Advances in Hydro-Geological Research in Arid and Semi-arid Areas

(1) Background: In arid and semi-arid reservoirs, water surface evaporation is the main method of water dissipation in order to inhibit the evaporation of water and enhance economic efficiency. The evaporation inhibition rate of water-piled PV at different times of the year is derived from the anti-evaporation test of water-piled PV, and a new idea is proposed for water conservation in plains reservoirs in arid areas. (2) Methods: The test was conducted by dividing the area into groups A and B, with and without PV panel shading. In situ observation and numerical calculation were used to measure the atmosphere’s temperatures, test group, and PV module. The saturated water vapor pressure difference was then calculated according to Dalton’s principle to analyze the economic benefits of water saving. (3) Results: Based on the test results, it was found that the shading of PV panels had a cooling effect on the water body, the PV module, and the atmosphere. Group A showed a 44.2% decrease in the saturation water vapor pressure difference compared to Group B. The maximum evaporation suppression rate of 40.2% was observed in July, while the minimum rate of 12.2% was observed in January. The average evaporation suppression rate for the entire year was 29.2%. By utilizing the annual water savings for agricultural irrigation, it is possible to cover 38 hm² of land and generate a revenue of 39,000 CNY. (4) Conclusions: The photovoltaic water cover can effectively reduce water evaporation and generate economic benefits. Full article

Water yield and purification are important aspects of water ecosystem services, and achieving a balanced development of the two is necessary for the development of aquatic ecosystems. Using the InVEST model, the spatiotemporal variations of regional water yield and purification services in Shanxi, China, from 2000 to 2020 were analyzed. Three future scenarios (natural development, urban development, and ecological protection) were assessed for 2030 using the PLUS model. The results showed that in 2000–2020, the water yield of Shanxi Province in terms of space was generally low in the middle and northwest and high in the southeast, and it was affected by land-use change and climatic change. From 2000 to 2020, the water yield of Shanxi Province changed by 78.8 mm. In 2030, water yield will be highest under the urban development scenario (380.53 mm) and lowest in the ecological protection scenario (368.22 mm). Moreover, the water quality purification capacity improved, with nitrogen loading high in the center and low in the east and west. Due to the implementation of environmental protection policies and the improvement of the technical level, the nitrogen load was the highest in 2000 (0.97 kg/hm²) and lowest in 2015 (0.94 kg/hm²). By 2030, because of the high nitrogen loadings of cultivation and construction land and low nitrogen loadings of forests and grasslands, the nitrogen load was lowest under the scenario of urban development (0.94 kg/hm²) and highest under ecological protection (0.85 kg/hm²). Full article

Bangong Lake is a narrow and long lake in the arid region of the plateau in northern Tibet. The salinity of the east of the lake is different from that the west, resulting in differences in the natural environment and human living conditions on each side. Watershed hydrochemical analysis and spatial statistical analysis can help to understand regional hydrochemical evolution and water quality evaluation. In this study, the hydrochemical characteristics of surface water (glacier, river, and lake) and groundwater in the Bangong Co Lake Watershed were investigated to reveal the relationships between various water bodies. The drinking water quality index (DWQI) and USSL classification were applied to assess groundwater quality suitability for agricultural and drinking purposes. The hydrochemical characteristics show the differences among water bodies and their spatial distribution. The analyzed groundwater and surface water samples, such as river water and glaciers, were mainly Ca-HCO₃-type and the lake water was mainly categorized as Na-Cl-type with some Na-HCO₃-Cl type. The lake water’s chemical components are mainly affected by evaporative karst decomposition. The main mineralization process of groundwater and river water was related to the dissolution of reservoir minerals, such as dolomite and calcite, as well as halite. The drinking water quality index (DWQI) indicates that 79% of the groundwater samples in the study area were of good enough quality for drinking. In terms of irrigation water quality, the electrical conductivity (EC), calculated sodium adsorption ratio (SAR), and magnesium hazardous ratio (MHR) showed that more than 13% of the total samples were not suitable for irrigation. However, the USSL classification indicated that glacier and river water are relatively suitable for irrigation. Additionally, some groundwater and lake water has very high alkalinity or salinity, which is alarming when considering them for irrigation. Full article