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Climate change vulnerability depends on whether organisms can disperse rapidly enough to keep pace with shifting temperatures and find suitable habitat along the way. Here, we develop a method to examine where and for which species shifting isotherms will outpace species dispersal using stream networks of the southern Appalachian Mountains (United States) and their highly speciose and endemic fish fauna as a model system. By exploring alternative tributary and mainstem dispersal pathways, we identify tributaries as slow-climate-velocity pathways along which some fish can successfully disperse and thus keep pace with climate change. Despite accessibility and thermal suitability, non-temperature habitat conditions in tributaries are unsuitable for some dispersing species, thus probably precluding establishment of persistent populations. Our findings demonstrate a trade-off shaping the efficacy of thermal refugia that depends on species-specific habitat associations and reveal individual-level dispersal behaviour, body size and stream network geometry as general correlates of climate change vulnerability.

Riverine ecosystems are governed by patterns of temporal variation in river flows. This dynamism will change due to climate change and the near-ubiquitous human control of river flows globally, which may have severe effects on species distributions and interactions. We employed a combination of population modelling and network theory to explore the consequences of possible flow regime futures on riparian plant communities, including scenarios of increased drought, flooding and flow homogenization (removal of flow variability). We found that even slight modifications to the historic natural flow regime had significant consequences for the structure of riparian plant networks. Networks of emergent interactions between plant guilds were most connected at the natural flow regime and became simplified with increasing flow alteration. The most influential component of flow alteration was flood reduction, with drought and flow homogenization both having greater simplifying community-wide consequences than increased flooding. These findings suggest that maintaining floods under future climates will be needed to overcome the negative long-term consequences of flow modification on riverine ecosystems.

Amplified climate change in polar regions is significantly altering regional ecosystems, yet there are few long-term records documenting these responses. The McMurdo Dry Valleys (MDV) cold desert ecosystem is the largest ice-free area of Antarctica, comprising soils, glaciers, meltwater streams and permanently ice-covered lakes. Multi-decadal records indicate that the MDV exhibited a distinct ecosystem response to an uncharacteristic austral summer and ensuing climatic shift. A decadal summer cooling phase ended in 2002 with intense glacial melt ('flood year')-a step-change in water availability triggering distinct changes in the ecosystem. Before 2002, the ecosystem exhibited synchronous behaviour: declining stream flow, decreasing lake levels, thickening lake ice cover, decreasing primary production in lakes and streams, and diminishing soil secondary production. Since 2002, summer air temperatures and solar flux have been relatively consistent, leading to lake level rise, lake ice thinning and elevated stream flow. Biological responses varied; one stream cyanobacterial mat type immediately increased production, but another stream mat type, soil invertebrates and lake primary productivity responded asynchronously a few years after 2002. This ecosystem response to a climatic anomaly demonstrates differential biological community responses to substantial perturbations, and the mediation of biological responses to climate change by changes in physical ecosystem properties.

Over time, the average global temperature has varied greatly, mainly due to natural phenomena. However, several anthropic activities have caused significant changes in the Earth's atmosphere, so that various greenhouse gases, especially CO2, have increased their atmospheric concentration and, consequently, produced an increase in the planet's temperature. These climatic changes, particularly global warming, can affect organisms in continental aquatic environments, including primary producers (e.g., macrophytes). Using photosynthetic parameters calculated from chlorophyll a fluorescence and measurements of chlorophyll a content, we assessed the potential effects of temperature increases predicted by two future scenarios from the fifth assessment report of the Intergovernmental Panel on Climate Change (IPCC), Representative Concentration Pathway 4.5 (RCP 4.5) and Representative Concentration Pathway 8.5 (RCP 8.5), on the photosynthetic responses of five aquatic macrophytes from tropical lotic ecosystems. Our results showed a trend of a reduction in the φPSII values associated, as a rule, with an increase in the heat dissipation values in the reaction centers of photosystem II, that is, parameter E. Such reductions in the φPSII associated with increases in parameter E suggest that most likely, even the less severe RCP scenario, RCP 4.5, is already sufficient to negatively and significantly affect the photosynthetic responses of most aquatic macrophytes tested in this experimental study. Considering that macrophytes, alongside macroalgae and periphyton, form the basis of autotrophic food webs in tropical lotic ecosystems, our results suggest that there is a real possibility that the negative effects produced by global warming on these primary producers are propagated, as a "cascade effect", indirectly affecting higher trophic levels as well. [ABSTRACT FROM AUTHOR]

Mass mortality of Unionidae from the genera Middendorffinaia, Buldowskia, and Sinanodonta was observed in the plain rivers of the south of Primorsky Krai (south of the Russian Far East) in the abnormally hot and low-water summer–autumn season of 2021. Nodularia douglasiae (Griffith et Pidgeon, 1833) was the most resistant and thus least affected species, the species from the genera Sinanodonta and Middendorffinaia, the least resistant and the most affected. [ABSTRACT FROM AUTHOR]

Climate change is a matter of worldwide concern with severe predicted impacts on biodiversity. Here, we analysed the potential impacts of current and future climates on aquatic true bugs (Heteroptera) in relation to their distribution patterns and ecological preferences (based on a database generated from existing literature references and field collections). We considered the traits as 'species thermal range' and 'emergence period' to evaluate the future climate change impacts on the distributions of aquatic true bugs in the riverine regions of a tropical biodiversity hotspot, the Western Ghats of India. We used Species Distribution Models (SDMs) to evaluate the potential impacts of climate change on the distributions of aquatic true bugs. We modelled the distributions of twenty-six species of aquatic true bugs using different modelling tools through a carefully examined set of occurrence records to generate potential present distributions and to project these distributions into future scenarios of climate change. We observed increasing/decreasing range sizes of the species in the current and future scenarios. We found losses and increases of species' ranges in some regions, but not much variation in species richness. Similarly, no significant effect was observed in the distribution ranges for species with different duration of emergence period and thermal range in current and future climatic scenarios. Losses and gains in species richness would be concentrated in the mountainous area of the Western Ghats, whereas loss of species and the bigger difference between current and future richness will occur in the adjacent lowlands and towards central regions, including the network of protected areas of the Western Ghats. These areas are critical to buffer regional species loss in the future. Implications for insect conservation: Given the importance of aquatic true bugs as bioindicators and biological control agents, monitoring their range shifts should be routinely addressed in the conservation contexts of the Western Ghats. [ABSTRACT FROM AUTHOR]

