ABSTRACT

Effective planning of land use on watersheds must be based on quantitative information on the physical resources of climate, topography, geology, soils, vegetation, and water resources. If watersheds are inhabited, then further information is required on the numbers and distribution of people and animals, communications, economic and subsistence landholdings, and farming systems. Rainfall amount and seasonal pattern are such critically important pieces of information that measurements should begin at the earliest stage in programs of watershed management or development. The numbers of rain gauges required depends largely on whether the results are to be used for research, such as water-balance studies, or for general purposes of watershed management. Watershed managers find that the technical literature describes many devices for improving the accuracy of rainfall measurement. Watershed management authorities in the tropics are liable to receive conflicting, but trenchant, advice from interested parties about the probable effects of proposed changes in land use.