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Equitable water allocation in a heavily committed international catchment area: the case of the Komati Catchment
Physics and Chemistry of the Earth 29 (2004) 1309–1317 www.elsevier.com/locate/pce
Equitable water allocation in a heavily committed international catchment area: the case of the Komati Catchment Sakhiwe Nkomo
a,*
, Pieter van der Zaag
b
a
b
Department of Water Affairs, Swaziland Unesco/IHE Institute for Water Education, Box 3015, Delft DA 2601, The Netherlands
Abstract This paper investigates water availability and use in the Komati catchment. The Komati catchment is shared by Swaziland and South Africa and forms part of the Incomati basin, with Mozambique as the third riparian country. In 2002 the three countries reached agreement about how the scarce water should be allocated, based on the principle of equitable and sustainable utilization, as stipulated by the SADC Protocol. The Komati catchment has five main water uses: afforestation, irrigation, the environment, urban/industrial/mining (UIM), and interbasin water transfers (for industrial use). In addition, South Africa and Swaziland have committed themselves to satisfy a certain cross border flow to downstream Mozambique. Frequently, debate has arisen between users and riparian countries on the direction that water resources development has taken in the catchment. Downstream farmers have often complained about interbasin transfers taking place in the upstream portions of the catchment. There has also been animosity about effecting environmental flow releases. A relatively simple, spreadsheet-based water resources model (Waflex) was developed to analyse water availability and use under current and future scenarios. The results were then compared to results obtained from another model that was used in a joint study by Mozambique, South Africa and Swaziland. The Waflex model showed a high degree of consistency with the one used for comparison, especially in terms of trends. It was found that the recent completion of two new dams has improved water supply to irrigation in the two countries. Future water demands will result in appreciable shortages for irrigation and domestic use. The agreed maximum development levels will soon outstrip the ability of the catchmentÕs supply. The paper shows that a combination of measures will be required to ensure equitable and sustainable water utilisation in the Komati catchment. These will have to be agreed by the riparian countries. Moreover, over the course of negotiations, important roles will have to be played by catchment management agencies and river boards in Swaziland and South Africa, as well as by the Tripartite Permanent Technical Committee of the three riparian countries. 2004 Elsevier Ltd. All rights reserved. Keywords: Water resources modelling; Consumptive water use; Instream flow requirements; Transboundary catchment management
1. Introduction The Komati catchment is part of the Incomati Basin (Fig. 1), which is shared by Swaziland, South Africa and Mozambique. The catchment, which comprises the Ko*
Corresponding author. E-mail addresses: [email protected], [email protected] (S. Nkomo). 1474-7065/$ - see front matter 2004 Elsevier Ltd. All rights reserved. doi:10.1016/j.pce.2004.09.022
mati River and its tributary the Lomati River, originates in the Drakensberg range west of the town of Carolina in Mpumalanga, South Africa. It passes through Northern Swaziland before flowing back to South Africa and joining with the Crocodile River. After the confluence the river is called the Incomati. The river then flows into Mozambique at Ressano Garcia. Several smaller rivers contribute to the Komati and Lomati in the lower reaches of the river. The catchment is shared by
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Fig. 1. The Incomati, Umbeluzi and Maputo Basins (Source: Carmo Vaz and Van der Zaag, 2003).
Swaziland and South Africa. Since it is part of the larger Incomati Basin, downstream Mozambique is also a stakeholder. The Komati catchment is located in a water-stressed region. Rainfall in the area is highly seasonal and the base flow contribution is also low resulting in the need for reservoirs for the dry season. The Komati catchment has several water using activities, some of which can be in conflict with one another. These are sugar cane and citrus irrigation, afforestation, domestic and municipal water use, industrial use, inter-basin transfers and environmental water demands. These uses have resulted in the commitment of a large percentage of the catchmentÕs mean annual runoff. In 1991 consumptive water use stood at about 690 Mm3/a, which is about 48% of the mean annual runoff (MAR) for the Komati catchment. However the three Parties to the Tripartite Interim Agreement (TIA) agreed to allow water use to increase through more irrigation and afforestation for Swaziland and South Africa to about 992 Mm3/a (TIA, 2002). This is 69% of the MAR and it is a very high level of commitment for a catchment. To satisfy the demands made on the water resources large dams have to be constructed. Today there are five large dams in the Komati catchment with a total storage capacity of about 791 Mm3. Maguga Dam in Swaziland has just been completed and has paved the way for further irrigation development in Swaziland and South Africa. It is hoped that the dam will solve some of the water stress problems in the catchment. However,
according to Waalewijn (2002), the increasing demand for primary water, downstream demands from Mozambique and the recognition of the environmental reserve will continue to place high demands on the river system. Given the high level of consumptive water use in the catchment and the erratic nature of rainfall in the region there is a need for good management of the water resources. However, the complexity of the processes and variables in the catchment makes it difficult to make informed decisions on water allocation and development. This paper therefore investigates the possible measures for the equitable and sustainable utilization of the water resources in the catchment. The paper reports the findings of a spreadsheet-based model that represents the water resources system of the Komati (Nkomo, 2003). The model can simulate the impact of various measures on existing users. These measures include: changing of environmental flow requirement, changing irrigated area of sugar cane and non-sugar cane crops, the irrigation efficiencies, changing the area under commercial (exotic) tree plantations, and changing priorities of use. The model is based on the Waflex principle (Savenije, 1995), and can be used as a tool for decision-making in the future development of water use in the Komati catchment. The first part of the paper verifies the model, by comparing its outcomes with that of a much more sophisticated model developed under the aegis of the Tripartite Permanent Technical Committee of the three riparian countries, and which was used to finalise the Joint Incomati Basin Study also known as JIBS (2001). The spreadsheet-based model uses identical input data for (surface) water availability, albeit over a shorter time series (20 years, covering the period 1950– 1969; while the JIBS model used 70 years of data covering the period 1920–1989).
2. The Komati basin The total length of the Komati river from its source to the confluence with the Crocodile River is approximately 450 km. The total catchment area is 11,200 Mm2 (including 1493 Mm2 for the Lomati River). About 2560 Mm2 of the catchment falls in the northern part of Swaziland, the remainder is in South Africa (Fig. 2). The Komati Sub-catchment has a mean annual runoff of 1420 Mm3/a and a mean annual precipitation of 800 mm/a. The catchment experiences rainfall in the summer months of October–March and it generally increases from east to west. The potential evaporation decreases from east to west as a result of lower temperatures in the mountainous western part of the catchment. Hence irrigation becomes more important for crop production towards the east (Carmo Vaz and Van der Zaag, 2003).
