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As one of the major water supply systems for inland rivers, especially in arid and semi-arid regions, snow cover strongly affects hydrological cycles. In this study, remote sensing datasets combined with in-situ observation data from a route survey of snow cover were used to investigate the changes in snow cover parameters on the Chinese Altai Mountains from 2000 to 2022, and the responses of snow cover to climate and hydrology were also discussed. The annual snow cover frequency (SCF), snow cover area, snow depth (SD), and snow density were 45.03%, 2.27 × 104 km2, 23.4 cm, and ~0.21 g·cm−3, respectively. The snow water equivalent ranged from 0.58 km3 to 1.49 km3, with an average of 1.12 km3. Higher and lower SCF were mainly distributed at high elevations and on both sides of the Irtysh river. The maximum and minimum snow cover parameters occurred in the Burqin River Basin and the Lhaster River Basin. In years with high SCF, abnormal westerly airflow was favorable for water vapor transport to the Chinese Altai Mountains, resulting in strong snowfall, and vice versa in years with low SCF. There were significant seasonal differences in the impact of temperature and precipitation on regional SCF changes. The snowmelt runoff ratios were 11.2%, 25.30%, 8.04%, 30.22%, and 11.56% in the Irtysh, Kayit, Haba, Kelan, and Burqin River Basins. Snow meltwater has made a significant contribution to the hydrology of the Chinese Altai Mountains. [ABSTRACT FROM AUTHOR]

The source region of the Yangtze River (SRYR, 1.4 × 105 km2 above Zhimenda station) on the Tibetan Plateau (TP) has 78% permafrost coverage. The streamflow depth increased at a rate of 2.5 mm/a since 2000. Quantification of the water contribution brought by permafrost thawing is a difficult task. In this study, we used Sentinel‐1 data and the SBAS‐InSAR technique to monitor terrain deformation from September 2016 to December 2021, and then utilized the long‐term deformation rate to assess ground ice meltwater release and the seasonal deformation to evaluate water storage in the active layer. Results reveal that 55.3% of the terrain in the SRYR has subsidence >2.5 mm/a, indicating widespread ground ice melting. The release rate of ground ice meltwater is 4.3 mm/a in the entire SRYR, above 6 mm/a at the Dangqu and Tuotuo River subbasins. The water release rate is relatively small (∼3%) in comparison to the streamflow depth of 151 mm per year during the investigation period of 2017–2021. We did not detect a strong increasing or decreasing trend among the 5‐year seasonal deformation, which reflects that the total soil water content in the active layer did not change significantly during the short investigation period. The results provide a data basis for ground ice richness and loss information in the SRYR and help to understand the impact of permafrost thawing on the regional water cycle in the permafrost environment. Plain Language Summary: The Yangtze River is the longest river in China; its source region (1.4 × 105 km2, above Zhimenda station) has 78% permafrost coverage and a 935 km3 ground ice reserve. The hydrological processes may have been significantly impacted by the permafrost degradation over the past few decades. This study presented a quantitative analysis of the effects of permafrost thawing on the water balance using terrain deformation derived from InSAR monitoring. Subsidence rates and seasonal deformation were first used combined to estimate permafrost thawing release water. The entire source region of the Yangtze River experienced extensive thaw subsidence and ground ice melting, and the rate of ground ice meltwater release was 4.3 mm per year during 2016–2021. The 5‐year seasonal deformation for 2017 to 2021 did not show strong increasing or decreasing trends. It suggests that the water storage in the active layer doesn't have significant changes. It may also suggest that most of the water from melting ground ice is released as surface or subsurface runoff and the supply to the active layer is small during the investigation period. Key Points: Quantitative analysis of the effects of permafrost thawing on the water balance in the permafrost‐affected watershedSubsidence rates and seasonal deformation were used combined to evaluate the amount of ground ice melting release waterRunoff depth of 4.3 mm/a by ground ice melting water and small variation of active layer water storage in the study area during 2016–2021 [ABSTRACT FROM AUTHOR]

Shrub encroachment has been a worldwide phenomenon, but the interactions between the surface hydrological cycle and the shrub‐encroached landscape at different hillslope positions remain poorly investigated. The present study was undertaken to explore the interactions between the water infiltration patterns affected by shrub encroachment. At four slope positions of a hillslope encroached by Caragana microphylla Lam, soil water content and temperature were continuously measured at 10‐min intervals at four or five depths in both the presence (shrub patches) and absence (grass matrix) of shrubs. Then, the infiltration of rainfall and meltwater was estimated based on analyses of the above data. The rainfall infiltration ratios (IRs) of grass matrix were as high as 0.78 ± 0.08, except at the lower site, which had a value of only 0.47. The IRs of shrub patches increased from 0.38 at the top site to 0.77 at the lower site. In snowy years, snow and ice were blown upward by wind and accumulated in the shrub patches and their leeward areas, which resulted in higher water input for the shrub patches than for the grass matrix. Shrub encroachment changed the microtopography and soil properties of the hillslope and further affected the surface hydrological processes. The feedbacks between shrub encroachment and water infiltration varied among sites of the hillslope, which may in turn have affected the development of shrub patches. [ABSTRACT FROM AUTHOR]

Lakes on the Tibetan Plateau (TP) play a major role in the regional hydrological cycle and underpin vital ecosystem services. However, the long-term lake evolution and underlying mechanisms, especially on the exorheic southern TP, remain unclear. Here, we reconstructed the lake level variations of Mabu Co and Gala Co on the southern TP through detailed paleo-shoreline dating using post-infrared infrared stimulated luminescence (pIRIR) signals of K-feldspar single grains, and explored the driving forcings based on a comparison of paleoclimate records and geomorphological analysis. The results show that a unified paleolake at Mabu Co and Gala Co at a level ∼20 m above the modern level (a.m.l.) of Mabu Co developed during the late MIS 3 (35.9 ± 1.9–29.1 ± 1.4 ka) in response to increased glacial meltwater and Indian summer monsoon (ISM) rainfall. Under intensive glacier melting, the paleolake reached its maximum level (∼29 m a.m.l.) and area (190 km2, ∼22 times larger than the modern areas of Mabu Co and Gala Co) during the last deglacial (16.8 ± 1.0–13.6 ± 0.7 ka) and began to outflow, which triggered incision and lowering of the spill-point. The lake level showed an overall decreasing trend since the last deglacial largely influenced by the lowering of the spill-point. During the last deglacial-early Holocene (12.7 ± 0.6–9.8 ± 0.6 ka), a high-stand lower than that in the previous stage (∼24 m a.m.l.) was maintained by the strengthened ISM and glacial meltwater. In the mid-Holocene (8.7 ± 0.9–4.1 ± 0.3 ka), the paleolake experienced two rapid lake level drops in response to the weakening events of the ISM. The exposed shoreline terrace between the two lakes following the lake level drop after ∼6 ka provided an ideal living surface for the inhabitants at the Mabu Co site during 4.5–4.0 ka. We found that glacial meltwater and lake spillover processes, apart from the ISM, have exerted great impacts on the hydrological history of Mabu Co and Gala Co. The paleolakes have provided critical resources for humans at the Mabu Co site living in the alpine anoxic environment. Additionally, we suggest that lakes with low spill-points adjacent to exorheic basins on the southern TP should be given more attention regarding flooding hazard risks against increasing precipitation and glacial meltwater in the future. • Paleo-shoreline dating using pIRIR of K-feldspar single grains. • A lake level record since MIS 3 on the southern Tibetan Plateau. • Lake high-stands in MIS 3 and the last deglacial influenced by meltwater. • Lake spillover and incision of spill-point occurred in the last deglacial. • Paleolake system provided living surface and resources for early humans. [ABSTRACT FROM AUTHOR]

Glaciers on the Tibetan Plateau play an important role in the local hydrological cycle. However, there are only few studies on groundwater in the alpine basins in the Tibetan Plateau which considered the effects of glaciers. Glaciers are extensively distributed in the Dongkemadi River Basin, which is a representative alpine basin in the Yangtze River source region. This study focuses on building a numerical groundwater flow model with glaciations using HydroGeoSphere (HGS) to simulate subglacial meltwater recharge to groundwater in the Dongkemadi River Basin in response to future climate changes. Effects of hydraulic conductivity, precipitation, and temperature on subglacial meltwater recharge to groundwater were discussed. Glacier changes in the future 50 years were predicted under different climate change scenarios. Results show that: (1) the average thickness of the glacier will change significantly; (2) the simulated rate of annual mean subglacial meltwater recharge to groundwater is 4.58 mm, which accounts for 6.33% of total groundwater recharge; and (3) hydraulic conductivity has the largest influence on subglacial meltwater recharge to groundwater, followed by temperature and precipitation. Results of this study are also important to sustainable water resource usage in the Yangtze River source region. Article Impact Statement: Investigate the subglacial meltwater recharge to groundwater in the Dongkemadi River Basin in response to future climate change. [ABSTRACT FROM AUTHOR]

