Reservoir Capacity Research Articles

Study on gas content variation and main controlling of low-rank coal in Huanglong Jurassic coalfield

In order to study the controlled factors and variation of gas content in deep low-rank coal reservoirs, taking No.4 coal of Jurassic Yan’an Formation in Huanglong coalfield as an example, collects the production data and prepares the coal samples. Carrying out the coal rock and coal quality test and multi-temperature methane isothermal adsorption experiment to explore the influence of different temperature and pressure conditions on coal adsorption capacity, and analyzes the variation characteristics of gas content with burial depth combined with geological conditions. The results show that the sedimentary, structural and hydrogeological conditions have a certain influence on the formation and preservation of coalbed methane. The gas content increases with the increase of coalification degree and vitrinite content, and decreases with the increase of inertinite content, ash yield and volatile yield. With the increase of moisture, the gas content increased first and then decreased. When the pressure is less than 4 MPa, the adsorption capacity increases about 4-4.7m3/t with the increase of pressure, and the increasing trend slows down when the pressure is greater than 4 MPa. The adsorption capacity decreased more obviously with the increase of temperature when the temperature increased from 25°C to 35°C. Based on the prediction model of saturated adsorption capacity of deep coal reservoirs, it is found that there is a gas content critical conversion depth 800-900 m. The gas content shows a process of rapid increase (<800 m)-slow increase (800–900 m)-gradual decrease (>900 m) with the increase of burial depth. Below 800 m, the positive effect of reservoir pressure is dominant, and the gas content increases with burial depth. Above 900 m, the negative effect of reservoir temperature is dominant, and the gas content decreases with burial depth. The study results provide a theoretical basis for the development of deep low-rank coalbed methane resources.

Evaluation of reservoir sedimentation using bathymetry survey: a case study on Adebra night storage reservoir, Ethiopia

Reservoir sedimentation is a serious challenge that reduces reservoir life. Because it decreases the initial capacity of the reservoir and has an impact on drinking water supply, irrigation, and hydropower activities. Inadequate land activities and poor management techniques cause soil erosion and reduce reservoir storage capacity. As a result, accurate sediment estimation was assist in the adoption of sustainable land-use activities and best management practices that lead to effective reservoir operations. The main objective of this study was to evaluate the rate of sedimentation and remaining capacity of Adebra night storage reservoir (NSR) using a bathymetric survey and Arc-GIS 10.8. A comparison of original and current reservoir capacity was used to evaluate the quantity of sediment deposition in the reservoir. The latter was developed using Arc-GIS 10.8 and a bathymetry survey that was used to develop the TIN surface and evaluate reservoir volume. The Adebra NSR reservoir capacity was decreased by the accumulation of sedimentation from 36,902 m3 in 2012 to 27,722 m3 in 2020. The results of this study showed that the Adebra night storage reservoir had lost on average 24.8% of its capacity due to sedimentation, during 8 years of operation. The average deposition rate of sedimentation in Adebra NSR was estimated to be 1147.5 m3/year, with a loss rate of 3.1% per year. The value of sedimentation rates found in live storage of the reservoir area was 1147.5 m3/year. At the current time, the expected life of the night storage reservoir was reduced due to a lack of proper soil conservation practices in the reservoir catchment areas. In general, the study finding showed that the capacity of NSR was reduced by the accumulation of sedimentation year to year throughout the design period. Therefore, to improve the capacity of NSR should be planning and implementing different techniques of sediment control and removal, depending on the estimation of sediment production from watersheds of inlets and outlets of reservoirs.

