Search Results (42)

This study presents a comprehensive analysis of hydrological alterations and environmental flow components in the Beht River basin in northwest Morocco, using a coupled approach involving the Soil and Water Assessment Tool (SWAT) for hydrological modeling, the Indicators of Hydrologic Alteration (IHA) for flow regime assessment, and the Standardized Precipitation Index (SPI) for drought characterization. The SWAT model, run on a daily time step, showed satisfactory performance in terms of statistical criteria for both calibration and validation periods, despite encountering limitations, and proved its ability to simulate and reproduce the hydrological behavior of the basin. Using the IHA, we investigated changes in the hydrological regime over two distinct periods, revealing significant hydrological alteration. The SPI analysis supported these findings by highlighting the variable impacts of dry and wet periods on the hydrological regime, thus validating the observed changes in river flow indicators. As a preliminary step toward establishing environmental flows in the Beht River, this study provides foundational insights into the temporal evolution of its hydrology. These findings offer a valuable basis for better water resource management and conservation in the region. Full article

Understanding and analyzing low river flows are some of key tasks of effective water management, particularly in Chile’s Mediterranean regions, where irregular rainfall distribution leads to drought and water scarcity. This study aims to assess low-flow trends in the four major Chilean river basins (Maipo, Rapel, Maule, and Biobío) by calculating three key hydrological indices: the mean annual minimum and maximum flows (MAM), the base flow index (BFI), and the standardized precipitation index (SPI), using data from 18 hydrometric stations. The indicators of hydrologic alteration (IHA) tool was applied to calculate the MAM and BFI to assess flow variability and groundwater contributions. The SPI was calculated to examine hydrological drought conditions and evaluate how these conditions affect river flow behavior, correlating reduced low river flows with precipitation trends at the beginning of the dry season. Statistical analysis was conducted through the ordinary least squares (OLS) test for normally distributed data, and non-parametric tests, including the Mann–Kendall test, as well as Sen’s slope estimation, for data not meeting normality requirements. The results, presented both analytically and graphically, reveal trends in river flow indices and variations across the river basins, identifying critical areas of reduced flow that may require enhanced water management strategies. Full article

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. Full article

A combination of annual peak water demand due to seasonal population spikes along with small and shallow aquifers has prompted an assessment of the region’s watersheds as operating at a net water deficit. This study uses the Soil and Water Assessment Tool (SWAT) to simulate historical drought conditions in the Chipuxet watershed in Rhode Island, USA. The calibrated and validated model uses the Soil Moisture Deficit Index (SMDI) and Evapotranspiration Deficit Index (ETDI) as well as an Indicators of Hydrological Alteration (IHA) calculation to determine the frequency and severity of historical droughts and to simulate climate change conditions developed through a downscaled climate model selection. The output data for the historical and climate change scenarios were analyzed for drought frequency and severity. Results indicate that water stress will increase in both low-emission (RCP4.5) and high-emission (RCP8.5) scenarios. Additionally, the SMDI and ETDI show that RCP8.5 climate scenarios will have more severe deficits. Finally, IHA data indicate that zero-flow days and low-flow durations increase under all climate scenarios. Full article

The complementary operation of hydropower and photovoltaic power, aimed at meeting real-time demand, has led to frequent adjustments in power generation, causing significant fluctuations in hydrological systems and adversely affecting fish reproduction. The traditional hydrological regime alteration assessment index is based on index of hydrologic alternation (IHA) and mostly focuses on annual and daily runoff alterations. This study proposes a new set of indicators considering the characteristics of subdaily hydrological regime alterations, including magnitude, rate of change, duration, frequency, and timing. Using the hourly outflow from Longyangxia, an analysis of indicator redundancy was conducted. The alteration of the indicators before and after hydropower and photovoltaic operation was then analyzed using the cumulative probability distribution curve. Additionally, a concentration index was introduced to analyze the variations in hydrological impacts during different months. The results show that the hydro–photovoltaic complementary operation changed the subdaily natural flow regime, significantly increasing the rate of flow increase or decrease and the duration, with most indexes increasing by more than 100% compared with the natural flow regime. Furthermore, the concentration values of the indexes for the hydro–photovoltaic complementary operation were less than 10, indicating a more significant impact on the subdaily flow regime throughout the year. This research provides crucial data for mitigating ecological impacts under multi-source complementary scheduling. Full article