Many subglacial environments consist of a fine‐grained, deformable sediment bed, known as till, hosting an active hydrological system that routes meltwater. Observations show that the till undergoes substantial shear deformation as a result of the motion of the overlying ice. The deformation of the till, coupled with the dynamics of the hydrological system, is further affected by the substantial strain rate variability in subglacial conditions resulting from spatial heterogeneity at the bed. However, it is not clear if the relatively low magnitudes of strain rates affect the bed structure or its hydrology. We study how laterally varying shear along the ice‐bed interface alters sediment porosity and affects the flux of meltwater through the pore spaces. We use a discrete element model consisting of a collection of spherical, elasto‐frictional grains with water‐saturated pore spaces to simulate the deformation of the granular bed. Our results show that a deforming granular layer exhibits substantial spatial variability in porosity in the pseudo‐static shear regime, where shear strain rates are relatively low. In particular, laterally varying shear at the shearing interface creates a narrow zone of elevated porosity which has increased susceptibility to plastic failure. Despite the changes in porosity, our analysis suggests that the pore pressure equilibrates near‐instantaneously relative to the deformation at critical state, inhibiting potential strain rate dependence of the deformation caused by bed hardening or weakening resulting from pore pressure changes. We relate shear variation to porosity evolution and drainage element formation in actively deforming subglacial tills. Plain Language Summary: The ice at the base of certain glaciers moves over soft sediments that route meltwater through the pore spaces in between the sediment grains. The ice shears the sediment, but it is not clear if this slow shearing is capable of changing the structure or volume of the pore space, or the path of the meltwater that flows through the sediment. To study the relations between the shearing of the sediment and the changes in its pore space, we use computer simulations that portray the sediment as a collection of closely packed spherical grains, where the pores are filled with meltwater. To shear the simulated sediment, the grains at the top are pushed with fixed speeds in the horizontal direction. Despite the slow shear, which is generally thought of as having no effect on pore space, our results show that shearing changes the sizes of the pores in between the grains, where large pores are formed near the top of the sediment layer. If the grains at the top are pushed with uneven speeds, then the largest pores are formed in the areas where grain speeds vary the most. We show that the exchange of meltwater between neighboring pores is faster than the movement of the grains, indicating that the meltwater can adjust quickly to changing pore space. Key Points: Large shear gradients at the ice‐till interface create a narrow zone of elevated porosity in tillThe porosity of granular beds increases with shear strain rate even for subglacial strain ratesPore pressure equilibrates rapidly at the grain scale during critical state shear [ABSTRACT FROM AUTHOR]

The Himalayas, also known as third pole of the Earth feed some of the major rivers of the world viz. Ganga, Indus, Brahmaputra etc. The accurate assessment of water resources in eastern Himalayas is very important for respective policy makers. The detailed assessment of water resources and hydrological cycle component are very critical for attaining United Nations sustainable development goals (SDGs) such as affordable and clean energy, clean water and sanitation and building resilient infrastructure This study focuses on Kameng river basin, estimating the melt water & its contribution to the total discharge of the river. A 3-layer VIC model coupled with energy balance algorithm is used to estimate the patterns of melt and discharge profile in the region. Net contribution of melt water to the river were estimated to be about 18% during peak melt season in upper catchments. With advancement in technology, acquiring meteorological data via remote sensing has become more accurate & of high resolution. This data is one of the major inputs of the model. With accurate forecasting of these parameters, multipurpose hydropower projects in these regions can plan well in advance thus playing a major role in Integrated Water Resource Management. In current study the coefficient of determination & Nash-Sutcliffe efficiency were calculated to be 0.82 & 0.71 respectively. With increasing population in the region, any substantial change in the streamflow will have consequences unknown as of now, thus making this study a necessity & need of hour. [ABSTRACT FROM AUTHOR]

Paleoproxy records indicate that abrupt changes in thermohaline circulation (THC) were induced by rapid meltwater discharge from retreating ice sheets. Such abrupt changes in the THC have been understood as a hysteresis behavior of a nonlinear system. Previous studies, however, primarily focused on a near-static hysteresis under fixed or slowly varying freshwater forcing (FWF), reflecting the equilibrated response of the THC. This study aims to improve the current understanding of transient THC responses under rapidly varying forcing and their dependency on forcing time scales. The results simulated by an Earth system model suggest that the bifurcation is delayed as the forcing time scale is shorter, causing the Atlantic meridional overturning circulation collapse and recovery to occur at higher and lower FWF values, respectively. The delayed shutdown/recovery occurs because bifurcation is determined not by the FWF value at the time but by the total amount of freshwater remaining over the THC convection region. The remaining freshwater amount is primarily determined by the forcing accumulation (i.e., time-integrated FWF), which is modulated by the freshwater/salt advection by ocean circulations and freshwater flux by the atmospheric hydrological cycle. In general, the latter is overwhelmed by the former. When the forced freshwater amount is the same, the modulation effect is stronger under slowly varying forcing because more time is provided for the feedback processes. [ABSTRACT FROM AUTHOR]

Due to the continuous degradation (gradual thawing) of permafrost, supra-permafrost water has become an important component of runoff that occurs in cold regions. However, current research has only focused on the amount of water provided by permafrost, and little has been reported regarding the source and formation mechanisms of supra-permafrost water. Due to the difficulty of observation and sampling in cold regions and insufficient data accumulation, model simulations face various difficulties in regard to solving problems related to hydrological processes. Considering the advantages of stable isotope tracer methods in hydrology, the source of supra-permafrost water in Qilian Mountain was analyzed based on 1,840 samples, and the source of supra-permafrost water was determined by end-member mixing analysis (EMMA). Negative line-conditioned excess (lc-excess), lower slope, and particularly the negative intercept of the evaporation line (EL) indicates strong evaporation effects on supra-permafrost water. Remarkably, the evolutionary process, influencing factors, and relationship with other water bodies all indicate that supra-permafrost water is replenished by precipitation, ground ice meltwater, and snow meltwater. The results indicated that from May to October, the contributions of precipitation to the supra-permafrost water were 79%, 83%, 90%, 84%, 87%, and 83%, respectively. Snow meltwater contributed 11%, 13%, 10%, 16%, 11%, and 9%, respectively. Permafrost degradation impacts the water cycle and can increase the minimum monthly runoff and increase groundwater storage. To mitigate the effects of this change, monitoring and early warning systems are essential for detecting signs of permafrost degradation in a timely manner so that appropriate measures can be taken. This may involve the use of remote-sensing technologies, sensor networks, and other methods for real-time monitoring. Establishing mechanisms for sharing information with the relevant departments is crucial. The research results provide scientific and technological support and aid in decision-making to mitigate the negative effects of continuous permafrost degradation in a changing environment. • Precipitation is the main source of supra-permafrost water in the Qilian Mountains. • Permafrost degradation increases the minimum monthly runoff and groundwater storage. • Main point #3: Stable isotope of supra-permafrost water has no obvious seasonal variation. [ABSTRACT FROM AUTHOR]

Above polar ice sheets, atmospheric water vapor exchange occurs across the planetary boundary layer (PBL) and is an important mechanism in a number of processes that affect the surface mass balance of the ice sheets. Yet, this exchange is not well understood, and has substantial implications for modeling and remote sensing of the polar hydrologic cycle. Efforts to characterize the exchange face substantial logistical challenges including the remoteness of ice sheet field camps, extreme weather conditions, low humidity and temperature that limits the effectiveness of instruments, and dangers associated with flying manned aircraft at low altitudes. Here, we present an Unmanned Aerial Vehicle (UAV) sampling platform for operation in extreme polar environments that is capable of sampling atmospheric water vapor for subsequent measurement of water isotopes. This system was deployed to the East Greenland Ice-core Project (EastGRIP) camp in northeast Greenland during summer 2019. Six sampling flight missions were completed. With a suite of atmospheric measurements onboard the UAV (temperature, humidity, pressure, GPS) we determine the height of the PBL using on-line algorithms, allowing for strategic decision making by the pilot to sample water isotopes above and below the PBL. Water isotope data was measured by a Picarro 2130-i instrument using flasks of atmospheric air collected within the nose cone of the UAV. The internal repeatability for δD and δ18O was 2.8 ‰ and 0.45 ‰, respectively, which we also compared to independent EastGRIP tower-isotope data. Based on these results, we demonstrate the efficacy of this new UAV-isotope platform and present improvements to be utilized in future polar field campaigns. The system is also designed to be readily adaptable to other fields of study, such as measurement of carbon cycle gases or remote sensing of ground conditions. [ABSTRACT FROM AUTHOR]