Effects of competitive adsorption on production capacity during CO2 displacement of CH4 in shale

During CO2 displacement of CH4 in shale, competitive adsorption results in reduced pore space used for gas flow in shale, which is closely associated with the production capacity of shale-gas reservoirs. Thus, the present work investigates the effects of CO2–CH4 competitive adsorption on production capacity. Herein, a slit–pore model is developed in terms of gas storage (CO2 and CH4) and graphene pores using molecular dynamics and implemented via large-scale atomic/molecular massively parallel simulator. The effects of CO2 injection pressure, temperature, and velocity and of pore size on CO2–CH4 displacement and competitive adsorption properties are simulated and examined. Hence, the displacement efficiency of CH4 and the adsorption layer thickness of the CO2–CH4 binary mixture are determined. Moreover, based on a basic seepage model of planar linear flooding, the effect of CO2–CH4 competitive adsorption on production capacity is analytically investigated. Results demonstrate that the production capacity with consideration of adsorption layer thickness is less than that without consideration of adsorption layer thickness, illustrating that CO2–CH4 competitive adsorption behaviors are closely connected with permeability, flow rate, and production capacity of shale-gas reservoirs, especially for shale-gas reservoirs containing large numbers of pores and slits.

Sustainable sediment management for sustainable use of reservoirs

Sustainable sediment management for sustainable use of reservoirs

Radical-Induced Low-Field 1H Relaxation in Solid Pyruvic Acid Doped with Trityl-OX063.

In dynamic nuclear polarization (DNP), radicals such as trityl provide a source for high nuclear spin polarization. Conversely, during the low-field transfer of hyperpolarized solids, the radicals' dipolar or Non-Zeeman reservoir may act as a powerful nuclear polarization sink. Here, we report the low-temperature proton spin relaxation in pyruvic acid doped with trityl, for fields from 5 mT to 2 T. We estimate the heat capacity of the radical Non-Zeeman reservoir experimentally and show that a recent formalism by Wenckebach yields a parameter-free, yet quantitative model for the entire field range.

Exploring a multi-objective cluster-decomposition framework for optimizing flood control operation rules of cascade reservoirs in a river basin

Multi-objective flood control operation of cascade reservoirs is a vital issue in river basin management. However, traditional multi-objective approaches commonly provide one operation scheme only and fail to offer decision-makers with more Pareto-front options. This study explores a multi-objective cluster-decomposition framework for optimizing the flood control operation rules of cascade reservoirs in a river basin. The proposed framework involves a multi-objective optimization module, a cluster-decomposition module, and an evaluation and sorting module. The multi-objective cluster-decomposition framework simultaneously deals with three objectives: to minimize the flood peaks of flood control points (O1); to minimize the reservoir capacity used for flood control (O2); and to minimize the flood diversion volume of the flood detention area (O3). The complex flood control system composed of two cascade reservoirs, four navigation-power junctions, one flood detection area, and three flood control points in the Ganjiang River basin of China constitutes the case study. The results demonstrate that the proposed framework can significantly improve the comprehensive benefits of the cascade reservoirs, where the maximum reduction in objectives O1–O3 is 2071 m3/s (the improvement rate is 2.64 %), 219 million m3 (the improvement rate is 44.60 %), and 167 million m3 (the improvement rate is 78.13 %), respectively. Furthermore, in contrast to the traditional multi-attribute evaluation method, the proposed framework can effectively identify compromised decisions through a cluster-decomposition module, which provides beneficial trade-off guidance in making a sound decision upon Pareto-front options.

Study on the Electrical Control Mechanism of Gas Occurrence in a Microscale Coal Matrix.

The study of the gas occurrence mechanism in a microscale coal matrix is the basis of coalbed methane (CBM) reservoir formation mechanism analysis and its exploration and development scheme design, which has important scientific and engineering significance. Currently, many researchers are focusing on a specific coal type to explore the macroscopic adsorption characteristics of gas occurrence. However, the research on the microscale gas-solid coupling mechanism is relatively rare and the electrical control mechanism of gas occurrence is not reported in detail. This study focuses on the electrical mechanism of microscale gas occurrence using physical simulation experiments and molecular dynamics analysis. This study clarifies the "gas adsorption-electrical properties-functional group" linkage mechanism and explores the macroscopic performance of the microscale gas occurrence mechanism using electrical properties. The study reveals the following: (1) the coal reservoirs exhibit a weak negative potential at the nanoscale, and the trends of surface potential (SP) and surface electrical charging density (SECD) are fluctuated with the degree of coal rank increases; (2) there is a good correlation between the SP, SECD values, and the relative content of functional groups; and (3) the charge density on the coal's microscopic surface influences their gas molecule attraction capacity, affecting the gas adsorption capacity of coal reservoirs at the macroscale. This study presents a theoretical foundation for establishing the molecular force field superposition mechanism of gas occurrence in microscale coal matrix and has broad application prospects in the macroscale numerical simulation of CBM development.

