Study On Water Functional Transition Zone And Water Environmental Carrying Capacity For Tidal River Network

As part of the Shanghai science and technology commission supported project "study on the Shanghai water environment functional zoning" and "Study on the water quality improvement of the Suzhou Creek rehabilitation Phase II project", and also the Shanghai Water Authority supported project "Study on the carrying capacity of the Shanghai tidal river networks", this study focuses on solving the key technical problems existing in water environment functional zoning and the water resource development, utilization, protection and management. A systematic research approach has been conducted in the study and the following achievements are achieved.This study shows that longitudinal dispersion coefficient has close relation to the predicted water quality. With intensive reference to the relevant studies, This project suggested a rational range of longitudinal dispersion coefficient value, and also the method to adjust the empirical coefficient in computing the longitudinal dispersion coefficient.Basing on the new ideas of water environment functional transition zone and the theory of water environment carrying capacity assessment, this study, for the first time, formulated the formula to compute the concentration distribution and the length of the transition zone under steady and unsteady hydrodynamic conditions. The method of computing the length of the transition zone under steady and unsteady hydrodynamic conditions is proposed for the first time, and the impact of hydrodynamic, contaminant characteristic, type of transition zone and the internal pollution source from sediment on the length of the transition zone is studied in detail for the first time.With consideration of the complex river networks and the related complex hydrodynamics, for the first time, a mathematical model to assess the assimilative capacity was setup for the Shanghai tidal river networks. The model can either simulate the length and the concentration distribution of pollutants in the transitionzone, or to assess the assimilative capacity and its space-time change with water quality boundary conditions, water quality objectives, storage of water and the operation of control structures.Basing on the Shanghai digital river network with unified geo-coordinate system, this study integrates hydrodynamic model, water quality model, assimilative capacity assessment model and GIS into one platform. The combined effects of water quality change due to storage branch and the river network schematization has been taken in account in the model. The integrated system can support auto-coding and the identification of networks. A GIS based hydrodynamic, water quality and water environmental carrying capacity assessment model has been setup for the Suzhou Creek river system.Some creative achievements has been achieved in the study of improving tidal river networks hydrodynamic and water quality model, development of water environmental carrying capacity assessment model, and the impacts on the length of transition zone and assimilative capacity. The main results has been published on the El journals oThis study provides key technical tools and scientific basis to water environment functional zoning, environmental engineering feasibility study, and is also critical in balancing water quality, assimilative capacity and the total maximum discharging load.