Update on Usk Water Abstraction

Guy Mawle has written the following report on how things stand on revisions to major water abstractions from the Usk. He helps the Wye & Usk Foundation (WUF) on the Usk Wye Abstraction Group (UWAG). 

This is the information Guy has had as part that Group from Dwr Cymru Welsh Water (DCWW):

• Old Prioress Mill Pumping Station, Usk, is no longer running (stopped 13th July 2020)
• New Prioress Mill P.S. started early Sept 2020
• New Station shutdown 5th Oct to 4th November to tie into both mains
• New Prioress Mill P.S. commissioning was from Sept to 21st Dec 2020
• Further shutdown to swap valves is required early 2021
• Llantrisant P.S. will be stopped December 2021

And for the new reservoir release valves:

• Usk reservoir valve scheme is ongoing and due for completion Sept 2021
• Talybont reservoir valves are in place
• River Usk control system design and build scheduled for April 2021

The following information is how the situation looks:

DCWW's new infrastructure now appears to be set up in the lower river, though their abstractions have been compliant with their new licences from NRW for some time, improving the river flows downstream of Prioress Mill at Usk and for fish migration, though the full UWAG agreement, from 2014, remains to be implemented. 

For the Usk, the key organisations contributing to the UWAG agreement are DCWW, the Canal & Rivers Trust and the Wye & Usk Foundation. NRW, whilst closely involved, has taken an independent view, as the regulator. Nonetheless, it cited the UWAG agreement when consulting on DCWW's new licences.

It may be that 'environmental releases' of different types from the upper reservoirs, as proposed in the UWAG agreement, will be trialled in 2021. There has been no confirmation of this. Since DCWW now has new valves in place at Talybont, it is possible that 'spate support releases' from this reservoir at least will be piloted. 

'Spate-support releases' were devised by John Lawson (when working for WUF) to counteract the spate-clipping effects of impounding water behind the various reservoir dams. The releases will extend the spate period and hence the opportunities for fish migration. These and other environmental releases should benefit the wider ecology of the Usk as well as fish.  NRW, whilst recognising the environmental benefits, has not made the provision of water for such releases by DCWW, a legal requirement. Rather NRW decided that the impact of the reservoirs on downstream flows, including spate clipping, should be treated as natural. Nonetheless, DCWW may make environmental releases if there is water available after their own needs have been met.

DCWW may also make regulation releases from the upland reservoirs, usually during a dry spell, to boost water levels in Llandegfedd Reservoir. While the water from regulation releases are abstracted at Usk, they do improve flows through the river upstream, as happened in May/June and again in September 2020. Guy has asked what plans DCWW has for releases, regulation and environmental, from April this year but had no response as yet.

The licence for the Monmouth & Brecon canal abstraction at Brecon by the Canal & Rivers Trust remains to be resolved with extensive computer modelling by a technical group. The canal will need support through further releases by DCWW from Usk reservoir to ensure satisfactory flows downstream of Brecon, as defined by NRW.  Flows in the reach downstream of Brecon are currently unsatisfactory, though the abstraction is legal under historical legislation. The canal will still have to close to navigation occasionally  in dry years. The canal's licence, to be determined by NRW, must be in place by the end of 2022.