Understanding groundwater-vegetation interactions is crucial for sustaining fragile environments of desert areas such as the Horqin Sandy Land (HSL) in northern China. This study examined spatio-temporal variations in the water table and the associated vegetation status of a 9.71 km² area that contains meadowland, sandy dunes, and intermediate transitional zones. The depth of the water table and hydrometeorologic parameters were monitored and Landsat Thematic Mapper (TM) and Moderate Resolution Imaging Spectroradiometer (MODIS) data were utilized to assess the vegetation cover. Spatio-temporal variations over the six-year study period were examined and descriptive groundwater–vegetation associations developed by overlaying a water table depth map onto a vegetation index map derived from MODIS. The results indicate that the water table depends on the local topography, localized geological settings, and human activities such as reclamation, with fluctuations occurring at annual and monthly scales as a function of precipitation and potential evapotranspiration. Locations where the water table is closer to the surface tend to have more dense and productive vegetation. The water table depth is more closely associated with vegetative density in meadowlands than in transitional zones, and only poorly associated with vegetation in sandy dunes.

This study addresses challenges such as insufficient irrigation water quotas, severe groundwater over-extraction, and conflicts around crop water usage within the mixed-cropping areas of the Inner Mongolia Yellow River Basin. Five evaluation factors—water resource utilization efficiency, irrigation rate, degree of development and utilization, supply modulus, and demand modulus—were selected for a gray relational analysis to assess the 2023 water resource carrying capacity. A crop structure optimization model was developed using machine learning, focusing on minimizing water use while maximizing economic benefits. The results indicate that groundwater resources are nearing critical levels, with many regions showing low carrying capacities and supply–demand conflicts. Key issues include unreasonable planting structures and excessive irrigation quotas, leading to significant water waste. To optimize resource utilization, it is recommended to reduce the food crop planting area by 0.0194 × 10⁴ hm² and increase economic and forage crops by 0.0106 × 10⁴ hm² and 0.0116 × 10⁴ hm², respectively. This adjustment would lead to a total water utilization reduction of 0.0289 × 10⁶ m³ per year, an increase in total yield of 4340.86 tons, and an increase in total economic benefit of CNY 6,559,200, thus leading the cropping structure towards greater rationality. The findings provide valuable insights for optimal water resource allocation in mixed-cropping irrigation areas.

Understanding historical trends in temperature, precipitation, and runoff is important but incomplete for developing adaptive measures to climate change to sustain fragile ecosystems in cold and arid regions, including the Balagaer River watershed on the Mongolian Plateau of northeast China. The objective of this study was to detect such trends in this watershed from 1959 to 2017. The detection was accomplished using a Mann-Kendall sudden change approach at annual and seasonal time scales. The results indicated that the abrupt changes in temperature preceded that in either runoff or precipitation; these abrupt changes occurred between 1970 and 2004. Significant (α = 0.05) warming trends were found at the minimum temperatures in spring (0.041 °C a⁻¹), summer (0.037 °C a⁻¹), fall (0.027 °C a⁻¹), and winter (0.031 °C a⁻¹). In contrast, significant decreasing trends were found in the precipitation (−1.27 mm a⁻¹) and runoff (−0.069 mm a⁻¹) in the summer. Marginally increasing trends were found in the precipitation in spring (0.18 mm a⁻¹) and fall (0.032 mm a⁻¹), whereas an insignificant decreasing trend was found in the runoffs in these two seasons. Both precipitation and runoff in the wet season exhibited a significant decreasing trend, whereas in the dry season, they exhibited a marginally increasing trend. Sudden changes in spring runoff and sudden rises in temperature are the main causes of sudden changes in basin rainfall.