Ecosystems respond to climatic and anthropogenic forcings with regime shifts and reorganizations of their system structures. In river basins, changes in sediment transport can have cascading effects that cause ecosystem regime shifts. The Yellow River, once the world's most sediment-rich river, has experienced dramatic regime shifts. Although recent intervention has returned sediment discharge in the Yellow River to pristine levels, our understanding of previous regime shifts remains inadequate, particularly for the regime shift to a sediment rich period during early historical time. We reanalyzed previous datasets to clarify the first historical sediment transport regime shift in the Yellow River. Our results show that while historical climatic changes (e.g., the Medieval Warm Period, about 900–1100 AD) caused changes in sediment transport, a regime shift occurred only under increased forcing from anthropogenic stresses (started from about 1350 AD, reached the tipping point after 1900 AD). This unique behavior of the Yellow River under increasing anthropogenic forces may provide perspective for sustainable river basin management. [ABSTRACT FROM AUTHOR]

Global change is predicted to have a marked impact on freshwater ecosystems in the High Arctic, including temperature increase, enhanced precipitation, permafrost degradation and increased vegetation cover. These changes in river catchments can alter flow regime, solute transport to streams and substantially affect stream ecosystem functioning. The objective of this study was to evaluate changes in stream functioning in a high-Arctic stream in relation to changes in discharge, and runoff flow path. We measured environmental factors, biofilm structure, nutrient uptake rates and metabolism. We studied three reaches in a headwater stream in NE Greenland with different catchment characteristics in early and late summer (during two different years) to evaluate the potential influence of environmental change on Arctic stream ecosystem functioning. Highest nutrient uptake, primary production and ecosystem respiration was found in late summer showing that streams are more efficient at retaining nutrients and have higher autotrophic production, likely due to less impact of snowmelt, and lower discharge increasing the surface to volume ratio between streambed and water column. Nutrient uptake rates in late summer from high-Arctic tundra streams were comparable to uptake rates in temperate pristine streams, likely due to no shading by bank vegetation and longer days in the high-Arctic summer compared to temperate streams. Overall, the results of this study aids in the endeavor of predicting how climate-derived changes will affect in-stream nutrient uptake and metabolism in high-Arctic streams. The results suggest that their capacity to transport, cycle and retain carbon and nutrient may increase if the importance of soil water flow paths for streams also increase, thus with effect to stream trophic relations and solute export to coastal areas. [ABSTRACT FROM AUTHOR]

Importance of evaluation of global hydrological models (gHMs) before doing climate impact assessment was underlined in several studies. The main objective of this study is to evaluate the performance of six gHMs in simulating observed discharge for a set of 57 large catchments applying common metrics with thresholds for the monthly and seasonal dynamics and summarize them estimating an aggregated index of model performance for each model in each basin. One model showed a good performance, and other five showed a weak or poor performance in most of the basins. In 15 catchments, evaluation results of all models were poor. The model evaluation was supplemented by climate impact assessment for a subset of 12 representative catchments using (1) usual ensemble mean approach and (2) weighted mean approach based on model performance, and the outcomes were compared. The comparison of impacts in terms of mean monthly and mean annual discharges using two approaches has shown that in four basins, differences were negligible or small, and in eight catchments, differences in mean monthly, mean annual discharge or both were moderate to large. The spreads were notably decreased in most cases when the second method was applied. It can be concluded that for improving credibility of projections, the model evaluation and application of the weighted mean approach could be recommended, especially if the mean monthly (seasonal) impacts are of interest, whereas the ensemble mean approach could be applied for projecting the mean annual changes. The calibration of gHMs could improve their performance and, consequently, the credibility of projections. [ABSTRACT FROM AUTHOR]

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The Miankaleh wetland, one of the richest ecosystems in the north of Iran, has experienced an unprecedented environmental degradation caused by overexploitation of the water resources and climatic changes in recent years. This research aims to estimate the environmental water requirement (EWR) for the rivers that drain into the wetland. For this purpose, comprehensive data were collected through physiographic, climatic, hydrologic, ecologic, and field studies of the wetland and its drainage basin. To estimate the EWR, we applied several methods including the Tenant, the Eco-deficit, the flow duration curve, the Wetted-Perimeter method, and the physical habitat simulation model (PHABSIM) and the results were evaluated based on the natural discharge of the rivers before retrogression of the Miankaleh wetland. Further, the results showed that the consideration should be given to the Wetted-Perimeter and the PHABSIM Model for estimation of the EWR for the rivers of the Miankaleh wetland given the seasonality of the rivers and hydroclimatic condition of the study area. The mean annual EWR of the rivers was estimated between 0.12 and 2.03 m3/s, which is close to the values of the bank full flows. The current discharge of the rivers are less than the estimated EWR, showing the discharge rates do not meet the water requirement for aquatic species of the Miankaleh wetland [ABSTRACT FROM AUTHOR]

Geography and nursery-specific dynamics guide environmental drivers of growth for young-of-year (YOY; larval and juvenile) Alewife (Alosa pseudoharengus) and Blueback Herring (Alosa aestivalis), two species collectively termed river herring; of these factors, temperature is considered one of the most influential. To better understand future YOY growth relative to climate change, this study was designed to determine the site-specific growth rates of YOY river herring in Potomac River tributaries, and determine if temperature was a driving factor of growth. Daily ages were ascertained from YOY otoliths and used to calculate growth rates using nine growth models. Weighted Akaike information criterion (AICw) determined the best-fit model for both species was the von Bertalanffy growth model. Von Bertalanffy growth parameters differed between species (p < 0.0001), between years for both species (p < 0.0001), and between locations for Blueback Herring (p = 0.0002), emphasizing the need for species-specific assessments. Standard length and cumulative growing degree-days were highly correlated within each year for both species, but significantly different between species and years for each species (Pearson's r = 0.740–0.913, p < 0.0001). Estimating site-specific growth rates and drivers of growth can help managers determine the potential of Potomac River tributaries as viable nurseries in future climates. [ABSTRACT FROM AUTHOR]

Originating in the Tianshan Mountains in arid Central Asia, the natural discharge change of the Naryn River is strongly affected by climate change. As the main source of water for the region, this river is crucial to both the natural environment and the socio-economic development. To extend the discharge record and better understand past and future changes in Naryn River discharge, we developed four tree-ring width chronologies and analyzed the relationship between tree growth and discharge. The resulting reconstruction dates back to 1753 and has an R2 of 0.374 (1939–2017). Interannual discharge variations of the Naryn River indicate that 1917 was the driest year of the past 265 years, while 1956 was the wettest. The record also indicates that the majority of extreme flood years occurred in the past century; prior to about 1900 C.E., the discharge of the Naryn River was relatively stable. Since 1900 C.E., discharge volume has gradually increased, as has discharge variability. At decadal time scales, the 2010s are notable for the frequency of major floods, whereas the 1910s were the driest. Between the 1870s and the 1910s, the Naryn River experienced a period of low discharge that continued for nearly half a century. The discharge of the Naryn River over the past 265 years appears to vary over quasi-periods of 60, 21, 11, and 2-4 years, which are driven by large-scale climate systems. [ABSTRACT FROM AUTHOR]