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Fig. 2. The Komati catchment (Source: JIBS, 2001).
Presently, large dams (exceeding 9 Mm3) that have been constructed in the Komati sub-catchment are Nooitgedacht, Vygeboom, Sand River (off-channel), Driekoppies and Maguga Dams. In addition the catchment contains some smaller farm dams and weirs.
3. The Waflex model The Waflex model is a water resources model with a monthly timestep that can be used as a management tool in a catchment. It is a spreadsheet model that provides transparency and flexibility. The Waflex model has been developed to tackle problems such as the allocation of scarce resources like water. Its network functions are based on the equation of continuity and the fact that water flows from upstream to downstream. These network functions are relations between cells that can be copied to any location in the sheet to mould the network (Savenije, 1995). Reservoirs can be incorporated into the network. A reservoir consists of three cells; an inflow cell, a storage cell and a release cell. The release cell acts as an inflow point to the downstream branch. The storage and release of the reservoir is determined in a macro subroutine and takes into account the flood rule curve (FRC), the utility rule curve (URC) and the dead storage curve (DSC). The storage can never exceed the FRC and the DSC may never be crossed as a result of a release. Thus the FRC and the DSC are hard boundaries. The URC is a soft boundary that separates two zones of differing operating rules in the reservoir. Evaporation losses from each dam are calculated using storage––area curves. The evaporation losses for a particular timestep are calculated using dam storage for the previous timestep.
The water requirement from the reservoirs is computed in a ‘‘mirror–image’’ network that exists next to the ‘‘real’’ network. The mirror–image network differs from the real network in that it computes the required demand in the upstream direction starting from the downstream outflow requirement (De Groen, 2002). The network of the Komati Waflex model is shown in Fig. 3. There are five large dams that have been modelled in the catchment. These are the Nooitgedacht, Vygeboom, Maguga, Sand River and Driekoppies dams. The Sand River Dam is an off-channel storage owned by Mhlume Sugar Company and pumps water out of the river according to the water abstraction permit of Mhlume Sugar. For purposes of modelling, the principle of capacity sharing (Natsa et al., 2000) has been used to split Maguga Dam into two virtual dams since 40% of the dam is owned by Swaziland and 60% by South Africa. Depending on the scenario, the upper Komati dams may be required to release water for downstream users. In this case the difference between what is required of Maguga Dam and what it actually releases is computed at the beginning of each timestep. If the difference is greater than zero, the requirement from the upper Komati dams then includes the deficit being faced downstream. The water released is recalculated to include the compensation by Nooitgedacht and Vygeboom dams. The model incorporates nine water abstraction nodes. The node numbers and names are shown in Table 1. The node numbers and location are shown in the model schematic in Fig. 3. Return flows from irrigation are calculated as a percentage of water lost through inefficiency of the irrigation system. The output of the model is in the form of the satisfaction of the demands for all the water using activities in
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Inflow point 9
8
10
11 12
Abstraction node 7 Dam 9 Border
South Africa
Downstream compensation
2
1
10
Nooitgedacht
South Africa
Swaziland
3
5
4
Vygeboom 2
11
Driekoppies
Maguga 3
6
7
Sand 5
6
Fig. 3. Schematic diagram for Komati catchment Waflex model.
Table 1 Location of abstraction nodes Name
Node #
Nooitgedacht
2
Vygeboom
3
Maguga Sand River Tonga
5 6 7
Ngonini Driekoppies Vlakbult Komatipoort
9 10 11 12
4.1. Reducing and/or decreasing priority of interbasin transfer to power plants Location Downstream Nooitgedacht in upper Komati Downstream Vygeboom in upper Komati Downstream Maguga in Swaziland Downstream Sand River in Swaziland Lower Komati before confluence with Lomati Upper Lomati in Swaziland Downstream Driekoppies Lomati before confluence with Komati Lower Komati after confluence with Lomati
the catchment. The satisfaction is defined as the percentage of the time in which the demand is fully met. The satisfaction measured by the Waflex model is similar to the assurance of supply as calculated by the model used for the JIBS study. The model also monitors the compliance to instream flow requirements that have been agreed to by Mozambique, South Africa and Swaziland. This is calculated as a percentage of the total number of time steps in which these requirements are fully complied with. 4. Possible intervention measures Possible measures to achieve equitable and sustainable use of the water resources in the Komati catchment include the following.
Water transfers for industrial use (cooling power plants) withdraw a volume of about 132 Mm3/a from the Komati catchment. Approximately 80% of the water consumed at wet-cooled power stations like the ones in the upper Komati is lost due to evaporation from the cooling towers. Dry-cooled technology reduces these losses and hence the total amount of water consumed at the power station (DFID, 2002). According to the Tripartite Interim Agreement (TIA) between Mozambique, South Africa and Swaziland, this water transfer has a high priority. This results in less water being available for downstream irrigation activities. To increase the water available downstream the two upper Komati dams could release water downstream when there is a shortage. This may mean giving the water transfers a lower priority or reducing the demand due to water transfers. In this research the reduction of the demand for transfers is modelled as well as the release of water from Nooitgedacht and Vygeboom dams to compensate for shortages in downstream dams. 4.2. Reducing afforestation levels Afforestation is one of the major water users in the catchment. A reduction in the area covered by commercial forests would result in a proportional reduction in the water use by afforestation. The data available is for runoff reduction due to 2000 afforestation levels and the areas covered by forests in 1991 and 2000. In
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this research an analysis will be made given that afforestation areas drop to a third of 2002 levels. 4.2.1. Environmental water requirements The environmental water requirements used in the model are maintenance of low instream flow as calculated in the JIBS Phase II study. The environmental management classes C and D are analysed and compared in the model (Class C is more water demanding than Class D). The satisfaction of environmental flows as agreed in the Tri-Partite Interim Agreement is also monitored at the key points of Diepgezet, Mananga and Lebombo. 4.3. Swapping irrigated crops At present sugar cane growing occupies more land than any other crop. Sugar cane is a water-hungry crop (about 10,000 m3/ha) and swapping of sugar cane with non-sugar cane crops (about 4900 m3/ha) may lead to reduced use of water by irrigation. In the model crops other than sugar cane have been lumped together as non-sugar for simplicity. 4.4. Increasing irrigation efficiency At present, the main irrigation methods in Swaziland are furrow (39%), sprinkler (54%), drip (4%) and centre pivot (3%). This is estimated to be equivalent to an irrigation efficiency of 60% for Swaziland. South Africa uses mainly sprinkler or dragline irrigation systems. Drip and centre pivot irrigation systems are also used to a lesser extent. The efficiency in South Africa is approximately 70%. Intervention measures can aim to convert irrigation schemes to higher efficient systems. One such measure is to convert all irrigation to drip systems, with an assumed efficiency of 90%. 5. Verification of the Waflex model In order to compare the results from the Waflex model with those from the JIBS model, two initial model runs were conducted. Run 1a simulates 1991 water requirements and 1991 infrastructure, i.e. without Maguga and Driekoppies dams. Run 1b assumes maximum future water requirements as allowed by the TIA but without new infrastructure. The resulting satisfaction levels of the various groups of water users are shown in Fig. 4a and b. The JIBS model came up with assurance of supply levels between 96% and 100% for UIM (urban/industrial/mining) requirements in 1991 for each country. The results of future water requirements (2015) in the JIBS study resulted in assurance levels of 80% and less for UIM requirements in each country and 39% and 43% for irrigation in Swaziland and South Africa, respectively.
