Ecological Water Demand Research Articles

Water Quality Restoration with Ecological Water Demand Allocation Regulation

Ecological water replenishment is the main means of ecological restoration in urbanized rivers. The control targets of utilizing water resources, allocating water and restoring the water quality have become the research hotspot. In this study, the Chengnan River Basin in Jiangbei New District of Nanjing was taken as the object, and the ecological water demand threshold in the Chengnan River Basin was evaluated by using the calculation result of the ecological water demand obtained by the improved Tennant method. According to the ecological water replenishment configuration plan, a water quality and quantity coupling model was constructed to simulate and analyze the water quality improvement effects at the control section of the Chengnan River Basin under different guarantee conditions. The results show that the monthly water demand allocation scheme based on the improved Tennant method can be used as the basis for water replenishment of river ecological restoration, and it can effectively improve the water quality of the Chengnan River. The use of 40,000 t / d water replenishment for 11 days can make the Longwangmiao section meet the water quality target control requirements.

Hydropower generation and ecological operation under climate change: a case study of the downstream cascade of Lancang River hydropower plants

Climate change has intensified the conflict between economic and ecological water demands, and brought challenges to the ecological operation of hydropower plants. This study examined the effect of climate change on hydropower generation and ecological operation of hydropower plants, and investigated the response of the interactions between power generation and ecological water demand to climate change. The hydropower operation model and the future streamflow projections modeled by climate projections of several global climate models are used. The downstream cascade of Lancang River hydropower plants was used as a case study. Results show that the overall streamflow and hydrological variability were predicted to increase under climate change, and the ecological flow destruction rate was also predicted to increase. The benefit of hydropower generation and its ecological effects varied more among different operational schemes than among different climate change scenarios, indicating that future conflicts between hydropower generation and ecological water demand are largely inevitable. The increase in hydrological variability caused by climate change can exacerbate the conflict between hydropower generation and ecological water demand, causing larger costs of ecological degradation when retaining the current hydropower benefits.

New grassland riparian zone delineation method for calculating ecological water demand to guide management goals

AbstractRiver flow provides water that maintains the ecological health of both the river itself and the adjoining riparian zones. However, there is a lack of clear definition and identification method of the riparian zone of inland river basins with narrow river channels and anthropogenic intervention reservoirs. In this study, we developed a new method to delineate semiarid grassland riparian zones by taking the Xilin River (Inner Mongolia, China) basin as a case study for providing an opportunity for a more accurate estimation of the ecological water demand of riparian zone. The extent of the riparian zones with different geomorphological and hydrological characteristics was determined by using unmanned aerial vehicle (UAV) images at five river sections along the reach under the combination of natural variations and the regulation by the dams. After mapping each river section, river length and riparian zone area were shown to have a strong relationship (ρs = 0.9; p < .05), which was extended to calculate the downstream riparian zone area by using its river length. Moreover, we applied the distribution flow method to calculate the river ecological water demand and employed the Penman‐Monteith method to calculate riparian zone ecological water demand. The results showed that the river ecological water demand of the downstream of the reservoir was approximately 6.5×106 m3 per year while riparian zone was 2075.1×106 m3. Only 36, 19, and 15% of the ecological water demand can be met in the hydrological wet, average, and dry years, respectively, because of improper reservoir management and the inability of the discharge of the reservoir to meet the ecological water demand of the downstream riparian zone. Our data illustrate the impact and importance of river flow on the downstream degradation of riparian grasslands and can motivate reservoir management in semiarid areas, which will be helpful to guide water regulations to meet environmental and ecological needs.

Ecological Water Rights of the Bosten Lake Wetlands in Xinjiang, China

This paper took the Bosten Lake wetlands as the research object. From the perspective of actual water consumption, the minimum, suitable, and maximum ecological water demand were calculated. It was found that: 1) in a moderate year (P = 50%), the minimum, suitable and maximum ecological water demand was 105,336.5 × 104 m3, 116,835.3 × 104 m3 and 126,051.9 × 104 m3, respectively; 2) in a general dry year (P = 75%), the minimum, suitable and maximum ecological water demand was 102,384.8 × 104 m3, 113,633.5 × 104 m3 and 122,649.6 × 104 m3, respectively; and 3) in a special dry year (P = 95%), the minimum, suitable, and maximum ecological water demand was 98,822.4 × 104 m3, 109,667 × 104 m3 and 118,359.1 × 104 m3, respectively. The values of ecological water demand of the Bosten Lake wetlands gradually decreased from a moderate year to a special dry year. The results showed that the amount of ecological initial water rights of the Bosten Lake wetlands was 190,022 × 104 m3 in a moderate year, 165,990 × 104 m3 in a general dry year and 133,199 × 104 m3 in a special dry year. All the ecological initial water rights with different guarantee rates were larger than the suitable ecological water demand with the same guarantee rates.

