A tool for cost-effectiveness analysis of field scale sediment-bound phosphorus mitigation measures and application to analysis of spatial and temporal targeting in the Lunan Water catchment, Scotland

Abstract

The cost-effectiveness of six edge-of-field measures for mitigating diffuse pollution from sediment bound phosphorus (P) runoff from temperate arable farmland is analysed at catchment/field scales. These measures were: buffer strips, permanent grassland in the lowest 7% of arable fields, dry detention bunds, wetlands, and temporary barriers such as sediment fences. Baseline field P export was estimated using export coefficients (low risk crops) or a modified Universal Soil Loss Equation (high risk crops). The impact of measures was estimated using simple equations. Costs were estimated from gross margin losses or local data on grants. We used a net cost:benefit (NCB) factor to normalise the costs and impacts of each measure over time. Costs minimisation for target impact was done using PuLP, a linear programming module for Python, across 1634 riparian and non-riparian fields in the Lunan Water, a mixed arable catchment in Eastern Scotland. With all measures in place, average cost-effectiveness increases from £9 to £48/kg P as target P mitigation increases from 500 to 2500kg P across the catchment. Costs increase significantly when the measures available are restricted only to those currently eligible for government grants (buffers, bunds and wetlands). The assumed orientation of the average field slope makes a strong difference to the potential for storage of water by bunds and overall cost-effectiveness, but the non-funded measures can substitute for the extra expense incurred by bunds, where the slope orientation is not suitable. Economic discounting over time of impacts and costs of measures favours those measures, such as sediment fences, which are strongly targeted both spatially and temporally. This tool could be a useful guide for dialogue with land users about the potential fields to target for mitigation to achieve catchment targets.

Global mapping of freshwater nutrient enrichment and periphyton growth potential

“…In isolating the limiting nutrient (and form thereof) and prioritising areas that require remediation, the choice and cost-effectiveness of good management practices can be optimised 56 . Once land managers know which nutrient to concentrate on they can identify small areas of the farm, often term critical source areas, that account for the majority of losses to water 57 .…”

Challenges of Reducing Phosphorus Based Water Eutrophication in the Agricultural Landscapes of Northwest Europe

“…Transforming this knowledge into appropriate cost effective mitigation strategies remains a major challenge (Schoumans et al, 2014(Schoumans et al, , 2015Dodds and Sharpley, 2015;Kleinman et al, 2015;Sharpley et al, 2015;Withers et al, 2015a,b;Rowe et al, 2016). The degree of integration and knowledge is such today that some of the most recent studies can go as far as integrating the costs of management in the reduction of diffuse phosphorus emissions, in connection with national or local legislation or land property issues (e.g., McDowell et al, 2016;Vinten et al, 2017;Zhang et al, 2017).…”

A strategy for optimizing catchment management actions to stressor–response relationships in freshwaters

“…, Vinten et al. ). McDowell () showed that across 14 sub‐catchments farmed with sheep, red deer, beef, or dairy cattle, the cost‐effectiveness of mitigations targeted to critical source areas was six to seven times higher than untargeted mitigation actions.…”

“…, Vinten et al. ). Furthermore, although proxies such as connectivity indices exist to indicate the likely response time of actions, direct evidence of treatment speeds is sparse (Stieglitz et al.…”