Extreme Hydrological Conditions Research Articles

Response to hydrometeorological changes and evaluation of habitat quality in the Dongting Lake basin, China

ABSTRACT With the advancement of hydraulic engineering processes, surface water resources are encountering unprecedented crises that threaten social and ecological sustainability. This study analyzed the response changes and potential correlations between river conditions and climate change in the Dongting Lake (DTL) basin using gray correlation analysis and the LSTM model. Additionally, the InVEST model was employed to further assess the distribution of habitat quality within the basin. The results of the study showed that (1) the range of variation of environmental flows in each tributary became significantly narrower and the frequency of extreme hydrological conditions was reduced in the period after the abrupt hydrological change. (2) The hydrological status had a higher degree of correlation with the rainfall index, and the performance is more prominent on the Xiang River, and the influence of temperature is less. (3) Except in the Xiang River Basin, human activities are the dominant factor of runoff variation, and the annual contribution is generally higher than 50%. (4) Habitat quality in the ‘high’ distribution was the most guarded and always accounted for more than 60% of the basin, while habitat quality in the east-central part of the DTL basin and around the DTL was generally low.

Sensitivity of development goals to water scarcity of Iraq and transboundary regions

Iraq and its transboundary regions have significant challenges from water scarcity in combination with other social and environmental factors. There are short- and long-term implications for vulnerable demographics, such as youth. With Iraq's dependence on upstream water management, there is a need to address several critical factors of transboundary watersheds such as the Haditha, Mosul, Dokan, and Euphrates-Tigris basin. This paper develops the use of particular social, hydrological, and other environmental factors in a risk register of basins and vulnerable populations, where societal priorities vary across scenarios of hydrology and water. Social data (i.e., gridded youth population data) and hydrological observations (i.e., precipitation, temperature, root zone soil moisture, and Normalized Difference Vegetation Index (NDVI)) are obtained from publicly available satellite-based Earth observations and global models. Risk is defined and quantified as the disruption of basin order and spatial plots are provided to improve understanding of the spatial distribution of water scarcity challenges in the region with regard to vulnerable populations. The results feature identification of the most and least disruptive scenarios including: 1) population density is lowest in basins exposed to the highest air temperatures, 2) an urban-to-rural migration pattern (such as prompted by a public health crisis) would significantly disrupt basin order, and 3) populations with greatest exposure to extreme hydrological conditions of water scarcity are found in the southern basins of Iraq in or near the Al-Muthanna governorate. The impacts of this work are to steer future investments that mitigate risk of disrupted system orders and to increase system resilience of vulnerable populations to water scarcity.

Application of artificial countermeasures to enhance desilting efficiency in a reservoir under normal and extreme events

ABSTRACT The influx of flood-induced turbidity flows with high sediment concentrations into the reservoir can create sediment deposition issues, potentially jeopardizing water supply reliability. Efficient management of reservoir water resources is imperative for sustainable utilization. Evaluating the need for reservoir desilting involves comprehending the inflow and outflow dynamics of water-sediment discharges, the capacity of existing outlet structures, reservoir operation objectives, and available desilting technologies. However, given the altering hydrological conditions due to the impacts of climate change, there is a necessity for adaptive methods to ensure reservoir storage maintenance. Consequently, this study introduces the utilization of a flushing channel with artificial guiding structures to enhance desilting efficiency. A 2D numerical model offers convenient computational tools for assessing water-sediment transport behaviors across various operational scenarios based on reservoir management strategies. Data obtained from field observations is collected and analyzed to calibrate and verify the numerical model. By employing 2D numerical modeling, sediment concentration and desilting efficiency are calculated to support effective desilting operations within a reservoir. Simulation results indicate that the integration of additional artificial guiding structures at the bottom of the reservoir can enhance sedimentation mitigation outcomes by approximately 17.63% under normal conditions and by 5.27% under extreme hydrological conditions.

