If a Rain Drop Falls in the Forest, does it Affect Northampton?

14 May

Over the last few weeks of this semester, students in our Ecohydrology class at Smith College have taken on challenging hydrologic questions that are relevant to our community. In this post, Sophie D’Arcy, Natalie Forrest Gill, and Lauren Weston address the question: What is the effect of logging and forest regrowth on the amount of water available in Northampton’s reservoirs during the month of August?

 R_WWdam
Ryan and West Whately dam

In the winter of 2013, the City of Northampton implemented its Forest Management Plans by selectively logging the Ryan, West Whately, and Mountain Street watersheds(1) – the area of land that drains water to Northampton’s reservoirs. This action sparked a debate about the impacts of logging a public resource and its effect on the quality of the environment.

Forests play an important hydrologic role by influencing the way in which water flows over the landscape and through the soil, impacting both water quality and quantity. Maintaining the health and diversity of the forest promotes high water quality by reducing processes such as erosion and sedimentation(2). The forest management plans were developed with the intention of maintaining water quality, with little impact on quantity(3). One such practice involves the selective cutting of unhealthy or disease-vulnerable species.

The forest management plans outline silvicultural practices to be used in the forested watersheds of the town’s three reservoirs over the coming years(1). Adhering to responsible forest management practices developed for the northeastern United States, the city has determined that 26.8% of the Ryan and West Whately and 4% of the Mountain Street watersheds are suitable for cutting(1). Some of these practices include refraining from cutting near vulnerable water systems, on steep land, and in areas where growth of invasive species are likely to occur(1).

Although Northampton is primarily focused on maintaining water quality, an analysis of the quantity of available water is relevant because residents of Northampton are often subjected to water usage restrictions in the month of August. Several studies have determined that reduction in forest cover results in an increase in water yield(2); in the case of Northampton, this would correspond to an increase in the city’s water supply. This is due to the interception and transpiration of water by trees, reducing the amount of water flowing into the reservoirs.

According to the forest management plans, 341.5 acres are intended to be cut between 2012 and 2017(1). At most, the city will cut 25% of each sub-watershed over a ten year period(1).Studies performed in experimental watersheds in other parts of the Northeast suggest that increases in water yield cannot be detected from reductions in forest cover of less than 20%(4). Therefore, it is not likely that any change to the amount of water available to Northampton will be noticeable.

Even if a change in the quantity of water in the reservoirs does occur, water usage restrictions would not be directly affected. This is because water restrictions are based on the average daily stream flow at a stream gauge on the Mill River, which is not directly connected to the reservoirs(5).

Perhaps the best way to move forward is to monitor the amount of water available in these reservoirs to determine if, in fact, the management practices have caused changes. If the water yield increases, the city may then reconsider its methods of water restriction determination. Continuous direct measurement of the water depth in the reservoirs of the forested watersheds would allow for a clearer rationale behind usage restrictions for the community.

The debate over logging in Northampton is not over; conversations regarding the stakeholders and decision makers involved in these plans and the true effects on the watershed will surely continue.

Works Cited

[1] City of Northampton, Massachusetts. Department of Public Works. Combined Forest Stewardship Overview: “Ryan Reservoir & West-Whately Reservoir Watersheds” and the “Mountain Street Reservoir” Watershed , Land of the City of Northampton, Department of Public Works, Hatfield, Conway, Whately and Williamsburg, MA. By Michael Mauri. Northampton MA: n.p., 2012.Watershed Protection and Management. City of Northampton, Massachusetts, 21 June 2012. Web. 25 Apr. 2014.
[2] Hewlett, John. Principles of Forest Hydrology . 1969. Reprint. Athens, Georgia: University of Georgia Press, 1982. Print.
[3] Correspondences with Nicole Sandford. Senior Environmental Scientist. City of Northampton,Department of Public Works.
[4] Brown, Alice E., Lu Zhang, Thomas A. McMahon, Andrew W. Western, and Robert A. Vertessy. “A Review of Paired Catchment Studies for Determining Changes in Water Yield Resulting from Alterations in Vegetation.” Journal of Hydrology 310 (2005): 28-61. ScienceDirect. Elsevier. Web. 24 Apr. 2014.
[5] City of Northampton, Massachusetts. Department of Public Works, Water Division. Water Restriction Policy. Ed. Edward S. Huntley. City of Northampton, Massachusetts, 27 Mar. 2013. Web. 23 Apr. 2014.

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