Assessment of drought occurrences in Zhob District using Standardized Precipitation Index from 1981-2018

Abstract

Background: It is valuable for the policy makers to configure and assess the severity of drought in a particular area having arid climate, remote rural settlements and history of prolonged drought spells.

Objective: This study identifies and assesses the onset and extent of drought in the Zhob district by studying its spatio-temporal pattern using geospatial techniques.

Methods: In a longitudinal timeframe study (1981-2018), the precipitation data was collected from two rain gauge stations across Zhob district to assess the precipitation trends and calculate Standardized Precipitation Index values at multiple timescales. The values were then projected spatially as well as temporally to study the subsequent patterns and spatio-temporal extent of drought.

Results: The findings revealed that over the past 38 years, the Zhob district has experienced waves of dry and wet spells out of which the two prolonged drought spells were identified as 1998-2002 and 2015-2018. Both the periods differentiate in pattern and extent of spread; however detailed study of the later drought period was carried out to configure the differences in category and extent of the drought when compared on multiple timescales.

Conclusions: The spatio-temporal drought trends of past 38 years in the study area revealed how differently the drought expands over an area when assessed on various timescales. The precipitation anomaly when studied in conjunction with frequency of drought recurrence in the study area, revealed patterns indicating onset and other characteristics of drought. Such indications if rightly pointed out by the government agencies would help farmers and local populace to timely ascertain the approaching drought.