Metabolic Rates of Rainbow Trout Eggs in Reconstructed Salmonid Egg Pockets

In situ evaluations of the metabolic rates (i.e., respiration and excretion) of salmonid eggs are mostly indirect, focusing on the sampling of hyporheic water from wild or artificial nests. Comparatively, experimental studies carried out under controlled, laboratory conditions are less abundant due to methodological difficulties. This study presents a novel experimental setup aimed to address this issue and enable the measurement of oxygen and dissolved inorganic nitrogen fluxes in simulated rainbow trout (O. mykiss) egg pockets. The experimental setup consists of reconstructed egg pockets in cylindrical cores under flow-through conditions. Live and dead eyed-stage eggs were incubated in a natural, sterilised gravel substrate. Hyporheic water circulation was ensured using peristaltic pumps, with the possibility to collect and analyse inflowing and outflowing water for chemical analyses. Microcosm incubations, with closed respirometry of eggs in water alone, were also carried out in order to infer the importance of microbial respiration in the simulated egg pockets. The results show an increasing trend in oxygen demand, due to the development of biofilm in the reconstructed egg pockets and increased egg respiration rates. Moreover, egg pockets showed positive ammonium net fluxes connected with the advancing developmental egg stage, while nitrate removal peaked during the last phase of the experiment, mainly due to the formation of oxic-hypoxic interfaces, leading to couple nitrification–denitrification processes. The suggested approach enables to test a number of in situ situations, including the effects of extreme hydrological conditions, sediment clogging and sudden changes in water chemistry or temperature on the survival and metabolic performances of nests, at different egg development stages.

Non-perennial rivers and streams in extreme hydrological conditions—comparing the effectiveness of amplicon sequencing and digital microscopy for diatom biodiversity appraisal

IntroductionNon-perennial rivers and streams are increasingly present, in part because of climate change, even in the temperate climate. However, how the loss of connectivity and complete drying affect microphytobenthos in general and diatom communities in particular has gone mostly unstudied. MethodsWith this paper, we aim to close this gap, identifying diatom biodiversity through manual digital microscopy and rbcL amplicon sequencing, to observe a) which method is better suited to it and b) how the ecotone flow-pool-dry affects diatom diversity under duress. Three karstic, non-perennial rivers and streams with a gradient from natural to anthropogenically disturbed were sampled under flooding conditions and after a long and intense drought in 2022.ResultsOur results show that digital microscopy shows a higher diversity and species richness than amplicon sequencing. We posit that this might be due to a reduced pool of subaerophile taxa having been sequenced and being part of the reference database. Furthermore, the effect of drying only resulted in a reduction in diversity after this drought, although the biofilm was still alive under these conditions. DiscussionTo use amplicon sequencing for non-perennial river diatom diversity monitoring, the reference databases will have to be adapted to such systems, as most rivers may be subjected to drying regularly in the future.

Design experiences of MSE structures under complex conditions in a highway project

The design and construction of Mechanically Stabilized Walls (MSE) have had a great boom in Guatemala in recent years. Central America’s largest private infrastructure road project has required the construction of more than 30,000 m2 of MSE structures under extreme seismic, topographical, and hydrological conditions. Considering that Guatemala has been a country with very high seismicity and the project being on a good percentage of slopes on the margins of a river, made both the design and construction of the project face great challenges. The project consists of tier walls, walls with upper slopes, walls supported on extremely steep slopes and walls with heights that can reach more than 20 meters. Many of these structures have critical hydraulic and global stability conditions. There are three case studies of walls, that by their complexity deserve to be considered for further study and from which there are many lessons for the future use of mechanically stabilized structures in the face of complex conditions.

Design experiences of MSE structures under complex conditions in a highway project

The design and construction of Mechanically Stabilized Walls (MSE) have had a great boom in Guatemala in recent years. Central America’s largest private infrastructure road project has required the construction of more than 30,000 m2 of MSE structures under extreme seismic, topographical, and hydrological conditions. Considering that Guatemala has been a country with very high seismicity and the project being on a good percentage of slopes on the margins of a river, made both the design and construction of the project face great challenges. The project consists of tier walls, walls with upper slopes, walls supported on extremely steep slopes and walls with heights that can reach more than 20 meters. Many of these structures have critical hydraulic and global stability conditions. There are three case studies of walls, that by their complexity deserve to be considered for further study and from which there are many lessons for the future use of mechanically stabilized structures in the face of complex conditions.

