Ecological Water Requirement Research Articles

Impact of the Grain for Green Project on water resources and ecological water stress in the Yanhe River Basin.

The Grain for Green project (GGP), initialized by the Chinese government in 1999, has achieved substantial achievements accompanied by a decrease in surface runoff on the Loess Plateau, but the impacts of large-scale afforestation on regional water resources are uncertain. Hence, the objective of this study was to explore the impact of land use change on generalized water resources and ecological water stress using the blue and green water concepts, taking the Yanhe River Basin as the case study. The Soil and Water Assessment Tool (SWAT) was applied to quantify the green water and blue water, which are defined as generalized water resources. The ecological water requirement of vegetation (forest and grass), agricultural water footprint and virtual water flow are considered regional water requirements. The land use types of 1980 (Scenario I) and 2017 (Scenario II) were entered into the SWAT model while keeping the other parameters constant to isolate the influence of land use changes. The results show that the average annual differences in blue, green and generalized water resources were -72.08 million m3, 24.34 million m3, and -47.74 million m3, respectively, when the simulation results of Scenario II were subtracted from those of Scenario I, which shows that land use change caused by the GGP led to a decrease in blue and generalized water resources and an increase in green water resources. Surface runoff in Scenario I was more than that in Scenario II in all of the years of the study period from 1980–2017, and green water storage in Scenario I was more than that in Scenario II in all of the years of the study period except in 1998; although lateral flow in Scenario I was less than that in Scenario II except in 2000 and 2015, as was groundwater runoff in 1992, 2000 and 2015, and green water flow in 1998. Blue water flow, green water storage and green water flow in Scenario II were less than those in Scenario I in the whole basin, 12.89 percent of the basin and 99.21 percent of the basin, respectively. The total water footprint increased from 1995 to 2010 because the forest water footprint increased significantly in this period, although the agricultural water footprint and grass water footprint decreased. The ecological water stress index values had no obvious temporal change trends in either land use scenario, but the ecological water stress index in Scenario II was greater than that in Scenario I, which illustrates that the GGP led to an increase in ecological water stress from the perspective of generalized water resources.

Definition and calculation of hierarchical ecological water requirement in areas with substantial human activity—A case study of the Beijing–Tianjin-Hebei region

In areas with high levels of human activity, there is often an imbalance between the supply and demand of water resources. This often means that ecological water requirements (EWRs) cannot be met in the long term, which leads to a deterioration in the ecological environment. To protect the ecological environment in areas with considerable human activity, research into hierarchical EWRs is essential. This paper first defined the hierarchical EWR concept (the minimum, suitable and ideal EWR) in areas with substantial human activity, and then developed a method to calculate this requirement over a large-scale area, taking the Beijing–Tianjin–Hebei region in China as a case study. Results showed that the minimum EWR in the Beijing–Tianjin–Hebei region was 42.81 × 108 m3, the suitable EWR was 54.37 × 108 m3, and the ideal EWR was 70.01 × 108 m3. The EWR of 13 cities in the region was calculated. The water requirement in the central area of Beijing–Tianjin–Hebei was significantly higher than that of the southern or northern areas. The EWR rate was used to characterize the EWR as a proportion of the surface water resources. The results showed that the minimum, suitable and ideal EWRs for Beijing–Tianjin–Hebei were 39%, 49%, and 63%, respectively. It was calculated that the annual average ecological water supply guarantee rate of Beijing–Tianjin–Hebei from 2015 to 2019 was 46%, which generally met the minimum EWR. This paper provides technical methods and a reference for calculating the EWR over large-scale areas with considerable human activity.

