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The growing population and expansion of rural activities, along with changing climatic patterns and the need for water during drought periods, have led to a rise in the water demand worldwide. As a result, the construction of water storage structures such as dams has increased in recent years to meet the water needs. However, dam construction can bring significant alterations to the natural flow regime of rivers, and it is therefore essential to understand the potential effects of human structures on the hydrological regime of rivers to reduce their destructive impacts. This study analyzes the hydrological changes in the Shahrchai River in response to the Shahrchai Dam construction in Urmia, Iran. The study period was from 1950 to 2017 at the Urmia Band station. The Indicators of Hydrological Alteration (IHA) were used to analyze the hydrological changes before and after regulating, accounting for land use changes and climatic factors. The results revealed the adverse effects of the Shahrchai Dam on the hydrological indices. The analysis showed an increase in the average flow rate during the summer season and a decrease in other seasons. However, the combined effects of water transferring for drinking purposes, a decrease in permanent snow cover upstream of the dam, and an increase in water use for irrigation and agricultural purposes resulted in a decrease in the released river flow. Furthermore, the minimum and maximum daily flow rates decreased by approximately 85% and 65%, respectively, after the construction of the Shahrchai Dam. Additionally, the number of days with maximum flow rates increased from 117 days in the pre-dam period to 181 days in the post-dam period. As a concluding remark, the construction of the Shahrchai Dam, land use/cover changes, and a decrease in permanent snow cover had unfavorable effects on the hydrological regime of the river. Therefore, the hydrological indicators should be adjusted to an acceptable level compared to the natural state to preserve the river ecosystem. The findings of this study are expected to guide water resource managers in regulating the sustainable flow regime of permanent rivers.

The growing population and expansion of rural activities, along with changing climatic patterns and the need for water during drought periods, have led to a rise in the water demand worldwide. As a result, the construction of water storage structures such as dams has increased in recent years to meet the water needs. However, dam construction can bring significant alterations to the natural flow regime of rivers, and it is therefore essential to understand the potential effects of human structures on the hydrological regime of rivers to reduce their destructive impacts. This study analyzes the hydrological changes in the Shahrchai River in response to the Shahrchai Dam construction in Urmia, Iran. The study period was from 1950 to 2017 at the Urmia Band station. The Indicators of Hydrological Alteration (IHA) were used to analyze the hydrological changes before and after regulating, accounting for land use changes and climatic factors. The results revealed the adverse effects of the Shahrchai Dam on the hydrological indices. The analysis showed an increase in the average flow rate during the summer season and a decrease in other seasons. However, the combined effects of water transferring for drinking purposes, a decrease in permanent snow cover upstream of the dam, and an increase in water use for irrigation and agricultural purposes resulted in a decrease in the released river flow. Furthermore, the minimum and maximum daily flow rates decreased by approximately 85% and 65%, respectively, after the construction of the Shahrchai Dam. Additionally, the number of days with maximum flow rates increased from 117 days in the pre-dam period to 181 days in the post-dam period. As a concluding remark, the construction of the Shahrchai Dam, land use/cover changes, and a decrease in permanent snow cover had unfavorable effects on the hydrological regime of the river. Therefore, the hydrological indicators should be adjusted to an acceptable level compared to the natural state to preserve the river ecosystem. The findings of this study are expected to guide water resource managers in regulating the sustainable flow regime of permanent rivers. [ABSTRACT FROM AUTHOR]

Flow–duration curves (FDCs) provide a compact view of the historical variability of river flows, reflecting climate conditions and the main hydrologic features of river basins. The Surface Water and Ocean Topography (SWOT) satellite mission will enable the estimation of river flows globally, by sensing rivers wider than 100 m with a sampling recurrence from 3 to 21 days. This study investigated the lifetime mission potential for FDC estimation through the comparison between remotely-sensed and empirical FDCs. We employed the Global Runoff Data Center dataset and derived SWOT-like river flows by selecting gauging stations of rivers wider than 100 m with more than 10-year long daily river flow time series. Overall, 1200 gauged river cross-sections were examined. For each site, we created a set of 24 SWOT-simulated FDCs (i.e., based on different sampling recurrences, mean biases, and random errors) to be compared against their empirical counterparts through the Nash–Sutcliffe efficiency and the mean relative error. Our results show that climate and the sampling recurrence play a key role on the performance of SWOT-based FDCs. Tropical and temperate climates performed the best, whereas arid climates mostly revealed higher uncertainties, especially for high- and low-flows. [ABSTRACT FROM AUTHOR]

