Sustainable management of fresh groundwater resources in coastal East Africa - Using lessons from the past to build future resilience to climate and

Title: Sustainable management of fresh groundwater resources in coastal East Africa - Using lessons from the past to build future resilience to climate and environmental change

High coastal population growth rates, with associated water demand and environmental changes including climate change are putting enormous pressure on coastal groundwater resources. Groundwater is more resilient to increasing climatic extremes, and is the only source of water during droughts, but if over-extracted, is vulnerable to depletion and underground salinisation from the ocean.

In East Africa (EA), increased birth rates, development and migration from inland areas have increased demand for water and land leading to poor sanitation and water supply. Groundwater is often the only year-long reliable source of freshwater essential for sanitation, agriculture, and consumption but saline intrusion causes long-term contamination.

The UNESCO World Heritage property of Kilwa Kisiwani (KK), a small island off the coast of Tanzania, was once a particularly celebrated maritime city-state which dominated a large part of the Swahili coast during the late medieval period. KK was then a prosperous city with many mosques and palaces, described by the 14th-century explorer Ibn Battuta as, 'the most beautiful of cities and elegantly built'.

Various authors record KK had a population of between 4,000 and 30,000 in the 16th-century, which had declined to ~1,000 by the 19th-century, but is currently rising again to over ~1,200 people.

Archaeological evidence suggests that, after some time, the island's freshwater could no longer sustain the sultan's palaces, pilgrims to the mosques and seafaring traders. Today, the island has the remains of at least 17 stone-wells, most of which are abandoned or too salty to drink. Three are still in use though have higher levels of salinity than on the mainland. Previous well excavations on KK have shown the water table to be up to 2m higher in the 14th-century.

The multidisciplinary project will investigate how availability and quality of freshwater from wells contributed to the decline of KK at different stages of its history, and how water management can alleviate water shortages allowing local development of the EA coast and island communities.