ABSTRACT
Drought is the most complicated but least understood of all natural hazards, affecting more people than any other natural events. It is a normal, temporary, recurrent feature of climate, although it is inaccurately considered as a rare and random event. Drought has been documented among the earliest extreme climate events. Wilhite & Glantz (1985) reviewed drought definitions and identified six general drought categories: meteorological, climatological, atmospheric, agricultural, and hydrologic and water management. Salinger & Mullan (1995) defined a drought as a time period that the supply of moisture from precipitation or stored in the soil or hydrological reservoirs is insufficient to fulfill the requirements of plants, urban usages as well as other purposes. In New Zealand, a meteorological drought can be defined as a period of consecutive 15 days with rainfalls less than 0.1 mm per day (Mosely & Pearson, 1997). Likewise, the agricultural drought have often been defined using three months duration as a standard dry period when precipitation or soil moisture is reduced to a level that may be expected on average less than once in 20 years (Porteous, 1995).
