River Basins Worldwide Research Articles

Flood Inundation Modeling by Integrating HEC–RAS and Satellite Imagery: A Case Study of the Indus River Basin

Floods are brutal, catastrophic natural hazards which affect most human beings in terms of economy and life loss, especially in the large river basins worldwide. The Indus River basin is considered as one of the world’s large river basins, comprising several major tributaries, and has experienced severe floods in its history. There is currently no proper early flood warning system for the Indus River which can help administrative authorities cope with such natural hazards. Hence, it is necessary to develop an early flood warning system by integrating a hydrodynamic model, in situ information, and satellite imagery. This study used Hydrologic Engineering Center–River Analysis System (HEC–RAS) to predict river dynamics under extreme flow events and inundation modeling. The calibration and validation of the HEC–RAS v5 model was performed for 2010 and 2015 flood events, respectively. Manning’s roughness coefficient (n) values were extracted using the land use information of the rivers and floodplains. Multiple combinations of n values were used and optimized in the simulation process for the rivers and floodplains. The Landsat 5 Thematic Mapper (TM), Landsat 8 Operational Land Imager (OLI), Moderate Resolution Imaging Spectroradiometer (MODIS) MOD09A1, and MOD09GA products were used in the analysis. The Normalized Difference Water Index (NDWI), Modified NDWI1 (MNDWI1), and MNDWI2, were applied for the delineation of water bodies, and the output of all indices were blended to produce standard flood maps for accurate assessment of the HEC–RAS-based simulated flood extent. The optimized n values for rivers and floodplains were 0.055 and 0.06, respectively, with significant satisfaction of statistical parameters, indicating good agreement between simulated and observed flood extents. The HEC–RAS v5 model integrated with satellite imagery can be further used for early flood warnings in the central part of the Indus River basin.

Improving surface water quality of the Yellow River Basin due to anthropogenic changes.

Understanding of how changes in diverse human activities and climate contribute to water quality dynamics is crucial for sustainable water environment management especially in the arid and semi-arid regions. This study conducted a comprehensive estimation of the surface water quality change in the Yellow River basin during 2003-2017 and its responses to varied pollution sources and water volumes under socioeconomic and environmental influences. Basin-wide measurements of chemical oxygen demand (COD), ammonium nitrogen (NH+4-N) and dissolved oxygen (DO) concentrations were used in trend detection. Annual anthropogenic (covering six sectors) and natural (sediment-induced, flow-in from the upstream and stored last year) pollution sources and water components (inflow, natural runoff, water consumption, reservoir storage and evaporation) were compiled for each sub-basin. Bottom-up hierarchical analysis was then performed to differentiate individual contributions. Results showed significant decreasing trends in COD and NH+4-N concentrations and increasing trends in DO concentrations. The middle reaches that traverse the Loess Plateau however remained severely polluted with 11.3-39.0% inferior to level III in 2017. The pollutant load played major positive contributions that gradually increased from upper to lower reaches. Declines in urban, rural and industrial pollution discharges following environmental investments and rural depopulation contributed the most: 78-96% for COD and 55-100% for NH+4-N. The total surface water volume had dilution effects in the upper and middle reaches (3-28%) and condensing effects in the lower reaches (2-37%). Precipitation and vegetation dynamics contributed slightly. The primary unfavorable factors were the growing agricultural pollution discharges and water consumption in the upper and middle reaches that also threatened the lower reaches. This study is expected to provide in-depth insights for the systematic response of regional water quality to combined human interventions and references for water quality management in other arid and semi-arid river basins worldwide.

