An assessment of the economic water use
efficiency and productivity of the upstream
and downstream catchments’ agricultural
production, South Africa
A case study of the Baviaanskloof and Gamtoos Valley,
Eastern Cape, South Africa
M.Sc. Thesis by Annah Ndeketeya
June 2012
Irrigation and Water Engineering Group
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An assessment of the economic water use efficiency and
productivity of the upstream and downstream catchments’
agricultural production, South Africa
A case study of the Baviaanskloof and Gamtoos Valley, Eastern Cape, South
Africa
Master thesis Irrigation and Water Engineering submitted in partial fulfillment of the degree
of Master of Science in International Land and Water Management at Wageningen University,
the Netherlands
Annah Ndeketeya
June 2012
Supervisors:
Dr.ir. Gerardo van Halsema
Irrigation and Water Engineering Group
Wageningen University
The Netherlands
www.iwe.wur.nl/uk
Odirilwe Selomane
Living Lands
Eastern Cape
South Africa
www.earthcollective.net/livinglands
Facilitated by:
Participatory Restoration of Natural Capital and Ecosystem Services in the Eastern Cape
(PRESENCE), South Africa; Living Lands
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Abstract
Water scarcity is a problem that is threatening the world and pressure is growing for the
agricultural sector to cut its water use. This has given rise to the interest in water use and
efficiency in water management studies. With the aim of assessing the productivity of
Baviaanskloof valley after serious land degradation, a study was carried out to determine the
economic and physical water use efficiency for the year 2010 and the results were compared to
the downstream catchment, the Gamtoos Valley. Water productivity for the year 2011 was also
calculated for the Baviaanskloof using actual crop water use from Cropwat simulation. Data was
collected from November 2011 up to February 2012. Interview with farmers and personnel from
the Gamtoos Irrigation Board (GIB) were done to get information on water use, crops cultivated,
yields, prices, costs and cropping seasons. In some cases the bucket method was used to validate
the figures on water use obtained from the farmers. Using irrigation data on use from farmers
and other soil, crop and weather parameters from the Agricultural Research Council the
Cropwat model was run to simulate the actual crop water use and to determine the amount of
over/under irrigation. All the raw data was then analyzed using the formulas’: eWUE= net
income/total water use, WUE=yield/total water use, WP=Yield/ actual water use. Comparisons
were made per catchment from plot level to farm level then at basin level. Some differences
were noticed among farmers and the reasons varied from yield, water use and net income. Major
differences were noticed between the two catchments. The eWUE was 1.99 and 6.81R/m3 for
Baviaanskloof and Gamtoos respectively. For the common crops maize and potatoes the eWUE
was higher again for Gamtoos than for Baviaanskloof: for potatoes it was mainly because of low
yields (10t/ha) compared to 35t/ha from Gamtoos whilst in maize it was due to high water use of
about 1200mm used by the Baviaanskloof farmers whereas the other farmers used only 420mm.
The water productivity was higher than the WUE for the Baviaanskloof for most crops. The
range between WP and WUE was huge for maize, potato, wheat and tobacco whilst it was slight
for the seed vegetables. This shows there is a lot of room for improvement. From the results the
recommendation is for farmers to focus more on high value crops. The results also showed that
the total amount of water currently used for crop production is enough to irrigate approximately
271 hectares of citrus hence it is feasible for farmers to change to citrus production from a water
availability standpoint. However, strong organisation and linkages especially with downstream
farmers and GIB are needed to improve the agricultural practices in the upstream area. Further
exploration still needs to be done to see what other land use options can be adopted in the area
and the costs and benefits.
Key Words: economic WUE, physical WUE, water productivity, Cropwat simulation
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