Study On Optimal Allocation Of Water Resources And Ecological Restoration In The Ecological Fragile Area Of Northwest China

The climate change and global warming leads to the early melting of glaciers,which further exacerbates the uneven distribution of precipitation in time and space.What's more,the rapid population growth,economic development and accelerated urbanization,have caused great damage to the natural ecological environment.Especially the northwestern part of China,most of which are in arid and semi-arid regions,coupled with extreme shortage of water resources,unreasonable development and utilization,and the excessive development and utilization of water resources in the upper and middle reaches,have further exacerbated the environmental degradation.Northwestern part of China has become the region with the most significant vulnerability in China.The protection and restoration of the northwestern ecologically fragile areas is one of the important themes of the Western Development Strategy.The environmental condition in this region not only affects the sustainable d'evelopment of northwestern regions,but also the whole China.Due to the uneven characteristic of rainfall,the mismatched of water and soil resources,as well as the large proportion of agricultural water which squeezing ecological water requirement,the effect of water resources utilization on social economy development and ecological environmental quality cannot be neglected.Therefore,Water resources management is the key of environment protection in ecological fragility region in the northwestern districts.Global warming has led to enhanced evapotranspiration in the oceans and land,accelerated air-water cycles,and increased spatial and temporal changes in precipitation distribution,leading to increased uncertainty in the amount of available water resources.Coupled with the complexity of the ecosystem itself and the subjectivity and blindness of human activities,made it more difficult to restore the ecology of the northwest region.In this paper,on the basis of fully identifying the uncertainty and complexity of the system,proposed the coordination of"water-land-grain",taking economy,society and environment into consideration.Then selects the three river source areas and Shule River Basin as the research object,and established series models of grassland ecosystem restoration,water resources optimization and agricultural planting structure optimization,including:(1)A CvaR based interval two-stage stochastic programming is developed for ecological protection and restoration to reflect stochastic information existing in grass yeild.Overload area and control area would be optimized to obtain high system benefit and effective ecological management plan.Taking the conditional value at risk as risk management index to represent the attitude of decision makers,the results can help balance the tradeoff between system benefit and system risk,as well as coordinate the relationship between economic development and ecological protection.(2)An interval minimax relative-regret analysis model for water resources management is formulated.Results can help solve the rival rousness of water among different districts and different sectorsThe environmental water demand is considered to promote the public awareness on environment protection and ecological conservation.(3)Through introducing crop water footprint theory into the crop planting structure optimization process,the disparities and features for water footprint of different crops in different districts can be reflected,with consideration of entity water and virtual water.The results can help improve the agricultural water resources management status with minimized water consumption and maximized system benefit and thus improve the water utilization co-efficiency.(4)A chance-constraint based fractional programming method is proposed for crop planting structure optimization in Yumen district.A crop planting structure model is established to reflect random uncertainty existing in right hand side of the constraints.Crop-planting structure,total crop area,water allocation scheme,crop yeild and system benefit can be obtained.Results indicate that when food demands are satisfied,more economic crops can be planted to support local economic development.The series of model proposed in this paper can be effectively applied to water resources management and ecological environment protection in northwest ecologically fragile areas,and can also be used for reference in other arid and semiarid areas.The research results can provide a basis for further management work from the perspective of the "land-water-grain" relationship.