Driving Mechanisms of the Evolution and Ecological Water Demand of Hulun Lake in Inner Mongolia

Hulun Lake is located in the Hulun Buir Grassland in Inner Mongolia and is an important component of the northern ecological barrier of China. Fluctuations in its area directly affect the stability of the surrounding ecological environments. In this study, Hulun Lake was taken as the study object, and meteorological data, water body area, water level, reservoir capacity, runoff volume, and social statistical data were used to study the dynamic changes in Hulun Lake and the critical driving forces. We constructed a balance analysis equation, determined the role of groundwater in the water cycle, and examined the minimum ecological water demand of Hulun Lake. The results of the analyses revealed that during the last 55 years, the variation trends of the water level, area, and reservoir capacity were generally consistent and could be divided into six stages. The increased temperature decreased precipitation, and increased evaporation resulted in decreased water flow from the major rivers supplying the lake, which was the main cause of the decrease in the water level and area of Hulun Lake. Groundwater was involved in the water cycle of Hulun Lake. After deducting the seepage and surface drainage, we found that the groundwater recharge volume was around 792 million m3 yearly. Based on the environmental, ecological, and production functions of Hulun Lake, the minimum ecological water demand is 11.272 billion m3.

PRODUKSI DAN KONSUMSI OKSIGEN ZONA ATAS DAN BAWAH SECCHI DISK DI WADUK BENANGA SAMARINDA

The high sedimentation and erosion in reservoirs in Indonesia have been the main factors causing the decrease in reservoir capacity. High sedimentation is the main factor causing the decline in the carrying capacity of the reservoir ecosystem. This research was conducted to determine the production of dissolved oxygen and respiration in the upper and lower zones of the sechi disk in the Benanga Reservoir. As data on dissolved oxygen production and respiration in the upper and lower zones of the secchi disk. This study uses a dark and light bottle storage method to see the difference between the upper and lower zones of the waters so as to get the production and oxygen consumption. Dissolved oxygen production and consumption studies (dark and light bottles) used a 4-hour incubation. The results show that the dissolved oxygen consumption in the upper zone is 2.07 mg/L and the lower zone is 1.90 mg/L, gross primary productivity (GPP) in the upper zone is 4.95 mg/L and the lower zone is 4.32 mg/L, and the net primary productivity (NPP) is in the upper zone. 2.88 mg/L and lower zone 2.42 mg/L.

Höegh LNG and Altera Infrastructure is scaling up large scale CCS infrastructure

In a joint initiative, called “Stella Maris CCS” Altera Infrastructure and Höegh LNG are working together to provide cost efficient floating Carbon Capture and Storage infrastructure solutions for a global market, not limited to size or geographical location.Valuable infrastructure experience is brought together; with FPSO (Floating Production, Storage and Offloading) and Dynamically Positioned Shuttle Tankers from Altera and FSRU’s (Floating Storage Regasification Unit) from Höegh. We intend to continue to build on our heritage and experience, using our combined skills to contribute to carbon emission reduction around globe. With the “Stella Maris CCS” project, we will essentially be doing what we are doing today, only in reverse. Our solution, initiated in 2019 as the first of its kind, will offer a large-scale floating infrastructure for collection, transport, and injection of CO2 into subsea reservoirs/aquifers.Our infrastructure concept consists of 2-3 Carbon Collection Storage Units (CCSU) to aggregate volumes at different key locations, 3-4 CO2 Shuttle Carriers and one Floating Storage and Injection Unit, the total amount of CO2 injected with these assets can reach up to 10 million tons per year.In order to realize large scale CCS, the unit costs must come down, and the barriers for emitting industries to invest in capture plants must be lowered. With Stella Maris we are addressing these hurdles. The larger ship design enables carrying volumes of CO2 at low pressure and will allow for greater economies of scale in the absence of a pipeline which places less limitations on distance to reservoir and ultimate flow capacity. Having a centralized conditioning of CO2 in a CCSO hub allows more flexibility for on-site capture design from multiple onshore industrial emission sources with shared port access. To defray high logistics cost in e.g. the Baltic region, a hub and spoke transportation approach enables collection in smaller parcels, milk-run gathering and conditioning for large scale transfer for storage in an offshore subsea reservoir on the Norwegian Continental shelf.