Fig. 4. (a) Verification run for 1991. (b) Verification run for 2015.
100 Satisfaction (%)
80
92 73
80
96
89
96
81 80
60 40 Waflex JIBS
20 0
(a)
IRR-RSA
IRR-SWA
100 Satisfaction (%)
86
80 61 43 40
JIBS
(b)
80
84
80
58
60
Waflex
UIM-RSA UIM-SWA
39
20 0 IRR-RSA
IRR-SWA
UIM-RSA UIM-SWA
Fig. 5. (a) Comparison of Waflex results with JIBS for 1991. (b) Comparison of Waflex results with JIBS for 2015.
The comparison between the JIBS model and the Waflex model is shown in Fig. 5a and b. The JIBS model treated the water transfer in South Africa as an urban water use and the one in Swaziland as an irrigation use. Weighted averages have therefore been used
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to illustrate the comparison more clearly. In the case of 1991, the results from the Waflex model are comparable for Swaziland where the satisfaction is 81%. The satisfaction for South Africa is underestimated by the Waflex model (73%). The UIM requirements in South Africa are found to have a satisfaction level of 92% and 89% in Swaziland. The figures are therefore lower than those found by the JIBS model. In the simulation for the year 2015, the Waflex shows the satisfaction of UIM water requirements to be 84% and 86% for Swaziland and South Africa, respectively. This slightly overestimates the assurance given by JIBS. The satisfaction for irrigation is found to drop down to 61% and 58% for South Africa and Swaziland, respectively. This is, again, higher than the JIBS result. However, it can be observed that although the actual figures from the Waflex are higher, the same conclusion can be drawn from the results, i.e. that an increase in irrigation to the planned levels and an increase in urban demands without new infrastructure will result in unacceptably low satisfaction of those demands, and that Swaziland is slightly more affected than South Africa. A reason for the differences in outcomes between the Waflex and JIBS models may be the fact that the Waflex model used 20 years of input data (1950–1969) whereas the JIBS study used 70 years of data (1920–1989). This could be investigated by obtaining the whole input data set used in JIBS and running it in the Waflex model. In conclusion, the verification has shown that the Waflex model demonstrates a considerable degree of consistency with the JIBS model, especially in terms of trends. However, with increasing consumptive water use the Waflex model appears to return higher satisfaction levels than the JIBS model. The results from the Waflex model therefore need to be interpreted with care, and further verification is required.
6. Results of different development scenarios 6.1. Present and future water use Run 2a simulates the water use situation as in 2003. In this run both Driekoppies and Maguga dams have been constructed. The results are shown in Fig. 6a. Run 2b simulates the future situation, as allowed by the Tripartite Interim Agreement, without any special measures (Fig. 6b). When Fig. 6b is compared with Fig. 4b, it may be concluded that the construction of new infrastructure benefits South Africa more than Swaziland. This is so because without Maguga dam the model assumed that Swaziland would simply take out all the water that it required, whereas with Maguga dam in place, the requirements of downstream areas in South Africa are also taken into account. In fact, all water using sectors in
Fig. 6. (a) Satisfaction of demands of 2003. (b) Satisfaction of future water requirements with additional infrastructure.
Swaziland will obtain satisfaction levels that are unacceptable (below 80%). This is especially worrying for the UIM sector. However, the water stress in Swaziland also affects South Africa downstream, as the agreed cross-border flow at Mananga (TIA, 2002) cannot be maintained, and is violated in 27% of the months. Hence the need to look into possible intervention measures. The following two sections analyse measures related to interbasin transfers and irrigation. Two other sets of measures, related to exotic tree plantations and instream flow requirements, have been omitted due to lack of space. The model runs are based on the future water requirements, and the effect of the proposed measures are analysed by comparing the results with model run 2b (Fig. 6b). 6.2. Interbasin water transfer
1
Runs 4 and 5 deal with the interbasin transfer of water in the Upper Komati in South Africa, that brings cooling water to thermal power stations in the Olifants river (part of the Limpopo basin). Run 4 gives the South African interbasin transfer a low priority (TIA and JIBS consider this transfer to be industrial use, with the high1
Note that decreasing the transfer from the Komati to the Umbeluzi basin in Swaziland was not considered because of the negative impact this might have on the water situation of Maputo, which may then result in increased water demand from this city on the Incomati water resources, not freeing up any water.
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Fig. 7. (a) Satisfaction of future requirements with reduced priority for water transfers. (b) Satisfaction of future requirements with reduced volume for water transfers.
est priority). Run 5 halves the amount of water transferred (from 132 to 66 Mm3/a), while retaining its high priority. The results are shown in Fig. 7a and b. Assigning a low priority to the interbasin transfer improves the satisfaction levels for agriculture and urban requirements due to releases from the Nooitgedacht and Vygeboom dams, but the transfer itself suffers a decrease in satisfaction to 57%. If the amount of water transferred is halved, the improvement in satisfaction is slightly more for irrigation and urban use, even though the transfer retains its highest priority, and can satisfy the reduced demand for water to be transferred for 90%.
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Fig. 8. (a) Satisfaction of future requirements with increased irrigation efficiency. (b) Satisfaction with half of sugar cane swapped for nonsugar cane.
