Utvärdering av vattenkemisk data från Borgholm kommun och dess relation till geologiska förhållanden och markanvändning
Sammanfattning: Due to unusually low precipitation during late autumn and winter of the year 2015/2016 the groundwater levels of south-eastern Sweden have reached the lowest levels ever recorded since measurements began in 1968. In the month of April in the year 2016 the Geological Survey of Sweden (SGU) made a public statement to the media announcing that unless substantial amounts of precipitation is added during the spring of 2016 there is a risk of shortage of drinking water during the summer of 2016. Low groundwater levels would not only result in a decreased amount of drinking water available for withdrawal but would also have the secondary effect of increasing the content of undesired chemical elements in the water as the water becomes less diluted at lower quantities. Borgholm is a muncipality located on the island of Oland in Sweden and belongs to the areas that would be affected should a water shortage occur due to the increased demands that the summer tourism ensues. The county has a large quantity of data from preformed water chemistry analyses in solitary wells, which have made up the basis of the work on this paper. The data has not been properly evaluated in the past. Now the municipality wishes to make a general assessment of the hydrological circumstances within the municipality in order to later be able to make appropriate assumptions as to where to increase current water withdrawal or where to place new water catchment areas for drinking water. Through separation of data in Excel 2007, conversion of data points into maps in ArcMap 10.2.2 and creation of bar charts and tables in Excel 2007 areas with low or high levels have been defined as well as a general comparison of what values are normal within the region been made on the basis of the report “Bedömningsgrunder för grundvatten” (SGS-report 2013:01) for the elements fluoride, chloride, nitrate, nitrite and sulphate. Results show increased levels for the elements chloride, nitrate and sulphate and generally low levels for fluoride and nitrite. While nitrate and sulphate generally follow the region norm for the percentages of levels chlorine, fluoride and nitrite seem to differ and stray from the regional average. Conclusions of the work performed have deduced that the municipality should look into increasing their water withdrawal in their current water catchment area in Byxelkrok as well as locating new water catchments within the northern and under some conditions also the southern part of the municipality. An additional alternative includes investigating the possibility of re-infiltrating surface water in order to gain artificially created groundwater. Owners of solitary wells should look into the possibility of deepening their current wells while residents and visitors to the municipality should ration their drinking water usage this summer in order to save on water resources.
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