Simulation And Prediction Of Water Quality Of Jingjiang River Using WASP Model

Objective: 1.Using WASP model for simulating and predicting temporal-spatial variation rules about water quality of Jingjiang River; 2.Analyzing and verifying whether the WASP model could be used in large river; 3.Providing scientific basis to protect the water quality safety and make water quality management plan about Jingjiang River with forecast data of water quality variation from WASP model.Method: Using the WASP model recommended by the U.S. environmental protection agency(EPA), first of all, Jingjiang River trunk channel was conceptualized and divided into nine sections from Zhi Jiang to Xiong jiazhou about 247 kilometers according to hydrology, pollution, etc. On this basis,using EUTRO module and TOXI module of WASP, with 2014 hydrological year(including the dry seasons of 2013/2014 to the wet seasons of 2014) of dissolved oxygen, chlorophyll a and total suspended solids, lead, chromium and arsenic monitoring data as input variables, acquiring Jingjiang River pollution load emissions data and flow data of hydrologic station in Jingjiang River by collecting from the environmental protection department official website of Yi chang city and Jing zhou city and the official website of the bureau of hydrology and water resources in Hubei province,using test algorithm to calibrate the important parameters of the above-mentioned water quality indicators,validating the accuracy and reliability of the model by analyzing the relative error size between the simulated values and measured values of Various water quality indicators(Dissolved oxygen,Chlorophyll a,total suspended solids)according to the measured data from 2015 and 2016 hydrologic years, heavy metals(lead,chromium,arsenic)using measured data from 2015 hydrological year to validate,making a parameter sensitivity analysis to evaluate each model respectively.adopted measured data above as the benchmark data and used the parameter after calibration, simulated and predicted the variation of concentration in time and space in the hydrological years of 2014-2016 and 2016-2018 for each water quality index respectively in the end.Results:(1)The sensitive parameters of dissolved oxygen are Global Reaeration Rate Constant @ 20 ?, BOD Decay Rate Constant @20?, temperature and flow. Temperature, flow, Phytoplankton Endogenous Respiration Rate Constant @20?, Phytoplankton Respiration Temperature Coefficient and Phytoplankton Death Rate Constant are sensitive parameters of Chlorophyll a. The sensitivity analysis total suspended solids showed of these parameters of this model was not sensitive for total suspended solids.The sensitive parameters of metal lead, chromium, arsenic are flow, sedimentation rate and resuspension rate.(2)Displayed by model validation,, the relative error rate between measured density and simulate density were far lower than the 40% during the hydrological years of 2015-2016 about dissolved oxygen and total suspended solids related of eutrophication.The relative error rate of chlorophyll a within 40% accounted for 77.78%;In terms of metal indicators,the relative error of between simulated values and measured values are less than 40% during the hydrological year of 2015.(3)On the basis of Conceptualization and subsection, using the WASP model gained the Concentration range of forecast data about dissolved oxygen, chlorophyll a,total suspended solids,arsenic,lead and chromium during the hydrological year of 2015-2017 in Jingjiang River:dissolved oxygen between 6-9 mg/L, chlorophyll a between 6×10-4to 9×10-4mg/L total suspended solids in the change between 0 to 20 mg/L;the concentration of arsenic between in1.95×10-3to 2.00×10-3mg/L, the concentration of chromium5×10-5to 32×10-5mg/L, lead concentrations in 2×10-6to 12×10-6mg/L.Conclusions:.(1)On the basis of conceptualization and subsection for large rivers,the goodness of fit was high between prediction results and measured results of dissolved oxygen, chlorophyll a and total suspended solids, lead, chromium and arsenic,and simulating and predicting the temporal-spatial variation situation of concentration of some water quality indexes in Jingjiang River was good.(2)The concentration of Arsenic, lead, chromium and dissolved oxygen can meet the requirement of ?type of water from standard GB3838-2002 respectively in this study during the hydrological year of 2015-2017.