Simulation Of The Precipitation Infiltration And Soil Moisture To Changes In Land Use In Da'an

Ecohydrology process has been affected along with the development of society economy and the influence of human activities. Land use change, as a hot topic in nowadays society, is an important typical factor in complex human activities which affect the ecohydrological environment. As the important contents of ecohydrology research, groundwater and soil moisture are distinct in response to land use change. While precipitation infiltration is an important form of groundwater recharge, and also impacts on the groundwater.Da'an City, located in the hinterland of Songnen Plain, lies in eco-fragile region, with drought and less rains. Soil salinization and desertification become more serious, and the ecological problems like groundwater table are getting worse. In this thesis, based on the experiments, combined with 3S technology and simulations of models, research on the ecohydrological response to changes in land use on precipitation infiltration and soil moisture simulation was carried out systematically.There were four remote sensing images of Da'an City in the year of 1989, 2000, 2004 and 2008. After image process and image interpretation with software named ERDAS IMAGINE, land use types were classified after interpretating and formed into land use change database. Land use distribution diagrams were drawn by ArcGIS desktop software. The areas of arable land, saline-alkalisoil and grassland were the top three. The results of single dynamic index models and transfer matrix model showed that the fastest decrease appeared in bottomland, and the fastest increase appeared in paddy fields. Saline-alkali soil conversed to plowland mainly followed by grassland, and there was no conversion into saline-alkalisoil.Combined with remote sensing images' data and references' data, the areas of arable land and water presented the trends which were decreased at first and increased at last. The maximum areas of arable land and water came in recent years, which connected to the water conservancy projects in Jilin Province.Based on the land use changes rules, a targeted selection of typical area was determined for surface soil samples' and profile soil samples' collections. Classical methods were use to test the amount of soil moisture, field capacity, bulk density, soil texture and particle grading in laboratory. With data obtained from experiments, the variations of surface samples in horizontal direction, and the changes of profile samples in vertical direction were analyzed. In study area, soil was divided into sand with the highest content distributing mainly in northwest and less in southeast, and silt and clay in the contrast distributions. For surface samples, the distributions of soil moisture, field capacity and bulk density were all more in northwest, southwest and mid-east. For profile samples, the changes trends of three parameters were almost the same. In forest and arable land, the amounts of three parameters were small, while in wild grass land and saline-alkali soil, the amounts were relatively high.Simulation on precipitation infiltration was run by SWAT model with data of meteorology, DEM images, land use and soil data. Method of precipitation infiltration coefficient was used to verified the accuracy of SWAT model and then to discuss the effects of groundwater recharge in different land use types. According to the outcomes, it was found the max infiltration value per unit went to forest, and the min value went to difficult utilization land. High precipitation infiltration coefficient of combination of land use and soil went to types named meadow-chernozem and meadow-meadow soil, and the lowest went to saline-alkali soil. Analogue value of average precipitation infiltration in 2008 was 58.75 mm, and analogue value of total precipitation infiltration was 2.65×108m3. The two values calculated by coefficient of precipitation infiltration were about 59.23 mm and 2.67×108m3 separately. The values from simulation and calculation of total precipitation infiltration in 2008 were higher than those in 2000, with a growing tendency.Simulation on the growth period of maize was operated by SWAP model with meteorological data, crop data, soil data and the amount of irrigation. And then the dynamic change process of soil water and the situation of water balance in root zoon with the depth of 100 cm under the ground were analyzed. The model was calibrated and tested by data of 2008 and 2009. The main sources of soil water were from precipitation and irrigation, and the consumption of soil water was canopy transpiration, soil evaporation, leakage, crop interception and changes of soil water storage in soil layer. In the growth period of maize, precipitation and irrigation were mainly used for canopy transpiration and soil evaporation. The consequences of simulation illustrated the amount of water flux at the bottom of soil column was so small. Just in the situation with a large amount of precipitation and irrigation, there was a small amount of leakage in deep soil layer, while most water was stored in soil layer. Although crop transpiration was strong in August and September which leads to severe change of soil water, soil water storage was still in a dynamic balance.In summary, on the basis of land use change characteristics, with laboratory experiments, precipitation infiltration and soil water dynamic changes were simulated by SWAT model and SWAP model.The research would lay the foundation for data base on groundwater and soil water responses to land use change, and could be used to be the theoretical bases of ecology and water source management for Da'an City with large changes on land use pattern in recent years.