Study On Water Ecological Function Zoning In Ganqing Section Of Yellow River Basin

Water ecological function zoning is the basis of water environment zoning and classification management.Years of practical experience of water environment protection and management in countries all over the world have shown that water pollution and water ecosystem damage are prominent manifestations of basin ecological problems,which are rooted in the changes of the terrestrial ecosystem in the upper reaches of rivers and surrounding areas,leading to the decline of water environment quality and ecosystem degradation.Water ecological function zoning is designed to form a zoning scheme integrating the features of water body and land within the basin.It is based on the internal relationship between the characteristics of land ecosystem and water ecosystem.On the one hand,the results of zoning reflect the distribution pattern and ecological service characteristics of water ecosystem.On the other hand,it also reflects the support and spatial differentiation of terrestrial ecosystem for aquatic ecosystem.The application of existing studies on water ecological function zoning in Gansu section of the Yellow River Basin is not mature,and the ecological environment in this region is complex and diverse,so the construction of regional index system and the selection of regional technology need to be improved.Exploring the water ecological function zoning in this region is of great significance for river health management in the upper reaches of the Yellow River.This paper studies the water ecological function zoning of the Yellow River in Gansu and Qinghai sections.The main conclusions are as follows:1)In the four-tier water ecological function zoning index system of the Ganqing Section of the Yellow River Basin,the first-tier index is altitude,annual precipitation and average annual temperature;The secondary indexes are slope and ecosystem hydrological regulation capacity.The tertiary indexes are land use type and permafrost distribution.Four indexes are meandering degree and gradient of reach.Based on the SWAT model,subwatershed boundary was extracted,and the study area was divided into 5 primary,24 secondary,67 tertiary and 347 quaternary functional zones.2)the surface runoff yield function best area is located in the south as the study area,the area of rainfall is rich,and the function of the worst areas mainly in the study area and landscape mainly for the loess hills,less rainfall and temperature is higher,basic for urban land use types of cultivated land.The water conservation function is better in the source region of the Yellow River and the Qilian Mountains,and it is located in the southwest and part of the northern part of the study area.This area is dominated by plateau mountains,and most land use types are forest grassland,while the area with poor water conservation function is mainly in the northeast of the study area.The distribution of habitat maintenance function levels is relatively discrete.The best functional areas are mainly concentrated in the middle and south of the study area,mainly in the upper reaches of Taohe River,Daxia River and Baihe River,etc.The geomorphology in this area is mainly plateau mountains,while the worst functional areas are mainly in the northeast of the study area.In addition to the Jinghe River basin,Taohe River downstream and the areas around Xining,the soil conservation function has a basic preference.The landforms in the regions with poor function are mainly loess hills,densely populated cultivated land,more water resources utilization,and water and soil erosion easily.3)Combined with regional environmental characteristics and water ecosystem service characteristics,the regional characteristics of each first-level water ecological function zone were analyzed.Meanwhile,the regional environmental characteristics of all second-level zones under YR Ⅱ,all third-level zones under YR Ⅱ-3 and all fourthlevel zones under YR Ⅱ-3-2 were analyzed successively,taking the transition zone from Qinghai-Tibet Plateau to Loess Plateau as a typical region.Based on the land use data of 1990 and 2015,the main ecological and environmental problems faced by each region were analyzed.Combined with the water ecosystem service function led by the region,some decision-making suggestions were put forward.At the same time,the differences between the existing policies and this study were analyzed by comparing with the existing policies.The characteristics of different water ecological functional zones in the Ganqing Section of the Yellow River Basin are very different,so the environmental problems and construction schemes should fully consider the actual situation and characteristics of each.