March 2008
Deering Conservation Commission
Surface Water Report 2007
This is now the 14th year of our current surface water testing program. It is part of our long time commitment to monitor and promote water quality for our citizens. The 2007 spring and fall test data sheets are included. For comparison, 2006 spring and fall and 2005 summer test sheets are also included.
Specifically for surface water testing, we test about 30 locations spring and fall for conductivity, ph, and temperature. These tests allow us to evaluate water quality for certain contaminants, especially evidence of road salt and of bacteria.
In general, conductivity under 50 is very good, with low contamination from all sources. In general, conductivity from 50 to 100 may be evidence of relatively low levels of contamination from all sources including natural sources such as from beaver, ducks, or dissolved minerals. In general, conductivity more than 100 may have man introduced contamination such as bacteria from septic systems or road salt. This test does not indicate the presences of other contaminants like gasoline.
Water quality continues to remain stable, and overall very good. There is a band of salt contaminated water traveling from the north and west into Deering Lake from Rt. 149, but this is mitigated by the influx of clean water from the west, primarily from protected lands in this water shed. Water volume will influence test values, so it is important to try and compare dry years to dry years if you wish to understand the significance of a specific value. Also it is important to understand that this scale is very sensitive, and 10, 20 or 30 points actually represents a very small change.
To get a feel for what the data means, compare one site over time.
Site 3-Longwood Rd-Contoocook River .
Fall 07 Spring 07 Fall 06 Spring 06 Summer 05
Conductivity 100 60 80 40 80
Water Volume low high high/avg high low
What this suggests is that underlying contamination is relatively stable, and changes are related to water volume.
Site 34-Reservoir Rd-Mariotta’s Brook
Fall 07 Spring 07 Fall 06 Spring 06 Summer 05
Conductivity 260 180 160 110 540
Water Volume low high high/avg high low
What this suggests is that underlying contamination from road salt washing down from Rt 149 is relatively variable, and large changes are both related to water volume and the amount of salt used that winter.
Restraint in town use of salt and the sustained efforts of our community to manage responsible growth has substantially preserved our overall water quality to date. As a recent impact study indicates, even one poorly planned development, with a few extra houses situated to close to the wetland system can have a dramatic and measurable reduction in the clarity of Deering lake miles away.
For more information call Ed Cobbett at 464-3265 or Gary Bono at 464-5107
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