Storage capacity of a karst groundwater reservoir associated with a large dam in a humid subtropical canyon karst area in southwestern China

Storage capacity of a karst groundwater reservoir associated with a large dam in a humid subtropical canyon karst area in southwestern China

Mechanical Constitutive and Seepage Theoretical Model of Water Storage Media Based on Fractional Derivative

Using an abandoned underground goaf in coal mines as water reservoirs has been successfully applied for protecting mine water resources in western China. The water storage media are composed of broken rock masses and the voids between the rock masses. It is critical for reservoir capacity calculation that the deformation characteristics and seepage evolution of the water storage media under triaxial stress are theoretically described. In this study, broken rock masses and the space among the rock masses are simplified as two springs in a series. The mechanical behavior of the broken rock mass is described by Hooke’s law of linear elasticity, and the deformation characteristics of the space among the rock masses are represented by a nonlinear elastic constitutive model. The nonlinear stress-strain constitutive model of the water storage media is established by combining Hooke’s law and the fractional derivative stress-strain model. Similarly, a non-Darcy seepage model of the water storage media is obtained. The nonlinear stress-strain model is verified by mechanical experiments, physical simulation tests, and field measured data, and parameter sensitivity analysis is performed. The non-Darcy seepage equation is fitted and analyzed by using the seepage experimental data of the broken rock mass under triaxial compression conditions. The fractional non-Darcy model rather than the Forchheimer equation can more accurately describe the nonlinear seepage process in water storage media.

