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Climate, dams and data in Tanzania


Beth Mackay


April 4, 2017


Declan Conway, UMFULA Principal Investigator, looks at the increasing pressure climate change is having on Tanzania’s supply and demand for water.  Increasing demands on water for agriculture and hydropower generation are under additional pressure from climate change. Monitoring water levels at Tanzania’s largest artificial reservoir, Mtera dam, is essential for the Rufiji Basin Water Office to manage supply and demand for water resources. A high proportion of Tanzania’s grid-based electricity comes from hydropower. Water flows to generate this power are very sensitive. Within the last 20 years water levels have been both too low and too high to enable hydropower generation. The reservoir level fell too low to allow hydropower generation in 2003 and more recently in 2013-14, meaning that Tanzania’s Electricity Supply Company (TANESCO) was forced to turn to a private sector provider for more expensive replacement power. This is in contrast to 1997/98 and 2006, when major flooding across East Africa and Tanzania required spillage to avoid the dam overtopping. Keeping track of reservoir levels is thus critical and requires careful attention. UMFULA is consulting with the Rufiji Basin Water Office (RBWO) to investigate potential impacts of climate change on future water resources. As part of a recent additional piece of work commissioned through the FCFA programme the UMFULA team held a small meeting with the RBWO to discuss the design and preliminary results of a brief being prepared to introduce the potentially bewildering array of climate model results available for Tanzania, and elsewhere.       During a recent field trip, UMFULA PhD student from Sokoine University of Agriculture and I were joined by a staff member for one of their regular monitoring trips to download automated data collected at the dam on reservoir levels and water temperature – now a four hour round trip, thanks to a new road; this journey used to take days. At the time of our visit in late March 2017 the rainy season was ongoing. After a slightly late start, signs were that the season would be reasonable, but the reservoir was still in filling mode and quite low for thistime of year. TANESCO, Tanzania’s Electric Supply Company, manages the site due to its role in electricity production, but it maintains regular interactions with the RBWO which has responsibility for monitoring river flows upstream. Mtera dam releases have to be coordinated with another hydropower plant further downstream (Kidatu) which has much less storage but larger turbines able to generate more electricity. There is ongoing concern that electricity generation from Mtera and Kidatu may be affected by water abstraction upstream.  During our meetings we discussed the interest in information about future climate change in the region that may inform their operations. There was interest in publicly available rainfall data sets which have recently come online and could provide a means for the office to fill in areas where there are very sparse observations (the Rufiji basin covers 20% of Tanzania’s area and is bigger than Bangladesh). Data from a NASA-supported satellite that can monitor water levels for relatively large open water bodies was also of interest. Our meetings with the RBWO are providing a way to link UMFULA research as effectively as possible with operational and management priorities in the basin. Accompanying staff on field work gives insights into their day-to-day tasks and the challenges they face such as inaccessibility of monitoring sites, travel logistics and problems with maintenance. Identifying opportunities for UMFULA to provide information will support the management of water resources under climate change in Tanzania.