Evaluating the impact of land use and policy on water quality in an agricultural catchment : the Leet Water, South-East Scotland.
This is an interdisciplinary study combining research techniques from the natural and social sciences, to evaluate the impact of EU policies and land use change scenarios for assessing water quality in an agricultural catchment. The study focuses on the Leet Water catchment, a left-bank tributary of the River Tweed, Berwickshire, South-East Scotland. The Leet Water and its subcatchment the Lambden Bum cover an area of approximately 114km(^2) within the Lothian and Borders Nitrate Vulnerable Zone (designated in 2002).In the Leet Water catchment, spot measurements of nitrate (NO(^3)-N) from 1977 to 1998 found the 11.3 mg/1 (EU permitted maximum) was often exceeded. Further spot monitoring from October 2002 to August 2004 found 12 instances where the 11.3 mg/1 permitted maximum was exceeded with all streams in the catchment experiencing high levels of nitrate over the winter periods. Interviews with local farmers, advisors, and the regulators found this to be the result of a complex set of circumstances including long-term Common Agricultural Policy subsidies and the farmers' drive for increased profitability without due regard for the environmental consequences. Land management practices such as under- draining of fields, overuse of fertiliser and allowing livestock access to water-courses has exacerbated the problem. The study demonstrates the potential of multispectral airborne remote sensed data for mapping agricultural land cover at the field scale, including the ability to distinguish winter and spring-sown cereal crops. Pollution impacts were modelled using a modified export coefficient approach by integrating land cover with available chemical and fertiliser practice data sets. Results of modelling scenarios of simple land use changes found that reducing fertiliser use by 10% can reduce the number of fields in the very high risk group from 191 to 16 This equates to reducing the high risk area from 〜3255 ha (29% of the catchment) to 〜428 ha (3.3 % of the catchment). This method of water quality modelling provides a means of integrating field research on water quality with the results of socio-economic surveys. The research found the principal causes of the failure of EU policy to address the problems are both socio-economic and institutional barriers, in particular the way in which information is presented to the farming community. Case studies of both large and small farms reveal that agri-environment measures such as the 'points' based Rural Stewardship Scheme (RSS) can attract substantial funding. However, these schemes are of most benefit to large farms where significant land use changes that accrue points can be made. Smaller farms find it difficult to suggest changes that will accrue these 'points' for a successful application. Furthermore, farmers believe recent changes e.g. the Land Management Contract implemented by The Scottish Executive may include a range of funding opportunities for improving land management practices but these are not well presented. There are gaps in the knowledge transfer process in relation to water quality issues between Government and land users. This research suggests that independent facilitators (advisors) such as those used in the Australian landcare approach should be introduced in the UK to help address this problem.