PROCEEDINGS OF THE 3RD INTERNATIONAL CONFERENCE ON ENERGY AND DEVELOPMENT - ENVIRONMENT - BIOMEDICINE
Groundwater use in parts of the Limpopo Basin, South Africa
OLA BUSARI
Trans-Caledon Tunnel Authority (TCTA)
PO Box 10335, Centurion 0046
SOUTH AFRICA
[email protected] http://www.tcta.co.za
Abstract: - Water resources auditing on the South African side of the Limpopo Basin suggests that
groundwater presents the only viable alternative source of cost-effective supply to meet future requirements.
However, while aquifer yields are favourable in places, averaging 16.7 l/sec for main-stem alluvium,
groundwater is already extensively used. Between 1995 and 2002, total groundwater use in the area rose by
almost 40%, increasing from 98 to 136 million m3 per year. In the particular case of commercial irrigation,
over-exploitation of groundwater has been recorded in a number of places, especially in the northwest where
drawdowns of more than 50m have resulted from decades of intense agricultural water use. Although
groundwater use for mining is still low at 4% of total usage, the region is currently witnessing a surge in
mining operations, and a significant growth in water requirements is envisaged for mining development.
Key-Words: - Groundwater, Limpopo Basin, South Africa, Sustainable catchments, Water use
all over the country that have ‘uniform occurrence
characteristics’. Much earlier, Vegter [5] produced a
suite of hydrogeologic maps and summarized
valuable information on the groundwater conditions
in identified geologic formations.
In the upper and middle portions of the Limpopo
water management area, overburden materials and
fractured water-bearing units have served as the sole
sources of irrigation water for commercial
agriculture for more than two decades. In that light,
a number of groundwater studies have been carried
out in those areas by Dziembowski [6], Jolly [7],
Northern Transvaal Cooperative [8], Braune and
Dziembowski [9], Du Toit et al. [10], and
Masiyandima et al. [11]. In particular, Jolly [7]
provides a description of the typical hydrogeologic
setting, identifying two inter-dependent aquifers: a
weathered upper aquifer and a lower fractured unit.
Braune and Dziembowski [9] present an overview of
the regional geology, while Masiyandima et al. [11]
juxtapose new levels of recharge rates and
drawdowns with those previously determined by
Dziembowski [6] and Jolly [7]. In their work in the
northernmost reaches of main-stem alluvium
supporting agricultural communities, Du Toit et al.
[10] map the extent of the deposit and characterize
the local aquifer. This paper examines the use of
groundwater for meeting current and future needs in
the study area, especially as an alternative source of
water supply for domestic needs, smallholder
agriculture and similar productive purposes.
1 Introduction
In South Africa, as well as in each of the other three
riparian states in the Limpopo Basin – Zimbabwe,
Botswana and Mozambique (Fig. 1) – groundwater
is located in a strip of alluvium along the main stem
and in weathered and fractured crystalline basement
complex rocks in tributary catchments. Hitherto, an
orientation towards large-scale water resource
infrastructure on the South African side ensured that
surface water sources received much greater
attention. However, with opportunities for surface
water development almost exhausted, there is a
growing
consensus
that
targeted
aquifer
development is a potential option for sourcing water
to meet diverse and expanding needs, especially of
the vast rural populations.
Aside from consultations with stakeholder
individuals, groups and organisations involved in
groundwater use in the basin, and literature and
information search in previous work and databases,
this paper draws on a recent national intervention.
That initiative relates to the development of internal
strategic perspectives within the Department of
Water Affairs and Forestry, as interim catchment
management strategies prior to the full
establishment of catchment management agencies.
In the case of the Limpopo water management area,
one of nineteen in South Africa, the strategy, DWAF
[2], includes a groundwater component by Hubert
[3]. Significantly, in a preliminary effort to identify
and characterize the groundwater resources in South
Africa in terms of their occurrence, quality and
development potential, Vegter [4] delineated regions
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PROCEEDINGS OF THE 3RD INTERNATIONAL CONFERENCE ON ENERGY AND DEVELOPMENT - ENVIRONMENT - BIOMEDICINE
Figure 1: Location of the study area in the Limpopo Basin: DWAF [1].