The increase in irrigation efficiency results in a significant gain in the satisfaction levels of irrigation in both countries. Urban requirements in Swaziland also benefit significantly while they remain static at an acceptable 97% in South Africa. The swapping of sugar cane areas for non-sugar crops leads to improved satisfaction levels for irrigation and urban requirements only in Swaziland.
6.3. Irrigation: increasing efficiency and swapping crops Model runs 7 and 8 deal with irrigated crops. Run 7 simulates a situation whereby the irrigation efficiency of all irrigation systems in the catchment is increased to 90%. Note that the Interbasin Transfer from Sand River dam in Swaziland is now reduced, since the area irrigated now requires less water. Model run 8 assumes that half of the area that is assumed to be under sugar cane in the future is converted into less water-demanding nonsugar cane crops. The results are presented in Fig. 8a and b.
Fig. 9. Satisfaction with reduced water transfers, higher irrigation efficiency, crop swap and Class C IFR.
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6.4. Combined measures Model run 9, finally, combines three measures: halving the interbasin transfer in the Upper Komati, increasing the irrigation efficiency to 90% and converting half of the sugar cane area to non-sugar cane crops. Fig. 9 shows the results. 7. Conclusions and recommendations It is evident that the implementation of the Komati Basin Development Project, with the construction of Driekoppies and Maguga dams, resulted in the improvement of water availability for both Swaziland and South Africa. However, this may change in the future, when the water required will outstrip the ability of the catchment to supply it equitably and sustainably. Water shortages can be expected in future in some parts of the catchment as development approaches that allowed by present agreements. Releasing water from the dams in the Upper Komati will go a long way in relieving the shortage of water in Swaziland and the Lower Komati. It must be considered whether it is possible to reduce the water transfers from Nooitgedacht and Vygeboom dams to 62 Mm3/a, for instance through investments in cooling technologies that use less water. This also implies that in the continuing negotiations concerning the utilisation of the water resources in the Incomati water transfers in the catchment will have to be isolated as a unique type of water use. All concerned parties may then be able to discuss their differences over the priority of one distinct use over another. Reducing afforestation levels has a negligible effect on the satisfaction of water demands for other users (Nkomo, 2003). The study has not shown that reducing afforestation would yield any significant amounts of water for other uses. Thus the measure of cutting back on afforestation may perhaps cause more harm than good to the economy given that forestry contributes significantly to employment. Decreasing environmental water requirements from Class C to Class D leads to more violations of cross-border flows although they avail more water for other uses (Nkomo, 2003). Class C requirements may be more appropriate to maintain because they may prevent further degradation of the riverÕs ecology. Nevertheless it is suggested that instream flow requirements at appropriate river reaches be comprehensively determined before a final agreement is reached on the Incomati Basin. Reduction of sugar cane in favour of other less waterhungry crops would result in increased water availability in the long term. Increasing the efficiency of irrigation results in slightly higher satisfaction levels for all users. However, the implications of higher irrigation efficiency
are that the yields and hence consumptive water use by crops increases. Due to the increased efficiency, return flows will also decrease. The repercussions for downstream users who rely on return flows need to be addressed. The city of Maputo in Mozambique is an especially delicate case since it relies on return flows from irrigation in Swaziland along the Umbeluzi river. It is clear from the results presented in this paper that a combination of measures will be required to ensure equitable and sustainable water utilisation in the Komati catchment. Implementation of the measures would require careful negotiations in an open and well-informed environment, and will have to be agreed by the two riparian countries. In addition, all other interested parties, such as the various water user groups and downstream Mozambique need to be consulted. In the negotiations, important roles will have to be played by catchment management agencies and river boards in Swaziland and South Africa, as well as by the Tripartite Permanent Technical Committee of the three riparian countries. The Waflex model, as the JIBS model, may play a positive role in facilitating such negotiations, by means of estimating the effects of various combinations of measures. Such models bring out important water management issues, may trigger technical cooperation and promote understanding of each otherÕs interests and viewpoints. The following recommendations are made: • Given that the results of the Waflex model differ from those of the JIBS model, it is suggested that further verification of the Waflex model be done before the results can be taken as conclusive. • It is evident that a combination of measures would be necessary in order to improve the future availability of water for irrigation and domestic use downstream. The release of water from the Upper Komati and increasing irrigation efficiency seem particularly promising. • Reduction of sugar cane in favour of other less waterhungry crops is an option which may result in less problems of water shortage in the long term. If higher value crops are chosen (e.g. horticulture, flowers, etc.) there may also be an economic benefit.
References Carmo Vaz, A., Van der Zaag, P., 2003. Sharing the Incomati waters: cooperation and competition in the balance. UNESCO—IHP Technical Document/PCCP series number 13. UNESCO, Paris. DFID, 2002. Handbook for the Assessment of Catchment Water Demand and Use. Unpublished draft, Department for International Development in collaboration with Department of Water Development. H R Wallingford.
S. Nkomo, P. van der Zaag / Physics and Chemistry of the Earth 29 (2004) 1309–1317 De Groen, M., 2002. Water Resources Modelling: Lecture Handouts, Department of Civil Engineering, University of Zimbabwe. JIBS, 2001. Joint Inkomati Basin Study Phase 2. Consultec in association with BKS Acres. Final Draft, April 2001. Natsa, T.F., Nyagwambo, N.L., Van der Zaag, P., 2000. Comparing alternative surface water allocation scenarios for Zimbabwe. In: Proceedings 4th Biennial Congress of the African Division of the Intl. Ass. of Hydraulic Research ÔConserving and Sharing Water Resources in a Water Scarce EnvironmentÕ. Windhoek, June 7–9. Nkomo, S.M., 2003. Water resources modelling in the Komati Catchment shared by South Africa and Swaziland. Unpublished MSc thesis. University of Zimbabwe, Harare.
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Savenije, H.H.G., 1995. Spreadsheets: flexible tools for integrated management of water resources in river basins. In: Modelling and Management of Sustainable Basin-scale Water Resources Systems. IAHS Publications no. 231, pp. 207–215. TIA, 2002. Tripartite Interim Agreement between Mozambique, South Africa and Swaziland for co-operation on the protection and sustainable utilisation of the water resources of the Incomati and Maputo watercourses. Johannesburg, 29 August 2002. Waalewijn, P., 2002. Squeezing the cow: perceptions and strategies of stakeholders, concerning river basin management in the Lower Komati River, South Africa. Unpublished MSc thesis. Wageningen University, Wageningen.