Terraces play a crucial role in regulating the water cycle. The management and restoration of, and the conservation strategies and plans for basins rely heavily on the assessment of alterations in hydrological characteristics, whether natural or man-made, within these basin systems. This study centers on evaluating the impact of terraces on temporal variations in the hydrological regime within the Laixi River basin, within the context of climate variability. To achieve this, we employed a hydrological model and applied the Indicators of Hydrologic Alteration and Range of Variability Approach (IHA–RVA). The results show that, under the influence of terraces, the annual flow exhibited an overall decreasing trend. There was a noticeable decrease in streamflow from March to July, while from October to December, there was a clear upward trend, with increases ranging from 4.76% to 8.10% at the Guanshenxindi (GSXD) and Watershed outlet (WO) cross-sections. The indicators related to the minimum flow showed an overall increasing trend, whereas all indicators related to the maximum flow exhibited a clear decreasing trend. Both high and low flow pulse counts decreased, while high and low pulse durations increased overall. The overall trend of flow reversal counts also showed a decrease. All hydrological indicators exhibited low levels of alteration, with hydrologic alteration values lower than 33.33%. However, the influence of terraces on the upstream hydrological conditions was more pronounced than their downstream effect. The terraces in the study area have played a beneficial role in the flood regulation, drought mitigation, and water resource conservation of the Laixi River. They have contributed to stabilizing the daily average flow during high flow periods and have had a positive impact on the ecological base flow during low flow periods, thereby improving the aquatic ecological environment. This study provides theoretical support for river regulation within the framework of soil and water conservation measures. Full article

Human disturbance and climatic factors alter the hydrological state of rivers in many ways and have a degree of negative impact on the quality of watershed habitats; quantifying the impact of both human disturbance and climatic factors on hydrological change can help improve the quality of watershed habitats. Therefore, in this research, an integrated watershed assessment framework is proposed to analyse the watershed from four perspectives: hydrological situation, environmental flows, drivers, and habitat quality. A meteorological streamflow model based on the Long Short-Term Memory (LSTM) model was employed to analyse the hydrological evolution and quantify the influence of the drivers from the perspective of hydrological and environmental flows. The Integrated Valuation of Ecosystem Services and Tradeoffs (InVEST) model was then used to evaluate the spatial and temporal evolution of habitat quality in the basin. And, finally, the grey correlation theory was used to reveal the response of habitat quality to hydrological changes. Studies have shown that annual flow and precipitation are increasing in the Xiangjiang River (XJR) basin, while its annual potential evapotranspiration is decreasing significantly. After 1991, the hydrological conditions of the XJR were highly variable, with the combined rate of change of the most Ecologically Relevant Hydrological Indicators, ERHIs-IHA and ERHIs-EFCs, reaching 26.21% and 121.23%, respectively. Climate change and human disturbance are the main drivers of change for both (with contributions of 60% and 71%, respectively). Between 1990 and 2020, the habitat quality in the basin declined over time (from 0.770 to 0.757), with areas of high habitat value located mainly in mountainous areas and habitat degradation being concentrated in urban areas in the middle and lower reaches, gradually evolving towards areas of high habitat value in the periphery. There is a strong correlation between watershed habitat quality and the ERHIs. The results of the study can provide a scientific basis for maintaining regional ecological security and rational allocation of water resources. Full article