Climate change and human activities are affecting the ecological health of rivers and the economic value of its ecosystem services. Taking water quantity as the intermediate variable, we proposed a quantitative calculation method for the impact of climate change and human activities on the economic value produced by the ecosystem service functions of rivers. The framework mainly consists of three steps: firstly, we quantitatively determined the changes in the amount of water coming from rivers due to climate change and human activities; secondly, combining the theory of resource and environmental economics to calculate the economic value generated by ecological service functions of rivers; finally, we quantitatively identified and analyzed the impact of climate change and human activities on the economic value produced by the ecosystem service functions of rivers. Taking Baoji section of Weihe River (BSWR) as an example, we quantitatively analyzed and calculated the impact of climate change and human activities on the economic value produced by ecosystem service functions of rivers. The main conclusions of this paper are as follows: in recent 52 years, the economic value produced by the ecosystem service functions of rivers decreased by 3.57 billion yuan due to the climate change and human activities; the total economic value has been reduced by an average of 68 million yuan per year. This useful work can not only reveal the impact of climate change and human activities on the economic value of ecosystem services of rivers but also can provide an important basis for the reasonable management model of water resource of ecosystem of rivers watershed. [ABSTRACT FROM AUTHOR]

Temporary streams are submitted to high seasonal hydrological variations which induce habitat fragmentation. Global change promotes longer non-flow periods, affecting hydrological continuity and the distribution of biological assemblages in river networks. We aimed to investigate the effects of hydrological discontinuity on phototrophic biofilm assemblages in a Mediterranean stream, at both network and habitat scales. At the network scale during basal flow conditions, mostly nitrate and DOC concentrations were associated to the taxonomical and trait distribution of algae and cyanobacterial assemblages. Cyanobacteria dominated at the upstream and downstream sites of the network, while green algae and diatoms were abundant in its middle part. At the habitat scale, hydrological discontinuity promoted large changes in biofilm composition between riffles and pools, where pools were inhabited preferentially by green algae and riffle habitats by cyanobacteria. Our findings emphasize the myriad of factors affecting the spatial distribution of phototrophic biofilms, which become more heterogeneous according to water flow interruption. Under the predicted climate change scenarios, spatial heterogeneity in temporary streams may increase, which will lead to change phototrophic biofilm assemblages. [ABSTRACT FROM AUTHOR]

Small water bodies are critical for maintaining freshwater biodiversity, but are among the least investigated aquatic environments. We examined physical and chemical variables at two reaches in Arroyo Tambillos, a small, high-elevation Andean stream, in NW Mendoza province, Argentina, across four seasons to examine how local factors and seasonality affected the structure of the macroinvertebrate community. The Arroyo Tambillos community was numerically dominated by ephemeropterans (mainly Massartellopsis irarrazavali) while the dipteran Chironomidae were the most species rich. Total macroinvertebrate abundance was highest in summer, driven mainly by taxa that were secondary in dominance (Austrelmis sp. and Andesiops peruvianus), while richness did not differ between seasons. However, benthic composition was different in Fall 2013 (March) compared to other seasons, largely because of the increased abundance of Chironomidae. Canonical correspondence analysis discriminated Chironomidae species distributions in Fall 2013 by substrate type (i.e., big and small boulder substrate). By contrast, discharge, velocity, and depth were the variables which most affected the macroinvertebrate abundance and distributions. Contrary to our expectations, most community changes observed occurred in fall instead of summer. Nivo-kryal stream communities like the one described here have become increasingly important for conserving mountain stream biodiversity as anthropogentic impacts and climate change increasingly impact lower stream reaches. Therefore, monitoring high-altitude streams like the Arroyo Tambillos may be critical for preventing the future loss of unique and sensitive stream biota. [ABSTRACT FROM AUTHOR]

Coincidental long-term changes in estuarine nekton assemblages and environmental conditions are widely reported. In this study, from a warm-temperate, high salinity, salt marsh-dominated estuary in the southeastern USA, decreases in overall abundance, shifts in species and life stage composition, and changes in seasonal patterns of occurrence coincided with increased water temperature. Biweekly trawl collections in a subtidal creek were made during two 4-year periods separated by more than 30 years. Of the total 111 taxa in the North Inlet estuary, South Carolina, 64% (71) occurred during both the historic (1981–84) and recent (2013–16) periods. The top five species and their proportions of the total annual catches changed between periods. In the recent study period, near-bottom species (Lagodon rhomboides, Bairdiella chrysoura, Litopenaeus setiferus) increased, and pelagic species (Anchoa spp. and Lolliguncula brevis) decreased. The mean abundance of total nekton in the recent period was approximately 50% of historic abundance. Large, but temporary increases in nekton abundance occurred when salinity decreased after major storms. In the recent study period, shifts in the timing of peak abundances from spring to fall, the occurrence of juveniles during winter, and increased diversity suggested responses to significantly warmer winters and summers. Over the 30 year period, the subtidal nekton assemblage transitioned to a state of lower abundance and different composition. Future increases in water temperature, incidences of major storms, and modifications of estuarine habitats due to rising sea level could lead to additional changes in the fauna of warm-temperate estuaries. [ABSTRACT FROM AUTHOR]

For two hydrological models, the ECOMAG and SWAP, the hypothesis is checked that a model which has successfully passed the test based on observational data is more efficient for assessing future hydrological consequences of climate change than the models which did not pass the test. The efficiency is evaluated using two criteria: the robustness of a model and the uncertainty of simulation results. Three versions of each model constructed for the basins of the Lena and Mackenzie rivers are examined: the model whose parameters are set a priori (without calibration), the model which was calibrated against runoff hydrographs at the outlet, and the model which was calibrated against runoff hydrographs at several gaging stations of the river network. The estimates of possible changes in the river runoff by the end of the 21st century are obtained using data of global climate models. It is shown that the hydrological model which successfully passed the proposed testing procedure is more effective for assessing climate change impact on the river runoff. [ABSTRACT FROM AUTHOR]

In 1999, Diexi paleo-dammed lake (2349 m a.s.l.) was discovered around Diexi town along the Minjiang River in Sichuan province. Diexi is located where the eastern edge of the Tibetan Plateau and the Sichuan Basin meet. The dammed lake was formed during the Last Glacial Maximum of the Late Pleistocene (~30,000 years ago) and began to empty about 15,000 years ago. The lacustrine sediments (up to 240 m thick) preserve abundant paleoenvironment information. In this paper, a mass of oxygen isotopes and 14C dating from drilled cores are analyzed and discussed. The δ18O curve on the paleo climate from this section is comparable with the coeval paleo climatic curves of ice cores and karsts in China and others. Furthermore, the physical model testing has confirmed that the disturbed zones in the core are caused by strong earthquakes occurred at least 10 times, which implies strong crustal deformation, as an important driving force, affecting climate change. This study provides a new window to observe East Asian monsoon formation, paleoenvironmental evolution and the global climate change. [ABSTRACT FROM AUTHOR]

