Droughts are typically categorized into four major classes:
(a) meteorological drought, a deficit in precipitation;
(b) hydrological drought, a deficit in streamflow, groundwater
level or water storage; (c) agricultural drought, a deficit in
soil moisture; and (d) socioeconomic drought, incorporating
water supply and demand (Anderson et al 2011, Wilhite and
Glantz 1985). All four categories of droughts are related to
a sustained lack of precipitation and thus, having accurate,
long-term, and timely precipitation data is fundamental to
drought monitoring and analysis.