Effect of highway greenbelt constrution on groundwater flow in a semi-arid region.

The highway greenbelt, vigorously promoted in arid and semi-arid areas, has obvious impacts on beautifying the environment, absorbing dust, reducing noise, and maintaining soil and water. Moreover, it affects the characteristics of how water resources are distributed and the regional groundwater cycle. However, the impact of highway greenbelt construction on groundwater flow in semi-arid areas is unknown. The Hubao Highway greenbelt in the north part of the Tumochuan Plain was studied as an example. The paper combines field investigation, remote sensing and mathematical modeling to quantify the impact of highway green space construction on regional groundwater circulation. The results showed that: Trees, shrubs and grasses were the dominant vegetation types in the landscaped area, accounting for 42.17% of the studied area. The total evapotranspiration water consumption of the green belt during the growing season was 471.35 × 104m3. The groundwater recharge in the study area was mainly derived from the lateral recharge in front of the mountain, and the main discharge was the evapotranspiration water consumption of the green belt. This evapotranspiration accounts for 3.31% of the total groundwater recharge. Under the condition that the recharge in front of the mountain remains constant, the evapotranspiration water consumption of the green belt will still have an increasing trend in the future. Appropriate planting of poplar and other high water-consuming trees may be the best way to mitigate the adverse effects of greenbelt evapotranspiration on groundwater resources. The results of this study provide valuable insights for environmental protection and infrastructure development in similar areas.

Effects of groundwater level decline to soil and vegetation in arid grassland: a case study of Hulunbuir open pit coal mine.

Coal mine in arid and semi-arid area is one of the most severely degraded ecosystems on the earth. The continuous decrease in groundwater level caused by coal mining will inevitably affect biogeochemical environment of the vadose zone, and then lead to the replacement of surface vegetation. Yimin open-pit coal mine was taken as an example to reveal the relationship between the groundwater depth and soil water content (SWC), soil salt content, soil electrical conductivity (SEC), soil organic matter (SOM), soil available potassium (SAK), soil available nitrogen (SAN), vegetation coverage, aboveground biomass and species richness. The results show that, the change of groundwater depth can affect soil properties and then change the characteristics of surface vegetation, and the change of surface vegetation can also react on soil properties. Vegetation coverage and aboveground biomass are negatively correlated with groundwater depth, and positively correlated with SWC, SEC, SOM and SAK. The shallow groundwater table is conducive to the accumulation of SOM, so that the surface biomass and vegetation coverage are high. The higher the surface biomass, the more the SAN is absorbed. Under natural conditions, the relative strength of biological nitrogen fixation and plant absorption determine the content of SAN. In the research area, when the depth of groundwater is less than 0.4 m will cause soil salinization, then lead to low species richness; Species richness is exponentially correlated with groundwater depth and decreases with the increase in groundwater depth.

Study on evolution of groundwater-lake system in typical prairie open-pit coal mine area.

Due to the drought climate and a large amount of groundwater drainage, there are widespread environmental geological problems in prairie open-pit coal mining areas, such as hydrological cycle imbalance, soil desertification and prairie degradation. This study takes the Hulunbeir Prairie Yimin Open-pit Coal Mine as the research object. Basing on the investigation of the groundwater-lake system in the mining area, data of hydrological, meteorological and remote sensing image, the mathematical model of groundwater level-lake area response mechanism in the mining area was constructed by using the principle of water balance. And the influence of mining area development on the lake area of Yimin basin had been predicted and analyzed. The results show that in the past 35 years of coal mining, the number of lake groups in Yimin basin has changed from 5 before mining (1982) to 2 (2018), and the total area of lakes has reduced from 6.94 km2 before mining to 1.43 km2 with an area reduction rate of 79%. The prairie lake-groundwater coupling model was constructed based on the principle of water balance, and the goodness-of-fit reached more than 0.83 after testing. Based on the model, it's predicted that when the Yimin Coal Mine is closed (2045), the area of Chaidaminol lake will shrink to 1.37 km2 under the condition of little fluctuation of climatic factors and stable mine development.

Spatial-temporal evolutions of groundwater environment in prairie opencast coal mine area: a case study of Yimin Coal Mine, China.

The interactions between groundwater and its environment was investigated in prairie mining area in this study, through the groundwater system evolutions in mining area before and after the mining actions (from 1973 to 2016) of Yimin coal mine. The results showed that (1) the mining activities of the open-pit coal changed the original reduction environment into the oxidizing environment in the mining area. The pyrite and sulfur-bearing coal in the stratum oxidized, produced acid and triggered a series of subsequent reactions, resulting in the decrease in the pH value of the groundwater in the mining area. The concentration of SO42-, Fe2+, Fe3+, Ca2+ and Mg2+ and the total hardness increased. The regional hydrochemical type evolved from HCO3-Na·Ca·Mg type before mining to the type of HCO3·SO4-Na·Ca·Mg after mining. (2) Coal mining strongly draining underground water accelerated the regional groundwater circulation, and then made the groundwater desalination. The concentrations of TDS, COD and Na++K+ in the mining area all showed a decreasing trend. (3) The coal mining activities made the calcite and dolomite in saturated state under the natural condition of underground water to be unsaturated again. The hydro-geochemical action evolves from double control (water-rock interaction and evaporation-concentration) to water-rock interaction control.