BACKGROUND: Hydrogen and oxygen isotopes can be used to identify water sources and trace water cycles and have been used in hydrogeochemistry since the 1950s. Studies have been carried out on stable isotopes of atmospheric precipitation, rivers and lakes in Xinjiang. However, the research on hydrogen and oxygen isotopes of waters in Altay is scarce, except for atmospheric precipitation. Researchers found that the rainfall in the Altai Mountains during the warm season (April-October) increased significantly from 1959 to 2014. Due to this background of climate condition changes, it is meaningful to study the hydrogen and oxygen isotope compositions of various types of water bodies in the Altay region, at the southern foot of the Altai Mountains. OBJECTIVES: To obtain the basic data of hydrogen and oxygen isotopic composition of water in Altay and reveal their spatial distribution characteristics. METHODS: Hydrogen and oxygen isotope compositions of river water, lake water, spring water, snow water, and water from a mine pit in the Altay region of Xinjiang were determined by liquid water laser isotope analyzer (LGR DTIOO, America). The dissolved oxygen (DO), TDS, T, and pH of the water samples were measured using the German WTW3430 multi - parameter water quality analyzer. The concentrations of Na+, K +, Ca2 +, and Mg2 + were analyzed by inductively coupled plasma - optical emission spectrometry (PE8300, PerkinElmer, USA) . The concentrations of HC03 and co; were determined by alkali titration method. Cl and SO~ concentrations were analyzed by ion chromatography method. RESULTS: The results showed that the ranges of 018 0 and oD of the waters in the Altay area were from -15. 4%o to - 5%o and from - 121 %0 to - 49%0, respectively. The hydrogen and oxygen isotope content of various types of water in the Altay region were significantly different. The 818 0 and oD values of river waters varied from - 15. 4%o to - 11. 5%o and from - 114%0 to - 100%0, respectively, and the deuterium excess parameter varied from - 12. 4%o to 12. 4%o. The 818 0 and oD of Ulungur Lake were much higher than those of surface rivers, with an average value of - 5. 95%0 and - 78. 5%o, respectively. The deuterium excess parameter of Ulungur Lake was much lower than those of surface rivers, with an average value of - 30. 9%o. The 8 18 0 value (- 14. 9%o and -11. 8%0) of groundwater was similar to that of surface rivers, but oD (- 114%0 and - 121%0) was slightly higher than that of surface rivers, indicating that groundwater was supplied by surface rivers but may be affected by water - rock reactions. The 818 0 and oD values of snow water and the water from a mine pit were - 11. 8%0 and - 90%0, - 11. 6%0 and - 106%0, respectively. The fitting lines for hydrogen and oxygen isotopes of the lrtysh River and Ulungur River were oD = 1. 7297 818 0 - 83. 879 and oD = 1. 986018 0 - 76. 5, respectively. Surface rivers were remarkably different from the global and Urumqi atmospheric precipitation lines, indicating that apart from atmospheric precipitation, surface rivers were also recharged by glacier meltwater, and underwent evaporation and isotope fractionation during the water cycle. Due to the temperature and latitude effect of hydrogen and oxygen isotopes, the oD and 318 0 showed significant positive correlation relationships with T, TDS, and the molar concentration of major ions such as Na+, K+, Ca2+, Cl, and SO~, also showing a significant negative correlation with the latitude of the sampling sites and DO (P < 0. 05, n = 32). CONCLUSIONS: The hydrogen and oxygen isotope composition characteristics obtained in this study provide basic data for the stable isotope research of various types of water bodies in the Altay area. The precipitation in Altay has increased significantly in recent decades. Due to this background, it is indeed necessary to continue to conduct long - term and in - depth systematic research on the composition of hydrogen and oxygen isotopes in Altay's atmospheric precipitation and other types of water bodies. [ABSTRACT FROM AUTHOR]

Water levels in streams and aquifers often exhibit daily cycles during rainless periods, reflecting daytime extraction of shallow groundwater by evapotranspiration (ET) and, during snowmelt, daytime additions of meltwater. These cycles can aid in understanding the mechanisms that couple solar forcing of ET and snowmelt to changes in streamflow. Here we analyze 3 years of 30 min solar flux, sap flow, stream stage, and groundwater level measurements at Sagehen Creek and Independence Creek, two snow-dominated headwater catchments in California's Sierra Nevada mountains. Despite their sharply contrasting geological settings (most of the Independence basin is glacially scoured granodiorite, whereas Sagehen is underlain by hundreds of meters of volcanic and volcaniclastic deposits that host an extensive groundwater aquifer), both streams respond similarly to snowmelt and ET forcing. During snow-free summer periods, daily cycles in solar flux are tightly correlated with variations in sap flow, and with the rates of water level rise and fall in streams and riparian aquifers. During these periods, stream stages and riparian groundwater levels decline during the day and rebound at night. These cycles are reversed during snowmelt, with stream stages and riparian groundwater levels rising during the day in response to snowmelt inputs and falling at night as the riparian aquifer drains. Streamflow and groundwater maxima and minima (during snowmelt- and ET-dominated periods, respectively) lag the midday peak in solar flux by several hours. A simple conceptual model explains this lag: streamflows depend on riparian aquifer water levels, which integrate snowmelt inputs and ET losses over time, and thus will be phase-shifted relative to the peaks in snowmelt and evapotranspiration rates. Thus, although the lag between solar forcing and water level cycles is often interpreted as a travel-time lag, our analysis shows that it is mostly a dynamical phase lag, at least in small catchments. Furthermore, although daily cycles in streamflow have often been used to estimate ET fluxes, our simple conceptual model demonstrates that this is infeasible unless the response time of the riparian aquifer can be determined. As the snowmelt season progresses, snowmelt forcing of groundwater and streamflow weakens and evapotranspiration forcing strengthens. The relative dominance of snowmelt vs. ET can be quantified by the diel cycle index, which measures the correlation between the solar flux and the rate of rise or fall in streamflow or groundwater. When the snowpack melts out at an individual location, the local groundwater shifts abruptly from snowmelt-dominated cycles to ET-dominated cycles. Melt-out and the corresponding shift in the diel cycle index occur earlier at lower altitudes and on south-facing slopes, and streamflow integrates these transitions over the drainage network. Thus the diel cycle index in streamflow shifts gradually, beginning when the snowpack melts out near the gauging station and ending, months later, when the snowpack melts out at the top of the basin and the entire drainage network becomes dominated by ET cycles. During this long transition, snowmelt signals generated in the upper basin are gradually overprinted by ET signals generated lower down in the basin. The gradual springtime transition in the diel cycle index is mirrored in sequences of Landsat images showing the springtime retreat of the snowpack to higher elevations and the corresponding advance of photosynthetic activity across the basin. Trends in the catchment-averaged MODIS enhanced vegetation index (EVI2) also correlate closely with the late springtime shift from snowmelt to ET cycles and with the autumn shift back toward snowmelt cycles. Seasonal changes in streamflow cycles therefore reflect catchment-scale shifts in snowpack and vegetation activity that can be seen from Earth orbit. The data and analyses presented here illustrate how streams can act as mirrors of the landscape, integrating physical and ecohydrological signals across their contributing drainage networks. [ABSTRACT FROM AUTHOR]

Some 180 million people depend on the Indus River as a key water resource, fed largely by precipitation falling over the western Himalaya. However, the projected response of western Himalayan precipitation to climate change is currently not well constrained: CMIP5 GCMs project a reduced frequency and vorticity of synoptic-scale systems impacting the area, but such systems would exist in a considerably moister atmosphere. In this study, a convection-permitting (4 km horizontal resolution) setup of the Weather Research and Forecasting (WRF) model is used to examine 40 cases of these synoptic-scale systems, known as western disturbances (WDs), as they interact with the western Himalaya. In addition to a present-day control run, three experiments are performed by perturbing the boundary and initial conditions to reflect pre-industrial, RCP4.5 and RCP8.5 background climates respectively. It is found that in spite of the weakening intensity of WDs, net precipitation associated with them in future climate scenarios increases significantly; conversely there is no net change in precipitation between the pre-industrial and control experiments despite a significant conversion of snowfall in the pre-industrial experiment to rainfall in the control experiment, consistent with the changes seen in historical observations. This shift from snowfall to rainfall has profound consequences on water resource management in the Indus Valley, where irrigation is dependent on spring meltwater. Flux decomposition shows that the increase in future precipitation follows directly from the projected moistening of the tropical atmosphere (which increases the moisture flux incident on the western Himalaya by 28%) overpowering the weakened dynamics (which decreases it by 20%). Changes to extreme rainfall events are also examined: it is found that such events may increase significantly in frequency in both future scenarios examined. Two-hour maxima rainfall events that currently occur in 1-in-8 WDs are projected to increase tenfold in frequency in the RCP8.5 scenario; more prolonged (1-week maxima) events are projected to increase fiftyfold. [ABSTRACT FROM AUTHOR]

Rivers play a key role in the water cycle on the earth via integrating all hydrological channels to return terrestrial precipitations back to the oceans. In addition, rivers, together with groundwater, are powerful transformers of the surface lithosphere, responsible for chemical weathering of rocks and the removal of solute into the ocean. Tracing the dynamics of surface water and groundwater versus atmospheric feeding of rivers presents important issues in Arctic regions due to the ongoing change of the structure of hydrological runoff. In this study, stable water isotopes were used to reveal the temporal dynamics of water sources and to predict their possible change under the conditions of ongoing climate warming of the largest European Arctic river, the Severnaya Dvina, and adjacent groundwater. The isotopic composition of the river waters of the studied region is formed by the mixing of atmospheric precipitation with groundwater. The isotopic depletion in the springtime is mainly due to the recharge of thawed snow waters. A less pronounced effect in the autumn-winter period is provided by the discharge of groundwater into rivers, including the meltwater of the Last Glacial Period. This depletion is partially offset due to discharge of isotopically light thawed snow waters and is linked to evaporation in headwater streams, reservoirs, and wetlands. The isotopic composition of groundwater with low mineralization was formed throughout the Holocene and to a large extent depends on paleoclimatic conditions in the study area. In addition to fresh groundwater, brackish groundwater also takes part in the river's recharge. These brackish waters are associated with ancient and modern marine transgressions on the estuarine site and with the dissolution of Ca sulfate rocks in a karst region located in the middle reaches of the river. According to isotope data, the average annual input of the underground source to the total river flow is 25%. The results of this work will serve as the basis for continuing monitoring of the isotopic composition of river waters with an assessment of hydrological processes and observation of short as well as long-term climatic and anthropogenic impacts. [ABSTRACT FROM AUTHOR]

This study discusses the hydrochemical components of glacier snow meltwater using the correlation analysis, factor analysis, enrichment factor, and the Gibbs diagram. Water samples were collected from June to September in 2016 and 2017. The results obtained the monthly changes for anions and cations in Yuzhufeng (YZG) and Jianggudiru Glacier (JGG) were notably, with highest concentration of ions recorded in September. The effect of seasonal variation on the chemical characteristics of glacier snow meltwater was determined by studying the interaction between the glacier snow meltwater and the control source. The change of hydrochemical characteristics and hydrological cycle is positive in cold areas under the climate warming. The hydrochemical characteristics of glacier snow meltwater in study area were mainly contributed by crustal sources such as evaporates and carbonate rocks. Certainly, a small part of human input cannot be ignored. There was a close relationship between temperature and hydrochemical characteristics, and the relationship between meteorological factors and other ions except K+ was not clear. It is concluded that the water chemistry of glacier snow meltwater in the Alpine region is mainly controlled by the temperature factor-led ablation. [ABSTRACT FROM AUTHOR]

