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UNESCO-IHE Institute for Water Education, Delft (2012)

Analysis of water allocation in the Komati catchment downstream of Maguga and Driekoppies dams

Mukororira F .

Titre : Analysis of water allocation in the Komati catchment downstream of Maguga and Driekoppies dams

Auteur : Mukororira F .

Université de soutenance : UNESCO-IHE Institute for Water Education, Delft

Grade : Master of Science (MS) 2012

Résumé partiel
Water allocation is a very contentious issue in closing and closed basins. Decision makers normally aim to allocate water in an equitable and efficient manner. Such a case is exemplified in the Komati catchment, shared by South Africa and Swaziland with Mozambique not in the catchment but located downstream. This research aimed at describing the current water allocation, water use and how the cross border flow to Mozambique is impacted. In addition, future development scenarios were tested and how they would affect the water allocation regime in wet and dry years. Analysis of data was carried out for four river reaches of the Komati catchment downstream of Maguga and Driekoppies dams for years 2004 to 2011. Data was gathered through review of literature, documents and interviews with key informants. AWAFLEX simulation model was also set up using the period 2006 to 2011 for the analysis of future development scenarios in wet, normal and dry periods. These were all normal and wet years and represent the period when ultimate system operating rules started operating. For the dry period, a hypothetical scenario was simulated for the Komati river branch only, due to data constraints. The hypothetical scenario includes four consecutive dry years, at the moment when the reservoirs are full. Findings from this study show that the current water allocation practices in the Komati are based on the bilateral Treaty on the Development and Utilization of Water Resources of the Komati between South Africa and Swaziland with Mozambique’s consent provided that 2 m3/s averaged over 3 days (according to the Pigg’s Peak Treaty) is met at the Mozambique border. However, a recent agreement, the IIMA if implemented is supposed to supersede the current Treaty and this will definitely see a change in the water allocation practices of the Komati. This is because the IIMA allows for consumptive water use increase by the three countries including an increase in the minimum flow at the Mozambique border. The main water users are irrigation schemes and water abstractions are measured in 3 river reaches and therefore water can be accounted for and any inefficiency can be attended to. Comparison of water requirement and water abstractions by the users along the river reaches was done. Results show that the users along the Komati river in Swaziland abstract what they demand in 90% of the time. Irrigation users along the Lomati river have higher demands 50% of the time as compared to the abstractions.

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