The Ecological Water Demand of Different Vegetation Types in the Bashang Area, Northwest Hebei Province

In order to construct stable vegetation for reducing wind and sand disasters and soil erosion in the Bashang Area of Northwest Hebei Province in China, it is very important to understand the ecological water demand of different vegetation types in this area. Based on observed data and the Irmak-Allen formula, we investigated the ecological water demand and ecological water shortage of arbor, shrub and grassland in Bashang Area of northwestern Hebei province. The results showed that the actual evapotranspiration values of the three vegetation types in the growing seasons in the study area from high to low were arbor forest (401.81 mm), shrub (358.78 mm) and grassland (346.02 mm). The minimum ecological water requirements of arbor forest, shrub and grassland in the growing season were 243.96 mm, 218.35 mm and 211.36 mm, respectively, and the optimal ecological water requirements were 472.99 mm, 423.34 mm and 409.77 mm, respectively. In addition, the optimal ecological water shortage values were 198.56 mm for arbor forest, 148.91 mm for shrub and 135.34 mm for grassland. The ecological water shortage of vegetation has obvious seasonality, with the largest water shortage in May and June, and a lower and steady water surplus in July to October. Therefore, an artificial water supplementation in May and June would alleviate the drought stress of the vegetation. The rainfall in Bashang Area of Northwest Hebei Province can meet the requirements of minimum ecological water demand for arbor forest, but the gap between the rainfall and the optimal ecological water requirement is too large to support good growth of an arbor forest, which could explain why the degradation of poplar protective forests has occurred in Bashang Area.

Establishment of watershed ecological water requirements framework: A case study of the Lower Yellow River, China

It is of great practical significance to ensure ecological water requirements (EWRs) for the maintenance of river health and the sustainable development of human socioeconomics. How to scientifically determine the comprehensive EWRs and estimate the uncertainty of hydro-ecological tools performed in the process of conducting remains one of the most important yet most complicated issues. In this study, the ecological water requirements framework (EWRsF) of the Lower Yellow River (LYR), which considers instream ecological base flow, survival and reproduction of indicator fish species, equilibrium of erosion and siltation and ecological function of the estuary, was constructed by integrating hydrological, hydraulic and ecological habitat methods. The framework contains three crucial components - determination of instream EWRs and estuarine EWRs, uncertainty analysis of hydro-ecological tools. For instream ecological base flow, we proposed an improved Tennant method, which took into account both seasonality and sediment transport characteristics of the LYR, and could better reflect the actual hydrological regime. For the hydrological ecological response relationship of indicator fish species, we estimated the uncertainty of the model output of River2D to improve its credibility of the simulation results. The results demonstrated that: 1) Two-grade intra-annual monthly EWRs process of suitable and minimum for four instream sections and estuary area were obtained. The flood season (June–October) is the period with the largest proportion of intra-annual instream EWRs, whereas in estuary area, is the spawning period (April–July) of dominant species. 2) The uncertainty of HSI curves directly leads to the uncertainty of model output. Although the shape and position of the WUA curve can be uncertain, it does not affect the judgment of EWRs threshold. 3) The research results can provide scientific basis for water resource management decision-making in the LYR. Additionally, the ideas also have reference significance for similar basins.

Inclusion of Ecological Water Requirements in Optimization of Water Resource Allocation Under Changing Climatic Conditions

Inclusion of Ecological Water Requirements in Optimization of Water Resource Allocation Under Changing Climatic Conditions

Suggestions for Revegetation over the Next 30 Years Based on Precipitation in the Three North Region of China

Afforestation in the Three North Region (TNR) of China has received wide concern due to the low survival rate and threats to water security associated with the lack of available precipitation for vegetation. It is crucial to provide a spatial layout for revegetation according to the available precipitation to achieve the vegetation cover target. This study investigated the spatial pattern of precipitation, determined the suitable vegetation distribution based on the ecological water requirements and precipitation, and proposed an optimized revegetation scheme by comparing the actual and suitable vegetation patterns. The results indicated that the actual vegetation that matched the pixel-level precipitation accounted for 67.24% of the total vegetation area in the TNR. However, 18.50% of the actual forest, 21.82% of the actual shrublands, and 19.95% of the actual grasslands were overloaded with respect to precipitation. The total suitable vegetation area was reduced slightly compared to the actual vegetation area. There is still some potential for the revegetation of forest and shrublands, mainly those in the eastern and south-eastern parts of the TNR. The optimized revegetation area in the TNR was 3.04 × 106 km2, including a maintenance management type of 2.19 × 106 km2, an upgrade type of 0.49 × 106 km2, and a degradation type of 0.37 × 106 km2. Maintenance management (natural restoration) and transformation to vegetation types with lower ecological water requirements were recognized as important revegetation practices in the TNR. This study provides guidelines to adjust the Three North Shelterbelt Project policies based on precipitation data to reduce the negative impact of revegetation on the hydrological cycle.