The increasing human needs and changes in climate patterns have led to the construction of water storage structures to meet the water demand in many regions worldwide, including Iran. Consequently, the hydrological regimes of rivers in various parts of Iran, due to human activities such as dam construction, have undergone alterations in recent decades. Understanding the effects of dams on river hydrological regimes is essential for river flow management and the preservation of river ecosystems. In this regard, the present study assesses the changes in the health of the Urmia's Shahrchai River flow during three periods: pre-dam construction, dam construction, and dam operation, from 1951 to 2017, through calculating different flow health related indices. The results indicate that the deviation of all hydrological health sub-indices in the post-dam construction period is higher than the pre-dam construction period. Moreover, the deviation of flow regime sub-indicators was predominantly low to moderate until 1998 and varied from low to very high after 1998. Additionally, the highest deviation of studied flow health-related indices occurred during the reference and dam operation periods for flood occurrence and minimum monthly flow, respectively, while during the dam construction period, it pertained to minimum monthly flow. Furthermore, the findings suggest that the hydrologic health of Shahrchai River flow decreased by approximately 16% and 45% during the dam construction/operation periods, respectively, compared to the reference period. The results of this study can be utilized in the understanding of flow alteration and the sustainable regulation of the Shahrchai River flow regime. [ABSTRACT FROM AUTHOR]

The objective of the present study was to investigate the temporal changes of the river flow pattern using Colwell Indices (CIs) in rivers originating from the Sabalan mountainous. The simultaneous hydro-climatic and river flow data were used to determine the distinct periods of flow regimes. Then the flow statistics and CIs (Predictability, Constancy, and Contingency) were calculated annually. The results reveal that the Max statistics had a decreasing trend in Lai, Nir, and Pole-Soltani river gauge stations with 75.7, 89.3, and 81.4%, respectively. The difference in Lane index values in Ahl-e-Iman, Lai, Nir, Pol-e-Soltani, and Viladragh river gauge stations was −38.00, 20.8, 16.1, −1.8, and −35.3%, respectively, which its variations attributed to the precipitation variable. The Zero-days index increased considerably in Ahle-Iman and Pole-Soltani river gauge stations with the amounts of 201 and 947%, respectively. According to the Constancy index, the monthly stability of the flow in Ahl-e-Iman and Pole-Soltani river gauge stations was lower than the other stations, and the Nir station had the highest flow stability. The value of the contingency index at Lai and Villadaragh stations was shallow, meaning the minimal probability of occurrence of monthly river flow. As a concluding remark, the hydrological regime and the river flow indices in studied rivers had altered under the influence of precipitation and temperature change. Different aspects of altered patterns of river flow regimes can be captured by the Colwell's indices in terms of predictability, constancy, and contingency of in mountainous virgin rivers. Therefore, the proper management decisions should be taken in accordance with the change in the river flow regime, regarding maintaining river flow and the climate change impacts. [ABSTRACT FROM AUTHOR]

Flow–duration curves (FDCs) provide a compact view of the historical variability of river flows, reflecting climate conditions and the main hydrologic features of river basins. The Surface Water and Ocean Topography (SWOT) satellite mission will enable the estimation of river flows globally, by sensing rivers wider than 100 m with a sampling recurrence from 3 to 21 days. This study investigated the lifetime mission potential for FDC estimation through the comparison between remotely-sensed and empirical FDCs. We employed the Global Runoff Data Center dataset and derived SWOT-like river flows by selecting gauging stations of rivers wider than 100 m with more than 10-year long daily river flow time series. Overall, 1200 gauged river cross-sections were examined. For each site, we created a set of 24 SWOT-simulated FDCs (i.e., based on different sampling recurrences, mean biases, and random errors) to be compared against their empirical counterparts through the Nash–Sutcliffe efficiency and the mean relative error. Our results show that climate and the sampling recurrence play a key role on the performance of SWOT-based FDCs. Tropical and temperate climates performed the best, whereas arid climates mostly revealed higher uncertainties, especially for high- and low-flows.

