Ecological Water Diversion Project Research Articles

Spatio-temporal variations and multi-scale correlations of climate, water, land, and vegetation resources over the past four decades in the Heihe River Basin

Study regionHeihe River Basin (HRB), Northwest China. Study focusThe study proposes an analytical scheme to identify trend, periodicity, and scale-correlation in climate, water, land, and vegetation resources over the past four decades using multivariate remote sensing data. New hydrological insights for the regionHeat and precipitation resources in the HRB have increased at rates of 14.27℃ yr−1 and 1.26 mm yr−1, respectively. The glacier area has decreased by 47.47 %. Additionally, the increase in upstream precipitation (2.82 mm yr−1) and glacier meltwater effectively replenishes runoff, soil water, and groundwater. The implementation of the ecological water diversion project (EWDP) in 2000 has contributed to enhancing runoff and lake storage capacity. The 9.28 % increase in vegetation cover (including cropland, forest, grassland, and shrubland) indicates an improvement in the hydrothermal conditions of the HRB. Additionally, the magnitude and direction of interactions among various natural resources vary across multiple spatial scales and time scales. The effect of hydrothermal coupling on vegetation is more prominent at the interdecadal scale. Vegetation growth in the upstream area is primarily influenced by thermal condition, while moisture plays a significant role in the midstream and downstream areas. Knowledge from this study contributes to the informed allocation of natural resources and offer policymakers valuable insights to enhance eco-environmental sustainability.

Effects of Ecological Water Diversion on Internal Nitrogen and Phosphorus Release in a Typical Small Shallow Lake in China

Ecological water diversion is an important method to improve water quality in lakes and reservoirs. But the environmental effects, from the ecological water diversion project (EWDP) to the internal release of sediment nutrients, remain unclear. In this study, an indoor simulation of an EWDP with different treatment scenarios with water transfer proportions of 25%, 50%, 75% and 100% was conducted to study the effects of water diversion on sediment nitrogen and phosphorus release in Lake Wanshandang. Our results showed that the flux of NH3–N released from the sediments in the western and eastern areas of Lake Wanshandang was significantly reduced after water transfer treatment, and the degree of reduction increased with increased water transfer. Specifically, the release flux of NH3–N in the sediment in the western area decreased from 18.02 mg/(m2/d) to −2.25 mg/(m2/d) when the transferred water reached 100% replacement of the original overlying water. The effect of water transfer treatment on the release flux of SRP from sediment varied greatly throughout the lake. After treatment, the SRP release flux in the western and central areas increased significantly, while it decreased in the eastern area. The NH3–N and SRP concentrations changed from 0.12–0.27 mg/L and 0.02–0.049 mg/L to 0.28–0.84 mg/L and 0.01–0.066 mg/L before and after the water transfer treatment. Our statistical analysis showed that the change in NH3–N and SRP release fluxes after treatment was significantly negatively correlated (p < 0.05) with concentrations of NH3–N or SRP in the overlying water before and after water transfer. We suggest the increase in NH3–N and SRP concentrations in the overlying water after the water transfer treatment led to the subsequent decreased NH3–N or SRP release flux, while the decrease in SRP concentration in overlying waters enhanced SRP release from the sediment. The differences in the concentrations of nitrogen and phosphorus between the original overlying water and the transferred incoming water are important factors affecting the release of nutrients from sediment.

