Severn Trent Water AMP6 Low Flows Programme: River Noe and River Ashop Low Flow Distribution Assessment Official Sensitive (Sensitive information redacted) 13 February 2020 Severn Trent Water AMP6 Low Flows Programme: River Noe and River Ashop Low Flow Distribution Assessment Prepared for: Severn Trent Water Ltd 2 St John’s Street Coventry CV1 2LZ Report reference: 64116AB R36rev1, February 2020 OFFICIAL SENSITIVE Report status: Final rev1 CONFIDENTIAL New Zealand House, 160-162 Abbey Foregate, Registered Office: Shrewsbury, Shropshire Stantec UK Ltd SY2 6FD Buckingham Court Kingsmead Business Park Telephone: +44 (0)1743 276 100 Frederick Place, London Road Facsimile: +44 (01743 248 600 High Wycombe HP11 1JU Registered in England No. 1188070 Severn Trent Water AMP6 Low Flows Programme: River Noe and River Ashop Low Flow Page i Distribution Assessment Severn Trent Water AMP6 Low Flows Programme: River Noe and River Ashop Low Flow Distribution Assessment OFFICIAL SENSITIVE This document is classified by Severn Trent Water Ltd (STWL) as Official Sensitive and the information contained within is sensitive. Distribution of this document must be restricted and managed within organisations given access to it. If in doubt, please seek STWL’s permission before this document is shared with third parties. This report has been prepared by Stantec UK Ltd (Stantec) in its professional capacity as environmental specialists, with reasonable skill, care and diligence within the agreed scope and terms of contract and taking account of the manpower and resources devoted to it by agreement with its client and is provided by Stantec solely for the internal use of its client. The advice and opinions in this report should be read and relied on only in the context of the report as a whole, taking account of the terms of reference agreed with the client. The findings are based on the information made available to Stantec at the date of the report (and will have been assumed to be correct) and on current UK standards, codes, technology and practices as at that time. They do not purport to include any manner of legal advice or opinion. New information or changes in conditions and regulatory requirements may occur in future, which will change the conclusions presented here. This report is confidential to the client. The client may submit the report to regulatory bodies, where appropriate. Should the client wish to release this report to any other third party for that party’s reliance, Stantec may, by prior written agreement, agree to such release, provided that it is acknowledged that Stantec accepts no responsibility of any nature to any third party to whom this report or any part thereof is made known. Stantec accepts no responsibility for any loss or damage incurred as a result, and the third party does not acquire any rights whatsoever, contractual or otherwise, against Stantec except as expressly agreed with Stantec in writing. Report Reference: 64116AB R36rev1 OFFICIAL SENSITIVE Report Status: Final rev1 Severn Trent Water AMP6 Low Flows Programme: River Noe and River Ashop Low Flow Page ii Distribution Assessment Name Signature Author Adam Sutcliffe, Thomas Brook APEM Checked by Rick Hayes APEM Dan Cadman Reviewed by Paul Daily Revision record: Reference Date Status Comment Author Checker Reviewer Issued to 64116AB 19/03/2019 Draft First draft AS/TB RH DC/PD STWL* R36D1 64116AB Second 23/05/2019 Draft AS/TB RH DC/PD STWL/EA** R36D2 draft 64116AB 07/06/2019 Draft Third draft AS/TB RH DC/PD STWL/EA R36D3 64116AB 04/10/2019 Draft Final draft AS/TB RH DC/PD STWL/EA R36D4 Final for 64116AB 19/11/2019 Final client AS/TB RH DC/PD STWL R36 checks 64116AB 20/12/2019 Final rev1 Final AS/TB RH DC/PD STWL/EA R36rev1 *Severn Trent Water Limited. **Environment Agency Report Reference: 64116AB R36rev1 OFFICIAL SENSITIVE Report Status: Final rev1 Severn Trent Water AMP6 Low Flows Programme: River Noe and River Ashop Low Flow Page iii Distribution Assessment Executive Summary The River Ashop, River Noe and Jaggers Clough transfers are important sources of water to the Derwent Valley Reservoirs. Abstraction at the three structures must cease when inflows reach predetermined conditions, stipulated in the associated abstraction licence. Impact Assessment and Options Appraisal undertaken during AMP5 and AMP6 resulted in recommendations to change conditions on these abstraction licences under normal operation. This report complements those studies, recommending how compensation flows at the structures should be operated under natural circumstances when inflows cannot simultaneously maintain recommended flows in the River Ashop, River Noe and Jaggers Clough. This report does not recommend changes to the operation of these structures under typical climatic conditions. Naturally arising circumstances during which inflows cannot simultaneously