Tanzania: Critical analysis of river basin management in the Great Ruaha

This case study describes different responses to growing water scarcity in the dry season in the Usangu Plains, a catchment of the Great Ruaha River in South-West Tanzania. The Great Ruaha River is of national importance in terms of the utilisation of its water for significant rice production, maintaining a RAMSAR wetland site, meeting the ecological needs of the Ruaha National Park and the generation of hydro-electric power.

The background to the issues is best described via the rationale for the project “Sustainable Management of the Usangu Wetland and its Catchment” (SMUWC) which resulted from national and local concerns about the management of water and other natural resources in the Usangu Basin in Southern Tanzania.. In particular, national power shortages in the mid nineties were attributed to low flows to the Mtera/Kidatu hydropower schemes from the Ruaha River. A reduction in low flows in the Great Ruaha, where it passes through the Ruaha National Park, was also noted. There has now been a succession of years in which the river in the park has dried up completely during the dry season, and for increasing periods. An increase in competition for water was noted in Usangu itself, leading to conflict and sometimes violence. Concern was also expressed that the wetlands in the project area were diminishing and were becoming degraded, and that a valuable natural asset was being lost.

The Usangu Basin, or Upper Ruaha Basin, covers an area of 21,500 km2 and forms the headwaters of the Great Ruaha River, itself forming a major sub-basin of the Rufiji River. Usangu may be broadly divided into the central plain and a surrounding higher catchment. On average, the plain receives 600-800 mm annual rainfall, and the high catchment up to 1500 mm. Most of the rain falls in one season from mid-November to May. Six water users are differentiated:

Rainfed farmers and domestic water users in the high catchment;
Irrigators in the plains at the base of the escarpment;
Domestic users and rainfed maize cultivators in the plains;
Pastoralists and fishermen and women in the central wetland;
Wildlife and tourists in the Ruaha National Park that surrounds the riverine reach;
The Mtera/Kidatu hydropower schemes.

The analysis – based on results of two DFID (Department for International Development) projects, SMUWC (Sustainable Management of the Usangu Wetlands and its Catchment) and RIPARWIN (Raising Irrigation Productivity and Releasing Water for Intersectoral Needs) – incorporates a critical examination of the appropriateness of newly established river basin management structures to the problems and issues found.

1. Contested Water Resources Assessment: SMUWC and the Ministry of Water and Livestock developed a hydrological model and a monitoring programme that suggested multiple causes of the changes in the Ruaha and wetland flow regimes. These assessments challenged the original assumptions that the wetland shrinking and the zero flows in the Ruaha were mainly due to overgrazing and excessive consumption of water by livestock and a reduced ability of the wetland to act as a ‘sponge’ holding back water for later release into the Ruaha. The studies also refuted the strongly held belief that climate change and deforestation had caused a reduction in the baseflows of rivers flowing off the escarpment.
2. Contested Water Allocations: The Rufiji Basin Water Office has been charged with the introduction of water allocations and fees at all irrigation intakes on the Plains and has records of approximately 300 irrigation users. These allocations are flow rate based (e.g. 0.6 cumecs), and focus on wet season rice – though allocations are generally halved for the dry season. While the water allocations promoted widely by the RBWO appear elegant (a simple flow rate) and may have worked in other countries, they may not be appropriate in Usangu.
3. Contested Intake Structures The pursuance of an irrigation intake upgrading programme by the World Bank project utilizing irrigation-focussed engineering procedures is another case of mixed and unintended outcomes. Whilst this is supposed to raise irrigation efficiency, under close examination, the provision of concrete weirs and intake works shows that reliance on intakes alone does not, and cannot, raise irrigation efficiency to the levels expected by RBMSIIP.

A key conclusion is that managers of IWRM should continuously review and enrich the knowledge base, perceptions and processes of hydrological and system change in river basins with the aim of refining ‘an appropriate institutional response’.

In other words, we should not be satisfied with what appears to be an integrated water resources management approach, but critically unpack its components and identify modes of IWRM that are fully cognisant of the science, issues and responses at stake, and therefore deliver effective tailored solutions.