When Tropical Storm Irene hit New Hampshire just over two months ago, most residents were either evacuating or hunkering down and protecting their property, glad at least that the storm no longer had hurricane strength. For some researchers at Plymouth State University, though, the storm was an opportunity to study the long-term effects of floods.
Hydrologists and geologists from the university’s Center for the Environment spent days collecting water samples throughout the Pemigewasset River watershed. The goal? To determine how a large storm event releases nutrients and metals from the soil and moves them through the water system. Because the watershed has relatively few dams, it’s easier to study the movement of the phosphorus, carbon, aluminum, and other elements that may be released. Some of the elements may have long-ranging effects on forest growth, for example—either providing nutrients or inhibiting growth. Preliminary results indicate that at least 26 tons of dissolved nitrogen and 41 tons of dissolved aluminum were moved out of the watershed by Irene.
Irene was one of the largest storms in the watershed’s recorded history. Soils were still wet from previous storms, so relatively little rainfall was absorbed, increasing the level of flooding.