Preliminary Study On Regional Water Cycle Health Evaluation

With the intensification of human activities and global climate change,the original balance and laws of the natural water cycle system of the river basin have been broken.It has a dramatic impact on the natural water cycle,gradually evolving from a single cycle process led by nature to a "natural-social" dual model.In this realistic situation,how to maintain the healthy state of the water cycle has become an important proposition for the sustainable use of water resources.In this paper,Yinchuan City is selected as the research area to conduct a health assessment of the urban water cycle status in the past 9 years.At the same time,through the indoor experiment simulation to explore different recycled water as a substitute water source under different conditions of water supply ratio changes in landscape water quality changes.The main research contents and results are as follows:(1)Water cycle health evaluation builds an index evaluation system including four dimensions and 15 evaluation indexes.And put forward the index health threshold.(2)The evaluation results found that the evaluation scores of each dimension layer are quite different:the evaluation scores of water environment quality and water ecological level are high,and they have reached a healthy state over the years;the abundance of water resources is in a sub-healthy state,which has been stable for many years.Floating changes are very small;although water resources utilization is in a morbid state,the trend is good and there is an upward trend.(3)The comprehensive health status of the water cycle in Yinchuan City was in a sub-health state from 2009 to 2017,and the health score from 2015 to 2017 has been rising.The health score in 2017 reached the highest level,close to the health state.This shows that the urban water cycle in the region has improved under strict control conditions.(4)Judging from the comprehensive results,the importance of the amount of waste water recycling is ranked first,and it is one of the key indicators that affect the health level of the water cycle.Whether the recycling of sewage is healthy or not will seriously affect the health of the city's water cycle.(5)After identifying the key factors,an experimental study was conducted on the use of recycled water as an alternative water source to supplement landscape water bodies.The results show that all the indexes except the total nitrogen in the experimental group with different proportions in each season change with time are in line with the standard of landscape water for reclaimed water.Due to the high temperature in the summer test,the water quality will continue to deteriorate when the proportion of reclaimed water in the still landscape water exceeds 75%.Therefore,it is recommended to supplement the water body in Baohu in summer.The proportion of reclaimed water is recommended to be 50%-75%.In other seasons,the reclaimed water can completely replace the Yellow River water.It should be noted that both lake water and reclaimed water have the problem of too high total nitrogen content.Excessive nitrogen and phosphorus content may cause eutrophication,and measures such as purification of aquatic plants can be used to make the water quality meet the standards.