Study On The River Health Assessment And The Ecological Regulation Research In The Dawen River Basin

As an important natural resource,rivers have the functions of providing material production,regulating flood,providing water resources,providing habitats,maintaining ecological diversity and so on.They also play an important role in sustainable development in the natural material cycle process and social economic development.At the same time,river system is the core element of ecological environment,maintaining the ecological balance of the region.In recent years,the Dawen River Basin has successively built many cascade reserviors,which have improved the water supply capacity of farmland irrigation,domestic water and industrial water.However,researvior construction caused the problem of river ecological degradation.This paper analyzed the ecological health status of the Dawen River Basin from the aquatic organisms and hydrological processes point of view,and proposes the ecological dispatching of the Dawen River Basin,and proposed an ecological scheduling scheme in order to achieve a reasonable water allocation in the Dawen River Basin.The main research contents of this thesis are as follows:According to the four times ecological investigation in the Dawen River Basin from October 2016 to April 2018,the fish dominant species were Carassins auratus,Hemicculter Leuciclus and Channa argus,the indicator species were Cyprinus carpio,Hemicculter Leuciclus,Carassins auratus,Pelteobagrus fulvidraco,Cobitis sinensis,Hypophthalmichthys molitrix and Misgurnus anguillicaudatus.The key period of the Dawen River Basin was proposed.The ecological health in the Dawen River Basin was evaluated from the aspects of water quality and fish index of biotic integrity,the results showed that the evaluation results were good at the upper reaches of the Dawen River,the Yingwen River and the source of the south branch of the Dawen Riverand the evaluation results at the downstream of the Dawen River,the middle and lower reaches of the south branch of the Dawen River and the Hui River were poor.The results of water quality and fish index of biotic integrity were analyzed by cluster analysis,and three ecological zones were identified,which were respectively the area above the confluence of the Yingwen River and the Dawen River,the area from the confluence of Yingwen River and the Dawen River Wen River to Wenkou and Dawen Henan Branch to the Dawenkou and the south branch of the Dawen River,the area of the lower reaches of the Dawen River and the Hui River.Based on the hydrologic series data of Beiwang hydrological station,Dawenkou hydrological station and Daicunba hydrological station in the Dawen River Basin,using trend analysis,wavelet analysis and RVA(Range of Variability Appraoch)based on IHA(Indicators of Hydrological Alteration)to analyze the variation trend of annual flow,variation period and the change degree of hydrological indicators in the Dawen River Basin.The results indicated that the annual flow of the Dawen River Basin showed a decline trend.There were three abvious periodic peak,which were 5 years,11 years and 25 years scales.The maximum periodic peak appeared in 11 years.As for the Dawenkou section,the hydrological alteration of the monthly flow in June and July,annual minimum flow,base flow index,the frequency of high/low flow,the duration of high/low flow,the rising rate and the falling rate changed significantly.As for the Daicunba section,hydrological alteration of the monthly flow in July and August,annual minimum flow,base flow index,days of zero flow and the flow reversals changed significantly.The approaches of RVA,Tennant,the lowest average monthly flow and the lowest average monthly flow with 90% guaranteed rate were proposed to calculate the ecological flow.It is considered that the results obtained by Tennant can reasonably reflect the ecological flow process in Dawen River Basin.Finally,combined with the ecological period of the Dawen River Basin from April to September,the ecological flow process of the Dawen River Basin in different horizontal years at the sections of Beiwang,Dawenkou and Dacunba hydrological stations is obtained.Tennant method is used to calculate the minimum ecological flow which can maintain the basic morphology and function of river in different typical years,which provides basic data for the ecological regulation.Analyze the development and utilization of major cascade reservior in the Dawen River Basin,and quantitatively analyze the supply and demand of domestic water,industrial water and agricultural water in the regulation region.On the basis of the connotation and methods of river ecological regulation,the multi-objective ecological scheduling model of Dawen River was established.The particle swarm optimization was used to iteratively calculate the scheduling schemes of different levels and optimized the scheduling schemes.Finally,the ecological scheduling scheme of Dawen River Basin was provided.The results show that the control sections of Beiwang,Dawenkou and Daicunba can meet the demand of ecological discharge in most months of different level years,especially in most months of normal and dry years,which can provide reference for improving the ecological health in the Dawen River Basin.