The two graphs above show water level height and percent new water that entered each river during Hurricane Sandy on October 30, 2012. The Israel River's peak in water composition lagged behind the peak in water level by 4 hours and 12 minutes. Keene's Beaver Brook, lag time between peaks was only 42 minutes. One hypothesis for this difference is that urban surfaces are less permeable than most of the surfaces which they replace, so rain has less interaction with soils in urban surfaces. Check back for other comparisons. I will be running analysis and posting new graphs.
Monday, December 10, 2012
|Hobo U24 Datalogger configuration in Blanchard Brook pool|
|Left-Right: Hobo U24 Datalogger, YSI 85, Oakton EC 11+|
Early in November, we installed LoVoTECS Hobo Water Level and Conductivity Loggers in a small stream called Blanchard Brook in Walpole, NH. The loggers were installed as part of a quality control group to study the variations among the dataloggers. The installation method differs from the rest of the network, in that five conductivity loggers and one water level logger were deployed in a one foot section of a pool in Blanchard Brook. The loggers are collecting data points every minute rather than every three or fifteen. Each data set will be compared to identify variations among individual loggers. Since we’ve been observing the electrical conductance of Blanchard Brook, the average conductivity range has been between 100 and 200 us/cm.
In addition to the comparison of the individual units, we are also capturing field conductivity readings using two styles of field meters and collecting a grab sample at the time of the field readings to note the variation between field, lab and the datalogger values.
Following the deployment in Blanchard Brook the logger group will be moved to Claybrook in Plymouth to make the same observations. Claybrook has an average conductivity range from 30-60 us/cm. Finally the loggers will be placed in a series of three standards to test their accuracy against the known solutions in a controlled environment.
Stay tuned to the blog to follow the progress and results of the Quality Logger Group.
Wednesday, November 28, 2012
Saturday, November 17, 2012
A pattern that is emerging around New Hampshire is that specific electrical conductance is highest at low flows and becomes diluted as flows increase. This is because there are higher solute concentrations in soil water or groundwater and lower solute concentrations in rainwater. Higher solute concentrations in groundwater or soil water are partly natural, caused by dissolution of naturally occurring minerals. However, sometimes higher solute concentrations are elevated by human inputs of minerals, particularly sodium chloride as road salt. Natural or human-caused, this dilution pattern can tell us about how much groundwater contributes to a stream. But, I will leave this discussion to Ashley Hyde for another time. In the meantime, here is a picture of dilution from a downstream reach of the Israel River (or Israel's River). I am writing code to produce these pictures for each site, and this is the first picture I've been able to pull together. I was excited, so I thought I would share.
Posted by Mark Green at 2:18 PM
Monday, November 12, 2012
We are building computer code (R is our preferred scripting language) to summarize the huge amounts of data arriving from the LoVoTECS sensors. We are going to publish graphs here to share interesting patterns in the data. Here are a few months.
There is a clear positive relationship between monthly median water temperature and specific electrical conductance. Our warmer streams have more solutes in them - the role human activities play in driving this pattern is a future question that we will be addressing.
Posted by Mark Green at 8:57 PM