Changes in pH and calcium after selective liming in the catchment of Loch Dee, a sensitive and rapid-turnover loch in south-west Scotland

Abstract

. A variety of liming techniques were investigated to mitigate the effects of long-term acidification of Loch Dee. a rapid-turnover loch in south-west Scotland. Of the limestone chips and powder added to the major inflow stream plus powder added to the catchment between 1980 and 1982, only 3·6% was calculated to have reached the loch and none was lost at the outflow. After the addition of limestone powder to the loch in 1983. via the major inflow stream, the calcium levels increased in the loch but 50% of the added limestone was calculated to have been lost at the loch outflow, Within 2 years, calcium concentrations and pH had relumed to pre-liming levels. Calcium uptake by sediments accounted for about 28% of the 75 tonnes of limestone added although this was probably n conservative estimate. These results suggest that, in sensitive rapid-turnover lochs, the addition of limestone will be at least a regular requirement if water quality is lo be maintained at levels desirable for maintaining a viable fishery, A high initial dosage will also be required due lo calcium uptake by sediments.