Impacts of land use policy on the recovery of mountain catchments from acidification

Abstract

Watersheds in mountainous regions provide water resources available to large downstream areas. Acidification of mountain waters leads to problems in water quality with impacts to drinking water supply and biodiversity conservation. Effects of the land use policy, air pollution and forest canopy on acidification of headwater catchments in the Jizera Mountains were studied in the period of 1982–2015. The archive of LANDSAT imagery and a field inventory was used to reconstruct changes in the vegetative cover. The atmospheric deposition of acidic substances (sulphate, nitrate, and ammonia) in studied catchments was approximated by a spatial interpolation. The acid atmospheric load culminated in the 1980s. The Helsinki protocol on the reduction of sulphur emissions lead to a reduced open field deposition of sulphur, but, the atmospheric deposition of sulphur and nitrogen is also controlled by the vegetative canopy. A drop in the acid load and a recovery of surface waters from acidification were observed with the harvest of spruce forests. The existing land use policy, institutes of ‘protected headwater area’ and ‘zones of hygienic protection’ (Water Act 138/1973) were ineffective in this situation. In a catchment scale, the proposed scenario of structured forestry zones (respecting riparian buffers, stability of steep slopes, significant fog drip areas, peat spots) can decrease the annual load of sulphur and nitrogen by approx. 30%.