The reservoir was created in 1975, by damming the Ruaha river close to the main road between Iringa and Dodoma. The storage capacity is 125 million cubic metres, with a maximum surface area of c.660 km² which can be reduced to 200 km² at minimum supply level. The maximum depth is 35 m at the dam with a large area of shallows below 8.5 m. The lake has many (estimated at more than one million) standing dead trees. There are areas of rocky shoreline along the inner basin and a variety of habitats along the remaining water-edge, which can include (much depends upon the fluctuating water-levels) extensive areas of reedmace Typha, reed Phragmites, various short grasses, open mud and bare sand. The surrounding area is dry Commiphora–Acacia woodland, characteristic of the central plateau. Just 3 km north of the dam and east of Dodoma road lies Pakwaya Mbuga, a rain-fed temporary wetland.
See Box for key species. An important fishery has developed attracting large numbers of piscivorous birds. The dead trees provide nest-sites for waterbirds. Bird counts were made in the inner basin during March and April 1994, and in January 1995 a small section of the north-eastern shoreline was surveyed. Large flocks of flamingos have been reported, but no quantitative data is available. In 1994, there were substantial numbers of Phalacrocorax carbo, Anhinga rufa, Ardea cinerea and Haliaeetus vocifer nesting in the dead trees. Many hundreds of thousands of Hirundo rustica roost in these trees. In 1994, after substantial rains, Pakwaya Mbuga covered an area of 600 ha and held breeding concentrations of Dendrocygna viduata and Dendrocygna bicolor (3,000 of each species). Other species breeding at this time were Nettapus auritus, Anas erythrorhyncha, Sarkidiornis melanotos, Plectropterus gambensis, Actophilornis africanus and Chlidonias hybridus.
Non-bird biodiversity: None known to BirdLife International.
BirdLife International (2019) Important Bird Areas factsheet: Mtera reservoir. Downloaded from http://www.birdlife.org on 24/01/2019.