GLOBE hydrology SPECIAL report:
Tabor Academy, Marion, MA
Dear Students,
Having exchanged a number of email messages with teacher Richard Harlow of Tabor Academy, we decided to present some of what we're looking at to you. Tabor Academy reports data from three sites near their school. In this report, we hope to present Tabor Academy's sites so you can see the kinds of things that we've been looking at. Although all three sites are located fairly near each other, they are each parts of very different hydrologic regimes.
Tabor Academy GLOBE hydrology sites:
Harvey's Folley is a small pond located on the grounds at Tabor Academy. It is fed by groundwater.
Teacher Richard Harlow's Observations:The pond is in an open area surrounded on three sides by playing fields and one side by houses with no trees on the edge of the pond and only a couple at the periphery of the fence that surrounds the pond. The pond is used to water the schools playing fields (not for drinking water) during the summer. At the present time this site is not being used by the school. However, the pond does have an exit that is between two concrete abutments that have grooves on each side where wooden slats can be lowered to dam or raise the level of the pond. When water exits the pond it runs down into a small marshy area, under a road and into a saltmarsh. This same dam could also prevent saltwater from gushing into the pond during a hurricane. The banks of the pond are grass and the water edges of the pond have rushes, Juncus sp. grasses and in the pond proper, there is an abundance of pond vegetation. At present the water clarity has been excellent. We take our samples from a bucket that is designated just for these tests and therefore is not used for anything else.
The curious thing about the water at Harvey's Folley is that it has an unusually high electrical conductivity. A background check into the history of the pond revealed that there is a large deposit of iron at the bottom of the pond approximately where the groundwater enters the pond. Under some conditions this might have been the answer, however this is probably not the case at Harvey's Folly. The pH of the water and the levels of oxygen present in the water (pH > 3, and significant D.O.) indicate that any iron present would be in the form Fe(III) which is relatively insoluble in water. Another perhaps more likely possibility is that the pond is experiencing a form of marine saltwater intrusion. Often when groundwater sources near the ocean are pumped for drinking water, they cause saltwater to enter into the system. This saltwater can cause significant rises in the conductivity of a system because of the ability of Na+ and Cl- ions to conduct electricity.
Teacher Richard Harlow's Observations:Sippican Brook is a medium sized tidal river. We take our measurements from a road bridge over the river. The bucket is lowered into the current, filled, brought to the surface and dumped, than filled again. The second filling of the bucket is the water that we sample. We use the same format at all three sites. The location of the bridge is up stream far enough so that the only time that saltwater has been noticed at this site is when there is a phenomenally high tide (full moon or new moon). However, when we tested the surface water during one of these moon tides it tested what we considered to be normal for the river with a 5S of 60. If there had been any mixing of saltwater we would have noticed it especially during that day. The banks of the river are wooded, and the color of the water is a light brown, which gives me some cause for concern as to what our real end point is for DO. All our measurements have been very consistent, which simply emphasizes the anomalous nature of our first site.
Teacher Richard Harlow's Observations:Dagget Brook is a small but channeled deep brook. Again our sample is taken from a bridge that crosses the brook. The brook drains Bear Swamp and empties into the upper end of Sippican River. The distance from where we take the sample and where it empties into Sippican River is about one quarter mile, and the distance from where the brook is and our Sippican River site is about 2 miles. It is completely fresh, but also has a color the same as Sippican River, a light brown. There is NO odor to any of these water sites, as a matter of fact just the contrary, there is a rather refreshing smell. This brook runs through deciduous woods. Again the brook almost mirrors Sippican River, with no more than 6.8 mg/L CaCO3 and a slightly lower pH of 5.9 on our last visit.
If you have any questions to ask about the data set and how the analysis is going, feel free to send email to Chris (cgutmann@hwr.arizona.edu) or me (roger@hwr.arizona.edu).Sincerely,
Roger Bales
Professor of Hydrology & Water Resources
University of Arizona