Multi-Scenario Simulation of Land Use Changes with Ecosystem Service Value in the Yellow River Basin

Land use change plays a crucial role in global environmental change. Understanding the mode and land use change procedure is conducive to improving the quality of the global eco-environment and promoting the harmonized development of human–land relationships. Large river basins play an important role in areal socioeconomic development. The Yellow River Basin (YRB) is an important ecological protective screen, economic zone, and major grain producing area in China, which faces challenges with respect to ecological degradation and water and sediment management. Simulating the alterations in ecosystem service value (ESV) owing to land use change in the YRB under multiple scenarios is of great importance to guaranteeing the ecological security of the basin and improve the regional ESV. According to the land use data of 1990, 2000, 2010, and 2018, the alterations in the land use and ESV in the YRB over the past 30 years were calculated and analyzed on the basis of six land use types: cultivated land, forestland, grassland, water area, built-up land, and unused land. The patch-generating land use simulation (PLUS) model was used to simulate the land use change in the study area under three scenarios (natural development, cultivated land protection, and ecological protection in 2026); estimate the ESV under each scenario; and conduct a comparative analysis. We found that the land use area in the YRB changed significantly during the study period. The ESV of the YRB has slowly increased by ~USD 15 billion over the past 30 years. The ESV obtained under the ecological protection scenario is the highest. The simulation of the YRB’s future land use change, and comparison and analysis of the ESV under different scenarios, provide guidance and a scientific basis for promoting ecological conservation and high-quality development of river basins worldwide.

Common irrigation drivers of freshwater salinisation in river basins worldwide

Freshwater salinisation is a growing problem, yet cross-regional assessments of freshwater salinity status and the impact of agricultural and other sectoral uses are lacking. Here, we assess inland freshwater salinity patterns and evaluate its interactions with irrigation water use, across seven regional river basins (401 river sub-basins) around the world, using long-term (1980–2010) salinity observations. While a limited number of sub-basins show persistent salinity problems, many sub-basins temporarily exceeded safe irrigation water-use thresholds and 57% experience increasing salinisation trends. We further investigate the role of agricultural activities as drivers of salinisation and find common contributions of irrigation-specific activities (irrigation water withdrawals, return flows and irrigated area) in sub-basins of high salinity levels and increasing salinisation trends, compared to regions without salinity issues. Our results stress the need for considering these irrigation-specific drivers when developing management strategies and as a key human component in water quality modelling and assessment.

Spatiotemporal Coupling Coordination Analysis of Social Economy and Resource Environment of Central Cities in the Yellow River Basin

With the rapid economic and social development and accelerated urbanization, the negative ecological impact of major river basins worldwide has been deepening, which is gradually threatening the sustainable development of cities. This study establishes the model of the coupling coordination relationship between social economy and resources environment of nine central cities in the Yellow River Basin. Based on the evaluation index system of social economy and resource environment, we quantitatively measure the coupling coordination degree and spatiotemporal pattern of the nine central cities from 2010 to 2017. The obstacle factors of coupling coordination were then diagnosed based on the obstacle degree model. The results showed that (1) the social economy and resources environment development indices of the nine central cities in the Yellow River Basin, as well as the coupling coordination of each central city, showed an overall upward trend from 2010 to 2017. (2) Most of the central cities in the Yellow River Basin were in the coordinated coupling stage, among which Xining and Lanzhou have the highest coupling degree. (3) The obstacle factors affecting the harmonious development coupling coordination of the nine central cities were natural growth rate of population, proportion of tertiary industry in GDP and per capita investment in fixed assets in social economy system, and per capita green area of parks, per capita total amount of water resources, and per capita industrial SO2 emissions in resources environment system. It is necessary to adopt different strategies for different cities to promote the coupling coordination development of urban social economy and resources environment in the Yellow River Basin.

Coordination and control – limits in standard representations of multi-reservoir operations in hydrological modeling

