Water Dynamics And Numerical Simulation Of Farmland In Mu Us Sandland

Mu Us Sandland is located in semi-arid area, northwest China. It has arid climate,scarce rainfall, shallow groundwater level and fragile ecological environment. Thestudy area is located in Hailiutu River, where agriculture, livestock and mining isdeveloping well. But the water shortage has become a major obstacle restricting itseconomic development. In our research, we combined in-situ test and Hydrus-1Dsoftware together to study Mu Us Desert soil moisture dynamics and water flux.Through two years of research, we studied the relationship, changes and features ofwater flux of the water cycle during the spring maize growing course, and realized theusage and dynamic changes of farmland water. This paper reveals the mechanism ofwater consumption of crop and provides guidance for local agricultural production.Through in-situ test and numerical simulation, we got research results as follows.The depth of groundwater level is55.6-130cm in the study site. The hydraulicconnection between groundwater and plow layer is obvious. Furthermore, thestrongest correlation with groundwater is the soil layer above50-60cm from thegroundwater level.The main activity layer of maize roots is above50cm depth and the roots uptakewater mostly from about20cm depth. The water consumption of evaporation mainlycomes from the soil layer above40cm depth and little comes from the deep soil andgroundwater, while a large part of the water consumption by transpiration comes fromthe deep soil and groundwater. The appearance of zero flux plane during maizegrowing course is related to groundwater level, precipitation, irrigation and corngrowing.The evapotranspiration of corn changes with the growing stage. The proportionof evaporation during the early and late growing stages is greater than the stage whencorn grows rapidly. The transpiration gradually increases when maize starts growingrapidly. The soil water content changes with time. From seedling stage to dough stage,the soil moisture experiences the process of slow—violent—slow, and there is arelativity dry soil layer in the30-40cm depth. The soil moisture content decreases fastest at the depth of10cm and20cm, and it will emerge Hydraulic Lift when the soilwater potential value decreases to-0.15bar.The evapotranspiration rate of maize in2011and2012is580.32mm and411.7mm, respectively. The contribution of groundwater to the corn water usage is220.09mm and33.7mm, while the evaporation contributes31%and38.23%to thetotal evapotranspiration, respectively. Affected by meteorological factors and cropgrowing, the amount of evapotranspiration has much difference between2011and2012, the meteorological factors have different influence degrees ranging as windspeed> air relative humidity> net radiation≈day maximum temperature> dayminimum temperature. The amount of current irrigation will cause deep percolation,so the amount can be reduced to72%.Through the speculation of Hydrus-1D under the weather and maize growingconditions of2011, we find that the usage of groundwater will decrease and theirrigation will increase with the drawdown of groundwater, and when the water tabledrops to the depth of147cm, corn will not use groundwater any more, meanwhile, theamount of irrigation will get the maximum.