Water replenishment for ecological flow with E-WAS framework: a case study of the Longgang River Basin, Shenzhen, China

Abstract. With rapid urbanization, there will be more conflict between human systems and the riverine ecological system, and therefore, ecological operations, practices and research must involve the ecological water replenishment of entire river basins with new modeling tools. In this study, we establish an ecological flow-oriented water resource allocation and simulation framework (E-WAS). Virtual reservoirs and ecological units are added to the water resources network. With new water balance equations for virtual reservoirs and ecological units, the E-WAS can simulate the ecological replenishment process in a river basin and can provide a recommended water replenishment scheme that considers optimization principles. The E-WAS was applied in the Longgang River Basin, Shenzhen, China. 17 ecological units and 45 water supply nodes are considered in the model. A water replenishment scheme that used water from 31 reservoirs and reclaimed water from 7 water sewage plants was selected. This scheme significantly increased the satisfactory degree of ecological water demand and efficiently supported the formulation of a control scheme for the water environment of a basin. The E-WAS framework is similar to model plug-ins but helps to avoid the large workload that is required for model redevelopment and can expand the functions of models quickly.

Comparative study on the dynamic calculation method of river ecological water demand

In order to maximize the seasonal ecological hydrological demand of the river, this paper introduces three improved dynamic calculation methods. Taking the downstream channel of the Jilintai-I Hydropower Station on the Kashi River in Xinjiang as an example, three methods are applied to calculate the ecological water demand of the channel. Meanwhile, it is compared with the improved classification standard of Tennant method, and a method that is more suitable for the calculation of the ecological water demand of the river in this basin is selected, so that the calculation results can meet the seasonal dynamic demand of runoff while ensuring the basic ecological and hydrological demand of the basin, and benefit to the sustainable development of the river habitat. And reduce the losses caused by hydrological disasters, and achieve the coordinated development of economy and ecology.

Long-term and mid-term ecological operation of cascade hydropower plants considering ecological water demands in arid region

As the rapid development of economy, hydropower, as a kind of cleaner energy, is bringing in huge economic benefits, leading to the appearance of a great many of hydropower plants. Decades after the hydropower plants operation, series of quite serious ecological problems were brought in due to the changes in the natural flow. To restore the river ecosystem, this paper is making efforts on seeking series of operation schemes to balance the socio-economic and ecology benefits. Therefore, a simulation (Model-I) and an optimization (Model-II) operation model are established to provide a feasibility and a reasonable scheme for the multi-objective long-term and mid-term hydropower plant operation. To resolve the complex model, large-system coordinated decomposition method and an idea that efficiently narrows down the search space are used. The Irtysh River basin in China is selected as the study area to apply the model and make a trade-off to balance the water supply for socio-economics and ecology. The results show that the average annual power generation of hydropower plant group in Model-I is 2.5% more than that in Model-Ⅱ, both more than that of practical operation. In Model-I the water supply in dry year is far less than the minimum need (50%), but the Model-II provided a reasonable solution that the water supply in dry year is close to the median need (80%). Besides, the water supply for ecology in Model-II is obviously increased compared with Model-I, and the ratio increases from 56% to 86%, at the same time, the ratios to socio-economics are from 92% to 98%. Specially, the ratio of agricultural irrigation increases from 84% to 94%. In a word, the scheme meets the water requirements for socio-economics and ecology under considering the hydropower plants benefits, providing a scientific theoretical basis for water resource management.

