Study On Mechanism And Practice Of Improving Water Quality By Water Resources Diversion In Plain River-net Areas

Disaster of flood and waterlog, shortage of water resource and deterioration of water environment have become three major problems related to water. Water resources diversion is no doubt a very important measure to resolve these three major issues. The method is a redistribution of water resource in terms of time and space by means of water projects in order to meet requirement of safety of flood control, safeguard of water supply and improvement of ecology system for society. Water resources diversion for improving water quality is attributed to environmental diversion, which is called the clean water diversion in plain river-net areas like Shanghai Municipality.The definition of the clean water diversion here is a water resource reallocation method adopted to improve river water quality in the water project controlled region by means of maximum use of outer river tidal dynamics and freshwater resources through functions of engineering arrangements including gates and pumps to facilitate an oriented and orderly movement of the water body of main rivers in river-net and speed up the water body exchange on the prequisite that flood control, industrial and domestic water use, shipping and water environment of critical areas are guaranteed. Its main purpose is to develop the comprehensive functions and benefits of water engineering facilities featured by benefits realization and risk aversion through changes of the operation of existing or proposed future water facilities so that present water resource can be adequately used, river quality can be improved, and water ecology, environment and scenery can be restored, improved and protected and in turn to ensure a sustainable economic development supported by a sustainable water resource development. It is not only an important measure to enhance the existing river-net water environment capacity, but also a world current of BPEO case with Chinese touch and therefore meet the need for double targets achieving both social and economic development and environment improvement at present situation in China.This article has made a comprehensive and systematic analysis and research on the mechanism of water quality improvement by means of the clean water diversion in plain river-net areas from different branches of learning of hydrology, geology, water engineering, environmental science,chemical analysis and applied mathematics. Emphasis has been put on the calculating method of water introduction and discharging capacity in catchments, study of water function district definition, appraisal of mechanism of black and malodorous phenomenon, study of water- net environmental capacity for pollutants, and theory and methodology for water quality modeling and simulation applicable to water diversion. Therefore, a theoretical framework of water resource diversion has been primitively set up. Meanwhile, based on the water resources census data, water diversion prototype observation, historical data search and collection, expert panel discussions together with methods of hydrological, dilution mechanism and self-cleansing analysis and mathematical modeling, a comprehensive assessment of the function of the clean water diversion in Shanghai under existing engineering situation has been made. Discussion has been made on the problems arising from it and optimization of the existing diversion proposals and engineering measures.This article has covered the following six major research contents.Part I presents a thorough study of basic conditions of the clean water diversion in plain river-net areas mainly from perspectives of geological, economic and technical analysis. Five fundamental elements for the clean water diversion is formulated as follows: the basic element for the clean water diversion is a river-net in plain formed by long time natural evolution and human forces; The set-up of 14 water engineering controlled regions and their neighboring controlled water gates projects provides conditions for the clean water diversion; Heavy pollution in river-net develops t...