|Development of water resource management tools to manage salinity in the Berg and Breede catchments in the Western Cape
|Expanded Title:||This research entailed a workshop, which was a unique event combining four programmes of the research into one discussion event. The four programmes were as follows:
• The WRC project tasked with researching the effect of land-use change on salt production and looking for possible measures to regulate land use (Projects K5/1849 and K5/1503).
• The development of tools that can be used by water managers to lower the amount of salinity redistribution in catchments.
• A discussion of the contribution made by a bilateral programme with Germany to the research and ways to take this collaboration forward.
• The culmination of the knowledge gained in tools for the management of salinity.
At this workshop, the data that were gathered during the course of these research projects on dryland salinity were considered for defining the criteria to be used in land management, with the principle aim of reducing the salinity load that reaches the Berg River through saline seep. A wide range of measurements and modelled results were therefore tabled to be considered as directives towards a salinity management strategy for the Berg River catchment. The issues discussed are crucial to the general water supply (especially water quality) in the Western Cape. If the farming community can help to reduce the saline seep towards the river, less water may be needed from our dams to maintain the river system in the summer.
It further was important to look into which tools should be made available to water managers in these catchments and to hear from water managers and stakeholders what their needs were. The stakeholder involvement was also discussed in detail.
The results are divided into two groups of tools, namely (1) outcomes of the workshop and consultation process, and (2) the modelling outcomes and the proposed mechanisms for continued learning and discussion through workshops.
In the general discussion there were three main concerns:
• The dissemination of the information generated.
• Which aspects of the research should be continued?
• Finding money/sponsors for continued monitoring.
The discussion about the continuation of monitoring led to the following:
• Critical measurement in terms of borehole monitoring, climate monitoring and water quality should continue.
• In a sense, the new WRC research programme tasked with tools (K5/2063) for water managers should define the critical measurements needed for adequate saline water management in the larger catchments.
• The definition of observed processes in the Berg River catchment should be programmed into the JAMS/J2000 model. This was done for the salt flow path and the effect of contour banks on runoff.
• At least the critical measurements that will help us in the testing and development of tools for water managers should continue.
The history of agriculture in the Berg River catchment was discussed. Points were raised about when the salinity became a problem. The origins of salinity were explained (also indicated by previous research) as:
• Salinity from the recent influence of the sea in the form of dry aerosols and generally indicated as recharge.
• Salts from geology, mainly as continued weathering of the Malmesbury shales. However, this was indicated to maintain and play a minor role in the occurrence of salinity.
• Redistribution of salinity in the catchment as a result of water and wind transport.
The comments related to the ability to model the salt recharge as a special addition to the J2000 model.
The modelling entailed two major processes, namely (1) the hydrological modelling approach, through which the dryland salinity problem, as influenced by land-use change, could be indicated, and (2) a modelling expert system approach, through which the quality of the water in the Breede River could be managed. The decision was also made to test the hydrological model for the three scenarios outlined below:
Scenario1: Simulating the effects of alternative land-use/vegetation types in riparian zones.
Scenario 2: Simulating the effects of alternative land-use/vegetation types along contour banks.
Scenario 3: Simulating the effects of alternative land-use/vegetation types in areas that exhibit high salt storage in the regolith zone.
The workshop was very productive as a number of new ideas and concepts surfaced.
The stakeholders envisaged that the research that led to this report, as well as this report, should be published as a book/manual for land-use management.
A clear programme for setting up and managing the K5/2063 research programme was developed, linking the completed research to tools/knowledge that could be of value to water managers.
The mechanisms in water movement in the catchment and the consequent depth of the water table during a year are illustrated quite well. It also is clear that the more annual vegetation, or the larger the cover in terms of annual vegetation, the more the excess winter water in the system is being taken care of, and the deeper the occurrence of the perched water table during summer. A deeper summer water table implies a smaller threat to the river system, as fewer salts will potentially reach the river during the summer months, when a low-flow is maintained in the Berg River.
The detailed experiments carried out and observations made indicated a number of interacting events that contribute to dryland salinity and summer saline seep. The one event that can be singled out, however, is cultivation practices. It was indicated that cultivation practice has a large impact on the ratio between overland flow and infiltration.
Overall, the results of the hydrosalinity process-based modelling of the Sandspruit catchment with the JAMS/J2000-NaCl model indicates that there is potential for the model to be used as a water and salinity management tool in the catchment
|Document Type:||Research Report
|Document Subjects:||Water Resource Management/IWRM - Hydrogeology
|Document Keywords:||Hydrology, Municipality, Nutrient Management, Water Quality
|Document File Type:||JPG
|Research Report Type:||Standard
|WRC Report No:||2063/1/14
|Authors:||de Clercq WP; Bugan RDH; Jovanovic NZ; Visser T; de Villiers J; Smithers JC
|Organizations:||Department of Soil Science, University of Stellenbosch; Natural Resources and Environment, CSIR
|Document Size:||9 KB
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