Abstract. Major multi-reservoir cascades represent a primary mechanism for dealing with hydrologic variability and extremes within institutionally complex river basins worldwide. These coordinated management processes fundamentally reshape water balance dynamics. Yet, multi-reservoir coordination processes have been largely ignored in the increasingly sophisticated representations of reservoir operations within large-scale hydrological models. The aim of this paper is twofold, namely (i) to provide evidence that the common modeling practice of parameterizing each reservoir in a cascade independently from the others is a significant approximation and (ii) to demonstrate potential unintended consequences of this independence approximation when simulating the dynamics of hydrological extremes in complex reservoir cascades. We explore these questions using the Water Balance Model, which features detailed representations of the human infrastructure coupled to the natural processes that shape water balance dynamics. It is applied to the Upper Snake River basin in the western US and its heavily regulated multi-reservoir cascade. We employ a time-varying sensitivity analysis that utilizes the method of Morris factor screening to explicitly track how the dominant release rule parameters evolve both along the cascade and in time according to seasonal high- and low-flow events. This enables us to address aim (i) by demonstrating how the progressive and cumulative dominance of upstream releases significantly dampens the ability of downstream reservoir rules' parameters to influence flow conditions. We address aim (ii) by comparing simulation results with observed reservoir operations during critical low-flow and high-flow events in the basin. Our time-varying parameter sensitivity analysis with the method of Morris clarifies how independent single-reservoir parameterizations and their tacit assumption of independence leads to reservoir release behaviors that generate artificial water shortages and flooding, whereas the observed coordinated cascade operations avoided these outcomes for the same events. To further explore the role of (non-)coordination in the large deviations from the observed operations, we use an offline multi-reservoir water balance model in which adding basic coordination mechanisms drawn from the observed emergency operations is sufficient to correct the deficiencies of the independently parameterized reservoir rules from the hydrological model. These results demonstrate the importance of understanding the state–space context in which reservoir releases occur and where operational coordination plays a crucial role in avoiding or mitigating water-related extremes. Understanding how major infrastructure is coordinated and controlled in major river basins is essential for properly assessing future flood and drought hazards in a changing world.

Observation‐Constrained Projection of Global Flood Magnitudes With Anthropogenic Warming

AbstractRiver flooding is among the costliest natural disasters with severe economic, societal, and environmental consequences. However, substantial uncertainties remain in global and regional projections of future flood conditions simulated by global climate models (GCMs) and/or global hydrological models (GHMs). Using physical models coupled with machine learning (ML), for the first time, we project changes in flood magnitudes of 2062 global river basins by constraining physical‐based streamflow simulations with observations under 1.5°C and 2°C warming scenarios identified for the Representative Concentration Pathway 8.5. We found that, during the validation period, the GHMs‐simulated flood magnitudes would improve with reduced uncertainty over the selected river basins after ML with a Long Short‐Term Memory network. Our estimation suggested that flood magnitudes would increase in many Northern Hemisphere mid‐ and high‐latitude rivers (e.g., Lena River, Amur River and Volga River) but decrease in some river basins in southern Finland and Eastern Europe in future periods (i.e., 1.5°C and 2°C warming levels). In 1.5°C and 2°C warmer worlds, the decreasing flood magnitudes in most South American rivers are associated with decreased soil moisture and increased evapotranspiration induced by warmer temperatures. Although the geographical pattern of changes in flood magnitudes for the +2°C experiment is close to that of the +1.5°C experiment, a 1.5°C warming target is more likely to reduce flood magnitudes of many river basins worldwide (e.g., in central and eastern Siberia, Alaska/Northwest Canada and South America).

Quantifying the climate and human impacts on the hydrology of the Yalong River Basin using two approaches

AbstractRunoff in many river basins worldwide has shown an alteration under the impact of global climate change and increasing human activities. A detailed quantitative and qualitative analysis on the impact of climate change and human activities is therefore of great significance towards the sustainable water resources planning and management. In this study, the impact of climate change and human activities on the runoff was first quantitatively analyzed for the Yalong River Basin (YRB), China, by using a combination of the CREST hydrologic model and the Choudhury–Yang equation based elastic coefficient method, respectively. Furthermore, a qualitative analysis on the response of runoff to human activities was carried out in terms of land use changes, water withdrawal and reservoir operation. Results indicate that precipitation and runoff of the Yalong River Basin increased and decreased at the rate of 1.17 and 0.35 mm/a, respectively, for the period from 1980 to 2018. Climate change and human activities contributed 6.65–21.67% and 78.33–93.35% to the runoff variation, respectively. Among the human activities, we found that reservoir construction and operation is likely to be the major driver of the variation in the hydrologic regime of the YRB. Our methods and findings are expected to provide implications for water resources planning and management for the YRB and different basins across the globe.