Rivers provide crucial ecosystem services in water-stressed drylands. Australian dryland rivers are geomorphologically diverse, ranging from through-going, single channels to discontinuous, multi-channelled systems, yet we have limited understanding of their sensitivity to future hydroclimatic changes. Here, we characterise for the first time the geomorphology of 29 dryland rivers with catchments across a humid to arid gradient covering >1,800,000 km2 of continental eastern and central Australia. Statistical separation of five specific dominantly alluvial river types and quantification of their present-day catchment hydroclimates enables identification of potential thresholds of change. Projected aridity increases across eastern Australia by 2070 (RCP4.5) will result in ~80% of the dryland rivers crossing a threshold from one type to another, manifesting in major geomorphological changes. Dramatic cases will see currently through-going rivers (e.g. Murrumbidgee, Macintyre) experience step changes towards greater discontinuity, characterised by pronounced downstream declines in channel size and local termination. Expanding our approach to include other river styles (e.g. mixed bedrock-alluvial) would allow similar analyses of dryland rivers globally where hydroclimate is an important driver of change. Early identification of dryland river responses to future hydroclimatic change has far-reaching implications for the ~2 billion people that live in drylands and rely on riverine ecosystem services. [ABSTRACT FROM AUTHOR]

Extreme temperatures have increased in intensity, duration and frequency in the last century, with potential consequences on key ecological processes such as organic matter breakdown. Many stream ecosystems are fueled by the breakdown of terrestrial leaf litter, which is exposed to atmospheric conditions for certain periods of time before entering the stream. Thus, extreme warming or freezing events may affect the litter physicochemical structure, which could translate into altered breakdown within the stream. The above prediction was tested by exposing litter of common riparian tree species in southern Chile to freezing (−20 ºC; dry or wet litter) or heating (40 ºC) and comparing breakdown with control litter exposed to room temperature (20 ºC), separating the effects of different breakdown agents (i.e., leaching, microorganisms and detritivores). The greatest effects were found in wet litter subjected to freezing; this treatment significantly increased leaching in the short term (48 h) and slowed down breakdown in the long term (30 days), mostly due to the inhibition of microbial breakdown. Heating also retarded microbial breakdown, but the effect was smaller. Our results suggest that short-term extreme temperatures—particularly cold ones—have the potential to slow down litter breakdown in streams, which will most likely impact global biogeochemical cycles where streams play a key role. [ABSTRACT FROM AUTHOR]

Climatic changes have a significant impact on the hydrologic behavior of a river especially its discharge. Sustainable management of water resources necessitates an examination of spatiotemporal variation in climatic parameters such as precipitation and temperature to quantify their relationships with the river discharge. The present study develops both parametric and non-parametric models by modifying the tools of 'R' statistical software (version 3.2.2) to investigate variations in 11 climatic parameters for a 117-year dataset (1900–2017) in Ganges River basin of India. The novelty of the modified hydroclimatic spatiotemporal trend model is its ability to explore seasonal trends and Sen's slopes of climatic parameters while avoiding trend-autocorrelation complications using an advanced Mann–Kendall test and Sen's slope estimator. Furthermore, relationships among the Sen's slopes of each climatic parameter are assessed to investigate the trend interdependencies. Parametric modeling has been performed to develop relationships among precipitation and remaining climatic parameters. Model validation results suggest non-parametric model to quantify relationships between precipitation and river discharge for a long-term data series. The results demonstrate that the forecasted precipitation exhibits a gradually decreasing trend leading to a significantly decreasing trend in river discharge (15–21%) for the next three decades (2030, 2040 and 2050). The model outcomes guide the water managers towards framing sustainable policies for managing water supplies, floods and droughts, hydropower development, barrage operation control, and environmental flows. [ABSTRACT FROM AUTHOR]

The Green Sturgeon is a long-lived anadromous fish known to spawn in only three locations. Southern Distinct Population Segment (DPS) Green Sturgeon spawn only in the Sacramento drainage, while the Northern DPS spawns in the Klamath and Rogue rivers. In 2011, a young of year (YOY) Green Sturgeon was captured in the Columbia River below Bonneville Dam, providing preliminary evidence of a fourth spawning location. In 2017, four additional Green Sturgeon YOY of similar size were captured in the Columbia River below Bonneville Dam. Genetic analysis of all YOY samples indicates that they belong to the Northern DPS, confirming that the Northern DPS actually spawns in at least three locations. The detection of Green Sturgeon spawning in the Columbia River only in years with relatively high spring flow (2011, 2017), combined with confirmed correlations between flow and spawning for other White and Green Sturgeon populations, suggests that appropriate spawning conditions may only exist above a specific flow threshold. The Columbia River has the potential to play an important role in Green Sturgeon climate change adaptation due to its location at the northernmost end of the species' reproductive range. We recommend future research to better quantify Green Sturgeon recruitment magnitude, frequency and dynamics in the Columbia River. [ABSTRACT FROM AUTHOR]

Tropical regions are characterized by hydrological extreme events, which are likely to be exacerbated by climate change. Therefore, quantifying the extent to which climate change may damage a hydrological system becomes crucial. This paper aims to evaluate the findings from previous research on projected impacts of climate change on hydrological systems located in regions bounded by the Tropic of Cancer and the Tropic of Capricorn. It intends to provide an in-depth understanding of the climatic conditions, applied approaches, climate change impacts on future streamflow, and measures to reduce prediction uncertainty in the tropics. The review revealed that there is a significant variation in the magnitude of climate change impacts on streamflow in the tropics. The reason for the inconsistent trend prediction is that projections are heavily dependent on the trajectory of greenhouse gas emissions, climate model structural differences, and uncertainty of downscaling methods and hydrological models. Therefore, to minimize the uncertainty and maximize confidence in streamflow projections, it is essential to apply multi-member model ensembles and to clarify the adaptation strategy (coping, adjusting, or transforming). [ABSTRACT FROM AUTHOR]

Ice phenomena are a major component of the hydrological regime of east-central and northern European rivers. However, their occurrence disturbs inland water transportation, particularly affecting the major rivers of the Central European Plain that are part of Europe's international waterways. The Oder is one of these rivers, and is located on the boundary between the much warmer and the much colder part of the temperate climatic zone. This makes the course of ice phenomena on the river difficult to predict. The main purpose of this work is to document and analyse the dynamic of changes occurring for over 60 years (1956–2015) in the ice phenomena of a river that demonstrates a transitional ice regime. It was found that the duration of all ice phenomena decreased (by up to 0.58 days·year−1) and so did the duration of ice cover (by up to 0.46 days·year−1). The rates and trends of the two parameters were, however, different in different parts of the lower stretch of the river. This fact is especially important in the context of climate changes whose characteristics include an increased incidence of extreme weather situations, both meteorological and hydrological. There was also found to be a strong correlation (R2 from 0.69 to 0.81) between the duration of ice phenomena and the mean air temperature in winter (December to February) and a much weaker correlation between the duration of ice phenomena and the NAO index (R2 from 0.42 to 0.48). Such a little correlation of ice phenomena with NAO is likely to result from the pollution of the Oder River (in particular in the second half of the twentieth century) and icebreaking operations on the river. [ABSTRACT FROM AUTHOR]

