THE EFFECTS OF LAND MANAGEMENT AND PREDICTED CLIMATE CHANGE ON HYDROLOGICAL CONNECTIVITY AND DIFFUSE FINE SEDIMENT POLLUTION RISK WITHIN THE RIVER EDEN CATCHMENT.

Abstract

There is a growing recognition that future management of the water quality in UK rivers will depend upon an improved understanding of the effects of projected climate change on catchment systems. Until recently, little attention has been given to the secondary effects that climate change may have. However, it is now becoming clear that successful management will depend upon research into factors beyond the primary changes in soil moisture and river flows. One area of particular concern is the way climate change may alter patterns of diffuse pollution of fine sediment, with associated impacts on river flora and fauna.

If the UK is going to meet the stringent targets laid out in the EU Water Framework Directive, then urgent management of diffuse pollution is required. In 2012 only 28% of water bodies met their ecological potential or good status and 67% of river water bodies cite diffuse pollution as a key pressure which is preventing improvement and the achievement of good ecological status (Environment Agency, 2012). For management solutions to be cost-effective, they need to be targeted at the key problem areas within a catchment. This research uses the River Eden catchment in Cumbria as a test catchment and applies a hydrological simulation model, risk mapping framework and risk filter to the area in order to determine current connectivity and diffuse pollution trends. From this toolkit, projections of the future patterns of risk are calculated.

The SCIMAP based toolkit predicted that the fine-sediment erosion risk varies spatially across the River Eden catchment. Locations deemed to be most at risk of causing a fine-sediment pollution issue are in the lower reaches of the catchment where intensive arable farming is found. When risks were modelled temporally, variations depending upon vegetation cover and average monthly rainfall were found. It was noted that the presence of autumn-sown crops could reduce risk over a year whilst spring-sown crops are likely to increase fine-sediment erosion risks.

Several conclusions are drawn from this research: 1) it has been shown that the SCIMAP framework is an effective way of identifying critical source areas of diffuse pollution and could prove an invaluable tool to environmental managers; 2) the important role that autumn-sown crops can play in minimising erosion risk has been shown to be applicable in the River Eden catchment and the best way to incorporate this into crop cycles highlighted; 3) through the use of projected climate change data and a hydrological simulation model, it has been shown that the location of critical source areas are likely to change as a result of projected climate change and associated variability in rural land management. This highlights the need for continuous catchment-wide monitoring and management of hydrological connectivity and associated diffuse pollution risks.