2 Geohydrologic characteristics
2.1 Matlabas/Mokolo/Lephalala catchments
The approach adopted here, of tracking the
occurrence of groundwater on the basis of river
catchments, is only for convenience in accordance
with common practice, but also following and
drawing on the presentation of the groundwater
component of the internal strategic perspective for
the region, DWAF [2]. Fact is aquifer configurations
don’t exactly match those of surface water
catchments, a reality that presents considerable
challenges to the holistic and integrated
management of water across traditional catchment
boundaries.
The Limpopo and its tributaries – Nwanedi,
Nzhelele, Sand, Mogalakwena, Lephalala, Mokolo
and Matlabas – form the principal drainage system
(Fig. 1). Most of the rivers in the extensive drainage
system flow predominantly northwards; in practical
terms though, the Limpopo is the only true perennial
river. Due to the absence of permeable waterbearing strata with the capacity to store and then
transmit water to rivers, most of the water-courses
are mainly active during the wet season, flowing
after heavy local rainstorms. But also, in the large
perennial river, the seasonal nature of rainfall
ensures that discharge is highly variable,
underscoring the need to develop groundwater as an
alternative water source.
In the area, four major lithologic units predominate.
Some parts of the region are remote and ranching
and game management are practised. Limited
groundwater
is
available
in
the
sandstone/conglomerate unit, from which boreholes
generally yield 0.5-2l/s, occasionally higher than
3l/s in discontinuities. The depth of boreholes ranges
from 55 to over 200m, with depth to water 20 to
90m. Water quality is considered to be very good,
especially around the recharge zone of the
Waterberg
Mountains.
In
the
Karoo-age
siltstone/sandstone, yields are frequently under
0.5l/s in the siltstone, but may be up to 2.5l/s in
sandstone. Boreholes have been drilled to depths
between 45 and 80m, with water levels ranging from
20-45m. Aquifers of the metamorphic Limpopo
Mobile Belt are expectedly limited to faults, fracture
zones and weathered materials. Yields from
boreholes are usually lower than 0.5l/s, but could be
as high as 2l/s in places. Depth of holes ranges from
35 to 85m and water levels 10-45m. Water quality is
poor in places, indexed by the dissolved solids
content, and nitrate could be anomalous due to
agricultural activities. In a limited norite/gabbro
unit, part of the Bushveld Igneous Complex,
borehole depths range from 40-70m, with static
levels usually 20 to 30m, while yields are generally
0.5-2.5l/s, occasionally getting as high as 5l/s.
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since the 1970s. Dziembowski [6] determined that
the average recharge rate to the aquifer was 3.8% of
the annual rainfall, which falls within the 2-5%
brackets recently given by Masiyandima et al. [11].
2.2 Mogalakwena catchment
Reflecting the complexity of groundwater
occurrence in the area, a number of lithologic units
will be highlighted. The region is home to ranching,
game management and the use of groundwater for
irrigation. In hilly portions underlain by
dolomite/sandstone, boreholes are generally less
than 100m in depth and their yields under 2l/s,
though going over 5l/s in dolomitic zones.
Boreholes penetrating norite/gabbro vary in depth
from 40-70m, with static levels between 20 and
25m, while yields are generally 0.5-2l/s, at times
reaching 5l/s. Granite aquifers, where sufficiently
weathered, could yield over 5l/s, although 0.5-1l/s is
more common. Depth of boreholes is generally 7080m, depth to water 20-30m, and there are reports of
pockets of high nitrate. Boreholes drilled into
coarse-grained sandstone/conglomerate vary in
depth from 50 to 200m, yielding 0.5-2l/s normally
and exceeding 3l/s along fracture zones. Yields from
a basalt unit could be more than 5l/s in structural
features, more frequently in the range 0.5-2.5l/s,
while water levels of 20-30m are recorded in holes
of depth 60-80m. Underlying the basalt in the
Taaibosch Fault zone is a productive Clarens
Sandstone aquifer, with yields exceeding 40l/s for
holes over 200m in depth. At the other extreme,
boreholes drilled into granite/gneiss/schist hardly
exceed 2l/s in yield, usually under 0.5l/s, and depths
are normally less than 80m, with depth to water 2030m.
