| Urban water bodies refer to the surface water bodies within the urban built-up area and the planned area,with the main purpose of creating urban water environment and providing residents with water-friendly space for leisure and entertainment.For most urban water bodies,especially artificial water bodies,designated to landscape use.However,the existing evaluations of urban water bodies mainly focus on the water quality and eutrophication of the water bodies,but there are short of evaluation and protection of urban landscape water bodies.Therefore,this study focused on the landscape effect of urban water bodies,selected 189 urban water bodies in 26 provinces of China,and obtained first-hand data based on data collection,field investigation,field monitoring and data processing.According to theoretical analysis,data analysis and simulation calculation,the comprehensive evaluation index of urban water landscape effect established and applied to the strategic analysis of urban water landscape effect protection.The main outputs of this work are as follows:(1)Based on the field investigation of 189 urban water bodies in 26 provinces of China,the correlation between the main water environment parameters and the water landscape effect was studied.For urban water bodies with different replenishment waters,the evaluation results based on either "Surface Water Environmental Quality Standard"(GB3838-2002)or traditional trophic state index were both inconsistent with the real landscape effects of field investigation.In view of the fact that the landscape effect of a water body mostly depends on the visual properties and public acceptance of the water,introducing the results of on-site questionnaire survey,it was found that public satisfaction and water transparency(SD)were positively correlated,indicating that SD is an important factor related to urban water landscape effect.Therefore,the analysis of the influencing factors to SD can be used as a theorectical approach to establish the comprehensive index for water landscape effect.(2)Based on the correlation between SD and the water landscape effect,as well as the analysis of factors restricting SD,the water environment parameters affecting the water landscape effect was studied.According to the theoretical analysis of SD,it was found that the visual perception of water was affected by a variety of suspended matters in the water,including inorganic suspended solids,organic detritus and algae.These suspended matters thus becomes the main restricting factors of the water landscape effect.Through the analysis of the causes of the three types of suspended matters,it was found that the visual sensory properties of water were closely related to its suspended state,organic pollution state,algae reproduction state and hydraulic state,and the independent water environment parameters that directly affect the above state,namely suspended solid(SS),dissolved oxygen(DO),chemical oxygen demand(COD),ammonium(NH4+-N),nitrogen(NO3--N),total phosphorous(TP),hydraulic retention time(HRT)and water temperature(T).Therefore,these 8 parameters can be used as the associated water environment variables of the water landscape effect.(3)A comprehensive index for water landscape effect assessing of urban water bodies was established.Firstly,through the comparison of the commonly used comprehensive index forms,the multiplicative method was selected,and the comprehensive evaluation index for urban water landscape effect with 8 related water environment factors was established,that is,WLEI=∏i=18qiwi Then,the quality of each factor(qi)was determined through the dimensionless and cumulative frequency distribution function of the 8 related water environment factors using the fist-hand data from field investigation.Furthermore,considering different replenishment situations,the weight coefficient(wi)of each factor is established through the sensitivity analysis of 8 related water environment factors.The relationship between the calculated WLEI and the measured SD based on the data of field investigation of urban water bodies of the inveatigated urban water bodies was good(R2=0.8948,p<0.05).Consequently,taking SD as the reperence condition of public acceptance,a grading and quantitative evaluation method for landscape effect assessing of urban water bodies were proposed.(4)With the consideration of tha actual demands of reclaimed water for landscape water replenishment in water-deficient cities,using the comprehensive evaluation indexd for urban landscape effect,cases comparison of reclaimed water replenishing and natural water replenishing was carried out,and the basic strategy for improving urban water landscape effect was studied.The results showed that despite the concentration of dissolved organic matter and nutrients in the reclaimed water are generally higher than that of natural water,it has the advantage of low SS concentration.Among the 8 relevant water environmental factors,the contribution rate of the hydraulic retention time(HRT)to WLEI is the largest,and the second is the organic matter concentration(CODMn)of reclaimed water.Therefore,providing adequate replenishment water amount of reclaimed water and strengthening the removal of organic matter in reclaimed water treatment are the main strategies for ensuring the water landscape effect of urban water bodies replenished with natural water.In contrast,when natural water is used as the replenishment water source,the SS concentration contributes the most to WLEI,followed by HRT and TP.Therefore,appropriate pretreatment(such as coagulation and filtration)reduces the SS and TP concentration of the replenishment water,as well as ample replenishment water supply are the main strategy for ensuring the water landscape effect of urban water bodies replenished with reclaimed water. |
