Lower Farm is a predominantly arable farm straddling two catchments to the south and east of Garsington in Oxfordshire. The land to the south drains into the Baldon Brook and the east flows into the Denton Brook to meet the River. Both catchments suffer from phosphate pollution, The Project planned a range of interventions, in two phases to slow the flow, and hold back nutrients and sediments.
These interventions were:
- Bunded ditches in existing ditch systems,
- Sedimentation ponds,
- Pond restoration and expansion
Baseline Assessment and Planning
The initial assessment determined the topography of the land and the resultant drainage flows, as shown in Figure 2. This informed the positioning of monitoring points necessary to identify variations in phosphate and nitrate levels across the area and to establish a baseline against which results of the measures installed can be assessed.
This initial assessment provided the information as to where interception measures would be at their most effective (i.e. in terms of land draining into them) given the constraints of available space and without compromising the operation of the farm. Regulatory issues were also considered at this stage and specifically the constraints and opportunities under the then prevailing agri-environment schemes.
Management and Monitoring
Management: Interception ponds need only minimal management. Overflow pipes need to be checked as with all ditch lines on an annual basis. Sediment should be excavated out with the spoil spread back onto the fields. The frequency of this work will be dictated by the extent of sedimentation.
Monitoring: assessment as to whether any improvement occurs is critical and underlines the importance of setting up the baseline prior to the project commencement. Funding is often a significant impediment here especially given the multi-year time horizons over which improvements may occur. Water quality monitoring can, however, increasingly be achieved in a cost-effective way using quick testing kits to measure phosphate and nitrate concentrations. These are being used by local volunteers to provide continued project area monitoring at Lower Farm.