Environmental Assessment of the Afon Rhondda Fawr Drought Permit (8112-1)
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Dŵr Cymru Welsh Water Environmental Assessment of the Afon Rhondda Fawr Drought Permit (8112-1) Final March 2019 Client: Dŵr Cymru Welsh Water Title: Environmental Assessment of Afon Rhondda Fawr Drought Permit (8112-1) Project No: ED10929 Date of Issue: March 2019 Status: Final Version No: 1.0 Produced By Authorised for Release By ……………………………….. …………………………………… Dr Anne Fairhead John Sanders Principal Environmental Scientist Technical Director This report is the Copyright of Welsh Water and has been prepared under contract to provide consultancy support on drought planning by both Cascade Consulting (Environment & Planning) Ltd and by Ricardo Energy & Environment.* The contents of this report may not be reproduced, in whole or in part, nor passed to any organisation or person without the specific prior written permission of Welsh Water. Cascade Consulting (Environment & Planning) Ltd and Ricardo Energy & Environment accept no liability whatsoever to any third party for any loss or damage arising from any interpretation or use of the information contained in this report, or reliance on any views expressed therein, other than the liability that is agreed in the said contracts. *As part of a share purchase agreement in August 2015, Cascade Consulting (Environment & Planning) Ltd transferred its business to Ricardo plc. All employees transferred to Ricardo Energy & Environment, a trading name of Ricardo-AEA Ltd which is a wholly owned subsidiary of Ricardo plc. The work described in this report spanned the pre-acquisition and post-acquisition period and throughout this time the consultants involved maintained a continuity of service both as employees of Cascade Consulting and then subsequently as employees of Ricardo Energy & Environment. CONTACT DETAILS: Ricardo Energy & Environment Bright Building, First Floor Manchester Science Park Pencroft Way Manchester M15 6SGZ Tel: +44 (0)1235 753000 Dŵr Cymru Welsh Water Environmental Assessment of the Afon Rhondda Fawr Drought Permit (8112-1) Final NON-TECHNICAL SUMMARY INTRODUCTION AND PURPOSE OF THIS REPORT Welsh Water’s Drought Plan provides a comprehensive statement of the actions Welsh Water will consider implementing during drought conditions to safeguard essential water supplies to customers and minimise environmental impact. It encompasses a number of drought management options that will only be implemented if and when required and includes drought permit options. A drought permit is a management action that, if granted, can allow more flexibility to manage water resources and the effects of drought on public water supply and the environment. The objective of this report is to provide an independent and robust assessment of the potential environmental effects of implementing a drought permit at the Afon Rhondda Fawr, over and above those arising due to natural effects of drought and those which would occur under "normal" abstraction licence conditions. Afon Rhondda Fawr is located in Welsh Water’s South-east Wales Conjunctive Use System (SEWCUS) Water Resource Zone (WRZ) which covers the large conurbations of Cardiff and Newport as well as the towns and villages of the South Wales valleys as far west as the Rhondda Valley and as far east as Chepstow. Water from the Afon Rhondda Fawr combines with water from the Afon Rhondda Fach as the River Rhondda at Porth. The assessment also considers how the proposed drought permit may affect the environment in combination with the effects of other existing abstraction licences, environmental permits and other drought management plans. This report is a ‘shelf-copy’ report which would be updated to support an application to Natural Resources Wales for a drought permit at the Afon Rhondda Fawr, which may be required by Welsh Water in the future. PROPOSED DROUGHT PERMIT DETAILS In order to protect public water supplies within Welsh Water’s SEWCUS WRZ in the event of a future severe drought, Welsh Water would make an application to Natural Resources Wales (NRW) for a drought permit for a temporary abstraction from the Afon Rhondda Fawr. If granted, the drought permit involves a new, unsupported emergency river abstraction of 1Ml/d from the Afon Rhondda Fawr adjacent to Treherbert to support raw water supply to the raw water storage reservoir at Tynywaun Water Treatment Ricardo Energy & Environment Dŵr Cymru Welsh Water Environmental Assessment of the Afon Rhondda Fawr Drought Permit (8112-1) Final Works (WTW). To enable the abstraction, a low, temporary weir constructed of sandbags would be required across the Afon Rhondda Fawr. A modest volume of water would be available from this drought permit scheme during a drought, and there is benefit to supply locally through provision of an immediate