Remote Sensing and Geospatial Models to Simulate Land Use and Land Cover and Estimate Water Supply and Demand for Water Balancing in Phuket Island, Thailand

Currently, Phuket Island is facing water scarcity because water demand for consumption was approximately 51 million m3/year, whereas water supply was only about 46 million m3/year. Thus, the study of water supply, demand and balancing are important for effective water resources management. This study aims to simulate the LULC data using the CLUE-S model, estimate water supply using the SWAT model, and calculate water demand using a water footprint basis for water balancing on the Island. In addition, tourist water demand was separately estimated under normal and new normal conditions (COVID-19 pandemic) to fit with the actual situation at national and international levels. Water balance results with the consideration of ecological water requirements suggest that a water deficit occurs every year under the dry year scenario in normal and new normal conditions. In addition, the monthly water balance indicates that a water deficit occurs in the summer season every year, both without and with the consideration of ecological water requirements. Consequently, it can be concluded that remote sensing data with advanced geospatial models can provide essential information about water supply, demand, and balance for water resources management, particularly water scarcity, in Phuket Island in the future. Additionally, this study’s conceptual framework and research workflows can assist government agencies in examining water deficits in other areas.

Ecological Water Requirement in Upper and Middle Reaches of the Yellow River Based on Flow Components and Hydraulic Index.

Deterioration of the ecological environment in the upper and middle reaches of the Yellow River in China substantially impacts the growth and development of aquatic organisms in the drainage basin. This paper builds a conceptual model by applying flow components and fish ecological requirements relation with a relevant object of main fish in the upper and middle reaches of the Yellow River. The paper utilized the flow restoration method by employing the River2D model (two-dimensional model of river hydrodynamics and fish habitat), and a one-dimensional hydrodynamics HEC-RAS (hydrologic engineering center’s-river analysis system). The calculation result showed that the runoff condition required for Silurus lanzhouensis survival is that the monthly lowest flow in a year is 150 m3·s−1, and the lowest flow for suitable flow from April to October is 150 m3·s−1, and 300 m3·s−1 from November to March. The research result is closer to the actual condition and has more outstanding operability. Meanwhile, the results proposed the coupling method of ecological water requirement for the mainstream of the Yellow River. Moreover, the results portrayed the ecological flow process according to the upper envelope of minimum and maximum ecological water requirements of each fracture surface. It is regarded that the ecological flow process is deemed as the initial value of the reservoir regulation model.

An Environmental Flow Framework for Riverine Macroinvertebrates During Dry and Wet Seasons Through Non-linear Ecological Modeling

A suitable environmental flow is critical for the functional maintenance of riverine ecosystems. Hydropower plants alter the flow regime by decreasing or even drying up the streamflow downstream of the dams, thereby affecting ecosystem sustainability. In this study, we aimed to develop a robust environmental flow framework that can provide scientific evidence for sustainable water resource management. Using ecological niche modeling based on non-linear responses of species to habitat factors, we assessed the environmental flow in the Xiangxi River Basin of Central China during dry and wet seasons from a multi-year perspective. The most abundant macroinvertebrate taxon (i.e.,Baetis) was selected for model testing. The results showed seasonal differences in the minimum ecological water requirements and optimal environmental flow. These two hydrological metrics were higher during the wet season than during the dry season. During the dry season, the minimum ecological water requirement ofBaetiswas 1.3 m3·s−1, and the optimal environmental flow was 1.6 m3·s−1. During the wet season, the minimum ecological water requirement ofBaetiswas 2.5 m3·s−1, and the optimal environmental flow was 2.6 m3·s−1. This study provides a theoretical basis for the robust management of water resources in river basins.

