Change in Water Spread Area due to Sedimentation in Mtera Dam in the Mtera Reservoir in Iringa, Tanzania

Abstract

Mtera reservoirs play an important role in Tanzania's local economy because of their reliance on hydropower. However, human activities have been reported to pose a challenge to its sustainability by altering storage capacity. Hence, the objective of this paper was to assess the change in water spread area due to sedimentation in Mtera Dam in Mtera Reservoir at Iringa, Tanzania using appropriate standard procedures, including remote sensing techniques. Data obtained show that for the period of ten years (2014-2024), the water spread area declined by 226.675 km², which corresponds to a 34.34% decline from 2014 as a baseline. Similarly, the reservoir storage capacity decreased by 1.25 km³, corresponding to a loss of 39.06%. The annual rate of storage capacity and water spread area loss was observed to be 0.125 km³ year⁻¹ and 22.67 km² year⁻¹, respectively. The largest loss was observed in the upstream zones of the reservoir (western and northwestern), where much of the sediment has been deposited. The rate of reduction of storage capacity is higher compared to internationally accepted levels of change. The study concludes that the sedimentation has significantly reduced the storage capacity of the reservoir to the extent that it can affect its functioning, such as hydropower generation. The study recommends emphasizing conservation measures, especially in the upstream zones, and routine monitoring of sediment to improve the functioning and sustainability of Mtera Reservoir.