Forsmark site investigation. Monitoring of brook water levels, electrical conductivities, temperatures and discharges January-December 2009

This document reports the monitoring of water levels, electrical conductivities, temperatures and discharges at four brook discharge gauging stations, and the monitoring of water electrical conductivity at the outlet of Lake Bolundsfjaerden in the Forsmark area. The report presents data from 1 January through 31 December 2009 and is a continuation of reporting from Johansson and Juston (2007, 2009), which covered the periods from 1 April 2004 through 31 March 2007 and 1 April 2007 through 31 December 2008, respectively. Long-throated flumes equipped with automatically recording devices were used for the discharge measurements. Every c. 14 days the water depths at the upstream edge of the flumes were measured manually by a ruler as a check. Electrical conductivity and temperature were automatically recorded and these parameters were also measured manually every c. 14 days with the site investigation field devices. SKB's Hydro Monitoring System (HMS) was used to collect and store all data. From HMS quality assured data were transferred to SKB's primary database Sicada. Measurements of levels, electrical conductivities and temperatures were made every 10 minutes (every 30 minutes for electrical conductivity at the outlet of Lake Bolundsfjaerden). For the calculation of discharge, quality assured water level data from the flumes were used. The calculation procedure included consolidation of the time series to hourly averages, screening of data for removal of short-term spikes, noise and other data that were judged erroneous. After the calculations were performed, the results were delivered to Sicada. The amplitudes of water level variations during this reporting period were 0.26-0.33 m at the four stations. The mean electrical conductivities varied between 26 and 41 mS/m at the four discharge stations. The electrical conductivity at the outlet of Lake Bolundsfjaerden varied between 53 and 188 mS/m during the period with the higher values at the end of the year and was on average 113 mS/m. The water temperatures varied between c. zero during winter up to c. 20 deg C during hot summer days with low discharge. The highest recorded discharge of the largest catchment (gauging station PFM005764) was 109 L/s and for the smallest catchment 38.2 L/s (gauging station PFM002668). The station PFM002667 was the only station that had a period with zero discharge; Sep. 19 - Oct. 8. However, the discharges in all stations were very low in late September and early October. The specific discharge for the largest catchment was 4.74 L/s/km2 (149 mm/yr) which is close to the estimated longterm average of 150-160 mm/yr. The specific discharge for the largest catchment, averaged over the five-year period 2005-2009 was 5.81 L/s/km2 (183 mm/yr). The station with the lowest specific discharge during 2009 was PFM002667; 3.79 L/s/km2 (120 mm/yr).