Assessing irrigated water utilization to optimize irrigation schedule in the oasis-desert ecotone of Hexi Corridor of China

Water is the key factor limiting crop production in arid inland river basins of northwestern China, where water scarcity challenges food security and the sustainability of eco-environment. Changing the chronical management strategies is urgent to realize more crop per drop and to satisfy ecological water requirement in the Hexi Corridor, where agriculture relied heavily on irrigation using groundwater. Long-term observations of soil water balance components and crop production are lack but essential to optimize irrigation schedules with moderate groundwater recharge. AquaCrop model was calibrated and validated using field data on spring wheat and spring maize rotation in the midstream of the Heihe River from 2005 to 2014, and used to assess current irrigation practices and to generate optimal deficit irrigation schedules. Simulations of soil water balance, canopy progression, biomass accumulation and yield production over time well mimicked the water utilization and crop development. Plastic mulching prevented 53.5% and 62.6% of potential soil evaporation for spring wheat and spring maize, respectively. Temporary water logging soon after irrigation reduced transpiration by restricting canopy development and stomatal conductance. No more than 30% of water supply was used by crops, but drainage below root zone occupied more than 68% of water supply by present. Mean biomass water use efficiency (WUE) was 0.034 kg m−3 and 0.047 kg m−3, and mean yield WUE was 1.16 kg m−3 and 2.41 kg m−3 for spring wheat and spring maize, respectively. Cultivar “2014” for spring wheat and cultivar “8703” for spring maize were suitable for yield production in this area. Beyond 50% of applied water would be productively used with reduction of drainage in water supply by more than 25% under the modified irrigation schedules. Total amount of applied water reduced by about 50%, but the biomass and yield values would remain unchanged. These irrigation schedules will greatly improve WUE of irrigated agriculture, supporting the rational allocation of water resources of the inland river basins at a watershed scale.

Calculation of instream ecological water requirements under runoff variation conditions: Taking Xitiaoxi River in Taihu Lake Basin as an example

Calculation of instream ecological water requirements under runoff variation conditions: Taking Xitiaoxi River in Taihu Lake Basin as an example

Application of edge computing and GIS in ecological water requirement prediction and optimal allocation of water resources in irrigation area.

The purposes are to use water resources efficiently and ensure the sustainable development of social water resources. The edge computing technology and GIS (Geographic Information Science) image data are combined from the perspective of sustainable development. A prediction model for the water resources in the irrigation area is constructed. With the goal of maximizing comprehensive benefits, the optimal allocation of water quality and quantity of water resources is determined. Finally, the actual effect of the model is verified through specific instance data in a province. Results demonstrate that the proposed irrigation area ecological prediction model based on edge computing and GIS images can provide better performance than other state of the art models on water resources prediction. Specifically, the accuracy can remain above 90%. The proposed model for ecological water demand prediction in the irrigation area and optimal allocation of water resources is based on the principle of quality water supply. The optimal allocation of water resources reveals the sustainable development ideas and the requirements of the optimal allocation model, which is very reasonable. The improvement of the system is effective and feasible, and the optimal allocation results are reasonable. This allocation model aims at the water quality and quantity conditions, water conservancy project conditions, and specific water demand requirements in the study area. The calculation results have great practicability and a strong guiding significance for the sustainable utilization and management of the irrigation area.

