Kurtna Lake District: a natural pearl suffering from anthropogenic pressures

Abstract

The Kurtna Lake District, situated in the northeastern part of Estonia, contains the largest number of lakes per km2 in the country – 38 natural lakes in a 30 km2 area. The unique area fell under severe anthropogenic influence in the middle of the 20th century and the influence has continued until the present day. Oil-shale, sand and peat mining, groundwater and surface water abstraction – all have been affecting the lakes in the district. Lake water levels have dropped, lake chemistries and consequently lake ecosystems have changed. For some lakes the effects have been larger, but some lakes have remained mostly unchanged. In 1987 a landscape protection area was formed, but that has not solved the problems. The lake district used to contain five rare clear water lakes with low nutrient and mineral content (L. Valgejärv, L. Liivjärv, L. Ahnejärv, L. Martiska, L. Kuradijärv). Nowadays, most of them have become significantly more eutrophic, because of water level decrease, but L. Valgejärv, with its preserved unique plant communities, is still considered to be one of the ecologically most valuable lakes in Estonia. The lake district also contains the only siderotrophic (iron rich) lake in Estonia – Lake Räätsma. Lakes Nõmmejärv and Konsu have had their water regime changed considerably. Lake Nõmmejärv accepts the inflow of sulphate-rich mine water and Lake Konsu has been turned into a surface water reservoir for an oil-shale processing factory. Lake Kihljärv on the other hand has effectively dried out in the recent years. At the same time, the picturesque Lake Saarejärv has remained largely unaffected. Therefore, the Kurtna Lake District is an area of great contrasts, partly it still resembles the pristine nature it used to be, and partly it is a sad monument for an overly eager consumption of natural resources.