Vegetation responses to ecological water delivery and prolonged droughts in an artificial desert oasis, Northwestern China

Irrational water usage in the middle reaches of inland rivers is detrimental to downstream oases, and the Qingtu Oasis is a typical downstream oasis that is degraded by water resource scarcity. The Qingtu Lake ecological water diversion project (EWDP) has restored the oasis, but the response pattern of different vegetation communities to environmental water and the dominant drivers of vegetation dynamics are not clear. Here, based on ground and satellite observations, this study investigated the spatial and temporal patterns of vegetation distribution and growth in the Qingtu Oasis from 2010 to 2022, and the reasons for the interannual variability in vegetation growth were also explained. The results showed that temporal variations in the distribution area of Phragmites australis (PA) followed a logistic curve after the EWDP, which increased rapidly from 2010 to 2019 and stabilized afterward. Meanwhile, the distribution area of Nitraria tangutorum (NT) presented a linear increase during the study period, with a 121.2% increase. Due to water inundation, the central region was occupied by PA communities, while NT communities moved to the edge. The spatial connectivity of PA patches increased significantly in contrast to the overall fragmentation tendency of NT patches in 2010–2022. The oasis tended to be homogenized and aggregated according to the morphological spatial pattern analysis, along with the landscape diversity and contagion indices. Enhanced vegetation growth, as indicated by the normalized difference vegetation index (NDVI), was observed in 76.1% of the vegetated lands, and the NDVI increasing rate was high near the canal. Using the random forest model, this study found that changes in groundwater depth were the most important driver of NDVI variability. The following influencing factors were atmospheric CO2 concentration, water inundation area and water delivery amount. In the absence of large increases in water delivery amount, oasis vegetation growth was susceptible to prolonged droughts. This study uncovers a nonlinear response of different vegetation communities to climate change and the EWDP in the downstream region of arid endorheic basins and identifies meteorological droughts as a key factor that should be fully considered in water delivery strategies. These findings lay a solid foundation for managing oasis restoration and water resource allocation in arid inland river basins.

The reallocation of water and ecosystem service values in arid ecosystems with the implementation of an ecological water diversion project

The rational allocation of the water resources in drylands and the scientific evaluation of their values are important for the regional sustainable development. We estimated the water consumption of each ecosystem in Ejina Oases in the arid area in northwest China based on the water balance equation, then assessed their ecosystem service values (ESVs) using the value per unit area method and the value equivalent factor per unit area method considering the cost of water consumption, respectively, and calculated their water productivities from 1990 to 2015. With the implementation of the ecological water diversion project (EWDP) in 2000, the deciduous broadleaf forest dominated by Populus euphratica had an increasing trend, meanwhile, lakes had a changing process from shrinking and drying up to recovery and expansion from 1990 to 2015. The total water consumption in Ejina Oases decreased from 5.26*108 m3 in 1990 to 4.79*108 m3 in 2000, and then increased continually to 5.97*108 m3 in 2015. The water consumption of forest, grassland and cultivated land hardly changed, while the water consumption of water or wetland changed obviously. The total ESVs estimated using the value per unit area method in Ejina Oases decreased from 1052.6 to 787.3 million ¥ in the period of 1990–2000, then increased to 1500.6 million ¥ in 2015, while the ESVs estimated using the value equivalent factor per unit area method decreased from 6368.7 million ¥ in 1990 to 5892.0 million ¥ in 2000, then increased to 7139.9 million ¥ in 2015, and the latter method was more reasonable. The results showed that the EWDP started in 2000 led to the reallocation of water resources and transfer of ESVs among ecosystems, which had obvious performance in the ecological environment and social economy. This study provided a comprehensive view of water use and management, ecological restoration and socio-economic development in this key ecological function zone, and will help decision-makers to formulate the scheme of rational allocation and efficient utilization of water resources in the basin.

Factors Influencing Seasonal Changes in Inundation of the Daliyaboyi Oasis, Lower Keriya River Valley, Central Tarim Basin, China