The inland location of Mongolia and its relatively high general elevation above sea level combined with the arid climate favor the formation of the specific hydrological regime of water bodies which are highly vulnerable to climate changes. The formation features and the current state of water resources in Mongolia are considered. A brief description of the main water bodies is given. The available estimates of the impact of anthropogenic factors and climate changes on some components of water balance are discussed. [ABSTRACT FROM AUTHOR]

Projected changes in river runoff due to possible climate change during the 21st century were simulated with making use of a physically-based land surface model SWAP and meteorological projections simulated by five Global Climate Models (GCMs) for each of four RCP scenarios. The Northern Dvina, Indigirka, and Taz river basins were used in the study. For each basin, 20 projections of changes in climatic river runoff were obtained for three climatic periods of the 21st century. The projected changes in climatic river runoff were analyzed together with the projected changes in climatic precipitation, incoming shortwave and longwave radiation, and evapotranspiration. The obtained hydrological projections were used to estimate their uncertainties resulting from the application of different GCMs and RCP scenarios. [ABSTRACT FROM AUTHOR]

Building resilient infrastructure is one of the major challenges faced by cities due to increasing urbanization rates and climate change. Furthermore, the application of vulnerability assessment frameworks is a significant challenge that requires the appropriate tools for decision makers. This text analyses an ongoing green infrastructure (GI) project in the city of Cali, Colombia, by presenting the assessment methodology and identifying the main benefits and vulnerability reduction possibilities resulting from the intervention. The main objective of this research focuses on (1) assessing the impact of flood risk in urban areas using GIS techniques; (2) mapping and quantifying vulnerability reduction due to the intervention in a simulation scenario; and (3) exploring the feasibility of GI projects as a tool for decision-making processes. [ABSTRACT FROM AUTHOR]

Insights from long-term subsistence fisheries data can improve our understanding of the population-specific responses of Arctic charr, Salvelinus alpinus, to environmental conditions. In this study, associations were found between temporal environmental variation and Arctic charr length- and weight-based growth using data from fish captured in the Hornaday River fishery. Overall, spring precipitation and summer air temperature appear to be the most important environmental influences on Arctic charr probably because of their respective impacts on the opportunities for acquiring surplus energy for growth. A pattern of decreasing age-related importance of temperature and increasing age-related importance of precipitation suggested that the coupling between growth and environmental effects varied by life-period. The changing prominence of each variable seems to result from the shift in apportioning energy for increases in length to increases in weight, likely as a result of the onset of maturation. The linkage of population characteristics to environmental conditions provides a baseline reference against which future data may be compared to determine the significance of any observed changes in population characteristics as a result of continuing ecological change in the north. [ABSTRACT FROM AUTHOR]

The aim of the study was to establish the strength and direction of the relationship between daily temperature of river water and air with the use of selected estimation methods. The relationship was assessed for the River Noteć and its tributaries (Western Poland), using the cross-correlation function and Granger causality. The study established cause-and-effect relations for "water–air" and "air–water" directions of influence. It was confirmed that forecasting the pattern of flowing water temperature from changes in air temperature yields better results when done based on data from the previous day. Results of modelling the relationship between data series with the use of the linear and natural cubic splines models confirmed the presence of a nonlinear relation. It was also established that there is a statistically significant correlation of random fluctuations for both temperature series on the same days. This made it possible to confirm the occurrence of short-term connections between water and air temperature. The results can be used to determine the qualities of thermal regimes and to predict temperature of river waters in the conditions of climate change. [ABSTRACT FROM AUTHOR]

Farmers may adapt to climate change by substituting away from the crops most severely affected. In this paper we estimate the substitution caused by a moderate change in climate in the US Midwest. We pair a 10-year panel of satellite-based crop coverage with spatially explicit soil data and a fine-scale weather data set. Combining a proportion type model with local regressions, we simultaneously address the econometric issues of proportion dependent variables and spatial correlation of unobserved factors. We find the change in expected crop coverage and then we link those changes to the expected changes from an estimated climate dependent yield equation. Ceteris paribus, we find that climate induced changes in yield are offset by land coverage changes for rice and cotton but they are strongly amplified for corn and soy. [ABSTRACT FROM AUTHOR]

Presented are the results from investigating carbon balance in forests of the transboundary Selenga river basin, based on inventory data for the status of forest reserves and he key factors (tree felling and forest fires) influencing carbon absorption and emission in forests. Analysis of the forest reserves in the Buryat and Mongolian parts of the Selenga river basin revealed distinctive features in the age structure of forests (middle-aged and young tree stands are dominant in Buryatia, and mature and overmature stands in Mongolia), and in the structure of lands of forest reserves (an increase in forest area is observed in Buryatia, whereas Mongolia shows the reverse trend). It is established that these differences are influenced by the practices of forest management and by the organization of the forest protection against fires in neighboring countries. The ROBUL technique was used to obtain estimates of carbon budget. A comparative analysis of carbon balance showed that the potential of forests of Buryatia in carbon absorption (deposition) is by a factor of 3 larger than forests of Mongolia. It is concluded that the amount and sign of carbon budget of forests growing in neighboring territories are determined by the current age structure of forests and by the intensity of destructive disturbances (carbon losses as a result of tree felling, forest fires and death of tree stands), because the carbon absorption by forests is characterized by a relative stability. The contribution from various carbon pools of the forest ecosystem to the total carbon stock and deposition (absorption) by forests is shown. Results obtained from assessing carbon budget can serve as a basis for developing the forest management and forest use strategy within the framework of transboundary cooperation of neighboring countries in order to minimize the negative effects of climate change and make effective use of its potential benefits. [ABSTRACT FROM AUTHOR]

Water temperature is a key determinant of biological processes in rivers. Temperature in northern latitude rivers is expected to increase under climate change, with potentially adverse consequences for cold water-adapted species. In Canada, little is currently known about the timescales or magnitude of river temperature change, particularly in large (≥104 km2) watersheds. However, because Canadian watersheds are home to a large number of temperature-sensitive organisms, there is a pressing need to understand the potential impacts of climate change on thermal habitats. This paper presents the results of a study to simulate the effects of climate change on the thermal regime of the lower Saint John River (SJR), a large, heavily impounded, socio-economically important watershed in eastern Canada. The CEQUEAU hydrological-water temperature model was calibrated against river temperature observations and driven using meteorological projections from a series of regional climate models. Changes in water temperature were assessed for three future periods (2030-2034, 2070-2074 and 2095-2099). Results show that mean water temperature in the SJR will increase by approximately ~1 °C by 2070-2074 and a further ~1 °C by 2095-2099, with similar findings for the maximum, minimum and standard deviation. We calculated a range of temperature metrics pertaining to the Atlantic Salmon and Striped Bass, key species within the SJR. Results show that while the SJR will become increasingly thermally-limiting for Atlantic Salmon, the Striped Bass growth season may actually lengthen under climate change. These results provide an insight into how climate change may affect thermal habitats for fish in eastern Canadian rivers. [ABSTRACT FROM AUTHOR]

