Critical loads for soils and freshwaters; a comparison methods at the Plynlimon catchments A. Jenkins1, S. Coric4, B. Reynolds2, C. Curtis3, and M. Renshaw1 1Institute of Hydrology, Wallingford, Oxen., UK. 2Institute of Terrestrial Ecology, Bangor, Gwynedd, UK. 3Department of Geography, University College London, UK. 4Department of Civil Engineering, Imperial College, London, UK.
Abstract. International agreements aimed at reducing sulphur
deposition from the atmosphere are now focused on the "critical loads" concept. This provides a distributed
link between sources and receptors of acidic oxides and also links the level of reduction with
biological recovery. Methods for calculating critical loads include simple classification (Level
0), mass-balance equilibrium models (Level 1) and dynamic hydrochemical models (Level 2). Here,
examples of each method are applied to headwater catchments in Plynlimon, mid-Wales. The critical
loads derived are compared and the utility of the critical loads concept as a tool for
local pollution control and land management is assessed.
Differences in critical load methods for soils result
from assumptions regarding biological receptors. Surface water critical loads are generally similar under
all methods. As a local management tool, the dynamic model is most appropriate although it
has a high data requirement. The utility of other methods depends upon detailed maps
of soil and vegetation being available at an appropriate scale.
Citation: Jenkins, A., Coric, S., Reynolds, B., Curtis, C., and Renshaw, M.: Critical loads for soils and freshwaters; a comparison methods at the Plynlimon catchments, Hydrol. Earth Syst. Sci., 1, 729-741, doi:10.5194/hess-1-729-1997, 1997.