Simulation of Water and Salt Dynamics under Different Water-Saving Degrees Using the SAHYSMOD Model

Water shortage and soil salinization are the main issues threatening the sustainable development of agriculture and ecology in the Hetao Irrigation District (HID). The application of water-saving practices is required for sustainable agricultural development. However, further study is required to assess the effects of these practices on water and salt dynamics in the long term. In this study, the impacts of different water-saving practices on water and salt dynamics were investigated in the HID, Northwest China. The SAHYSMOD (integrated spatial agro-hydro-salinity model) was used to analyze the water and salt dynamics for different water-saving irrigation scenarios. The results indicate that the SAHYSMOD model shows a good performance after successful calibration (2007–2012) and validation (2013–2016). The soil salinity of cultivated land in the middle and upper reaches of the irrigation district decreased slightly, while that in the lower reaches increased significantly over the next 10 years under current irrigation and drainage conditions. It is predicted that if the amount of water diverted is reduced by up to 15%, the maximum water-saving volume could reach 650 million m3 yr–1. For the fixed reduction rate of total water diversion, the prioritized measure should be given to reduce the amount of field irrigation quota, and then to improve the water efficiency of the canal system. Although a certain amount of water can be saved through various measures, the effect of water saving in the irrigation district should be analyzed comprehensively, and the optimal water management scheme should be determined by considering the ecological water requirement in the HID.

The Decision of an Eco-Friendly Reservoir Operation Scheme Based on a Variable Set

The river ecosystem has the characteristics of the coexistence of clarity and ambiguity. The starting point of eco-friendly reservoir operation is to fully consider the ecological water requirements of the lower reaches of the reservoir, so it also has the characteristics of clarity and vagueness. The fuzzy theory is an excellent tool to realize the quantification of fuzzy concepts. In this paper, the variable set theory (VS) is introduced into the decision-making field of eco-friendly reservoir scheduling scheme optimization. Taking Ertan Hydropower Station as an example, the scheduling scheme optimization is carried out. To verify the effectiveness of the evaluation method, this paper compares and analyzes the evaluation results of the fuzzy set evaluation method and the composite fuzzy matter-element method. The results show that the variable fuzzy set method has the advantages of rigorous theory, a concise model, and simple calculation, and the decision result is reasonable and reliable. This research can provide new ideas for the decision-making research of engineering.

A novel index for ecological drought monitoring based on ecological water deficit

Although the concept of ecological drought was first defined by the Science for Nature and People Partnership (SNAPP) in 2016, there remains no widely accepted ecological drought monitoring index. Therefore, this study constructed a new ecological drought index, the standardized ecological water deficit index (SEWDI). The SEWDI is based on the difference between ecological water requirement and consumption, referred to as the standardized precipitation index (SPI) method, which was used to monitor ecological drought in Northwestern China (NWRC). The performance of the SEWDI was compared with that of other widely–used drought indices, including standardized root soil moisture index (SSI), self–calibrated Palmer drought index (scPDSI), standardized precipitation–evaporation drought index (SPEI), and SPI, using the Pearson correlations between these indices and standardized normalized difference vegetation index (SNDVI) under different time scales, wetness and water use efficiencies (WUE) of vegetation. The SEWDI at a 12–month scale was decomposed in NWRC during 1982–2015 using the rotational empirical orthogonal function (REOF) in order to demarcate five ecological drought regions, including southeastern sub–region (SE), southwestern sub–region (SW), northwestern sub–region (NW), northeastern sub–region (NE), and central sub–region (CT). The characteristics of ecological drought in NWRC, such as intensity, duration, and frequency, were extracted using the run theory. The return periods of five types of drought were calculated using wavelet analysis. Results showed that the performance of SEWDI in monitoring ecological drought was the best among the drought indices under different time scales, and the 12–month–scale was largely unaffected by wetness and WUE. Results of monitoring indicated that serious ecological droughts in the NWRC mainly occurred in 1982–1986, 1990–1996, and 2005–2010, primarily in SE, SW, and CT, SW and NE, and NW, NE, and CT, respectively. Furthermore, SEWDI in the arid SW, NW and CT showed a longer return period compared to that in the humid NE and SE, and the evolution of ecological drought in arid regions was mainly influenced by meteorological drought and the scarcity of root soil moisture. This study provides ant approach for quantifying ecological drought severity across natural vegetation areas which can be employed by decision makers

