Towards an ecohydrology-based restoration of the Usangu wetlands and the Great Ruaha River, Tanzania

Wetlands Ecology and Management (Impact Factor: 1.27). 01/2006;


An open channel flow model, calibrated against field data, suggests that cattle intrusion in the eastern Usangu wetlands, as well as both dry and wet weather irrigation upstream, are responsible for the seasonal drying out of the Great Ruaha River (GRR) downstream. This human-induced change has severe socio-economic implications downstream, including hindering hydroelectricity production, as well as a devas-tating impact on the Ruaha National Park (RNP) ecosystem that is now shifting from wet tropics to dry tropics. To ensure sustainable development, governance is urgently needed for the Usangu catchment in a way that is compatible with ecohydrology principles for the sustainable use of water resources. In order to do that, perennial flow must be restored to the GRR. For this to happen this study suggests that all the livestock must be removed from the eastern Usangu wetlands and dry weather irrigators must return at least 25% ($4 m 3 s)1) of the water to the river.

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    • "hen the study was conducted during 2011 , 2012 and 2013 . Sources of surface water The GRR ( Fig . 1 ) is the main permanent water source for wildlife in the Ruaha NP . Large - scale human utilisation of water upstream of the Ruaha NP , particularly for agricultural irrigation since 1993 , has significantly reduced its flow during the dry season ( Mtahiko et al . , 2006 ) ."

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    • "In the Ihefu, the increase in cattle has led to degradation of soil and vegetation and many mammalian wildlife populations have decreased significantly as a consequence of increased human activity (Mtahiko et al. 2006). Despite the lack of statistical significance, lower wet season flows in the Great Ruaha River (see section, The Study Area) have reduced inundation upstream of the Nyaluhanga restriction, and consequently the western wetlands are now experiencing far fewer periods of inundation (Mtahiko et al. 2006). Analyses of satellite images indicated significant changes in land cover in the catchment and seasonal and inter-annual variation in the area of the Ihefu swamp (Box 1). "
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    ABSTRACT: "In the face of growing water stress and increasing concerns over the sustainability of water use, Tanzania has, in common with many other countries in Africa, focused largely on the development of more integrated catchment-wide approaches to water management. In the Great Ruaha River Basin, considerable effort has gone into increasing water productivity and the promotion of mechanisms for more efficient allocation of water resources. Over a period of five years, the RIPARWIN project investigated water management in the basin and evaluated the effectiveness of some of the mechanisms that have been introduced. The study findings are relevant to basins in developing countries where there is competition for water and irrigation is one of the main uses."
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    • "For example, in the Ruaha National Park in Tanzania, water diversion for irrigation removed much of the water available for wildlife in particular during the dry seasons (Mtahiko et al. 2006). This resulted in massive disruption to wildlife, including over-population of hippos and crocodiles in the remaining small water holes in the dry season, increased mortality of fish and mammals, overgrazing and erosion of surrounding lands, and disruption to dry-season wildlife migration patterns (Mtahiko et al. 2006). Similarly in Lake Manyara water level decreases annually and is associated with hyper eutrophication which favors development of phytoplanktons in particular cyanobacteria (Lugomela et al. 2006). "
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    ABSTRACT: Understanding local people's socio-economic values of wetlands and traditional mechanisms of managing natural resources forms the basis of conserving them. Wetlands have frequently been developed for short-term economic gains that destroy their ecological values and environmental services in the long term. A study was carried out to assess socio-economic values of the wetland resources, environmental threats around Lake Manyara and local community awareness on causes of environmental changes, degradation in the wetlands and their effects using 80 respondents. Field surveys, interviews, questionnaires and direct observation were used in data collection. It was found that local community was aware on the ecosystem services accrued from the wetlands which were unsustainably used. However, environmental degradation due to unsustainable agriculture, overgrazing, deforestation, urbanization and mining was rampant which had resulted to soil erosion, reduced water availability, wildlife mortality and frequent dry up of Lake Manyara and rivers. In order to protect the lake basin; controlled human activities, land use and water resources within the catchment are to be done in cooperation between the government departments, local authorities and the general local community around.
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