Catchment Management

Models describing the relative contributions of phosphorus (P) from different sources to water bodies (source apportionment) are key tools in determining priorities for mitigation strategies within the River Basin Management Planning process under the Water Framework Directive (WFD). Previous source apportionment was simplistic because it was based on total P loads, even though not all P loading has the same ecological significance due to the form or timing of the loading.

There is a need to increase awareness of the benefits that water provides and how our actions can help protect and improve them. Concerns over water quality and quantity are increasing around the world and these are exacerbated by climate change and other pressures. Arguably, and having a plentiful supply of water from rainfall, Scotland has not been severely affected by these issues. Consequently there is a perception that public understanding of water and the benefits provided is often low.

In 2015, a review of Scotland’s Water Sector was published by CREW in support of the Scottish Government’s Hydro Nation Strategy. This work reported on the scope and the scale of Scotland’s Water Sector, and how different parts of the sector link together using visual tools in the form of Scotland’s Water Map.

Onsite wastewater treatment systems (OWTS), the majority of which are septic tanks, are a contributing factor to phosphorus and faecal microbial loads. OWTS contribute to waterbodies failing to meet Water Framework Directive (WFD) objectives and as such, measures to improve the quality of OWTS discharges are required. Literature has been reviewed for a range of measures designed to reduce phosphorus and pathogen concentrations in effluent from OWTS. A feasibility assessment focussed on their application, effectiveness, efficiency, cost and ease of adaptation.

This project set out to explore the possibility of producing a set of four risk maps that could be used to determine the risk of diffuse pollution occurring within Scottish agricultural catchments. The key soil-based factors likely to affect water quality were deemed to be: