Model Of Acidification Of Groundwater In Catchments Model Research Articles

Assessing recovery from acidification of European surface waters in the year 2010: evaluation of projections made with the MAGIC model in 1995.

In 1999 we used the MAGIC (Model of Acidification of Groundwater In Catchments) model to project acidification of acid-sensitive European surface waters in the year 2010, given implementation of the Gothenburg Protocol to the Convention on Long-Range Transboundary Air Pollution (LRTAP). A total of 202 sites in 10 regions in Europe were studied. These forecasts can now be compared with measurements for the year 2010, to give a "ground truth" evaluation of the model. The prerequisite for this test is that the actual sulfur and nitrogen deposition decreased from 1995 to 2010 by the same amount as that used to drive the model forecasts; this was largely the case for sulfur, but less so for nitrogen, and the simulated surface water [NO3(-)] reflected this difference. For most of the sites, predicted surface water recovery from acidification for the year 2010 is very close to the actual recovery observed from measured data, as recovery is predominantly driven by reductions in sulfur deposition. Overall these results show that MAGIC successfully predicts future water chemistry given known changes in acid deposition.

Modelling catchment response to acid deposition: a regional dual application of the MAGIC model to soils and lakes in the Athabasca Oil Sands Region, Alberta

The effects-based acid emissions management framework (EMF) for determining the need for emission control policies in the Athabasca Oil Sands Region, Canada is dependent on model simulations of future soil and surface water chemistry. An approach for regional application of the Model of Acidification of Groundwater in Catchments (MAGIC) was developed that addresses the differential sensitivity of forest soils and lakes. The approach used was a dual application wherein a plot-scale calibration to forest soils and a catchment-based calibration to lake chemistry were used to account for poorly understood hydrologic connections between uplands and lakes, key processes including sulphur (S) and nitrogen (N) retention as well as groundwater sources of base cations to the lakes. The regional application was carried out at 50 lake catchments currently monitored for response to acid deposition. Simulated forest soil chemistry (modelled at 28 catchments) exhibited small changes in base saturation under future conditions of elevated acid deposition, while in general molar BC:Al exhibited considerable change but remained well above critical chemical limits used to protect acid-sensitive forest soils. Similarly, simulations of charge balance acid neutralizing capacity (ANCCB) for the lakes suggested very small decreases since industrialization, and forecast projections under acid deposition double the current level suggested that only one lake will reach the critical threshold for ANCCB (75 μeq L–1) specified by the EMF. There is limited potential for acidification impacts at the study sites.

The present is the key to the past, but what does the future hold for the recovery of surface waters from acidification?

Analogue matching was used to identify close modern water quality analogues for a set of 59 acid-sensitive lakes in the Galloway region of south-west Scotland. Modern analogues were identified that closely matched the pre-disturbance conditions of these lakes using simulated water quality parameters from the MAGIC (Model of Acidification of Groundwater in Catchments) model for key years from 1860 to 2100. The lakes were matched with hydrochemical samples from a large spatial data set in the UK. For the majority of the 59 lakes, several close modern analogues were identified from the training set for specified years. The close modern analogues for the reference year (1860) were predominantly located in north-west Scotland, an area of low acid deposition and high-status water quality. A clear recovery in the regional surface water acid neutralising capacity (ANC) was simulated by MAGIC in 2015 compared to the situation in 1970 at the height of acid emissions. Predicted trends in surface water chemistry from present day to 2015 indicate some improvement in water quality with c. 23 ± 0.97% recovery towards pre-acidification (1860) ANC for the region. Output from the MAGIC model was used with the analogue technique to investigate the combined influence of future changes in deposition and climate on biogeochemical processes and water quality at the Round Loch of Glenhead (RLGH). Our results demonstrate that pre-acidification restoration targets will not be achieved by simply reducing acid deposition, and climate change will further confound the beneficial effects of deposition reductions. Results for 2015 and beyond show that modern analogues for these periods were predominantly concentrated in North Wales, with some in north-west Scotland, Galloway and the Lake District. Evidence from model simulations and modern analogues indicate that more stringent measures to further reduce acid deposition and combat climate change in the future are necessary if the majority of lakes in the Galloway region are to be restored to their pre-acidification target chemistry. The identified analogues for selected periods may be used to study wider ecological conditions to better define reference conditions and future recovery trajectories. That modern analogues were identified for the simulated chemistry in 2100 at RLGH suggests that unprecedented chemical conditions are unlikely to be observed as a result of future climate change.

Modelling seasonal nitrate concentrations in runoff of a heathland catchment in SW Norway using the MAGIC model: I. Calibration and specification of nitrogen processes

MAGIC (the Model of Acidification of Groundwater In Catchments) has been widely applied on catchments all over the world. The model has been used with annual time resolution to simulate the long-term effects of acidic deposition on surface water chemistry. Here MAGIC was applied using a monthly time step. The purpose was to simulate observed seasonal nitrate (NO3) concentrations and fluxes at an upland heathland catchment in southwestern Norway during the period 1993–2004. The rates of the key ecosystem nitrogen (N) processes (mineralization, plant uptake, litterfall and immobilization) were assumed to be governed by temperature. A snow accumulation and melt routine was used. The rates were calibrated to obtain the best match between the observed and simulated NO3 patterns. The best fit was obtained with standard yearly cycles for deposition and N parameters. The results show that MAGIC can explain 68 and 88% of the variation in seasonal NO3 concentrations and fluxes, respectively. The calibrated model provides a tool for exploring the effects of future scenarios of climate change and N deposition on NO3 in streamwater.

