Ecological Water Level Research Articles

Sustainable groundwater regulation in typical irrigation areas of inland river basins based on ecological indicators and the MIKE-SHE hydrological model

Study regionThe study area is located in the Nukus irrigation area on the lower reaches of the Amudarya River in Uzbekistan. Study focusThe extensive agricultural land development has introduced a substantial amount of water resources into the irrigation area, leading to a significant rise in regional groundwater levels. Quantifying regional groundwater resource issues and achieving sustainable groundwater management under conditions of high spatiotemporal heterogeneity are key scientific issues for regional ecological protection. Thus, this study used the concept of ecological water level to quantify groundwater issues, used the MIKE-SHE hydrological model to conduct scenario simulations, formulated and subsequently evaluated a groundwater regulation plan with spatiotemporal attributes. New hydrological insights for the regionRegional sustainable development groundwater level should be within the range of 1.78–2.78 m. During the irrigation and non-irrigation periods, the groundwater levels in approximately 84.3 % and 72.2 % of the study area respectively exceeded the upper and lower ecological water level limits. Under the background of gradually increasing groundwater fluctuations, it will pose a serious threat to regional ecology. Therefore, this paper established a monthly-scale groundwater zoning control plan, which can make the area of regional groundwater within the ecological water level reach 87.53 %. All research not only contributes to the protection of the local ecological environment but also provides valuable insights for water resources management in other regions.

Water Resources Management for Multi-Source Ecological Restoration Goals in an Oasis: A Case Study of Bohu County Irrigation Area in Xinjiang, China

Oases in arid regions consist of river–lake–groundwater systems characterized by complex hydrological cycles and fragile ecosystems. Sustainable water resource management, aimed at multi-source ecological restoration, is crucial for oasis ecological protection and represents a current research challenge. This study focuses on the Bohu irrigation area, using ecological water levels, the MIKE-SHE hydrological model, and the water balance equation to propose a multi-objective groundwater and surface water regulation scheme that meets both the ecological safety requirements of the irrigation area and the ecological water demands of the Small Lake. Key findings include the following: (1) The regional ecological water level ranges from 1.69 m to 4 m, with about 74% of the area exceeding this range, threatening local ecology. (2) The proposed regulation method adjusts 91.25% of areas exceeding the ecological water level to within the acceptable range. (3) Under various planting scenarios, the minimum water distribution from the west branch of the BLSM water diversion hub should be 824.632 × 106 m3/a to meet Small Lake ecological demands. When this volume exceeds 831.902 × 106 m3/a, both groundwater regulation and Small Lake ecological demands are satisfied. This paper quantifies the water cycle mechanisms in complex hydrological interaction areas, providing specific solutions to regional ecological problems, which holds significant practical relevance.

Ecological water level regulation based on aquatic plant restoration in large reservoirs: A case study of Wangying Reservoir

The regulation of water levels based on water level requirements at different life-cycle stages of aquatic plants is a crucial measure for the restoration of aquatic plants. Based on the current situation of aquatic plants in the reservoir and the requirements for the water level of aquatic plants in different life cycle stages, the present study proposes the best ecological water level under different plant coverage restoration targets for the Wangying Reservoir. There were 184 species of aquatic plants in the Wangying Reservoir belonging to 142 genera in 61 families and 32 orders, with an average biomass of 2.35 kg/m2 and average density of 227 plants/m2. The total coverage of aquatic vegetation was 26 %, which included 15 % hygrophytes and emergent plants and 11 % submerged plants. The hygrophytes, emergent, and submerged plants have experienced discrepant life history stages and water level requirement even for the same life history stage. The fluctuations in the water level required for hygrophytes and emergent plants (2 m) were relatively more stable across different life cycle stages than for submerged plants (5 m). These results offer valuable guidance for the recovery of aquatic plants and reservoir management for the lentic water bodies.

