title: Four years of continuous monitoring of the Meirama end-pit lake and its impact in the definition of future uses.
abstract: Following the technical closure of the brown lignite Meirama mine (NW Spain) in April 2008, the reclamation of the mined area is being accomplished with the controlled flooding of its large pit. During the first 7 months of flooding, the sequential arrest of the ground water dewatering system led to the growth of an acidic water body of about 2 hm3. Since October 2008, the surface waters from some local streams have been diverted towards the pit so that these have become the major water input in the flooding process. Surface water has promoted a major change in the chemical composition of the lake water so that, at present, its surface has a circum neutral pH, net alkalinity, and low conductivity. At present, the lake has slightly more than one half of its final volume, and it is expected the overflow in 3 to 3.5 years. The lake is meromictic, with a sharp chemocline separating the acidic monimolimnion (pH≈3.2, acidity≈150 mg CaCO3/L, κ 25≈2.4 mS/cm) from the main water body (pH≈6.5, alkalinity≈15 mg CaCO3/L, κ 25≈0.3 mS/cm). Oxygen is being depleted at the bottom of the lake so that the monimolimnion became anoxic in January 2011. Above the chemocline, the composition of the lake is similar, but not identical, to that of the flooding stream waters. Close to the surface, some constituents (pH, metals) show strong seasonal variations in coincidence with the phytoplankton growing periods. Those parameters whose limits are legally prescribed comply with the corresponding water quality standards, and they are also consistent with the forecasting results obtained in early modeling. At present, a project considering the construction of an uptake tunnel to exploit the lake is being developed for the emergency water supply of the metropolitan area of A Coruña.
authors.affiliation: Water and Environment Engineering Group (GEAMA), Universidade da Coruña, Campus de Elviña s/n, 15192, A Coruña, Spain, jdelgado@udc.es.
authors.forename: J
authors.initials: J
authors.lastname: Delgado-Martin
authors.forename: R
authors.initials: R
authors.lastname: Juncosa-Rivera
authors.forename: I
authors.initials: I
authors.lastname: Falcón-Suárez
authors.forename: J
authors.initials: J
authors.lastname: Canal-Vila
mesh_terms: D004190:Disasters; D004784:Environmental Monitoring; D005618:Fresh Water / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D060106:Lakes / Q000737:chemistry; D008670:Metals / Q000032:analysis; D008906:Mining; D010839:Phytoplankton / Q000254:growth & development; D012621:Seasons; D013030:Spain; D014874:Water Pollutants, Chemical / Q000032:analysis*; D014877:Water Pollution, Chemical / Q000706:statistics & numerical data; D014881:Water Supply / Q000706:statistics & numerical data
chemical_list: D008670:Metals; D014874:Water Pollutants, Chemical