Our study provides a retrospective evaluation of the perturbances of the opencast mining on the small river. Based on a standard 'before-after-control-impact' approach, we assess the impact of disturbances on aquatic ecosystems. For this purpose, we used IHA (Index of Hydrological Alteration) statistics to fully quantify the impact of open-pit mine on flow regimes of small-to-medium-size rivers. The analysis results in flow data captured in the 33 parameters of the range variability approach (RVA) and five ecological flow components (EFC). This approach helped us comprehensively evaluate the alteration in the flow regime in areas of open-pit mining on the example of the Noteć River, a typical lowland river. We conclude that the level integrated hydrologic alterations to this river under the influence of the groundwater depression cone and water from the mine dewatering are high, as assessed by the RVA and EFC methods. Specifically, this work uses the IHA framework to verify the necessity of including a specific group of indicators. Our analysis shows that for the post-impact period on the investigated river, the functioning of the river ecosystem was degraded. One of the EFC components completely disappeared at both water gauge stations. There were also profound hydrologic alterations, such as increased frequency or duration of “extreme low flows” at one station; at the second station, “high flow pulses” occurred more frequently. More than 65 % of the altered parameters in five IHA groups were modified drastically. In the river section affected by the groundwater depression cone, both the minimum and maximum flows decreased by 20 % to 55 %. In the section where water from the mine dewatering is fed in, the minimum flows changed by + 170 to + 230 %. The use of the IHA tool provides an opportunity for environmental flow restoration of water conditions in degraded post-mining areas.

This paper describes how uncontrolled and illegal mining of sand and gravel can affect surface water and groundwater regimes in places where there is a hydraulic connection between them, based on a case study of the Velika Morava River in Serbia. Also, a change in cross-profile geometry, as a result of anthropogenic and natural factors, hinders the preparation of this river for inclusion among Serbia's waterways. The Velika Morava River's navigability would enable the development of waterborne transportation for both merchant ships and vessels of the Serbian Armed Forces River Flotilla. Correlations between water levels at gauging stations, as well as correlations between groundwater levels and river water levels at gauging stations, are used to show the dependence of these parameters on the change in the river bed profile after sand and gravel mining at the locations near gauging stations. In addition, the homogeneity of time-series of average annual elevations and the variance of the water levels of the Velika Morava River, measured in gauging stations during different periods, are statistically analyzed. The deepening of the Velika Morava riverbed where it was indiscriminately excavated in the 1980s led to the disruption of the groundwater regime and the hydraulic connection with the river, which lowered the water table of the aquifer used for the public water supply, as well as causing a number of other negative consequences. [ABSTRACT FROM AUTHOR]