Importance and main ecological and environmental problems of lakes in China

<p indent="0mm">Lakes including reservoirs are sensitive to global environmental change and human activities in the basin. They are sensitive sentinels and regulators of global environmental change and regional climate. Meanwhile, lakes are important constituent of “landscape, forest, farmland, lake, grassland and sand” life community. Remote sensing monitoring showed that there were 2670 lakes (≥<sc>1 km²)</sc> with a total water area of <sc>80662.4 km²,</sc> and 5156 reservoirs (≥<sc>1 km²)</sc> with a total water area of <sc>39697.1 km²</sc> in China in 2020. China Water Statistical Yearbook 2021 showed that the number and storage capacity of completed reservoirs increased from 86822 to 98566, and from <sc>416.9</sc> to <sc>930.6 km³</sc> from 1980 to 2020. Therefore, there is a total lakes and reservoirs area of <sc>120359.5 km²,</sc> but only accounting for 1.25% of China’s land area. Although the area of lakes and their proportion of land area are very limited, lakes play a vital role in ensuring the ecological civilization construction and promoting the economic and social development of the basin. Unfortunately, the importance and ecological service values of lakes are seriously underestimated and lack the real quantification. Therefore, this study systematically explores and quantifies the importance and ecological services of lakes in China from seven different perspectives. First, lakes are the most and the best centralized drinking water sources (CDWSs) contributing 40.6% of the CDWSs vs. river (30.8%) and groundwater (28.6%), and act as the backbone of the safety of drinking water in China based on 1093 CDWSs from 340 prefecture-level cities and 55 county-level cities (population ≥1 million). Second, lakes have important regulation and storage functions and play a key role in flood control and drought resistance. Based on the national lake survey data, the total amount of water regulation of natural lakes (≥<sc>1 km²)</sc> is close to <sc>150 km³.</sc> Meanwhile, the joint operation of the Yangtze River Basin in 2021 indicated a total regulation capacity of <sc>106.6 km³</sc> and a total flood control capacity of about <sc>69.5 km³</sc> of 47 control reservoirs. Third, lake basins play an important role in the national economic development and food security. Of China’s nine major commercial grain production areas, seven are located in Jianghuai lakes zone and northeast plain lake zone. Fourth, lakes are one of the richest biodiversity ecosystems on earth. Among the 62 international important wetlands in China, there are 26 lake wetlands including Lake Poyang, Lake Dongting, Lake Qinghai etc accounting for 41.9%. Fifth, lake fishery plays an important role in China’s fishery production evidenced by China Fishery Statistical Yearbook 2021, which showed that the aquaculture area of lakes was 2186662 hectares, accounting for 42.7% of the national freshwater aquaculture area and 30.8% of the national aquaculture area in 2019. Sixth, lakes have important tourism value and contribute to beautiful business cards of many cities. Among the 45 national tourist resorts in China, there are 15 lakes tourist resorts, accounting for one third, highlighting the rich tourism value resources of lakes. Seventh, lakes are an important part of the northern ecological security barrier. Lake Hulunhu, Lake Wuliangsuhai, Lake Daihai, Lake Qinghaihu, Lake Bositenghu, and Lake Aibihu act as the key nodes of northern ecological security barrier. In addition, lakes play a big role in energy storage and power generation, agricultural irrigation, inland navigation, carbon sequestration and pollution reduction and regional climate regulation. Large numbers of lakes with different types are widely distributed throughout China exhibiting obvious regional differentiation. Moreover, lakes are facing many ecological and environmental problems which reduce their value of providing ecological services. Specifically, eutrophication and cyanobacteria bloom have not been fundamentally alleviated, which threats the water quality safety of lake drinking water sources. The aquatic vegetation of the lakes is seriously degraded, which weaken their purification capacity and reduce their biodiversity. The synergistic effects of rapid climate change and intense human activities cause either lake flooding, shrinkage or salinization. Warm and humid climate results in a rapid expansion of the lakes on the Tibetan Plateau, which significantly increase the risk of glacial lake outburst. Aiming the above-mentioned ecological and environmental problems, this study puts forward the strategies and countermeasures for lake protection and management including lake-basin system studies, scientific regulation of water resources, cyanobacteria bloom early warning and control, national lake ecological restoration project, basin industrial structure upgrading, and lake protection legislation, which will promote the improvement of lake environmental and the construction of beautiful lakes.

Glacier Contributions to River Discharge During the Current Chilean Megadrought

AbstractThe current Chilean megadrought has led to acute water shortages in central Chile since 2010. Glaciers have provided vital fresh water to the region's rivers, but the quantity, timing and sustainability of that provision remain unclear. Here we combine in‐situ, remote sensing and climate reanalysis data to show that from 2010 to 2018 during the megadrought, unsustainable imbalance ablation of glaciers (ablation not balanced by new snowfall) strongly buffered the late‐summer discharge of the Maipo River, a primary source of water to Santiago. If there had been no glaciers, water availability would have been reduced from December through May, with a 31 ± 19% decrease during March. Our results indicate that while the annual contributions of imbalance ablation to river discharge during the megadrought have been small compared to those from precipitation and sustainable balance ablation, they have nevertheless been a substantial input to a hydrological system that was already experiencing high water stress. The water‐equivalent volume of imbalance ablation generated in the Maipo Basin between 2010 and 2018 was 740 × 106 m3 (19 ± 12 mm yr−1), approximately 3.4 times the capacity of the basin's El Yeso Reservoir. This is equivalent to 14% of Santiago's potable water use in that time, while total glacier ablation was equivalent to 59%. We show that glacier retreat will exacerbate river discharge deficits and further jeopardize water availability in central Chile if precipitation deficits endure, and conjecture that these effects will be amplified by climatic warming.