The ecological water diversion project (EWDP) in the Tarim River Basin, China, aims to allocate more surface water to downstream reaches to restore the degraded ecosystems. However, seasonal changes in ecological water diversion; the factors (natural and anthropogenic) controlling the ecological water diversion, whether the seasonal delivery of water temporally corresponded to the vegetation’s seasonal water demands; and the benefits of the ecological water diversion through overflowing surface water irrigation are unclear. To address the above issues, this study examines the intra-annual changes and its influencing factors in ecological water diversion (inundation) in the Daliyaboyi Oasis in the lower Keriya River valley within the Tarim Basin, discusses whether the seasonal delivery of water temporally corresponded to the vegetation’s seasonal water demands, and assesses the ecological benefits of overflowing surface water irrigation. Inundation was quantified by digitizing monthly changes in the inundated area from 2000 to 2018 in the oasis using 184 Landsat images. The results demonstrate that seasonal changes in the inundated area varied significantly, with maximum peaks occurring in February and August; a period of minimal inundation occurred in May. Differences in the July/August peak (i.e., July or August) in inundation dominated the inter-annual variations in the inundated area over the 19-year study period. The two peaks in the inundation area were temporally consistent with the vegetation’s seasonal water demand. Local residents have used ecological water to irrigate vegetation in different parts of the oasis during different seasons, an approach that expanded the inundated area. The February peak in the inundated area is closely linked to elevated downstream groundwater levels and the melting of ice along the river. The August peak is related to a peak in runoff from headwater areas. The minimum May value is correlated to a relatively low value in upstream runoff and an increase in agricultural water demand. Thus, natural factors control the intra-annual and inter-annual variations in the inundated area. Humans changed the spatial distribution of the inundated area and enhanced the water’s ecological benefits, but did not alter the correlation between peak periods of inundation and vegetation water demand. The results from this study improve our understanding of the benefits of the EWDP in the Tarim River Basin.

Closing the irrigation water productivity gap to alleviate water shortage in an endorheic basin

Closing the irrigation water productivity (IWP) gap is an effective approach to alleviating water deficits and ensuring food security. However, few studies have attempted to quantify the IWP gap and the potential benefits of closing it. This study adopted the Heihe River Basin, the second-largest inland basin in China, as a typical study area. The aims of this study were to: (1) assess the positive achievements and potential risks triggered by the Heihe Ecological Water Diversion Project (EWDP) according to multi-source and multi-scale measured data; (2) analyze potential approaches to improve the IWP and quantify the potential benefits that can be achieved by closing its IWP gap. The results of this study indicated that the EWDP effectively reallocated surface water resources, replenished groundwater in the lower reaches, and facilitated the recovery of oases and economic development in the downstream regions. However, this project has indirectly led to an imbalance in the groundwater resource between the middle and lower reaches, resulting in decline in groundwater levels and degradation of local vegetation in the midstream regions. In addition, the expansion of cultivated land in the midstream and downstream oases has resulted in the deterioration of farmland environment. The water transfer resulted in a deceleration in the growth of IWP from 2.44 % to 1.15 %, and the existing IWP gap was 1.43 kg/m3 between 1984 and 2017. This study predicted a future increase in the IWP to 2.01 kg/m3 with a reduction in the gap to 0.45 kg/m3 while maintaining food production. The potential for conserving water in the Heihe agricultural region can reach 552 million m3 by reducing the planting area by 10 %, improving irrigation water use efficiency by 20 %, maintaining existing agricultural film inputs, and reducing fertilizer application by 10 %. Following the research recommendations can greatly alleviate the agricultural water shortage and over-extraction of groundwater in the middle reaches and ensure meeting ecological water demand in the lower reaches. This study can act as a reference for sustainable management of an endorheic basin.

Water Resource Management Implications for a Desert Oasis From Tree‐Ring δ18O Variations in Populus Euphratica in Northwest China