The seasonal snowmelt period is a critical component of the hydrologic cycle for many mountainous areas. Changes in the timing and rate of snowmelt as a result of physical hydrologic flow paths, such as longitudinal intra‐snowpack flow paths, can have strong implications on the partitioning of meltwater amongst streamflow, groundwater recharge, and soil moisture storage. However, intra‐snowpack flow paths are highly spatially and temporally variable and thus difficult to observe. This study utilizes new methods to non‐destructively observe spatio‐temporal changes in the liquid water content of snow in combination with plot experiments to address the research question: What is the scale of influence that intra‐snowpack flow paths have on the downslope movement of liquid water during snowmelt across an elevational gradient? This research took place in northern Colorado with study plots spanning from the rain‐snow transition zone up to the high alpine. Results indicate an increasing scale of influence from intra‐snowpack flow paths with elevation, showing higher hillslope connectivity producing larger intra‐snowpack contributing areas for meltwater accumulation, quantified as the upslope contributing area required to produce observed changes in liquid water content from melt rate estimates. The total effective intra‐snowpack contributing area of accumulating liquid water was found to be 17, 6, and 0 m2 for the above tree line, near tree line, and below tree line plots, respectively. Dye tracer experiments show capillary and permeability barriers result in increased number and thickness of intra‐snowpack flow paths at higher elevations. We additionally utilized aerial photogrammetry in combination with ground penetrating radar surveys to investigate the role of this hydrologic process at the small watershed scale. Results here indicate that intra‐snowpack flow paths have influence beyond the plot scale, impacting the storage and transmission of liquid water within the snowpack at the small watershed scale. [ABSTRACT FROM AUTHOR]

Global policies for mitigation of global warming GW will require countries to rely as possible upon renewable, clean energy sources. This includes developing countries, in need to foster suitable life conditions under population growth. Hydropower can deliver such renewable energy, pending water availability and proper management. In central Asia, water resources management is an urgent challenge, especially given desert climate, and the expected impacts of transient climate change hereon. While some catchments will still receive large shares of water from transient melting of the water towers in the Himalayas, others will not, given their little ice cover, in spite of the high altitudes. This is the case of Kabul River of Afghanistan, displaying low rainfall and high altitude, and yet displaying very small ice cover, and where further the present hydropower network is limited and partly damaged by recent conflicts. The goal of this work is to evaluate hydropower potential of the Kabul River and subsequently potential hydropower coverage of energy demand, under the hypotheses that (i) the present network would work at its largest potential and (ii) that hydrological regimes will change in response to scenarios of climate change, until the end of XXI century. To do so, we use a sparse array of data to tune the Poli-Hydro model, able to model hydrology of high altitude, poorly monitored catchments as here. Using modelled (and otherwise unknown) streamflows entering the present power plants (reservoirs + power-houses), we then simulate water management for hydropower purposes. We use two conditions, namely (i) run-of-river ROR and (ii) storage, and (optimal) regulation STO, allowing multipurpose use of water when necessary (e.g. irrigation needs). We then feed Poli-Hydro with IPCC climate scenarios (plus downscaling) until 2100, to carry out a sensitivity analysis (what if? scenarios) of (i) hydrological cycle and (ii) hydropower production. The future hydrological regimes are largely affected by uncertain future precipitation, and so is hydropower production. In spite of potentially increased hydropower on average (+ 1.4% at mid-century, + 1.7% at 2100), driven by variably changing stream flows, some scenarios indicate decreased overall production (down to − 3%) at half century. We provided here a tool usable to (i) assess present and future hydropower potential in the Kabul River, (ii) direct improvement of the present plants network and (iii) benchmark proposals for future network extension. [ABSTRACT FROM AUTHOR]

• Isotopic evolution from heterogeneous snowpack captured in the model. • Increasing isotopic difference of initial snow layers induces more variation. • Isotopically enriched top layer induces more alteration in the residual snowpack. • Optimized parameters for melting of heterogeneous snowpack were suggested. Snowmelt, a component of the hydrological cycle, is influenced by changing climate and meteorological events. In the context of hydrometeorological studies, the water isotopic composition of snowmelt has been commonly used. This study examined temporal variations in the isotopic composition of snowmelt from an isotopically heterogeneous snowpack to the context of accurate quantification of isotope-based hydrograph separation. In this study, a one-dimensional model was used to simulate the isotopic variations of the meltwater by varying the initial isotopic compositions of the snow layers and parameters such as effectiveness of exchange (ψ), ice-to-liquid ratio of the exchange system (f), and water saturation (S). Isotopic evolution is sensitive to the initial layer sequence of isotopically enriched or depleted snow in the snowpack and the extent of isotopic differences between the layers. More variated patterns are observed in the isotopic evolution as the ψ and f values are increased; particularly, a significant modification is observed in the bottom layer that is altered by the enriched top layer, thereby further affecting the pattern of isotopic evolution. The isotopic heterogeneity has been suggested to be a significant factor in the isotopic evolution of snowmelt, even though various other influencing factors have been considered under natural conditions. Because of the close dependence of snow and glacial conditions upon climate change, this study is expected to support further hydrometeorological studies, particularly in snow-dominated regions. [ABSTRACT FROM AUTHOR]

The state of the subglacial hydrologic system, which can modify ice motion, is sensitive to the volume and rate of meltwater reaching it. Bare‐ice regions rapidly transport meltwater to the bed via moulins, while in certain accumulation zone regions, meltwater first flows through firn aquifers, which can introduce a substantial delay. We use a subglacial hydrological model forced with idealized meltwater input scenarios to test the effect of this delay on subglacial hydrology. We find that addition of firn‐aquifer water to the subglacial system elevates the inland subglacial water pressure while reducing water pressure and enhancing subglacial channelization near the terminus. This effect dampens seasonal variations in subglacial water pressure and may explain regionally anomalous ice velocity patterns observed in Southeast Greenland. As surface melt rates increase and firn aquifers expand inland, it is crucial to understand how inland drainage of meltwater affects the evolution of the subglacial hydrologic system. Plain Language Summary: The flow of ice and meltwater from the Greenland Ice Sheet into the ocean affects sea levels. Ice flow is sensitive to meltwater that travels underneath the glacier. Where and when that water reaches the glacier bed shapes the water channel network under the glacier. We use a computer model to analyze how firn aquifers, newly discovered meltwater pockets that sit dozens of meters below the ice sheet surface in east Greenland, change the water channel network under local glaciers. We find that the firn‐aquifer water supply can maintain a water channel network under the glacier that changes less over each season, compared to areas without firn‐aquifer water. This subglacial channelization could explain observations of steadier glacier flow in locations with firn aquifers. Key Points: High‐elevation firn‐aquifer water drainage drives evolution of the subglacial hydrologic system >30 km inland, potentially affecting outlet glacier speedPersistent input of water from firn aquifers can maintain subglacial channels outside the melt season and across yearsThe timing and duration of firn‐aquifer water delivery to the bed is an important but underconstrained variable in ice sheet hydrology [ABSTRACT FROM AUTHOR]

Glacier meltwater change in the north‐eastern edge of the Tibetan Plateau is greatly important for the projection of the impact of future climate change on local water resource management. Although the glaciated area is only approximately 4% of the Upper Reach of the Shule River Basin (URSRB), the average glacier meltwater contribution to river run‐off was approximately 23.6% during the periods 1971/1972 to 2012/2013. A new glacier melting module coupled with the macroscale hydrologic Variable Infiltration Capacity model (VIC‐CAS) was adopted to simulate and project changes in the glacier meltwater and river run‐off of the URSRB forced by downscaled output of the BCC‐CSM1.1(m), CANESM2, GFDL‐CM3, and IPSL‐CM5A‐MR models. Comparisons between the observed and simulated river run‐offs and glacier area changes during the periods 2000/2001, 2004/2006, 2008/2009, and 2012/2013 suggest that the simulation is reasonable. Due to increases in precipitation, the annual total run‐off is projected to increase by approximately 2.58–2.73 × 108 m3 in the 2050s and 0.28–1.87 × 108 m3 in the 2100s compared with run‐off in the 2010s based on the RCP2.6 (low greenhouse gas emission) and RCP4.5 (moderate greenhouse gas emission) scenarios, respectively. The contribution of glacier meltwater to river run‐off will more likely decrease to approximately 10% and less than 5% during the 2050s and 2100s, respectively. [ABSTRACT FROM AUTHOR]

