RTCT, Freshwater Habitats Trust and Wild Oxfordshire, in association with the Environment Agency, will be undertaking a water improvement project in the Holton Brook catchment in 2015/16. A map of the Holton Brook is shown below. The project will work with landowners to (i) identify small-scale practical measures that can be introduced to reduce diffuse pollution, and (ii) begin implementation of the measures identified. The partnership will also seek additional funding to complete measure implementation beyond the timescale of this short project. Specifically, the project will engage with landowners to identify where small scale interventions may be positioned to intercept the main diffuse pollutants of concern (phosphorus, nitrogen and sediments) at the point where they leave the field, and before they reach the main receiving waters. Nitrate is not currently used to assess waterbody status in the Water Framework Directive (WFD). However, although not directly affecting the WFD classification, the high levels of nitrate recorded in the area are very likely to limit biological recovery.
The project will address these issues in three main ways:
1. Intercept or manage diffuse nutrient and sediment sources:
(a) Small scale interventions may include:
- Small wetland drain interceptor basins to intercept field drains that often bypass field margin buffer strips;
- Installation of low bunds in existing ditch systems across the landscape to slow flows and hold back sediments and sediment associated nutrients, especially phosphorus.
- Fencing stream access to livestock to limit sediment and phosphate input.
(b) Gateway and livestock crossing (on farm) improving and/or repositioning: where heavily eroded gateways are close to streams we will use hard-core or other materials to limit sediment input into streams, or move them so they pose less of a threat to the water environment. This may involve fencing off access to the watercourse from livestock.
2. Intercept or manage rural small point sources of nutrients and sediment (e.g. sceptic tanks).
Water quality surveys being undertaken in the project area (but separate to this funding bid) and any waterbody walkovers may uncover non-STW phosphorus point sources in the project area (e.g. poorly management or functioning septic tanks, misconnections). We will work to identify the causes of any such pollution, propose measures to intercept and/or seek to rectify these issues.
3. Improve in-stream areas where invertebrate and/or macrophyte habitat may be improved.
This may involve the addition of woody debris, which is one of the most effective techniques for enhancing stream and river systems, stream fencing or bank modifications.