Run-of-river hydropower in the UK and Ireland: The case for abstraction licences based on future flows

Run-of-river hydropower in the United Kingdom (UK) and Ireland is a small but vital component of renewable electricity generation that enhances grid diversification and resilience, contributes to the net-zero emissions targets, and provides local community benefits. Planning approval by environmental regulators for hydropower water abstraction is based on the abstraction licence conditions (ALCs) that dictate when and how much water may be taken from a given stream location. Although ALCs for non-environmentally sensitive rivers vary across England, Wales, Scotland, Northern Ireland, and Ireland, the impacts of these variations on power generation are not fully understood. Here, we investigate how ALC variations across the UK and Ireland have historically impacted water abstraction and power generation and might continue to do so under future climate conditions. Specifically, we apply five distinct ALCs combination sets, as laid out by the five environmental regulators in the region, to historical observed streamflows and future projected flows (modelled for the Representative Concentration Pathway 8.5 scenario using the EXP-HYDRO hydrological model), at 531 hydropower sites across the UK and Ireland. We then calculate the daily water abstraction potential for each hydropower site and the collective power generation potential separately for Great Britain (GB) and the Island of Ireland (IoI). Our results show that the ALCs that permit greater use of lower flows allow for more power generation than those that enable abstraction during high flow conditions. The most optimal combination of ALCs for power generation, when compared to those currently in use, increases future generation potential by 30.4% for GB and 24.4% for the IoI, while maintaining environmental protection as per the Welsh guidelines. Our results suggest that ALC policy and regulatory reforms are needed to provide optimal use of future streamflows for hydropower generation while ensuring protection for the environment is maintained

Impacts of climate change on future water availability for hydropower and public water supply in Wales, UK

Study region: Wales, United Kingdom. Study focus: Climate change is predicted to have a large impact on the hydrological regimes of Welsh rivers. However, its influence on the abstraction capability of key sectors, such as public water supply (PWS) and hydroelectric power (HEP), is not yet fully understood. We use the Soil and Water Assessment Tool (SWAT) to generate future (2021–2079) streamflows under a worst-case scenario of greenhouse gas emissions (Representative Concentration Pathway 8.5) at two catchments in Wales, the Conwy and Tywi. SWAT streamflow output is used to estimate total unmet demand for PWS and changes in generation characteristics for HEP. PWS unmet demand is assessed using the Water Evaluation And Planning (WEAP) system under increasing, static, and declining demand scenarios. Mann-Kendall analysis is performed to detect and characterise trends. New hydrological insights for the region: Under all future demand scenarios, there is increased occurrence of insufficient streamflow to satisfy PWS demand. For HEP, decrease in annual abstraction volume results in a loss of generation potential, despite an increasing number of days that maximum abstraction is reached. Changes in HEP generation and PWS availability are most pronounced in the medium-term (2021–2054), with rate of change slowing after 2060. We provide a novel perspective on future water resource availability in Wales, giving context to management planning to ensure future PWS sustainability and HEP generation efficiency

Measurement of the Production Rate of Charm Quark Pairs from Gluons in Hadronic Z0Z^{0} Decays

The rate of secondary charm-quark-pair production has been measured in 4.4 million hadronic Z0 decays collected by OPAL. By selecting events with three jets and tagging charmed hadrons in the gluon jet candidate using leptons and charged D* mesons, the average number of secondary charm-quark pairs per hadronic event is found to be (3.20+-0.21+-0.38)x10-2