Modelling the recovery of surface water chemistry and the ecological implications in the British uplands

Abstract

The MAGIC (Model of Acidification of Groundwaters in Catchments) model has been calibrated to three acid sensitive regions in the UK: Galloway, the South Pennines and Wales. These calibrations use the best available data for surface water, soil and deposition, from several UK data bases and regional sampling programmes. The model is capable of reproducing observed base cation and acid anion concentrations as reflected by a close match between observed and simulated acid neutralising capacity (ANC). Predictions to 2016 under currently agreed emission reductions, the Gothenburg Protocol, show that ANC greater than zero will be achieved at 100%, 86% and 100% of sites in Galloway, the Pennines and Wales, respectively. This indicates the potential for biological recovery and a return to good status although chemical conditions remain some way from simulated pre-acidification conditions. In the longer term, beyond 2036 (20 years after compliance with the Gothenburg protocol), the model indicates that increased N leakage to surface waters may cause deterioration in the chemical status.

Dynamic Modeling and Target Loads of Sulfur and Nitrogen for Surface Waters in Finland, Norway, Sweden, and the United Kingdom

“…Regional dynamic modeling results have been reported for individual countries. ,,,, However, previous assessments primarily focused on scenario analyses, i.e., simulations to answer the question: what is the future chemical status of a surface water under various deposition scenarios? In contrast, the current study addresses the inverse question: what deposition, called target load, is required to obtain a specified lake chemical status within a given time period (if feasible)?…”

“…The study sites are predominantly small acid-sensitive headwater lakes and streams, with low base cation concentrations, low alkalinity, and low (charge balance) ANC . All surface waters have been widely used in acidification assessments evaluating long-term trends in surface water chemistry − and the prediction of future chemistry using dynamic (hydro-chemical) models, specifically MAGIC. − The study sites have played a central role in European-scale projects, such as ‘Recover:2010’ and “Eurolimpacs”, focused on model simulations of surface water response to European emissions reduction policies. The process limitations and predictive uncertainty of MAGIC in isolation and in comparison with other models, e.g., PnET-BGC (photosynthesis and evapotranspiration-biogeochemistry), SAFE (soil acidification in forest ecosystems), and VSD (very simple dynamic), have been widely published. ,,, Similarly, the influence of climate change on model predictions for MAGIC have been widely assessed. ,,, As such, herein, we focus on the determination of target loads using MAGIC, which (hitherto for) have not been reported for the study sites and refer the reader to previous publications for detailed information regarding model calibration and process uncertainty for MAGIC.…”

Modelling hydrochemical and ecological trends in acid sensitive surface waters in the Scottish Highlands

“…Winter snowfall is substantial at high elevation, and can contribute ~30% of mean annual precipitation in some areas (Dunn et al 2001). The magnitude of acid deposition in remote Scottish mountains is minor relative to other areas of the UK with deposi- tion inputs of c. 14 kg ha -1 y -1 S and ca 8 kg ha -1 y -1 N (Monteith & Evans 2000;Helliwell et al 2003). and c) soil map (1:10,000).…”

Long-term predictions of ecosystem acidification and recovery

“…There have been many acidification modelling studies involving projections into the future (e.g. Evans et al, 1998;Ferrier et al, 2003;Helliwell et al, 2003;Jenkins et al, 1990). Usually the time period concerned is 50 years or less, because of a well-justified feeling that predictions become too uncertain over longer periods.…”