The groundwater debate has to be science-based
Groundwater has been proven over and over to be a reliable, sustainable and cost-effective source of water – when managed responsibly.
On 30 September 2018 we reached the end of the 2017 / 2018 hydrogeological year and now know where we stand before the onset of the next rainy season. We have made it through four years of below average rainfall – yes, the past hydrological year yielded 85% of our average rainfall. Dam levels are sitting at a relatively prosperous 76% and we can face the dry summer with some confidence. However, we should not forget that there is still much recovery to be made – particularly in the agricultural sector.
A series of recent reports have warned of the dangers of using groundwater and the environmental impact thereof. Such articles have appeared regularly since the onset of the drought, but never quote anyone with hydrogeological expertise or experience. It is always botanists, ecologist or somebody presented as a water expert – whatever that may be. I regularly get asked about the validity of these claims – with the most recent article even prompting communications from a friend based in Washington.
It is not easy to give a clear and concise argument why these fears are unfounded and misplaced. The planet on which we live is a large, interconnected ecosystem. I am a specialist in hydrogeology. I study, develop and manage groundwater, and have done so for almost 40 years. On this journey I have learnt much about these connections, but remain focussed on my area of expertise. I find it difficult to synthesise my understanding into short conversations or articles, but have recognised a couple of common misconceptions and concerns.
Possibly the most common misconception is that groundwater is not a renewable resource. The concept of fossil aquifers – aquifers formed under past climatic and geological conditions – and pumping aquifers dry because they don’t get recharged sit comfortably with the layperson. Such aquifers do exist, with the Nubian Sandstone Aquifer in North-eastern Africa being a good example. Water out of this system is being mined on a very large scale with the understanding that it is not being recharged. This was a deliberate decision by the four countries that share this transboundary aquifer system.
There is ample scientific evidence to demonstrate that our aquifers are recharged – and recharged regularly. In the wetter parts of the country recharge occurs every year, even during the drought. In the semi-arid parts of the country – such as the Karoo – recharge may only take place every couple of years after heavy rains. Even aquifers underlying the Namib Desert get recharged when the rivers are in flood. We need to take account of these observations and facts.
In recent times the concept of a groundwater-drought has emerged, which is different to meteorological droughts, hydrological droughts and agricultural droughts. Conceptually this relates to prolonged periods of no or little recharge and seemingly applies to shallow aquifers and water supply. Also, it is argued that groundwater-droughts can occur some years after surface droughts. The good news is that this situation does not (yet) apply to us. After four years of below average rain, groundwater levels have not been significantly impacted. In fact, groundwater levels that I measured last week are 4m higher than during the corresponding period last year.
The second most common argument I hear is that we don’t know enough. Well, the real question is who doesn’t know enough? And if you don’t know enough, who have you consulted that might know enough? Far from arguing that we know everything, there is an army of hydrogeologists in South Africa who know much about groundwater. The 350 members of the Ground Water Division – established in 1978 – are found in government, academia, research organisations and consultancies.
Our profession has a couple of challenges, such as identifying exactly who is a hydrogeologists and who is not, but belongs to one of the closely aligned professions. We also have good hydrogeologists and not so good hydrogeologists. Neither our science nor our industry is perfect, but we do have substance. So before anyone can say we don’t know enough, maybe they should find out what is known and engage with those with expertise in this field.
The City of Cape Town appointed a groundwater consultancy to help them source groundwater from the Table Mountain Group aquifer. This project was initiated in 2002 and has been a stop-start affair, with the drought providing some recent impetus. Much effort has gone into initial groundwater and ecosystem research and defining baseline conditions. The project went through a public participation programme and is guided by a project committee. It is simply disingenuous to claim that the City has not – and is not – doing its homework. The only meaningful way to proceed is to implement a pilot project and monitor hydrogeological and ecological response. We really don’t need more desk-based studies. They won’t tell us anything new.
Should the pilot project demonstrate that our current knowledge is off the mark, then the scheme could either be modified or simply shut down. This will allow the hydrogeological system to recover. Over-use of the Uitenhage Artesian Basin in the early part of the last century – as evidenced by a sharp decline of flow from the Uitenhage Springs – and the implementation of groundwater management and subsequent recovery of the aquifer demonstrates this. Impacts are not going to happen overnight and may take years to manifest themselves. Appropriate monitoring and adaptive aquifer management are important in ensuring that any impacts are within acceptable limits.
