Researching contribution of forests to sustainable water resource management

The health of streams and watersheds is tied directly to forests. Forests increase the resiliency of watersheds through water storage, soil protection, and filtering processes. Forests are also an integral part of future strategies for reducing global warming, controlling storm water, and improving quality of life.

Tropical rain forests are the source of many of the world's most important watersheds. The water that is not used by the plants and animals of the tropical rain forest or recycled into clouds finds its way into river systems that sustain, by providing water for irrigation, navigation, and drinking, some of the largest concentrations of people on the planet – in South and Southeast Asia, in Africa, and in South America. The levels at which the tropical rain forest releases water into its rivers, the seasonal rates at which it does so, are features of the rain forest watershed that people who live far from the forest depend upon for their daily survival.

Many watersheds are severely affected each year by wildfires, intensified by declines in forest health. Catastrophic fires can destroy watershed functions and stream conditions for decades. The effect of forest loss and the importance of sustaining the health of forests should be recognized as an integral part of future watershed, water quality, and pollution prevention strategies.

This strategy features in the framework of Agenda 21 as formulated at UNCED (Rio de Janeiro, 1992), now coordinated by the United Nations Commission on Sustainable Development and implemented through national and local authorities. Agenda 21 recommends promoting and expanding research into the contribution of forests to sustainable water resource development.

A Victorian Government sponsored study, for example, calculated the financial benefit of water supplied to Melbourne from forested catchments at $250 million per year. This amount is based on a study which valued water collected in the Thomson Reservoir and supplied to Melbourne at $530 per megalitre, and the fact that the bulk of water supplied to Melbourne is harvested from 80 000 ha of catchment forested with ash-type eucalypts. Annual water yields from these forests vary from six to twelve megalitres per hectare, depending on whether the forest is 30 year old regrowth or oldgrowth more than 200 years old. Presently most of the ash-type eucalypt forest in the catchments is 54 years old. Over the next 50 to 100 years, as the regrowth forests age, the value of water produced each year will increase by $150 million due to natural streamflow increases.