An integrated modeling system has been developed for analyzing the impact of climate change on snowmelt runoff in Kaidu Watershed, Northwest China. The system couples Hadley Centre Coupled Model version 3 (HadCM3) outputs with Snowmelt Runoff Model (SRM). The SRM was verified against observed discharge for outlet hydrological station of the watershed during the period from April to September in 2001 and generally performed well for Nash-Sutcliffe coefficient (EF) and water balance coefficient (RE). The EF is approximately over 0.8, and the water balance error is lower than ± 10%, indicating reasonable prediction accuracy. The Statistical Downscaling Model (SDSM) was used to downscale coarse outputs of HadCM3, and then the downscaled future climate data were used as inputs of the SRM. Four scenarios were considered for analyzing the climate change impact on snowmelt flow in the Kaidu Watershed. And the results indicated that watershed hydrology would alter under different climate change scenarios. The stream flow in spring is likely to increase with the increased mean temperature; the discharge and peck flow in summer decrease with the decreased precipitation under Scenarios 1 and 2. Moreover, the consideration of the change in cryosphere area would intensify the variability of stream flow under Scenarios 3 and 4. The modeling results provide useful decision support for water resources management.

In the 21st century, heavier rainfall events and warmer temperatures in mountainous regions have significant impacts on hydrological processes and the occurrence of flood/drought extremes. Long-term modeling and peak flow detection of streamflow series are crucial in understanding the behavior of flood and drought. This study was conducted to analyze the impacts of future climate change on extreme flows in the Kaidu River Basin, northwestern China. The soil water assessment tool (SWAT) was used for hydrological modeling. The projected future precipitation and temperature under Intergovernmental Panel on Climate Change (IPCC) representative concentration pathway (RCP) scenarios were downscaled and used to drive the validated SWAT model. A generalized extreme value (GEV) distribution was employed to assess the probability distribution of flood events. The modeling results showed that the simulated discharge well matched the observed ones both in the calibration and validation periods. Comparing with the historical period, the ensemble with 15 general circulation models (GCMs) showed that the annual precipitation will increase by 7.9–16.1% in the future, and extreme precipitation events will increase in winter months. Future temperature will increase from 0.42 °C/10 a to 0.70 °C/10 a. However, with respect to the hydrological response to climate change, annual mean runoff will decrease by 21.5–40.0% under the mean conditions of the four RCP scenarios. A reduction in streamflow will occur in winter, while significantly increased discharge will occur from April to May. In addition, designed floods for return periods of five, 10 and 20 years in the future, as predicted by the GEV distribution, will decrease by 3–20% over the entire Kaidu watershed compared to those in the historical period. The results will be used to help local water resource management with hazard warning and flood control.

The Ili River Delta (IRD) is the largest delta in the arid zone of Central Asia. Since the 1970s, the entire delta system has undergone a series of changes due to climate change and the impoundment of the Kapchagay Reservoir upstream of the delta, triggering an ecological crisis. Wetlands play a crucial ecological role in biodiversity conservation. Most studies have mainly focused on the response of vegetation and soil microbial to ecological changes in the delta, ignoring the dynamic processes of wetlands changes. Hence, such changes in the IRD and the underlying mechanisms need to be investigated in depth. In this study, wetlands in the IRD from 1975 to 2020 were extracted based on Landsat images using the object-oriented method; changes in the wetland area, wetland landscape pattern, NDVI, and NPP were analyzed; and the contributions of natural and human factors to wetland evolution were quantified. The results indicated the following: (1) From 1975 to 2020, the wetland area of the IRD showed an increasing trend, and changes in the wetland area were mainly found in the middle part of the delta near the Saryesik Peninsula. (2) The wetland landscape pattern in the IRD changed markedly from 1975 to 2020. The dominant patches of the wetland in the middle of the delta continued to expand; the patch aggregation index (AI) increased, and the landscape fragmentation index (LFI) decreased. (3) From 2000 to 2020, the average annual normalized difference vegetation index (NDVI) and net primary productivity (NPP) in the IRD increased, which is consistent with the change in wetland expansion. (4) Inflow to the delta from the Ili River and the water level of Balkhash Lake are significantly correlated with the wetland area, which are the dominant factors driving wetland evolution; and water evaporation from the Kapchagay Reservoir and irrigation water diversion on the left bank of the reservoir obviously intensified the process of lake water level decline and wetland degradation during 1970 to 1985. These results can provide scientific background for making informed ecological protection decisions in the IRD under the impacts of climate change and human activities.

Land use/cover change (LUCC) is becoming more and more frequent and extensive as a result of human activities, and is expected to have a major impact on human welfare by altering ecosystem service value (ESV). In this study, we utilized remote sensing images and statistical data to explore the spatial-temporal changes of land use/cover types and ESV in the northern slope economic belt of the Tianshan Mountains in Xinjiang Uygur Autonomous Region, China from 1975 to 2018. During the study period, LUCC in the study region varied significantly. Except grassland and unused land, all the other land use/cover types (cultivated land, forestland, waterbody, and construction land) increased in areas. From 1975 to 2018, the spatial-temporal variations in ESV were also pronounced. The total ESV decreased by 4.00×10⁸ CNY, which was primarily due to the reductions in the areas of grassland and unused land. Waterbody had a much higher ESV than the other land use/cover types. Ultimately, understanding the impact of LUCC on ESV and the interactions among ESV of different land use/cover types will help improve existing land use policies and provide scientific basis for developing new conservation strategies for ecologically fragile areas.

The Ili River Delta (IRD) is an ecological security barrier for the Lake Balkhash and an important water conservation area in Central Asia. In this study, we selected the IRD as a typical research area, and simulated the water yield and water conservation from 1975 to 2020 using the water yield module of the Integrated Valuation of Ecosystem Services and Tradeoffs (InVEST) model. We further analyzed the temporal and spatial variations in the water yield and water conservation in the IRD from 1975 to 2020, and investigated the main driving factors (precipitation, potential evapotranspiration, land use/land cover change, and inflow from the Ili River) of the water conservation variation based on the linear regression, piecewise linear regression, and Pearson’s correlation coefficient analyses. The results indicated that from 1975 to 2020, the water yield and water conservation in the IRD showed a decreasing trend, and the spatial distribution pattern was “high in the east and low in the west”; overall, the water conservation of all land use types decreased slightly. The water conservation volume of grassland was the most reduced, although the area of grassland increased owing to the increased inflow from the Ili River. At the same time, the increased inflow has led to the expansion of wetland areas, the improvement of vegetation growth, and the increase of regional evapotranspiration, thus resulting in an overall reduction in the water conservation. The water conservation depth and precipitation had similar spatial distribution patterns; the change in climate factors was the main reason for the decline in the water conservation function in the delta. The reservoir in the upper reaches of the IRD regulated runoff into the Lake Balkhash, promoted vegetation restoration, and had a positive effect on the water conservation; however, this positive effect cannot offset the negative effect of enhanced evapotranspiration. These results provide a reference for the rational allocation of water resources and ecosystem protection in the IRD.