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Maine StreamStats

StreamStats for Maine was developed in cooperation with the Maine Department of Transportation.

StreamStats for Maine can be used to estimate (1) instantaneous flood discharges with exceedance probabilities of 0.5, 0.2, 0.1, 0.04, 0.02, 0.01, 0.005, and 0.002 (equivalent to 1.25-, 1.5-, 2-, 5-, 10-, 25-, 50-, 100-, and 500-year recurrence intervals, respectively) for small and large streams; (2) monthly and annual mean flows, as well as flows at the 1-, 5-, 10-, 25-, 50-, 75-, 90-, 95-, and 95-percent exceedance probabilities, and (3) 7-day, 10-year low flows for ungaged, unregulated, rural streams throughout Maine. In addition, StreamStats can estimate (1) June median flows for Southern Maine; (2) August median flows for regions of Southern, East Coast, and Aroostook County, Maine; baseflow throughout Maine south of  46º 21′55″ N latitude; and bankfull discharge, width, depth, and area for streams in Central and Coastal Maine. The reports below present the regression equations used to estimate the flow statistics, describe the errors associated with the estimates, and describe the methods used to develop the equations and measure the basin characteristics used in the equations. Limitations of the methods are also described in the reports; for example, all of these equations are appropriate only for ungaged, unregulated, rural streams in Maine. Users should familiarize themselves with the reports below before using StreamStats to obtain estimates of streamflow statistics.  

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

Peak-Flow Frequency Estimates: Peak-flow regression equations are available for the entire State of Maine and appear in a table with a heading of “Peak Flow Statistics” (Lombard and Hodgkins, 2020). 

Baseflow Estimates: Baseflow estimates are computed as mean August baseflow per square mile of drainage area on user-selected sites throughout Maine south of 46º 21′55″ N latitude. Units are cubic feet per second per square mile of drainage area.   

June and August Median Flow Estimates: StreamStats often provides two estimates of the June and August median flows (JUND50 and AUGD50) for user-selected sites in some parts of Maine. One set of estimates, which are available state-wide, are determined by equations from Dudley (2015), and appear in tables with headings of “Statewide June Flow Statistics” and “Statewide August Flow Statistics.” The other estimates are determined by equations from Lombard, Tasker, and Nielsen (2003) for areas in Eastern Aroostook County (AUGD50 only), Lombard (2004) for areas in Eastern Coastal Maine (AUGD50 only), or Lombard (2010) for areas in southern Maine (JUND50 and AUGD50), and appear in a table with a heading of “Regional Median Flows Statistics.” In cases where two estimates are available, the estimates from the “Regional Median Flow Statistics” table should be the preferred estimates. 

Uncertainty: StreamStats reports the uncertainty of the flow estimates for ungaged basins when basin characteristics for selected sites are within the ranges of the basin characteristics of the streamgages that were used to develop the regression equations. Errors for basins with basin characteristics that are beyond these bounds are unknown. The applicable ranges of the basin characteristics are provided in the StreamStats outputs and messages are provided when basin characteristics are outside of the applicable ranges. Particular caution should be used for very small basins, as drainage-area delineations can have large percent errors due to their small size and estimates from regression equations for small basins typically involve large extrapolations beyond the data used to develop the equations. Delineations for very small basins should be checked in the field. 

Base layers Information: Several GIS data datasets were created in 2023 to be implemented into the StreamStats application to allow for more accurate watershed delineations. These data were compiled from the high-resolution National Hydrography Dataset (NHD) and the Maine Lidar-Derived Watersheds (Sturtevant and Schoen, 2022). These datasets can be found in the Data Release below and include elevation rasters, flow accumulation rasters, flow direction rasters, stream definition cell threshold raster, and streamgage boundary layers: