**StreamStats in Massachusetts**

New peak-flow regression equations were made available in StreamStats version 3 for Massachusetts on May 12, 2017 and in version 4 on June 14, 2017. The new equations can be used for estimating the 50-, 25-, 10-, 2-, 1-, 0.5, and 0.2-percent annual exceedance probabilities (Zarriello, 2017). StreamStats for Massachusetts also can be used to estimate the long-term 99-, 98-, 95-, 90-, 85-, 80-, 75-, 70-, 65-, 60-, 55-, and 50-percent duration flows, the 7-day, 2-year and the 7-day, 10-year low flows, and the August median flow for ungaged sites (Ries and Friesz, 2000). The application also includes an equation for estimating the probability of a stream flowing perennially (Bent and Steeves, 2006), and equations for estimating bankfull geometry—width, mean depth, cross-sectional area – and bankfull discharge (Bent and Waite, 2013). The reports below present the equations used to estimate the statistics, describe the errors associated with the estimates, and describe the methods used to develop the equations and to measure the basin characteristics used in the equations. Users should familiarize themselves with the report before using StreamStats to obtain estimates of streamflow statistics for ungaged sites.

- Ries, K.G., III, and Friesz, P.J., 2000, Methods for estimating low-flow statistics for Massachusetts streams: U.S. Geological Survey Water Resources Investigations Report 00-4135, 81 p.
- Bent, G.C., and Steeves, P.A., 2006, A revised logistic regression equation and an automated procedure for mapping the probability of a stream flowing perennially in Massachusetts: U.S. Geological Survey Scientific Investigations Report 2006-5031, 107 p., 1 CD-ROM.
- Bent, G.C., and Waite, A.M., 2013, Equations for estimating bankfull channel geometry and discharge for streams in Massachusetts: U.S. Geological Survey Scientific Investigations Report 2013–5155, 62 p.
- Zarriello, P.J., 2017, Magnitude of flood flows at selected annual exceedance probabilities for streams in Massachusetts: U.S. Geological Survey Scientific Investigations Report 2016-5156, 54 p.

The equations from each report are applicable for most areas of Massachusetts except eastern Buzzards Bay, Cape Cod, and the Island regions, and the main branches of the Connecticut and Merrimack Rivers. Estimates obtained from the equations assume natural flow conditions at the site.

For the equations from Ries and Friesz (2000), StreamStats reports the uncertainty of the estimates for basins with drainage areas between 1.61 and 149 mi^{2}. For equations from Bent and Steeves (2006), StreamStats reports the uncertainty of the estimates for basins with drainage areas between 0.01 and 1.99 mi^{2}. For the equations by Bent and Waite (2013) StreamStats reports the uncertainty of the bankfull estimates for basins with drainage areas between 0.60 to 329 square miles. For the equations by Zarriello (2017), StreamStats reports the uncertainty of estimates for basins with drainage areas between 0.16 to 512 square miles. Errors for basins with drainage areas beyond these bounds are unknown. The prediction intervals that are presented for the bankfull estimates were determined using equations that differ from those used by Bent and Waite (2013), and as a result, the presented prediction intervals are substantially wider than the actual intervals. Limited trials indicate differences in prediction intervals of between 30 and 90 percent.

Click on this link to obtain general information on the Massachusetts application, as well as specific sources and computation methods for basin characteristics.

StreamStats for Massachusetts was developed in cooperation with the Massachusetts Department of Conservation and Recreation, the Massachusetts Department of Environmental Protection, the Massachusetts Geographic Information System, and the Massachusetts Environmental Trust.