1.6 – Surface and groundwater

The Albertine graben area has significant amounts of surface water resources including lakes and rivers (Section 1.2). The rivers/streams originate from the elevated grounds on the escarpment and  mountain ranges and flow down into the Rift Valley. There are also a number of Rift Valley lakes whose waters are mainly derived from the flowing rivers. The area is drained by numerous perennial rivers including Amua, Nyawa, Kochi, Enyawu, Nyagak, Aswa, and Zoka in the north east of the graben. In the Lake Albert area, rivers like Sambiya, Victoria Nile, Semliki, Hohwa, Wambabya, Waki, Waiga, Sonso, Waisoke and Muzizi are found. The central sections of the graben have rivers Mpanga, Nyamwamba, Mubuku, Kyambura, Oruyubu and Rusangwe, while the south western sections of the graben have rivers Nyamugasani, Ishasha and Mitano- Ntungwa in addition to small seasonal streams.

Furthermore, a series of erosion valleys and gullies cut the escarpment and discharge runoff from the escarpment to the valley. There are also seasonal streams and rivers which are flooded by runoff from the catchment areas after a heavy rainfall event. For example, in the Lake Albert area, water from these rivers drains quickly either into Lake Albert or seeps into the thick sediments of the Rift Valley floor. The seasonal rivers in this area include Sebugoro, Kabyosi, Warwire and Nyamasoga.

Most of the rivers and streams have incised into the landscapes leading to a topographic pattern of narrow river valleys and sometimes gorge-like features. Due to the nature of rift escarpment landscape, the rivers and streams flowing into the Rift Valley often have a limited catchment size and this implies limited hydrological potential. Consequently, some of the scarps are drained by ephemeral (intermintent) flows to the extent that some of the river valleys are dry most of the time.

The most spectacular landscape of river flow is perhaps the Victoria Nile. The Victoria Nile runs east-west through Murchison Falls National Park for over 80 km. Between Chobe and Paraa, the Nile drops 350 m through stretches of white water rapids and cascades. The most dramatic feature along this reach is Murchison Falls, where the river has cut back through the Rift escarpment plunging 45m below, with huge convulsions through a cleft only 6 m wide. At this point, the falls may be discernable into two separate features. Apart from Murchison falls, a further spill occurs over an adjacent cataract known as ‘Uhuru Falls’ formed in 1962 (year of Uganda’s independence). Below Murchison Falls, the river flows out of the gorge to become calmer and wider, before finally entering Lake Albert as a delta (now a Ramsar Site). While Victoria Nile is responsible for most of the surface drainage in the protected area, smaller watersheds divert drainage into Waiga and Waisoke rivers which discharge into Lake Albert south of Buliisa. The Albert Nile drains in Lake Albert to the north.

Further south-west, the Rwenzori Mountains become the most important water catchment with numerous rivers descending from the high rainfall and snow-capped mountain to the Rift Valley floor and into lakes George and Edward. The key rivers in this area include rivers Mubuku and Nyamwamba. On the other hand numerous rivers and streams drain from the escarpment and highland areas beyond to the rift valley zone, and also often end up in the lakes.

Some ground water resources exist in a number of locations, the hydrology of which is undoubtedly influenced by a number of environmental conditions including geology, rainfall and the existence of Rift Valley lakes and rivers. Overall however, the graben is poor in ground water resources due to absence of true aquifers. Most of the under lying rocks are basement complex which by nature do not contain good  aquifers. However, limited ground water reserves occur in rock fissures and localized aquifers.  Ground water is harnessed in many areas, largely to provide for water needs of local communities. Evidence from many boreholes and shallow wells indicate relatively high water table conditions in many places. Such conditions imply high sensitivity of the water resources to oil exploration and development activities, including potential for serious problems of pollution of the shallow aquifers.