Numerical analysis of propagation characteristics of sediment peak and its implications for the Xiluodu Reservoir

Abstract Reservoir construction alters the hydrodynamic characteristics of the flow and sediment regimes, resulting in the enhancement of the hysteresis effect between the flood and sediment peaks. In this study, a 3D numerical model was adopted to investigate the propagation characteristics of sediment peak and the management method of reservoir sediment release. The results indicate that the incoming flow rate and the storage water level have a great influence on the propagation time of the sediment peak, and the incoming flow rate has a large influence on the attenuation rate of the sediment peak while the storage water level and the incoming suspended sediment concentration have a small effect on the attenuation rate of the sediment peak. An empirical formula based on inflow rate, water level elevation, water depth and length and storage capacity of reservoirs was established to predict the lag time between the flood and sediment peaks. The asynchronous movement between the incoming flood and sediment peaks has a clear influence on the propagation characteristics of the sediment peak. The hysteresis effect of the flood and sediment peaks can be fully utilized by reservoir managers to reduce reservoir sedimentation and improve sedimentation distribution.

Enhancement of flushed sediment in pressure flushing using inclined plates upstream of orifice

Abstract Pressure flushing is a common technique to restore the storage capacity of reservoirs. However, the low quantity of flushed sediment remains a drawback of pressure flushing. Experimentally, the present study used inclined plates upstream of the bottom outlet to increase the flushed sediment in pressure flushing. The variables included the plate width (B), the angel between the vertical line at the outlet center and the normal vector of the inclined plate (α), radial distance of the inclined plates from the orifice center (R), and outlet discharge (Q). The results showed that the flushed sediment significantly enhanced; the quantity of flushed sediment for B = 6.3 cm, α = 60°, R = 8.5 cm, and a Q = 8.34 L/s was 19 times as large as that in the reference test (i.e., without plates). Furthermore, the length, width, and depth of the scour cone in the presence of inclined plates were 3, 2.3, and 3.3 times as high as those in the absence of the inclined plates. Also, equations were developed to predict the volume and dimensions of the scour cone in the presence of inclined plates based on the experimental data. Finally, the importance of the variables was determined using a sensitivity analysis method. Between all considered parameters in this study, the plate distance from the outlet was found to have the highest effect and the plate inclination the lowest effect (three times) in increasing the flushed sediment through the orifice.

Analysis of runoff variation and driving factors in the Minjiang River Basin over the last 60 years

Abstract An absolute essential for effective water resource management and ecological restoration is knowing the temporal and spatial variation of runoff. The objective of this study was to determine the spatial and temporal changes in runoff at the main hydrological stations along the Minjiang River and the Dadu River between 1961 and 2016 using the non-parametric Mann-Kendall test and annual variation analysis. Canonical correspondence analysis and regression analysis were used to determine the contribution of anthropogenic disturbance, vegetation, and climatic conditions to runoff change. The runoff at each station of the Minjiang River showed a clear decreasing trend, whereas the decreasing trend of the Dadu River was not significant. Moreover, the discharge at the Shawan (SW) station upstream of the Dadu River and the Gaochang (GC) station downstream of the Minjiang River have changed significantly during the flood and non-flood seasons since 2000, while the discharge at other stations has not changed significantly. The average annual runoff in the non-flood season at SW and GC in 2011–2016 increased by approximately 26.21 and 36.47%, respectively, compared with 1961–2010. Anthropogenic disturbance, vegetation, and climatic conditions in the Minjiang River Basin accounted for 76.24, 13.62, and 10.14%, respectively, of the runoff change in the basin. Water consumption and total reservoir capacity were the specific factors most affecting runoff change in the basin, accounting for 15.10 and 13.94%, respectively, of the changes in runoff. The research can provide important support for the ecological restoration of Minjiang River Basin and Yangtze River Basin.

