Land use influences on acidification and recovery of freshwaters in Galloway, south-west Scotland

Abstract

The long term response of surface waters to changes in sulphur deposition and afforestation is investigated for three upland river systems in the Galloway region of south-west Scotland. From 1984-1999, these rivers exhibited a statistically significant decline in non-marine sulphate concentrations in response to reduced acid deposition. This reduction in non-marine sulphate was, however, insufficient to induce a pH recovery over the period. A statistically significant increase in river pH was observed between 1956-1970 (0.05 yr -1 ) when subsidised agricultural lime payments were at a maximum. In 1976, this subsidy ceased and surface waters have progressively acidified. In addition, climatic change is found to influence long-term trends in pH. Mean annual pH was greatest during a dry period between 1969-1973 when total annual discharge was low. Thereafter, pH declined gradually in response to higher rainfall and increased total annual discharge. Overall, surface waters draining the afforested catchments of the Rivers Cree and Bladnoch are more acid than those draining the moorland catchment of the Luce. These results indicate that in afforested catchments, current reductions in sulphur emissions have not led to an observed improvement in the acid status of surface waters. Forestry, therefore, represents a confounding factor with regard to chemical recovery from acidification in this region.

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

“…In Galloway, Ferrier et al (2001) and Helliwell et al (2001). This pattern is similar to that found in Wales where the region is dominated by semi-natural moorland vegetation or coniferous forestry plantation at higher elevation, with improved pasture in lower valleys .…”

Chemical trends at lakes and streams in the UK Acid Waters Monitoring Network, 1988-2000: Evidence for recent recovery at a national scale

“…In the UK, monitoring during the 1970s and early 1980s was limited to local programmes in a few areas (e.g. Harriman et al, 2001;Helliwell et al, 2001). Co-ordinated national monitoring began in 1988 with the establishment of the UK Acid Waters Monitoring Network (AWMN) (Patrick et al, 1995), which provides a regular and controlled programme of chemical, biological and hydrological measurements across a representative range of 22 acid-sensitive waters.…”

Temporal assessment of copper speciation, bioavailability and toxicity in UK freshwaters using chemical equilibrium and biotic ligand models: Implications for compliance with copper environmental quality standards

“…In this regard, the higher drainage densities and steeper topography of this upland study area reduce the amount of time before runoff enters the stream network and consequently the time for potential soil buffering processes within the catchment. Therefore, the surface water draining the afforested catchment of the Cree is inherently more naturally acid (Helliwell et al, 2001).…”