Approach On Ecological Safety Evaluation Of Large Scale Water-saving Irrigation

China's water resources are unevenly distributed in time and space,insufficient in quantity,and the shortage is serious.The development of water-saving irrigation has become an important way and an inevitable choice to alleviate the contradiction between water supply and demand.However,the cyclical attributes and system characteristics of water resources determine that water-saving irrigation will inevitably lead to changes in the accompanying processes and the safety of associated systems.The ecological effects and ecological security of large-scale water-saving irrigation have received increasing attention from all walks of life.This paper was aimed at this problem,taking the arid inland river basin in Northwest China as an example to carry out the evaluation method and application research of ecological safety of large-scale water-saving irrigation.Firstly,this paper systematically sorted out the system of water-saving irrigation engineering technology,and analyzed its characteristics and development trend.Based on a comprehensive analysis of the ecological environment vulnerability,economic development level,climate geography,irrigation development trend and labor cost in Northwest China,the evaluation index system of comprehensive performance of watersaving irrigation technology in arid and semi-arid regions of Northwest China was proposed.The comprehensive performances of three typical water-saving irrigation techniques(drip irrigation,sprinkler irrigation and small-scale border irrigation)were evaluated by using Analytic Hierarchy Process and Fuzzy Comprehensive Evaluation,and the evaluation results of the three were excellent,general and general.Secondly,the paper analyzed the water cycle processes,associated processes and ecological impacts of large-scale water-saving irrigation,and proposed the definition,risk mechanism and evaluation method of ecological safety of large-scale water-saving irrigation.Based on the Vensim model structure,a simulation model including irrigation,soil,surface water,groundwater and biology subsystems for quantitative evaluation of ecological safety of large-scale water-saving irrigation in irrigation district was established.The ecological safety impact analyses of large-scale water-saving irrigation in irrigation district under different river channel leakage rates,initial groundwater levels,initial soil salt contents and water-saving irrigation technology combination models were carried out.Finally,taking Changma Irrigation District in the Shule River Basin of Hexi Corridor as an example,the ecological safety evaluation model system was formed based on the irrigation system model constructed by Vensim model and the groundwater model developed by GMS model.The ecological safety of large-scale water-saving irrigation scenarios composed by different water source conditions,water distribution technologies and field water-saving technology in irrigation district was quantitatively analyzed.The proposed definition,safety classification,risk mechanism,evaluation method and systematic simulation model of ecological safety of large-scale water-saving irrigation,and the response of the ecological safety of irrigation district to different river channel leakage rates,initial groundwater levels,initial soil salt contents and watersaving irrigation technology combination patterns,will enrich the theory of ecological safety of large-scale water-saving irrigation,and have positive significance for guiding the sustainable development of water-saving irrigation and ecological environment protection in the Shule River Basin and other similar arid inland river areas.