The Research On The Adjustment Of Agriculture Structure And Sustainable Utilization Of Water Resources In Chinese Semi-arid Region

On the base of the data( 1961-2000) from 181 meteorological observation stations and national water resources bulletin, as well as related yearbooks, the current situation of water resources shortage and the severe situation of water resources of future are analysed,and the paper points out that reasonable adjustment of agricultural structure ,enhance water using efficiency of agriculture is one of the important ways to lighten the shortage of water resources,realize the sustainable utilization of water resources,retard drying tendency and increase the anti-drought capability of agriculture. The study results indicate: in the semi-arid region, the climate has a evident warning tendency in recent 40 years, especially in 1990's,such tendency is more obvious;meanwhile precipitation has a decreasing tendency,water shortage will be more severe in future,especially in growing season,water shortage will still be the main factor to restrict the agricultural production. The space-time distribution of Chinese semi-arid region surface water isn't even,the differences in a year are obvious; the differences of underground water between years are not so obvious as surface water,but it still has a decreasing tendency,especially in shanxi and sha'anxi provinces.There is a significant linear correlation between the precipitation and water resources in semi-arid region, the dynamic regularity of water resources is basically same as the dynamic regularity of precipitation. Acceding to the theory of crop water requirement, maximum potential evapotranspirations are calculated by applying FAO Penman-Monteith method,and then we obtain the water requirement ,water balance and watercorrection factors ect.of main crops(spring maize,summer maize,spring wheat,winter wheat,cotton)and different type grasslands,and the space-time distribution regularities of water requirement of cropland and natural grassland are analysed,the result show: the water requirements of same kind crop in different areas are different,water satified degrees are different to different crops in the same area,and water requirement of same crop are different between years for climatic variation;the water requirements of main crops are increasing from east to west and from south to north, water satified degrees are decreasing from east to west and from south to north. In growing season, there are deficits in crops water supply in most area,so the irrigation is needed to meet the requirement for crop growing normally. On the base of grain self-sufficiency,following natural laws,such as, the area where is suitable for tree to grow,we plant tree,where suitable for grass to grow we plant grass,or plant both tree and grass. Applying Linear Programming method,synthetically considering ecological benefit,economic benefit and social benefit,regarding minimizing the contradictory between water supply and requirement of agriculture,enhancing the capability of anti-drought,and decreasing the influence of drought as our aims, to provide theoretical bases and scientific methods for adjusting agricultural structure,returning cropland to woodland and grassland ,and utilizing water resources sustainablly,and improving ecological environment in semi-arid region.