Drought Criteria

Rainwater catchment is an anticipatory response to drought. Catchment design requires a prudent definition of target drought. Target drought might be a normal dry season, two rainless weeks, etc. Definition is by both duration and depth of precipitation. Target draught is often a balance drawn from past hydrologic history, consequences of rainwater catchment system failure, social implications and public acceptance. Most of the numerous drought indices are inappropriate as catchment performance targets. This paper briefly reviews drought definitions and suggests an analysis for identifying proper rainwater catchment design criteria. Analysis must anticipate the variety of meteorological futures that a catchment might experience. Stochastic analysis improves understanding of probable catchment behavior and the risks associated with alternative catchment designs. Drought Duration Depth Frequency analysis allows the time step for which a system is sized to be matched to the duration of drought. An example illustrates such assessment