The new generation of watershed management

The interplay among land topography, vegetation cover (particularly forest cover) and water flows has been the core focus of watershed research and management for the last 20 years. However, some studies and experiences presented by review participants challenge the common wisdom about interactions among these factors. For instance:

• The impact of land use and vegetation cover on water flows varies significantly with the type of land use, size of the watershed, climate, soil characteristics, topography, geology, etc. In the past, the need to take into account the specific characteristics of each situation was frequently overlooked. This led to overgeneralizations and oversimplifications in policy-making and practice.
• Forests are beneficial for watershed health, but tend to use more water than other types of vegetation cover. Forests therefore may reduce water supply to aquifers or river systems.
• The impact of land use on water regime and availability is largely a matter of scale. Appropriate land management contributes significantly to regulating water flows in small watersheds, but when large river basins are considered the impact of land use on the hydrological regime becomes insignificant compared with that of other factors, such as the intensity of extreme rainfall events. At larger scales, however, land use does have a significant impact on water quality.
• There is increasing evidence that climate and human-induced changes are affecting the hydrological cycle. The impacts of these changes depend on both rainfall volume and land-use practices: a slight increase in event-precipitation is likely to have a much larger impact on runoff and flood discharge when inappropriate watershed management practices are applied.

Read the case study: Himalayan deforestation and downstream floods .

Would you like to know more? Go through the forest hydrology briefing.