Multi-Scale, Multi-Season, Multi-Indicator Evaluation Of Agricultural Drought Trends In Ethiopia

Abstract

Agriculture plays an important role in Ethiopian economy and country’s GDP livelihood relay on it. Most of agriculture in Ethiopia is rainfed even small household farms without irrigation facilities. Ethiopia is drought-prone country therefore, droughts significantly affect crop production. Understanding droughts is therefore important for food security of Ethiopia. Intra season and seasonal drought trends in Ethiopia were studied using a suite of drought indicators— standardized precipitation index (SPI), standardized precipitation evapotranspiration index (SPEI), Palmer drought severity index (PDSI) and Z-index for Meher (long-rainy), Bega (dry), and Belg (short-rainy) seasons to identify drought-causing mechanisms. Trend analysis indicated shifts in late-season Meher precipitation into Bega in the southwest and southcentral parts of Ethiopia. Droughts during Bega (October – January) are largely temperature controlled. Short term temperature-controlled hydrologic processes exacerbate rainfall deficits during Belg (February–May) and highlighted the importance of temperature and hydrology-induced soil dryness on production of short-season crops such as tef. Droughts during Meher (June – September) were largely driven by precipitation declines arising from the narrowing of the intertropical convergence zone (ITCZ). Increased dryness during Meher had severe consequences on the production of corn and sorghum. PDSI is an aggressive indicator of seasonal droughts suggesting the low natural resilience to combat the effects of slow-acting, moisture-depleting hydrologic processes. SPI shows significant drying trends (meteorological droughts) and it is most rampant during December, February and July within seasons of Bega, Belg and Meher respectively. SPEI indicates drying trend in December, March and September. Z-index shows moisture deficit (agricultural drought) in October, March and September during Bega, Belg and Meher season respectively. This affects both long cycled and short cycled crops. The lack of irrigation systems in the nation limits the ability to combat droughts and improve agricultural resilience. There is an urgent need to monitor soil moisture (a key agro-hydrologic variable) to better quantify the impacts of meteorological and agricultural droughts on agricultural systems in Ethiopia.