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The Orange River Mouth (ORM) Wetland (16°30'E; 28°35'S) wetland was identified as being of international importance because (Ref. 2):

• It is an example of a rare wetland in its particular biogeographical region.

• It supports an appreciable assemblage of rare, vulnerable or endangered species. Of the 57 wetland bird species recorded, 14 can be considered either to be rare or endangered. The site also supports 33 mammal species (including the Cape clawless otter) and the Namaqua barb, a red data species fish found only in the lower reaches of the Orange River.

• It regularly supports substantial numbers of particular waterfowl, indicative of wetland productivity and diversity.

Agricultural: The area immediately abutting the south of the river is irrigated farmland for supply of produce to the State Alluvial Diggings. Immediately to west of the bridge along the northern bank of the ORM, meadowland is maintained for a stables complex.

Industrial: Diamond mining companies hold a concession to most of this land. The north bank of the Orange River forms the border between SA and Namibia. The border is in the process of being changed, but since Namibia is going to join the Ramsar Convention, this wetland will then be a joint designation.

Urban: Behind the belt of farmland to the South of the ORM, the township of Alexander Bay is situated on the slopes immediately outside the former floodplain area. The closest settlement is that of Alexander Bay (RSA) and Oranjemund (Namibia). Seaward of the meadows along the northern shore of the ORM, the floodplain is under "natural" vegetation on the river side of the dyke, which protects developments near Oranjemund, notably the golf course.

Recreational: Anglers have a choice between fishing in the Orange River or the Atlantic Ocean. The Orange River, especially the section between the Richtersveld and Alexander Bay, is also popular for canoeing expeditions. Various 4x4 trails crisscross this area. Trained guides are available and some companies rent out vehicles.

Aquatic vegetation: The Orange does not have true estuarine communities as the sea hardly enters the river and there are few salt tolerant plants.

Terrestrial Vegetation: The Ramsar site comprises sand banks or channel bars covered with pioneer vegetation, a tidal basin, a narrow floodplain, pans, the river mouth, and a salt-marsh on the south bank of the river mouth.

The wetland vegetation includes wetland marshes, saltmarsh, island and bank vegetation. Wetland marsh vegetation and island and bank vegetation consist mainly of freshwater species.

The major vegetation types recognised include the island communities; dominated by Scirpus littoralis, Phragmites australis and Sporobolus virginicus; the peripheral marshland, dominated by Sarcocornia pillansiae and Sporobolus virginicus; and the Lycium decumbens floodplain vegetation.

Invertebrates: The Orange does not have true estuarine communities as the sea hardly enters the river and there are sand prawns or bivalves that would normally be expected to dwell in the mud flats of estuaries.

Fish: Very little data are available on fish life within this system. From the available data it is evident that freshwater species are predominant in the system. As far as fish life is concerned this system cannot be regarded as an ecologically important system.  A red data fish species (Largemouth Yellowfish ) is found only in the lower reaches of the Orange River (Ref.2).

Birds: The Orange River Mouth is regarded as the sixth most important coastal wetland in southern Africa in terms of the number of waterfowl it supports.  The river mouth, mudflats, intrafluvial marshlands, islets near the mouth and adjacent pans provide a sizeable area of sheltered shallow water suitable for concentrations of wetland birds, which use these habitats for breeding purposes or as a stopover on migration routes. The bird population can be as high as 20 000 to 26 000 individuals. Of the 57 wetland species recorded, 14 are listed as either rare or endangered in one or both of the South African and Namibian Red Data Books.

At times the area supports more than 1 % of the world population of three species endemic to south-western Africa: the Cape cormorant (Phalacrocorax capensis), Damara tern (Sterna balaenarum) and Hartlaub's gull (Larus hartlaubii). On a southern Africa scale the wetland supports more than 1 % of the subcontinental population of blacknecked grebe (Podiceps nigricollis), lesser flamingo (Phoenicopterus minor), chestnut banded plover (Charadrius pallidus), curlew sandpiper (Calidris ferruginea), swift tern (Sterna bergii), and Caspian tern (Hydroprogne caspia).

Mammals: The site also supports 33 mammal species (including the Cape clawless otter) (Ref. 2).

Geology: The "sand-bars" at the mouth of the river are of a particular nature. They differ from those to be found higher up in the stream. The geomorphological agent in the case of the latter is the river itself and the material to be found there consists of sedimentary (river) deposits. In the case of the sandbar that stretches from the mouth of the river to the sea, the geomorphological agent is the sea - more specifically the wave action and the long-shore current.

The ORM-system is situated approximately 1 335 km downstream of the Vander Kloof Dam and 1 155 km downstream of the confluence of the Orange River and Vaal Rivers. Total water losses due to net evaporation from the river between the PK le Roux Dam and the ORM-system are estimated at approximately 14 % of the total inflow to the river below the PK le Roux Dam.

In 1840 according to Hottentot legend the river was in flood for 5 months.  

The oldest record of an Orange River flood is a vivid account by Burchell in 1882. He described the confluence of the Vaal and Orange River as: “a rapid and agitated tide of muddy water, swelled to a terrific height, overwhelming the trees on its bank, and thrown into waves by the force of its own impetuous current”.

Precipitation: Average annual precipitation at the ORM is only 50 mm/yr with an average annual potential evaporation of over 3 000 mm/yr. The sparse rainfall occurs mainly in winter. Single very rare heavy showers can account for as much as the normal annual precipitation. Hail is seldom reported in this region.

Temperature: The highest average maximum temperature (24,42 °C) occurs in January and the lowest average minimum temperature (8,7 °C) occurs in July,

Currently the only disturbance to the ORMW is minor; local recreational use by personnel of the mining organisations and (far) upstream damming of water extraction.

The major threat to this wetland is loss of inflow of water and sediment through human manipulation of water in the Orange River catchment. The two major extant dams on the middle reaches of the Orange River already limit floods in the lower Orange River to events of very large magnitude and also act as traps restricting the quantity of sediment moved downstream of the middle reaches. Development of further dams and diversion of flow in the headwaters as part of the Lesotho Highlands Scheme are likely to further reduce water availability in the ORMW. This scheme will come into effect in the mid 1990's. When fully implemented this scheme will transfer 2 000 x 10 m/yr from the Orange River to the Vaal River system. One result of these water transfer schemes is that less water will be available for release to the Lower Orange River and particularly to the ORMW.