To assess the effects of seasonal irrigation subsidies from paddy fields, spatiotemporal changes in diets of detritus feeders including nereidid polychaetes Hediste diadroma and H. atoka (facultative suspension feeders) and Tylorrhynchus osawai (surface-deposit feeder) were examined in Idoura Lagoon, Sendai Bay, Japan, using carbon and nitrogen stable isotope ratios (d13C and d15N). d13C ratios of Hediste species were much lower near a freshwater input (St. IB; -25.6 to -18.2‰) than in a seaward area (St. IA; -17.9 to -14.3‰), highlighting the assimilation of river subsidies in river-affected habitats. A d13C-based isotopic mixing model showed that riverine phytoplankton and detrital matters became the major diet of Hediste species in August and December at St. IB (60 to 72%), which corresponded to the supply of irrigation drainage to the area. Contrastingly the contribution of microphytobenthos increased sharply in March at both stations (55 to 83%) because of benthic diatom blooms. These emphasize that the Hediste species can change their feeding modes (i.e., suspension- and deposit-feeding) depending on food availability in the habitat. In winter and/or spring, d13C of H. diadroma negatively correlated with their body size, suggesting size-dependent variation in food utilization. d13C ratios of the sympatric deposit-feeders and suspension-feeding bivalves were seasonally more stable, depending mainly on microphytobenthos and river derived materials, respectively. These suggest that a certain group of estuarine consumers including Hediste species act as significant links between terrestrial and estuarine food webs by incorporating riverine terrestrial subsidies to benthic secondary production in estuaries. [ABSTRACT FROM AUTHOR]

The objective of this study is to investigate the changes in the river flow regime under the influence of dam construction and climatic variability and disaggregate their individual effects. Daily discharge, temperature, and precipitation data were collected from Qaranqo River basin in East Azerbaijan (Iran) for the period of 1971–2017. To disaggregate the effects of climatic variability and dam construction, daily river discharge data after dam construction were simulated using an Artificial Neural Network (ANN). Then, with the use of Indicators of Hydrologic Alteration (IHA) and annual indexes, river flow regime changes were examined. Results showed that monthly flows in all months except for July, August, and September, decreased. Also, annual maximum flows (except for a maximum of 1 day) decreased and minimum flows (except for a minimum of 1 day) increased. The Julian dates of minimum and maximum flows had also preceded, in which both dam construction and climatic variability were influential. Both dam construction and climatic variability were equally effective for monthly flows, extreme flows, and Julian dates of extreme flows. However, dam construction played a greater role in the changes of high and low pulses, and fall and rise of flow hydrograph. The two indexes of relative and absolute ranges of variation of intra-annual parameters had decreased, while the non-uniformity coefficient, concentration degree, complete accommodation coefficient, and Richards-Baker index had increased, which were mainly affected by climatic variability. In the Environmental Flow Components (EFC) in the group of low monthly flows in most months, there was little difference between observed data and simulated data, which indicated the role of climatic variability in the river flow regime. By contrast, there was a significant difference in peak, duration, and time of large and small floods, which indicated the role of the dam construction in these components. Climate variability had the most role in changes of monthly low flows, extreme low flows, and high flows of river flow regime, while in small and large floods, the role of dam construction was significant. It can be concluded that the effect of climatic variability on flow regime in the Qaranqo River basin, was greater than the effect of dam construction. [ABSTRACT FROM AUTHOR]

The Master Recession Curve (MRC) is a crucial tool for evaluating, managing, and utilizing rivers, particularly under low-flow conditions. Analyzing changes in the MRC of river flow is useful for water resource planning, surface water utilization, and estimating and allocating environmental flow. This study utilized daily flow data from rivers in Ardabil province, Iran over a 48-year statistical period (1970–2015). The Visual Basic program was utilized to estimate the equations and coefficients of recession curves. The trends of the constant and slope coefficients of the MRC equations were determined using the Mann-Kendall test and linear regression. Higher constant coefficient values were attributed to main rivers with higher discharge (e.g., Borran, Mashiran, and Samian, having 17.98, 13.79, and 5.64 cms, respectively. The slope of the MRC in most of the rivers in the central part of the study area exhibited a decreasing trend (p-value<0.05), which attributed to climate change, alterations in precipitation patterns, reduced rainfall/snowmelt, and water abstraction leading to less water input during non-flood periods. Additionally, most rivers in different climatic regions and areas of the study region exhibited an increasing trend (p-value<0.05) in the MRC constants, indicating reduced groundwater recharge or increased groundwater abstraction, as a common issue in the Ardabil province. Moreover, human water use and reservoir regulation (Yamci, Sabalan, Saghezchi, Givi, and small regulating reservoirs) can influence river flow patterns during non-flood periods. The occurrence of droughts and intensified surface water use by farmers, as well as unauthorized extraction of water from wells, have exacerbated this trend. • MRC slope had decreasing trend in rivers of Ardabil due to climate change and water abstraction • Most rivers in Ardabil province show an increasing trend in MRC constant value (p < 0.05) • Human water use and reservoir regulation influence river flow patterns during non-flood periods • Droughts, surface water use, and unauthorized water extraction exacerbate trend of increasing MRC constant [ABSTRACT FROM AUTHOR]