Spatio-temporal heterogeneity of ecological water level in Poyang Lake, China

Anthropogenic activities and climate change have caused physical and ecological changes in lakes and have aggravated water level fluctuations, which are essential factors to consider for nutrient import, ecological protection, and biodiversity maintenance. Maintaining water levels within a reasonable range is essential for maintaining lake function and ecological health, because ecosystem stability is compromised when water level fluctuations exceed specific thresholds. Thus, the ecological water level (EWL) is an important index for maintaining aquatic habitats and biodiversity. A method for quantifying the EWL of lakes based on hydrological statistical analysis was constructed to bridge the gaps in existing studies, considering both the hydrological alteration and spatio-temporal heterogeneity of water level fluctuations. Taking Poyang Lake as an example, which has recently attracted increasing global attention owing to its water level alterations and subsequent ecological problems, the applicability of the method and rationality of the results were verified. The results indicate that hydrological alteration occurs at the water level of the representative stations, which is jointly affected by climate change and anthropogenic activities in this region. For instance, the construction and operation of the Three Gorges Project affected the water level alteration at Hukou and Xingzi station, and drought further aggravated that of Xingzi station. The calculated EWL of Poyang Lake showed obvious spatio-temporal heterogeneity, which is consistent with the topographic, geographical, and climatic characteristics of the basin. And the rationality of the EWL in this study was verified through literature reviews and satisfiability of characteristic species requirements. The proposed EWL calculation method is simple and feasible with easy data acquisition, strong universality, and broad application prospects, offering a scientific basis and quantitative reference for water resource management and lake ecosystem protection.

Research on the Reconstruction of Aquatic Vegetation Landscape in Coal Mining Subsidence Wetlands Based on Ecological Water Level

The eastern region of the Huang-Huai area is vital for China’s coal production, with high water table mining causing significant surface subsidence and the formation of interconnected coal mining subsidence wetlands. Restoring these wetlands is crucial for biodiversity, environmental quality, and sustainable development. Aquatic vegetation plays a crucial role in wetland ecosystems, underscoring its importance in restoration efforts. Understanding and managing water level fluctuations is essential due to their impact on vegetation. This study examines the Qianshiliying coal mining subsidence wetland in the Yanzhou Mining Area, China, with the goal of devising a water level regulation plan based on the minimum ecological water level to improve the growth and recovery of aquatic vegetation. The research delves into landscape ecological restoration techniques for aquatic vegetation in coal mining subsidence wetlands in the eastern Huang-Huai region, emphasizing the importance of water level management. The results reveal that the minimum ecological water level in the Qianshiliying coal mining subsidence wetland is 32.50 m, and an area of 78.09 hectares is suitable for the reconstruction of aquatic vegetation. This paper utilizes lake morphology, minimum biological space, and water level demand methods for aquatic plants in the landscape to promote restoration of coal mining subsidence wetlands. A notable strength of this approach is its ability to quantitatively predict the survival range and area of aquatic vegetation in these wetlands, enabling a more scientifically informed restoration of ecological balance and promoting landscape ecological restoration in the eastern Huang-Huai region.

Effect of groundwater decline on plant induced by tunnel excavation and calculation of ecological water level based on SPAC model

Effect of groundwater decline on plant induced by tunnel excavation and calculation of ecological water level based on SPAC model

Determination and analysis of groundwater ecological level in Changling County

In order to determine and analyze the groundwater ecological level in Changling County, a total of Landsat 8 series remote sensing images from 2017 to 2021, buried depth data of 51 groundwater observation Wells and 47 phreatic salinity detection data in 2021 were collected. Based on the field investigation and laboratory experiment, the spatial and temporal changes of groundwater level and vegetation coverage in the study area from 2013 to 2017 were determined by using remote sensing technology (the Environment for Visualizing Images) and geographic information system. Through the analysis of the vegetation coverage ratio and the relationship between the groundwater depth and diving salinity, we determine the appropriate growth of vegetation in the study area of diving level and diving salinity water. The results showed that from 2017 to 2021 in the average groundwater level and vegetation cover degree decline year by year, the study area northwest shallow depth of groundwater, vegetation cover degree better, however, in the central and eastern regions, the groundwater depth is larger and the vegetation coverage degree is poor. When the depth of local groundwater is 3.3–4.5 m and the phreatic salinity is less than 0.85 g/L, the ecological water level and phreatic salinity are suitable for vegetation growth in the study area. When the depth of local water is less than 3 m, soil salinization occurs in the surface soil near the lake marsh. When the depth of local water was greater than 8.4 m, the phenomenon of soil desertification appeared in some areas of central China.

