Great Fish River

from Wikipedia, the free encyclopedia
Great Fish River
Groot-Visrivier
The Great Fish River at the Double Drift Nature Reserve

The Great Fish River at the Double Drift Nature Reserve

Data
location South AfricaSouth Africa South Africa Eastern Cape
Province
River system Great Fish River
source in the northern part of the Bamboesberg massif and in the eastern part of the Sneeuberg massif (Snow Mountains)
muzzle Indian Ocean Coordinates: 33 ° 29 ′ 39 ″  S , 27 ° 8 ′ 1 ″  E 33 ° 29 ′ 39 ″  S , 27 ° 8 ′ 1 ″  E
Mouth height m

length 730 km
Catchment area 30,366 km²
Discharge at the Outspan gauge (1160580)
A Eo : 29,745 km²
Location: 145 km above the mouth
NNQ
MNQ 1969–1986
MQ 1969–1986
Mq 1969–1986
MHQ 1969–1986
HHQ (max. Month Ø)
0 l / s
4.1 m³ / s
8 m³ / s
0.3 l / (s km²)
16.2 m³ / s
121 m³ / s

The Great Fish River ( Afrikaans Groot-Visrivier , German Great Fish River ; formerly Great Salt River ) is a river in the South African province of Eastern Cape . It is about 730 kilometers long and has a catchment area of 30,366 square kilometers. The river, together with the Sundays River to the west of it, drains the eastern parts of the semi-arid Karoo . Major tributaries are the Kariega River , Kat River , Little Fish River , Koonaprivier, and the Tarka River .

course

The headwaters of its upper tributaries are in the northwestern section of the Eastern Cape Province, in the wider area of ​​the city of Middelburg . The sources are located in the northern part of the Bamboesberg massif and in the eastern part of the Sneeuberg massif (Snow Mountains). The course of the river stretches south of Middelburg through the small town of Visrivier to Cradock and further to the area east of Somerset East , from where its right tributary approaches the Little Fish River and flows into the Great Fish River in the landscape between Sheldon and Carlisle Bridge . From around this point on, its turns increase significantly and the valley cuts deeper into the landscape. Further downstream, it takes in the Koonaprivier with its tributaries from the Winter Mountains area and the Kat River, which brings its water from the Katberg and Elandsberg area.

In the lower reaches, the river bed meanders very strongly and cuts deeply into the hill country of the Makhanda region . Its mouth is in Waterloo Bay east of Port Alfred at Fort D 'Acre on the coast of the Indian Ocean. There its valley widens and the mouth is shaped by a mighty sandbank. The regional road R72 crosses the valley here with a bridge.

Geological situation

Its upper course and the most important tributaries lie in the area of ​​the eastern Great Karoo, the geological structure of which is determined by sandstones and other sedimentary rocks of the Beaufort group . In the area of ​​the Great Fish River Nature Reserve, it is mainly sandstones of the Middleton Formation (Beaufort Group) that shape the geological structure of the riparian zones. Further downstream, its course crosses the narrow sandstone zone of the Ecca group north of Makhanda and has contact with tillites of the Dwyka group before penetrating further south into older rock strata. Now the Great Fish River reaches the folding zone of the Cape Supergroup . It is mainly rocks (slate) from the Witteberg group ( Devonian ). Its mouth area lies in the area of ​​this folding zone.

From its upper reaches near Middelburg to north of Makhanda, the Great Fish River flows through a basin-like landscape. This area is called the Great Fish River Basin ( Fish River Basin called). It is a flat to flat undulating landscape with an area of ​​about 25,000 square kilometers. The basin is characterized by low annual rainfall (350–450 mm). Swellable clay minerals in the soil, such as montmorillonite , absorb a considerable part of the surface water, bind it for a long time and gradually release it back into the atmosphere in the form of water vapor. This process favors the semi-arid climate in the Great Fish River Basin because only small amounts of water are absorbed into the aquifer (mostly sandstones here). This process is known as evapotranspiration .

Typical alluvial deposits on the undulating relief of the Fish River basin are clayey loam soils .

