Water Resources Management And Decision-making Model Research For Irrigation District In Shiyang River Basin

Shiyang River Basin is a typical arid district in the northwest of China, with a high degree of water resources development and a prominent problem of water resources management. Therefore, research hydrologic cycle and water resources transformation process in Shiyang River Basin are significant for the reasonable utilization and optimal allocation of restricted water resources in arid region. Meanwhile, water resources system is full of complex uncertainties. Factors and parameters of water resources system optimization process could be affected by various uncertain elements such as climate, water resources quantity, agricultural production capacity and management level. Taking Wuwei basin as an example, which is located in the midstream of Shiyang River basin, this study carries out research on water resources transformation mechanism and simulation and optimization models under uncertainties based on the analysis of the uncertain parameters and variables. Models during water resources simulation and optimization process were established including deficit irrigation management, crop area configuration, surface water and groundwater transformation, real-time operation of reservoir, irrigation area optimization and water resource allocation. The main research contents and results are as follows:(1) An interval-parameter fuzzy linear optimization model (IPFLP) for crop area allocation management was developed and applied to both river-irrigated area and well-irrigated area of Shiyang River Basin. The model focused on deficit irrigation area allocation ratios and deficit irrigation management of the three irrigation districts under limited water resources supplies. Because of the spatial and temporal variations in stream, flows, system costs, and related benefits, agricultural irrigation systems are often filled with uncertainties. Interval-parameters programming and fuzzy programming were introduced to the determined optimal model. Three decision scenarios associated with different inflow policies were examined in this study. Different fuzzy set levels were introduced to reflect the fuzzy uncertainties for the decision makers with different subjective judgments and varied system benefits. The results were more significant than that of the traditional determined method. It could be used to provide decision support for local irrigation management.(2) An uncertain monthly reservoirs operation and multi-crop deficit irrigation model based on the conjunctive use of groundwater and surface water was proposed in this study. The objective was to maximize the total crop yield of the entire irrigation districts. Meanwhile, ecological water was remained for the downstream demand. Due to the shortage of water resources, the monthly crop water production function was adopted for multi-period deficit irrigation management. The model reflected the characteristics of water resources repetitive transformation in typical inland rivers irrigation system. The model was applied in water resources optimization management in Shiyang River Basin, China. Uncertainties in reservoir management shown as fuzzy probability were treated through chance-constrained parameter for decision makers. Necessity of Dominance (ND) was used to examine the advantages of the method. The optimization results including reservoirs real-time operation policy, deficit irrigation management and the available water resource allocation could be used to provide decision support for local irrigation management. Furthermore, the obtained strategies could help with the risk analysis of reservoirs operation stochastically.(3) A water resource transformation simulation model was developed to the study area. The surface water and ground water calculation Molden Sakthivadivel model based on water balance was applied to calculate water balance relations in the process of regional water resources transformation. The Thornthwaite-Mather model was adopted to eliminate the change process of water content of the surface soil area under different water resources allocation situations, Evapotranspiration of surface area and groundwater recharge were computed as well. This research addressed the relationship between water consumption and water storage of each part in the region, and studied water resources utilization and transformation in the case of surface water and groundwater conjunctive use. Moreover, water resources allocation strategies under various scenarios were analyzed.(4) A regional water resources optimization model based on Molden Sakthivadivel model and Thornthwaite-Mather model was developed to provide optimal management for irrigation area and monthly irrigation water. Considering the demand of decreasing irrigation area and the planed downstream flow in Shiyang River Basin Comprehensive Restoration Plan, the described model could provide reasonable optimization allocation decisions conforming to the limited water resources condition. Accordingly, valuable guidance was proposed for the study area to manage irrigation area and water allocation efficiently.