Pangani - Climate change modelling for the Pangani Basin to support the IWRM planning process

The report describes the best possible climate scenarios for the middle of the 21st century for the Pangani Basin, utilising a range of General Circulation Models (GCMs) and a state of the art statistical downscaling procedure. This should enhance understanding on the implications of future climate change on the water resources of the Basin for pragmatic planning.

The Pangani River Basin in north-eastern Tanzania (with about 5% of its area in southern Kenya) drains the southern and eastern sides of Africa’s highest peak, Mt. Kilimanjaro (5,985 m), then passes through the arid Maasai Steppe, draining the Pare and Usambara Mountain Ranges before reaching the coastal town of Pangani, marking its estuary with the Indian Ocean.

The basin supports the rapidly-expanding economic centres of Arusha and Moshi. Most of the Basin’s 3.7 million people rely, either directly or indirectly, on agriculture for their livelihoods. Irrigated agriculture in the basin (estimated at 30,000 to 40,000 ha) is a significant contributor to Tanzania’s food security and supports almost 3 million livelihoods. The basin also includes four hydroelectric power facilities with a combined production capacity of about 17% of Tanzania’s national power grid capacity, although these facilities seldom generate electricity at full capacity due to water stress.

Pangani is already a water-stressed basin (defined as < 1200 m3 of water per person per year) and climate change is expected to greatly exacerbate this condition.

Tanzania’s Initial National Communication (INC) predicts a 1.8°C to 3.6°C temperature increase, decreasing rainfall, and increased evaporation in the Pangani Basin, which together are expected to result in a 6-10% decrease in annual flows. River flows have already reduced to the point that seawater intrudes approximately 20 km upstream from the estuary.

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