Equitable water allocation in a heavily committed international catchment area: the case of the Komati Catchment Sakhiwe Nkomo
a,*
, Pieter van der Zaag
b
a
b
Department of Water Affairs, Swaziland Unesco/IHE Institute for Water Education, Box 3015, Delft DA 2601, The Netherlands
Abstract This paper investigates water availability and use in the Komati catchment. The Komati catchment is shared by Swaziland and South Africa and forms part of the Incomati basin, with Mozambique as the third riparian country. In 2002 the three countries reached agreement about how the scarce water should be allocated, based on the principle of equitable and sustainable utilization, as stipulated by the SADC Protocol. The Komati catchment has five main water uses: afforestation, irrigation, the environment, urban/industrial/mining (UIM), and interbasin water transfers (for industrial use). In addition, South Africa and Swaziland have committed themselves to satisfy a certain cross border flow to downstream Mozambique. Frequently, debate has arisen between users and riparian countries on the direction that water resources development has taken in the catchment. Downstream farmers have often complained about interbasin transfers taking place in the upstream portions of the catchment. There has also been animosity about effecting environmental flow releases. A relatively simple, spreadsheet-based water resources model (Waflex) was developed to analyse water availability and use under current and future scenarios. The results were then compared to results obtained from another model that was used in a joint study by Mozambique, South Africa and Swaziland. The Waflex model showed a high degree of consistency with the one used for comparison, especially in terms of trends. It was found that the recent completion of two new dams has improved water supply to irrigation in the two countries. Future water demands will result in appreciable shortages for irrigation and domestic use. The agreed maximum development levels will soon outstrip the ability of the catchmentÕs supply. The paper shows that a combination of measures will be required to ensure equitable and sustainable water utilisation in the Komati catchment. These will have to be agreed by the riparian countries. Moreover, over the course of negotiations, important roles will have to be played by catchment management agencies and river boards in Swaziland and South Africa, as well as by the Tripartite Permanent Technical Committee of the three riparian countries. 2004 Elsevier Ltd. All rights reserved. Keywords: Water resources modelling; Consumptive water use; Instream flow requirements; Transboundary catchment management
1. Introduction The Komati catchment is part of the Incomati Basin (Fig. 1), which is shared by Swaziland, South Africa and Mozambique. The catchment, which comprises the Ko*
Corresponding author. E-mail addresses: [email protected], [email protected] (S. Nkomo). 1474-7065/$ - see front matter 2004 Elsevier Ltd. All rights reserved. doi:10.1016/j.pce.2004.09.022
mati River and its tributary the Lomati River, originates in the Drakensberg range west of the town of Carolina in Mpumalanga, South Africa. It passes through Northern Swaziland before flowing back to South Africa and joining with the Crocodile River. After the confluence the river is called the Incomati. The river then flows into Mozambique at Ressano Garcia. Several smaller rivers contribute to the Komati and Lomati in the lower reaches of the river. The catchment is shared by
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Fig. 1. The Incomati, Umbeluzi and Maputo Basins (Source: Carmo Vaz and Van der Zaag, 2003).
Swaziland and South Africa. Since it is part of the larger Incomati Basin, downstream Mozambique is also a stakeholder. The Komati catchment is located in a water-stressed region. Rainfall in the area is highly seasonal and the base flow contribution is also low resulting in the need for reservoirs for the dry season. The Komati catchment has several water using activities, some of which can be in conflict with one another. These are sugar cane and citrus irrigation, afforestation, domestic and municipal water use, industrial use, inter-basin transfers and environmental water demands. These uses have resulted in the commitment of a large percentage of the catchmentÕs mean annual runoff. In 1991 consumptive water use stood at about 690 Mm3/a, which is about 48% of the mean annual runoff (MAR) for the Komati catchment. However the three Parties to the Tripartite Interim Agreement (TIA) agreed to allow water use to increase through more irrigation and afforestation for Swaziland and South Africa to about 992 Mm3/a (TIA, 2002). This is 69% of the MAR and it is a very high level of commitment for a catchment. To satisfy the demands made on the water resources large dams have to be constructed. Today there are five large dams in the Komati catchment with a total storage capacity of about 791 Mm3. Maguga Dam in Swaziland has just been completed and has paved the way for further irrigation development in Swaziland and South Africa. It is hoped that the dam will solve some of the water stress problems in the catchment. However,
according to Waalewijn (2002), the increasing demand for primary water, downstream demands from Mozambique and the recognition of the environmental reserve will continue to place high demands on the river system. Given the high level of consumptive water use in the catchment and the erratic nature of rainfall in the region there is a need for good management of the water resources. However, the complexity of the processes and variables in the catchment makes it difficult to make informed decisions on water allocation and development. This paper therefore investigates the possible measures for the equitable and sustainable utilization of the water resources in the catchment. The paper reports the findings of a spreadsheet-based model that represents the water resources system of the Komati (Nkomo, 2003). The model can simulate the impact of various measures on existing users. These measures include: changing of environmental flow requirement, changing irrigated area of sugar cane and non-sugar cane crops, the irrigation efficiencies, changing the area under commercial (exotic) tree plantations, and changing priorities of use. The model is based on the Waflex principle (Savenije, 1995), and can be used as a tool for decision-making in the future development of water use in the Komati catchment. The first part of the paper verifies the model, by comparing its outcomes with that of a much more sophisticated model developed under the aegis of the Tripartite Permanent Technical Committee of the three riparian countries, and which was used to finalise the Joint Incomati Basin Study also known as JIBS (2001). The spreadsheet-based model uses identical input data for (surface) water availability, albeit over a shorter time series (20 years, covering the period 1950– 1969; while the JIBS model used 70 years of data covering the period 1920–1989).
2. The Komati basin The total length of the Komati river from its source to the confluence with the Crocodile River is approximately 450 km. The total catchment area is 11,200 Mm2 (including 1493 Mm2 for the Lomati River). About 2560 Mm2 of the catchment falls in the northern part of Swaziland, the remainder is in South Africa (Fig. 2). The Komati Sub-catchment has a mean annual runoff of 1420 Mm3/a and a mean annual precipitation of 800 mm/a. The catchment experiences rainfall in the summer months of October–March and it generally increases from east to west. The potential evaporation decreases from east to west as a result of lower temperatures in the mountainous western part of the catchment. Hence irrigation becomes more important for crop production towards the east (Carmo Vaz and Van der Zaag, 2003).
