River Thames, (Thame sub-catchment), England

REFRESH Catchment case studies - responding to future change: River Thames, S. England (Thame sub-catchment)

Thame Sub catchmentThe River Thame is a tributary of the Thames flowing through Oxfordshire and Buckinghamshire in south east England. Around 45% of the catchment is grassland and 39% arable. There are two Special Areas of Conservation and Sites of Special Scientific Interest and one Area of Outstanding Natural Beauty. There has been significant growth in urban centres in recent decades. Water quality is generally good but there are high phosphorus concentrations. Diffuse and point source pollution are major water quality issues.

Although the water quality in the River Thame is generally good, scientists and local stakeholders agree that there are problems related to diffuse pollution (agricultural and urban) and point source pollution (urban wastewater and septic tanks). Looking specifically at phosphorus, current research suggests that the cheapest way to improve water quality in this particular river is to reduce diffuse pollution from agriculture by applying the following additional measures:

  • Establish riparian buffer strips.

  • Reduce phosphorus fertilizer applied across all crop land by 20%

  • Adopt minimum tillage systems.

  • Construct wetlands/sediment retention ponds.

  • Establish cover crops during winter.

There are other measures which may also reduce phosphorus pollution (e.g. reducing stocking density or fencing off riparian zones), but they are less cost-effective. In addition to water pollution, there are other pressures affecting the aquatic environment, such as physical modification of stream channels. These should also be considered in water management. The application of mitigation actions implies costs in terms of investment and operational costs as well as reduced benefits (for example, decrease in crop yields in land set aside for buffer strips of constructed wetlands). However, if water quality improves in the River Thame, society will also receive more benefits, including:

  • Improved recreation conditions for walkers and nature enthusiasts.

  • Benefits to local business and the community.

  • Increases in the overall quality of fishing, bringing further benefits to the local community (increased fees).

  • Reduced treatment costs of water for human consumption and lower costs from reduced fertilizer applications.

Research shows that in economic terms, the total benefits of the improved water quality in the Thame basin are higher than the costs of the measures needed for improvement over time. However, qualitative assessment of the socio-economic effects of such measures shows that benefits and costs are not equally distributed across society: a significant burden is placed on farmers (and, to some extent potentially, on Thames Water), while the public generally is the main beneficiary of improved water quality. To address these distributional issues, we should not focus on cost-effectiveness only, but also we should also work on improving compensation mechanisms in terms of fairness as well as increasing the flexibility of environmental regulation and awareness raising.

Results presented here are based on the most up to date research, but there are methodological challenges that require further investigation. These include:

  • Addressing multiple pressures. Local stakeholder consultation indicated that there are multiple pressures acting on the River Thame, but this research has only focused on phosphorus. Further research is required to understand the effects of multiple pressures acting together.
  • Estimation of benefits at the local level. Benefits estimations have been based on the benefit transfer method which brings with it some errors. Primary local estimations would help improve estimates.
  • Climate and land use change effects. The results presented relate to current climate conditions and land use, but the robustness of the measures in the face of changing future conditions would need to be tested (see other REFRESH case studies).

For further information see REFRESH reports

Workshop proceedings on collaborative scoping of solutions, Thames catchment, UK

River Thames modelling, final report

Cost-effectiveness Analysis reports for the Thames/Kennet catchment, UK, including analysis of proportionality/disproportionality

Synthesis of work at Thames / Kennet catchment, UK

Proceedings of stakeholder workshop for improving water quality in the Thame sub-catchment, UK. September 2012

'Improving water Quality in the River Thame - sharing scientific and local knowledge'