WP11:

South Africa catchment study


Overview:

The primary catchment for WP11 research is that of the Thukela River where both extensive smallholder and large scale commercial irrigated agriculture exists. The catchment provides a pilot site where measured downstream responses can be used to develop, test and verify available modelling systems along the lines of that adopted by Andersson et al (2009).For this catchment,the WHaTeR project will build on earlier research conducted in the area, for example through the Smallholder System Innovations in the Integrated Water Resources Management project undertaken in the Potshini subcatchment of the Thukela. This project generated substantial knowledge and experience that will be of great benefit to the RTD activities of the WHaTeR project.

This Work Package will be undertaken in close collaboration with the consortium partners, SUA and SRC in particular. The methodology is to identify suitable WHT sites, drawing on the GIS based approaches of De Winnaar et al (2007) and Mbilinyi et al., (2007), within the selected study catchment and then to assess the potential impact (positive and negative) on EG&S, including water resources impacts through the application of agro-hydrological modelling system, at a hierarchy of spatial and temporal scales in catchments representative of key climatic regions in Sub-Saharan Africa.

WHT systems are small spatial scale interventions that capture short time period rainfall and runoff events and thus have the potential to alter the partitioning of rainfall at the land surface. At different spatial and temporal scales and depending on the extent of uptake, this may have both positive and negative impacts on the generation of ecosystem services and the trade-offs and feedbacks in both upstream and downstream areas. Thus, it is critical to be able to assess the benefits, impacts and potential trade offs of WHTs at a range of spatial scales including those at which large scale commercial irrigation is present. It is also important to consider that ecosystem services result from processes of the hydrological cycle in its entirety, including evaporation and transpiration, infiltration, soil moisture, groundwater recharge and runoff generation as well as streamflow. In particular, the production of agricultural products (biomass) through the use of green water flows is a focus of attention and the simulation of sediment and nutrient yields provides an additional area of innovation. We will then assess the sites identified and consider these explicitly in the configuration of an appropriate agro-hydrological modelling system. Appropriate systems must be applicable at spatial and temporal scales at which WHT systems operate and should include crop estimation modules i.e. agro-hydrological, as crop yield estimates can be compared to historical and current crop yield information, provide an additional verification means and a clear link to assessing the potential EG&S arising from green water flows.

The main research questions addressed by WP11 are:
• What are the upstream-downstream implications of uptake of WHTs?
• How do the various scales interact from field to river catchment with regards to the hydrological functioning and ecosystem services under conditions of WHT uptake?
• What are the trade-offs between water for food and large scale irrigation and water for the environment at field, multiple farms (landscape) and catchment scales under conditions of WHT uptake?

The methodology will be using scenario analyses coupled with global to regional water balance and trade models, in close consultation with project partners and stakeholders to ensure relevance. In particular the outputs will serve for policy and decision support outputs in Work Package 3.


Objectives:

The main objectives of WP11 are:
• Analyse benefits, impacts and potential trade offs of WHTs on hydrological functioning and ecosystem services, based on upstream-downstream interactions (in cooperation with Work Package 4 and 11)
• Develop methods for determining additional ecosystems service synergies and/or trade-offs emerging from WHTs for multiple scales using a catchment as starting point (jointly with Work Package 4 and 12)
• Develop methods and tools to asses the impacts of WHTs on catchment water quantity and quality, including upstream and downstream interactions (jointly with Work Package 4 and 12)
• Provide inputs into the Work Packages 2, 3, 5, 6, 7 and 8

Deliverables:

D11.1) Factsheet South Africa: A factsheet will be produced describing the first results on the RTD activities on water harvesting technologies and their impacts and potential tradeoffs based on upstream-downstream interactions. [month 24]


D11.2) Synthesis report with GIS model and guidelines: A synthesis report will be written on the impacts and potential trade offs of WHTs based on upstream-downstream interactions at catchment level. The synthesis includes a GIS model with guidelines and standards for sustainable WHTs. [month 42]


Lead Institution:

University of Kwazulu-Natal (UKZN)


WP Leader:

Graham Jewitt
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