Determination of the ecological water levels in shallow lakes based on regime shifts: A case study of China's Baiyangdian Lake

Water level management is an effective way to promote ecological restoration of shallow lakes. However, efforts to achieve an ecologically suitable water level often emphasize keeping water above the minimum water level and reducing water level fluctuations, but ignore the purpose of maintaining the ecosystem's stability and health. In this paper, we developed a PCLake model to determine the optimal monthly ecological water level with the goals of stably achieving clear water and maintaining ecosystem health. We simulated the regime shifts between eutrophic and oligotrophic in China's Baiyangdian Lake, and determined that the critical P loadings during eutrophication and oligotrophication were 1.57 and 0.835 mg/m2/day, respectively. The annual and monthly optimal water levels ranged from 7.8 to 8.6 m and from 7.6 to 8.6 m, respectively. Our results provide a scientific basis for the ecological restoration of Baiyangdian Lake.

Influences of anthropogenic acids on carbonate weathering and CO2 sink in an agricultural karst wetland (South China)

Carbonate minerals are the largest carbon (C) reservoir on earth. Quantitative assessment of carbonate weathering and CO2 sink flux caused by anthropogenic acids in karst wetland regions is imperative to improve understanding of the hydrogeochemical evolution and global C cycle in karst ecosystem. In this study, a typical field observation was conducted in the Huixian karst wetland (HKW) in South China. The hydrogeochemical and isotopic (δ15N-NO3–, δ18O-NO3–, and δ13CDIC) analyses combined with the MixSIAR model and stoichiometric coefficients were used to quantitatively estimate the influence of H2CO3, HNO3 and H2SO4 on carbonate weathering and CO2 sink flux. The results obtained showed that anthropogenic HNO3 and H2SO4 affect carbonate weathering in the HKW, evidenced by the significant correlations between hydrogeochemical parameters and δ13CDIC value. The quantitative results showed high contributions of HNO3 and H2SO4 to carbonate weathering in karst groundwater, with contribution ratio values of 20.91 ± 19.29 and 21.69 ± 26.88%, respectively. Besides karst water over-exploitation, this finding suggested that these anthropogenic acids were also an important cause of a decrease in ecological water levels, resulting in the shortage of karst water resource and degradation of wetland ecosystem. Moreover, the involvement of anthropogenic acids in the natural chemical weathering has significantly decreased the CO2 sink flux by 11.23 ± 7.94 and 41.60 ± 30.24% for surface water and groundwater, respectively, thereby potentially affecting the karst C cycle and global climate change. This present study provided an integrated quantitative approach for estimating the influence of H2CO3, HNO3, and H2SO4 on carbonate weathering and CO2 sink in karst wetland regions. Our study highlighted that the effects of anthropogenic acids on carbonate weathering need to be considered in future studies on the restoration of wetland ecosystems, particularly in intensive agricultural study areas.

Effects of Groundwater Level Control on Soil Salinity Change in Farmland around Wetlands in Arid Areas: A Case Study of the Lower Reaches of the Shiyang River Basin, China

The farmland around wetlands in the lower reaches of an arid area is susceptible to salinization. To explore the effects of the groundwater level control at an irrigation cycle scale on the salt concentration of the topsoil solution, this study carried out groundwater level control and irrigation experiments using the intelligent groundwater control and in-situ field monitoring system (also referred to as the groundwater control system) in the experimental base for groundwater control of the Shiyang River basin. On this basis, this study compared and analyzed the changes in groundwater depth, soil salinity, soil moisture content, and total water potential in zones with and without groundwater control (also referred to as the control and non-control zones, respectively). Results show: (1) When the groundwater depth increased by about 50 cm under the influence of the groundwater control system, the salt accumulation layer of the soil bulk shifted downward by about 20 cm, and the topsoil bulk salt (at a depth of less than 40 cm) decreased to below 5.0 g/kg; (2) In summer, the pore water electrical conductivity (ECp) of the topsoil in the control and non-control zones exhibited alternating rapid decreases and slow increases. In the concentration stage of the soil solution, the ECp of the topsoil in the non-control zone had significantly higher increased amplitude than that in the control zone, especially 3–8 days after irrigation. At this stage, the ECp of the topsoil in the control and non-control zones increased in two (slow and rapid increase) and three (slow, rapid, and fairly rapid increase) periods, respectively; (3) At the concentration stage of the topsoil solution, both the moisture content and solution salt content of the topsoil in the control zone were in a negative equilibrium state, with the absolute values of the equilibrium values gradually increasing. In contrast, the moisture content and solution salt content of the topsoil in the non-control zone were in negative and positive equilibrium, respectively, with the absolute values of their equilibrium values gradually increasing. The groundwater control system can mitigate the concentration rate of the topsoil solution by increasing the groundwater depth and influencing the water and salt equilibrium of the topsoil solution, which can create a suitable topsoil salt environment for crop growth. This study is of great significance for determining an appropriate ecological water level interval and optimizing groundwater control strategies for farmland around wetlands.

