Study On Ecologica Environmental Water Demand Of Typical Lake In Ningxia

Shahu Lake is the largest natural brackish lake in Ningxia.It is located in the arid and semi-arid area of northwest China.The climate is dry,the evaporation is large,and the water resources are short.In addition,with the rapid development of tourism and surrounding industries and agriculture,the sand lake body The water quality has deteriorated year by year,and the eutrophication trend is obvious,and it is urgently needed to be treated.Carrying out research on the ecological water demand of Shahu Lake can provide a basis for Shahu to solve water environment problems.Based on the existing research results,this paper takes Shahu as an example to carry out in-depth research on the water demand of lake ecological environment.The research results and main conclusions obtained are as follows:(1)According to the data of Shahu monitoring from 2015 to 2017,the single-factor evaluation method is used to discriminate the water quality category of Shahu Lake,determine the compliance rate of each water quality index,and determine the main over-standard factors of Shahu Lake.Comprehensive nutrient status index method was used to evaluate the nutrient status of Shahu Lake.The pollution factor of the main over-standard in Shahu Lake from 2015 to 2016 was TP,followed by TN,CODCr and CODMn.In 2017,the main pollution factor of Shahu Lake water was TN,followed by CODcr,TP and CODMn.From 2015 to 2017,the eutrophication of Shahu Lake is mildly eutrophic in spring and winter,and moderately eutrophic in summer and autumn.(2)Referring to the current scholars' different definitions of lake ecological environment water demand,combined with regional characteristics,the concept and connotation of "lake ecological environment water demand" in arid regions are further studied.The concept of lake ecological environment water demand in arid and semi-arid areas is defined as:Under the premise of ensuring that the lake's ecological functions and ecological environment objectives are not destroyed,the lake's ecological environment will no longer deteriorate and gradually obtain the amount of water needed for restoration.(3)From the perspective of water quantity and water quality,on the basis of satisfying the ecological environment function of Shahu Lake,the water quantity-water quality coupling model of Shahu Lake was constructed.Respectively calculated the water quality of Shahu Lake water quality no longer deteriorated,reaching the surface water quality stand amount of water required for the Class ? and Class ? water.The calculation shows that when the water quality of Shahu Lake is still no longer deteriorating,the optimal water diversion for the whole year is 27.32 X 106m3.When the water quality of Shahu Lake meets the requirements of Class IV water and Class ? water specified in the surface water quality standard,the optimal water intake was 25.67 × 106m3 and 52.74 × 106m3,respectively.(4)The function method is used to calculate the water demand of the ecological environment of Shahu Lake.The water demand of the ecological environment of Shahu Lake is composited by basic water demand of Shahu Lake,the water demand improvement of Shahu Lake water environment and the vegetation and landscape water demand of Shahu Lake.Respectively calculated the minimum,suitable and maximum ecological environment water requirement of Shahu Lake.The calculation results of the ecological environment water demand of Shahu Lake show that the minimum ecological environment water requirement of Shahu Lake is 14.02×106m3,the suitable ecological environment water demand of Shahu Lake is 32.43 ×106m3,and the maximum ecological environment water requirement of Shahu Lake is 63.41 ×106m3.