Invasive Species Investigation
Bristol Water has committed to deliver an invasive non-native species (INNS) investigation as part of the National Environment Programme. This is driven by the Water Framework Directive and the EU Invasive Alien Species (IAS) Regulations. INNS have a number of implications for water companies including:
• Fouling, eroding or blocking of assets
• Altering water quality and the ability to measure it
• Increasing the need for herbicide use within the catchment
• Interfering with recreational use, such as angling and sailing
• Impact on SSSI status
So far we have surveyed Chew Valley and Blagdon lakes, and introduced a company biosecurity procedure based on the DEFRA “Check, Clean, Dry” approach. Biosecurity is a set of precautions to prevent the introduction or spread of INNS or disease. This means taking steps to make sure that good hygiene practices are in place to reduce and minimise the risk of spreading invasive non-native species. A good biosecurity routine is always essential, even if INNS are not always apparent, and we encourage all visitors to our lakes to follow this procedure.
Bristol Water has a regulatory commitment under the National Environment Programme to carry out this investigation at Blagdon Lake. This involves investigating the impact on macrophytes, including species of stonewort, in Blagdon lake under a drought scenario. In practice this would mean reviewing the extent of macrophyte stands as they become exposed as lake levels fall. Under dry/drought conditions, these plants have been seen to suffer a degree of die back. The purpose of the investigation would be to monitor whether these exposure events are detrimentally impacting the macrophyte communities leading them to change or reduce in extent over time.
Currently we are surveying macrophyte species at Blagdon Lake throughout the year, with additional surveys during a dry/drought period.
Water Framework Directive Hydroecology Investigations
Under the Environment Agency’s National Environment Programme, Bristol Water is investigating how downstream river ecology is affected by Blagdon and Chew Valley Reservoirs. Reservoirs by their nature impound water and can therefore directly affect downstream river flows, in terms of flow magnitude, timing and rate of flow changes, seasonality of flows and flow variability. Reservoirs can also affect downstream water quality, temperature, sediments, and the movement of migratory fish such as eels.
We are firstly assessing if and to what extent the reservoirs do cause impacts. We will then undertake an options appraisal and options trials to understand what we can do to reduce or mitigate impacts. This work is being undertaken in consultation with the Environment Agency.
Congresbury Yeo Water Quality Investigation
We are collaborating in an investigation into the influences on water quality in the Congresbury Yeo downstream of Blagdon Reservoir. This work has been initiated and is being co-funded by Bristol Water, Wessex Water, the Environment Agency and Yeo Valley Farms, and aims to understand the relative pressures on the river reach and the interventions required to achieve Good Ecological Potential under the Water Framework Directive.
Barrow Reservoir No. 3 Water Quality Investigation
Barrow Reservoir No. 3 is identified as a lake under the Water Framework Directive (WFD), and is specifically designated as a heavily modified water body. According to the Environment Agency’s assessment the status of the water body is assessed at ‘Moderate’ overall due to elevated concentrations of phosphorus and frequencies of phytoplankton blooms.
We are investigating current and historical phosphorus concentrations in the reservoir, to identify sources and their relative contributions in terms of phosphorus loads to the reservoir. We will then review feasible options to reduce phosphorus concentrations in the reservoir taking into account operation constraints, and provide recommendations based on this review and a high level cost benefit analysis. The investigation will be completed to align with regulatory date set for the relevant NEP driver WFD2i, 30th September 2017.
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