A global analysis of the susceptibility of river basins to invasion of a freshwater zooplankton (Daphnia lumholtzi)

Abstract Climate change and species invasions pose serious threats to biodiversity. Daphnia lumholtzi Sars, 1885, a cladoceran species native to Africa, Asia, and Oceania, has successfully invaded large sections of North and South America, there is evidence that the increase in the Earth's temperature and the number of reservoirs have facilitated this process. In this context, our study evaluated the effects of climate change on the invasive potential of D. lumholtzi, identifying the environmental suitability of non‐native river basins around the world to invasion by this species. Using ecological niche modelling, we predicted potential distribution areas of D. lumholtzi in non‐native continents at the present time, in 2050 and 2080. For future scenarios we considered two hypotheses of greenhouse gas emission: extreme (8.5 representative concentration pathways) and moderate (4.5 representative concentration pathways). We used different algorithms in niche models within the ensemble forecast approach to estimate the potential distribution of D. lumholtzi river basins worldwide. Furthermore, we developed a susceptibility index, that uses the presence of D. lumholtzi, its suitability information, area, and number of reservoirs to evaluate the susceptibility to invasion for each river basin. Our predictions showed that future climate change will have a strong influence on the invasive potential of D. lumholzti, potentially expanding its distribution in eastern North America and boosting invasion across Europe, especially at the end of the century. The susceptibility index also showed that many river basins that presently are not vulnerable to invasion by this species will become susceptible to invasion, these basins lie mainly in Europe. Our results will be useful for monitoring and mitigating the spread of this species, especially for river basins identified as highly susceptible to invasion. Thus, we suggested that D. lumholtzi should be a high priority for monitoring and preventive actions against invasion of these river basins. We also suggest that better risk assessments, that include invasive species and reservoirs, should be a priority in national energy development plans.

Water scarcity-risk assessment in data-scarce river basins under decadal climate change using a hydrological modelling approach

Basin-scale water scarcity, an adverse consequence of the imbalance between the available fresh water and water demands, is an alarming situation in many countries worldwide. This necessitates for analyzing the risk of water scarcity forced with the changing climate, land-use alterations, growing population, and industrialization to pave a way for sustainable water resources systems planning and management. This study advocates a hydrological model-based evaluation approach employing Soil Water Assessment Tool (SWAT) to identify the dominating drivers on the decadal streamflow patterns and other basin-scale water balance components, viz., blue water flow (BWF), green water storage (GWS), and green water flow (GWF) in the Brahmani and Baitarani River basins of eastern India. The results reveal that, in these basins, the climate change effect has relatively a higher impact on streamflow than the land-use change. This study surmises that the Brahmani and Baitarani River basins can be categorized under the high- and moderate-risk water scarcity zones, respectively. The developed approach of assessing the water scarcity risk under the non-availability of basin-scale sectoral water demands could be a reliable tool for many data-scarce river basins worldwide.

Fish community responses to antecedent hydrological conditions based on long-term data in Mediterranean river basins (Iberian Peninsula)

In recent decades many studies have proven the paramount impact of flow regimes on the structure of lotic ecosystems, both through extreme events (i.e. floods and droughts) but also during intermediate flows, which temporarily and spatially regulate the habitat availability. Human demand for water is steadily increasing and scientists are challenged to define ecosystem needs clearly enough to guide policies and management strategies. However, field studies demonstrated that a variety of interacting factors, such as, presence of barriers (e.g. dams) and temporal changes in habitat structure affect the abundance, composition and distribution of fish assemblages. This work based on quantile regression tested hypotheses to elucidate the effect of antecedent hydrological conditions on fish communities. A large monitoring database collecting and homogenizing the existing information on fish fauna in the Júcar River Basin District (Eastern Iberian Peninsula) was gathered and used to evaluate biological metrics (species richness, Capture Per Unit Effort-CPUE, and CPUE ratio over the total CPUE) related to life history strategies (i.e. periodic, opportunistic or equilibrium) and species origin (i.e. native, translocated or alien). The resulting dataset was complemented with diverse indicators of the measured daily discharge at the nearest gauging site. Most of the significant relationships confirmed the role of antecedent hydrological conditions as limiting factors, although other environmental factors likely play additional roles. In general, richness and abundance of alien species showed the higher proportion of significant associations, particularly spring flows and annual minima and maxima. These flow-ecology relationships shall be particularly useful to manage ecological responses to hydrological alteration. They also provide with clear ecological foundations for developing environmental flows assessments in Mediterranean river basins worldwide, using holistic approaches which can harmonise eco-hydrological approaches with smaller-scale and habitat-based ecohydraulics methods, especially under the current climate trends.

