Water is so important to the wellbeing of an ecology, and while sometimes it is doubtful whether dams improve an ecology or not, they remain a fundamental tool of at several species to improve a local environment.
Learning from beavers, water rats and other dam makers, we understand that a good dam is one that retards water flow rather than slows or stops it entirely. A beaver dam does not significantly change the rate of water flow, but it does retard the direction enough that a pond develops without robbing downstream of more than its fair share of water.
Humans make dams too. Some of our dams imitate those of our favorite water rodents, but others are our own invention entirely. Our dams typically reserve water (in a “reservoir”) for our agriculture, stealing water from downstream for use at the dam – or in a distance from the dam by way of canals. But some other human dams – many of which can be seen in Elbert County and throughout Colorado – are constructed by farmers who use the water on site at the pond, and are made in a similar way that rodent dams are made.
When water is retarded in its flow, more trees will grow, and these trees increase the amount of rainfall, gradually changing the environment to have more water. They immediately reduce the evaporation of groundwater, and encourage the biodensity required to improve ground retention of water. They increase biodiversity, and generally are useful to the improvement of the land itself into a healthful climate for human life.
Deserts can be made to bloom without water, as has been shown by Dr. Masanobu Fukuoka and others. By simply increasing the amount of plant life, we increase the amount of soil fungus and microorganisms, and improve the water retention of the soil; we increase biodiversity and biodensity in our fields to increase our yields. Greening deserts needs no dams, if you have the hundreds of years to wait.
But good dams can be made to green the desert, or at least reclaim the lands creeks and rivers may again flow.