Agricultural water optimization coupling with a distributed ecohydrological model in a mountain-plain basin

Agricultural water optimization at the basin scale is critical for sustainable irrigated agriculture and water resources management. Crop Water Production Function (CWPF) and surface water are key components of agricultural water optimization. CWPF relates closely to crop yield/growth-related parameters, and surface water of sub-basins is often different and impacted by water withdrawals. However, CWPF accounting for the crop yield-related parameter and natural runoff of sub-basins were scarcely involved in agricultural water optimization at the basin scale. To fill this gap, CWPFs of different water units are estimated using a distributed ecohydrological model involving the spatial heterogeneity of crop photosynthetic capacity parameter, and the natural runoff of sub-basins is reproduced by this model. Integrating these functions and variables, and taking the agricultural benefit of the whole basin as the main objective, an agricultural water optimization model at the basin scale (AWOMB) is developed and applied to a mountain-plain basin in North China. The results showed that agricultural water optimization in a representative year would lead to 0.4% increase of crop production for the whole basin at the expense of certain urban ecological water and equity of agricultural water. In this scenario, the river ecological water requirements in all sub-basins would be satisfied. Assuming the domestic, industrial and river ecological water demand being fully satisfied in 2020s, water deficits will be 8% and 26% for the whole basin under the normal and dry year scenarios, respectively. Correspondingly, increments of 2% and 7% crop production are predicted in these two scenarios by agricultural water optimization. It is demonstrated that water resources utilization and agricultural production are effectively improved by coupling a distributed ecohydrological model with water resources optimization in the study basin. This research provides a methodology for integrative catchment water resources management.

Long-term Water Regime Studies of a Degraded Floating Fen in Hungary

Historical trends in water management and recent climatic variations put wetlands in the Carpathian basin under strong pressure and led to their degradation. The lack of extended site specific environmental data series inhibits the understanding of long-term eco-hydrological processes. This undermines the success of restoration and/or management efforts. As a precedent we analyzed a recently degraded Hungarian lowland wetland, the Nyárjas fen in order to identify the main cause of its drying. Our method is based on one-dimensional simulations of a variably saturated soil column representing the dominant hydrological conditions of the wetland. To properly define the necessary soil hydraulic parameters, soil sampling, laboratory measurements and inverse modelling were carried out. The hydrological simulations for the 1961-2010 period clearly suggest that (i) the wetland degraded due to a temporal unfavorable combination of regional groundwater depletion and decreased precipitation, (ii) and could not recover afterwards despite the improvement of hydrological conditions. The ecological water demand of the Nyárjas fen can be explicitly expressed in terms of groundwater level. However, water availability is a necessary, but not sufficient criteria of good habitat status. The elaborated methodology provides the basis of bottom-up type environmental water demand estimation on a regional/national scale.

Water Balance Analysis Based on a Quantitative Evapotranspiration Inversion in the Nukus Irrigation Area, Lower Amu River Basin

Human activities are mainly responsible for the Aral Sea crisis, and excessive farmland expansion and unreasonable irrigation regimes are the main manifestations. The conflicting needs of agricultural water consumption and ecological water demand of the Aral Sea are increasingly prominent. However, the quantitative relationship among the water balance elements in the oasis located in the lower reaches of the Amu Darya River Basin and their impact on the retreat of the Aral Sea remain unclear. Therefore, this study focused on the water consumption of the Nukus irrigation area in the delta of the Amu Darya River and analyzed the water balance variations and their impacts on the Aral Sea. The surface energy balance algorithm for land (SEBAL) was employed to retrieve daily and seasonal evapotranspiration (ET) levels from 1992 to 2018, and a water balance equation was established based on the results of a remote sensing evapotranspiration inversion. The results indicated that the actual evapotranspiration (ETa) simulated by the SEBAL model matched the crop evapotranspiration (ETc) calculated by the Penman–Monteith method well, and the correlation coefficients between the two ETa sources were greater than 0.8. The total ETa levels in the growing seasons decreased from 1992 to 2005 and increased from 2005 to 2015, which is consistent with the changes in the cultivated land area and inflows from the Amu Darya River. In 2000, 2005 and 2010, the groundwater recharge volumes into the Aral Sea during the growing season were 6.74×109 m3, 1.56×109 m3 and 8.40×109 m3; respectively; in the dry year of 2012, regional ET exceeded the river inflow, and 2.36×109 m3 of groundwater was extracted to supplement the shortage of irrigation water. There is a significant two-year lag correlation between the groundwater level and the area of the southern Aral Sea. This study can provide useful information for water resources management in the Aral Sea region.

