Drought Assessment in Zacatecas, Mexico

Water has always been an essential development factor for civilizations, but its erratic distribution in space and time has caused severe socio-economic problems throughout human history due to both scarcity and excess. In Mexico, insufficient rainwater to satisfy crop water requirements is a recurrent phenomenon. From a meteorological perspective, drought refers to a decay of the rainfall-runoff process below normal values, resulting in lower availability of water resources to satisfy the needs of human activities, particularly those related to agriculture and livestock. This research reports on drought assessment for Zacatecas, Mexico using monthly data from 111 weather stations with temperature and precipitation information from a 33-year period. Drought was characterized by applying the Standardized Precipitation Index and the Reconnaissance Drought Index using 3, 6, and 12 month timescales; both indexes were plotted and mapped for the period 2005 to 2014. The trend indicates rainfall anomalies (from incipient drought to severe drought) in 6 or 7 years, depending of the selected timescale. April was selected to start the drought analysis because it is the month when farmers usually establish rainfed crops in the region. In ten years, Zacatecas has lost 478 million US dollars due to drought. 2005, 2009, and 2011 were the most critical years, with 47%, 39%, and 63% losses in agricultural income. Such values are in agreement with drought severity estimates: 2005 and 2011 were both dry years (drought indexes were less than 1.25 in the whole territory).