Relationship between landscape characteristics, history, and lakewater acidification in the Adirondack Mountains, New York

Interactions between acidic deposition and watershed characteristics were evaluated for a group of lakes in the Adirondack Mountains, New York. Landscape characteristics were compiled and examined relative to paleolimnological inferences of historical acidification. Results of estimates of acidification using the Model of Acidification of Groundwater in Catchments (MAGIC) and paleolimnological analysis were compared to physical, biological, and landscape change data, including such factors as watershed disturbance, logging, fire, and windthrow, to evaluate if inclusion of additional processes could improve model estimates. Results of bivariate and multivariate analysis confirmed that lakes that have experienced historical acidification tend to be those that receive relatively high amounts of precipitation and have short hydraulic residence times. These variables explained 58% of the diatom-inferred acidification. A combined model of long-term precipitation amount, hydraulic residence time, and recent blowdown accounted for 71% of the historic acidification in the Adirondacks. Lakes that have increased in pH since pre-industrial times tend to be those subject to substantial human disturbance and those that burned during major fires recorded after 1900. The magnitude of the discrepancy between MAGIC model and diatom-inferred hindcasts of acidification was not significantly correlated with any of the landscape change variables, suggesting that additional modifications to the MAGIC model to take into account landscape change are not likely to appreciably improve model performance.

A comparison of methods for estimating soil characteristics in regional acidification models; an application of the MAGIC model to Scotland

Abstract. The results from an application of MAGIC (Model of Acidification of Groundwater In Catchments) to 733 Scottish catchments are presented. The availability of representative, good quality soil data is frequently limiting factor for biogeochemical modelling, particularly those involving modelling at various spatial scales. This study tests the sensitivity of MAGIC to soil input data derived from two different methodologies; the "nearest neighbour method" considers the closest representative soil profile to a catchment, and the "spatial weighting method" of all soil types identified in a catchment, based on a soil physico-chemical classification of Scotland. Soil data (soil depth, density, cation exchange capacity and base saturation) calculated using the "nearest neighbour method" and the "spatial weighting method" were highly variable, although the range of upper and lower limits were greater for soil data produced using the nearest neighbour method. In contrast to the predominantly organic soil data calculated by the nearest neighbour method, the spatially weighted soil parameters included a greater proportion of mineral soils. With regard to simulated surface water Acid Neutralising Capacity (ANC) for 1851, 1997 and 2050, MAGIC predictions were similar irrespective of the methodology used to determine soil input parameters. However, soil input data derived from both methods resulted in variable base saturation predictions. It is concluded that the "nearest neighbour" methodology is most appropriate if the objective is to determine the predicted response of the most acid- sensitive sites within a region in line with the approach used in Critical Laod mapping. On the other hand, "spatial weighting" integrates catchment soils and represents a more robust methodology by which to determine changes in median soil and water response in a regional context. The anticipated reductions in S emissions associated with the Second S Protocol are predicted to have a marginal beneficial effect on the recovery of soils and surface waters of Scotland.

Testing, improvement, and confirmation of a watershed model of acid-base chemistry

Strategies to control the emission of atmospheric pollutants such as sulfur and nitrogen, are generally based in large part on projections using models that simulate the influence of sulfur and/or nitrogen deposition on the acid-base chemistry of surface waters. One of the principal models used throughout Europe and North America for such assessment is the Model of Acidification of Groundwater in Catchments (MAGIC). All watershed models are simplified representations of reality, and as such require careful testing to establish their veracity prior to use for making policy projections. This is particularly true where the use of these model projections has the potential for serious environmental or economic consequences. During the past five years, we have tested the MAGIC model in a large variety of settings and under quite varying environmental conditions. This work has included comparing model hindcast simulations with diatom-inferences of historical acidification, sensitivity analyses to examine the response of the model to alternative assumptions and formulations, and detailed testing of model forecasts by comparing simulated chemistry with the results of catchment-scale and plot-scale experimental acidification and deacidification. Our analyses have elucidated a number of potentially-important deficiencies in model structure and method of application. These have resulted in changes to the model and its calibration procedures. Our work has included in-depth evaluation of issues related to regional aggregation of soils data, background sulfur deposition, natural organic acidity, and aluminum mobilization. The result has been an improved and more thoroughly-tested version of MAGIC. The process we have followed to improve and confirm the MAGIC model has been iterative and time consuming. It required the availability of large volumes of data from experimental manipulation and paleolimnological studies. We believe that such model testing and confirmation efforts should be a critical prerequisite for regional or national assessment activities that are based largely on the results of environmental models.