GIS-based Study On The Water-constrained State Of Arable Land In Hilly And Mountainous Region

The total water resources and its use efficiency are the key factors for the agriculture production in the use of arable land. Though being abundant in precipitation and water resources in hilly and mountainous region of southwest China, it always be threatened by serious drought. The complex topography was an important factor which influence the water use on arable land. Considered the water-constraint by the topography of the hilly and mountainous region, this study analyzed the influence of topography on the evaporation of the soil-water in the soil-water cycle, the soil water storage and the interflow in the surface of soil water in the first distribution of the water resource on arable land according to the soil water cycle mechanism on arable land of hilly and mountainous region. Based on the analysis, this study presented a calculated method for the cost of the cultivated land irrigation on account of topography to analyze the irrigation water constraint by the topography. Taking the Li Xiangxi wateshed as case, this study build a level evaluation model combined the soil water cycle mechanism and the topographical characteristic based on the DEM data, land use data, soil data and hydrology data, and also comprehensively assessed the water constrained state of arable land in the hilly and mountainous region using multi-factor weighting method after extracting the constraining factors by GIS,then analyzed the time series of construction of a high standard of basic farmland using the quadrant method and multidimensional weighted degree method according to the water-constrained state. The conclusions are as follows:(1) The water-constrained state was classified to five grades as mild, medium, intense, severe and very severe. The mild water-constrained arable land accounted for just 0.47% of the total arable land,and the medium and intense water-constrained arable land accounted for 79.26% which were abundant in arable land resources to explore agricultural construction but been threaten by the drought seriously. The severe and very severe water-constrained arable land accounted for 13.55%, 6.72% separately.(2) Based on the survey of 1170 samples, the correct rate of the analysis was 78%. The correct rate decreased with the decrease of water-constraint grade, the correct rates from very severe to mild were 85%, 81.67%, 78.33%, 75% and 68.33%.(3) The arable land with irrigation condition accounted for 88.23% of the total arable land, and the area of which with no irrigation were 52.62 km2. The miner water constrained arable lands were near the source of the water, but its converse cannot be true. Under the constraint of the irrigation cost, the practical irrigation decreased 29 %, and the area of arable land which cannot be irrigated effectively was 44.35 km2.(4) The analysis on spatial-temporal structure of high standard farmland construction showed that the area of arable land which can be explored positively was 76.16 km2. And there are 8 priority of construction zones with an area of 54.95 km2. The result of priority ordering using multidimensional weighted degree method showed that the priority list of the 8 construction zone was as follow: The Longtan Town district, the northern Linshi Town district, the Tongle Town district, the southern Linshi district, the southern Dashun district, the Qianfeng Town district, Zengfu Town district, Dashun town district.