AbstractPaleoclimatic data has often been applied to demonstrate the influence of anthropogenic activities on runoff to desert rivers, and such features as reservoirs are clearly known to influence available water in downstream riparian settings. The impact of human activities on the hydrology of a downstream desert oasis is, however, an open question. High‐resolution hydroclimate paleo‐reconstructions for desert oases are lacking, partly because paleoclimate proxies in extremely dry deserts are insensitive to extremely low precipitation. Here, we first attempt to reconstruct regional precipitation (r = −0.743, p < 0.001, n = 49) for the interval 1886–2009 from the stable oxygen isotope ratio (δ18O) of five Populus euphratica trees growing in the Ejina Oasis, on the lower reaches of the Heihe River in extremely arid Northwest China. The δ18O series for P. euphratica in the oasis (∼900 m a.s.l) abruptly increases relative to an δ18O series of Qinghai spruce (Picea crassifolia) growing in upper limit of forest (∼3,000 m a.s.l) in Longshou Mountain (middle reaches of the Heihe River) after about 2000, when the Ecological Water Diversion Project on the Heihe River was implemented. This finding implies that the Ejina Oasis suffered from serious drought during the last decade, or at least that the Oasis is stressed more than expected by current climate conditions. Other evidence also indicates that human activities contributed to a decrease in air moisture in the Ejina Oasis after 2000. To mitigate water stress on the oasis, we recommend some practical measures to ensure the rational development of the desert oasis.

Runoff controls the development of eco-hydrological and economic conditions in an arid oasis of the downstream inland river basin

Oasis degradation and terminal lake shrinkage are prevalent consequences of the disputed distribution of water resources in inland river basins, hindering regional sustainable development. The Ecological Water Diversion Project (EWDP) is regarded as an important measure to restore the desert-oasis ecosystem in inland river basins, and thus it is essential to comprehensively evaluate the response of eco-hydrological and socioeconomic systems to the EWDP. Based on multiple indicators, we used trend analysis, linear regression, partial least square regression, and structural equation model to disentangle the quantitative effects of the EWDP on the change of eco-hydrological and socioeconomic conditions in the Ejina Oasis (EO) in the lower reaches of the Heihe River in northwest China. Our results indicate that the ecological deterioration was prevalent before the execution of the EWDP, including the increase of groundwater depth, the disappearance of lakes, the decrease of NDVI. After the EWDP, runoff released to EO increased 69.15%, the mean groundwater depth decreased 0.48 m, 52.28% of the study area showed a significant increase in NDVI, areas of forest and grassland increased 20.17 and 25.65 km2, respectively. The EWDP improved the hydrological regime and prompted the recovery of the oasis. Besides, socioeconomic development was facilitated under the restoration of the eco-hydrological conditions, characterized by the expansion of farmland and the thrive of the tourism industry. The hydrological variables promoted the improvement of the ecological condition with a direct strength of 0.93 and facilitated the development of the socioeconomic conditions in EO with an indirect strength of 0.84. Runoff was the most important positive contributor both to the NDVI and GDP in EO. This comprehensive evaluation framework can offer valuable insight for water resources management and sustainable development in the inland river basin of arid areas.

Multi-Sensor Evaluating Effects of an Ecological Water Diversion Project on Land Degradation in the Heihe River Basin, China

To deal with the increasingly severe land degradation in the downstream of the Heihe River Basin(HRB) in northwest China, an Ecological Water Diversion Project(EDWP) was implemented since 2000. A comprehensive analysis of the effects associated with the project on land degradation is necessary. According to the concept of Land Degradation Neutrality (LDN), multi-sensor data has been used to extract information on Land Use/Land Cover (LULC), aeolian desertification, and vegetation dynamics, which were chosen as monitoring indices to reveal the process of land degradation in the HRB. Then, these results were combined with meteorological data, socio-economic statistics, and hydrological data to discuss the main driving factors influencing the land degradation process to evaluate the effects of the EWDP on land degradation in the HRB. The results showed that the process of land degradation in the HRB could be divided into two stages, in which the degradation trend was dominant from 1990 to 2000, and the rehabilitation trend was dominant from 2000 to 2015. Although both climate variation and human activities have been favorable to land degradation development in the HRB, climate factors have no significant influence on land degradation in the midstream and downstream in the HRB. The decrease of available water resources is the dominant driving factor of a series of ecological environment problems in the downstream of the HRB, and the land degradation process of the HRB has been stopped and reversed mainly attributed to the EWDP. The EWDP facilitated the recovery of the deteriorated ecosystem by improving the efficiency of surface water resources reallocation in the downstream. Still, the EWDP indirectly led to the sink of the groundwater table in the midstream with resulting in local vegetation degradation.