2.4 Nzhelele/Nwanedi catchments
The area hosts four major lithologic units. Residents
occupying dense communal settlements in upper
portions rely heavily on boreholes drilled into coarse
sandstone where structural features yield over 3l/s,
although yields lower than 0.5l/s are more common;
borehole depth is in the range 50-150m and water
level 20-50m. Yields less than 0.5l/s are also the
norm in the southwest-northeast trending karoo
sandstone, with depth to water 20-30m in boreholes
of depth 40-70m. In the easternmost portions, a
basalt aquifer feeds human settlements and intensive
agriculture with over 5l/s from structural features
and deeply weathered overburden, although 0.5-2l/s
is more common. Depth to water is 15-25m in
boreholes ranging in depth from 65-85m. Up north,
home to game management and livestock farming,
the underlying granite/gneiss/schist usually yields
below 0.5l/s, though ranging up to 2l/s in weathered
zones, faults and fractures. Depth to water varies
from 20 to 30m in holes of depths 40-70m.
2.5 Limpopo main stem
In the southwest, downstream of the confluence of
the Crocodile and Marico rivers, the Limpopo River
is narrow and cuts into the granite-gneiss-schist of
the Limpopo Mobile Belt. Alluvial deposits are
generally less than 3m, and boreholes varying in
depth from 15 to 25m only yield 1-2.5l/s. Further
north around the confluence of River Shasi with the
Limpopo, alluvial thickness goes up to 25m,
enhancing aquifer potential. At the northern
extremes, in the Pontdrift-Weipe area hosting a large
farming community reliant on groundwater for
extensive irrigation, yields of up to 30l/s are
recorded from holes of depth 15-25m. In a study of
about 400 boreholes penetrating main-stem alluvial
aquifer in the area, Du Toit et al. [10] estimated an
average yield of 16.7l/s. Also, the thickness of the
alluvial deposit was reported to be 6m on the
average, although reaching a high 24m in places.
2.3 Sand catchment
Four main lithologic units underlie the area. Down
south, granitic rocks are deeply weathered and
frequently yield over 5l/s. Irrigated agriculture
accounts for high nitrate in places. In contrast, to the
west,
holes
penetrating
coarse-grained
sandstone/conglomerate only yield below 0.5l/s,
although over 3l/s along faults and fractures zones,
even at depths close to 150m. Although yields from
the Karoo basalt are normally less than 2l/s, they
exceed 5l/s in structural features; water levels range
from 15-25m in holes of depth 60-80m. Borehole
depths in granite/gneiss/schist vary from 40 to 70m
and depth to water 20-30m; the yield is normally
less than 0.5l/s, but goes up to 2.5l/s in places.
Portions show high total dissolved solids and, once
again, nitrate levels due to intense agriculture are of
concern. Around the Dendron community where the
local aquifer has served as the sole source of
irrigation water for commercial agriculture for more
than two decades, Masiyandima et al. [11] estimated
that groundwater levels had fallen by over 50m
ISBN: 978-960-474-148-9
3 Trends of water use
3.1 Groundwater use by sector
Groundwater plays a significant role in the supply of
domestic water to a majority of the rural
communities in the study area, and abstractions from
hundreds of dispersed boreholes spread across
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from a low 1.0 million m3 per year in the
Nzhelele/Nwanedi catchment to 71 million m3 per
year in the Sand catchment. By 2002, groundwater
use had increased in all catchments, totaling 136
million m3 per year, but recording the highest
growth of 200% in the Mogalakwena catchment
(Table 3). Considering that the current data in Table
1 suggest that groundwater use has now reached 261
million m3 per year or about 200 million m3 per year
if main-stem abstraction is excluded for parallel
comparison, it follows that abstraction has more
than doubled in just 10 years.
densely populated demand centres in the former
homelands of the pre-1994 apartheid set-up.