Frequency and intensity of precipitation events can alter hydrological conditions of lotic systems and material inflow from the catchment. In this study, interannual changes in food web structure were investigated in a lake–swamp–river system in the semi-arid West Siberian forest-steppe region using carbon and nitrogen stable isotope ratios (δ13C and δ15N). The δ15N signatures of aquatic producers and consumers including zooplankton, benthic invertebrates, and fish sharply increased (up to 7.2‰ in range) in 2009 under high summer precipitation. This would reflect the inflow of 15N-rich nutrients accumulated in the catchment through natural and anthropogenic activities, e.g., sewage, livestock farming, evaporation, and/or microbial denitrification. In 2010, benthic producers including epiphytes and macrophytes were more 13C-enriched, which is likely due to limited supply of dissolved inorganic carbon (DIC) under water stagnation, leading to a large isotopic fractionation during photosynthesis. However, 13C-enrichments in the benthic producers were not reflected to those of aquatic consumers in the habitat. Interannual changes in δ13C of particulate organic matter (POM; a proxy of phytoplankton) were reflected to those of zooplankton, benthic invertebrates, and fish fry, suggesting the trophic importance of autochthonous phytoplankton in the system. These findings suggest that occasional precipitation events in semi-arid forest-steppe regions can modify nutrient flux from the catchment, leading to changes in δ15N baseline in the lotic food web. [ABSTRACT FROM AUTHOR]

The Vietnamese Mekong Delta (VMD) is one of the world's most vulnerable deltas to climate change and sea level rise. Adequate understandings of future hydrological changes are crucial for effective water management and risk-proofing, however, this knowledge body is currently very limited. This study quantifies the responses of the VMD's river flow regime to multiple stimuli, namely future upstream inflow variation, local climate change, and sea level rise. The one-dimensional hydrodynamic model MIKE 11 was used to simulate discharges and water levels across the delta. We developed four scenarios to represent changes in the upstream discharges, precipitation changes and sea level rise, covering the 2036–2065 period. We downscaled climate data and applied three bias-correction methods for five General Circulation Models (GCM), and two Representative Concentration Pathways (RCPs). The climate change projections show similar trends of increasing wet season precipitation and decreasing dry season precipitation. However, cross-scenario variations are sometimes large, depending on the individual GCMs, the RCPs and specific locations. The hydraulic simulation results indicate that, under discharge changes between −20% and +10%, combined with in-delta precipitation variations during the dry season, river discharges at the four representative stations could reduce substantially from −2.5% to −100.2%. During the wet season, the calculated river discharges show increase between 7.3% and 46.7% under four considered scenarios. Substantial changes in the VMD's river flow regime could have potentially serious implications for water management, especially saltwater intrusion, and therefore calling for timely adaptation measures. [ABSTRACT FROM AUTHOR]