The impacts of the ecological water diversion project on the ecology-hydrology-economy nexus in the lower reaches in an inland river basin

This study aims to analyse the comprehensive effects of an ecological water diversion project (EWDP) and its driving mechanism since 2000 in Heihe River Basin (HRB) in Northwest China. We compared the hydrological, ecological, and socio-economic changes in the period of 1985–2015, revealed the relationships between them using linear regression method, and discussed their internal mechanisms referring to the long-term monitoring data, statistics data, field surveys and remote sensing data. We found that the hydrological regime in the region downstream of Langxinshan Hydrological Station (LXS region) in the lower HRB has changed, with an increase of annual discharge as well as obvious differences in the intra-annual distribution of monthly runoff. As a result, the groundwater level in most of the LXS region has risen, but the changes of the chemical characteristics of the groundwater were not significant. Meanwhile, the vegetation has been remarkably restored, and the water and wetland continually expanded suggesting that the degraded environment in the LXS region has gradually been rehabilitated. Additionally, the regional economy has developed rapidly, with a rapid increase of value-added tertiary industry due to the explosive growth of the tourist population. Along with the EWDP, other policies and projects have played an important role in restoring the ecology. The hydrological, ecological, and socio-economic systems have formed feedback loops in the LXS region, but there is still need to coordinate the relationships between water resource, ecosystem and socio-economy by considering water carrying capacity and water production efficiency and thinking of them as a nexus.

Assessing Underground Water Exchange Between Regions Using GRACE Data

AbstractQuantifying the underground water exchange between adjacent regions is a common question in field investigations and groundwater flow models. This paper proposes an innovative approach to assess underground water exchange patterns based on Gravity Recovery and Climate Experiment (GRACE) observations, the water balance method, and Darcy's law. The dynamic patterns of flux changes are investigated over four boundaries of an arid plain. Moreover, the causes of anthropogenic and climate factors are evaluated using the entropy method and the partial least squares regression (PLSR) model. The results indicate that terrestrial water storage (TWS) in the study area shows a decreasing trend at a rate of −1.77 ± 0.21 mm/yr from 2003 to 2015. The water resources recharging the study area from its southern boundary show a noticeable increasing trend, which is mainly attributed to the warming climate and increasing precipitation on the Qilian Mountains. The Ecological Water Diversion Project and the imbalance between precipitation and evapotranspiration are the main factors inducing the decline of flux changes for the northern, western, and eastern boundaries. Under the constrains of empirical values of hydrogeological parameters, GRACE‐based methods find that increment of the flux changes in the southern boundary may account for approximately 0.43% of the investigated flux in 2000, and the decrement of flux changes in the eastern boundary may be about 0.01% to the previous measured results. Anthropogenic activities are the dominant driving force for the changes in water resources, with the weight of 88.70%. The presented method can provide insights into the patterns of flux change in data‐poor areas.

An entropy-based investigation into the impact of ecological water diversion on land cover complexity of restored oasis in arid inland river basins

