Agricultural Irrigation Water Requirement In Response To Changing Environment In Jingdian Irrigation District Of Gansu Province

In recent decades,the safety of agricultural water use is getting into a serious situation due to the dual effects of climate change and human activities,which limits the development of a"griculture in irrigation areas.The water demand for agricultural irrigation in irrigation areas is closely related to the safety of agricultural water use.Therefore,it is a great theoretical significance and guiding role to establish the research on the impact of the environment change on irrigation water demand in irrigation district,to determine reasonable agricultural planting structure in irrigation districts,to ensure the safety of agricultural water use,and to promote the sustainable development of agriculture In this paper,The Jingdian irrigation district in Gansu Province as the research object.Based on the review of relevant literature,the response of agricultural irrigation water demand to the changing environment in Jingdian Irrigation district is researched by the combination of theoretical analysis and model calculation method in this paper,And propsed the agricultural water use strategies to respond to changing environment.The main results obtained are as follows:(1)The climate tendency method and the sliding average method are used to analyze the temporal evolution of environmental factors in the irrigation area.The Mann-Kendall trend test method is used to test the average temperature and precipitation of the irrigation area,and the wavelet analysis method is used to analyze the cycle of precipitation in the irrigation area.The results show that:Firstly,the average temperature and wind speed in the irrigation area are increasing over the years.Secondly,the changing trend of the relative humidity and sunshine hours is not obvious.Thirdly,the average temperature increase trend is significant and has instability.The precipitation has obvious cyclical changes,and these changes are 7 years,13 years and 28 years respectively.Moreover,the precipitation in the cyclical period of 13 years is the strongest.Finally,the climate of the irrigation area is changing toward the warming trend.And the total planting area of the irrigation area is increasing,the ratio of food crops is decreasing,and the ratio of economic crops is increasing.(2)The water requirement of reference crops in the irrigation area is calculated by using the P-M formula,the agricultural irrigation water requirement in the irrigation area is also calculated according to the agricultural data of the irrigation area.The time characteristics of total agricultural irrigation water demand and irrigation water demand of different crop types in irrigation districts were analyzed.The ArcGis software was used to study the spatial variation of total agricultural irrigation water demand and irrigation water demand of different crop types in different typical hydrological years.The results of researches display that the total agricultural irrigation water demand in irrigation districts show a significant increase trend for many years;the irrigation water demand for summer crops show a decreasing trend,but the irrigation water demand for autumn crops show an increasing trend.In addition,the irrigation water demand for economic crops and forest fruit crops didn't change a lot.The spatial distribution characteristics are listed below:1)The areas with large total agricultural irrigation water demand are distributed in the southeast and northwest of the irrigation area for many years.2)The areas where need large irrigation water resource for summer crops and economic crops are distributed in the northwestern part of the irrigation area.3)The areas with the large irrigation water demand for autumn crops are distributed in the southeast and northeast of the irrigation area.(3)The spatial distribution characteristics of different crop types in different typical hydrological areas are:1)In the 25%rainy year,the summer crops and autumn crops areas which need large irrigation water demand are distributed in the northwest and southeast of the irrigation area,and the economic crops area which needs large irrigation water demand is distributed in the northwestern part of the irrigation area.The fruit crops area which has large irrigation water demand is distributed in the southeastern part of the irrigation area.In the 50%normal year,the summer crops area with large irrigation water demand is distributed in the northwest of the irrigation area.The autumn and winter crops and economic crops which have large irrigation water demand is distributed in the northeast and southeast of the irrigation area,and the forestry crops with large irrigation water demand is distributed in the southeast.In the 75%dry year,The summer crops areas with large water demand are distributed in the northwest and southeast of the irrigation area.The areas with large irrigation water demand for autumn and winter crops are distributed in the northwestern,northeast and southeast,of the irrigation area,and the area of economic crops with large irrigation water demand is distributed in the northwest of the irrigation area.In the north and southeast,the areas where the irrigation water demand for forest fruit crops is larger are distributed in the northeast and southeast of the irrigation district.(4)The relationship between environmental factors and agricultural irrigation water demand was studied by path analysis method and principal component regression method,and the corresponding regression model was established.The results show that:1)Among meteorological factors,precipitation has the greatest impact on agricultural irrigation water demand,and followed by relative humidity,sunshine hours,average temperature and wind speed.2)Among human activity factors,planting area has the greatest impact on agricultural irrigation water demand,and followed by planting structure.3)The multiple regression model established by the path analysis method has high fitness and prediction accuracy,which is more suitable for predicting the water demand of agricultural irrigation in irrigation areas.(5)The agricultural water saving potential of the irrigation district is different in different typical hydrological years.Among them,the agricultural water saving potential of the rainy year is the largest,and the agricultural water saving potential of the dry year is the smallest.Therefore,The agricultural water strategies to cope with changing environment problems are proposed,such as improving the canal system,rationally arranging water resources,adjusting the crop planting structure,implementing water-saving irrigation technology,and strengthening the water price adjustment mechanism etc.