The Effects Of Anthropogenic Pollutions On Water Quality Of Huangbaihe River Basin,China

Huangbaihe River basin(HRB)is first grade drinking water source protection zone of Yichang city,China and the water quality management target is to meet Class II standard.The river has built four cascaded reservoirs Xuanmiaoguan,Tianfumiao,Xibeikou,and Shangjiahe located upstream,middle stream,and downstream section of the river.With total reservoirs storage capacity of 332 million cubic meters,the total economic output in the water supply area of the HRB accounts for nearly 80% of Yichang City.As in all major rivers in China and worldwide,the HRB has been seriously affected by serious pollution of human intervention.The main anthropogenic sources of pollution and the largest contributors of the river water pollution are: Mining pollution,agriculture none point source,and domestic garbage.Recently,mostly due to the long-term mining effects and agricultural non-point source,eutrophication has been frequently occurred in reservoirs and along the river,causing problems of drinking water crisis in Yichang City.Based on a three year(2014-2016)water quality monitoring data and a combined application of three multifactor methods: Multivariate Analysis,Water Quality Index Analysis and Water Quality Modeling,the main objective of this Ph D research was to understand the widespread destruction and aggravated effects of large scale anthropogenic activities on the water quality of HRB,and to assess and evaluate the effects on different spatial and temporal scales.Using multivariate analysis this study identified that there are two anthropogenic sources pollution groups in the river basin.Total Phosphorus dominated pollution(TP-pollution)and Total Nitrogen dominated pollution(TN-pollution).Upstream watersheds,Xuanmiaoguan and Tianfumiao,are highly polluted with TP-pollution and that the effects are worse in the tributary streams than in the main river and reservoirs.On the other hand,downstream watersheds,Xibeikou and Shangjiahe,are highly polluted with TN-pollution,and that effects are worsen in the main river and reservoirs than in the tributary streams.These findings demonstrated the need to reduce the effects of anthropogenic pollution in upstream tributaries of the HRB.Using water quality index analysis the study investigated that water quality standard of HRB varied between Class V(seriously polluted)and Class II(slightly polluted).The upstream reservoir watersheds,Xuanmiaoguan and Tianfumiao,are only meet the Class IV standard and the Xibeikou and Shangjiahe reservoir watershed are within Class II-Class III implies the Xuanmiaoguan and Tianfumiao water sources required treatment before use for human consumption.The most impaired pollutants affected water quality standards are TP and TN.Therefore more effective management measures must be taken to protect the effect of TP and TN on the drinking water source protection zones of HRB.Using the Soil and Water Assessment Tool(SWAT)model this study investigated that upstream reservoir watersheds,Xuanmiaoguan and Tianfumiao,received higher nutrient load especially TP than the downstream reservoirs.This result has important implications for eutrophication control and to identify the location and the sources of pollution.Therefore rapid eutrophication by reducing external nutrients especially TP loading into reservoir water bodies may be one of the clearest measures for water quality management in HRB.Calibration and validation of the nutrients models has been a difficult task in a cascaded reservoir watershed due to water quality dynamic and nonlinear responses that characterize flow and nutrients transport.Water quality of reservoirs is controlled by internal hydrodynamic factors and external or watershed characteristics.As innovative achievement,this study reported the modeling techniques on how to conceptualize and model water and nutrients transport through four cascade reservoir water bodies.The application of a multisite(split-location)calibration and validation was a creative approach for nonlinear response hydrologically and hydro-chemically connected reservoir water system and it is applicable to HRB.Finally,anthropogenic pollution in HRB has shown concurrent effects on the water quality.Hence,single method application might not have adequately addressed the collective impacts of pollutants on the water quality.Therefore,the methodology applied in this research,the multifactor water quality assessment and modeling technique is found to be the best approach to distinguish between pollutants of variable characteristics and is applicable to Huangbaihe River water quality study.To this end,the methodology may be applicable for water quality studies in other similar watershed.