The extraction of mineral resources below the groundwater table is related to water removal from surface and underground mines. Water drainage is considered the main process for keeping mining sites dry or suitable for mining. Parameters of depression cone and its impact radius are factors influencing decision makers. Water collection system, pumping station and sedimentation ponds are the main tools for water drainage. The quantity of drainage water depends on the amount of precipitation, surface water, soil water and groundwater. Water table in wells, the amount of pumped-out water and the amount of water in the Toolse River have been measured from 2005 to 2009, and chemical components in river water have been analysed. Analyses have shown that water is often repumped from the mining sites. Operating surface mines in the Ubja region act as water reservoirs. Accumulated water is directed to the Toolse River increasing its flow. Quality indicators in the Toolse River of the Ubja region are in accordance with water normatives except total P content downstream the Toolse River.
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2. Monitoring of Kunda mining region, water and bottom sediments of the Toolse River in 2007. Report Department of Mining of TUT. Tallinn, 2008, 72 p. [in Estonian].
3. Iskül, R., Kaeval, E., Robam, K., Sõstra, Ü., Valgma, I. The origin and amount of removal water in the Ubja oil shale opencast mine and its influence to the Toolse River. – In: Book of abstracts: International Oil Shale Symposium, Tallinn, Estonia, 8–11 June, 2009. Tallinn, 2009, 83.
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