Industrial groundwater use is pronounced around the
central town of Mokopane in the Mogalakwena
cathment, with two well-fields augmenting water
supplies to platinum mines.
In the northwest around the communities of
Dendron and Bochum, and further north in the
Pontdrift and Weipe farming settlements adjacent to
the rich alluvial strips of the Limpopo main stem,
groundwater is used extensively for irrigation. In
fact, in the study area, irrigation constitutes the
highest use of groundwater (Table 1), accounting for
about 69% of the total use. Irrigation water usage is
followed by rural domestic supply at 21%,
municipal supply at 5%, mining at 4% and livestock
needs at 1%. Information feeding into Tables 1 and
2 have been obtained from the national water
department and the provincial agriculture
department, Government of Limpopo Province [12],
supplemented with additional data provided by Du
Toit [13].
Table 2: Groundwater use for irrigation
(including Limpopo main-stem)
Agricultural
community
Northern
Springbok Flats
Sandriver
Pontdrift/Weipe
Dendron
Altona
Makhado
(Louis Trichardt)
Taaibosch
Beauty/Marnitz
Total
Table 1: Groundwater use by sector
(including Limpopo main-stem)
Type of use
Irrigation
Mining
Urban Supply
Rural Supply
Stock Watering
Total
Groundwater
abstraction
(million m3/yr)
181
10
12
55
3
261
% of Total use
69
4
5
21
1
100
Groundwater
abstraction
(million m3/yr)
45
8,500
5,800
4,500
850
420
42
60
23
7
2
180
180
29,430
1
1
181
Table 3: Groundwater use & potential
(excluding Limpopo main-stem, million m3/yr)
Catchment
area
Nzhelele/
Nwanedi
Sand
Mogalakwena
Lephalala
Matlabas/
Mokolo
Total
Table 2 spreads out the irrigation component of
groundwater use according to the specific
agricultural communities, and gives an indication of
the combined farm-plots being irrigated. Sources
differ in both the actual sizes of plots and volume of
groundwater used. In fact, some estimates suggest
that irrigation abstraction from the Pontdrift/Weipe
area alone could be as high as 120 million m3 per
year, that is, twice the figure provided herein. As
Table 2 shows, the irrigation groundwater
abstraction of 181 million m3 per year is applied
over a total of 29,430 hectares in the region.
Abstraction
1995
2002
1
1.5
Potential
Initial
Available
14
12.5
71
15
4
7
74
48
4.5
8
85
125
35
75
11
77
30.5
67
98
136
334
198
Government has adopted the principle that local
groundwater resources in the area be first
considerably utilized, before additional surface
water transfers from adjoining catchments are
contemplated. As a matter of policy, consistent with
the aquifer potential in Table 3, the development of
available groundwater will now be strongly
considered across the Mokolo catchment, central
portions of the Mogalakwena catchment, and limited
parts of the Sand and Lephalala catchments.
Findings from the situation assessment of the water
resources in the Limpopo water management area,
DWAF [14], also adopted in the preparation of the
National Water Resource Strategy, indicate that in
1995, groundwater use in the area totalled 98 million
m3 per year. As of that year, groundwater use ranged
ISBN: 978-960-474-148-9
Area
irrigated
(hectares)
9,000
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3.2 Groundwater use by catchment
3.2.4 Mogalakwena catchment
Declining groundwater levels are also a source of
concern in parts of the Mogalakwena catchment, an
area that witnessed the greatest rise in abstraction
between 1995 and 2002. Hubert [3] points to overexploitation in the dolomitic aquifer in the area, but
also to excessive groundwater abstraction in the
Dorps River and Rooisloot valleys, including about
3 million m3 per year from the Mokopane well-field
west of the Dorps valley, which could be affecting
flow and yield to downstream settlements. An
element of integrated resource evaluation for
groundwater management in the area is the likely
impact of increasing mining activities already
requiring an expansion of the Mokopane well-field
and possible abstraction of over 1000 m3 per day
from an abandoned chrome mine. Also requiring
investigation are groundwater quantity and quality
stresses due to mining, as well as potential conflicts
between the demands of domestic supplies and
mining operations. In the Taaibosch area, there is a
significant abstraction of groundwater for
agricultural purposes, livestock watering and
domestic supply to rural settlements. Indeed,
domestic supply to about 20 communities is the
focus of plans for groundwater exploitation in the
fractured basalt in the Taaibosch Fault zone. The
basaltic aquifer, from which about 45 million m3 per
year of groundwater is abstracted for extensive
agricultural use, is reported to be experiencing more
than average drawdowns. In this and other cases in
the study area, aquifer responses to over-abstraction
need further examination, perhaps to inform a
review of water allocations using instruments
prescribed under South Africa’s new Water Act.
