18 February 2011

The Global Environmental Flow Calculator

The Global Environmental Flow Calculator (GEFC) is a software package for desktop rapid assessment of Environmental Flows (EFs). The EF estimation technique in GEFC is using monthly time step series reflecting “natural” / unregulated flow conditions and its corresponding Flow Duration Curve (FDC)- a cumulative distribution function of flows. The FDC is represented by 17 percentage points on the probability (X) axis. EFs aim to maintain an ecosystem in, or upgrade it to some prescribed or negotiated condition - “Environmental Management Class (EMC).” The higher the EMC, the more water is needed for ecosystem maintenance and more flow variability needs to be preserved. Six EMCs are used in GEFC, ranging from “Unmodified” to “Critically Modified.” Each EMC is represented by its unique FDC. The FDC for each class is determined by the lateral shift of the original reference FDC to the left along the probability (X) axis by one percentage point. Each EMC is effectively an EF scenario. The EMC best suited for the river in question may be selected-based on expert judgment. A FDC established for each EMC can be converted into an EF time series.

The EF estimation in the GEFC package includes 4 subsequent steps:
  1. Select a Data Source
  2. Display Hydrological Characteristics
  3. Calculate EFs
  4. Display Estimated Reference and Environmental Monthly Flow Time Series
Detailed ‘Help’ facility is built into the package. A free copy of the software (on DVD, which also includes the simulated global flow database) may be obtained from Mrs Nishadi Eriyagama (n.eriyagama@cgiar.org).
GEFC is a product of the collaborative project between IWMI and the Water Systems Analysis Group of the University of New Hampshire (UNH - http://www.wsag.unh.edu/). Enquiries on the package may be directed to Dr. Vladimir Smakhtin (v.smakhtin@cgiar.org).

The above image is an illustration of progressive zooming in the Global Environmental Flow Calculator from the main screen to the individual river basins and data cells seen at a higher zoom level (b) Display of the actual selected monthly flow data and other hydrological characteristics / time series calculated from it.

Above, The graphed and tabulated Reference and Environmental Flow Duration Curves (b) Display of Estimated Reference and Environmental Flow Time Series

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