An Interactive, GIS-Based Application to Estimate Continuous, Unimpacted Daily Streamflow at Ungaged Locations in the Connecticut River Basin

RCN Topic
Instream Flow

Work from this project allows users to identify a stream reach of interest in the Connecticut River basin and obtain estimated continuous daily, unregulated or “natural” streamflow at the selected location. The application spans the entire Connecticut River basin, including the states of Connecticut, Massachusetts, New Hampshire and Vermont. This work expands on a method developed for Massachusetts to estimate daily streamflows at ungaged locations. The project is divided into two tasks: 1) the refinement of the methods to include gages in the northern portion of the Connecticut River Basin, and 2) the development of a seamless, multi-state point-and-click GIS application to interactively estimate streamflow at ungaged locations in the Connecticut River Basin.  This project integrates current work being completed in cooperation with the Massachusetts Department of Environmental Protection and the Connecticut Department of Environmental Protection.

Streamflow information is critical for addressing any number of hydrologic problems. Often, streamflow information is needed at locations that are ungauged and, therefore, have no observations on which to base water management decisions. Furthermore, there has been increasing need for daily streamflow time series to manage rivers for both human and ecological functions. To facilitate negotiation between human and ecological demands for water, this paper presents the first publicly available, map-based, regional software tool to estimate historical, unregulated, daily streamflow time series (streamflow not affected by human alteration such as dams or water withdrawals) at any user-selected ungauged river location. The map interface allows users to locate and click on a river location, which then links to a spreadsheet-based program that computes estimates of daily streamflow for the river location selected. For a demonstration region in the northeast United States, daily streamflow was, in general, shown to be reliably estimated by the software tool. Estimating the highest and lowest streamflows that occurred in the demonstration region over the period from 1960 through 2004 also was accomplished but with more difficulty and limitations. The software tool provides a general framework that can be applied to other regions for which daily streamflow estimates are needed.

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