Freshwater Umbrella third Annual Report October 2010

The work programme under the Freshwater Umbrella has been designed to provide the best available means for addressing key DEFRA policy questions regarding the effects of N deposition on upland lakes and streams. These questions may be summarised as: 1. What is the spatial extent of acidification and eutrophication in UK upland lakes and streams which may be attributed to or exacerbated by N deposition? 2. How successful have S and N emission reduction policies been to date in reducing or preventing acidification (measured as critical load exceedance) and eutrophication of sensitive freshwaters in the UK? 3. Which forms of N deposition lead to NO3 - leaching into surface waters? 4. Since only a small proportion of deposited N currently leaks into surface waters, which factors control leaching and how do they change through time, i.e. will the major increases in NO3 - leaching predicted by mass-balance models occur over policy-relevant timescales (years to decades)? 5. How will future reductions in NOx or ammonia emissions affect NO3 - leaching and hence the acidification or eutrophication status of surface waters, and over what timescales?