Identifying the mechanism through which changes in land use and land cover (LULC) modulate hydrological flows is vital for water resource planning and management. To examine the impact of LULC change on the hydrology of the Gaborone Dam catchment within the upper Limpopo basin, where Notwane river is the major river within the catchment, three LULC maps for the years 1997, 2008, and 2017 were established based on a mosaic of Landsat 5 for 1997 and 2008 and Landsat 8 for 2017. The 10 m-resolution Version 200 ESA World Land Cover Map for 2021 is used as a ground truth to train the random forest (RF) classifier to identify land cover classes from Landsat 8 imageries of 2021 using the Google Earth Engine (GEE) Python API. The overall accuracy/kappa coefficient of the RF classifier is 0.99/0.99 for the training and 0.73/0.68 for the validation data sets, which indicate excellent and substantial agreements with the ground truth, respectively. With this confidence in the LULC classification, the impact of LULC change on the hydrological flow within the catchment was estimated by employing the Soil and Water Assessment Tool (SWAT) and indicator of hydrological alteration (IHA). The SWAT model calibration and validation were first performed, and the ability of the model to capture the observed stream flow was found to be good. The LULC maps from Landsat images during the 1997–2017 period show a decrease in forests and shrubland in contrast to an increase in pasture land. The expansion of pasture and cropland and the reduction in forests and shrubland led to a decline in the amount of evapotranspiration and groundwater recharge. Furthermore, the LULC change also caused a reduction in low flow during dry periods and an increase in high flow during the rainy season. The findings clearly demonstrate that LULC changes can affect the water table by altering soil water recharge capacity. The study highlighted the importance of LULC for catchment water resource management through land use planning to regulate the water level in the Gaborone Dam against the impact of climate change and growing water demands by the city of Gaborone due to population growth. Full article

Hydrological conditions are key factors in the evaluation of water resources and ecosystems. The Yongding River Basin has many irrigated areas, and excessive agricultural water consumption has led to serious water shortages and ecosystem damage. To investigate the evolution of ecohydrological conditions and their driving factors in the Yongding River basin in a changing environment, this study combines indicators of hydrologic alteration with the range of variability approach (IHA-RVA) to identify the most ecologically relevant hydrological indicators (ERHIs) and to determine the periods of hydrological variability in the basin, using the Xiangshuipu section on the Yang River as the study area. By calculating the degree of hydrological alteration, the evolutionary pattern of ecohydrological conditions in the basin was analyzed, and the WetSpa model was used to quantitatively identify the contributions of climate change, reservoir storage, and irrigation water withdrawal to the alteration of hydrological conditions. The results showed that the rise and fall rate; maximum and minimum 1 day flows; dates of maximum flow; and July flows were the most ecologically relevant hydrological indicators for the Xiangshuipu section. Variability of this section occurred between 1982 and 1988; except for the annual maximum 1 day flows and fall rate, which underwent moderate changes; all other indicators exhibited small changes and the overall hydrological alteration of the Xiangshuipu section was low. The most influential change in the hydrological conditions was irrigation water withdrawal (from specific irrigation); followed by climate change and reservoir storage. The results of this study provide an important basis for water resources utilization and ecological management in the Yongding River basin. Full article

The Heilong-Amur river basin (HARB) is the largest transboundary river in Asia and is primarily located in its cold region. With global warming and geopolitical cooperation strengthening between Russia and China, the hydrology change and water security risks are receiving increasing attention. This study utilized the linear regression, Mann–Kendall, and cumulative anomaly methods to analyze changes observed in the upper HARB’s streamflow and water levels over 30 years. The collation of outcomes derived from the methods mentioned above, the indicators of the hydrological alterations process, and the range of variability approach method (IHA–RVA), coupled with results gleaned from the double cumulative curve method, facilitate a thorough evaluation of the perturbations in hydrologic indicators, as well as the impacts of anthropogenic activities. The results showed that the overall hydrological regimes of both streamflow and water levels at the Luoguhe (LGH), the Shangmachang (SMC), and the Kalunshan (KLS) displayed a mild decrease from 1988 to 2017. The streamflow decreased by 58%, 42%, and 38%, and water levels decreased by 48%, 53%, and 59%, respectively, at each station after the mutations. LGH station recorded the highest decrease rate in streamflow at 8.28 × 10⁸ m³/a, whereas the steepest rate of decline in water levels was observed at KLS station at 0.05 m/a. Despite the decreasing trend in the high pulse count of streamflow across the three stations, a slight increase in the high pulse duration of streamflow was noted at SMC and KLS. Precipitation changes were the primary driving force behind runoff alterations, contributing 62%, 84%, and 90% at LGH, SMC, and KLS, respectively, significantly higher than the contribution from anthropogenic activities (38%, 16%, and 10%, respectively). These findings also underscore the suitability of the methodologies employed in this study for application in cold regions. Full article