An improved understanding of the response of oasis ecosystems to ecological water diversion is essential for sustainably managing water resources in arid inland river basins. This entropy-based investigation provides new insight into the ecohydrological impacts of ecological water diversions through a case study of Qingtu oasis in the lower Shiyang River basin in Northwest China. Since 2010, an ecological water diversion project was put in place by Water Resources Bureau of Shiyang River Basin to restore the degraded Qingtu oasis. Annual cumulative water releases from this water diversion project had reached 0.25 billion m3 in 2018. This contributed to an increase in shallow groundwater level of 1.2 m. A combination of land cover classification indices and an entropy approach were used to assess the ecohydrological response to water diversion inputs. Land cover was classified as sparsely, lowly, moderately, and highly vegetated areas using Normalized Difference Vegetation Index (NDVI) calculated from Landsat images and the Excess Green minus Excess Red Index that was estimated from unmanned aerial vehicle images. Land cover complexity was evaluated using component complexity and spatial complexity. The component complexity corresponds to land cover composition and was assessed using the Shannon's entropy. The spatial complexity corresponds to spatial configuration of different land cover compositions and was analyzed using spatial entropy methodology. The rise in groundwater level caused by ecological water diversion drove the land cover transition and enhanced the component complexity. Field survey data showed that tendency and randomness co-existed in the spatial pattern of groundwater depth and its relationship with NDVI, which jointly affected spatial complexity (i.e., dependence and independence in spatial co-occurrences of different land cover categories). Results from this study improve understanding of the impacts that ecological water diversions can have on land cover evolution in natural oasis in arid inland river basins.

Partitioning groundwater recharge sources in multiple aquifers system within a desert oasis environment: Implications for water resources management in endorheic basins

The global expansion of irrigation-based agricultural practices is causing an overexploitation of groundwater resources. A thorough understanding of groundwater recharge processes is necessary for restoring groundwater and improving water resources management, especially in desert oasis aquifers in endorheic basins. In this paper, the Ejina Oasis in the downstream of Heihe River Basin was selected as the representative case for such an endeavor. Based on stable isotopes and end member mixing analysis, we found that the shallow groundwater was modern water, with 13% originating from local precipitation and 87% from river water infiltration. The semi-confined groundwater is a mixture of shallow groundwater (30%), lateral groundwater flowing from the middle Heihe River Basin (MHR; 52%), and confined groundwater (18%). Confined groundwater was old water formed in paleo-climatic humid and cold conditions. Shallow groundwater levels were restored substantially after implementation of the Ecological Water Diversion Project (EWDP) began in 2000 in the Heihe River Basin, but the semi-confined groundwater levels still declined slowly. These different responses to EWDP are attributed to the differences in primary recharge sources of the two aquifers. Because river water infiltration was the main sources of shallow groundwater, increases in river discharge into the Ejina Oasis resulted in increased shallow groundwater levels over a short time scale. Continued over-pumping of groundwater for irrigation in the MHR reduced lateral groundwater flow into the lower Heihe River Basin, which was the primary source of semi-confined groundwater. For successful groundwater restoration and maintenance of groundwater for the future, EWDP implementation must integrate water management of river water and groundwater diversion across the whole basin. Our results can provide useful information on policy decision makers for sustainable use of water resources in the oases of other similar watersheds around the world.

Runoff variation characteristics, association with large-scale circulation and dominant causes in the Heihe River Basin, Northwest China

The water resources in arid and semi-arid regions are critical to providing reliable sources of water for food production and ecosystem functioning. In this study, continuous wavelet transform and wavelet coherence were used to analyse the runoff periodicity and relationship with climate indices, respectively. Additionally, the double mass curve (DMCD), the slope changing ratio of cumulative quantity (SCRCQ) and the Choudhury–Yang equation (Budyko-CY) methods for different potential evapotranspiration data (E0(E0-20 cm, E0-PM, E0-H)) were used to separate the impacts of climate changes and anthropogenic activities on runoff variations. The results demonstrated that the flow regimes in high and low flow seasons were not obvious shifts, and that after implementation of the Ecological Water Diversion Project (EWDP), ecosystems were gradually restored in the downstream portion of the Heihe River Basin (DHRB). Periodicities of 1–7 years and 1–5.8 years were detected in Yingluoxia and Zhengyixia, respectively. Additionally, on a 1–148.2 month timescale, the monthly runoff with AO, NAO, PDO, and AMO had significant resonance periodicity and a 1–48 month Spearman's lag correlation. On the annual and high-flow, climate changes dominant determinant to an increase of runoff for the DMCD and Budyko-CY in period 2, SCRCQ and Budyko-CY in period 3 for different E0 in the upstream (UHRB). In the midstream (MHRB) region, anthropogenic activities played a dominant role in deducing the runoff by the SCRCQ and Budyko-CY methods for different E0 values in period 3. During the low-flow season, the impact of human activities in the UHRB and climate changes in the MHRB was significant for period 2 and 3. Therefore, the impacts of climate change and human activities on runoff changes caused by the introduction of different E0 on different timescales should be fully considered in the future.

