Drought
Drought is a complex physical and social phenomenon of widespread significance. It is often the result of many complex factors acting on and interacting within the environment. Complicating the problem of drought is the fact that drought often has neither a distinct start nor end. It is usually recognizable only after a period of time and, because a drought may be interrupted by short spells of one or more wet months, its termination is difficult to recognize.
Droughts can be of three kinds:
(i) Meteorological drought: This happens when the actual rainfall in an area is significantly less than the climatological mean of that area. The country as a whole may have a normal monsoon, but different meteorological districts and sub-divisions can have below normal rainfall. The rainfall categories for smaller areas are defined by their deviation from a meteorological area's normal rainfall -
Excess: 20 per cent or more above normal
Normal: 19 per cent above normal - 19 per cent below normal
Deficient: 20 per cent below normal - 59 per cent below normal
Scanty: 60 per cent or more below normal
(ii) Hydrological drought: A marked depletion of surface water causing very low stream flow and drying of lakes, rivers and reservoirs
(iii) Agricultural drought: Inadequate soil moisture resulting in acute crop stress and fall in agricultural productivity
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