| Land use change is one of the main factors affecting regional hydrological process,and its effect on water resources include the change of water quantity,water quality,water cycle and spatial distribution.Since agricultural water use is the main consumption sector of water resources in China,the interaction between land use structure and agricultural water use will directly affect the hydrological process of irrigation district.Irrigation district is a product of human economic activities,agricultural production is the largest water resources consumption activity in irrigation district,the difference of water consumption between different crops is significant,and land use(planting structure)change will have an impact on hydrological process.How to reveal and quantify the relation of these two factors are the hard parts in related research.Our study focused on flat artificial irrigation district,and we selected SWAT model to analyze the impact of land use(planting structure)change on hydrological process in Hetao Irrigation District,in order to reveal the relation between land use change and hydrological process.Our results show that:(1)This paper verifies the feasibility of applying SWAT model to simulate the influence of land use change on hydrological process in Hetao Irrigation District.(2)Human activity is the main factor causing land use change in irrigation district,among which,the change of planting area of crops is especially obvious.During the study period,agricultural land area decreased from 3764.6 km2 to 3734.7km2.Among which,wheat sown area experienced a sharp decline,from 2302.0 km2 in simulation-1990-1996 to 632.7 km2 in simulation-2006-2012,a 72.5% decrease.While sown area of maize and sunflower witnessed an upward trend,from 290.8 km2 and 1171.8 km2 in simulation-1990-1996 to 761.3 km2 and 1907.7 km2 in simulation-2006-2012,a 161.8% and 62.8% increase,respectively.When it comes to non-agricultural land use,wasteland area increased from 758.9 km2 in simulation-1990-1996 to 941.7 km2 in simulation-2006-2012,while pasture andconstruction land area decreased from 1852.0 km2 and 1060.0 km2 in simulation-1990-1996 to 1789.8 km2 and 959.9 km2 in simulation-2006-2012,respectively.(3)Planting structure is the main characteristic of land use change in irrigation district,and it will affect the evapotranspiration.The peak period of evapotranspiration is consistent with the growth period of main crops in irrigation district.The evapotranspiration(ET)of agricultural land is larger than that of non-agricultural land.Our simulated annual average ET of maize and sunflower increased from 0.2 billion m3 and 0.7 billion m3 in simulation-1990-1996 to 0.4 billion m3 and 1.0 billion m3 in simulation-2006-2012,a 147.7% and 47.4% increase,respectively.While that of wheat decreased from 1.1 billion m3 in simulation-1990-1996 to 0.3 billion m3 in simulation-2006-2012,a 70.8% decrease.And ET of non-agricultural land is rather small compared to ET of agricultural land,thus agricultural water use and water consumption are the main consumption items in Hetao Irrigation District.(4)Land use change will affect the amount of drainage,the downstream water quantity and the water input and output of the irrigation district.Seen from drainage volume,there is a large difference of drainage volume between two simulations.Total drainage volume and farmland drainage volume of Hetao Irrigation District in simulation-1990-1996 was 0.53 billion m3 and 0.47 billion m3,while that in simulation-2006-2012 was 0.40 billion m3 and 0.37 billion m3.Comparing farmland and non-farmland drainage volume,farmland drainage volume was significantly higher than non-farmland drainage volume,this is because there is a large water demand in crop growth period,farmland drainage come from not only precipitation but also irrigation water.Farmland drainage volume in simulation-1990-1996 and simulation-2006-2012 accounts for 89.4% and 91% of total drainage volume,respectively. |
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