3.2.1 Limpopo main-stem
Irrigation abstraction of groundwater is extensive
around the farming communities of Pondtdrift and
Weipe in the northernmost parts of the study area,
predominantly from the alluvial aquifer. As already
alluded to, although groundwater abstraction in that
corridor is indicated here as 60 million m3 per year,
some estimates point to well over 100 million m3 per
year. Hubert [3] reports that a well-field tapping the
Limpopo River alluvium supplies 2-5 million m3 per
year to a diamond mine in Musina up-north. Also,
domestic water supply to Musina and the border
town of Beitbridge relies on boreholes drilled into
the alluvial deposits. Groundwater abstraction from
the channel storage behind weirs is a common
phenomenon on both the South African and
Botswana sides of the Limpopo River, Hubert [3].
Also, on both the Zimbabwean and South African
sides, irrigation abstraction from storage within the
riverbed sands is substantial, but reported daily
abstractions vary widely, calling for a transboundary collaborative approach to aquifer
monitoring and management.
3.2.2 Nzhelele/Nwanedi catchments
In these catchment areas, groundwater is mainly
used for domestic purposes and livestocking
watering. The low increase from 1.0 million m3 per
year in 1995 to 1.5 million m3 per in 2002 is mostly
due to an expansion in the scattered communal
human settlements using groundwater.
3.2.3 Sand catchment
The largest groundwater use in the study area occurs
in the Sand catchment, accounting for over half (74
million m3 per year) of total abstraction. Even if
Table 2 confirms the intensive use of groundwater
for irrigation in the area, fact is most water use
sectors rely, to some degree, on groundwater.
Around major human settlements in the middle and
upper reaches, there is a heavy use of groundwater
for stock watering and domestic supply. In the
vicinity of the town of Dendron, irrigated areas are
increasing in extent and groundwater application.
Aside from a groundwater use of over 20 million m3
per year fed mainly from fractured aquifers around
Dendron, additional agricultural abstraction along
the Sand River itself is estimated as about 40 million
m3 per year. While there has not been an upsurge as
such in groundwater abstraction since 1995, the
sustainability of increasing drawdowns and equity in
resource use are of growing concern and need closer
examination.
ISBN: 978-960-474-148-9
3.2.5 Lephalala/Matlabas/Mokolo catchments
Although agriculture is the largest user of
groundwater in these catchments, abstraction for
domestic use in informal settlements is increasing,
particularly in the south. Also, Hubert [3] has
observed the use of groundwater for game-ranching
and eco-tourism in the Waterberg Wilderness Area.
4 Conclusions
Irrigation constitutes the highest use of groundwater
in the study area, accounting for 69%. In the northwestern portions, particularly around the Dendron
and Bochum settlements, and further north in the
Pontdrift and Weipe communities, irrigation is
extensively fed by groundwater from the alluvium in
the Limpopo main stem. Irrigation water usage is
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for Water Resources Planning (North), DWAF,
Pretoria, 2003.
[3] Hubert, G. Internal Strategic Perspective,
Limpopo
Water
Management
Area:
Groundwater Overview. Draft Discussion
Report, DWAF, Pretoria, 2002.
[4] Vegter, J.R. Groundwater Development in South
Africa and an Introduction to the Hydrogeology
of Groundwater Regions. Report No. TT 134/00,
2001.