Incorporating Historical Spring Discharge Protection Into Sustainable Groundwater Management: A Case Study From Pearl Harbor Aquifer, Hawai‘i

Groundwater management policy around the world increasingly seeks to protect groundwater-dependent ecosystems and associated human uses and values. This includes uses of ecosystems and agricultural systems linked to natural spring discharge. Yet, there are few examples of practical tools to balance human groundwater use with ecological water demand related to spring discharge. Using a simulation optimization framework, we directly incorporate a spring discharge constraint into the analysis of sustainable yield for operationalizing groundwater policy in the state of Hawai‘i. Our application on the island of O‘ahu is a spring discharge-dependent watercress farm with historical, cultural, and ecological significance. This research provides decision-makers in Hawai‘i with information regarding the trade-off between groundwater pumping and spring discharge, which is connected to multiple benefits, including historical and cultural values in line with codified state beneficial use protections. Because this trade-off provides an important step in operationalizing sustainable yield policy in Hawaii, we conclude by discussing further conceptual and technical developments necessary to move groundwater policy in Hawai‘i closer to full incorporation of the public trust principles of the state water code.

Characterization of soil water by the means of hydrogen and oxygen isotope ratio at dry-wet season under different soil layers in the dry-hot valley of Jinsha River

AbstractThe soil water was stratified sampling and analyzed with 0–100 cm by three plantation (Leucaena Benth Forest land, Dodonaea angustifolia Shrub land and Heteropogon contortus grassland) at the dry-hot Valley in Jinsha River, at June, September, December of 2016, which were to know about the variation and mechanism of soil water movement. The results showed that (1) soil water in different soil layers is significantly different, and the overall performance is shrub land (11.65%) > grassland (8.29%) > forest land (6.76%); (2) the δD isotope ratio of the soil water from all samples ranged from −146.359% to −54.628% and the δ18O isotope ratio ranged from −20.272% to −2.148%, and there is a good linear relationship between isotope ratios of soil water of three different soils; (3) there is a change with season: the intercept of the isotopes ratio at different months decreased in turn, June < September < December. While the shrub lands and grassland had the same pattern but slightly different, the isotope ratio of soil moisture in December was lower, and the intercepts of shrub land in September were significantly larger than in December; (4) there is a change in space: the total difference isotopes ratio of soil water is larger at the shallow soil layer and changed sharply at all positions of the forestland, while those in the shrub land and grassland changed became relatively weakly. This study provides the theoretical basis for the key problems of plant water using mechanism, ecological water demand, vegetation recovery and so on.

Velocity and turbulence evolution in a flexible vegetation canopy in open channel flows

Dams intercept the river flow and reduce the water input of downstream lakes, which leads to the decreased water level and deteriorated water environment. Environmental water releases are becoming regular ways to maintain ecological water demand of lakes. This study was carried out to describe how natural submerged flexible vegetation altered velocity and generated turbulence under different water releases discharge scenarios. Natural Ceratophyllum demersum L. was collected from a large shallow lake, Baiyangdian Lake, China. Two vegetation densities were set in this flume experiments. The flow velocity was measured using particle image velocimetry (PIV) techniques and used to study the mean flow features (velocity and Reynolds stress) and distributions of vegetative drag and development length. The observed velocity profiles presented vertical stratification. The greatest gradient of velocity and shear stress appeared around the top of the canopy. The canopy drag of submerged flexible vegetation presented a parabolic vertical distribution, and smaller drag was generated by larger flows under the same density. The initial adjustment length of water flow was linearly correlated with the deflected height of flexible vegetation and was little affected by the vegetation density in the two studied densities. The most intense turbulence in the vegetation canopy appeared at its top, where the largest shear stress was also observed. Strong canopy-scale vortices on the top of the canopy were produced and penetrated closer to the bed in the cases of denser vegetation under small discharges (Cases 3.1–3.5); penetration was also restricted by canopy drag and was unable to reach the bed.

