Like a hurricane, flood, earthquake, or tornado drought is a natural disaster. Unlike these other crises, however, drought, in a sense, represents a "non-event"; it is difficult to identify the onset of a period of prolonged drought and it is likewise difficult to isolate the termination point for a period of protracted drought. These complexities are reflected in the problem of defining drought. To the meteorologist drought may connote a period of abnormally dry weather or lack of precipitation. To the geologist or hydrologist drought is viewed in a broader perspective e.g. a sufficient lack of water, including surface and ground water as well as precipitation, so as to cause a significant hydrologic imbalance in an area. From an even broader perspective drought may be defined as a moisture deficit in the physical or natural sub-system of an area that has a significant impact on the human eco-system of that region or area. To view drought from an economic perspective, this latter definition of drought must be accepted; it is only when drought affects the human eco-system that is becomes an economic problem.