Water & Wastewater Treatment Magazine
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28 | JANUARY 2018 | WWT | www.wwtonline.co.uk dominant 8-year cycle and, when strong, gives us wetter winter conditions. Anyone who experienced the so-called 'conveyor belt' of storms hitting the UK in the winter of 2013/14, resulting in wide-spread - ooding across the country, has seen the in- uence of the NAO. A sensible question to ask at this point would be: "if we know that the NAO a‡ ects UK weather, why haven't we been using it more in our water resource planning?". One answer is that the NAO pattern is oŠ en hidden by noise. Rainfall is a‡ ected by countless in- uences, from solar radiation, to cropping rotations, to the cereal farming practices of the biscuit industry. All this noise hides the subtle in- uence of the NAO's 8-year cycle. Luck- ily for water managers, more and more research is agreeing that certain ground- water resources in the UK are particularly adept at ignoring noisy, Rich Tea-driven rainfall and responding to that near- decadal cycle. While this is still a relatively new area of research, connections between climate and groundwater (climate teleconnec- tions, if you want to be technical) have been investigated in a handful of loca- tions across the UK. A great example of a groundwater resource's ability to absorb the NAO signal can be found in the Heath- lanes borehole groundwater level record in the Shropshire permotriassic sand- stone. Heathlanes shows a clear pattern that repeats every 8-10 years, appearing to be stronger than any seasonality in the records. The latest climate teleconnec- tion research is trying to explain exactly why particular groundwater resources are adept at reproducing the NAO signal, and why others show little to no repeating patterns other than the usual seasonality. If we can have con— dence that the NAO is driving the cycles we see in the Heath- lanes data, then we may be able to say, to some degree of con— dence, what state this groundwater resource is going to be in 8 or 16 years' time. And what is true for Heathlanes, could be true for many other groundwater resources across the UK. Presently, there is an assumption in many assessments of water resource resil- ience that understanding annual changes in groundwater recharge is suš cient for long term management of that resource. This makes sense as, anecdotally, we know that a lot of variety happens on a yearly basis: wet winters and dry sum- mers. However, this premise means that the in- uence of any longer-term climate cycle is oŠ en ignored. Metrics such as Average Annual Recharge and Average Annual Rainfall all assume that annual cycles are the most important aspect of water resource variability. For the Heathlanes borehole record, surely any calculated Average Annual Recharge used for assessing groundwater availability should be taken with a pinch of salt. Climate change is naturally taken into account in assessments of future proof- ing groundwater resources but these are typically an understanding that resources are to become more subject to drought (and therefore less available for supply) in the future: a downward trend. What the latest climate teleconnection research is ultimately telling us is that there is a component missing from this model. We have annual - uctuations and we have a general downward trend from climate change, but without the additional inclu- sion of an 8 year cycle we are potentially missing opportunities to more eš ciently utilize our groundwater resources for hu- man and environmental purposes. The Ofwat 2020 report highlights in- novation through 'solutions to long-term challenges' and 'alternatives to traditional engineering approaches'. These goals provide a perfect opportunity to develop and utilise understanding of climate tel- econnections for improved water resource management eš ciencies. The potential of this new area of research is clearly signi— - cant, and once the study of climate and groundwater teleconnections has matured to the point that it can be a useful tool for predicting groundwater availability, the industry will be primed to adopt new and more intelligent approaches. The knowledge: water resource management