On the origin and processes controlling the elemental and isotopic composition of carbonates in hypersaline Andean lakes

The Altiplano-Puna Plateau of the Central Andes hosts numerous lakes, playa-lakes, and salars with a great diversity and abundance of carbonates forming under extreme climatic, hydrologic, and environmental conditions. To unravel the underlying processes controlling the formation of carbonates and their geochemical signatures in hypersaline systems, we investigated coupled brine-carbonate samples in a high-altitude Andean lake using a wide suite of petrographic (SEM, XRD) and geochemical tools (δ2H, δ18O, δ13C, δ11B, major and minor ion composition, aqueous modelling). Our findings show that the inflow of hydrothermal springs in combination with strong CO2 degassing and evaporation plays an important role in creating a spatial diversity of hydro-chemical sub-environments allowing different types of microbialites (microbial mounds and mats), travertines, and fine-grained calcite minerals to form. Carbonate precipitation occurs in hot springs triggered by a shift in carbonate equilibrium by hydrothermal CO2 degassing and microbially-driven elevation of local pH at crystallisation. In lakes, carbonate precipitation is induced by evaporative supersaturation, with contributions from CO2 degassing and microbiological processes. Lake carbonates largely record the evaporitic enrichment (hence salinity) of the parent water which can be traced by Na, Li, B, and δ18O, although other factors (such as e.g., high precipitation rates, mixing with thermal waters, groundwater, or precipitation) also affect their signatures. This study is of significance to those dealing with the fractionation of oxygen, carbon, and boron isotopes and partitioning of elements in natural brine-carbonate environments. Furthermore, these findings contribute to the advancement in proxy development for these depositional environments.

Effect of Hydraulic Structure on Mitigating Extreme Hydrological Conditions of a Small River in the Temperate Zone (Główna River, Central Europe)

Water resources are of elementary economic and environmental importance, and the observed global transformations as well as regional environmental conditions necessitate activities aimed at providing an optimal amount of water at different levels. One such solution is hydrotechnical infrastructure that permits the precise control of the amount of water in the catchment. This paper presents results concerning changes in the water flow in the Główna River in Poland before (1955–1983) and after (1984–2021) the construction of the Kowalski Reservoir. In the former period, there were no changes in water flow, and the obtained results were not statistically significant (p 0.05). In the period after the construction of the reservoir, a decreasing trend in monthly flow was observed in December, April, July, September, and October. Moreover, a decrease in 1, 3, 7, and 90 day maximum flow was observed. For maximum 30 day flow, the changes were below the threshold of the adopted significance level. Moreover, minimum flow in the period after the construction of the reservoir showed no significant decreasing trend. In hydrological terms, the reservoir served its purpose by contributing to the stabilisation of the water flow. This information is important from the point of view of an increase in retention and corresponds with a broader programme conducted in the territory of Poland. In the context of the construction of further reservoirs, it is important to investigate the current range of changes in water circulation for objects of the type already functioning in the environment, constituting an actual point of reference.

A deep learning model for reconstructing centenary water storage changes in the Yangtze River Basin

Since 2002, the Gravity Recovery and Climate Experiment (GRACE) and its Follow-On mission (GRACE-FO) have facilitated highly accurate observations of changes in total water storage anomalies (TWSA). However, limited observations of TWSA derived from GRACE in the Yangtze River Basin (YRB) have hindered our understanding of its long-term variability. In this paper, we present a deep learning model called RecNet to reconstruct the climate-driven TWSA in the YRB from 1923 to 2022. The RecNet model is trained on precipitation, temperature, and GRACE observations with a weighted mean square error (WMSE) loss function. The performance of the RecNet model is validated and compared against GRACE data, water budget estimates, hydrological models, drought indices, and existing reconstruction datasets. The results indicate that the RecNet model can successfully reconstruct historical water storage changes, surpassing the performance of previous studies. In addition, the reconstructed datasets are utilized to assess the frequency of extreme hydrological conditions and their teleconnections with major climate patterns, including the El Niño-Southern Oscillation, Indian Ocean Dipole, Pacific Decadal Oscillation, and North Atlantic Oscillation. Independent component analysis is employed to investigate individual climate patterns' unique or combined influence on TWSA. We show that the YRB exhibits a notable vulnerability to extreme events, characterized by a recurrent occurrence of diverse extreme dry/wet conditions throughout the past century. Wavelet coherence analysis reveals significant coherence between the climate patterns and TWSA across the entire basin. The reconstructed datasets provide valuable information for studying long-term climate variability and projecting future droughts and floods in the YRB, which can inform effective water resource management and climate change adaptation strategies.

