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United Republic of Tanzania
The United Republic of Tanzania has nine major drainage basins that are the basis for water resources management through nine corresponding basin water boards (MWI, 2009):
River discharge and lake levels start rising in November-December and generally reach their maximum in March-April with a recession period from May to October/November. Many of the larger rivers have flood plains, which extend far inland with grassy marshes, flooded forests and ox-bow lakes.
The lakes and swamps cover 5.4 million hectares and comprise 5.8 percent of the country (SEI, 2007), in particular Lake Victoria, Lake Tanganyika and Lake Nyasa (Tanzanian name for Lake Malawi), which also form the border to neighbouring countries (Table 4). Other lakes include Lake Rukwa, Lake Eyasi, Lake Manyara, Lake Natron, Lake Balangida.
Internal renewable surface water resources are estimated at 80 000 million m³/year and renewable groundwater resources at around 30 000 million m³/year, but 4 000 million m³/year is considered to be overlap between surface water and groundwater, which gives a value of total internal renewable water resources (IRWR) of 84 000 million m³/year (Table 3). External renewable water resources are estimated at 12 270 million m³/year, which is the inflow from the Kanyaru river from Rwanda (4 670 million m³/year) contributing to the Kagera river, and from the Kagera river from Burundi (7.6 million m³/year). Surface water leaving the country is estimated at 15 640 million m³/year through Lake Victoria to Uganda (10 700 million m³/year), through the Kagera border river to Rwanda (7 600/2 = 3 800 million m³/year), through Lake Malawi to Malawi (140 million m³/year) and through Lake Tanganyika to the Democratic Republic of the Congo (1 000 million m³/year). The dependency ratio is around 13 percent and the total renewable water resources are 96 270 million m³/year, or 1 800 m³/year per capita in 2015.
There are 633 dams (MWI, 2009) and the total capacity of large dams is almost 104 200 million m³. This includes 100 000 million m³ which is considered to be the Tanzanian part of the additional storage capacity created in Lake Victoria (shared with Kenya and Uganda) through the construction of the Owen Falls dam at the outlet of Lake Victoria in Uganda. The main dams in the United |Republic of Tanzania are the Mtera, Nyumba ya Mungu, and the Kidatu dams. Leakage, siltation and inappropriate or damaged features are very common: about 21 percent of the 633 dams experience spillage and 12 percent have silted up, requiring hence rehabilitation (MAFSC, 2013). About 90 percent of the country electricity is generated through hydropower from the Great Ruaha and Pangani rivers only (DE, 2006). Small dams are called Charco dams for irrigation, municipal and livestock purposes. Hydrological and topographic conditions largely restrict dam construction in the country, but three major dams are planned: the Farkwa dam in Dodoma; the Lugoda Dam in Iringa; and the Kidunda dam in Morogoro (MW, 2014).
Due to the very low rate of population with access to improved sanitation (16 percent), there is little wastewater collected–47 million m³ in 2012–and even less treated and directly used. Similarly, there is little desalinated water, despite the fact that that would help reduce water shortages especially on the Zanzibar islands.