Grundvatn Í Føroyum
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J A R Ð F E I N G I - F R Á G R E I Ð I N G 2 015 - 01 Grundvatn í Føroyum F . ebruar 2015: Ólavsdóttir, J. Mortensen, L. Heinesen, M. V. Øster, R. Mortensen, K. Johanneson, A. Brekkutún 1 · Postsmoga 3059 · FO 110 Tórshavn Tel: +298 357000 T-Postur: [email protected] FAROESE EARTH AND ENERGY DIRECTORATE Heimasíða: www.jardfeingi.fo Grundvatn í Føroyum Innihaldsyvirlit English summary ..................................................................................................................................... 3 Inngangur ................................................................................................................................................ 4 Grundvatn................................................................................................................................................ 5 Grundvatn í gosgrýti ................................................................................................................................ 6 Grundvatnsgoymsla ............................................................................................................................. 6 Legugosgrýti .................................................................................................................................... 6 Rivur................................................................................................................................................. 9 Jarðhitavøkstur (geothermal gradient) ................................................................................................. 12 Heitar keldur .......................................................................................................................................... 13 Heita vatnið í Kollafirði ...................................................................................................................... 15 Gagnnýtsla av heita vatninum í Kollafirði ...................................................................................... 19 Regluverk fyri útvinnan av grundvatni .......................................................................................... 19 Lóg um jarhitaskipanir ............................................................................................................... 20 Lógarheimild at útvinna grundvatn ........................................................................................... 21 Hitaskipanir og hitaflutningur innan í jørðini (geothermal systems) .................................................... 21 Lág-hitaskipanir ................................................................................................................................. 22 Rivustýrd ringstreymsskipan (convection) .................................................................................... 23 Leiðandi legugrýtisskipan .............................................................................................................. 24 Jarðtrýstshitaskipan (Geopressured geothermal systems) ........................................................... 25 Samandráttur og tørvur á framhaldandi kanningum ............................................................................ 25 Tilvísing .................................................................................................................................................. 27 Fylgiskjøl ................................................................................................................................................ 28 Fylgiskjal 1 ......................................................................................................................................... 29 Jarðhitaboringar ............................................................................................................................ 29 Fylgiskjal 2 ......................................................................................................................................... 30 Rivur............................................................................................................................................... 30 Fylgiskjal 3 ......................................................................................................................................... 32 Vísindaligar boringar ..................................................................................................................... 32 Fylgiskjal 4 ......................................................................................................................................... 33 Kjarnaboringar ............................................................................................................................... 33 Fylgiskjal 5 ......................................................................................................................................... 36 Boriprotokol frá á Traðarvegi 5b, Kollafjørður, yvir tí seinnu jarðhitaboringina við heitum vatni í Kollafirði (27 oC). ............................................................................................................................ 36 1 Grundvatn í Føroyum Fylgiskjal 6 ......................................................................................................................................... 37 Boriprotokol frá á Lygnnesi 10, Kollafjørður, yvir tí fyrru jarðhitaboringina við heitum vatni í Kollafirði (19 oC). ............................................................................................................................ 37 Fylgiskjal 7 ......................................................................................................................................... 38 Refraktiónsseismisk linja á Streymoynni, sum er lýst av Pálmason (1965). .................................. 38 Forsíðu mynd: Romica Øster, Jarðfeingi og William Bærentsen, í starvsvenjing á Jarðfeingi, máta hitalagið á heita vatninum í Kollafirði, oktober 2014. 2 Grundvatn í Føroyum English summary The investigation into groundwater issues has as yet been very limited in the Faroe Islands where surface water and a small amount of spring water have made up the main water resources so far, although a large number of springs have been known for a long time, as reflected in e.g. numerous place names around the islands. Spring water temperatures are normally around 8oC, although a number of warmer springs (11.25oC to 18.7oC) were observed already centuries ago in an area which indicates a potential anomalous E-W oriented geographical belt in the central part of the islands. This belt also encompasses the only one out of a total of three deep wells in the islands, the Vestmanna-1 well (660 m deep), in which the water temperature is considerably higher than average. During the last couple of years approximately 150 geothermal wells have been drilled in the Faroe Island. The average depth is c. 200 m and the wells are drilled for the purpose of heating individual family houses, etc. Some of these wells are artesian. In the summer of 2014, a geothermal artesian well in the village of Kollafjørður, Streymoy hit a relatively large amount of anomalously warm water (27oC) at 117 m depth. Initial water flow rates of 32.000 litre/hour (l/h) at first decreased relatively fast but have now (7 months later) almost stabilised at about 16.000 l/h. With the addition of 25 % of electricity power, the energy associated with this water amounts to the heating of around 150 family houses. Another artesian well, located less than 100 m from the other, also proved to produce relatively warm water, at c. 19oC, with a present flow rate of approximately 300 l/h. Based on the limited geological knowledge it is not possible at the moment to predict if the water flow into these two wells may be associated with some specific volcaniclastic layers in the region, or it may be controlled by some deep reaching faults, potentially in a so-called low temperature geothermal circulation system, as described in Iceland by Saemundsson et al. (2011). This hypothesis may be supported by a 50 years old refraction seismic survey conducted by Pálmason (1965) on Streymoy. In the Kollafjørður area a jump in basement depth was interpreted which may be speculated to represent a fault zone at basement level. Geological investigations into the complex matter of ground water issues in the Faroe Islands could form the basis for future use of ground water for clean water supply as well as geothermal energy. 3 Grundvatn í Føroyum The report concludes that groundwater has the potential to become a valuable resource for the Faroese society. Inngangur Higartil hava møguleikarnir at útvinna ella á annan hátt at gagnnýta grundvatn í Føroyum verið lítið kannaðir. Ein orsøk til tess er óivað, at føroyska undirgrundin er bygd upp av gosgrýti, t.e. fyri stóran part basaltfláum, sum ikki kunnu innihalda ella geva frá sær serliga nógv vatn. Tó hevur kelduvatn (í breiðari merking, t.e. vatn, sum rennur út í lendið innan úr jørðini ella undan svørðinum) verið brúkt sum drekkivatn, og fólk hava vitað um heitar keldur í árhundraðir. Hesar hava tey seinastu umleið 40 árini í ávísan mun verið brúktar sum vatnveiting til smoltstøðir. Í hesi frágreiðing verður heitið “kelda” eisini nýtt í nevndu merking, og tað skal tí ikki lesast í eini strangt heilsufrøðiligari merking, sum tekur atlit til vatngóðsku, framleiðsluhátt v.m. Hóast tað í tíðarskeiðum hevur verið hugt at grundvatnsspurninginum í ein ávísan mun ymsar staðir kring landið, til dømis tá borað varð fyri Sumbiar- og Norðoyatunlunum ella í sambandi