Study On The Water Ecologocal Carrying Capacity Of Shahu Lake In Ningxia

Due to the disturbance of human activities,the structure and function of the ecosystem have been destroyed.It’s had been affected the further development of the social economy.The study of water ecological carrying capacity(WECC)in the arid regions of Northwest China has important scientific and practical significance.This thesis studies the spatial and temporal distribution of water environment factors and aquatic biodiversity in Shahu Lake,then finds out the eutrophication assessment and water pollution degree.Then constructs an index system for evaluation of WECC.Application of factor analysis to screen candidate indicators and construct an evaluation index system for WECC.Analytic hierarchy process(AHP)are determined the weight of each indictor,calculate the WECC index.The main results are organized as the following:(1)The spatial and temporal distribution characteristics of water environment factors in Shahu Lake showed obvious seasonal variation.Transparency(SD)reaches a minimum in summer and reaches a maximum in winter;Permanganate index(CODMn)reaches a maximum in summer and reaches a minimum in winter;Dissolved oxygen(DO),chemical oxygen demand(CODcr),ammonia nitrogen(NH3-N),total phosphorus(TP),and chlorophyll-a(Chl.a)content basically reached the maximum in summer and relatively low in spring and winter;The total nitrogen(TN)and the five-day biochemical oxygen demand(BOD5)reached the maximum in the autumn,and the content in the spring and winter was relatively low;Seasonal changes in pH are not obvious.Shahu Lake is in a mild to moderate eutrophication state.(2)The density and biomass of phytoplankton and aquatic plant benthic animals reached their maximum in summer;the density of zooplankton reached its maximum in auumn,and the biomass reached its maximum in summer.The density and biomass of benthic animals reach their maximum in autumn;The density and biomass of phytoplankton,aquatic plants and zooplankton are above the average value at the Ⅴ sampling point.The density and biomass of phytoplankton,aquatic plants and zooplankton at the Ⅱ and IV sampling points are below the average value.The Shahu water body is moderately polluted,and the water quality in the summer and autumn is less polluted.(3)Factor analysis was used to screen DO,CODMn,CODcr,NH3-N,TP,Chl.a,phytoplankton density,aquatic plant density,and aquatic plant density from water environmental factors and aquatic biodiversity indices.The 13 indicators is constituted as the system of the Shahu Lake WECC.AHP is used to determine the weight,and the evaluation value of WECC of Shahu from 2015 to 2017 is calculated.The summer WECC belongs to higher bearing capacity,and the winter WECC is unbearable,Autumn and winter are weakly loadable.The ecological carrying index of Shahu Lake was 0.35、0.33、0.31 from 2015 to 2017,showing a downward trend year by year.The ecological carrying capacity of Shahu Lake was weakened from basic to bearable.