Volume II - The Northern Cape Provincial Spatial Development ...

Northern Cape PSDF
Volume 2
December 2011
is anticipated that the planning, surveying, design, and the South Africa‐Namibia
negotiations will delay construction until 2014‐2018. An investigation of the potential of a
dam at Aspoort in the Doring subarea of Olifants/Doorn WMA was undertaken by Northern
Cape in the 1990s. The study indicated that a dam would have the potential for irrigation
developments on a large scale. The Northern Cape Department of Agriculture originally
proposed to undertake a pilot scheme to verify some of the assumptions used in the Aspoort
Scheme proposal. However, this has not yet been undertaken. The Western Cape also
investigated the Melkboom and Melkbosrug dams and a development cap was put in place
for a period of seven years, up to end 2005, to ensure that ad hoc development did not
preclude the development of any schemes by the Northern Cape.
C.2.8 WATER QUALITY
C.2.8.1 THE LOWER VAAL
The land use in the Lower Vaal WMA is primarily livestock farming, with some dry land
cultivation in the northeast. Intensive irrigation is practiced at Vaalharts. Diamond‐bearing
intrusions near Kimberley and alluvial diamonds are found near Bloemhof. Iron ore and
other minerals are found in the south‐eastern parts of the Lower Vaal WMA. The
development in the Upper and Middle Vaal WMAs has led to the deterioration in the water
quality of the water resources in the system, with salinisation and eutrophication being the
two major water quality problems being experienced.
Salination has either a natural or an anthropogenic cause. Although the origin of natural
salination of river water is geological, human activities are associated with increased
releases of salts, particularly at point sources of pollution, such as poorly managed urban
settlements and mining residues. Water quality studies have found that levels of dissolved
salts are high in the Lower Vaal downstream of the Harts River confluence. Irrigation along
the lower Vaal River to Douglas causes concentration of salts. The Modder and Riet River
irrigation schemes consume large amounts of fresh water and raise salinity levels in the
depleted river flow to high levels, further adding to the pollution of the lower Vaal River at
Douglas Barrage. Water quality can have a significant effect on crop production. All irrigation
water contains dissolved mineral salts, but the concentration and composition of the
dissolved salts vary according to the source of the water. Very high salt levels can reduce and
even stop crop growth. Other reasons for high levels of salinity are related to mining
activities.
Eutrophication is the enrichment of water with plant nutrients nitrate and phosphates,
which encourages the growth of algae. The algae cause problems in water purification. The
sources of the nutrients include irrigation return flows, urban runoff, industrial discharges
and wastewater treatment works discharges. Water quality studies have found that there is
also excessive growth of water hyacinth. Eutrophication has negative economic implications
for water users. Water boards in the Middle Vaal have been forced to upgrade their water
treatment works to treat odour and colour associated with the eutrophication. Further
impacts include alteration of the ecology of the river systems, the clogging of irrigation
equipment, and being unable to use river systems for recreational purposes. The regulation
of the Vaal River has resulted in a reduction in baseflows and flow variations in the river. The
Office of the Premier &
Department of Rural Development & Land Reform
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Dennis Moss Partnership