Setting standards for draw-down capability at Scottish Water’s Reservoirs

With 270 large raised reservoirs, Scottish Water is the largest owner of reservoirs covered by the Reservoirs Act 1975 in the UK. Although draw-down capability is considered by Inspecting Engineers at statutory inspections, Scottish Water had not established a policy on this matter.

In order to establish best practice, Aecom was commissioned by Scottish Water to study and review current draw-down capacity for their impounding reservoirs, and to propose a standard to adopt for draw-down rates to meet maintenance, precautionary and possible emergency requirements.

This paper reviews current standards for reservoir draw-down proposed and adopted in the UK and overseas. These standards vary over a considerable range. Within this range, draft criteria have been developed for adoption by Scottish Water (SW). These have been determined by considering both risk-based and practical considerations relevant to Scottish Water’s reservoirs.

Following an initial review based on limited data, further assessment of draw-down capability is in hand to understand the extent of upgrading required to meet the proposed criteria.