In around a decade, total demand for water will exceed the available supply globally. This will be a challenging problem for decision-makers and regulators referred to as ‘jaws of death’ by Sir James Bevan, Chief Executive of England’s Environment Agency. London, along with many other major cities across the world, will be severely affected. Putting emphasis on reducing consumers demand will not be enough; this is a lesson we learnt from Cape Town’s 2018 major drought. New supply sources will have to be found along with demand management solutions. Among supply-side options, Inter-basin Transfer (IBT) schemes have received less attention from both academia and industry. The construction of an IBT requires considerable investments and can also have negative impacts on the exporting basin which have to be studied.
To this note, a team of researchers from the UK (HR Wallingford, Newcastle University, and Tyndall Centre for Climate Change Research) provided a framework to be implemented during the planning and designing stage of an IBT. This framework can be used for feasibility studies regardless of type, location, layout, and means of the IBT.
They used this framework to assess the initial climate impact of a hypothetical IBT scheme that will deliver water from the Keilder reservoir in the northeast of England to London in the southeast. They stated: “This choice is informed by the fact that Kielder is the largest reservoir in the UK and is located in one of its least water-stressed regions.”
The proposed framework computes the spatial and temporal distribution of water flow and storage along the catchment area using climate projection for precipitation and potential evapotranspiration (UK Climate Projection 2018; UKCP18). This data is then modeled into a rainfall-runoff model to calculate future inflow time series to determine storage capacity and stream temperature. The proposed framework was evaluated 100 future climate scenarios generated from the driest member of the UK’s Met Office UKCP18 for the donor basin.
Dr. Khadem and colleagues assessed the negative ecological and hydrological impacts of the hypothetical. The impact of this hypothetical IBT was assessed under three transfer scenarios. In the “NoTransfer” scenario, there was no demand for water from London IBT and water from the Keilder Reservoir was utilized within its resource zone. In the “AllYearTransfer” scenario, there was a continuous demand for water from the London IBT throughout each year. In the “WinterTransfer” scenario, the London IBT is operational only in the winter months (i.e. October to March) while delivering the annual water deficit of London.
The Hydrological impact was evaluated by assessing if IBT causes drought in the export basin. The hydrological risk of potential droughts in the Kielder catchment area was higher in the “AllYearTransfer” scenario. In this scenario, this IBT will struggle to keep up with the demand and will result in drought in the Kielder water resource zone. However, transferring under ‘WinterTransfer’ shows there will be no adverse hydrological impact as the donor basin is experiencing high flows. The ecological impact was evaluated by assessing if the change in flow and storage volume will alter stream temperature and destroy the freshwater habitat. In all three scenarios, low stream temperature was predicted with no negative ecological impact on the Kielder basin.
The research team’s findings have successfully proved that an ambitious north-south IBT can resource water from the Keilder reserve to meet London’s deficit by transferring large volumes of water in winter months, even under the driest UKCP18 climate projection. This is not the only option available to decision-makers but this study shows that it is a viable and feasible option to consider, and perhaps a starting point for further analysis. “The current water resource management plan comprises a portfolio of leakage reduction, demand reduction, new groundwater and reuse schemes, and regional transfers. However, if population growth is higher, demand reduction fails to return the necessary benefits, or if the higher standard of drought resilience called for by the National Infrastructure Commission is imposed, then a long-distance IBT may be essential to sustain London’s water supply” said the led author Dr. Khadem.
Journal Reference and Image Credits:
Khadem, Majed, Richard J. Dawson, and Claire L. Walsh. “The feasibility of inter-basin water transfers to manage climate risk in England.” Climate Risk Management (2021): 100322. DOI: https://doi.org/10.1016/j.crm.2021.100322