An integrated connectivity diagnostics and dependency analysis framework for supporting water replenishment management

An in-depth investigation on hydrological connectivity and its relationships with water level are fundamental for regional water replenishment management. In this research, an integrated connectivity diagnostics and dependency analysis framework (ICDDAF) was developed for determining the optimal ecological water level in Baiyangdian Wetland, North China. It consisted of two core modules: hydrological connectivity diagnostics (HCD) and hydrological connectivity–water level coexistence analysis (HC–WLCA). The results were as follows. 1) In the HCD module, remote sensing coupling geostatistical connectivity function methods can accurately evaluate the hydrological connectivity considering the directional difference and the validity of distance range. For intra–annual variations, the hydrological connectivity was relatively good in March at the monthly scale, spring at the seasonal scale and the west–east direction, while relatively weak in September and summer, which were related to the periodic characteristics of vegetation growth, overall terrain and flow direction. For inter–annual variations, it was generally weak and showed a downwards, then upwards and finally downwards trend. 2) In the HC–WLCA module, Multivariate Copula Analysis Toolbox was innovatively adopted to describe the coexistence relationships of hydrological connectivity and water level. Beta and generalized Pareto distributions were selected as the optimal marginal distributions for hydrological connectivity and water level indicators respectively, and Frank copula was determined as the optimal joint distribution function; the modelling uncertainty in the coexistence relationships was focused. 3) The water level of 7 m was determined as the optimal ecological water level for maintaining good hydrological connectivity and restoring ecological environment. Considering the coexistence relationships of hydrological connectivity and water level, such an ICDDAF can provide a new perspective for efficient adjustments of water levels based on hydrological connectivity pattern variations under different water replenishment schemes, aiming to achieve ecological restoration of wetlands.

Multiple-criteria determination and preventive measures of river ecological water level in the Northern Jiangsu plain

It is vital to employ efficient methods to calculate and determine the threshold of river ecological flow. These methods help to get the river ecological status control countermeasures in the plain river networks and construct a flawless long-term mechanism of ecological flow control (water level). According to the river's current environment and the actual circumstances surrounding its operation and administration, the upper, middle, and lower reaches make up the three sections of the Zong-Liutang River in the Plain of Northern Jiangsu. Furthermore, the ecological water level governing factor for each reach was analyzed and studied. The ecological water level threshold in the upper and lower reaches of the Zong-Liutang River adopted the specified values of Jiangsu Provincial Department of water resources. The threshold of the middle reach was thoroughly analyzed by using the determination method with multi-criteria, which consisted of the hydrological and hydraulic methods (including yearly minimum water level with a 90% assured rate method; wetted perimeter method; minimum monthly average water level method), aquatic living conditions method, and river landscape entertainment factor method. Taking into account the hydrological and hydrodynamic characteristics, observed hydrological data conditions of rivers, and the actual operation rules of rivers and water projects regulations in the Northern Jiangsu plain. Through comparing and contrasting actual operation and management plans, the target values of the ecological water level for the river's upper, middle, and lower reaches were 17.4 m, 8.96 m, and 7.5 m, respectively. Based on the river's ecological water level's control value, which was found through a thorough analysis, and the river's real operation and management conditions, specific measures to protect the river's ecological water level were suggested. These included developing a perfect and workable ecological flow control method, speeding up the development of an ecological water level goal assurance early warning system, and an ecological flow and inlet system.

Rational Allocation of Water Resources in the Arid Area of Northwestern China Based on Numerical Simulations

Adding a series of surface-water transfer projects still cannot solve the current water shortages in the arid area of northwestern China. Selecting a rational allocation plan for the water resources is the key to coordinating water use for the national economy and ecological environment. In this study, taking the Wuwei Basin as the study area, long-term data of source-sink terms from 2007 to 2018 were analyzed. Following the calibration and validation of the numerical simulation model of the groundwater system, the data was highly fitted. Based on this model, the groundwater system balance, water level variations, and suitable ecological water level area in 2050 under four water resource allocation plans were compared. Under plan 4, the groundwater resources change from an average decrease of 7656.4 × 104 m3·yr−1 from 2007 to 2018, to an increase of 4624.6 × 104 m3·yr−1 in 2050, which means the groundwater systems are almost in a positive balance state. Compared with 2018, the water level with small groundwater depth drops by 2.2–5.7 m, while that with large groundwater depths steadily rises by 2.7–8.6 m. In addition, it can maintain the 9 km2 natural oasis wetland area and the 116 km2 well-growing natural vegetation area, which can effectively promote the benign evolution and efficient, balanced sustainable development of the regional water resources, economy, and ecological environment.

