Between a rock and a wet place: What is the impact of the drought on groundwater resources in the Western Cape?

This article, by Marlese Nel, Groundwater Science Communicator, is published as follow-up to the recent GWD Drought Symposium hosted at UWC, 2 November 2018

The current drought has left immense stresses on our water resources in various parts of the country, and especially in the Western-, Easter- and Northern Cape. It was easy to see the impact on our surface water resources by the daunting pictures of especially the Theewaterskloof Dam when it reached a level of only 11% capacity. As the possibility of Day Zero crept closer, more and more individuals, businesses and even local government hastily turned to groundwater use. This led to an unprecedented increase in boreholes being drilled in the Western Cape.  And in many cases, this “back door” water supply source has kept the front door open for businesses to stay economically feasible, for hospitals to secure essential services and for municipalities to continue to deliver water to its residents.

This increased demand for groundwater supply inevitably led to people asking questions; like ‘Will we destroy the groundwater source?’, ‘How much water can we abstract?’ and ‘Is the resource resilient to the drought?’. Very opposing views on the potential impact of the increased groundwater abstraction were publically expressed by various specialists. In this regard, the Department of Water and Sanitation imposed a 45% reduction in domestic and Industrial groundwater use and a 60% reduction in Agricultural groundwater use in Government Gazette 41381 on 12 January 2018 for the Breede Gouritz and Olifants Doorn water management areas in the province.

Which led to this one-day symposium, hosted by the Western Cape Branch of the Ground Water Division of SA (GWD). The only way to determine the extent of the impact of the drought on the groundwater resources is to have monitoring data; the hard numbers – no speculation of whether water levels dropped because of the drought or whether the amount of rainfall had an influence or not. To eliminate any speculation, the first session of the symposium was aptly titled “Show me yours, and I’ll show you mine”; referring to data sharing of course.

Dr Jaco Nel, Deputy Director of the Institute for Water Studies at UWC, and also the Chair of the Western Cape Branch of the GWD, opened the symposium with a question: Do we need to limit the use of groundwater in drought periods, or do we continue to use it?

Mr Fanus Fourie from the Department of Water and Sanitation: National Planning Directorate shared a statistical perspective on the monitoring data before and after the drought in the Western Cape. The lowest water levels ever measured (from 2008 to 2018) was recorded in June 2018, and levels are starting to recover from that level. Whether these lowest water levels represent a real impact largely depend how we define where exactly the bottom of the aquifer is.

Various hydrogeological consultants in the Western Cape not only attended the day, but also presented very recent and/or current data from groundwater resource assessment studies they are involved in. Some of the comments and conclusions about the impact of the drought on groundwater that all agreed on are the following:

  • There is no drought impact on groundwater resources, but definitely a drought signature in how the aquifers respond to the change in precipitation.
  • The drier cycles of 2003-4, 2011-12 are showing similar signatures as 2015-18.
  • Groundwater recharge processes are different during the drought conditions, compared to “normal” precipitation.
  • In 2018 we still experienced a below average rainfall season in large parts of the Western Cape, resulting in the drought signature still evident in the current groundwater level data.
  • The data shared at the seminar suggested that large users of groundwater with monitoring data and continuous evaluation of the data were able to supply groundwater through the drought period without any significant impact on the water level trends.
  • Although some good data available with private consultants and their clients, very limited data is available to DWS to assess the impacts of the drought or for researchers/other consultants to build upon.

Ms Candice Lasher-Scheepers, Principal Professional Officer, Geohydrology at the City of Cape Town’s Bulk Water Supply Department announced an initiative by the CoCT and also pledged their commitment to put all groundwater data from any previous studies in the Metropole on the CoCT website to be accessible to any interested party. This will ensure that future studies do not duplicate previous ones, that it is easier to collaborate data and compare historical trends with current trends and also that future hydrogeological projects use the same set of information as a starting point.

Apart from sharing data, the second session of the day was titled ‘Surprise Surprise!’ and contained talks on unexpected revelations some of the attendees encountered during drilling or monitoring of aquifer systems. This session induced some interesting discussions and challenged some of the fellow hydrogeologists’s thinking about the hydrogeology of some areas in the Western Cape.

Various alumni of the EWS Department at UWC attended and contributed to the symposium, which is an indication of the successful hydrogeology mentoring and training students receive here, preparing them for the consultancy environment and to make a contribution to the knowledge pool of groundwater scientists in the Western Cape, and even in the rest of South Africa.

PICTURES:

  1. Programme front
  2. Two UWC-IWS students attending the symposium – Mr Angelo Johnson (left), current MSc Hydrogeology student and Mr Adolf October, UWC Alumni, GPT Consultants