The Pandivere Upland
The Pandivere Upland is the highest bedrock upland in Estonia. Its bedrock is represented by Middle and Upper Ordovician and Lower Silurian limestones. The Izhora Upland in northwest of Russia is a similar structure. The Pandivere and Izhora uplands and the Ahtme elevation are the central parts of more than 300 million-year-old pre-Devonian elevations, eroded by glaciers. The top and the southern slope of the Pandivere Upland have preserved the features of the pre-Devonian elevation, but its northern slope was formed in the Cenozoic, in the process of the formation of the depression of the Gulf of Finland. The continental glaciers eroded the northern slope during the Pleistocene ice ages.
The Quaternary cover of the upland is only a few metres thick. The largest Quaternary landforms — the Ebavere (146 m a.s.l.), Kellavere (156 a.s.l.) and Emumägi (166 m a.s.l) hills are located on the southern slope of the upland. Other well-known Quaternary landforms on the slopes of the upland are the Porkuni–Neeruti hills and the Rakvere Vallimägi, Pähnimägi, and Võlumägi hills.
The Quaternary cover is composed of calcareous clayey till. It has moderate water-bearing capacity and is a favourable source rock for fertile soils that are common in the Pandivere region. Agricultural landscapes dominate here. Small stands of forest are reminders of the times when the area was covered with diverse broad-leaved forests.
Temporary lakes and karst springs
In the Pandivere Upland, the limestones are near the surface and topographically higher than in the surrounding area. This causes intense filtration and karst processes in the vault of the upland: above 100 m a.s.l. in an area of 1300 square km, lakes and rivers are almost non-existent. At about 80–90 m a.s.l., the base of the upland is marked by a circle of springs, from where many rivers and rivulets begin. Well-known springs include Norra–Oostriku, Kihme, Jäneda, Imastu, Lavi, Kulina and Simuna.
This makes the Pandivere Upland the most important watershed area of Estonia. During the spring, melting snow and rainfall fill the depressions and cavities with water, forming temporary lakes. The best known are the Võhmetu–Lemküla lakes near the Porkuni–Neeruti esker field, Heinjärv Lake in the Savalduma karst field, etc. After slow filtration of the water, these depressions become dry. The karst water system in the vault and upper part of the slopes of the Pandivere Upland was formed before the ice ages, but it continues to develop today.
The Pandivere water protection area
The hydrogeological conditions described above make the ground water of the Pandivere Upland vulnerable to pollution. Any pollution in the ground water would be distributed through the karst channels, reaching the springs and polluting both springs and rivers beginning from these springs. In these conditions, the ground water has almost negligible capability of self-purification. Careless construction and amelioration have opened some ground water channels and lowered the water level in large areas. This has caused drying of some low wells in farms and reduced the moisture of the soils. Early this Century, clean springs rich in water were important in choice of the location for alcohol distilleries. Today, the rivers feeding from the springs are favourable for trout farming.
During the last decades of Soviet power, the Pandivere Upland suffered from intense agricultural, military, industrial and communal pollution. The continuation of these trends would have lead to the pollution of the ground water and spring water, so that the nitrate load would have exceeded the health standard. The Pandivere water protection area was established in 1988, to preserve the unique ground water system, influencing the water supply over more than half of the Estonian territory. Consistent application of protective measures and the reduction of human impact have lead to the improvement of the quality of the water resources that were damaged and endangered.Details about this article
Created: 23.04.2001 18:45
Modified: 28.09.2012 16:35