Ecohydrological Variation and Multi-Objective Ecological Water Demand of the Irtysh River Basin

Hydrological processes regulate the ecological processes of a basin. Climate change and anthropological activities lead to changes in the natural hydrological process of rivers, whereas variations in hydrological processes can disrupt the stability of ecosystems, resulting in various ecological challenges. Quantitative evaluation of ecological water demand and its key components can play a key role in the sustainable development of ecosystems. The studies of ecohydrological variation and multi-objective ecological water demand are of great significance for ecological protection and remediation due to the unique characteristics of each river basin and diverse ecological protection objectives. This study identified ecohydrological variation in ecosystems, focusing on the Irtysh River Basin as a case study, and improved methods for ecological water demand of valley forests and grasslands in terrestrial ecosystems and for the ecological water level of lake ecosystems. The results demonstrated that: (1) a drastic decrease in the annual average river flow of the basin and significant changes in ecohydrological characteristics can lead to reduced biomass; (2) the ecological water demand of valley forests and grasslands during the critical ecological stage (April–September) was 521 million m³, with 52.4% of total demand occurring in June and July. The minimum ecological water levels of the Burultokay and Jili lakes were 478.66 m and 480.66 m, whereas the maximum levels were 482.80 m and 483.20 m, respectively; (3) ecological regulation based on catchwork irrigation technology can create hydrological processes that meet the water demands of valley forests and grasslands and achieve remediation of the terrestrial ecosystem. The ecological water levels and the ecosystem balance of the Burultokay and Jili lakes can be maintained by optimizing the replenishment flow from the Irtysh River to the Burultokay Lake under different precipitation levels. This study can act as a reference for the ecological protection and remediation of the Irtysh River Basin and similar ecosystems globally.

Sustainable high-intensity backfill coal mining method: feasibility assessment for ecologically fragile areas of Western China

ABSTRACT High-yield coal mining and ecological environment protection are the main aspects of the sustainable development of ecologically fragile mining areas in Western China. This paper briefly describes the development and current situation of solid filling coal mining in China, puts forward a green and sustainable filling coal mining method providing a maximum annual treatment capacity of waste gangue of 2 4 million tons, and analyzes the mechanical compaction properties of solid waste gangue, eolian sand, and loess in these areas. Taking a Coal Mine in Inner Mongolia, China, as an example, the effects of three key indices, namely mining height, face width, and backfill materials’ compaction ratio (BMCR) on the subsidence, horizontal deformation, horizontal movement, inclined deformation, and curvature of Quaternary aquiclude are studied. At a mining height of 3 m and BMCR = 80%, the maximum aquifer subsidence is below 168 mm. Based on the surface vegetation growth capacity analysis, the design principle of controlling the SBM key parameters by the ecological water level threshold is substantiated. The results show that the mining height and the BCMR of goaf are the key control indices affecting the stability of Quaternary aquifers, the evolution of ecological water level, and the production of surface vegetation. Combining the underground intelligent dry coal preparation and in-situ filling coal mining technology with a reasonable adjustment of the above parameters, the ecological environment protection can be realized for the whole life cycle of local coal seam mining in the areas under study.

Optimum ecological water level of water-carrying lake based on the relationship between water quality and water level

