Parker-Ipswich-Essex Rivers Restoration Partnership

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A US Geological Survey (USGS) study in the Ipswich River basin proposed a threshold below which summer streamflows become ecologically damaging based on the dewatering of important stream habitat (D. S. Armstrong et al. 2001). While this threshold of 0.42 CFSM (cubic feet per second of water per square mile of watershed) was developed specifically for the Ipswich, we believe it is reasonable to apply the same threshold for evaluating conditions in the Parker an Essex watersheds as well based on their similarities in location, size and character. The USGS operates three realtime streamflow gauges in the PIE-Rivers Region on the Ipswich (2) and Parker (1) Rivers. The MA Division of Ecological Restoration operates an additional 3-6 gauges with operation varying from year to year based on funding and volunteer availability.

*Streamflow is heavily influenced by rainfall and rainfall patterns vary greatly from year to year. Average rainfall and flood frequency in the region has increased measurably since the 1970s (Collins 2009; W. H. Armstrong et al. 2011) and is expected to further change as a result of climate change. We will use available weather data to attempt to normalize flow data for inter-annual and longer-term variations in rainfall.

Availability: PI                  Frequency: Continuous (since 1930s for USGS gauges)

Response Variable(s): Count of summer days (July-Sept) below ecological streamflow threshold


Armstrong, D.S., Richards, T.A. & Parker, G.W., 2001. Assessment of Habitat, Fish Communities, and Streamflow Requirements for Habitat Protection, Ipswich River, Massachusetts, 1998-99,

Armstrong, W.H., Collins, M.J. & Snyder, N.P., 2011. Increased Frequency of Low-Magnitude Floods in New England. Journal Of The American Water Resources Association, 01930, pp.1–15.

Collins, M.J., 2009. Evidence for Changing Flood Risk in New England Since the Late 20th Century. JAWRA Journal of the American Water Resources Association, 45(2), pp.279–290. Available at: [Accessed April 4, 2012].