Whatever source of water we choose to harness comes with risks and impacts. If we build a dam, we destroy everything within the footprint of that dam and have ecological impacts far downstream, the risk of alien vegetation clearing is that it doesn’t yield as much water as predicted, desalination is energy intensive and threatened by a fragile electricity supply and sharply increasing costs. The list goes on. It is unhelpful to simply say one source is better than the other without considering a range of factors and implications.
There are very well-established protocols applied in environmental impact assessments that will be useful in this regard. These protocols aim to differentiate the significance of impacts as well as their extent, duration, reversibility and cumulative effect. It is of little meaning to say that groundwater abstraction impacts the environment without addressing the afore-mentioned aspects. Similarly, the impacts of developing groundwater need to be compared to those resulting from sourcing a similar yield of water from a dam, desalination plant or other sources – while also considering costs and social benefits. These assessments need to be founded on knowledge, integrity and independence.
We can have detailed arguments about the pro’s and con’s of groundwater use based on different perspectives, knowledge and experience – much of which will only generate hot air. My gripe with the groundwater naysayers is two-fold. As addressed above, what have they done to properly inform themselves about the properties, characteristics and behaviour of groundwater? But more importantly, what have they done to observe and assess the impacts of groundwater use in this country? For example, it is popular to talk about the impacts of California – where groundwater is used at scales unlikely ever to be seen in this country and who have also recently gone through a prolonged drought. But what about Hermanus, Plettenberg Bay, Prince Albert or Villiersdorp? Agter-Witzenburg Valley or the Hex River Valley?
Some 13% of municipal water supply in the Western Cape Province is derived from groundwater, and has been for decades. This supplies some 63 towns and villages in the Western Cape – either in total or partially. This drought is not our first rodeo. So where are these impacts that we are being told to fear? What is the significance of such impacts – if any – and what is the extend, duration and cumulative impact? Instead of continually trying to model and predict the future, we should start by learning from the past.
Notwithstanding the above, the groundwater community don’t help themselves by the impressions they create from the mess at drilling sites. I have been appalled at what I have seen over the past 12 months, with a lack of consideration for the people and setting in which they operate. While exacerbated by the fly-by-nighters, all drillers can make a much better effort to reduce the nuisance of their operation. It is my understanding that these impacts are mostly temporary, readily mitigated and reversible. It would be meaningful to have an assessment of the status of the drill sites around the Steenbras Dam, only six months ago deemed to have been so impactful so as to halt drilling when dam levels were starting to dip under 20%.
Groundwater has been proven over and over to be a reliable, sustainable and cost-effective source of water – when managed responsibly. This caveat applies to all sources of water. It is a renewable resource recharged by rainfall. People of my ilk would love groundwater to be without a downside, but its dispersed nature and the rate at which it can be abstracted dictate the groundwater supply schemes need more care and resources to keep them operational. Groundwater is well suited to supply villages and small towns, but a 10% contribution to Cape Town’s water supply is feasible. It will require appropriate expertise, sufficient resources for development and ongoing operation and maintenance.
Claims that we cannot properly cost groundwater schemes are groundless. They are costed all the time. Sure – there might be unknowns, but not enough to discard the resource as an alternative or additional source of water. The Berg River Dam, initially costed at R 700 million, cost in the order of R2.5 billion to complete. Working within that kind of tolerance would easily allow for the cost of a groundwater scheme to be estimated. The cost of developing equivalent volumes of water from groundwater and desalination showed that groundwater at R 3 million was a far better option than the R 21 million spent on the stuttering desalination option. One example doesn’t provide compelling evidence but does illustrate the point. In my limited experience with unit reference values of water supply, groundwater schemes invariably prove themselves to be attractive. With knowledge, experience and some reasonable assumptions, information about the cost of developing and maintaining groundwater schemes can be included in decision-making processes. We would do best, however, if such information were generated by resource economists.
There is no doubt in my mind that as a society we need to use less water and make better use of the wastewater we generate. There is also no doubt that clearing alien vegetation is an imperative – something we just have to do. The introduction of alien vegetation to stabilise shifting sand was a mistake driven by noble intent, but a mistake nonetheless. I am certain that mistakes will be made in the future, but these can be minimised by avoiding single perspectives. We need to pool our knowledge and consider alternatives in light of cost, environmental impact and societal benefit. DM
Dr Roger Parsons is a hydrogeologist with more than 30 years’ experience. He is the Director of Parsons & Associates Specialist Groundwater Consultantscc and former provincial branch chair of the Groundwater Division. He writes this article in his private capacity
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