There are no surface rivers here and the lake has no inlet or outlet. Lake levels are tied to rainfall, along with some underground flow from aquifers located further inland. There is a network of groundwater that surfaces at the foot of the Mahfaly Plateau, with three permanent springs (Mande, Andranonaomby and Manava) and numerous seeps and intermittent springs. Lake levels rise with sufficient rainfall, and drop when water evaporates faster than it is being replenished. Vegetation Emergent plant species able to grow in the sodic water include southern cattail (Typha domingensis) and flat-sedge (Cyperus spp.). Glasswort (Salicornia pachystachya) is one of the few species that can tolerate extreme salinity, so it is usually found alone on highly saline sites. Other salt-tolerant species move onto the flats as the water levels recede including Salsola littoralis, Atripex perrieri, as well as some grasses (Sporobolus virginicus, Paspalum vaginatum) and the golden leather fern (Acrostichum aureum). The introduced species beach sheoak (Casuarina equisetifolia) can be found in small stands along the east shore. Aquatic Fauna High phosphate concentrations, originating from erosion, are thought to be the main factor limiting the diversity of aquatic fauna. There are no fish. Invertebrates belonging to four taxonomic groups (Annelida, Gastropoda, Crustacea and Insecta) have been documented. Taxonomic richness was at its highest (15 taxa) in April (rainy season) and decreased to 11 taxa in August (dry season). The eastern part of the lake had consistently more species then the western part, probably because of the consistently lower salt concentrations. The crustaceans were the most widespread species. The aquatic fauna documented in Lake Tsimanampetsotsa is as follows: Annelida (ringed or segmented worms), family Glossiphoniidae (freshwater jawless leeches). Gastropoda species (snails and slugs): Planorbis planorbis (Planorbidae) (ram's horn snails), Georissa petiti (Hydrocanidae) and Potamopyrgus sp. (Hydrobiidae) (mud snails). Crustacea species (crustaceans): Grandidierella mahafalensis (Aoridae) and Halmyrapseudes thaumastocheles (Apseudidae). Insects found included: flies (Diptera); beetles, including nymph of the Dytiscidae (diving beetles) and adults of the Hydroptilidae and Elmidae families; mayflies (Ephemeroptera); bugs (Hemiptera) from 3 families (Naucoridae, Veliidae and Notonectidae); dragonflies of the Libellulidae family and damselflies of the Coenagrionidae family. Birds More than 34 bird species are recorded from the lake area. Greater flamingos (Phoenicopterus roseus) are at times present in large numbers and nest on the lake. Lesser flamingos (Phoenicopterus minor) have also been seen here. The lake and saline flats constitute an important habitat for many