This manual is intended to provide basic knowledge and practical approaches to watershed managers and planners, who are involved in watershed survey and planning in developing countries.
The watersheds in mind are upland or hilly watersheds with combinations of forest, cultivated, or grazing lands and populated mostly by subsistence farmers.
The guide is aimed primarily at middle-level technicians in order to enable them to carry out the actual planning work, with the assumption that concepts, strategies, problems and overall solutions have already been worked out at the appropriate decision making levels in consultation with the land users.
A watershed programme, in order to be effective, has to carry out a relatively intensive effort in a limited area, which therefore has to be very carefully identified and selected. The important catchments of a country will typically be mountain areas with high rainfall and their priority rating will depend on the related downstream interests, city water supply, hydroelectric power generation, irrigation schemes, floodplain protection, etc. They will in many cases not coincide with priority areas for national soil conservation programmes aiming at increased sustainable food production from the nation's farm land, or community forestry programmes designed to meet the needs of the local people in areas of scarcity of wood products.
Watershed problem analysis, incentive packages, road construction standards, enforcement of forest protection regulations, etc. are therefore not necessarily those applicable to rural development, soil conservation, and forest protection, etc. nation-wide. However, any special arrangement made in a critical watershed places severe limitations on its applicability and sustainability outside the catchment and over time.
The watershed planner should be aware therefore of new approaches and strategies in soil conservation and land management, farming systems analysis and development, community forestry, etc. and realize that although the identification and selection of priority watersheds is made at central level with downstream interests in mind, it is the upstream land user who is effectively the watershed manager through his or her land use decisions. The challenge is to harmonize "top-down" central planning selection of critical and priority watersheds with a "bottom-up" approach in which farmers will participate actively because of the benefits to them from improved land husbandry practices.
The survey examples given in this manual are for reference only and should not be taken as step by step instructions. Watershed management is site specific and no method, however sound, can be applied universally without modifying it to suit local needs.
The manual is divided into three parts. The first part gives an overall introduction and explains what preparatory work is needed. The second part starts with survey approaches and techniques in general, followed by a long section (chapter 7) of specific techniques and examples, many of which are from actual experiences. The third part concentrates on planning and plan formulation. A brief introduction to the use of microcomputers for this purpose is placed in Appendix 3 for reference.
It should be pointed out that, in practice, survey and planning is a continuous process and that the divisions included in this manual are only for the sake of analysis and clarity of presentation.