Globally glaciers are rapidly shrinking, endangering the sustainability of melt water and altering the regional hydrology. Understanding long-term glacier response to climate change and the influence of non-climatic attributes like morpho-topographic factors on ice loss is of high relevance. Here we estimate the multi-temporal mass balance of 445 glaciers in the upper Alaknanda basin and neighboring transboundary glaciers using optical stereo imageries from 1973 to 2021. Our measurements indicate a mean annual area change rate of −1.14 ± 0.07 km2 a−1 and a geodetic glacier mass balance of −0.34 ± 0.08 m w.e. a−1 from 1973 to 2020, leading to an overall mass loss of 12.9 ± 1.7 Gt, that accounts for up to 0.036 ± 0.006 mm of sea level rise. Before 2000 (1973–2000), the mean regional glacier mass loss rate was −0.30 ± 0.07 m w.e. a−1, which increased to −0.43 ± 0.06 m w.e. a−1 during 2000–2020. ERA5 Land reanalysis data showed a summer and annual temperature rise of ∼0.6 °C and ∼ 0.5 °C respectively in recent time period (2015–2020) and consequent strong mass loss (−0.68 ± 0.09 m w.e. a−1). In addition to climatic influence, glacier morphometry, topographic features and uneven debris cover distribution further impacted the regional and glacier specific mass balance. Our multi-temporal observation from space also emphasized that though the glaciers in this region experienced an increasing mass loss but a strong heterogeneous glacier specific response, like surging and dynamic separation of glacier, are also evident that was not captured by the available long-term global elevation change grids. Among all the climatic and non-climatic attributes, we identified summer temperature having most significant influence over glacier mass budget in this region, with a mass balance sensitivity of −0.6 m w. e. a−1 °C−1. Hence, knowing the mean summer temperature will help to predict the mass balance for any intermediate year for this region. If such climatic trend continues, smaller glaciers are likely to disapear in coming decades. Similar studies in other parts of the world and on specific glaciers can reveal links with climate factors, reconstruct mass balance, and enhance comprehension of glacier response to climate change. Our geodetic mass balance estimates will improve the estimation of meltwater run-off component of the hydrological cycle in this part of the Himalaya, which could be used to calibrate/validate glacier mass balance models. • Detailed analysis of multi-temporal (ten periods) geodetic mass budget for ∼445 glaciers in the Alaknanda Basin and surroundings. • Overall (1973-2020) mass loss was −0.34 ± 0.08 m w.e. a –1 (12.9 ± 1.7 Gt), that accounts for up to 0.036 ± 0.006 mm of sea level rise. • Increase in summer and annual temperature in the most recent period (2015-2020) led to strongest mass loss (-0.68 ± 0.09 m w.e.a -1) over all periods. • Short-term heterogeneous variations like glacier surging and dynamic separation are also identified. • Among all climatic and non-climatic factors, summer temperature has strongest influence, with a mass balance sensitivity of -0.6 m w. e. a -1 ° C -1. [ABSTRACT FROM AUTHOR]

The marine-terminating outlet in Basin 3, Austfonna ice cap, has been accelerating since the mid-1990s. Stepwise multi-annual acceleration associated with seasonal summer speed-up events was observed before the outlet entered the basin-wide surge in autumn 2012. We used multiple numerical models to explore hydrologic activation mechanisms for the surge behaviour. A continuum ice dynamic model was used to invert basal friction coefficient distributions using the control method and observed surface velocity data between April 2012 and July 2014. This has provided input to a discrete element model capable of simulating individual crevasses, with the aim of finding locations where meltwater entered the glacier during the summer and reached the bed. The possible flow paths of surface meltwater reaching the glacier bed as well as those of meltwater produced at the bed were calculated according to the gradient of the hydraulic potential. The inverted friction coefficients show the "unplugging" of the stagnant ice front and expansion of low-friction regions before the surge reached its peak velocity in January 2013. Crevasse distribution reflects the basal friction pattern to a high degree. The meltwater reaches the bed through the crevasses located above the margins of the subglacial valley and the basal melt that is generated mainly by frictional heating flows either to the fast-flowing units or potentially accumulates in an overdeepened region. Based on these results, the mechanisms facilitated by basal meltwater production, crevasse opening and the routing of meltwater to the bed are discussed for the surge in Basin 3. [ABSTRACT FROM AUTHOR]

The residence time of subglacial meltwater impacts aquifer recharge, nutrient production, and chemical signals that reflect underlying bedrock/substrate, but is inaccessible to direct observation. Here we report the seasonal evolution of subglacial meltwater chemistry from the 2011 melt season at the terminus of the Athabasca Glacier, Canada. We measured major and trace analytes and U-series isotopes for twenty-nine bulk meltwater samples collected over the duration of the melt season. This dataset, which is the longest time-series record of ( 234 U/ 238 U) isotopes in a glacial meltwater system, provides insight into the hydrologic evolution of the subglacial system during active melting. Meltwater samples, measured from the outflow, were analyzed for ( 238 U), ( 222 Rn) and ( 234 U/ 238 U) activity , conductivity, alkalinity, pH and major cations. Subglacial meltwater varied in [ 238 U] and ( 222 Rn) from 23 to 832 ppt and 9 to 171 pCi/L, respectively. Activity ratios of ( 234 U/ 238 U) ranged from 1.003 to 1.040, with the highest ( 238 U), ( 222 Rn) and ( 234 U/ 238 U) activity values occurring in early May when delayed-flow basal meltwater composed a significant portion of the bulk melt. From the chemical evolution of the meltwater, we posit that the relative subglacial water residence times decrease over the course of the melt season. This decrease in qualitative residence time during active melt is consistent with prior field studies and model-predicted channel switching from a delayed, distributed network to a fast, channelized network flow. As such, our study provides support for linking U-series isotopes to storage lengths of meltwater beneath glacial systems as subglacial hydrologic networks evolve with increased melting and channel network efficiency. [ABSTRACT FROM AUTHOR]

Melt runoff (MR) contributes significantly to the total runoff in many river basins. Knowledge of the meltwater contribution (MCR, defined as the ratio of MR to the total runoff) to the total runoff benefits water resource management and flood control. A process-based land surface model, Noah-MP, was used to investigate the spatiotemporal characteristics of MR and MCR in the Upper Changjiang River (as known as Yangtze River) Basin (UCRB) located in southwestern China. The model was first calibrated and validated using snow cover fraction (SCF), runoff, and evapotranspiration (ET) data. The calibrated model was then used to perform two numerical experiments from 1981 to 2010: control experiment that considers MR and an alternative experiment that MR is removed. The difference between two experiments was used to quantify MR and MCR. The results show that in the entire UCRB, MCR was approximately 2.0% during the study period; however, MCR exhibited notable spatiotemporal variability. Four sub-regions over the Qinghai-Tibet Plateau (QTP) showed significant annual MCR ranging from 3.9% to 6.0%, while two sub-regions in the low plain regions showed negligible annual MCR. The spatial distribution of MCR was generally consistent with the distribution of glaciers and elevation distribution. Mann-Kendall (M-K) tests of the long-term annual MCR indicated that the four sub-regions in QTP exhibited increasing trends ranging from 0.01%/year to 0.21%/year during the study period but only one displayed statistically significant trend. No trends were found for the peak time (PT) of MR and MCR, in contrast, advancing trend were observed for the center time (CT) of MR, ranging from 0.01 months/year to 0.02 months/year. These trends are related to the changes of air temperature and precipitation in the study area. [ABSTRACT FROM AUTHOR]

[Display omitted] • Spatio-temporal variability of stream flow was observed using stable water isotopes. • Seasonal variation in δ18O and δ2H reflects different contributing sources. • Heterogeneity is spatial δ18O and δ2H patterns is ascribed to distinct microclimatic conditions. • D-Excess values of stream water reflects mixing of precipitation sources. • Mean Residence Time (MRT) estimated in stream water is 188 ± 15–387 ± 38 days. The meltwater generated from the Himalayan mountain system is an important source of freshwater sustaining hydrological, ecological and biological activities in upstream and downstream regions. Under a warming climate, the cryospheric cover is shrinking, altering the availability of freshwater to ∼53 million people living in the upper and lower parts of the Himalayas. Therefore, it becomes essential to understand the hydrological processes and regimes influencing the regional hydrological cycle for proper water resource management and ecosystem restoration policies. In this study, we measured the patterns of isotopic values (δ18O and δ2H) of river/streamwater to assess the factors controlling its spatio-temporal variability and mean residence time in glacierized mountainous Upper Indus River Basin, India to better understand the significant hydrological processes and controls. The isotopic values of stream/river water exhibited significant spatio-temporal variance ascribed to changing physiographic, hydrometeorological, and climatic factors persisting at the local and regional scales. The slope and intercept of the River Water Line [δ2H = (8.3 ± 0.2) × δ18O + (15 ± 3.9, p > 0.001)] is higher than global meteoric water line and local meteoric water line of the UIRB, India. The seasonality in source water ratios suggested that stream water is more biased to winter precipitation. The estimated mean residence time in six sub-basins ranged from 188 ± 17 to 387 ± 38 days with the longest and shortest mean residence time observed in Indus (387 ± 38 days) and Tangtse (188 ± 17 days) sub-basins. The polynomial (second‐order) relationship suggests that the variability in the paleo-precipitation δ18O values reflect a change in the moisture source and/or upliftment along airmass transport pathways. Our study highlighted the significance of physiographical and hydrometeorological processes in controlling the spatio-temporal variance of stable isotopic composition of river/stream water bodies. The current research work also improved the knowledge and understanding of the local and regional hydrological processes. [ABSTRACT FROM AUTHOR]

