Adding a series of surface-water transfer projects still cannot solve the current water shortages in the arid area of northwestern China. Selecting a rational allocation plan for the water resources is the key to coordinating water use for the national economy and ecological environment. In this study, taking the Wuwei Basin as the study area, long-term data of source-sink terms from 2007 to 2018 were analyzed. Following the calibration and validation of the numerical simulation model of the groundwater system, the data was highly fitted. Based on this model, the groundwater system balance, water level variations, and suitable ecological water level area in 2050 under four water resource allocation plans were compared. Under plan 4, the groundwater resources change from an average decrease of 7656.4 × 104 m3·yr−1 from 2007 to 2018, to an increase of 4624.6 × 104 m3·yr−1 in 2050, which means the groundwater systems are almost in a positive balance state. Compared with 2018, the water level with small groundwater depth drops by 2.2–5.7 m, while that with large groundwater depths steadily rises by 2.7–8.6 m. In addition, it can maintain the 9 km2 natural oasis wetland area and the 116 km2 well-growing natural vegetation area, which can effectively promote the benign evolution and efficient, balanced sustainable development of the regional water resources, economy, and ecological environment.

Unsaturated zones are critical for water and material exchange between groundwater and surface ecosystems. Understanding the migration patterns of soil water and salts in these zones can offer theoretical support for maintaining the equilibrium between groundwater and surface ecosystems in Northwestern China’s salinized regions. This study explores the correlation between soil particle composition and soil water and salt distribution at a test site in the lower reaches of the Shiyang River basin. It analyzes the way in which water and salt patterns vary with different soil structures over various timescales. The results indicate that lithological profiles with similar structures but varying fine particle contents exhibit distinct water–salt variation patterns. Higher fine particle content leads to increased water and total dissolved solid content, but a decreased infiltration rate. When the middle layer has the highest fine content, soil evaporation is partially inhibited. The more complex the lithologic structure, the less effective irrigation is in leaching salt. However, when the lithologic structure remains constant, fine particle content has minimal impact on salt leaching.

The impacts of land use/cover changes (LUCCs) on groundwater resources are a global issue. The Shiyang River Basin of China is a typical, ecologically fragile area. Focusing on the Wuwei sub-basin of the central plain, this study analyzed typical remote sensing image data for 17 specific dates since 1970. Before the Comprehensive Treatment Program in 2007, the area of natural oases decreased at a rate of 16.25 km2/year, while the area of farmland expanded at a rate of 13.85 km2/year. The farmland expansion preferentially occurred in low-vegetation-coverage oases, where the groundwater depth increased from 4 to 20 m. The consumption of groundwater increased from 7319.5×104 m3/year to 12,943.2 × 104 m3/year. During the period 2008–2018, the areas of both the natural oases and farmland decreased at rates of 2.57 km2/year and 8.99 km2/year, respectively. The groundwater level rose significantly in the south and west, as well as near the main river channel. Groundwater consumption has been restored to 7270.4 × 104 m3/year. Only 0.12 km2 of every 1.17 km2 of the original natural oases were restored through the natural farmland–natural oases conversion process. Groundwater depth increased significantly with the continuous expansion of farmland. Since the farmland area was effectively controlled, the trend of groundwater-level decline was significantly improved. These findings provide scientific support for the ecological restoration and reconstruction of oases, as well as an efficient and balanced development of river basin water resources.