Groundwater development and management shared between Ethiopia, Kenya and Somalia, within the Genale-Dawa River Basin (Juba Watershed).
The Dawa Aquifer extends from Negele in southern Ethiopia, through Mandera County in north-eastern Kenya, to the Gedo Region of south-western Somalia. It occupies a semi-arid to arid zone, with mean annual rainfall ranging from 250-300 mm in the southern lowlands to 600-700 mm in the Ethiopian highlands, against a potential evapotranspiration exceeding 2,000 mm/year.
Its natural limits are defined by the Ethiopian Highlands to the north-west, the Derkali Plateau in Mandera West, and the Sengif Antiform to the south-east, which marks the structural boundary of the Luuq-Mandera Basin.
| Riparian state | Area (km²) | Share |
|---|---|---|
| Ethiopia | 18,587 | 60% |
| Kenya | 10,519 | 34% |
| Somalia | 1,441 | 5% |
| Total | 31,000 | 100% |
The study delineated four distinct groundwater bodies within the Dawa system, differentiated by geology, depth, yield, flow regime and water quality. The terminology "Upper", "Middle", "Lower" and "Alluvial" is spatial and does not imply stratigraphic correlation.
| Body | Area | Depth | Yield |
|---|---|---|---|
| Upper Dawa | 17,744 km² | 40-250 m | < 10 m³/hr |
| Middle Dawa | 4,587 km² | 20-200 m | < 20 m³/hr |
| Dawa Alluvial | 872 km² | 5-30 m | < 60 m³/hr |
| Lower Dawa | 6,417 km² | 66-260 m | < 5 m³/hr |
Recharge occurs through direct rainfall infiltration, riverbed infiltration along losing reaches, and localized infiltration through structurally controlled zones. It ranges from approximately 37 mm/year in the south to nearly 200 mm/year in the north-western highlands.
The calibrated model confirms that river-aquifer exchange dominates the flux by a wide margin over diffuse recharge.
| Component | Rate (m³/day) | Role |
|---|---|---|
| River inflow (river → aquifer) | > 1,130,000 | Dominant inflow |
| Diffuse recharge (rainfall) | 303,189 | Secondary inflow |
| Abstraction (baseline) | 3,107 | Negligible outflow |
| Total system flux | ≈ 1,434,178 | System throughput |
A calibrated MODFLOW model was used to compare a baseline scenario, a climate-stressed scenario (reduced recharge, increased abstraction) and an intervention scenario incorporating a 5% increase in managed recharge alongside fifteen additional production wells.
| Component | Climate-stressed | Intervention | Interpretation |
|---|---|---|---|
| Recharge in | 257,711 | 270,596 | ↑ Managed recharge effect |
| River in | 1,144,073 | 1,140,961 | Slight decline in dependence |
| Abstraction | 4,480 | 6,430 | ↑ 15 new wells |
| Mass-balance error | ≈ 0.00% | ≈ 0.00% | Numerically stable model |
Key finding: even under full project development, total withdrawals (6,430 m³/day) represent less than 1% of total system flux — with no detectable drawdown propagation, flow reversal or storage instability.
Sites were selected to collectively represent the full recharge-transmission-discharge continuum and to provide complementary data for the future transboundary decision-support system.
Shallow-to-moderate alluvial-sandstone aquifer; fresh Ca-HCO₃ water.
Shallow saline interface requiring grouted steel casing (≥ 40 m) and continuous EC monitoring.
Shallowest alluvial aquifer (~20 m); clay aquitard protection; highest aggregate demand.
Across much of rural Somalia and north-eastern Kenya, groundwater meets 80-95% of total water demand, yet current per-capita access is just 7-13 litres/day — well below the WHO emergency minimum of 20 L/day.
| Riparian state | Demand estimate |
|---|---|
| Ethiopia | ≈ 28 Mm³/yr (domestic demand; livestock and irrigation not yet quantified) |
| Kenya | ≈ 35.8 Mm³/yr (sub-basins 5HB + 5HA, centred on Mandera; domestic, irrigation, livestock) |
| Somalia | ≈ 3 Mm³/yr (preliminary domestic demand, Belet Xaawo and Doolow) |
The Dawa Aquifer is an extensive, multi-layered system of four distinct groundwater bodies, with substantial storage capacity and strong buffering power. Some 73% of its area shows moderate-to-very-high potential. With river-aquifer exchange dominating the flux and current abstraction negligible, the system can sustain the proposed scale of development without measurable regional impact, while its water balance can be actively improved through managed recharge.
Against acute and growing human dependence on a resource delivering a service far below emergency standards, the evidence establishes that sustainable, equitable and climate-resilient development of the Dawa Aquifer is technically warranted, provided that abstraction is matched by systematic monitoring and adaptive management.
| Rev. No. | Revision objective | Date | Developed by | Verified by | Approved by |
|---|---|---|---|---|---|
| 0 | First emission | October 2025 | SW, SO, JW, GS | JK | VM |
| 1 | Second emission | June 2026 | SW, SO, JW, GS | JK | VM |
Submitted by SGI S.p.A. (Via della Provvidenza 15, 35030 Sarmeola di Rubano, Padova – Italy) under the regional Horn of Africa Groundwater for Resilience program (P174867), financed by the World Bank and coordinated by IGAD.