Time-series-based habitat model development for surface water management on endangered aquatic plant Isoetes taiwanensis conservation in mountain wetlands

Wetland scientists and ecological engineers are encouraged to comprehend hydrological driving forces for enhancing environmental conservation, ecological restoration, and integrated management. The spatiotemporal distribution and dynamics of aquatic plants are critical for improving their functional niche in mountain wetlands. This study evaluates the hydrological variation of a mountain wetland to determine the adverse and advantageous situations of an endemic and endangered aquatic plant by establishing a time-variant habitat index model considering the inundation frequency and duration of a specific water level. The model was developed and verified by integrating with a field survey of biotic and abiotic data to build the corresponding habitat suitability indices through conducting polynomial regression analysis. The results indicate its capability to effectively quantify the intricate relationship between water level and plant coverage in different places and seasons. The habitat quality can be derived as the combined functions of total scattered and maximum continuous periods of dominant and nondominant water depths. Although the coverage area fluctuated in different seasons, the model reveals significant capabilities to bridge the gaps for reaching the extreme hydrological conditions which might cause the extinction of the endangered aquatic plant Isoetes taiwanensis. The plant is found to be more competitive in the region, implemented by excavation and consolidation, with deeper water depth and higher water conservation. We suggest adaptative water level management at the planning and design phases and rehabilitating these essential habitat patterns to enrich the survival of I. taiwanensis in the dry season. Strengthening the water retention capacity of the bottom soil to reduce water leakage and groundwater seepage velocity may also help achieve integrated management for surface water conservation in the wetland.

Thermo-hydro-poro-mechanical responses of a reservoir-induced landslide tracked by high-resolution fiber optic sensing nerves

Thermo-poro-mechanical responses along sliding zone/surface have been extensively studied. However, it has not been recognized that the potential contribution of other crucial engineering geological interfaces beyond the slip surface to progressive failure. Here, we aim to investigate the subsurface multi-physics of reservoir landslides under two extreme hydrologic conditions (i.e. wet and dry), particularly within sliding masses. Based on ultra-weak fiber Bragg grating (UWFBG) technology, we employ special-purpose fiber optic sensing cables that can be implanted into boreholes as “nerves of the Earth” to collect data on soil temperature, water content, pore water pressure, and strain. The Xinpu landslide in the middle reach of the Three Gorges Reservoir Area in China was selected as a case study to establish a paradigm for in situ thermo-hydro-poro-mechanical monitoring. These UWFBG-based sensing cables were vertically buried in a 31 m-deep borehole at the foot of the landslide, with a resolution of 1 m except for the pressure sensor. We reported field measurements covering the period 2021 and 2022 and produced the spatiotemporal profiles throughout the borehole. Results show that wet years are more likely to motivate landslide motions than dry years. The annual thermally active layer of the landslide has a critical depth of roughly 9 m and might move downward in warmer years. The dynamic groundwater table is located at depths of 9–15 m, where the peaked strain undergoes a periodical response of leap and withdrawal to annual hydrometeorological cycles. These interface behaviors may support the interpretation of the contribution of reservoir regulation to slope stability, allowing us to correlate them to local damage events and potential global destabilization. This paper also offers a natural framework for interpreting thermo-hydro-poro-mechanical signatures from creeping reservoir bank slopes, which may form the basis for a landslide monitoring and early warning system.

