River health assessment includes two aspects. One is how to determine the benchmark of river health, and the other is how to deal with the relationship between people and rivers.
To evaluate the health of a river, it is necessary to find a healthy river for comparison, or to find the health status of the river to be evaluated as a benchmark or frame of reference. At present, it is generally believed in the field of ecology that large-scale economic activities of human beings are the main reason for destroying the health of river ecosystems. The original state of rivers before large-scale economic activities is in a healthy state of natural evolution, which can be used as a benchmark or frame of reference for river health.
Some radical environmentalists believe that the original ecological river is the only standard for healthy rivers, advocate restoring rivers to their original state and oppose the development and utilization of rivers by human beings. Anthropocentrists tend to think that rivers are healthy as long as they can meet human needs for water supply, flood control, power generation, shipping and entertainment.
In order to balance these two aspects, river health needs a multi-index evaluation method. Generally speaking, river health is mainly assessed according to four types of indicators, namely, physical and chemical assessment, biological habitat assessment, hydrological assessment and biological assessment. Moreover, for different rivers, the health assessment standards and indicators adopted may be different. A healthy river should be "green as spring water and blue" and clean; There is also a scene of "the eagle hits the sky, the fish is shallow, and all kinds of frost fight for freedom". The biological community is rich and full of vitality. Academically speaking, the ecological structure and function of rivers are relatively perfect and can be regarded as healthy.
The concept of river health broadens people's horizons, from simple water quality protection to river ecosystem protection. In fact, some developed countries have embodied this concept in environmental legislation. For example, the river assessment indicators in the EU Water Framework Directive issued in 2000 are divided into three categories: river ecological factors, river hydrological form quality and river water quality physical and chemical quality factors, with dozens of items, which fully reflect the basic characteristics of rivers. However, at present, there is no overall research result of river health assessment in China. However, in recent years, the Yangtze River Water Conservancy Commission, the Yellow River Water Conservancy Commission and seven river basin management agencies, including Haihe River, Huaihe River, Pearl River, Songliao River and Taihu Lake, have respectively compiled the river health assessment standards in this basin.