This study establishes whether analysing the distribution patterns of wetlands could identify key systems that would focus conservation and management decisions, without site-specific data which requires significant logistical and financial resources. In the proposed approach, key wetlands at-risk were identified based on their position in the landscape, through the use of probability modelling and least-cost analyses. The research was based in a semi-arid part of the Eastern Cape, South Africa. The study area has aseasonal rainfall, different land-use zones and an existing spatial dataset, providing an ideal setting to test this method. Wetlands were highly clustered, with higher densities recorded in the south and along larger rivers. Areas that have more-suitable environmental conditions for wetlands were mapped—showing similar patterns to known dense wetland areas. In total, 89 systems were identified as very high-risk, and 414 wetlands were high-risk, to environmental and anthropogenic changes. Seven focal zones were selected by incorporating wetland clusters/hotspots. These zones should be the focus for further research and management that would assess the surrounding environment and the potential effects of land-use or climate changes, and policy adaptation. In summary, this study successfully illustrated the importance of adapting different spatial analytical methods in wetland research, and that desktop studies can be used to focus conservation and management efforts over larger areas. [ABSTRACT FROM AUTHOR]

This paper explores the possibility of using a calibrated rainfall-runoff model as a decision-making tool in sustainable water sharing. Designing institutional arrangements for runoff sharing process in the case of a sub-catchment spread across geopolitical boundary is challenging. For the water sharing arrangement to be sustainable, it must be founded on realistic runoff predictions. The climate uncertainties make the water sharing process more complex and complicated. This context warrants a decision-making tool for helping the water sharing policy makers and its managers in taking a decision. In this study, a decision-making tool for sharing the waters of Parambikulam sub-catchment in Southern Peninsular India is developed. RRL (Rainfall-Runoff Library), RAP (River Analysis Package) and SCL (Stochastic Climate Library) of eWater toolkit are used for developing this tool. In the decision making, it also incorporates the runoff change prediction portrayed in India’s second national communication to UNFCC. The existing institutional arrangement for water sharing of this sub-catchment is revisited in the light of findings of this study. Paper is concluded by explaining how it is useful in synthesizing a range of options on designing a new water sharing paradigm for this sub-catchment. [ABSTRACT FROM AUTHOR]

In this study, temperature extremes are analyzed for observed (1979-2005) and projected scenarios using three global climate models (GCMs) and their Representative Concentration Pathways (RCPs) based on Coupled Model Intercomparison Project Phase 5 (CMIP5) datasets, to investigate the spatio-temporal variations and possible changes in joint probability behavior of temperature extremes over North Sikkim Himalaya, India. Statistical downscaling model (SDSM) and copulas are applied to downscale the GCM outputs and to construct joint probability distribution of extremes, respectively. A set of ten climate extreme indices are selected to understand the inter-annual variability. Joint return period of extreme indices was calculated using six temperature extreme indices (based on days). Linear trends were estimated using Mann Kendall test with statistical significance and indicated widespread significant changes in temperature extremes. The significant changes in temperature extremes such as the temperature of warmest night and day have increased by 1.41 and 1.83 °C, and the temperature of coldest night and day has decreased by 3.61 and 4.83 °C, respectively, during 2006-2100 with the baseline period of 1979-2005. The spatial distribution of 5-year return periods and 10-year return periods is almost similar during 1979-2005. There is less co-occurrence of warm nights and days, but higher chance to co-occurrence of cool and warm nights in the same year during 2021-2100. The change in joint return periods under the RCP8.5 shows frequent co-occurrence of cool days and nights, ice and frost days, and cool and frost days than RCP2.6 and RCP4.5. This study implies that the warm days, cool days, warmer nights, and cool nights are decreased with increased warming intensity, which shows the overall warming trend over the North Sikkim Himalaya, India. [ABSTRACT FROM AUTHOR]

Efficient use of transboundary rivers under climate change requires periodic adaptation of their governing regime to the hydrological realities of the basin. Applying a short-term time horizon to an agreement on water allocation can make it easier for the riparian states to update the terms of their cooperation periodically, and thus, adapt them to changes in water availability resulting from climate change. However, agreements with a pre-agreed termination date can only increase the efficiency of water use if they lead to a stable cooperation. In this paper, I analyze how riparian states’ previous knowledge of the termination date of a water allocation agreement affects the agreement’s stability. The results show that when riparian states are aware of the agreement’s termination date, there is a higher chance for them to free-ride. However, certain cases may occur in which previous knowledge of the agreement’s termination date can contribute to the stability of an agreement by enforcing compliance. [ABSTRACT FROM AUTHOR]

We assessed stream ecosystem-level response to a drought-induced defoliation event by gypsy moth caterpillars (Lymantria dispar) with high-frequency water quality sensors. The defoliation event was compared to the prior year of data. Based on long-term records of precipitation and drought indices, the drought of 2015-2016 in Rhode Island, USA was an extreme climatic event that preceded and likely precipitated the defoliation from insect infestation. Canopy cover in the riparian area was reduced by over 50% increasing light availability which warmed the stream and stimulated autotrophic activity. Frass and leaf detritus contributed particulate carbon and organic nutrients to the stream. Based on locally calibrated s::can spectro::lyser data, nitrate concentration and flux did not significantly increase during defoliation while orthophosphate concentration and flux did significantly increase during part of the defoliation period. Lower mean daily dissolved oxygen (DO) levels and wider diel cycles of DO indicated higher biological activity during the defoliation event. Stream metabolism metrics were also significantly higher during defoliation and pointed to heterotrophic activity dominating in the stream. The increases in stream metabolism were low compared to other studies; in streams with higher nutrient levels (e.g., in agricultural or urban watersheds) the increase in light and temperature could have a stronger influence on stream metabolism. The in-stream metabolic processes and nutrient fluxes observed in response to the drought-driven defoliation event resulted from the long-term deployment of high-frequency water sensors. The proliferation of these water sensors now enable studies that assess ecosystem responses to stochastic, unusual disturbances. [ABSTRACT FROM AUTHOR]

