Calculation And Evaluation Of Soil Water Resoures Carrying Capacity Of Cultivated Land In Hebei Province

Hebei Province is one of the provinces which are extreme shortage of water resources in China, and the shortage of water resources is about 5~6 billion cubic meters under the present condition. Running of the South-to-North Water Diversion Project can relieve the shortage of the water resources, but cannot completely solve the shortage of water resources in Hebei Province. On the other hand, there have rich soil water resources. According to the results of soil water resources evaluation, the average annual available soil water resources were 23.1 billion cubic meters, in addition, the irrigation water were about 17 billion cubic meters, so there will be 40.1 billion cubic meters available soil water resources in whole province. And then, under the condition of the serious shortage of water resources and the irrigation water resources, reasonable development and utilization of soil water resources has great importance to ensure food security, to improve the farmers’ living standard, to maintain the sustainable utilization of water resources, to maintain a good ecological environment and to keep the agricultural sustainable development in Hebei Province. In this paper, the conception and connotation of soil water resources carrying capacity of cultivated land will be defined, and the soil water resources carrying capacity of cultivated land which are in Hebei Province, in each soil water resources division and in each city will be evaluated. The main research results are as follows:(1) The theory of resources carrying capacity is introducted to the research of soil water resources, and the concept of soil water resources carrying capacity has been defined in the paper. The conception is When soil water, fertilizer, gas and heat in soil maintain harmony, under the natural unified model condition, in which the source of soil water is natural precipitation, such as dry land and dry rice fields, or under the natural-manpower duality mode condition, in which the sources of soil water are natural precipitation and irrigation, such as irrigated land and paddy fields, and under the condition of the economy development level and the technology development level in a certain social development stage, the ability of soil water can continuously support on the development of agriculture. The main carrying object of soil water carrying capacity of cultivated land has been confirmed, it is agricultural planting; the connotations of soil water carrying capacity of cultivated land, including the carrying mode, space-time variety, the utilization form, socioeconomic and sustainable connotations have been analyzed; basing on the similarities and differences between the carrying capacity of water resources and the soil water resources carrying capacity, the characteristics of the soil water resources carrying capacity of cultivated land, including the sustainability, the finiteness, the variability, the regulating, dependence of precipitation, and simple carrying object, have been discussed.(2) According to the connotation and conception of the soil water resources carrying capacity of cultivated land, the multi-objective optimization models are established. In the model, the maximum agricultural output, the maximum total grain yield, and the minimum ratio of agricultural water consumption are taken as the goals, the crop structure, the valume of water resources, the valume of soil water resources and etc. are taken as the constraint condition in the model, then these single-objective model will be a comprehensive objective model by weighted method, and the comprehensive model are optimized by linear programming.(3) According to the characteristics and the influencing factors of the soil water resources carrying capacity of cultivated land, referencing the water carrying capacity evaluation index system, the evaluation index system of the soil water resources carrying capacity has been established, and then the threshold and the weight of each index have been calculated. The index system includes four primary-indexes, water supply, water utilization, management and benefit, and 17 secondary indexes. The threshold of the index can be predicted or determined by investigating the national, provincial, municipal relevant policies, regulations and planning, by collecting the relevant state criterion or occupational standard, by referencing the development level of developed countries and domestic developed regions, by using the regressive equation which is analyzed by the statistics yearbook data to predict the index threshold, and by the methods of expert experience. In order to describe the state of the soil water resources carrying capacity, the carrying capacity has be divided into primary, secondary, and three-level based on the level of agricultural saving-water technology development, and the corresponding interval of each grade have been calculated, providing the standard of quantitative evaluation of soil water resources carrying capacity. Combined with the questionnaire survey results, the weight of each evaluation index has been determined by subjectivity and objectivity.(4) The soil water resources carrying capacity calculation model is used to calculate the carrying capacity of soil water in cultivated land of whole province, seven soil water divisions, and eleven cities. Two plan level and two rain frequency have been considered in this paper, and 12 cases have been established, and in the evaluation of the whole prince, three levels of water-saving technology are considered. Then, fuzzy variable assessment method is utilized to evaluate each case and to determine the grade of the soil water resources carrying capacity in each case. In 2020,all carrying capacity cases can be evaluated as secondary, and be described “Plan is general, and can adapt to the local regional economic development". In 2030, when rain frequency is 50%, all cases can be evaluated primary, and be described “Plan is good, and more suitable for the local regional economic development”, and when rain frequency is 75%, all cases can be evaluated secondary, and are better than 2020. Under the background of agricultural sustainable development, through analyzing the basic and conditions in 2020 and in 2030, the developing plans in 2020 and in 2030 of Hebei Province are determined.(5) Using the soil water resources carrying capacity calculation model to calculate the carrying capacity of 7 soil water divisions and 11 cities in Hebei Province. Two plan level and two rain frequency have been considered in this paper, and the agricultural output, total grain yield, the utilization of soil water resources and water resources, the irrigation area, and the developing area of all kinds of soil water resources utilization technology of each soil water division and each city will be calculated and analyzed in the paper.(6) The value of soil water resources, of the availability and of the potential availability soil water in each county in Hebei Province are calculated, based on the research results, experience and cropping pattern, the advanced technology and measures are analyzed and summarized. The countermeasures and measures of enhancing the carrying capacity of soil water in cultivated land will be given in the paper including engineering measures, management measure and biological measures.