适宜的生态水位能够反映湖区生态系统的多种需求，是湖泊长期稳定健康运转的基本保障. 目前湖泊适宜生态水位的推求大多侧重恢复天然水位情势. 然而过水型湖泊承担着防洪、供水、航运等多种功能，频繁的人类活动导致湖泊水位情势异常复杂. 同时随着社会经济的快速发展，水质恶化对过水型湖泊生态系统造成了较大的负面影响，仅恢复天然水位情势难以反映过水型湖泊的生态需求. 因此，在IHA-RVA法的基础上，本文针对过水型湖泊吞吐性强的特点，利用水质-水位二元响应关系系统地提出了一套逐月修正过水型湖泊适宜生态水位阈值，并确定适宜水位变动率的方法. 以洪泽湖为应用实例，结果表明：1)根据湖泊水文情势和入湖污染物变化情况，湖泊调度周期可以划分为平水期(1—4月)、泄水期(5—6月)、蓄水前期(7—9月)和蓄水后期(10—12月)；2)各时期内，洪泽湖水位和水质呈现较强的相关性，其中平水期、泄水期和蓄水后期水质均随着水位上升而下降，平均Pearson系数达-0.77，仅在蓄水前期水质随水位上升而改善；3)现阶段洪泽湖的自净能力和污染物滞留比例竞争关系激烈，逐月适宜生态水位阈值为：12.92~12.99、12.79~12.99、12.84~12.99、12.86~12.99、12.71~12.89、12.39~12.63、11.97~12.93、12.50~13.07、12.65~13.26、12.90~13.04、12.90~13.04、12.90~13.04 m，除蓄水前期外，基于水位水质关系修正的适宜生态水位范围较IHA-RVA法计算的天然水位范围缩小了73.4 %. 总体而言，基于本文方法设计的湖泊适宜生态水位不仅可以满足生态系统对于水体大小的需求，一定程度上也可以体现湖泊生态系统对于水质的要求，为洪泽湖等过水型湖泊的生态调度、水资源管理提供科学依据.;The optimum ecological water level (OWL) guarantees stable and healthy operation of the lake in the long term by meeting various needs of the lake ecosystem. Previous studies on OWL mainly focused on restoring natural water level regime. However, water-carrying lakes have complicated water lever regimes resulted from flood control, water supply, shipping and other functions. Meanwhile, the water quality was further deteriorated due to rapid economic development. Consequently, the previous methods could not meet all the ecological needs of water-carrying lakes. Basing on IHA (indicators of hydrological alteration)-RVA (range of variability approach) method and relationship between water quality and water level, this paper proposed a method for identifying of the threshold of monthly OWL and determining the OWL variation of water-carrying lake. Taking Lake Hongze as an example, the results indicate that: 1) The lake regulation cycle can be divided into flat period (January-April), discharge period (May-June), early storage period (July-September) and late storage period (October-December) from the angle of hydrological regime and pollution into the lake. 2) There's a strong correlation between water quality and water level in each period as water quality improves with water level rising during the early storage period and deteriorates in other periods (Pearson coefficient was -0.77). 3) Due to the competition between the lake's self-purification capacity and pollutant retention ratio, the monthly OWL threshold from January to December is: 12.92-12.99, 12.79-12.99, 12.84-12.99, 12.86-12.99, 12.71-12.89, 12.39-12.63, 11.97-12.93, 12.50-13.07, 12.65-13.26, 12.90-13.04, 12.90-13.04, 12.90-13.04 m, respectively. The range of OWL modified by the relationship between water level and water quality is reduced by 73.4 % compared with the results of IHA-RVA method except in the early storage period. In general, the OWL designed by methods in this paper can reflect the requirements of lake ecosystem for water quantity and water quality to a certain extent, and provide scientific basis for the ecological regulation and water resource management of Lake Hongze and other water-carrying lakes.

Water surface photovoltaic along long-distance water diversion projects and its co-benefits

As the world encounters insufficient fossil energy and worsening environmental pollution, the significant potential of water surface photovoltaic (WSPV) systems and the remarkable benefits are crucial to promoting cleaner production and sustainable development. This paper proposes installing overhead WSPVs along the open channels of long-distance water diversion projects (WDPs), creating new opportunities for the adaptive traceability and utilization of energy–water resources. A multi-objective decision model for the feasibility evaluation of WSPVs is presented and applied to typical WDPs in China to demonstrate the effects of this modeling framework and explore the co-benefits of WSPV systems. The results indicate that: (1) it is economically and technically feasible to install WSPVs over MLSNWDP with a suggested tilt angle range of 10°–12°; (2) the proposed WSPVs in the eight typical projects evaluated using the decision model with a capacity of 29,486 MW can convert 37,263 GWh of electricity at a 12° tilt angle while saving 3.19 × 108 m3 of water annually; (3) the adaptive utilization of the saved water and electricity can increase the ecological water level guarantee rate of Baiyang Lake by 12.64%, alleviating potential eco-environmental problems. Moreover, a recommended coverage rate of 50% is proposed to inhibit algae outbreaks. Overall, this research demonstrates the technical and economic feasibility of the construction of WSPVs along WDPs and the co-benefits to address challenging research questions on the sustainable development of energy–water resources.

