Rapid Hydrological Appraisal: an integrated rapid approach to assess watershed function

Watershed function: why do we want to assess itHydrological functions of watersheds are very much influenced by the amount of rainfall that the watershed area receives and its underlying geology and land form. The functions include the capacity to:9Buffer peak rain events, 9Release water gradually,9Transmit water,9Maintain water quality and9Reduce mass wasting (such as landslides).The relation between land use and the flows of water to downstream areas is important, because human demand on water for agricultural production, industries and domestic use are globally increasing, while supply is stable. Fears that the quality, quantity and regularity of flow of water from uplands is affected by ‘deforestation’are the basis of land use regulation, restricting opportunities of upland people to make a living the way they want and see fit. Land use mosaics in upland areas provide important parts of environmental service functions. Communities gain income/direct benefits from what they harvest, grow or extract from these upland landscapes. Yet, there is no income for maintaining the landscape in order to produce environmental service functions for off-site and downstream beneficiaries. Maintaining or enhancing these functions thus remains an ‘externality’ to their decision making. The current perception in watershed management is that forest is the land use that can ‘best’ maintain watershed functions and changing landscape mosaics from forest into other form of land use will reduce the ability of the watershed to maintain its functions. This perception is debatable. How good or bad actually are non-forest land uses in maintaining the watershed function Can tree-based systems provide similar service as forest in maintaing the watershed function The answer to these questions are of interest and of importance to the policy makers in developing the watershed management policy. These answers are also of interest for the development of reward mechanism for the upland people for the environmental services they provide.

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