Hydrological modelling and water assessment in the Nyaluhanga catchment in the south-western part of Tanzania

Start date: 5 September, 2010 End date: 25 November, 2010 Project type: Master's Thesis (prior to 2018) Project code: 10-1-05 and 10-1-54 Countries: Tanzania Institutions: University of Copenhagen (UCPH), Denmark Grant recipient: Christian Rundblad and Theis Knudsen Total grant: 20,000 DKK


Tanzania faces numerous challenges with regards to water resources and water management due to predicted climate changes and increased demographic development. Fully distributed hydrological models, such as MIKE SHE, are effective tools to assess water resources. In this study a MIKE SHE model has been set up, for a catchment in the southwestern part of Tanzania, The main objective is to assess the sustainability of implementing groundwater based irrigation in the area hereby substituting the present river abstraction, which has led to cessation of downstream flow since 1993. The results suggest a sustainable groundwater abstraction rate in the magnitude of 400 mm year-1 within the present irrigation areas. This would however require an adaptation of cultivation strategies implementing less irrigation intensive crops, e.g. maize and onions as substitution for rice. The study does however evaluate that, expansion of the irrigation schemes in response to the population growth to cover the whole of the alluvial fans, would not be sustainable with this rate of pumping. Conjunctive water use, including river abstraction in the wet season and groundwater use in the dry season with a pumping rate in the magnitude of 300 mm year-1 applied on reduced areas, seems to be a sustainable prospect. The study concludes that there is an inadequate degree of water management in terms of water allocation and authorization, although progress has been made in terms of some reduction of unbeneficial water use. Increased funding for administrative institutions is necessary. The surveys conducted in this study showed an increasing willingness to pay water fees. This is due to the common acknowledgement of the scarcity of water and the confidence that the water management institutions will allocate the water resources in a sustainable manner. This coincides with the need for enhanced funding for further policing from Rufiji Basin Water Office (RBWO), which will enable them to enforce the water rights and avoid unauthorized water abstractions.