Hydrometry

The flow rate of the river was measured for 17 years (1969–1986) in Outspan, 145 km above the mouth in m³ / s. It should be noted that the river can dry up at any time of the year.

history

Between 1779 and 1853, the banks of the Great Fish River were the scene of border wars between European settlers and Native African people. Even then, the distribution of scarce water supplies was a key issue of conflict. Water distribution is currently the responsibility of the administration of the Water User's Association and its 17 regional Water Control Officers. Some of the water has been supplied via the Orange-Fish River Tunnel since 1975 .

Water reservoirs in the catchment area

In the catchment area of ​​the Great Fish River there are five large water reservoirs that are used to supply their regions with water.

  • Grassridge Dam (on Groot Brak)
  • Kat River Dam (on the Kat River)
  • Command Drif Dam (on the Tarka River)
  • Lake Arthur (on the Tarka River)
  • Ncora Dam (on the Tsomo River)

Conservation reserves on the Great Fish River

Part of the river has been declared a Great Fish River Reserve because of its scenic and ecological features as well as its biodiversity .

This nature reserve with an area of ​​45,000 hectares consists of three individual reserve areas. These are:

  • Double Drift Nature Reserve
  • Andries Vosloo Kudu Reserve
  • Sam Knott Nature Reserve

This nature reserve is cut through by the regional road R345 and can be reached from the villages of Alice in the north and Peddie in the south. The regional road R67 runs past its western edge.

Types of use in the catchment area

The majority of its catchment area, 94 percent, are natural areas that have been subject to little or no anthropogenic change and use. It is the dry steppe and bushland of the Great Karoo with mostly very little urban use. Only 3 percent of the area is used as agricultural land and an equal proportion is considered to be degraded landscape that is affected by erosion phenomena. Built-up areas make up less than 1 percent of the catchment area, although they include the towns of Adelaide , Bedford , Cradock, Fort Beaufort , Middleburg and Somerset East. The reason for this usage structure is the specific geological and climatic conditions of this Karoo region.

The development of economic activities is difficult because of these prerequisites and, in view of the sensitive ecological conditions, only possible to a limited extent and not desirable everywhere. Historically, it is traditional farmland, but it is only used to a limited extent for this purpose. Today, public and private activities are endeavoring to promote gentle tourism in the often semi-desert landscape.

The Great Fish River Museum in Cradock shows objects from the history of European settlement on the upper reaches of the Great Fish River.

See also

literature

  • Nick Norman, Gavin Whitefield: Geological Journeys . Cape Town (Struik Publishers) 2006 ISBN 1-77007-062-1
  • EAW Tordiffe, BJV Botha: The Relationship between Macro-Topography and the Groundwater Quality in the Great Fish River Basin, Eastern Cape Province . In: Water SA, Vol. 7. (1981) No. 3., pp. 113 ff.
  • Geological map of South Africa 1: 250.000, Sheet 3226 King William's Town
  • 3226 King William's Town, 1: 250,000, topo-cadastral, Mowbray (Chief Director of Surveys and Mapping Privat Bag Mowbray) 1985

Web links

Commons : Great Fish River  - collection of pictures, videos and audio files

Individual evidence

  1. a b Homepage UNH / GRDC - The Great Fish River in Outspan. Retrieved July 2, 2020
  2. ^ Water Institute of Southern Africa: GREAT FISH RIVER. on www.ewisa.co.za ( Memento of the original from August 15, 2011 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice.  @1@ 2Template: Webachiv / IABot / www.ewisa.co.za
  3. GREAT FISH RIVER: Topography, geology and soils. on www.ewater.co.za ( Memento from January 18, 2015 in the Internet Archive )
  4. Department of Water Affairs: Eastern Cape provincial water sector plan 2007/08 to 2011/12, p. 20 ff. At www.dwaf.gov.za (PDF; 749 kB)
  5. Water Control Ensures Great Fish River Valley Remains Land of Milk and Honey ( Memento of the original from October 27, 2011 in the Internet Archive ) Info: The archive link was automatically inserted and not yet checked. Please check the original and archive link according to the instructions and then remove this notice. (PDF; 186 kB) @1@ 2Template: Webachiv / IABot / www.wrc.org.za