Climate change analysis includes the study of several types of variables such as temperature, precipitation, carbon emission, and streamflow. In this study, we focus on basin hydrology and, in particular, on streamflow values. They are geographic and climatologic indicators utilized in the study of basins. We analyze these values to better understand monthly and seasonal change over a 40-year period for all basins in Turkey. Our study differs from others by applying multivariate analysis into the streamflow data implementations rather than on trend, frequency, and/or distribution-based analysis. The characteristics of basins and climate change effects are visualized and examined with monthly data by using cluster analysis, multidimensional scaling, and gCLUTO (graphical Clustering Toolkit). As a result, we classify months as low-flow and high-flow periods. Multidimensional scaling proves that there is a clockwise movement of months from one decade to the next, which is the indicator of seasonal shift. Finally, the gCLUTO tool is utilized in a novel way in the hydrology field by revealing the seasonal change and visualizing the current changing structure of streamflow. [ABSTRACT FROM AUTHOR]

In a changing climate, Arctic streams are expected to show more influence from snowmelt, rainfall and groundwater, and less domination from glacial meltwater sources. Snowmelt streams are characteristic features of Arctic ecosystems, yet our current understanding of longitudinal patterns in benthic macroinvertebrate assemblages in these systems is limited when compared to glacier-fed systems. This study characterised longitudinal patterns of macroinvertebrate communities in snowmelt streams in northeast Greenland to provide novel insights into Arctic stream communities as dominant water sources shift with climate change. Benthic macroinvertebrates and environmental variables were sampled at three sites along five streams. Taxa diversity, evenness and abundance were expected to increase with distance from the stream source due to enhanced channel stability and warmer water temperature. This expectation for diversity and evenness was found in two streams, but abundance was up to ten times higher at the upstream sites compared to downstream, where biofilm biomass and ionic load were also highest. Here communities were largely dominated by the genus Eukiefferiella (Chironomidae). In the other three streams, no clear pattern in longitudinal macroinvertebrate community composition was evident due to low channel stability along the entire stream length. This study highlights the considerable variation in macroinvertebrate zonal distribution between snowmelt streams in northeast Greenland. A change towards more snowmelt-dominated streams in the Arctic could lead to shifts in the longitudinal organisation of macroinvertebrate community assemblages and the dominant species as a function of channel stability characteristics. [ABSTRACT FROM AUTHOR]

In many mountainous areas of the world, glaciers serve as a source of fresh water that is of critical importance and contributes to the sustainability of agriculture and other socio-economic activities. An enhanced understanding of socio-economic consequences of the climate-related glacier changes is essential to the identification of vulnerable entities and the development of well-targeted environmental adaptation policies. A questionnaire and interviews of farmers in the Heihe River Basin were used to analyze their perception of cryospheric changes, attitudes towards mitigation of cryospheric changes, and the ways in which they perceived their responsibility. Preferred responses and interventions for cryospheric change and views on responsible parties were also collected and evaluated. Our investigation revealed that most rural residents were concerned about glacier changes and believed they would bring harm to present society, individuals, and families, as well as to future generations. The respondents’ perceptions were mainly influenced by the mass media. Most respondents tended to favor adaptation measures implemented by the government and other policy-making departments. An integrated approach will be needed to deal with the challenges to tackling climate-related glacier change. [ABSTRACT FROM AUTHOR]

The objective of this work was the estimation of time-space hydraulic (water depth, flow velocity) and morphological (sediment transport and bank erosion) characteristics in the downstream part of a Mediterranean stream under current and future climatic conditions. The two-dimensional hydraulic model MIKE 21C was used, which has been developed specifically to simulate 2D flow and morphological changes in rivers. The model is based on an orthogonal curvilinear grid and comprises two parts: (a) the hydrodynamic part and (b) the morphological changes part. The curvilinear grid and the bathymetry file were generated using a very high-resolution DEM (1 m × 1 m). Time series discharge data from a hydrometric station introduced in the hydrodynamic part of the model. Regarding the morphological part of the model, field measurements of suspended sediment concentration and of bank erosion were used. The model was calibrated and verified using field data that were collected during high and low flow discharges. Model simulation was in good agreement with field observations as indicated by a variety of statistical measures. Next, for predicting the riverbank change, future meteorological data and river flow data for the next 10 years (2017-2027) were employed. These data series were created according to a lower and a higher emission climate change scenario. Based on the results, an increase in rainfall intensity may cause significant changes in river banks after 10 years (more than 5 m of soil loss in river meanders). Using the obtained simulation results, extreme hydrological events such as floods transporting large sediment loads and changes in river morphology can be monitored. The proposed methodology was applied to the downstream part of the Koiliaris River Basin in Crete, Greece. [ABSTRACT FROM AUTHOR]

A regional numerical physico-mathematical model of river runoff formation is used to study the possibility to assess long-term variations of water regime characteristics in the Amur R. in the XXI century. Two methods were used to specify climate projections as boundary conditions in the hydrological model: (1) based on the results of calculations with an ensemble of global climate models of CMI5 project, (2) based on data obtained by linear transformation of series of actual meteorological observations with the use of normal annual climate parameters calculated by climate models. The results of numerical experiments were used to analyze the sensitivity of the anomaly of Amur normal annual runoff to changes in the climate normals of air temperature and precipitation. The anomalies of normal annual runoff were shown to respond similarly (within the accuracy of sensitivity coefficient estimates) to changes in the appropriate climate normals, whatever the way of specifying climate projections. [ABSTRACT FROM AUTHOR]

In recent years, the natural hydrology behaviors were greatly influenced by climate change. The relation between runoff and climate change are always the core of scientific hydrological study in arid region. This paper presents a multi-variate time series controlled auto-regressive (CAR) model based on hydrological and climatic data of typical tributaries Jinghe River in Ebinur Lake Basin of Xinjiang covering the period from 1957 to 2012. The aim is to study the climate change and its effects on runoff of the Jinghe River, Northwest China. The results showed the following: the runoff of the Jinghe River was unevenly distributed and has obvious seasonal changes throughout the year. It was concentrated in summer and has along dry season with less runoff. The monthly maximum river runoff was from June to September and accounted for 74% of annual runoff. The river runoff increased since the 1980s till the 1990s; in the 21st century there was a trend of decreasing. The oscillatory period of annual runoff series in the Jinghe River Basin was 21a and 13a, and these periods were more obvious, followed by 32a and 9a. The oscillation with a time scale of 21a and 13a was a fulltimed domain. The MRE is 6.54%, the MAE is 0.84 × 108 m3, and the RMSE is 0.039. The CAR model passed the F-test and residual test, and the change trend of calculated and measured values of annual runoff is consistence, which means that the model was reasonable. [ABSTRACT FROM AUTHOR]