Quantitative calculation and optimized applications of ecological flow based on nature-based solutions

The current difficulties in determining the ecological flow of rivers in northern China are the poor pertinence of methods and insufficient consideration of ecological factors. On the basis of systematic analysis of river hydrological situations and ecological protection objectives, the existing water ecological problems in river reaches were identified, a nested calculation framework for ecological flow of rivers was given based on Nature-based Solutions (NbS), considering the ecological integrity, biological diversity, morphological diversity and ecological service functions. With help of physical habitat simulation and the Penman-Monteith formula, indicator species were selected to research the natural process of restoring river function and realizing river runoff. To meet the water requirements of riparian vegetation during the growth period of the indicated species, the water demand law of typical vegetation changing with the growth time was studied, the upper and lower water levels were set, and the ecological water requirements of vegetation at each growth stage were determined. The results showed that the ecological basic flows required for the spawning period (April-June), the juvenile period (July-November) and the growth period (December-March) of Pseudorasbora parva in the Long River (typical section) were 3.14 m3/s, 4.32 m3/s and 2.16 m3/s, respectively. At the end of the spawning period, a 7-day (90% guarantee rate) pulse flow with a peak flow of 11.31 m3/s, a small flood process with a peak flow of 24.95 m3/s and a small flood process in the flood season lasting for 3 days provided effective external stimulation for the spawning of Pseudorasbora parva. The minimum annual ecological water requirement of reed was 15,100 m3. The current ecological flow of the Long River can meet the water requirements of most aquatic organisms and plants in the river ecosystem. The ecological flow calculation method based on NbS is widely applicable, and the results are representative. The method can be used to calculate the ecological flow of small and medium-sized northern rivers with a small flow and low flow rate.

Study on Ecological Water Requirement of Vegetation in Wuhai Based on GIS

Wuhai City is located in Inner Mongolia, belongs to the arid and semi-arid area of Northwest China, where precipitation is scarce, vegetation coverage is low and evaporation is large. With the exploitation of coal resources, the cultivated land area is gradually reduced and the surface is seriously damaged. After mining, a large number of mines and coal gangue piles are left behind, causing serious ecological problems. In order to ensure the normal growth of vegetation in Wuhai City, it is of great significance to study the ecological water demand of vegetation in Wuhai City for the realization of reasonable allocation of water resources, ecological restoration of mines and sustainable development of the city. Based on remote sensing satellite image data, combined with land use type map and ground meteorological data, this paper analyzes the spatial and temporal variation characteristics of normalized difference vegetation index (NDVI) in Wuhai City, calculates the evapotranspiration of vegetation in reference year, and obtains the ecological water demand of vegetation in Wuhai City by using area quota method according to different water demand spatial areas. The results showed that: in the total ecological water demand of vegetation in Wuhai City, the water demand of medium coverage grassland was the largest, reaching 407.59 mm, while that of forest land was the smallest, reaching 309.01 mm. The other water requirements from large to small are: low coverage grassland, high coverage grassland, sparse forest land, shrub land. Grassland accounts for 98% of ecological water demand, while woodland only accounts for 2%. The total ecological water demand is 326 million m3.