Effects of land use changes on the ecological operation of the Panjiakou-Daheiting Reservoir system, China

The problem of insufficient water for ecological purposes in the Luanhe River basin requires urgent resolution. The regional hydrological cycle is affected by the Panjiakou-Daheiting Reservoir system and by changes in land use in the upper watershed. Therefore, this system was selected as a study area to simulate ecological reservoir operation and analyze the effects of changes in land use on ecological operation. A physical habitat simulation model (PHABSIM) was built to determine the minimum and suitable ecological water demand. Then, an ecological reservoir operation model using an improved differential evolution (DE) algorithm was established. Simulated inflow data under the land use conditions in 1970 and 2015 were input into the model, and the effects of changes in land use on ecological operation and on the weighted usable area (WUA) for cyprinoids were calculated. The results show that ecological reservoir operation significantly improves the ecological water supply and increases cyprinoid habitat. The changes in land use led to a decrease in annual runoff, which further reduced the urban water supply by 0.67%–2.25% and the ecological water supply by 0.45%–2.04% at different flow frequencies. The land use changes also caused the WUA to decrease by 1746–2999 m2/km at different flow frequencies, with a decrease rate of 1.04%–6.28%. This study could provide valuable information for water resource managers operating reservoirs in river ecosystems and planning to cope with water shortages caused by land use change in water-deficient areas.

Study on the Ecological Operation and Watershed Management of Urban Rivers in Northern China

Small- and medium-sized rivers are facing a serious degradation of ecological function in water resource-scarce regions of Northern China. Reservoir ecological operation can restore the damaged river ecological environment. Research on reservoir ecological operation and watershed management of urban rivers is limited in cold regions of middle and high latitudes. In this paper, the urban section of the Yitong River was selected as the research object in Changchun, Northern China. The total ecological water demand and reservoir operation water (79.35 × 106 m3 and 15.52 × 106 m3, respectively) were calculated by the ecological water demand method, and a reservoir operation scheme was established to restore the ecological function of the urban section of the river. To examine the scientific basis and rationality of the operation scheme, the water quality of the river and physical habitat after carrying out the scheme were simulated by the MIKE 11 one-dimensional hydrodynamic-water quality model and the Physical Habitat Simulation Model (PHABSIM). The results indicate that the implementation of the operation scheme can improve the ecological environment of the urban section of the Yitong River. A reform scheme was proposed for the management of the Yitong River Basin based on the problems in the process of carrying out the operation schemes, including clarifying department responsibility, improving laws and regulations, strengthening service management, and enhancing public participation.

Water Resources Allocation of the Changjiang To Huai River Water Diversion

The Changjiangriver to Huai river water diversion project plans to divert water from the lower reaches of the Changjiangriver to replenish water in the middle reaches of the Huaihe river, mainly for the purpose of ensuring urban and rural water supply, developing Jianghuai shipping and improving river and lake ecology. In this paper, we predict the four aspects water demand including domestic, industrial, agricultural and ecological water demand in the river channel in 2030. According to the rules of lakes and water supply projects, we can obtain the water supply under different typical years. The balance of water supply and demand is analyzed for different circumstances. It is concluded that the average annual total water demand in the planned area in 2030 is 18.335 billion m3, the total water supply is 15.356 billion m3, and the water shortage is 2.979 billion m3.

Evaluation the ecological water demand of Dongting Lake based on ecological hydrology during the storage period

This paper is aimed at evaluating the ecological water demand of Dongting Lake in the middle reach of Yangtze River. Since Dongting Lake has evolved into a lake area connected by three waterways: Eastern Dongting Lake, Southern Dongting Lake and Western Dongting Lake, the ecological water level and ecological water demand of different lake areas must be obtained separately. In the Eastern Dongting Lake, we choose Lujiao station as the water level representative station, and choose Yingtian and Yangliutan station as the water level representative station in Southern Dongting Lake, and choose Nanzui and Xiaohezui station as the water level representative station in Western Dongting Lake. The natural water level data is used to obtain the ecological water level in different lake areas of Dongting Lake based on the ecological hydrology method, and then the ecological water demand is obtained through the lake water level-volume relationship curve. The ten-day average minimum ecological water demand of Dongting Lake from September to October is 6.042, 5.294, 4.095, 3.548, 3.139, 2.864 billion m3. The determination of the minimum ecological water demand of Dongting Lake provides a scientific basis for defining the safety status of the lake ecosystem.

