Evidence in the Horn of Africa of the resilience of rural water supply to drought

Groundwater is often relied on to provide secure drinking water, particularly in rural Africa, where other options are limited. The increased incidence of drought and its likely escalation due to climate change raise questions as to how resilient groundwater is to drought, and how the performance of different technologies used to access groundwater compares during drought. Here we report the results of three research studies undertaken in Ethiopia to directly address these questions. We first examine hydrographs from 19 wells, springs and boreholes during the 2015/16 El-Niño drought and the years following. Secondly, we report the results of a survey of groundwater recharge for 50 sampled boreholes from 4 woredas (districts) and, lastly, we examine the response of >5,000 different water points from across Ethiopia from January to April 2016 as the drought evolved. The results from the three studies all give a consistent story: groundwater supplies, particularly those accessing groundwater deeper than 15 metres, are resilient to the short-term effects of drought and become increasingly important as other water sources (e.g., springs) fail. Hand-pumpoperated boreholes were often the most reliable sources during drought periods, although motorized boreholes, if accompanied by active monitoring and maintenance, also proved so. Springs and hand-dug wells were generally, but not universally, severely impacted by drought, with those at higher elevations most affected. Recharge studies using environmental tracers suggested that the mean residence time of groundwater (<100 metres deep) is in the order of several decades across the Ethiopian Highlands. This indicates modern recharge is occurring but is not reliant on very recent rainfall; thus, groundwater is both resilient to drought and renewable when managed appropriately. Additional pressures put on groundwater supplies by the drought were shown to be mitigated by an active and sustained campaign of monitoring and maintenance as drought evolved.