Umvoti Vlei lies 11 km due south of Greytown and forms the headwaters of the Umvoti River. The terrain is almost flat, located at an altitude of 970 m a.s.l. The wetland owes its existence to a sill of tough sandstone that has prevented the Umvoti River from cutting downward. The climate is warm-temperate, with an average temperature of 17 °C. Rainfall averages 882 mm p.a., falling mostly in summer. There is some open water at the lower end of the vlei, where clay soils impede drainage. However, the major part of the site, where the soils are alluvial, is a dense, tall, permanently flooded bed of Phragmites australis reeds. Sedge meadows form narrow fringes in places, with bulrushes occurring in patches in the side-arms of the vlei. The surrounding grassland once held Ngongoni Veld, which disappeared due to constant grazing by cattle. Much land has been converted to maize and timber.
The wetland areas are good for Wattled Crane Bugeranus carunculatus and Grey Crowned Crane Balearica regulorum, which winter here in large numbers. The wetland also holds a small population of African Marsh Harrier Circus ranivorus. The surrounding grassland supports several threatened grassland species, including Southern Bald Ibis Geronticus calvus, Blue Crane Anthropoides paradiseus, Secretarybird Sagittarius serpentarius, Denham's Bustard Neotis denhami, African Grass Owl Tyto capensis and Black Harrier Circus maurus. The open grasslands also hold good numbers of Black-winged Lapwing Vanellus melanopterus. The site may have a small amount of suitable habitat for Striped Crake Aenigmatolimnas marginalis, and is suspected to hold several pairs of Eurasian Bittern Botaurus stellaris. The Carex beds have good potential for White-winged Flufftail Sarothrura ayresi.
Globally threatened species are Southern Bald Ibis (flocks of up to 60 birds have been recorded), Wattled Crane (4–6 breeding pairs and up to 15 individuals), Blue Crane (two breeding pairs and flocks of up to 40 individuals) and Grey Crowned Crane (4–5 breeding pairs and roosts of up to 200 individuals). Regionally threatened species are African Marsh Harrier and African Grass Owl.
Two Red Data mammals, serval Felis serval and oribi Ourebia ourebi, occur in the reserve.
Of the greater Umvoti Vlei (2 800 ha), only about a quarter (675 ha) is permanent wetland and less than half of this falls within a proclaimed reserve. So the fortunes of the reserve, in particular water levels and fire regime, are linked to those of the whole vlei. The vlei has a long history of abuse. The first drains were cut in 1918. In 1949, the Lion Match Company, one of the major landowners, excavated a large canal that lowered the water table by 30–90 cm. Only 32 ha of land suitable for poplar planting were so created. Public outcry prompted the Ministry of Agriculture to expropriate the affected land in 1950. Attempts to build barriers across the canals were generally unsuccessful, and uncoordinated fires were especially damaging. In dry years the peaty soils catch fire, making fire-break creation almost impossible. Restoration of the damaged area was proving so difficult that in 1975 the expropriated lot was given to EKZNW (formerly the Natal Parks Board) and proclaimed a nature reserve.
Since then all the artificial drains have been blocked with clay-filled bags, raising the water table by up to 30 cm. In an attempt to improve habitat diversity, some of the Phragmites reedbeds have been removed in order to create more open water. Once the reeds have been taken out, fire and a higher water table prevent re-colonisation. The main threats now to Umvoti Vlei are land-use practices in the catchment. Both forestry and crop farming – which require much irrigation – must lessen the flow of water into the vlei. The vlei has a gradient of 0.15%, the ideal for maximising silt entrapment and flood reduction; its functioning is considered essential for the well-being of the whole Umvoti River system. The Umvoti Vlei Nature Reserve is not actively managed by EKZNW and staff seldom visit it.
Aerial counts of cranes are undertaken in the area each year by EKZNW and EWT. Since 1998 the Wattled Crane population in the IBA has improved from a regular visitor (no breeding pairs were known in 1998) to six breeding pairs recorded during the 2014 survey. This is a significant increase in breeding pairs, elevating the importance of this wetland in KwaZulu-Natal. It highlights the possibility for the species to re-colonise other suitable wetlands.
Taylor PB. 1997a. The status and conservation of rallids in South Africa: results of a wetland survey in 1995/96. ADU Research Report No. 23. Cape Town: Avian Demography Unit, University of Cape Town.
Taylor PB. 1997b. South African palustrine wetlands: the results of a survey in summer 1995/96. ADU Research Report No. 24. Cape Town: Avian Demography Unit, University of Cape Town.