Association Between Hydrological Conditions and Dengue Fever Incidence in Coastal Southeastern China From 2013 to 2019

Dengue fever is a climate-sensitive infectious disease. However, its association with local hydrological conditions and the role of city development remain unclear. To quantify the association between hydrological conditions and dengue fever incidence in China and to explore the modification role of city development in this association. This cross-sectional study collected data between January 1, 2013, and December 31, 2019, from 54 cities in 4 coastal provinces in southeast China. The Standardized Precipitation Evapotranspiration Index (SPEI) was calculated from ambient temperature and precipitation, with SPEI thresholds of 2 for extreme wet conditions and -2 for extreme dry conditions. The SPEI-dengue fever incidence association was examined over a 6-month lag, and the modification roles of 5 city development dimensions were assessed. Data were analyzed in May 2022. City-level monthly temperature, precipitation, SPEI, and annual city development indicators from 2013 to 2019. The primary outcome was city-level monthly dengue fever incidence. Spatiotemporal bayesian hierarchal models were used to examine the SPEI-dengue fever incidence association over a 6-month lag period. An interaction term between SPEI and each city development indicator was added into the model to assess the modification role of city development. Included in the analysis were 70 006 dengue fever cases reported in 54 cities in 4 provinces in China from 2013 to 2019. Overall, a U-shaped cumulative curve was observed, with wet and dry conditions both associated with increased dengue fever risk. The relative risk [RR] peaked at a 1-month lag for extreme wet conditions (1.27; 95% credible interval [CrI], 1.05-1.53) and at a 6-month lag for extreme dry conditions (1.63; 95% CrI, 1.29-2.05). The RRs of extreme wet and dry conditions were greater in areas with limited economic development, health care resources, and income per capita. Extreme dry conditions were higher and prolonged in areas with more green space per capita (RR, 1.84; 95% CrI, 1.37-2.46). Highly urbanized areas had a higher risk of dengue fever after extreme wet conditions (RR, 1.80; 95% CrI, 1.26-2.56), while less urbanized areas had the highest risk of dengue fever in extreme dry conditions (RR, 1.70; 95% CrI, 1.11-2.60). Results of this study showed that extreme hydrological conditions were associated with increased dengue fever incidence within a 6-month lag period, with different dimensions of city development playing various modification roles in this association. These findings may help in developing climate change adaptation strategies and public health interventions against dengue fever.

ГИС гидроэкологической безопасности бассейна р. Селенги: структура, информационное наполнение и функциональные возможности

The transboundary basin of the Selenga river (the main tributary of Lake Baikal) is characterized by widespread and frequent hazardous events of climatic, hydrological and geomorphological nature. To integrate, display and analyze various data on these events, as well as provide them to the scientific community, a web GIS “Hydrological and environmental safety of the Selenga river basin” has been developed. The structure of the web GIS includes layers and databases that characterize the average long-term and extreme climatic and hydrological conditions in the basin, hazardous processes of hydrological and geomorphological nature, as well as their negative impact on landscapes, settlements and infrastructure. Both external databases and services (long-term weather and hydrological data series, WorldClim 2.0 database, ERA5-Land reanalysis and other) and previously unpublished result of the authors’ studies were used for web GIS content. The web-GIS development is based on open source software and libraries. A feature of the web GIS in comparison with previously published analogues for other river’s basins is an information rich climate section, which allows to assess various manifestations of the observed climate change in the Selenga river basin. Also, the data on several potentially hazardous natural processes like mudflows or aufeis formation are published on the service for the first time. Prospects for the development and improvement of the web GIS are associated with the publication of new GIS layers and databases compiled by the authors, with the development of hazard and risk assessment maps for various types of hazardous hydrological events. In addition, climatic characteristics based on modern ERA5 reanalysis and future climate projections for the 21st century are planned to be published.

