Be like the beaver: build more dams

Floods bring costs and benefits. Heavy rain, especially after a drought, causes heavy erosion in the higher country, and then spreads lots silt (erosion products) onto the flood plains, causes siltation of river mouths or carries this valuable soil conditioner into the sea. Silt is fertiliser for the plants of the flood plain, but many people forget this and curse the silt and work against nature by trying to control the flood waters with banks and levies.

Dams are used for two purposes – water supply and flood mitigation. However, one dam cannot do both things well – for water supply it need to be kept as full as possible, but for flood control it needs to be empty when the rains start.

The best way to conserve and ration water for the land is to use the Keyline ripping/contouring ideas of PA Yeoman. This process delays water runoff and its associated erosion. It will also conserve water for local pastures and trees and make the flow of water into creeks and rivers cleaner with a steadier supply.

However some people have other ideas:

"We must reclaim the roads and plowed lands, halt dam construction, tear down existing dams, free shackled rivers and return to wilderness tens of millions of acres of presently settled land."

David Foreman, a founder of "Earth First".

The "No Dams" crowd should learn from the beavers. Strings of dams can moderate flood risk, as well as creating drought sanctuaries and secure water for graziers, towns, irrigators and wildlife. Modern cities could not survive without large water storages for drinking water, sanitation, gardens and factories.

Fresh water is also necessary to produce fresh food. We can have fresh milk, butter, cheese, meat, vegetables, nuts and fruit; or we can irrigate the oceans and import fresh food from more sensible countries. And without fresh water and fresh food, there will be no local food processing.

Those infected with the green religion believe we should waste our fresh water by allowing it all to return as quickly as possible to the salty seas. They fight to protect beaver dams and natural lakes, but persistently oppose human dams and lakes. Some even want existing dams destroyed, while wasting billions on energy-hungry desalination and sewerage water recycling plants, pumps and pipelines.

They also want to prohibit man's production of two drought-defying atmospheric gases, both released by the burning of hydrocarbons – carbon dioxide which makes plants more drought tolerant, and water vapour which feeds the clouds and the rain.

Green water policies are un-sustainable, even suicidal.

Humans must copy the beavers and "Build more Dams". And help the biosphere by burning more hydrocarbons.