Study On The Soil-water Movement With The Drip Irrigation Under Mulch In Arid Regions

In arid regions, especially the northwest of China, as water shortages, extreme climate and fragile ecological environment, there were many ecological and environmental problems everywhere, such as land salinization, water table rise and water quality problems, which were caused by water resources development and utilization. For groundwater level rise caused by the use of water resources in the western, the laws of water movement under irrigation need to be understood. In this study, Karamay Agricultural Comprehensive Developmental Region saline in Xinjiang was taken as an example to study the laws of water movement. From June2010to September2010, soil water movement in vadose zone is studied, by monitoring precipitation, soil water potential, soil water content, depth to water table and meteorological factors, sampling precipitation, soil water, groundwater and irrigation for hydrogen and oxygen isotope test.In order to understand the laws of water movement in arid regions, we installed three tensionmeter systems, which includes18ceramic cups, in Karamay Agricultural Comprehensive Developmental Region. The results showed that:in arid regions, soil water potential diversifies intensively in vadose zone, so there is good environment for zero flux potentials to develop. There is one zero flux potentials below the surface of120cm in vadose zone which is Convergent Zero Flux Plane. This Zero Flux Plane is stable during the study period, illustrating that the uptake by plant roots makes the water content changes smaller. In the horizontal direction, soil water moves toward the drip.By analyzing the hydrogen and oxygen stable isotopes in precipitation, irrigation water, soil water, groundwater, soil water isotopes have obvious stratification. The isotopes of soil water is enriched in100cm of soil profile and the isotopes of soil water is relatively depleted between120to150cm of soil profile. Most stable isotopes of soil water fall to the right of the fitting line of precipitation indicating that soil water through a strong evaporation. The irrigation water recharges the groundwater through the8D—δ18O distribution map.Finally, using HYDRUS-1D model simulates the soil water movement in vadose zone after irrigation. From the simulation results, the model simulates much better, reflecting the changing trends of soil water potential. But the model simulates poor in a more intense period of dynamic change of soil water potential. and this may be related with the application of soil hydraulic conductivity rate of valuation. Actually, the soil hydraulic conductivity is a function of soil water content.