Estuaries are productive and ecologically important ecosystems, incorporating environmental drivers from watersheds, rivers, and the coastal ocean. Climate change has potential to modify the physical properties of estuaries, with impacts on resident organisms. However, projections from general circulation models (GCMs) are generally too coarse to resolve important estuarine processes. Here, we statistically downscaled near-surface air temperature and precipitation projections to the scale of the Chesapeake Bay watershed and estuary. These variables were linked to Susquehanna River streamflow using a water balance model and finally to spatially resolved Chesapeake Bay surface temperature and salinity using statistical model trees. The low computational cost of this approach allowed rapid assessment of projected changes from four GCMs spanning a range of potential futures under a high CO2 emission scenario, for four different downscaling methods. Choice of GCM contributed strongly to the spread in projections, but choice of downscaling method was also influential in the warmest models. Models projected a ~2–5.5 °C increase in surface water temperatures in the Chesapeake Bay by the end of the century. Projections of salinity were more uncertain and spatially complex. Models showing increases in winter-spring streamflow generated freshening in the Upper Bay and tributaries, while models with decreased streamflow produced salinity increases. Changes to the Chesapeake Bay environment have implications for fish and invertebrate habitats, as well as migration, spawning phenology, recruitment, and occurrence of pathogens. Our results underline a potentially expanded role of statistical downscaling to complement dynamical approaches in assessing climate change impacts in dynamically challenging estuaries. [ABSTRACT FROM AUTHOR]

Eurylophella iberica Keffermüller and Da Terra, 1978 is an endemic insect species of the Iberian Peninsula whose distribution has been poorly studied to date with rather old and scattered records. Here we compiled all existing distribution records and add new records from recent sampling activities. We also used this updated distributional information and environmental data (climate and geology) to estimate both current and future potential distributions in different climate change scenarios. We found that currently ca. 50% of the total Iberian region could present suitable environmental conditions for E. iberica (all the Iberian Peninsula, save the most eastern and Mediterranean areas). However, the potential distributions estimated when considering future climate change scenarios showed a marked reduction in the areas with suitable environmental conditions for the species, especially in the south. The northwest part of the Iberian Peninsula is a crucial zone for the future survival of this endemic species. We also found that most populations that occur in areas with suitable (both current and future) environmental conditions fall outside the Natura 2000 network of protected areas. Our results represent the first attempt to estimate the potential distribution of this endemic species providing important insights for its conservation. [ABSTRACT FROM AUTHOR]

The risk and predictability of weather and climate anomalies in Russian regions associated with differen types of El Niño are estimated using long-term data (1891-2015) on surface air temperature, precipitation, and indices of drought and excessive moisture. The probability of anomalies of these parameters in spring and summer months is estimated for different phase transitions of El Niño events. [ABSTRACT FROM AUTHOR]

In large part driven by total maximum daily load (TMDL) mandates, the restoration community in the Chesapeake Bay region has been implementing novel best management practices (BMPs) and stream restoration designs in urban areas, such as regenerative stream/stormwater conveyance (RSC) structures and stream-wetland complexes (SWCs). However, the nutrient and sediment reduction efficiencies of these novel designs are virtually unknown, and the possibility of increasing riverine flow in the Chesapeake Bay watershed associated with climate change this century necessitates an evaluation of their performance to develop and utilize those that optimize reductions in nutrient and sediment fluxes. We compare pre- and post-construction loads (total nitrogen (TN), total phosphorus (TP), and total suspended solids (TSS)) from RSCs (i.e., upland BMPs) and a SWC (i.e., stream restoration) constructed at the outflow of a highly developed watershed in the Coastal Plain physiographic province of Maryland. The largest of the two RSCs performed best in relation to expected nutrient and sediment reductions because of superior water retention capability. By the length of river reach restored, the SWC attained from 79 to 88% of its N reduction TMDL goal, but only 19 to 23 and 2.7 to 3.1% for TP and TSS, respectively; by watershed area, % attainments of TMDL goals were much lower. Results indicate that SWCs have the potential to curtail N loading from developed catchments, but additional water quality benefits may be limited. Climate change projections indicate that there will be an increased frequency of larger-volume storms that will result in an increase in stormflow runoff from urban areas, and increased pollutant loads will likely curtail potential gains made by efforts to achieve TMDL goals. Given the large-scale implementation of BMPs currently underway to accommodate the Chesapeake Bay TMDL, the restoration community needs to adopt a concerted strategy of building climate resilience into many types of urban BMPs to help attain and maintain loads at TMDL levels in anticipation of a progressively wetter climate throughout this century. [ABSTRACT FROM AUTHOR]

A disturbance or natural event in forested streams that alter available light can have potential consequences for nutrient dynamics and primary producers in streams. In this study, we address how functional processes (primary production and nutrient uptake) in stream ecosystems respond to changes in forest canopy structure. We focus on differences in incoming irradiance, nutrient uptake (NO, NH, and PO) and open-channel metabolism seasonally in 13 forested streams that drain forests with different canopy structures (10 to >300 years old) in the northeastern United States. Light irradiance was related to forest age in a U-shaped pattern, with light being the greatest in both young open forests (<50 years old) and older growth forests (>245 years old), whereas the darkest conditions were found in the secondary growth middle-aged forests (80-158 years old). Streams that had adjacent open or old-growth riparian forest had similar conditions with greater standing stock biofilm biomass (chl a), and elevated ER in October compared to streams with middle-aged riparian forests. Compared to all sites, streams with old-growth riparian forest had the greatest in-stream primary production rates (GPP) and elevated background nutrient concentrations, and to a lesser degree, increased nutrient retention and uptake ( V ). Streams draining older forests tended to be more productive and retentive than middle-aged forests, likely due to increased light availability and the age and structure of surrounding forest canopies. Middle-aged forests had the least variation in response variables compared to streams in young and old-growth riparian forests, likely a result of uniform canopy conditions. As the structure of widespread middle-aged forests in NE US is altered by loss of specific tree species, climate change, and/or human activity, it will impact in-stream production and nutrient dynamics and may ultimately alter nutrient loading in downstream catchments. [ABSTRACT FROM AUTHOR]

In this study, HSPF (Hydrologic Simulation Program-FORTRAN) was used to analyze the potential impact of climate change on the streamflow of four major river basins in Ethiopia: Awash, Baro, Genale, and Tekeze. The calibrated and validated HSPF model was forced with daily climate data of 10 CMIP5 (Coupled Model Intercomparison Project phase 5) Global Climate Models (GCMs) for the 1971-2000 control period and the RCP4.5 and RCP8.5 climate projections of 2041-2070 (2050s) and 2071-2100 (2080s). The ensemble median of these 10 GCMs projects the temperature in the four study areas to increase by about 2.3 °C (3.3 °C) in 2050s (2080s), whereas the mean annual precipitation is projected to increase by about 6% (9%) in 2050s (2080s). This results in about 3% (6%) increase in the projected annual streamflow in Awash, Baro, and Tekeze rivers whereas the annual streamflow of Genale river is projected to increase by about 18% (33%) in the 2050s (2080s). However, such projected increase in the mean annual streamflow due to increasing precipitation over Ethiopia contradicts the decreasing trends in mean annual precipitation observed in recent decades. Regional climate models of high resolutions could provide more realistic climate projections for Ethiopia's complex topography, thus reducing the uncertainties in future streamflow projections. [ABSTRACT FROM AUTHOR]