Ecological Effect Analysis And High Efficiency Utilization Of Water Resource For Nandujiang River Estuary

Nandujiang River is the greatest river in Hainan Province. In recent years, with the construction of different kinds of water diversion, storage and lifting works, the natural flow conditions were artificially changed, which affect (or even destroy) the health of river ecosystem.Meanwhile, excessive sand exploration in recent years leds to lowering of riverbed, and sea water intrusion is becoming more and more serious. Nandujiang River Estuary is confronted with serious ecological and environmental problem now.Systematical research was carried out in this thesis on the ecological effect and high efficiency utilization of water resources of Nandujiang River Estuary. Main contents and innovation points are:Multiple time scale analysis and variation trend analysis are carried out for natural annual runoff with wavelet method. The low frequency component was adopted in forecasting of hydrosequence tendency. The analytical hierarchy process in theory of fuzzy mathematies was introduced into water resources analysis, herein, the utilization degree of water resources of Haikou City is evaluated. Analytical hierarchy process was adopted for evaluation of utilization degree of water resources in Haikou City.Research indicates that the water resource development and utilization degree of Nandu River Estuary is not high, and there is still a large potentiality.Based on the concept of ecology water need and minimal ecology base runoff, the ecology water requirement in and outside of river channel of Nandujiang River was computed with multiple methods.The natural flow rate of downstream of Nandu River basically meets the requirement of suitable ecology base runoff. The biologic reproduction condition and the river ecosystem is basically in good condition.As for salt water intrusion, hydrodynamic method was adopted to study the relationship between intrusion distance and flow rate of river.The salt water encroachment status of estuary under low discharge was simulated and the relationship of salt water encroachment distance vs. time was analyzed, as well as the influence of discharge variation on salt water encroachment.An evaluating indicator system was established for functions of river, including the service function, environment function, utilization function and ecology function of river. Comprehensive evaluation was carried out with analytical hierarchy process to obtain the influence of each index on river ecology health. The influence of rubber dam works on river ecology was also analyzed. Analysis shows that the project has little impact on ecological environment downstream of Longtang Dam and the water intaking scenario is feasible.The service functions of water ecosystem of Nandujiang River were summed up, based on which, an economic value evaluating indicator system was established for service of ecosystem of river. The value of increased water impoundment of Nandu River estuary was studied.Water demand forecast was carried out based on gray predictive model and modified BP neural network and the results reflect the nonlinear relationship between water demand growth and impact factors well.In addition, high efficiency utilization of water resources of Nandujiang River Estuary was studied from the aspect of engineering measures and water distribution and management.