Classification of instream ecological water demand and crucial values in a semi-arid river basin

Analyzing the instream environmental flow demand by coupling the hydrological cycle and the hydrodynamic process with aquatic ecological processes at watershed scale remains one of the most important yet most difficult issues. One or two of the above processes have been the focus in the evaluation of intra-annual ecological water demand in recent studies. In this study, a hydrology–hydrodynamic–habitat model was developed and applied to the Huangshui River basin. A new classification method for instream ecological water demand (IEWD), which considered sensitive species was proposed. The suitable level of IEWD and crucial values with different flow frequencies were analysed, including runoff, water level, water surface width and weighted usable areas (WUA). The results of the study indicated that monthly IEWD had an increasing trend during the flood season and a decreasing trend during the non-flood season in three sections at different suitable levels. With the increase of suitable levels, the range of IEWD in three sections also increased. The IEWD and crucial values were the lowest in March with the smallest range and were the highest from July to October because the amount of precipitation during that period accounted for nearly 84.3% of that of the entire year. Furthermore, the lower the flow frequency in three sections, the higher the suitable levels of IEWD, as well as water level and water surface width every month. When the flow frequency of 90% decreased to 75%, the value of IEWD increased by at least 55% during the wet season and doubled during the dry season. The WUA with the lowest or highest flow frequencies were relatively poor, especially reproduction period. The IEWD and crucial values at different suitable levels agreed with the actual situations. Thus, this study provided a new method for implementing river ecosystem restoration and aquatic ecosystem management.

Evaluating and mapping water supply and demand for sustainable urban ecosystem management in Shenzhen, China

Abstract Rapid urbanization has resulted in a shortage of regional water resources, causing an imbalance for water resources. With the implementation of ecological policies, regional water management has been developed. However, the relationship between supply and demand of water resources and spatial distribution remains unclear under current policies, which lead to a lag in decision making and irrationality in decision makers. Shenzhen, a highly urbanized city, was used as an example to discuss the balance of urban water resources and its driving force. Furthermore, practical guidance for ecosystem management is discussed. Results revealed that the supply and demand of water in Shenzhen were imbalanced in spatial distribution. The demand for water resources was greater than the supply at an urban scale, and the unsatisfied demand of basins accounted for 81.1% of the total area. The underlying factors that greatly affected water supply were construction land, forests, water bodies, and farmland. The population density, per capita green area, and industrial areas increased the demand for water resources. Ecological water and domestic water demand will become the main water demand. The government should actively explore and practice the mechanism of water resources development and protection, prioritize water conservation, improve the efficiency of water resource utilization and construct water-saving lifestyles. Additionally, discussion on the landscape greening configuration to reduce the ecological water demand is recommended.

Integrated ecosystem services-based calculation of ecological water demand for a macrophyte-dominated shallow lake

Macrophyte-dominated shallow lakes are one of the commonest freshwater wetlands in plain area, and composed of lake, marsh, and terrestrial land. They are, however, facing great ecological risks of serious pollution and wetland degradation caused by the shortage of ecological water demand. Baiyangdian is the largest shallow lake in northern China. It is of great importance to ecosystem services in Xiongan New Area, China, providing food production, climate regulation and other functions. Water storage in Baiyangdian comprises components of lake, marsh and terrestrial land, each of which supplies a different ecosystem service value (ESV). As a result, the total ESV of a macrophyte-dominated shallow lake changes according to water storage fluctuation. In this study, we estimated the total and individual land ESVs (lake, marsh, and terrestrial land) of the Baiyangdian. We also quantified the relationship between ESV and water storage in the macrophyte-dominated shallow lake, taking water level as the indicator. The optimum water level varied, corresponding to the highest ESV of each type of land, and an optimum water level of 8.2 m was identified as achieving the highest total ESV of the Baiyangdian (6.697 billion yuan). We also divided ecosystem services into four functional categories: provisioning, regulating, supporting, and cultural and found these components also changed with water storage changes in the macrophyte-dominated shallow lake. Fluctuation in the total ESV was attributed mainly to the marshland because of its huge supply capacity for support and cultural services. An optimum water level range of 7.9–8.5 m existed where ESV was most balance among different functional categories. After considering the functional and land cover components of total ESV of the Baiyangdian, we recommend an optimum water level of 8.2 m, and emphasize the importance of including ESV in calculations of ecological water demand.