Estimating Dynamics of Terminal Lakes in the Second Largest Endorheic River Basin of Northwestern China from 2000 to 2017 with Landsat Imagery

Quantifying terminal-lake dynamics is crucial for understanding water-ecosystem-economy relationship across endorheic river basins in arid environments. In this study, the spatio-temporal variations in terminal lakes of the lower Heihe River Basin were investigated for the first time since the Ecological Water Diversion Project commenced in 2000. The lake area and corresponding water consumption were determined with 248 Landsat images. Vital recovery of lakes occurred two years after the implementation of the project, and the total lake area increased by 382.6%, from 30.7 to 148.2 km2, during 2002–2017. East Juyan Lake (EJL) was first restored as a project target and subsequently reached a maximum area of 70.1 km2. Water dispersion was initiated in 2003, with the East river prioritized for restoration. Swan Lake in the East river enlarged to 67.7 km2 by 2017, while the other four lakes temporarily existed or maintained an area < 7 km2, such as West Juyan Lake. Water consumed by lakes increased synchronously with lake area. The average water consumption of the six lakes was 1.03 × 108 m3/year, with 63% from EJL. The increasing terminal lakes; however, highlight the seasonal competition for water use between riparian vegetation and lake ecosystems in water-limited areas.

Assessment of river network water quality based on sluice gate control strategy in Wenzhou

Nowadays, an ecological water diversion project is executed in Wenzhou city for the purpose of river network water quality improvement. Due to the flow rate of the water diversion project is relatively low, the utilization of sluice gates along Oujiang River becomes important, which can help to accelerate the flow velocity and redirect the water flow in river network. In this study, an experiment is designed and executed near Huiqiao sluice gate, both water flow and water quality are observed at three monitoring sections before and after the sluice gate’s opening. The comparison between background and measured data shows the improvement of water quality in experimental area, which confirms the function of Huiqiao sluice gate. A comprehensive sluice gate regulation and control plan is anticipated in the future to further improve the river network water quality in Wenzhou city.

Exploring responses of lake area to river regulation and implications for lake restoration in arid regions

Many of the world’s lakes in arid endorheic basins are shrinking at alarming rates, reducing habitat and economic benefits. Lakes are commonly recovered by river regulation. However, the scarcity of water has hindered the restoration of lakes in arid regions. There is therefore an urgent demand for insight into efficient and sustainable restoration of lakes. Here a water mass balance model was used to explore the impact of flow regulation scenarios on the restoration area of East Juyan Lake (EJL), which is located in an arid zone of China. Then a fractional water loss index was introduced to examine the water storage efficiency of the lake. Results showed that the lake ecosystem has been effectively restored due to the increased streamflow entering the lake caused by the Ecological Water Diversion Project; the dynamic recovery process of lake area is related to the initial area, and streamflow input and evaporation jointly determine the lake equilibrium. Affected by lake topography, fractional water loss index responded nonlinearly to the lake area. Based on these, we determined the appropriate restoration area of 42 km2, and a discharge of 0.608 × 108 m3 of water must be maintained continuously every year to sustain this area. This paper has provided an efficient way to restore and manage lakes at their suitable size by river regulation and water transfer projects, which are important in helping policy makers make robust decisions to facilitate sustainable development in arid regions.