In this study, a comprehensive methodology was adapted to determine the environmental flow regime of “La Yerbabuena”, a temporary stream located in the Aguascalientes Valley, Mexico. The analysis was divided into four stages: the geomorphological watershed analysis, a hydrologic analysis, hydraulic modeling, and environmental analysis. The main geomorphological features of the study area were defined from maps in the spatial block, and with them, a synthetic series of daily and monthly discharge was determined and further used in the next stages. In the hydrological stage, the IHA (Indicators of Hydrologic Alteration) methodology and the procedures from the Mexican regulation, named NMX-159, were applied to the stream, and their results were comparatively analyzed. A similar interannual flow variation from both methodologies was found for wet and dry seasons, ranging from 0.010 to 0.108 m³/s. In the hydraulic modeling stage, a micro-basin part of the stream was modeled in the software HEC RAS, observing that the IHA methodology results had water levels that matched the baseflow of the stream, which allows understanding the hydraulic behavior of the water flow through the generation of different profiles in function of the rainy season. Finally, for the environmental stage, the hydrological health of the stream was evaluated using the software Flow Health, additionally observing that the IHA methodology was closer to the desired water level of the reference. This study demonstrates that the proposed methodology achieves the objectives defined by the NMX-159, which establishes a streamflow regime considering a natural interval of hydrologic variability in both ordinary and after-disturbance conditions. This application of the methodology for temporary streams provides an understanding of the hydrological behavior of the environmental flow throughout the year, and regarding the existing regulations, it presents a correlation with the obtained results, as well as greater precision in the dry season. Full article

Hydrological regimes influence an aquatic ecosystem’s biotic composition, structure, and functioning. But construction of dams or anthropogenic activities substantially alter the hydrologic regimes. In this study, we used a method named as the “Indicators of Hydrologic Alteration” to examine the degree of hydrologic alteration at seven flow gauge stations in the Mangla watershed. The assessment of alteration is carried out according to the Range of Variability (RVA). This method relies on analyzing hydrologic data obtained from existing measurement points (e.g., stream gauges) within an ecosystem or model-generated data. We used 33 parameters categorized into 5 groups based on magnitude, duration, frequency, timing, and rate of change to characterize hydrologic variation within a year statistically. We then examine the hydrologic perturbations by comparing the measure of central tendency and dispersion for each parameter between the “pre-impact (1967–1994)” and “post-impact (1995–2014)” periods. The results show that within the Mangla watershed, the high alteration was noted in the magnitude of monthly flows and extreme flows at Azad Pattan, Gari Habibullah, Palote and at Muzafarabad stations. The flow at Domel and Kohala stations are found in low hydrological alteration among all groups of indicators. The study indicates that Neelum Basin at Muzaffarabad has significantly high alteration with maximum negative values. On the other hand, a high frequency of alteration observed in the monthly flows and extreme water conditions. Overall, a moderate alteration is observed in the whole watershed, which may produce adverse effects on the aquatic ecosystem of the Mangla watershed. Full article