[Display omitted] • Mining activities drastically change the flow regime of medium and small low rivers. • In the period during mine operation (post-impact), two of the environmental flow components (EFCs) disappeared. • The monthly average flow of rivers flowing through the depression cone is below the lower limit of the RVA. • Feeding the riverbed with mine drainage water eliminates the "high and low pulses" characteristic of it. Our study provides a retrospective evaluation of the perturbances of the opencast mining on the small river. Based on a standard 'before-after-control-impact' approach, we assess the impact of disturbances on aquatic ecosystems. For this purpose, we used IHA (Index of Hydrological Alteration) statistics to fully quantify the impact of open-pit mine on flow regimes of small-to-medium-size rivers. The analysis results in flow data captured in the 33 parameters of the range variability approach (RVA) and five ecological flow components (EFC). This approach helped us comprehensively evaluate the alteration in the flow regime in areas of open-pit mining on the example of the Noteć River, a typical lowland river. We conclude that the level integrated hydrologic alterations to this river under the influence of the groundwater depression cone and water from the mine dewatering are high, as assessed by the RVA and EFC methods. Specifically, this work uses the IHA framework to verify the necessity of including a specific group of indicators. Our analysis shows that for the post-impact period on the investigated river, the functioning of the river ecosystem was degraded. One of the EFC components completely disappeared at both water gauge stations. There were also profound hydrologic alterations, such as increased frequency or duration of "extreme low flows" at one station; at the second station, "high flow pulses" occurred more frequently. More than 65 % of the altered parameters in five IHA groups were modified drastically. In the river section affected by the groundwater depression cone, both the minimum and maximum flows decreased by 20 % to 55 %. In the section where water from the mine dewatering is fed in, the minimum flows changed by + 170 to + 230 %. The use of the IHA tool provides an opportunity for environmental flow restoration of water conditions in degraded post-mining areas. [ABSTRACT FROM AUTHOR]

Water cycle research is the basis of any water management and one of most important elements is the runoff. In environmental analyzes the most commonly used is the annual specific runoff. Due to increasing environmental awareness the need for better seasonal runoff knowledge is crucial to support the decision making processes in order to improve the sustainable water resources management. The water quantity is crucial for all environmentally based water management. For water vulnerability analyzes the specific runoff can be taken into account as water sensitivity indicator. Since the runoff is varying in time and space the average annual runoff is not always enough, the substantial improvement can be achieved with the use of seasonal or monthly runoff. With the use of GIS we joined the results of two hydrological analyzes: water balance and river flow regimes. We used kriging to transform the point data of discharge coefficients in order to create continuous spatial distribution of the variable as a raster. To compute long-term average monthly specific runoff raster we used mathematical functions in GIS to combine the long-term specific runoff raster and the monthly discharge coefficients. The final results are 12 raster maps of monthly discharge coefficients and 12 maps of long-term monthly specific runoff. [ABSTRACT FROM AUTHOR]

A novel flow regime classification scheme was applied to 141 river basins across western Europe, providing more robust analysis of space-time variability in regimes and their driving hydroclimatological processes. Regime shape (timing) and magnitude (size) were classified to regionalise long-term average flow regimes and to quantify year-to-year variation in regimes for each basin. Six long-term regime shape regions identified differences in seasonality related to latitude and altitude. Five long-term magnitude regions were linked to location plus average annual rainfall. Spatial distribution of long-term regimes reflected dominant climate and runoff generation processes. Regions were used to structure analysis of (relative) inter-annual regime dynamics. Six shape and five magnitude inter-annual regimes were identified; and regime stability (switching) assessed at pan-European, regional and basin scales. In some years, certain regime types were more prevalent, but never totally dominant. Regime shape was more stable at higher altitude due to buffering by frozen water storage-release (cf. more variable rainfall-runoff at lower altitudes). The lower inter-annual magnitude regimes persisted across larger domains (cf. higher magnitude) due to the more widespread climatic conditions generating low flow. Notably, there was limited spatio-temporal correspondence between regime shape and magnitude, suggesting variations in one attribute cannot be used to infer the other. [ABSTRACT FROM AUTHOR]