BASIC CONSTRUCTION PRINCIPLES FOR MULTI-FUNCTIONAL HYDRO AGROLANDSCAPE SYSTEMS

Based on the principles of natural analogies, the necessary diversity, the ability of soil formation and the integration of knowledge, multifunctional hydroagrolandscape systems have been developed, including multifunctional systems (crop rotation fields and irrigation technique), which ensure the fulfillment of the ecological and economic functions of the soils of hydroagrolandscape systems. Multifunctional hydro-agrolandscape systems for the purposeful regulation of the soil-forming process on irrigated crop rotation fields by designing crop rotation and an irrigation system on irrigated lands (hydro-agricultural landscape system) with the linkage of agricultural crops to irrigation equipment and technology, which move along with agricultural crops according to the rotational scheme, adopted in the crop rotation, ensure the maximum possible use of solar energy for the soil-forming process in specific natural and climatic conditions. The environment-forming functions of a multifunctional hydro-agrolandscape system are provided on the basis of the use of integral criteria to ensure the agroecological sustainability of irrigated crop rotations (hydroagrolandscapes), taking into account geoecological restrictions, that is, the weighted average irrigation rate (water demand deficit) of agricultural crops in the crop rotation should not exceed the deficit of the ecological water requirement of agricultural land systems. Thus, the design of highly productive hydrolandscape systems requires ensuring compliance with not only the principles of the necessary diversity and natural analogies, based on the creation of se-rotations with mobile irrigation techniques to control and regulate soil-forming processes, that is, the soil as an object of influence (reclamation) performing an ecological function , and agricultural crops as a subject perform an economic function, requires the need, on the basis of the principle of knowledge integration, to form ways of regulating the natural process that provide targeted regulation and control of soil-forming processes as environment-forming systems.

Scenario analysis for the sustainable development of agricultural water in the Wuyuer River basin based on the WEP model with a reservoir and diversion engineering module

Agricultural water use is increasing quickly with the rapid socioeconomic development observed in the Wuyuer River basin. Water withdrawal for agriculture over the past decade have seriously depleted the ecological water requirements in the basin and damaged the channel and downstream wetland ecosystems. Achieving sustainable development in the basin will require a balance between agricultural water exploitation and ecological water demands. In this paper, a reservoir and diversion engineering module was integrated with a dualistic distributed hydrological model (WEP model) to investigate the effects of agricultural water use on river discharge. Agricultural water shortages and yearly minimum river discharges between 2020 and 2050 under six agricultural water exploitation scenarios and one natural scenario were estimated based on the proposed model. The results showed that the dualistic hydrological process model was more suitable for basins with agricultural water resource exploitation and that the river discharge was significantly less than the natural discharge due to irrigation and reservoir filling, especially in drought years. Under the scenarios of high, middle and low water resource exploitation without ecological operations, agricultural development was unsustainable because of agricultural water shortages and ecological water scarcity. The evaluation of the guaranteed rates for the agricultural water supply and environmental flows showed that the low water resource exploitation scenario with ecological operations was the best option and that sustainable development could be achieved in the basin under this exploitation scenario in the future. However, implementing water management practices in the basin could result in certain economic losses. These losses could be offset by ecological protection funds for downstream wetlands. Overall, the model results could help to inform planning and investment decisions within the basin to improve the sustainable management of water resources.

Response of shelterbelt transpiration to shallow groundwater in arid areas

Shelterbelts play an important ecological function in arid irrigation land, while competing for water which otherwise supports crop growth. Estimation of shelterbelt water consumption from groundwater is essential to better manage shelterbelts in irrigation districts, but often a challenging task due to its geometry and varying accessibility to groundwater. In the study, sap flow of Populus popularis planted along an irrigation canal was measured during two growing seasons (2016–2017) to investigate its response to varying shallow groundwater. Considering the radial pattern of sap flux density (Js) and measurement azimuthal effect, corrected Js was adopted to better represent transpiration. The results indicate that increased soil moisture and groundwater table during irrigation periods with water flowing in the canal enhance relative Js of shelterbelt by 5.5–25.8% from the non-irrigation intervals. The threshold of groundwater depth (3.6 m) is identified, beyond which transpiration of the seven-year-old shelterbelt becomes very low. Greenbelt transpiration strongly depends on groundwater within the threshold, and can be estimated through an exponential function of the ratio of atmospheric demand and groundwater depth. Besides, with the decrease of reference evapotranspiration from June to September, the sensitivity of shelterbelt transpiration response to groundwater table depth was increased. This study provides necessary information to evaluate farmland shelterbelt transpiration for rational water resource allocation to meet the ecological water requirement in arid areas with shallow groundwater.