Glacier-melt-induced changes in runoff are of concern in northwestern China where glacier runoff is a major source for irrigation, industries and ecosystems. Samples were collected in different water mediums such as precipitation, glacial ice/snowcover, meltwater, groundwater and streamwater for the analysis of stable isotopes and solute contents during the 2009 runoff season in the Laohugou Glacial Catchment. The multi-compare results of δ18O values showed that significant difference existed in different water mediums. Source waters of streamflow were determined using data of isotopic and geochemical tracers and a three-component hydrograph separation model. The results indicated that meltwater dominated (69.9 ± 2.7%) streamflow at the catchment. Precipitation and groundwater contributed 17.3 ± 2.3% and 12.8 ± 2.4% of the total discharge, respectively. According to the monthly hydrograph, the contribution of snow and glacier meltwater varied from 57.4% (September) to 79.1% (May), and that of precipitation varied from 0% (May) to 34.6% (September). At the same time, the monthly contribution of groundwater kept relatively steady, varying from 9.7% (June) to 20.9% (May) in the runoff season. Uncertainties for this separation were mainly caused by the variation of tracer concentrations. It is suggested that the end-member mixing analysis (EMMA) method can be used in the runoff separation in an alpine glacial catchment.Editor Z.W. Kundzewicz; Associate editor Not assigned [ABSTRACT FROM PUBLISHER]

The hydrological cycle has been enhanced under the warmer climatic conditions on the southeastern edge of the Tibetan Plateau, China. To investigate the complex hydrological system in the study area, δ18O and δ²H were measured on waters in a mountainous region-Huangbengliu watershed. The stream water tends to be isotopically more depleted in 18O and ²H than precipitation and groundwater, but more enriched than meltwater. A clear seasonality with higher isotopic values of stream water in summer and lower values in winter is evident, coinciding with the timing of the peak discharge. The correlation between δ18O and δ²H in stream water shows that the isotopic signature of precipitation is well preserved in stream flow, and the evaporation during the stream flow is only minor. The isotopic composition of stream water shows a decreasing trend from upstream to downstream, which results from tributary water inputs with heavy-isotope-depleted water. According to an isotopic mass-balance model, the fraction of meltwater inputs over the total stream flow ranged from 25.5 to 61.8 %. The study demonstrates that the ice--snow melting and tributary inputs are the prevailing mechanisms regulating stream isotope hydrology in alpine regions on the edge of the Tibetan Plateau. [ABSTRACT FROM AUTHOR]

• The isotopic composition of stream water is controlled by the different sources. • The lapse rate of δ18O was −0.19 ‰/100 m across the YZR Basin. • Potential sources of YZR were identified and quantified. Investigations of the hydrological processes of the Yarlung Zangbo River (YZR), a sizeable highland river on the southern margin of the Tibetan Plateau (TP), face challenging constraints owing to the complexities in the water sources and cycle pathway. A total of 156 stream water samples from the YZR Basin were collected and analyzed to elucidate our understanding of regional hydroclimate. The isotopic values were more negative in the uppermost reaches of the YZR and progressively increased along the river, with mean δ18O and δD values at − 15.16 ‰ and − 111.58 ‰, respectively. A clear negative gradient of − 0.19 ‰/100 m was obtained from the datasets, which is consistent with that of the southeastern TP. The linear regression for all samples was δ D = 8.64 × δ 18O + 19.80 (R2 = 0.93, n = 192), and the slope and intercept were highly similar to those of the meteoric water line in the TP, suggesting that precipitation plays a dominant role in stream recharge sources. Combining the results from the air mass trajectory model and the d-excess values, we found that moisture in the YZR originates mainly from the Bay of Bengal, with westerly mixing in the upper reaches. In addition to precipitation, glacial meltwater and geothermal waters were considered significant water sources for the YZR based on geographic and geological conditions. The proportion of glacial meltwater in the uppermost reaches was calculated to range from 68.2 % to 70.4 % using the end-member mixing analysis method. The contribution ratios of precipitation, glacial meltwater, and geothermal water were almost equal in the middle of the basin, while glacial meltwater contribution dominated in the downstream regions. These findings will significantly impact understanding of the hydrological cycle in the study area and provide vital baseline knowledge about the contribution proportion of different recharge sources in the YZR basin. [ABSTRACT FROM AUTHOR]

By using a degree-day based distributed hydrological model, regimes of glacial runoff from the Koxkar glacier during 2007-2011 are simulated, and variations and characteristics of major hydrological components are discussed. The results show that the meltwater runoff contributes 67.4%, of the proglacial discharge, out of which snowmelt, clean ice melting, buried-ice ablation and ice-cliff backwasting account for 22.4%, 21.9%, 17.9% and 5.3% of the total melt runoff, respectively. Rainfall runoff is significant in mid-latitude glacierized mountain areas like Tianshan and Karakorum. In the Koxkar glacier catchment, about 11.5% of stream water is initiated from liquid precipitation. Spatial distributions for each glacial runoff component reveal the importance of climatic gradients, local topography and morphology on glacial runoff generation, and temporal variations of these components is closely related to the annual cycle of catchment meteorology and glacier storage. Four stages are recognized in the seasonal variations of glacier storage, reflecting changes in meltwater yields, meteorological conditions and drainage systems in the annual hydrological cycle. [ABSTRACT FROM AUTHOR]

Continental ice sheets are a key component of the Earth's climate system, but their internal dynamics need to be further studied. Since the last deglaciation, the northern Eurasian Fennoscandian Ice Sheet (FIS) has been connected to the Black Sea (BS) watershed, making this basin a suitable location to investigate former ice-sheet dynamics. Here, from a core retrieved in the BS, we combine the use of neodymium isotopes, high-resolution elemental analysis, and biomarkers to trace changes in sediment provenance and river runoff. We reveal cyclic releases of meltwater originating from Lake Disna, a proglacial lake linked to the FIS during Heinrich Stadial 1. Regional interactions within the climate-lake-FIS system, linked to changes in the availability of subglacial water, led to abrupt drainage cycles of the FIS into the BS watershed. This phenomenon raised the BS water level by ~100 m until the sill of the Bosphorus Strait was reached, flooding the vast northwestern BS shelf and deeply affecting the hydrology and circulation of the BS and, probably, of the Marmara and Aegean Seas. [ABSTRACT FROM AUTHOR]

This study used 46 years of recent data, including glacial area, temperature, precipitation, and runoff data, to examine the glacier melting and its possible socioeconomic effects in the Manas River basin in western China. The average yearly change in the glaciated area in the Manas River basin for the entire study period was 0.41 %, and the glacier mass balance mainly keeps negative in the last 46 years. The negative glacial mass balance observed between 1986 and 2006 was 2.8 times greater than that for the period 1960-1985. Additionally, the amount of meltwater runoff was 78 % greater in 1986-2006 than in 1960-1985, with a mean depth of 478 mm year.Glacier melting and runoff in the Manas River basin during the late twentieth century were higher than at present. Annual meltwater volumes can reach 1 × 10 m, providing beneficial water resources to downstream areas. However, as the climate becomes warmer, the risk of meltwater flooding will also increase. Our calculations indicate that after the 2030s, the level of flooding risk will increase substantially. [ABSTRACT FROM AUTHOR]

Alpine glaciers have receded substantially over the last century in many regions of the world. Resulting changes in glacial runoff not only affect the hydrological cycle, but can also alter the physical (i.e., turbidity from glacial flour) and biogeochemical properties of downstream ecosystems. Here we compare nutrient concentrations, transparency gradients, algal biomass, and fossil diatom species richness in two sets of high-elevation lakes: those fed by snowpack melt alone (SF lakes) and those fed by both glacial and snowpack meltwaters (GSF lakes). We found that nitrate (NO3-) concentrations in the GSF lakes were 1-2 orders of magnitude higher than in SF lakes. Although nitrogen (N) limitation is common in alpine lakes, algal biomass was lower in highly N-enriched GSF lakes than in the N-poor SF lakes. Contrary to expectations, GSF lakes were more transparent than SF lakes to ultraviolet and equally transparent to photosynthetically active radiation. Sediment diatom assemblages had lower taxonomic richness in the GSF lakes, a feature that has persisted over the last century. Our results demonstrate that the presence of glaciers on alpine watersheds more strongly influences NO3-concentrations in high-elevation lake ecosystems than any other geomorphic or biogeographic characteristic. [ABSTRACT FROM AUTHOR]

The article focuses on the simplification of heat balance calculation to simulate discharge fluctuations from the July 1st Glacier in China since 1930s. It notes the estimation of the relative humidity and downward solar radiation from precipitation. It mentions that the computation of the daily discharge for the 2002 melting had produced a better simulation than those using the positive degree-day method. It states the calculation of the glacier runoff and mass balance at the July 1st Glacier since 1935. It also mentions the utilization of three patterns of daily temperature and precipitation to estimate meteorological data.

