Simulation of water resource carrying capacity based on LMDI-SD model in green development irrigation areas

Aiming at the problems of river dry-up, deterioration of the eco-environment and inefficient use of water resources caused by water diversion in the irrigation area, water resources carrying capacity under the green development model was simulated. Taking the Baojixia irrigation area as the research area, based on divisia exponential decomposition, Kaya equation and system dynamics theory, a coupled model with Logarithmic Mean Divisia Index (LMDI) and System Dynamics (SD) was proposed. LMDI model, based on water demand mechanism, was developed to decompose and identify the main driving factors for changes of the water consumption, including irrigation water consumption, industrial water consumption and domestic water consumption in the irrigation area. System dynamics model was employed to simulate the water requirement via inputting the key driving factors from the LMDI model. Five simulation schemes were set up using scheme analysis method, including ecological water demand, high-efficiency water saving, industrial structure adjustment and external water diversion. The proposed models were used to simulate the water demand of the irrigation area dynamically in the future, from 2017 to 2030. The levels of water resources carrying capacity were discussed by employing water resources carrying index in the planning year 2025 and 2030. The results showed that the quotas of water consumption played the major driving roles in the change of water consumption in different departments of irrigation area by analyzing historical data. According to the simulation results of the scheme 1 (current development model), the differences between supply and demand water were positive, and the carrying indexes of water resources were less than 1, which means the water resources could carry the development of the irrigation area in 2025. In 2030, the carrying indexes were greater than 1, which indicated that water resources were overloaded. Under the scheme 2 (environment-friendly model), the scheme 3 (environment-friendly and water-saving model) and the scheme 4 (environment-friendly, water-saving and industrial structure adjustment model ), P=75% in 2030, the differences between supply and demand water were negative, and the carrying indexes were greater than 1, indicating that the water resources cannot supply the social and economic development. But for the scheme 5 (green development model), the differences between supply and demand water were positive, and the carrying indexes of water resource were less than 1 through regulating the main driving factors of the water consumption in 2025 and 2030, which implied that the water resources can carry the development of the irrigation area. It was also shown that reasonable measures can alleviate effectively the contradiction between water supply and demand in irrigation areas and improve the water carrying capacity. The purpose of this study is to provide a scientific decision-making method for the rational utilization of water resources under the green development model in the arid and semi-arid irrigation areas.