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Fig. 2. The Komati catchment (Source: JIBS, 2001).
Presently, large dams (exceeding 9 Mm3) that have been constructed in the Komati sub-catchment are Nooitgedacht, Vygeboom, Sand River (off-channel), Driekoppies and Maguga Dams. In addition the catchment contains some smaller farm dams and weirs.
3. The Waflex model The Waflex model is a water resources model with a monthly timestep that can be used as a management tool in a catchment. It is a spreadsheet model that provides transparency and flexibility. The Waflex model has been developed to tackle problems such as the allocation of scarce resources like water. Its network functions are based on the equation of continuity and the fact that water flows from upstream to downstream. These network functions are relations between cells that can be copied to any location in the sheet to mould the network (Savenije, 1995). Reservoirs can be incorporated into the network. A reservoir consists of three cells; an inflow cell, a storage cell and a release cell. The release cell acts as an inflow point to the downstream branch. The storage and release of the reservoir is determined in a macro subroutine and takes into account the flood rule curve (FRC), the utility rule curve (URC) and the dead storage curve (DSC). The storage can never exceed the FRC and the DSC may never be crossed as a result of a release. Thus the FRC and the DSC are hard boundaries. The URC is a soft boundary that separates two zones of differing operating rules in the reservoir. Evaporation losses from each dam are calculated using storage––area curves. The evaporation losses for a particular timestep are calculated using dam storage for the previous timestep.
The water requirement from the reservoirs is computed in a ‘‘mirror–image’’ network that exists next to the ‘‘real’’ network. The mirror–image network differs from the real network in that it computes the required demand in the upstream direction starting from the downstream outflow requirement (De Groen, 2002). The network of the Komati Waflex model is shown in Fig. 3. There are five large dams that have been modelled in the catchment. These are the Nooitgedacht, Vygeboom, Maguga, Sand River and Driekoppies dams. The Sand River Dam is an off-channel storage owned by Mhlume Sugar Company and pumps water out of the river according to the water abstraction permit of Mhlume Sugar. For purposes of modelling, the principle of capacity sharing (Natsa et al., 2000) has been used to split Maguga Dam into two virtual dams since 40% of the dam is owned by Swaziland and 60% by South Africa. Depending on the scenario, the upper Komati dams may be required to release water for downstream users. In this case the difference between what is required of Maguga Dam and what it actually releases is computed at the beginning of each timestep. If the difference is greater than zero, the requirement from the upper Komati dams then includes the deficit being faced downstream. The water released is recalculated to include the compensation by Nooitgedacht and Vygeboom dams. The model incorporates nine water abstraction nodes. The node numbers and names are shown in Table 1. The node numbers and location are shown in the model schematic in Fig. 3. Return flows from irrigation are calculated as a percentage of water lost through inefficiency of the irrigation system. The output of the model is in the form of the satisfaction of the demands for all the water using activities in
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Inflow point 9
8
10
11 12
Abstraction node 7 Dam 9 Border
South Africa
Downstream compensation
2
1
10
Nooitgedacht
South Africa
Swaziland
3
5
4
Vygeboom 2
11
Driekoppies
Maguga 3
6
7
Sand 5
6
Fig. 3. Schematic diagram for Komati catchment Waflex model.
Table 1 Location of abstraction nodes Name
Node #
Nooitgedacht
2
Vygeboom
3
Maguga Sand River Tonga
5 6 7
Ngonini Driekoppies Vlakbult Komatipoort
9 10 11 12
4.1. Reducing and/or decreasing priority of interbasin transfer to power plants Location Downstream Nooitgedacht in upper Komati Downstream Vygeboom in upper Komati Downstream Maguga in Swaziland Downstream Sand River in Swaziland Lower Komati before confluence with Lomati Upper Lomati in Swaziland Downstream Driekoppies Lomati before confluence with Komati Lower Komati after confluence with Lomati
the catchment. The satisfaction is defined as the percentage of the time in which the demand is fully met. The satisfaction measured by the Waflex model is similar to the assurance of supply as calculated by the model used for the JIBS study. The model also monitors the compliance to instream flow requirements that have been agreed to by Mozambique, South Africa and Swaziland. This is calculated as a percentage of the total number of time steps in which these requirements are fully complied with. 4. Possible intervention measures Possible measures to achieve equitable and sustainable use of the water resources in the Komati catchment include the following.
Water transfers for industrial use (cooling power plants) withdraw a volume of about 132 Mm3/a from the Komati catchment. Approximately 80% of the water consumed at wet-cooled power stations like the ones in the upper Komati is lost due to evaporation from the cooling towers. Dry-cooled technology reduces these losses and hence the total amount of water consumed at the power station (DFID, 2002). According to the Tripartite Interim Agreement (TIA) between Mozambique, South Africa and Swaziland, this water transfer has a high priority. This results in less water being available for downstream irrigation activities. To increase the water available downstream the two upper Komati dams could release water downstream when there is a shortage. This may mean giving the water transfers a lower priority or reducing the demand due to water transfers. In this research the reduction of the demand for transfers is modelled as well as the release of water from Nooitgedacht and Vygeboom dams to compensate for shortages in downstream dams. 4.2. Reducing afforestation levels Afforestation is one of the major water users in the catchment. A reduction in the area covered by commercial forests would result in a proportional reduction in the water use by afforestation. The data available is for runoff reduction due to 2000 afforestation levels and the areas covered by forests in 1991 and 2000. In
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this research an analysis will be made given that afforestation areas drop to a third of 2002 levels. 4.2.1. Environmental water requirements The environmental water requirements used in the model are maintenance of low instream flow as calculated in the JIBS Phase II study. The environmental management classes C and D are analysed and compared in the model (Class C is more water demanding than Class D). The satisfaction of environmental flows as agreed in the Tri-Partite Interim Agreement is also monitored at the key points of Diepgezet, Mananga and Lebombo. 4.3. Swapping irrigated crops At present sugar cane growing occupies more land than any other crop. Sugar cane is a water-hungry crop (about 10,000 m3/ha) and swapping of sugar cane with non-sugar cane crops (about 4900 m3/ha) may lead to reduced use of water by irrigation. In the model crops other than sugar cane have been lumped together as non-sugar for simplicity. 4.4. Increasing irrigation efficiency At present, the main irrigation methods in Swaziland are furrow (39%), sprinkler (54%), drip (4%) and centre pivot (3%). This is estimated to be equivalent to an irrigation efficiency of 60% for Swaziland. South Africa uses mainly sprinkler or dragline irrigation systems. Drip and centre pivot irrigation systems are also used to a lesser extent. The efficiency in South Africa is approximately 70%. Intervention measures can aim to convert irrigation schemes to higher efficient systems. One such measure is to convert all irrigation to drip systems, with an assumed efficiency of 90%. 5. Verification of the Waflex model In order to compare the results from the Waflex model with those from the JIBS model, two initial model runs were conducted. Run 1a simulates 1991 water requirements and 1991 infrastructure, i.e. without Maguga and Driekoppies dams. Run 1b assumes maximum future water requirements as allowed by the TIA but without new infrastructure. The resulting satisfaction levels of the various groups of water users are shown in Fig. 4a and b. The JIBS model came up with assurance of supply levels between 96% and 100% for UIM (urban/industrial/mining) requirements in 1991 for each country. The results of future water requirements (2015) in the JIBS study resulted in assurance levels of 80% and less for UIM requirements in each country and 39% and 43% for irrigation in Swaziland and South Africa, respectively.