Securing the Environmental Water Requirements of Seasonally Ponding Wetlands: Partnering Science and Management through Benefit Sharing

Although environmental flow regime assessments are becoming increasingly holistic, they rarely provoke water managers to enact the adaptive water reallocation mechanisms required to secure environmental water for wetlands. The conditions that cause science-based environmental flow assessments to succeed or fail in informing the management of environmental water requirements remain unclear. To begin to resolve these conditions, we used process tracing to deconstruct the sequence of activities required to manage environmental water in four case studies of seasonally ponding wetlands in Mediterranean and Mesoamerican watersheds. We hypothesized that, when the flexibility and equitability of the socioeconomic system do not match the complexity of the biophysical system, this leads to a failure of managers to integrate scientific guidance in their allocation of environmental water. Diagnostic evidence gathered indicates that science-management partnerships are essential to align institutional flexibility and socioeconomic equitability with the system’s ecohydrological complexity, and thus move from determination to reallocation of environmental water. These results confirm that institutions e.g., river basin organizations need to be supplemented by motivated actors with experience and skill to negotiate allocation and adaptive management of environmental water. These institutional-actor synergies are likely to be especially important in water scarce regions when the need to accommodate extreme hydrological conditions is not met by national governance capacity. We conclude by focusing on benefit sharing as a means to better describe the conditions for successful science-based environmental flow assessments that realize productive efficiency in environmental water allocation i.e., recognition of multiple values for both people and ecosystems.

Evaluation of the Groundwater and Irrigation Quality in the Zhuoshui River Alluvial Fan between Wet and Dry Seasons

The Zhuoshui River alluvial fan is one of the most important groundwater and agricultural areas in Taiwan. Abundant groundwater resources are the main source of domestic water supply and irrigation water. However, groundwater recharge and groundwater quality have been greatly affected under extreme climate and hydrological conditions. Hence, the quality of groundwater has been a topic of concern to the public. In this study, groundwater level and groundwater quality data of the Zhuoshui River alluvial fan from 2008 to 2020 were used to divide the wet and dry season groups according to the sampling dates. An independent samples t-test was used to evaluate the differences in the mean groundwater level and the mean concentration between the wet and dry seasons. The test results show that there was no statistically significant difference in the mean groundwater level between the wet and dry seasons. This may result from the time lag effects of groundwater recharge. Except for groundwater temperature, bicarbonate, and total organic carbon (TOC), there were no significant differences among the mean concentrations of other groundwater quality parameters in Aquifer 1 and Aquifer 2 between the wet and dry seasons. In terms of the alluvial fan location, although the soil texture, land utilization, cropping systems, and hydrogeology of the proximal, mid-, and distal fan may affect groundwater quality variations, it seems that only Aquifer 1 is affected by surface water infiltration, resulting in significant differences in mean groundwater temperature, mean concentrations of major ions, and nitrate between the wet and dry seasons, whereas Aquifer 2 is less affected. At the same time, owing to the geological conditions and intensive cultivation in the Zhuoshui River alluvial fan, nitrate and arsenic could represent a high risk to the public’s health if groundwater is used as a source for domestic water supply or irrigation water in the distal fan area, whether in the wet season or dry season. Meanwhile, due to global climate change and uneven droughts and floods, the hydrological conditions of the so-called “wet season” and “dry season” are obviously different from those in the past. Compared with precipitation, groundwater level may be a better indicator for understanding variations in groundwater quality.

Transport of Potentially Toxic Elements in Solid Particulate Matter during Flash Flood Events in Upper and Lower Stretch of the Sava River

During extreme hydrological conditions such as flood events, sediments and alluvial soils may become re-suspended. As a consequence, the concentration of solid particulate matter (SPM) in the water column increases. As sediments represent a sink for the contaminants, when such perturbation occurs, the toxic substances may be re-dissolved into the water, causing harmful effects to the freshwater habitat. The purpose of this study was to evaluate the release of potentially toxic elements associated to SPM during flash floods. Two sampling sites on the Sava River were chosen: Litija (Slovenia), where the river has still the characteristics of an alpine river, and in Belgrade (Serbia), where Sava is a lowland river with a flat riverbed, slower flow and bigger quantities of fine-grained sediment. The results of the study showed a good correlation between the SPM mass concentration and water level/discharge. At both sampling sites, elevated concentrations of As, Cd, Cr, Cu, Pb, Ni and Zn were determined in SPM, indicating a moderate level of contamination at Litija and a high level at Belgrade. The results demonstrated that during the two investigated flash flood events limited the dissolution of PTE from SPM-bearing particles.