additional water resource to an existing WTW. The drought permit would influence the Afon Rhondda Fawr for a short distance downstream during ongoing low flow conditions; and the Nant Selsig, Nant Ystrad Ffernol and Nant Rhondda Fawr Stream upstream of the temporary weir. The drought permit is most likely to occur during the summer and autumn period, and is considered not to extend outside the period September to November. This has been confirmed by Welsh Water’s water resources modelling. The revised abstraction arrangements would legally be authorised for three months but would be removed sooner if water resources have returned to adequate levels to safeguard future water supplies, as agreed with NRW NEED FOR THE DROUGHT PERMIT Application for a drought permit is a precautionary approach. Due to the time needed to determine a drought permit application, Welsh Water will potentially apply for a drought permit more frequently than it will be used. The justification for the drought permit sought will be set out in a “Needs Statement”. This will be produced by Welsh Water at the time of a potential future application, and will form part of the full drought permit application. ALTERNATIVE SOURCES CONSIDERED Details of alternative sources considered by Welsh Water will be completed at the time of application for the drought permit at the Afon Rhondda Fawr. This will demonstrate justification for the proposed drought option details applied for. POTENTIAL IMPACTS OF DROUGHT PERMIT IMPLEMENTATION The scope of the assessment has been defined by a screening and scoping exercise. Ricardo Energy & Environment Dŵr Cymru Welsh Water Environmental Assessment of the Afon Rhondda Fawr Drought Permit (8112-1) Final Summary of the Hydrological Assessment The assessment has concluded that there is a minor impact on flows in headwater streams and a major impact on flows in the Afon Rhondda Fawr as a result of implementing the drought permit. Impacts on the Afon Rhondda Fawr from the confluence of the Afon Rhondda Fach to the confluence of the River Taff have been assessed as negligible. These hydrological impacts are assessed as leading to minor impacts on the physical environment of the river, including water quality. Summary of the Environmental Features Screening Environmental assessment is required and included for features where screening has identified a major or moderate impact. Screening identified WFD status and Community Assessment / Environment (Wales) Act Section 7 species, invasive fauna, landscape and recreation as environmental features for which an environmental assessment was required. The assessment has concluded that during periods when abstractions from a temporary intake at Treherbert on the Afon Rhondda Fawr occur there are major impacts on fish, macrophytes and white-clawed crayfish and moderate impacts on macrophytes, macroinvertebrates and phytobenthos. Cumulative Impacts No cumulative effects of implementing the drought permit with existing licences, consents and plans are currently anticipated. However, this should be reviewed at the time of any future application for a drought permit at the Afon Rhondda Fawr. MITIGATION AND MONITORING The environmental assessment has identified significant impacts of implementation of a drought permit at the Afon Rhondda Fawr. Consequently, in line with the DPG, an Environmental Monitoring Plan has been proposed. Potential mitigation measures have also been proposed and further discussion with NRW is required in order to develop suitable mitigation measures. CONCLUSIONS In summary, it has been concluded that the environmental effects on river flows, water quality and ecology of implementing a drought permit at the Afon Rhondda Fawr during September to November inclusive, over and above those conditions that already exist under "normal", i.e. licensed, baseline conditions, with the onset of a natural drought, would be major. Ricardo Energy & Environment Dŵr Cymru Welsh Water Environmental Assessment of the Afon Rhondda Fawr Drought Permit (8112-1) Final Contents Non-Technical Summary 1 Introduction ............................................................................................. 1 1.1 Purpose of the Environmental Assessment ............................................................. 1 1.2 Supporting Studies...................................................................................................2 1.3 Consultation .............................................................................................................3 1.4 Structure and Content of the Report .......................................................................3 2 Background to the Drought Permit ............................................................ 4 2.1 Welsh Water’s Supply System................................................................................