Fig. 4. (a) Verification run for 1991. (b) Verification run for 2015.
100 Satisfaction (%)
80
92 73
80
96
89
96
81 80
60 40 Waflex JIBS
20 0
(a)
IRR-RSA
IRR-SWA
100 Satisfaction (%)
86
80 61 43 40
JIBS
(b)
80
84
80
58
60
Waflex
UIM-RSA UIM-SWA
39
20 0 IRR-RSA
IRR-SWA
UIM-RSA UIM-SWA
Fig. 5. (a) Comparison of Waflex results with JIBS for 1991. (b) Comparison of Waflex results with JIBS for 2015.
The comparison between the JIBS model and the Waflex model is shown in Fig. 5a and b. The JIBS model treated the water transfer in South Africa as an urban water use and the one in Swaziland as an irrigation use. Weighted averages have therefore been used
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to illustrate the comparison more clearly. In the case of 1991, the results from the Waflex model are comparable for Swaziland where the satisfaction is 81%. The satisfaction for South Africa is underestimated by the Waflex model (73%). The UIM requirements in South Africa are found to have a satisfaction level of 92% and 89% in Swaziland. The figures are therefore lower than those found by the JIBS model. In the simulation for the year 2015, the Waflex shows the satisfaction of UIM water requirements to be 84% and 86% for Swaziland and South Africa, respectively. This slightly overestimates the assurance given by JIBS. The satisfaction for irrigation is found to drop down to 61% and 58% for South Africa and Swaziland, respectively. This is, again, higher than the JIBS result. However, it can be observed that although the actual figures from the Waflex are higher, the same conclusion can be drawn from the results, i.e. that an increase in irrigation to the planned levels and an increase in urban demands without new infrastructure will result in unacceptably low satisfaction of those demands, and that Swaziland is slightly more affected than South Africa. A reason for the differences in outcomes between the Waflex and JIBS models may be the fact that the Waflex model used 20 years of input data (1950–1969) whereas the JIBS study used 70 years of data (1920–1989). This could be investigated by obtaining the whole input data set used in JIBS and running it in the Waflex model. In conclusion, the verification has shown that the Waflex model demonstrates a considerable degree of consistency with the JIBS model, especially in terms of trends. However, with increasing consumptive water use the Waflex model appears to return higher satisfaction levels than the JIBS model. The results from the Waflex model therefore need to be interpreted with care, and further verification is required.
6. Results of different development scenarios 6.1. Present and future water use Run 2a simulates the water use situation as in 2003. In this run both Driekoppies and Maguga dams have been constructed. The results are shown in Fig. 6a. Run 2b simulates the future situation, as allowed by the Tripartite Interim Agreement, without any special measures (Fig. 6b). When Fig. 6b is compared with Fig. 4b, it may be concluded that the construction of new infrastructure benefits South Africa more than Swaziland. This is so because without Maguga dam the model assumed that Swaziland would simply take out all the water that it required, whereas with Maguga dam in place, the requirements of downstream areas in South Africa are also taken into account. In fact, all water using sectors in
Fig. 6. (a) Satisfaction of demands of 2003. (b) Satisfaction of future water requirements with additional infrastructure.
Swaziland will obtain satisfaction levels that are unacceptable (below 80%). This is especially worrying for the UIM sector. However, the water stress in Swaziland also affects South Africa downstream, as the agreed cross-border flow at Mananga (TIA, 2002) cannot be maintained, and is violated in 27% of the months. Hence the need to look into possible intervention measures. The following two sections analyse measures related to interbasin transfers and irrigation. Two other sets of measures, related to exotic tree plantations and instream flow requirements, have been omitted due to lack of space. The model runs are based on the future water requirements, and the effect of the proposed measures are analysed by comparing the results with model run 2b (Fig. 6b). 6.2. Interbasin water transfer
1
Runs 4 and 5 deal with the interbasin transfer of water in the Upper Komati in South Africa, that brings cooling water to thermal power stations in the Olifants river (part of the Limpopo basin). Run 4 gives the South African interbasin transfer a low priority (TIA and JIBS consider this transfer to be industrial use, with the high1
Note that decreasing the transfer from the Komati to the Umbeluzi basin in Swaziland was not considered because of the negative impact this might have on the water situation of Maputo, which may then result in increased water demand from this city on the Incomati water resources, not freeing up any water.
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Fig. 7. (a) Satisfaction of future requirements with reduced priority for water transfers. (b) Satisfaction of future requirements with reduced volume for water transfers.
est priority). Run 5 halves the amount of water transferred (from 132 to 66 Mm3/a), while retaining its high priority. The results are shown in Fig. 7a and b. Assigning a low priority to the interbasin transfer improves the satisfaction levels for agriculture and urban requirements due to releases from the Nooitgedacht and Vygeboom dams, but the transfer itself suffers a decrease in satisfaction to 57%. If the amount of water transferred is halved, the improvement in satisfaction is slightly more for irrigation and urban use, even though the transfer retains its highest priority, and can satisfy the reduced demand for water to be transferred for 90%.
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Fig. 8. (a) Satisfaction of future requirements with increased irrigation efficiency. (b) Satisfaction with half of sugar cane swapped for nonsugar cane.