The impacts of water level fluctuations of East Dongting Lake on habitat suitability of migratory birds

Understanding responses of habitat suitability of migratory birds to the water level is significant for providing countermeasures of wetland protection. East Dongting Lake serves critical wintering habitat for migratory birds along the East Asian-Australasian Flyway. However, the response relationships between the water level and the weighted usable area (WUA) for migratory birds remain largely unknown. Therefore, we established a habitat suitability model of migratory birds based on the Digital Elevation Model (DEM) and Normalized Difference Vegetation Index (NDVI) and recognized the change of WUA by comparing the transition of land-cover of similar hydrologic years before and after the operation of Three Gorge Dam (TGD). The results demonstrated that (1) the ecological water level of migratory birds in East Dongting Lake is 20.47–21.55 m. (2) Compared with the pre-TGD period, the start date of the ecological water level advanced by 25 days, the duration of the ecological water level increased by 16 days, and the fluctuation range of water level was more concentrated near the ecological water level, indicating that the TGD provides benefits for the migratory birds. (3) The most prominent transition among changes of land-cover was that the Reed beach (RB) (155.07 km2) and Marsh land (ML) (150.66 km2) changed to Tender Marsh land (TML) during dry hydrologic years, and the RB (171.90 km2) and ML (174.30 km2) changed to TML during normal hydrologic years. The findings show that water level changes habitat suitability of migratory birds by changing vegetation distribution at different elevations.

A new strategy for environmental flow management by using the remote sensing method

Implementing environmental flow (e-flow) is a key measure for restoring and managing river ecosystems. However, illegal competition for water resources or alterations of the natural flow regimes can result in the shortage of e-flow and degradation of river ecosystems. Monitoring and managing e-flow is increasingly critical and necessary in some regions. In this study, a monitoring method and guarantee rate evaluation system for e-flow was developed using remote sensing and hydrological data of the Jiulongjiang and Taizi rivers, China. The results indicated that the monthly e-flow varied with the water demand, ranging from 12.60 m3/s to 189.50 m3/s and 3.50 m3/s to 57.70 m3/s at Punan station, Jiulongjiang River and Tangmazhai station, Taizi River, respectively. Moreover, e-flow accounted for 24% of the average annual runoff for both rivers, which indicated that the ecological environment was in a fair or degrading state. Moreover, the guarantee rate of e-flow at Tangmazhai station is 100%, which indicates that the e-flow meets the requirements and is consistent with the results of the e-flow guarantee rate calculated by the actual measured flow. The guarantee rate of e-flow at Punan station is 0%, and exhibits a certain error with the actual measurement results; this is because a rectangular section exists between the maximum and minimum ecological water levels, which corresponds to a small change in the ecological water surface width of 0.9 m. The low-resolution remote sensing used in this study cannot capture this change, thus causing a large error in the measured result; however, this issue can be addressed by improving the remote sensing technique. The results showed that the monitoring method and guarantee rate evaluation of e-flow can be adopted for several basins, including larger scale river basins, and can improve e-flow management for mitigating the degradation of river ecosystems.

Short Term Real-Time Rolling Forecast of Urban River Water Levels Based on LSTM: A Case Study in Fuzhou City, China.

Water level management is an important part of urban water system management. In flood season, the river should be controlled to ensure the ecological and landscape water level. In non-flood season, the water level should be lowered to ensure smooth drainage. In urban areas, the response of the river water level to rainfall and artificial regulation is relatively rapid and strong. Therefore, building a mathematical model to forecast the short-term trend of urban river water levels can provide a scientific basis for decision makers and is of great significance for the management of urban water systems. With a focus on the high uncertainty of urban river water level prediction, a real-time rolling forecast method for the short-term water levels of urban internal rivers and external rivers was constructed, based on long short-term memory (LSTM). Fuzhou City, China was used as the research area, and the forecast performance of LSTM was analyzed. The results confirm the feasibility of LSTM in real-time rolling forecasting of water levels. The absolute errors at different times in each forecast were compared, and the various characteristics and causes of the errors in the forecast process were analyzed. The forecast performance of LSTM under different rolling intervals and different forecast periods was compared, and the recommended values are provided as a reference for the construction of local operational forecast systems.