What is a healthy river?
Just as there is no single measure for human health, there is no single measure for river health. Rather, a healthy river is comprised of many facets -- biological, physical, chemical, and even human.
It does not have to be a pristine river, untouched by any human development or activities. But a healthy river does have to be resilient and able to recover from natural and man-made disturbances.
A river’s health is measured on a continuum, just as a human’s health is. A river in the wilderness may rank the highest, but a river flowing through a major metropolitan region is not inherently unhealthy. Rather, the traits of an ecologically healthy river will have certain components that fall within a range that allows the river to maintain its ecosystem functions.
Fundamental characteristics of a healthy rivers include:
- A natural flow that varies in magnitude, frequency, duration, timing, and rate of change. A natural flow regime is a critical component for a healthy river because the flow of water provides the base on which all other river functions are built. The plants, fish, and wildlife in any given river have evolved to adapt to that river’s unique rhythms.
- Transportation of sediment and nutrients. Rocks, gravel, sand, silt, and organic debris are important components of a healthy river, creating floodplains, sandbars, riparian areas, and nourishing a river’s bed and channels. A healthy river in equilibrium does not allow too much erosion or excessive scouring of the riverbank and riverbed.
- Strong and varied plant communities. Native plant species provide critical habitat for fish and other riverine animals, regulate water temperatures, prevent excessive erosion of riverbanks, and can remove pollutants from river water. Vegetation as it decomposes is also an important source of nutrients and habitat.
- Productive and diverse habitat that can support numerous animal species. The natural movement of sediment throughout a river creates riffles, pools, side channels, and backwater areas providing both spawning and rearing habitat for many species of fish.
- Good water quality. A healthy river has temperature levels, dissolved oxygen content, salinity, turbidity, hardness, acidity, and alkalinity (water pH) that are all within a natural range for that river and its species. A healthy river will also have minimal amounts of pollution and toxics, such as pesticides, nitrogen, phosphate, fecal coliform, and heavy metals.
- Many macro invertebrates (bugs!). Aquatic insects are the primary food for many riverine species. Abundance and diversity of insect species can be a strong indicator of river health.
- Diversity of fish and wildlife species. While the number of fish and wildlife species will vary with each river, a diverse number of species is often an indicator of river health.
- A community that protects it through wise management and community planning. For example community groups work to ensure that new development is as river-friendly as possible or organize river clean up days and engage other community members in issues related to river health. A healthy, caring community is an essential facet of a healthy river.
From Healthyrivers.org
