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(ii) Considerable debate surrounds the water allocation required for the
environment. A useful synopsis of some relevant issues can be
found in the following: Walmsley. R.D. and Davies. B.R., 1991. An
overview of water for environmental management, Water SA.
VOL 17(1). p. 67 - 76. (The paper discusses inter alia the Pongolo
Floodplain and pans). See also Walmsley. J.J.• 1995. Market forces
and the management of water for the environment, Water SA. VOL
21(1), p. 43 - 50.
10.11 Sources of hydrological data
The Department of Water Affairs and Forestry. Private Bag X313. Pretoria. 0001, has
runoff and other data for over 800 river gauging stations, as well as data for approximately
180 reservoirs and several lakes in South Africa*. When data are requested. the
numbers of the required stations must be quoted (discussed later in the chapter). Failing
that, the name of the nearest town. the name of the river/dam and the latitude and
longitude co-ordinates of the site or area in question. should be provided. The data are in
the form of computer print-outs. photocopies. floppy diskettes and magnetic tapes. (The
latter two items must be supplied if such a data format is needed).
The streamflow data available in the Hydrological Information System (HIS) database
include minimum and maximum daily flow; monthly flow; the monthly maximum flow
peak, and the number of days per month that daily flow equalled or exceeded given values.
Flow is also measured in canals and pipelines. Other data include reservoirllake levels.
inflows and volumes; station/catchment descriptions and inventories; plus weir design and
calibration information, as well as water quality and climatological data (the latter
discussed elsewhere in this volume). The publication, Anonymous. 1988. Availability of
hydrological data. Hydrological Information Publication No. 14, Directorate of Hydrology.
Department of Water Affairs, Pretoria. 11 p. + app.• should be consulted for further
information**. Two important references are Middleton. Lorentz. Pitman and Midgley
*
**
Sometimes referred to as the National River Gauging Network.
See also Zietsman, D.P. and Schutte, J.M., 1981. The availability of quantitative and qualitative
hydrological data. In: Hattingh, W.H.J. (ed). Water Year + 10 and Then?, Technical Report No.
TA 114. Department of Water Affairs, ForestrY and Environmental Conservation. Pretoria.
p.156-217.