[5] Vegter, J.R. An Explanation of a Set of National
Groundwater Maps. Report No. TT 74/95, Water
Research Commission, Pretoria, 1995.
[6] Dziembowski, Z.M. The Geohydrology of the
Dendron Area, Pietersburg District. Report No.
GH 2878, DWAF, Pretoria, 1976.
[7] Jolly, J. Borehole/Irrigation Survey and
Groundwater Evaluation of the Doringlaagte
Drainage Basin. Report No. GH 3495, DWAF,
Pretoria, 1986.
[8] Northern Transvaal Cooperative. Investigation
of the Groundwater Resources in the Dendron
Area (Doornlaagte Catchment Area) with a view
to the Development of a Groundwater Model.
Agric Development Division, 1990.
[9] Braune, E. & Dziembowski, Z.M. Rural
Groundwater Supply Development: Study on the
Supporting Application of Environmental
Isotopes, Northern Bochum District, Northern
Province. Report GH 3908, DWAF, Pretoria,
1998.
[10] Du Toit, W.H., Botha, F.S. & Goossens, H.H.
Pontdrift/Weipe Alluvial Aquifer. Report No. GH
3958, DWAF, Pretoria, 2000.
[11] Masiyandima, M., van der Stoep, I.,
Mwanasawani,
T.
&
Pfupajena,
S.C.
‘Groundwater Management Strategies and their
Implications on Irrigated Agriculture: The Case
of Dendron Aquifer in Northern Province, South
Africa’. Proc. of 2nd WARFSA/WaterNet
Symposium, Cape Town, 2001, pp. 201-209.
[12] Government of Limpopo Province. Projects
that Use Groundwater as a Water Source. Open
File Report, Department of Agriculture,
Polokwane, 2002.
[13] Du Toit, W.H. Update on Groundwater Use
Data in the Limpopo and Levuvhu/Letaba Water
Management Areas. DWAF, Pretoria, 2002.
[14] DWAF. Limpopo Water Management Area:
Water Resources Situation Assessment, Main
Report. DWAF, Pretoria, 2002.
followed by rural domestic supply at 21%,
municipal supply at 5%, mining at 4% and livestock
needs at 1%. Industrial groundwater use is
pronounced around the central region of Mokopane,
with two well-fields augmenting supplies to
platinum mines.
As of 1995, aggregate groundwater abstraction for
the entire study area totaled 98 million m3 per year.
However, local use ranged from 1.0 million m3 per
year in the northeastern Nzhelele/Nwanedi
catchment, with predominant supply to rural
settlements, to 71 million m3 per year in the
irrigation-intensive Sand catchment. By 2002,
groundwater use had increased significantly in all
sub-basins, totaling 136 million m3 per year, but
recording the highest growth of 200% in the central
Mogalakwena catchment. Judging by the current
level of groundwater use, total abstraction from
underlying units has more than doubled over the last
10 years.
Nonetheless, in the light of the scale of future water
resources requirements for drinking and productive
use at the household level, there is a common
understanding that groundwater will increasingly be
of major relevance in water supply. And, indeed, the
prevailing policy environment requires that aquifer
development be strongly pursued across areas that
still appear to be relatively groundwater rich: the
entire Mokolo catchment, central portions of the
Mogalakwena catchment, and limited parts of the
Sand and Lephalala catchments. On a strategic note,
increasing attention is necessary to the fact that the
entire study area is part of a shared international
groundwater system. Therefore, the sustainability of
use in terms of water quality and increasing
drawdowns across trans-boundary aquifers, as well
as the concomitant issues of equity in resource use,
deserve closer examination.
Acknowledgements
This paper draws on the author’s two previous
assignments: the first on the broader trans-boundary
basin with the International Water Management
Institute; and the second on the formulation of
internal strategic perspective for the management of
regional water resources with South Africa’s then
Department of Water Affairs & Forestry (DWAF).
References:
[1] DWAF. National Water Resource Strategy.
DWAF, Pretoria, 2004.
[2] DWAF. Internal Strategic Perspective Study:
Limpopo Water Management Area. Directorate
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