maintain recommended flows on the River Ashop, the River Noe and the Jaggers Clough can occur in dry years between late spring and mid- autumn. There is no storage at any of the structures, meaning that during such circumstances, trade-offs may be needed in maintaining the ecology of the three rivers. Historically, support has been provided to the Jaggers Clough at the expense of flows in the River Noe or, less often, the River Ashop. This support has maintained flows in the Jaggers Clough at rates several times greater than those naturally expected in this stream during dry periods and can leave very small flows on the main stem of the Rivers Ashop and Noe. The Jaggers Clough is valued as a brown trout nursery, and as such its importance to the River Noe fishery may be greater than suggested by its size. Even so, analysis of habitat and experience during the very dry summer of 2018 do not suggest long-lasting impacts, and in any case, it is not standard practice to transfer raw water between catchments to support ecology in a recipient waterbody. Moreover, the historic practice of reallocating flows risks of deterioration in Water Framework Directive (WFD) status in the waterbodies downstream. The WFD makes provision for effects of naturally arising low flows, and in the absence of intervention, temporary impacts caused by natural low flows do not constitute a deterioration in status. This may not be the case were STWL to reallocate flows, regardless of the intention behind the reallocation. At the Ashop impoundment, the requirement to cease abstraction into the diversion channel is also problematic operationally. Any water transferred to the Jaggers Clough must also use this offtake. Under natural circumstances in which compensation flows on the Jaggers Clough cannot be met from the Noe and Jaggers combined inflow, the requirement to cease abstraction into the diversion channel can therefore be at odds with that to maintain the compensation on the Jaggers Clough. This report therefore recommends that support to the Jaggers Clough during naturally arising circumstances of low inflow any diversion of flow from the River Ashop to the Jaggers Clough should cease and support to the Jaggers Clough should be sourced from the River Noe in reduced quantity. To avoid rapid changes in flow, reductions should be preceded by a preparatory change implemented when there is sufficient flow in the River Noe to prevent rapid changes in both watercourses. Recommendations for operation of the compensation during naturally arising circumstances of low flows make provision for future changes as prescribed by the Notional Solution at these sites. However, under current provisions: • Once combined baseflows to the River Noe impoundment and Jaggers Clough compensation fall to 18 Ml/d, support to the Jaggers Clough can be reduced to maintain flows on the Jaggers Clough from 10 Ml/d to 6 Ml/d. If this results in temporary baseflow increases above 10 Ml/d on the River Noe these should be passed at the impoundment and not abstracted. • Once flows to the River Noe impoundment and Jaggers Clough fall to 13 Ml/d, support from the River Noe can be reduced to maintain flows on the Jaggers Clough at 2 Ml/d. The effects of any such changes should also be monitored. Report Reference: 64116AB R36rev1 OFFICIAL SENSITIVE Report Status: Final rev1 Severn Trent Water AMP6 Low Flows Programme: River Noe and River Ashop Low Flow Page iv Distribution Assessment Contents 1 INTRODUCTION 1 1.1 This report 1 1.2 Previous studies 1 2 OPERATIONAL CONSIDERATIONS 2 2.1 Abstractions on the River Ashop, River Noe and Jaggers Clough 2 2.2 Current licence requirements 2 2.3 Recommended licence changes 3 2.4 Limitations on operational flexibility 4 3 ECOLOGICAL CONSIDERATIONS 5 3.1 Potential effects on ecology 5 3.2 Character of reaches 6 3.3 Water Framework Directive 7 4 EFFECTS OF THE 2018 DRY PERIOD 9 4.1 Flows 9 4.2 Macroinvertebrates 9 4.3 Fish 11 5 SUMMARY AND RECOMMENDATIONS 15 5.1 Summary 15 5.1.1 Normal operation 15 5.1.2 Operation during natural circumstances of low flow 15 5.1.3 Potential impacts 16 5.2 Recommendations 17 5.2.1 Phasing of flow changes – current licence conditions 18 5.2.2 Phasing of flow changes post implementation of the Notional Solution 18 5.2.3 Simulation of recommendations during 2018 19 REFERENCES 21 Report Reference: 64116AB R36rev1 OFFICIAL SENSITIVE Report Status: Final rev1 Severn Trent Water AMP6 Low Flows Programme: River Noe and River Ashop Low Flow Page v Distribution Assessment ILLUSTRATIONS Illustration 2.1: Schematic of Ashop-Noe-Jaggers system 3 Illustration 4.1 Macroinvertebrate data for the Ashop and Noe. 10 Illustration 4.2. Standardised fish density (per 100 m2), Ashop d/s Alport confluence (E3-06) 12 Illustration 4.3. Standardised fish density (per 100 m2), Noe d/s impoundment (E2-03) 13 Illustration 4.4.