Matthew Pitts Catchment Strategy Manager Water plc

the umbrella body of the rivers trust movement where there’s water, there’s life Restoring the

Matthew Pitts, Catchment Strategy Manager, Simon Hunter, Head of Operations, Bristol Avon Rivers Trust

21st November 2018 Introduction

• Bristol Water and the River Chew • WFD and HMWB – an opportunity (and the 25 Year Plan)

• Impacts on the river

• Solutions, Trials and Monitoring

• Stakeholder consultation and concerns

• Monitoring • Conclusions and Looking Forward

• BART and the Chew Strategy

bristolwater.co.uk Bristol Water and the River Chew

• Reservoir opened in 1956 • Licence – provides for compensation flow downstream – 17 mills! • Vital component of Bristol and regional water supply • Catchment management in upper catchment • Reservoir is SSSI / SPA • WFD status bristolwater.co.uk • Eel / elver migration • Flood risk concerns downstream WFD and HMWB – an opportunity

• AMP6 - First National Environment Programme (NEP) for Bristol Water

• Chew and Reservoirs - assess impacts on downstream river water bodies -> trial mitigation measures -> implement adaptive management (over two AMPs)

• FANTASTIC OPPORTUNITY!

• Multiple benefits – eels, flood risk, fish, water quality • Build on years of research – Petts & Thoms 1986 • Partnerships • Community engagement • Stimulus for further improvements • BUT Limits to what BW can achieve alone

Pics of river, site visit with EA Chew been subject of research – Geoff Petts etc in 70s? bristolwater.co.uk Impacts on the river

• Modelled naturalised flow series, IHA / UKTAG Guidelines for River Flow • Flow impacts • Reduced flow variability and magnitude, except very low summer flows (note scale below) • Reversed seasonal pattern of flows – compensation for mills? • Reduced spate magnitude and frequency – spills only 2 in 3 years, no variation between spills • Attenuates some spates – slower rate of rise, increases duration – performs flood risk function • Abrupt changes in compensation flow • DOES NOT meet UKTAG requirements (annual minimum flow, flood flow, spring flow elevations, late summer elevations, autumn/winter elevations)

Chew Valley Reservoir current licence (Ml/d) Naturalised flow (without Chew Valley Reservoir) (Ml/d) 20 60

50 15 40

10 30

20 5 10

0 0 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Impacts on the river

• Low winter flows and increased siltation have affected the habitat quality of the river as indicated by the abundance and diversity of invertebrates in the river

Mayfly nymph

Olive

Adult mayfly Stonefly nymph Impacts on the river

• Due to the regulated flows and poaching by cattle, silt has accumulated in the upper river, smothering spawning gravels • Also accumulated algae on spillway • Due to the reservoir river has also lost larger gravels

UPSTREAM

Downstream of the reservoir – lots of silty clay sediment, channel is over-wide - acting more like a linear pond.

Cattle poaching – adding to silt load in river DOWNSTREAM Downstream

Upstream of the reservoir – narrower channel, faster flows, exposed gravels Impacts on the river

• 400m reach between spillway and compensation discharge – no regular flow since 1956!

Below the reservoir spillway

From the bridge by the pumping station Upstream of the current outfall Change Compensation Flows

Chew Valley Reservoir current licence (Ml/d) Naturalised flow (without Chew Valley Reservoir) (Ml/d) Chew Valley Reservoir trial (Ml/d) 20 60 20

50 15 15 40

10 30 10

20 5 5 10

0 0 0 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

• EA licence variation – can vary flows provided minimum flow maintained and same total annual release Short duration spate flows

• Short duration autumn ‘flush’ releases from the reservoir – not at times of high flow or reservoir spill – designed to introduce otherwise absent flow variability

High flow release from reservoir (200Ml/d) High flows downstream of Pumping station (200Ml/d) Relocate compensation discharge River Restoration Restoring The River Chew

bristolwater.co.uk Stakeholder Consultation - Concerns

• Issued letter explaining proposals, then held community meeting in October. Lots of interest….concerns:

• Effects of compensation flow change on flood risk – will the reservoir fill more quickly, spill longer/more frequently, effect of higher comp flow in winter when res no spilling

• Effects on water levels and fishing / habitats/ ecology

• How will we monitor and measure success?

• Agreed to amend compensation flow profile and go forward

• Reconvene in six months to review results – adaptive management

• Need more EA involvement – WFD / credibility / Chew Valley Reservoir Revised Trial (Ml/d) enforce Farming Rules - remove livestock from river 20 • Long terms commitment by Bristol Water - 2025

• BART – organise supplementary citizen monitoring – 15 Riverfly, fish catches

10

5

bristolwater.co.uk

0 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Monitoring

• Continued invertebrate survey at established sites (spring/autumn) – continues long EA dataset

• Sediment survey

• Channel x-section survey / flow gauging / velocity profiling – habitat availability and diversity

• Fixed point photography

• EA fish survey (next survey summer 2019)

• Water quality

• Riverfly and anglers catches – in association with BART

• WE WILL REVIEW TRIALS IN CONTEXT OF MONITORING RESULTS ON ANNUAL BASIS – RECONVENE COMMUNITY STAKEHOLDERS Conclusion and Looking Forward….Chew Catchment Strategy • On track to deliver multiple benefits from NEP work - locally • BUT working with others, can NEP work be a stepping stone or ‘seed’ project to provide benefits at catchment scale – connect people with their environment? • Loads of interest in the River Chew already – Flood Forum, angling clubs, websites – capitalise ?? • BW - £50k, BART - £15k, EA - £25k +£120k x 3 – others to be approached based on workstream interests/benefits

bristolwater.co.uk Conclusion and Looking Forward….Chew Catchment Strategy • How does this help Bristol Water ? • NEP requirement • Business Plan - social contract…. ‘we are committed to understanding our local communities needs beyond water so we can provide both social and economic benefits to your local areas.’ • Customer support or increasing environmental resilience

bristolwater.co.uk Matthew Pitts Catchment Strategy Manager

Bristol Water plc Road, Bristol, BS13 7AT Direct +44 (0) 117 934 1166 | Mobile 07500 917 629 | Email [email protected]

Bristol Water plc Registered Office Bridgwater Road Bristol BS13 7AT

bristolwater www.bristolwater.co.uk