The Forced Evaporation (FE) Analysis capability has been developed to quantify increased evaporation induced by increased water temperatures due to releases from thermoelectric power plants. These power plants withdraw cooling waters, which once run through the plant and are returned/discharged to rivers or lakes at a higher temperature than the ambient water temperature. This higher temperature water causes additional evaporation (forced evaporation) from the river or lake. This additional evaporation is counted as water consumption by regulators as it is no longer available to downstream users.
Evaporation is dependent on wind speed, atmospheric humidity, and water temperature. There are a number of methods to compute FE using different wind functions as listed in 114163726. The wind functions are computed using data contained in the ASER file (ASER.INP) in EFDC.
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IEVAP
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Evaporation Approach
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General Usage
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0
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Do Not Include Evaporation
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1
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Use Evaporation from ASER
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Measured or Externally Estimated
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2
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EFDC Original
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3
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Ward, 1980
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Cooling Lake
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4
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Harbeck, 1964
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Cooling Lake
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5
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Brady et al, 1969
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Cooling Pond
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6
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Anderson, 1954
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Large Lake
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7
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Webster-Sherman, 1995
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Lakes
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8
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Fulford-Sturm, 1984
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Rivers
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9
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Gulliver-Stefan, 1986
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Streams
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10
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Edinger et al., 1974
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Lakes/Rivers
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11
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Ryan-Harleman 1974
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Lakes/Rivers
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Once temperature is activated and the correct Surface Heat Exchange Sub-Model option has been selected the user can choose which evaporation approach is desired. Even if evaporative losses are not a major concern, the evaporative mass fluxes should normally be activated for most models.
Heat flux due to evaporation is always included for the Full Heat and the Equilibrium Temperature (W2) options.
EFDC_DSI/EFDC_Explorer Forced Evaporation (FE) toolset results have been compared to the Electric Power Research Institute's (EPRI) FE estimates. EPRI's once through cooling FE analysis for river discharges is based on a USGS report on water consumption by thermoelectric power plants (USGS, 2013; EPRI, 2013).
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Figure 1 Forced Evaporation: Evaporation Options for Water Balance.
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The user can also produce summaries of evaporation and forced evaporation using the Tabular Summary button as shown in Figure 2.
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Another new and related feature in EE7.3, is the user can now generate time series of the differences in water column results as shown in 114163726. DT means "delta temperature".
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Habitat models are designed for a wide variety of planning applications where habitat information is an important consideration in the decision-making process. EEMS now supports two new types of habitat analysis tool. These are in addition to the existing temperature limit and depth criteria tool in ViewPlan that was initially implemented to support studies on manatee populations in the Chassahowitzka Estuary. The two new tools generate time series critical limits, as well as support the state-of-the-art Instream Flow Incremental Method. These two methods are described below.
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Figure 1 Model Analysis: Habitat Analysis form.