US Army Corps of Engineers
Hydrologic Engineering Center

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HEC-EFM Plotter



In addition to “Standard” and “Custom” plots, HEC-EFM Plotter can also be used to investigate concepts such as ecosystem services (ecovalues), seasonality (dates), and tallies (summations) of values such as habitat provided, recreation user-days, or water supply shortages. These data can also be viewed as scenario comparisons (shifts).


"Ecovalues" are measures of how flow regimes performed for each relationship. The figure below displays ecovalues for two flow regimes and shows that the Gaged flow regime (orange) provided generally higher and more consistent ecovalues. Ecovalues offer insights regarding ecosystem services provided and how those services differ between flow regimes.


"Date" is based on the day and month when the statistical parameters of a relationship are met. Dates offer insights regarding when ecosystem dynamics occur and how that seasonality differs between flow regimes. In the figure below, dynamics associated with big bass winter habitat relationship tend to occur slightly earlier for the Gaged flow regime (green).


“Summations” track accumulations of ecovalues provided. Summations begin with a daily time series of ecovalues, which is quite different than the frequency-based approaches often used in EFM. By considering and tallying daily ecovalues, summations offer insight to services provided by whole seasons and flow regimes. Image below shows a summation related to fish habitat.


“Shifts” refer to comparisons between an active non-reference flow regime and the reference flow regime. In many studies, this is often called alternative analysis or scenario comparisons. Shifts are computed for ecovalues, dates, and summations. Figure below shows a summation shift related to fish habitat for the Gaged flow regime, which begins with a surplus and then accumulates an ecovalue deficit over its period of record.