Study On Groundwater Recharge Mechanism In Luochuan Loess Tableland Base On Environmental Isotope

Groundwater resources are an important component of water resources and account for a large proportion of water use.In the loss tableland region where resources are scarce,groundwater resources are more precious.In this study,the isotopic composition and chloride ion concentration of different water bodies(precipitation,soil water and groundwater)were analyzed by using hydrogen and oxygen stable isotope technique and C hloride mass balance method in Luochuan loess tableland region in central Loess Plateau.Explore the source of precipitation,groundwater recharge mechanism and the effcts of land use on groundwater recharge.1.The hydrogen and oxygen isotopic composition characteristics and vapor source were studied in detail.There are seasonal effects,rainfall effects and temperature effects on the precipitation of isotopes in different time periods by different environmental factors and water vapor from different sources.The analysis of regional atmospheric precipitation line equation and deuterium surplus shows that there are more sources of precipitation and water vapor in Luochuan region,and there are differences between years and years.Precipitation water vapor will be affected by the westerly circulation,the Indian Ocean monsoon and the Pacific monsoon,and the impact of the westerly circulation.2.The soil water status and soil moisture migration in the Loess Plateau region.Shallow soil moisture is affected by precipitation recharge and evaporation.The deep soil is affected by the land use.The isotopic composition of the soil profile confirms the existence of two forms of water transport in the deep soil supplemented by soil water infiltration and precipitation.The chloride ion concentration in the soil profile is limited by the land use pattern and the deep chloride ion is more stable.3.The mechanism of groundwater recharge in and the impact of land use in the Loess Plateau region.The recharge of groundwater in the study region is mainly composed of deep soil water infiltration,and there is also direct supply of groundwater to precipitation.The total recharge rate calculated from the chloride ion mass balance method is 120 mm / yr,which accounts for 20% of the annual rainfall.Land use patterns change the formation of bio-use dry layer seriously hampered the soil underwater water supply to groundwater.