Erosion Risk Assessment for Prioritization of Conservation Measures in the Watershed of Genale Dawa-3 Hydropower Dam, Ethiopia

Sedimentation is a leading global problem that affects the environment and dams by reducing the live storage capacity of reservoirs and the life expectance of dams. Hence, prioritizing watersheds according to the risk of soil loss is crucial for extending the useful life of dams and reservoirs. The objectives of this study were to assess sediment flow in the Genale Dawa-3 reservoir, identify subbasins that are prone to soil erosion, and evaluate the impact of different management practices on minimizing sediment yields by using the Soil and Water Assessment Tool (SWAT) model. The SWAT model was calibrated and validated by observed streamflow and sediment data based on the SUFI-2 algorithm by SWAT-CUP, and its performance was assessed. The model simulated the average annual sediment yield; the input to the reservoir was 16.83 ton/ha/yr for the period of 1990–2015. From a total of 31 subbasins, 12 were categorized from high to very severe (11–60 ton/ha/yr) sediment-yielding subbasins and selected for sediment management. The simulated scenarios showed that the average annual sediment reductions at critical erosion hot spots in subbasins after the application of filter strips, soil/stone bund, terracing, and contour farming were 35.03%, 66.54%, 80.88%, and 53.11%, respectively. Therefore, this study concluded that reducing sediment yield by implementing terracing in critical areas at risk of soil erosion was more effective than other soil conservation measures. Overall, this research can help planners and decision-makers to implement appropriate soil conservation measures in the most erosive subwatersheds in order to extend the useful life of the Genale Dawa-3 hydropower dam and reservoir.

Influence of Karst Reservoir Capacity on Flood in Lijiang Basin Based on Modified HEC-HMS through Soil Moisture Accounting Loss

The objective of this work was to modify the HEC-HMS flood prediction for the karstic watershed of the Lijiang River, South China, through the quantitative inclusion into the model of the available reservoir capacity of karst (ARCK) as a case study. Due to the complexities caused by hidden drainage networks in karst hydrology, as a new approach, soil moisture accounting loss was used to reflect the ARCK in flood forecasting. The soil moisture loss was analyzed against daily rainfall runoff data across 1.5 years by using an artificial neural network via phyton programming. Through the correlations found among the amounts of soil moisture and river flow fluctuations in response to precipitation and its intervals, coefficients were introduced to the model for output modifications. ARCK analysis revealed that while heavy rainfalls with longer intervals (i.e., 174 mm/2d after 112 days of the dry season) may not cause considerable changes in the river flow magnitude (0.1–0.64 higher owing to high ARCK), relatively small rainfalls with higher frequency (i.e., 83 mm/4d during the wet season) can cause drastic raise of river flow (10–20 times greater at different stations) due to lower ARCK. Soil moisture accounting loss coefficients did enhance the model’s simulated hydrographs accuracy (NSE) up to 16% on average as compared to the initial forecasting via real data. However, the modifications were valid for flood events within a few years from the soil moisture observation period. Our result suggested that the inclusion of ARCK in modeling through soil moisture accounting loss can lead to increased prediction accuracy through consistent monitoring.

The Bengal Water Machine: Quantified freshwater capture in Bangladesh.

Global food security depends on the sustainability of irrigated agriculture. Rising groundwater withdrawals from seasonally humid, alluvial plains across tropical Asia have enabled dry-season rice cultivation. This groundwater pumpage increases available subsurface storage that under favorable conditions amplifies groundwater replenishment during the subsequent monsoon. We empirically quantified this nature-based solution to seasonal freshwater storage capture described as the "Bengal Water Machine," revealing its potential and limitations. On the basis of a million piezometric observations from 465 monitoring wells, we show that the collective operation of ~16 million smallholder farmers in the Bengal Basin of Bangladesh from 1988 to 2018 has induced cumulative freshwater capture that volumetrically (75 to 90 cubic kilometers) is equivalent to twice the reservoir capacity of the Three Gorges Dam.