• River discharge and precipitation had inconsistent trends in this study area. • Considering snow melt parameters could improve river discharge simulation using SWAT. • Grid-based data could have better performance of simulation than station data. • Future river discharge would vary significantly with different changing rates. River discharge is one of the key elements in the global water cycle; however, its observation and projection are still lacking in alpine regions. This study analyzed the annual and seasonal variability of the river discharge in the upper region of the Yarlung Zangbo River basin, investigated the climate-discharge relationship, and projected the annual trend in the next few decades (2021–2100) based on a distributed hydrological model (Soil and Water Assessment Tool, SWAT). Results show that river discharge did not show the same trend as precipitation at either annual or seasonal scale in the study area. It indicated that precipitation might not be the primary source of river discharge, and meltwater from snow, glacier, and frozen soil could account for a large percentage of river discharge. The projected river discharge would vary significantly among years with different changing rates under different climate change scenarios. Overall, this study contributes to investigate the unusual climate-discharge relationship which is different from that in the whole river basin. Moreover, to separately consider the parameters related to snow melt could significantly improve the simulation accuracy; however, it could be further improved by considering the freeze and thaw processes of soil and glacier which are not included in the SWAT model. [ABSTRACT FROM AUTHOR]

Spring snowmelt floods in the Arctic are common and can be expected every year, mainly because of the extensive snow cover that ablates relatively quickly. However, documentation of extreme flows (both low and high) in the Arctic is lacking in part because extreme flows are relatively rare and gauging sites are very sparse, with most of short duration. In the nested Kuparuk River research watersheds on the North Slope of Alaska, two large summer floods have been observed (July 1999 and August 2002) in the headwaters; these high flows are contrasted to the low flows (drought conditions) observed in the summers of 2005 and 2007. It is clear that the continuous permafrost and the limited near-surface storage in the shallow active layer are responsible for both the high and low flow responses. Or, stated another way, the active layer is a poor buffer to both floods and droughts. When contrasting summer floods with snowmelt floods, it is clear from flood frequency analyses that the smaller, high-gradient headwater basins will be dominated by summer floods while those watersheds draining the low gradient coastal plain will be dominated by snowmelt floods. The two summer floods in the headwaters had flows that were three to four times greater than the largest measured snowmelt flood, while on the coastal plain the 2002 summer storm for the whole of the Kuparuk River only produced the maximum summer runoff of record that was about 1/4 of the maximum snowmelt flood. So, on the coastal plain and even for the Greater Kuparuk River that drains across the coastal plain, snowmelt floods dominate. Drought conditions prevail in summers when the limited surface water storage in the active layer and surface water bodies is depleted because evapotranspiration exceeds precipitation. [ABSTRACT FROM AUTHOR]

Summary: Solute releases from a seasonal snowpack are important features of spring runoff in temperate climate zones because meltwater accounts for a significant proportion of contaminant loading to catchments. Here we report a study that traces the movement of natural and artificial solutes in snow through the processes of snow deposition, snowpack metamorphism, and snowmelt at the Central Sierra Snow Laboratory (CSSL), Soda Springs, California, USA. Rare earth elements (REEs) were added to the snowpack to mark individual snow layers. New snow, snowpack profiles and snowmelt were sampled and analyzed for REE and anion (, Cl− and ) concentrations. Correlations between and concentrations increased from new snow to snowpack profiles and to snow melt, suggesting significant redistributions of natural solutes in the snowpack. The maximum concentrations of and were both five times greater in the snow melt than in the new snow. Solute release by the snowpack was strongly controlled by weather conditions; high concentrations of natural tracers were observed at the onset of intensive melting episodes separated by relatively cold days of little melting. This weather pattern resulted in three ionic pulses rather than one. Natural solutes also showed a diurnal variation that was negatively correlated with the diurnal melting cycle. This pattern can be simulated by the standard water percolation equation linked with a mobile–immobile solute transport model (MIM). The diurnal variations of REE tracers showed positive association with the discharge, and cannot be satisfactorily simulated by the same model, suggesting that additional physical processes, such as dual or multiple flow regimes, may be needed to accurately describe solute transport in snow. [Copyright &y& Elsevier]

The article presents a series of experiments conducted that examined the influence of basal ice formation on runoff water chemistry. According to the author, a series of experiments were carried out and examination was done by comparing ion concentrations in runoff water to meltwater. Moreover, the author added that all samples collected were analyzed for major cations and anions. Results showed that compared to meltwater before basal ice contact, formation of basal ice layers can enrich the initial runoff water sometimes.

In contrast to the northern hemisphere where species of Chironomidae are usually the dominant benthic invertebrates in the coldest upper reaches of glacial streams, mayflies ( Deleatidium spp.: Leptophlebiidae) predominate in equivalent conditions in New Zealand. We examined the life histories and annual production of Deleatidium spp. at two sites on the Matukituki River (South Island, New Zealand) and at three sites in its glacier-fed tributary, Rob Roy Stream. Mean annual water temperature at the five sites ranged from 2.1 to 7.0°C. Monthly sampling showed that mayfly populations were poorly synchronised at all sites but were probably univoltine. The large Deleatidium cornutum was the dominant mayfly species found at the upper sites (Sites 1 and 2) on Rob Roy Stream, whereas above the confluence with Matukituki River (Site 3) it co-existed with a complex of smaller species we refer to as D. “ angustum”. Deleatidium “ angustum” also dominated at the Matukituki sites. Deleatidium production calculated for the five sites, assuming an 11-month nymphal life, ranged from 0.48 g dry weight/m2/year (Site 1) to 3.07 g dry weight/m2/year (Site 3). The values for D. cornutum at Sites 2 and 3 are high for a species of Deleatidium and reflect its large size. This species appears to be strongly adapted for growth at low temperatures. Climate change scenarios for New Zealand predict the gradual and ultimate loss of small South Island glaciers and a consequent warming of streams as runoff from rainfall and snow melt becomes more dominant in spring. As a result, suitable habitats will be lost for cold-water specialists such as D. cornutum, and they are likely to suffer reductions in their distributional range and local extinction. In contrast, species such as those in the D. “ angustum” complex may extend their ranges into streams formerly dominated by glacial meltwater. [ABSTRACT FROM AUTHOR]

This article discusses the periodic connectivity of lakes and streams on the semi-arid, subarctic Precambrian shield of Canada. According to the authors, the principle of fill and spill controls the lake connectivity from runoff during the snowmelt period. Rainfall in a semi-arid environment during the summer was insufficient to overcome a storage deficit to re-establish flow connectivity among all lakes. Water Balance indicates that snowmelt runoff led to a rise in lake levels above their outlet elevations. Hydrologic modeling of flow along a chain of Canadian lakes simulates the field observations.

This article discusses the losses of soil phosphorus in rainfall, snowmelt, and irrigation runoff from small watersheds in Alberta, Canada. Soil phosphorus was determined for the surface and three depth layers in the spring and fall. The relationship between phosphorus in the soil layers and runoff had similar extraction coefficients, intercepts, and predictive power. There were no significant differences among the soil sampling strategies. The relationships should aid in the prediction of phosphorus runoff in Alberta.

In cold Arctic snowpacks, meltwater retention is a significant factor controlling the timing and magnitude of runoff. Meltwater percolates vertically through the snowpack until it reaches an impermeable horizon, whereupon a saturated zone is established. If the underlying media is below the freezing point, accretive ice formation takes place. This process has previously been crudely parameterized or modelled numerically. Such ice is called either superimposed ice on glaciers or basal ice on bare land. Using theory derived from sea-ice formation, an analytical solution to basal ice growth is proposed. Results are compared against growth rates derived from numerical modelling. In addition, model results are compared to field observations of ice temperatures. The analytical solution is further extended to account for the temperature gradient inside the underlying media and the variable thermal properties of the underlying media. In the analysis, observations and references have predominantly relied on knowledge front glaciers. However, the process of accretive ice growth is equally important in seasonal snow packs with a cold snow-ground interface and on Arctic sex ice where the ice-snow interface is well below freezing point. The simplification of this accretive ice growth problem makes the solution attractive for incorporation in large-scale cryospheric models. [ABSTRACT FROM AUTHOR]

Abstract: Ocean circulation models indicate that freshwater runoff from the North American continent during the last deglaciation may have had an effect on North Atlantic Ocean circulation, and thereby have altered regional climate. One such example is a flood from Lake Agassiz, which has been proposed by previous workers to have caused the onset of the Younger Dryas at around 12,850 calibrated years B.P. by entering the North Atlantic through the Gulf of St. Lawrence. We present two radiocarbon ages from terrestrial organic sources in the Champlain Valley that we associate with the pre-Champlain Sea proglacial lake phases; a musk-ox bone with an AMS age of 11,362±115 14C years B.P. (13,438–13,020 calibrated years B.P.), and a wood fragment with an AMS age of 10,901±76 14C years B.P. (12,995–12,793 calibrated years B.P.). These ages together with a glacial lacustrine varve estimate suggest that the initiation of the Champlain Sea may not have occurred until after the onset of the Younger Dryas. If the Lake Agassiz flood event occurred before the opening of the Champlain Sea then the floodwaters would have been diverted down the Champlain and Hudson valleys to the North Atlantic. Another possibility is that the Agassiz flood may have been contemporaneous with the opening of the Gulf of St. Lawrence. It is also possible that there may have been a large enough flood produced by meltwater originating in the Champlain Valley and St. Lawrence Lowlands at the inception of the Champlain Sea to have affected ocean circulation without the influence of Lake Agassiz. [Copyright &y& Elsevier]

Previous research has highlighted the relationship between snow accumulation and forest stand characteristics, as well as the effects of topography, but not the variability within stands. This study examined spatial patterns in snow accumulation within forest stands, their consistency from year to year, and the extent to which they can be predicted from commonly used stand measurements. Snow water equivalent (SWE) was measured on or near April 1, 1995 to 1997, and a forest inventory was completed at 64 points (15-m grid spacing) in each of nine stand types including mature and juvenile forests and clearcuts. Semivariograms revealed little evidence of spatial correlation among sample points, indicating that each sample could be considered statistically independent for analysis. Within the study stands, no strong spatial trends were evident through quadratic trend surface analysis. The within-stand coefficient of variation (CV) generally decreased with increasing mean accumulation. Spearman's rank correlation analysis and principal components analysis (PCA) indicated a weak to moderate similarity in snow accumulation patterns from year to year. Site-scale canopy measures do not appear to provide a reliable basis for parameterizing the variability of within-stand snow deposition. Through the fitting of general linear models (GLM), year alone accounted for 33% of the variability in snow water equivalent within stands, on average. Of the stand inventory variables measured, crown closure explained the largest proportion of the variability in SWE within each stand, but together with year never more than 43%. The strongest correlations between snow water equivalent and crown closure were found in those stands exhibiting the greatest consistency in interannual spatial patterns of snow accumulation. [ABSTRACT FROM AUTHOR]