Using Satellite Observations to Assess Applicability of GLDAS and WGHM Hydrological Model

GLDAS and WGHM hydrological products from January 2002 to December 2012 are investigated with GRACE satellite observations to study the terrestrial water storage anomalies (TWSA) in 30 major river basins worldwide. GLDAS and WGHM model outputs are compared and evaluated in terms of annual amplitude, long-term trend and spatial-temporal consistency with GRACE observations. The results show that the four land surface models in GLDAS show an obvious seasonal cycle in TWSA, among which the amplitudes of CLM is the smallest, MOSAIC and VIC are largest, and NOAH is in middle which exhibits the strongest consistency to the average GLDAS estimates. Compared with the GRACE results, the annual amplitudes are obviously underestimated by both GLDAS and WGHM in most river basins, and the underestimation degree of GLDAS is greater than that of WGHM. Also, the opposite situation occurs in river basins located near the Arctic. In terms of long-term trend, the results of the three models are quite different, especially for river basin with small area and strong human intervention, GLDAS and WGHM are not capable enough of reflecting the impact of human activities and their output performances are poor, while the GRACE results are closer to the actual situation. It is also found that the river basins with obvious downward trends are mainly concentrated in the areas with high irrigation rate (>10%).

Transboundary water resources “A comparative study”: The lessons learnt to help solve the Nile basin water conflict

Abstract The problematic water situation in Egypt, as one of the River Nile basin countries, has been heightened by the harmful effects of the Grand Ethiopian Renaissance Dam (GERD) on Egypt’s share of the Nile water. In the light of this Egyptian attention was directed towards a study of worldwide transboundary water problems, in order to find the most effective methods for dealing successfully with water shortage problems in basin countries. The present study focuses on the most successful experiences in the management and development of international river basins worldwide, as well as studying the possibility of implementing these experiences in other basins, especially the River Nile basin. The study showed that overcoming the water scarcity problems in Egypt and increasing the Nile water yield for all the basin countries can be achieved, first of all through serious cooperation among all the basin countries for minimizing the huge water losses from the river (more than 1480 Billion Cubic Metres per year which represents roughly 90% of the whole basin income), and secondly to make use of the most successful technical and political experiences that have been implemented in other international river basins mentioned in the present study.

Reconstructing Terrestrial Water Storage Variations from 1980 to 2015 in the Beishan Area of China

Terrestrial water storage (TWS) is a key element in the global and continental water cycle. Since 2002, the Gravity Recovery and Climate Experiment (GRACE) has provided a highly valuable dataset, which allows the study of TWS over larger river basins worldwide. However, the lifetime of GRACE is too short to demonstrate long-term variability in TWS. In the Beishan area of northwestern China, which is selected as the most prospective site for high-level radioactive waste (HLRW) disposal, the assessment of long-term TWS changes is crucial to understand disposal safety. Monthly and annual TWS changes during the past 35 years are reconstructed using GRACE data, other remote sensing products, and the water balance method. Hydrological flux outputs from multisource remote sensing products are analyzed and compared to select appropriate data sources. The results show that a decreasing trend is found for GRACE-filtered and Center for Space Research (CSR) mascon solutions from 2003 to 2015, with slopes of −2.30 ± 0.52 and −1.52 ± 0.24 mm/year, respectively. TWS variations independently computed from the water balance method also show a similar decreasing trend with the GRACE observations, with a slope of −0.94 mm/year over the same period. Overall, the TWS anomalies in the Beishan area change seasonally within 10 mm and have been decreasing since 1980, keeping a desirable dry condition as a HLRW disposal site.