Resilient California Water Portfolios Require Infrastructure Investment Partnerships That Are Viable for All Partners

AbstractWater scarcity is a growing problem around the world, and regions such as California are working to develop diversified, interconnected, flexible, and resilient water supply portfolios. To meet these goals, water utilities, irrigation districts, and other organizations will need to cooperate across scales to finance, build, and operate shared water supply infrastructure. However, planning studies to date have generally focused on partnership‐level outcomes (i.e., highly aggregated cost‐benefit analyses), while ignoring the heterogeneity of benefits, costs, and risks across the individual partners. This study contributes an exploratory modeling analysis that tests thousands of alternative infrastructure partnerships in the Central Valley of California, using a daily scale simulation model (CALFEWS) to evaluate the effects of new infrastructure on individual water providers. The viability of conveyance and groundwater banking investments are as strongly shaped by partnership design choices (i.e., which water providers are participating, and how is the project's debt distributed?) as by extreme hydrologic conditions (i.e., floods and droughts). Importantly, most of the analyzed partnerships yield highly unequal distributions of water supply and financial risks across the partners, so that only 8% of the partnerships explored are capable of providing water to each partner for under $200/ML. Partnership viability is especially rare in the absence of groundwater banking facilities (1%), or under dry hydrologic conditions (1%), even under explicitly optimistic assumptions regarding climate change. Given these results, we outline several major policy implications for institutionally complex regions such as California, which are currently investing heavily in cooperative approaches to resilient water portfolio design.

Extracting operation behaviors of cascade reservoirs using physics-guided long-short term memory networks

Study regionQingjiang cascade reservoir, China. Study focusReservoirs regulate the natural streamflow to utilize water resources comprehensively. How to mine the existing massive reservoir operation data to describe human operation behaviors is a challenge. To address this issue, a data-driven method, Long short-term memory (LSTM), was used to simulate the reservoir outflow by inputting historical information. The physics-guided LSTM model, shortly named PG-LSTM, was formulated by using synthetic flood samples and physical constraints of water balance, boundary, and monotonicity. New hydrological insights(1) PG-LSTM can reproduce historical outflow with seasonal variations, or predict outflow without lags, (2) knowledge of reservoir operations can guide LSTM with the reduction of negative flow occurrence and the accurate identification of operation behaviors under extreme hydrological conditions, (3) specifically, compared with conventional LSTM, gradient boosting regression tree and conventional reservoir operation, PG-LSTM can improve the Nash-Sutcliffe efficiency of cascade reservoir during the test period from 0.50, 0.20, and 0.17 to 0.54 in the reproduction scenario, and from 0.84, 0.26, and 0.17 to 0.85 in the prediction scenario with five-fold cross-validation method. The PG-LSTM is helpful to describe human operation behaviors of reservoirs.

Application of Nonlinear Time Series and Machine Learning Algorithms for Forecasting Groundwater Flooding in a Lowland Karst Area

AbstractIn karst limestone areas interactions between ground and surface waters can be frequent, particularly in low lying areas, linked to the unique hydrogeological dynamics of that bedrock aquifer. In extreme hydrological conditions, however, this can lead to wide‐spread, long‐duration flooding, resulting in significant cost and disruption. This study develops and compares a nonlinear time‐series analysis based nonlinear autoregressive model with exogenous variables (NARX), machine learning based near support vector regression as well as a linear time‐series ARX model in terms of their performance to predict groundwater flooding in a lowland karst area of Ireland. The models have been developed upon the results of several years of field data collected in the area, as well as the outputs of a highly calibrated semi‐distributed hydraulic/hydrological model of the karst network. The prediction of total flooding volume indicates that the performances of all the models are similarly accurate up to 10 days into the future. A NARX model taking inputs of the past 5 days' flood volume; rainfall data and tidal amplitude data across the past 4 days, showed the best flood forecasting performance up to 30 days into the future. Existing real‐time telemetric monitoring of water level data at two points in the catchment can be fed into the model to provide an early warning flood warning tool. The model also predicts freshwater discharge from the inter‐tidal spring into the Atlantic Ocean which hitherto had not been possible to monitor.