Seawater intrusion in the coastal aquifers of East Africa and the Horn of Africa: A review from a regional perspective

Abstract As coastal areas continue to experience population and economic growth, this calls for a more holistic understanding of its attendant environmental challenges towards ensuring sustainability. The over 8300km continental coastline stretch of East and Horn of Africa from Sudan to Tanzania is not an exception. A typical challenge with coastal areas is seawater intrusion (SWI) into coastal aquifers. Several efforts have been made in understanding this phenomenon and developing management strategies in different parts of the world. This has led to an evolution of different techniques for assessing the extent of seawater intrusion. This paper explores the status and extent of SWI studies in the region, focusing on the trend of techniques and methodologies used in the past 5 years. At a regional level, there is more empirical knowledge on SWI in Kenya, Djibouti, and Tanzania while that of Sudan, Eritrea, and Somalia are largely vague for obvious reasons – more studies have been conducted in the former countries. Hydrogeochemical technique coupled with statistical and analytical tools is the most prevalent approach. The review shows that the extent of SWI vary significantly from location to location but rarely extended beyond a few km inland in the region. SWI extent and severity was also shown to vary with seasons in studies covering temporal dimensions. The review shows that more research capacity building is needed especially in countries like Sudan, Somalia, Djibouti and Eritrea. Finally, recommendations on SWI research and management frontiers to explore in the region are suggested.