Partitioning the Impacts of Streamflow and Evaporation Uncertainty on the Operations of Multipurpose Reservoirs in Arid Regions

AbstractOngoing changes in global climate are expected to alter the hydrologic regime of many river basins worldwide, expanding historically observed variability as well as increasing the frequency...

Climate change impact assessment of a river basin using CMIP5 climate models and the VIC hydrological model

ABSTRACTClimate change has significant impacts on water availability in larger river basins. The present study evaluates the possible impacts of projected future daily rainfall (2011–2099) on the hydrology of a major river basin in peninsular India, the Godavari River Basin, (GRB), under RCP4.5 and RCP8.5 scenarios. The study highlights a criteria-based approach for selecting the CMIP5 GCMs, based on their fidelity in simulating the Indian Summer Monsoon rainfall. The nonparametric kernel regression based statistical downscaling model is employed to project future daily rainfall and the variable infiltration capacity (VIC) macroscale hydrological model is used for hydrological simulations. The results indicate an increase in future rainfall without significant change in the spatial pattern of hydrological variables in the GRB. The climate-change-induced projected hydrological changes provide a crucial input to define water resource policies in the GRB. This methodology can be adopted for the climate change impacts assessment of larger river basins worldwide.

The environmental cost of a reference withdrawal from surface waters: Definition and geography

Abstract World freshwater ecosystems are significantly deteriorating at a faster rate than other ecosystems. Water withdrawals are recognized as one of the main drivers of growing water stress in river basins worldwide. Over the years, much effort has been devoted to quantify water withdrawals at a global scale; however, comparisons are not simple because the uneven spatiotemporal distribution of surface water resources entails that the same amount of consumed water does not have the same environmental cost in different times or places. In order to account for this spatiotemporal heterogeneity, this work proposes a novel index to assess the environmental cost of a withdrawal from a generic river section. The index depends on (i) the environmental relevance of the impacted fluvial ecosystem (e.g., bed-load transport capacity, width of the riparian belt, biodiversity richness) and (ii) the downstream river network affected by the water withdrawal. The environmental cost has been estimated in each and every river section worldwide considering a reference withdrawal. Being referred to a unitary reference withdrawal that can occur in any river section worldwide, our results can be suitably arranged for describing any scenario of surface water consumption (i.e., as the superposition of the actual pattern of withdrawals). The index aims to support the interpretation of the volumetric measure of surface water withdrawal with a perspective that takes into account the fluvial system where the withdrawal actually occurs. The application of the index highlights the river regions where withdrawals can cause higher environmental costs, with the challenge of weighting each water withdrawal considering the responsibilities that it has on downstream freshwater ecosystems.

Engineered rivers in arid lands: searching for sustainability in theory and practice

ABSTRACTBeginning in the early twentieth century and progressing rapidly since the 1950s, large-scale water works have created engineered rivers. In dry-land basins they control flooding and provide water and energy to farms, cities and industry. Yet, they face numerous challenges. In 2013 we formed an interdisciplinary team to study future conditions of nine river basins worldwide. This paper presents the methodology and interim results for two of our basins, the Rio Grande and the Euphrates-Tigris. We conclude with a new definition of the sustainability of engineered rivers in arid lands, using dependable reservoir yield under drought conditions as the central indicator.

Basin-scale water-balance dataset (BSWB): an update

Abstract. This paper presents an update of a basin-scale diagnostic dataset of monthly variations in terrestrial water storage for large river basins worldwide (BSWB v2016, doi:10.5905/ethz-1007-82). Terrestrial water storage comprises all forms of water storage on land surfaces, and its seasonal and inter-annual variations are mostly determined by soil moisture, groundwater, snow cover, and surface water. The dataset presented is derived using a combined atmospheric and terrestrial water-balance approach with conventional streamflow measurements and reanalysis data of atmospheric moisture flux convergence. It extends a previous, existing version of the dataset (Mueller et al., 2011) temporally and spatially.

Erratum to: Evaluation of an ensemble of regional hydrological models in 12 large-scale river basins worldwide

Evaluation of an ensemble of regional hydrological models in 12 large-scale river basins worldwide (vol 141, pg 381, 2017)