Author : USAID/Sustainable Water Partnership (SWP)
Site of publication : globalwaters.org
Type of publication : Working Paper
Date of publication : 15, July 2021
Senegal has abundant freshwater resources but seasonal and regional variability in surface and groundwater availability is high. Senegal’s dependency ratio is considered high relative to other countries in Sub-Saharan Africa as approximately 34 percent of its water resources originate outside the country. Water sector restructuring, policy reforms, and emphasis on decentralization aim to strengthen water governance, quality, and availability. Low funding, limited data collection, and sector coordination challenges have impeded implementation of water management plans.
Surface Water Resources
Most renewable water supply is derived from surface water in five main drainage basins: the Senegal River, Gambia River, Casamance River, the Kayanga River, and the Sine Saloum. Senegal has several man-made dams and reservoirs, which regulate surface water flows for irrigation, prevent inland saltwater intrusion, and generate hydropower. Approximately 8.6 percent of Senegal’s energy is derived from hydropower.
Groundwater is the primary source for domestic consumption, livestock watering, mining and industry, and some irrigation. Groundwater availability, productivity, and depth vary by region. The shallowest aquifers are located near Petite Côte, Casamance, and the central western regions of Fatick and Kaolack, while the deepest are found in the Thiès region.
Surface Water Outlook
Demand for surface water is highest in the Senegal and Gambia Basins, primarily for agriculture. Agriculture accounts for 93 percent of total water demand compared to domestic (4.4 percent) and industrial uses (2.6 percent). Invasive aquatic plant growth has reduced the flow and oxygenation of surface waters and is impacting Lake Guiers, which is a key source of drinking water.
Industrial effluents and human wastewater have contaminated surface water, particularly near urban areas. Only 15 percent of household wastewater is treated and this has increased the incidence of water-borne diseases. Erosion and siltation are prevalent near agriculture and in coastal river deltas. River bank erosion is widespread in the lower Casamance Valley and Senegal Basin near Lake Guiers and the Lower Ferlo Valley.
Groundwater is the primary source of water for drinking and domestic use in rural and urban areas. Boreholes are highly concentrated in central western Senegal, which relies almost exclusively on groundwater. Groundwater is threatened by overexploitation and low recharge rates. Nationally, groundwater levels are decreasing by 0.30m–0.67m annually due to over abstraction.
Untreated wastewater and agricultural runoff has led to nitrate and bacteriological pollution, posing risks to urban groundwater supplies. In Dakar, nitrate concentrations were found to be approximately ten times higher than the WHO drinking water guideline.
Water Resources and Climate
Between 1996 and 2019, 1.8 million people were affected by drought and 1.2 million were affected by flood events. Prolonged drought between 1970 and 2000 contributed to rural-urban migration and today approximately three quarters of urban residents reside in unplanned settlements that are vulnerable to extreme flooding caused by heavy rainfall events. While it is uncertain whether total precipitation will increase or decrease with climate change, rainfall intensity is expected to increase, although they will occur less frequently.
Drought, erratic rain, and prolonged dry spells at critical points in the growing season are a significant risk to Senegal’s climate-sensitive, rainfed agricultural economy. Approximately 70 percent of agriculture is rainfed and vulnerable to changes in rainfall due to climate change. Coastal flood risks are considered high, particularly the central and southern coastal regions. Sea levels are projected to rise by one meter by 2100, creating extreme coastal flooding risks.
Water Policy and Governance
Water sector strategic plans emphasize integrated water resources management but implementation of the plans has been slow. Low government funding and human resources and institutional capacity constraints impede implementation of integrated water resources management and investments needed to protect water quality and availability.
Transboundary cooperation is vital to Senegal’s water security, as 34 percent of the country’s water originates outside the country. Senegal has signed six multilateral agreements covering the Senegal River Basin alone, as well as other international agreements. Throughout the country, there is a limited understanding of the quality and availability of water resources, vulnerability to climate change, water use, and risks of pollution.
Limited data collection and management challenges with monitoring and data systems have introduced uncertainty into water quality and abstraction data. Limited coordination between the water quality agencies and low funding compound these challenges.
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