The increase in irrigation efficiency results in a significant gain in the satisfaction levels of irrigation in both countries. Urban requirements in Swaziland also benefit significantly while they remain static at an acceptable 97% in South Africa. The swapping of sugar cane areas for non-sugar crops leads to improved satisfaction levels for irrigation and urban requirements only in Swaziland.
6.3. Irrigation: increasing efficiency and swapping crops Model runs 7 and 8 deal with irrigated crops. Run 7 simulates a situation whereby the irrigation efficiency of all irrigation systems in the catchment is increased to 90%. Note that the Interbasin Transfer from Sand River dam in Swaziland is now reduced, since the area irrigated now requires less water. Model run 8 assumes that half of the area that is assumed to be under sugar cane in the future is converted into less water-demanding nonsugar cane crops. The results are presented in Fig. 8a and b.
Fig. 9. Satisfaction with reduced water transfers, higher irrigation efficiency, crop swap and Class C IFR.
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6.4. Combined measures Model run 9, finally, combines three measures: halving the interbasin transfer in the Upper Komati, increasing the irrigation efficiency to 90% and converting half of the sugar cane area to non-sugar cane crops. Fig. 9 shows the results. 7. Conclusions and recommendations It is evident that the implementation of the Komati Basin Development Project, with the construction of Driekoppies and Maguga dams, resulted in the improvement of water availability for both Swaziland and South Africa. However, this may change in the future, when the water required will outstrip the ability of the catchment to supply it equitably and sustainably. Water shortages can be expected in future in some parts of the catchment as development approaches that allowed by present agreements. Releasing water from the dams in the Upper Komati will go a long way in relieving the shortage of water in Swaziland and the Lower Komati. It must be considered whether it is possible to reduce the water transfers from Nooitgedacht and Vygeboom dams to 62 Mm3/a, for instance through investments in cooling technologies that use less water. This also implies that in the continuing negotiations concerning the utilisation of the water resources in the Incomati water transfers in the catchment will have to be isolated as a unique type of water use. All concerned parties may then be able to discuss their differences over the priority of one distinct use over another. Reducing afforestation levels has a negligible effect on the satisfaction of water demands for other users (Nkomo, 2003). The study has not shown that reducing afforestation would yield any significant amounts of water for other uses. Thus the measure of cutting back on afforestation may perhaps cause more harm than good to the economy given that forestry contributes significantly to employment. Decreasing environmental water requirements from Class C to Class D leads to more violations of cross-border flows although they avail more water for other uses (Nkomo, 2003). Class C requirements may be more appropriate to maintain because they may prevent further degradation of the riverÕs ecology. Nevertheless it is suggested that instream flow requirements at appropriate river reaches be comprehensively determined before a final agreement is reached on the Incomati Basin. Reduction of sugar cane in favour of other less waterhungry crops would result in increased water availability in the long term. Increasing the efficiency of irrigation results in slightly higher satisfaction levels for all users. However, the implications of higher irrigation efficiency
are that the yields and hence consumptive water use by crops increases. Due to the increased efficiency, return flows will also decrease. The repercussions for downstream users who rely on return flows need to be addressed. The city of Maputo in Mozambique is an especially delicate case since it relies on return flows from irrigation in Swaziland along the Umbeluzi river. It is clear from the results presented in this paper that a combination of measures will be required to ensure equitable and sustainable water utilisation in the Komati catchment. Implementation of the measures would require careful negotiations in an open and well-informed environment, and will have to be agreed by the two riparian countries. In addition, all other interested parties, such as the various water user groups and downstream Mozambique need to be consulted. In the negotiations, important roles will have to be played by catchment management agencies and river boards in Swaziland and South Africa, as well as by the Tripartite Permanent Technical Committee of the three riparian countries. The Waflex model, as the JIBS model, may play a positive role in facilitating such negotiations, by means of estimating the effects of various combinations of measures. Such models bring out important water management issues, may trigger technical cooperation and promote understanding of each otherÕs interests and viewpoints. The following recommendations are made: • Given that the results of the Waflex model differ from those of the JIBS model, it is suggested that further verification of the Waflex model be done before the results can be taken as conclusive. • It is evident that a combination of measures would be necessary in order to improve the future availability of water for irrigation and domestic use downstream. The release of water from the Upper Komati and increasing irrigation efficiency seem particularly promising. • Reduction of sugar cane in favour of other less waterhungry crops is an option which may result in less problems of water shortage in the long term. If higher value crops are chosen (e.g. horticulture, flowers, etc.) there may also be an economic benefit.
References Carmo Vaz, A., Van der Zaag, P., 2003. Sharing the Incomati waters: cooperation and competition in the balance. UNESCO—IHP Technical Document/PCCP series number 13. UNESCO, Paris. DFID, 2002. Handbook for the Assessment of Catchment Water Demand and Use. Unpublished draft, Department for International Development in collaboration with Department of Water Development. H R Wallingford.
S. Nkomo, P. van der Zaag / Physics and Chemistry of the Earth 29 (2004) 1309–1317 De Groen, M., 2002. Water Resources Modelling: Lecture Handouts, Department of Civil Engineering, University of Zimbabwe. JIBS, 2001. Joint Inkomati Basin Study Phase 2. Consultec in association with BKS Acres. Final Draft, April 2001. Natsa, T.F., Nyagwambo, N.L., Van der Zaag, P., 2000. Comparing alternative surface water allocation scenarios for Zimbabwe. In: Proceedings 4th Biennial Congress of the African Division of the Intl. Ass. of Hydraulic Research ÔConserving and Sharing Water Resources in a Water Scarce EnvironmentÕ. Windhoek, June 7–9. Nkomo, S.M., 2003. Water resources modelling in the Komati Catchment shared by South Africa and Swaziland. Unpublished MSc thesis. University of Zimbabwe, Harare.
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Savenije, H.H.G., 1995. Spreadsheets: flexible tools for integrated management of water resources in river basins. In: Modelling and Management of Sustainable Basin-scale Water Resources Systems. IAHS Publications no. 231, pp. 207–215. TIA, 2002. Tripartite Interim Agreement between Mozambique, South Africa and Swaziland for co-operation on the protection and sustainable utilisation of the water resources of the Incomati and Maputo watercourses. Johannesburg, 29 August 2002. Waalewijn, P., 2002. Squeezing the cow: perceptions and strategies of stakeholders, concerning river basin management in the Lower Komati River, South Africa. Unpublished MSc thesis. Wageningen University, Wageningen.