Wind erosion reduction by water diversion in the lower Heihe River Basin, Northwest China

AbstractThe lower Heihe River Basin, a key ecological function zone in Northwest China, has suffered from serious land degradation by wind erosion for decades, posing a great threat to the national ecological safety. This study explores the dynamics of wind erosion and the soil conservation service (SCS) in this region following water diversion during 2001–2010 with the statistic model of wind erosion on small watershed basis based on remote sensing, climate, and soil data, and impacts of driving factors on the SCS are revealed with scenario analysis. Results suggest that the SCS represented by the soil retention amount was less than 500 t km−2 yr−1 in most parts of the study area and higher than 15,000 t km−2 yr−1 in a few wind erosion hotspots, including the East Juyanhai region, Dingxin Oasis, Ejina Oasis, and its surrounding desert–oasis transitional areas. The cumulative potential soil loss of the study area increased much faster than the cumulative soil retention amount, and fractional vegetation cover influenced by the Ecological Water Diversion Project played a dominant role in improving the SCS, accounting for 82.25% of the change in the SCS of the study area. Climate change played a subordinate role, but there were essential separate and interactive effects of climate factors on the SCS. This study provides a preliminary overview of hotspots of wind erosion and the SCS in the lower Heihe River Basin from a geographical perspective, laying a solid basis for combating land degradation by wind erosion in arid regions of Northwest China.

Analysis of the ecological water diversion project in Wenzhou City

As a developed city in China, Wenzhou City has been suffered from bad water quality for years. In order to improve the river network water quality, an ecological water diversion project was designed and executed by the regional government. In this study, an investigation and analysis of the regional ecological water diversion project is made for the purpose of examining the water quality improvements. A numerical model is also established, different water diversion flow rates and sewer interception levels are considered during the simulation. Simulation results reveal that higher flow rate and sewer interception level will greatly improve the river network water quality in Wenzhou City. The importance of the flow rate and interception level has been proved and future work will be focused on increasing the flow rate and upgrading the sewer interception level.

Assessing the impacts of an ecological water diversion project on water consumption through high-resolution estimations of actual evapotranspiration in the downstream regions of the Heihe River Basin, China

Ecological Water Diversion Projects (EWDPs) have been implemented in several endorheic river basins in the arid region of northwest China since the beginning of the new millennium to restore the deteriorated ecosystems. However, the effects of these EWDPs are difficult to evaluate quantitatively. Here, we assessed changes in water use in Ejin Oasis in the downstream region of the Heihe River Basin, which is a typical endorheic river basin in northwest China, based on the estimated evapotranspiration (ET) during the growing season (May to October) in 2000 (before the EWDP) and 2014 (after the EWDP). The ET estimates were based on the modified surface energy balance algorithm for land (M-SEBAL) model and Landsat images. The estimated ET was validated against observations using eddy covariance towers installed on different landscapes in 2014 and was found to have a root mean square error of 1.20mmday−1 and a coefficient of determination of 0.67 at the footprint scale on satellite overpass days. The estimated ETs in two years were also compared with another remote sensing product that showed a similar spatial pattern, with a spatial mean difference of 4mm and 0.5mm, respectively. The estimated ET was then used to evaluate the impact of the EWDP on water consumption. The ET over different land use and land cover types increased, with a mean increase of 52% over the 15 years of the implementation of the EWDP in Ejin Oasis. The water consumption in Ejin Oasis in 2014 was approximately twice that in 2000. Among the changes, water consumption by croplands increased significantly, with a maximum increase of 264% because of cropland expansion and increased ET. The increases in water consumption by forests and grasslands were 60% and 25%, respectively. The lake area expanded drastically (from 0 to 37.46km2), and the corresponding water consumption caused by evaporation was zero in 2000 and approximately 3.9×107m3 from May to October in 2014. This work demonstrates that estimates of the ET based on remote sensing can be used as reliable indicators for comprehensive assessments of the impacts of the EWDPs.