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channels. In some cases, pixels identified by the Band 5 classification method as open <br />water may also possess high NDVI* values attributable to emergent aquatic vegetation or <br />pixel mixing from verdant areas adj acent to the mapped pixel. The <3 acre water mask <br />was used to avoid the double counting of NDVI*-induced ET and open water E for the <br />same area. All NDVI* values for pixels classified as open water were masked out of the <br />final NDVI*-based ET mapping so that calculated open water ET rates took precedence. <br />An illustration of the results from the < 3 acre water body mapping is presented as Figure <br />9. <br />Comparable to ETg for vegetation, the Eg rate for these small water bodies (i.e. actual rate <br />less precipitation) was calculated using Equation 6 that employed ETo. <br />Eg_; of small water bodies = (ETo;- P,) (6) <br />Figure 9. <br />Band 5 water body <br />mask (< 3 acres) <br />applied over TM false <br />color mosaic. This <br />mask identified small <br />water bodies and <br />applied a separate E <br />value that more <br />accurately represents <br />the evaporation from <br />water surfaces. These <br />areas were eliminated <br />from further <br />consideration for water <br />use due to vegetation <br />(as NDVI* response). <br />16 <br />