Land use/land cover (LULC) and climate change are the two major environmental factors that affect water resource planning and management at different scales. This study aims to investigate the effects of LULC and climate change patterns for a better understanding of the hydrological processes of the Birr River watershed. To examine the effects of LULC and climate change patterns on hydrology, three periods of climate data (1986–1996, 1997–2007 and 2008–2018) and three sets of LULC maps (1986, 2001 and 2018) were established. The changes in hydrological flow caused by climate and LULC changes were estimated using the soil and water assessment tool (SWAT) and indicator of hydrological alteration (IHA) method. Results showed that the SWAT model performed well during the calibration and validation period at monthly timestep, with R² and NSE values of (0.83 and 0.81) and (0.80 and 0.71), respectively. The LULC change increased surface runoff while decreasing baseflow, water yield, and evapotranspiration. This was due to increased agriculture and settlements, and a reduction in bushland, forest, and grassland. Climate change increased surface runoff and water yield while decreasing baseflow and evapotranspiration during 1996–2006. The combined effect of LULC and climate reveals increased surface runoff and a decreased trend of evapotranspiration, whereas baseflow and water yield showed inconsistency. In addition, the IHA found no statistically significant increasing trend for one-day, three-days, seven-day, and thirty-day minimum and maximum daily streamflow in the Birr River watershed. These findings will be useful to authorities, water engineers, and managers concerned with hydrology, LULC, and climate. Full article

Rainfall is one of the dominating climatic parameters that affect water availability. Trend analysis is of paramount significance to understand the behavior of hydrological and climatic variables over a long timescale. The main aim of the present study was to identify trends and analyze existing linkages between rainfall and streamflow in the Nilwala River Basin (NRB) of Southern Sri Lanka. An investigation of the trends, detection of change points and streamflow alteration, and linkage between rainfall and streamflow were carried out using the Mann–Kendall test, Sen’s slope test, Pettitt’s test, indicators of hydrological alteration (IHA), and Pearson’s correlation test. Selected rainfall-related extreme climatic indices, namely, CDD, CWD, PRCPTOT, R25, and Rx5, were calculated using the RClimdex software. Trend analysis of rainfall data and extreme rainfall indices demonstrated few statistically significant trends at the monthly, seasonal, and annual scales, while streamflow data showed non-significant trends, except for December. Pettitt’s test showed that Dampahala had a higher number of statistically significant change points among the six rainfall stations. The Pearson coefficient correlation showed a strong-to–very-strong positive relationship between rainfall and streamflow. Generally, both rainfall and streamflow showed non-significant trend patterns in the NRB, suggesting that rainfall had a higher impact on streamflow patterns in the basin. The historical trends of extreme climatic indices suggested that the NRB did not experience extreme climates. The results of the present study will provide valuable information for water resource planning, flood and disaster mitigation, agricultural operations planning, and hydropower generation in the NRB. Full article

This study investigated hydrological alterations in the sections of the Mura, Drava, and Danube rivers, which together form a unique river landscape proclaimed by UNESCO as the Transboundary Biosphere Reserve Mura, Drava, and Danube (TBR MDD). A coherent network of 12 major protected areas along the rivers highlights their ecological value, which could be endangered by climate change and consequent environmental changes. Statistical analyses, such as the homogeneity test, Mann–Kendall trend test of monthly and seasonal discharges, and empirical probabilities of daily discharges, were applied to discharge data series (1960–2019) from six hydrological stations prior to the calculation of indicators of hydrologic alteration (IHA). This method could be a helpful tool for recognizing the changes in hydrological regimes that can affect river ecosystems. The 33 indicators were organized into five groups. The results showed a decrease in low pulse duration and increase in rise/fall rates and the number of reversals. From an ecological perspective, the results obtained for the probabilities of long flooding periods were particularly significant. They drastically decreased for all three rivers on their stretches within the reserve. According to IHA modeling results, the river sections analyzed were moderately altered with global indicator values between 0.5 and 0.75. The most pronounced hydrological alterations were associated with the frequency and duration of low and high pulses and the rate and frequency of changes in water condition, which could have a significant impact on the ecological values of the TBR MDD. In addition, results show more pronounced climate impact versus human activities. Full article