Abstract: Hydrological regimes have an important influence on biodiversity, structure, and functioning of aquatic ecosystems. Unforeseen circumstances, both hydrologically and ecologically, caused by potential adoption and expansion of runoff harvesting innovations is of particular concern to water resource planners, as downstream river systems are likely to be adversely affected. This paper provides methods for determining the influence that large-scale adoption of runoff harvesting could have on downstream flow regimes by using a scenario-based approach, with the ACRU Agrohydrological model, to simulate the potential alteration of streamflow regimes due to runoff harvesting. Scenarios were based entirely on the spatial extent of impervious surfaces associated with rural homesteads, estimates of which were taken from current population data and used to establish the density of hypothetical runoff harvesting systems within a catchment setup. Daily streamflow simulation from nine Quaternary Catchments in the Thukela River basin provided suitable data series’ for analysis using the Indicators of Hydrological Alteration method to compute ecologically relevant hydrological parameters. The outcome of this ecohydrological study demonstrated that a relatively simple modelling exercise offers the potential to assess impacts that may arise from large-scale runoff harvesting. Results established that magnitudes of high and low flows of river flow regimes were most affected by runoff harvesting. Flow reduction was found to be most significant with low flows (up to 29%) in the case where the maximum runoff harvesting scenario was used. However, the majority of the IHA hydrological flow parameters revealed only slight impacts, even under circumstances where modelling scenarios were based on unrealistically high proportions of runoff harvesting. Increasing the spatial extent of runoff harvesting is thus expected to have a much greater impact at smaller spatial scales; water resources of small sub-catchments may become appreciably depleted where such catchments host excessive numbers of runoff harvesting systems. Therefore it is equally important to understand the more localised level of impacts of runoff harvesting on aquatic ecosystems, localised. [Copyright &y& Elsevier]

An approach for estimating mean monthly runoff at ungauged sites is presented. Special attention is paid to include effects of local features such as karst and river regulation by reservoirs. The developments introduced conform with hydrostochastic concepts in that simple physical and statistical laws are inherent in the methods used for mapping. Hence, the approach developed here is consistent with the water balance along the river network. The suggested method combines an application of empirical orthogonal functions and an adapted stochastic interpolation scheme to match the runoff data. The observation data are handled in the frame of a hydrological information system. This allows the display of results either in the form of the change in a statistical parameter along the river branches towards the basin outlet or as a map of the variation of the parameters across the basin or region space. The approach is demonstrated for France. [ABSTRACT FROM AUTHOR]

The article presents a study which evaluates the long-term effects of floods on a regulated river. With this, the authors hypothesized that sequential floods over time would cause a regime shift in the ecosystem. The floods resulted in little change in the physicochemistry of the river, although particulate organic carbon and particulate phosphorus were lower after the floods. They eliminated moss cover on bed sediments within the first year of flooding and maintained low periphyton biomass and benthic organic matter after the third year of flooding. Experimental floods are being implemented on regulated rivers throughout the world to improve their ecological integrity to simulate the natural flow regime.

Hydrograph recessions, usually described through a power-law function of river flows, are among the most widely utilized hydrological signatures. Whereas theories explaining the genesis of recession exponents have been recently developed, ongoing discussions on the physical meaning and suitable proxies of recession coefficients suggest their linkage to soil moisture states of whole river basins. This work investigates the possibility to explain hydrograph recession coefficients by means of satellite-derived soil moisture products such as the Soil Water Index of Copernicus Global Land Service. Analyses of basin-averaged Soil Water Index, computed for eleven river basins from the Central and Eastern United States with varied climates and landscapes, reveal the existence of an inverse relation between mean soil moisture and its variability in time, and provide a glance into the variability of river flows. A visible signature of satellite-derived soil moisture conditions on the values of the recession coefficient as well emerges when statistics of the Soil Water Index are paired with recession properties obtained by means of hydrograph recession analysis. In particular, drier river basins characterized by larger soil moisture variability tend to exhibit larger and more variable recession coefficients. These results suggest reliability of existing conjectures about the role of soil moisture for determining recession properties, and indicate that satellite-derived products can inform understanding of the intrinsic variability of the hydrologic response in river basins. Unlabelled Image • The hypothesized influence of soil moisture on recession hydrograph is investigated. • Potential of satellite products to shed light on hydrological features is examined. • Satellite-derived Soil Water Index ranks river flows according to their variability. • Drier river basins with more variable SWI tend toward larger recession coefficients. • Remotely sensed soil moisture informs knowledge of hydrologic response variability. [ABSTRACT FROM AUTHOR]