The transformation of snowmelt water chemical composition during melt, elution and runoff in an Arctic tundra basin is investigated. The chemistry of the water flowing along pathways from the surface of melting snow to the 95.5 ha basin outlet is related to relevant hydrological processes. In so doing, this paper offers physically based explanations for the transformation of major ion concentrations and loads of runoff water associated with snowmelt and rainfall along hydrological pathways to the stream outlet. Late-lying snowdrifts were found to influence the ion chemistry in adjacent reaches of the stream channel greatly. As the initial pulse of ion-rich melt water drained from the snowdrift and was conveyed through hilislope flowpaths, the concentrations of most ions increased, and the duration of the peak ionic pulse lengthened. Over the first 3 m of overland flow, the concentrations of all ions except for NO3- increased by one to two orders of magnitude, with the largest increase for K+, Ca2+ and Mg2+. This was roughly equivalent to the concentration increase that resulted from percolation of relatively dilute water through 0.25 m of unsaturated soil. The Na+ and Cl- were the dominant ions in snowmelt water, whereas Ca2+ and Mg2+ dominated the hillslope runoff. On slopes below a large melting snowdrift, ion concentrations of melt water flowing in the saturated layer of the soil were very similar to the relatively dilute concentrations found in surface runoff. However, once the snowdrift ablated, ion concentrations of subsurface flow increased above parent melt-water concentrations. Three seasonally characteristic hydrochemical regimes were identified in a stream reach adjacent to late-lying snowdrifts. In the first two stages, the water chemistry in the stream channel strongly resembled the hillslope drainage water. In the third stage, in-stream geochemical processes, including the weathering/ion exchange of Ca2+ and Mg2+, were the main control of streamwater chemistry. [ABSTRACT FROM AUTHOR]

The continuous increase in the emission of greenhouse gases has resulted in global warming, and substantial changes in the global climate are expected by the end of the current century. The reductions in mass, volume, area and length of glaciers on the global scale are considered as clear signals of a warmer climate. The increased rate of melting under a warmer climate has resulted in the retreating of glaciers. On the long-term scale, greater melting of glaciers during the coming years could lead to the depletion of available water resources and influence water flows in rivers. It is also very likely that such changes have occurred in Himalayan glaciers, but might have gone unnoticed or not studied in detail. The water resources of the Himalayan region may also be highly vulnerable to such climate changes, because more than 50% of the water resources of India are located in the various tributaries of the Ganges, Indus and the Brahmaputra river system, which are highly dependent on snow and glacier runoff. In the present study, the snowmelt model SNOWMOD has been used to simulate the melt runoff from a highly glacierized small basin for the summer season. The model simulated the distribution and volume of runoff with reasonably good accuracy. Based on a 2-year simulation, it is found that, on average, the contributions of glacier melt and rainfall in the total runoff are 87% and 13% respectively. The impact of climate change on the monthly distribution of runoff and total summer runoff has been studied with respect to plausible scenarios of temperature and rainfall, both individually and in combined scenarios. The analysis included six temperature scenarios ranging between 0.5 and 3 °C, and four rainfall scenarios (-10%, -5%, 5%, 10%). The combined scenarios were generated using temperature and rainfall scenarios. The combined scenarios represented a combination of warmer and drier and a combination of warmer and wetter conditions in the study area. The results indicate that, for the study basin, runoff increased linearly with increase in temperature and rainfall. For a temperature rise of 2 °C, the increase in summer streamflow is computed to be about 28%. Changes in rainfall by ±10% resulted in corresponding changes in streamflow by 4–3.5%. For the range of climatic scenarios considered, the changes in runoff are more sensitive to changes in temperature, compared with rainfall, which is likely due to the major contribution of melt water in runoff. Such studies are needed for proper assessment of available water resources under a changing climate in the Himalayan region. [ABSTRACT FROM AUTHOR]

Arctic spring landscapes are usually characterized by a mosaic of coexisting snow-covered and bare ground patches. This phenomenon has major implications for hydrological processes, including meltwater production and runoff. Furthermore, as indicated by aircraft observations, it affects land-surface-atmosphere exchanges, leading to a high degree of variability in surface energy terms during melt. The heterogeneity and related differences when certain parts of the landscape become snow free also affects the length of the growing season and the carbon cycle. Small-scale variability in arctic snowmelt is addressed here by combining a spatially distributed end-of-winter snow cover with simulations of variable snowmelt energy balance factors for the small arctic catchment of Trail Valley Creek (63 km2). Throughout the winter, snow in arctic tundra basins is redistributed by frequent blowing snow events. Areas of above- or below-average end-of-winter snow water equivalents were determined from land-cover classifications, topography, land-cover-based snow surveys, and distributed surface wind-field simulations. Topographic influences on major snowmelt energy balance factors (solar radiation and turbulent fluxes of sensible and latent heat) were modelled on a small-scale (40 m) basis. A spatially variable complete snowmelt energy balance was subsequently computed and applied to the distributed snow cover, allowing the simulation of the progress of melt throughout the basin. The emerging patterns compared very well visually to snow cover observations from satellite images and aerial photographs. Results show the relative importance of variable end-of-winter snow cover, spatially distributed melt energy fluxes, and local advection processes for the development of a patchy snow cover. This illustrates that the consideration of these processes is crucial for an accurate determination of snow-covered areas, as well as the location, timing, and amount of meltwater release from arctic catchments, and should, therefore, be included in hydrological models. Furthermore, the study shows the need for a subgrid parameterization of these factors in the land surface schemes of larger scale climate models. [ABSTRACT FROM AUTHOR]

Snow volume and melt timing are major factors influencing the water cycle at northern high altitudes and latitudes, yet both are hard to quantify or monitor in remote mountainous regions. Twice‐daily special sensor microwave imager (SSM/I) passive microwave observations of seasonal snow melt onset in the Wheaton River basin, Yukon Territory, Canada (∼60 ° 08′05″N, ∼134 ° 53′45″W), are used to test the idea that melt onset date and duration of snowpack melt–refreeze fluctuations control the timing of the early hydrograph peaks with predictable lags. This work uses the SSM/I satellite data from 1988 to 2002 to evaluate the chronology of melt and runoff patterns in the upper Yukon River basin. The Wheaton River is a small (875 km2) tributary to the Yukon, and is a subarctic, partly glacierized heterogeneous basin with near‐continuous hydrographic records dating back to 1966. SSM/I pixels are sensitive to melt onset due to the strong increase in snow emissivity, and have a robust signal, in spite of coarse (>25 × 25 km2) pixel resolution and varied terrain. Results show that Wheaton River peak flows closely follow the end of large daily variations in brightness temperature of pixels covering the Wheaton River, but the magnitude of flow is highly variable, as might be expected from interannual snow mass variability. Spring rise in the hydrograph follows the end of high diurnal brightness temperature (Tb) amplitude variations (DAV) by 0 to 5 days approximately 90% of the time for this basin. Subsequent work will compare these findings for a larger (7250 km2), unglacierized tributary, the Ross River, which is farther northeast (∼61 ° 59″40″N, ∼132 ° 22″40″W) in the Yukon Territory. These techniques will also be used to try to determine the improvement in melt detection and runoff prediction from the higher resolution (∼15 × 15 km2) advanced microwave scanning radiometer for EOS (AMSR‐E) sensor. Copyright © 2006 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

One of the most important parameters for spring runoff forecasting is the snow water equivalent on the watershed, often estimated by kriging using in situ measurements, and in some cases by remote sensing. It is known that kriging techniques provide little information on uncertainty, aside from the kriging variance. In this paper, two approaches using Bayesian hierarchical modelling are compared with ordinary kriging; Bayesian hierarchical modelling is a flexible and general statistical approach that uses observations and prior knowledge to make inferences on both unobserved data (snow water equivalent on the watershed where there is no measurements) and on the parameters (influence of the covariables, spatial interactions between the values of the process at various sites). The first approach models snow water equivalent as a Gaussian spatial process, for which the mean varies in space, and the other uses the theory of Markov random fields. Although kriging and the Bayesian models give similar point estimates, the latter provide more information on the distribution of the snow water equivalent. Furthermore, kriging may considerably underestimate interpolation error. Copyright © 2006 Environment Canada. Published by John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Since snowmelt runoff is important in the mountainous parts of the world, substantial efforts have been made to develop snowmelt models with many different levels of complexity to simulate the processes at the ground (soil–vegetation), within the snow, and at the interface with the atmosphere. Snow modifies the exchange of energy between the land surface and atmosphere and significantly affects the distribution of heating in the atmosphere by changing the surface albedo and regulating turbulent heat and momentum fluxes at the surface. Thus, for computing the amount of melt, the only strictly correct way is using an energy budget. A two‐layer point model (SNOBAL) was applied to calculate the energy and mass balance of snowmelt in the upper Karasu basin, in eastern Turkey, during the 2002–04 snow seasons. The data on snow and climate were provided from automated snow and meteorological stations installed and upgraded to collect high‐quality time series data of snow and meteorological variables, such as snow water equivalent, snow depth, precipitation and radiation, with automated data transfer. A number of analyses of snowpack energy and mass balance were carried out to understand the key processes that have major impacts on the snow simulation. Each form of energy transfer was evaluated during snow accumulation and ablation periods using a 2 h computational time step. The model results are appraised with respect both to temporal distribution (the model application for three consecutive snow seasons at one site) and to areal evaluation (the model application to three different sites for one season). The model performance is evaluated by comparing the results with observed snow water equivalent, snow depth and lysimeter yield. Copyright © 2006 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]