SPATIAL VARIATIONS OF WATER LOSS DURING DROUGH A CASE STUDY1

Authors

  • Tiao J. Chang,

    1. Respectively, Professor, Civil Engineering Department, Ohio University, 147 Stocker Center, Athens, Ohio 45701; Environmental Specialist, Ohio Environmental Protection Agency, 122 South Front Street, Columbus, Ohio 43216; and Land Design Engineer, Land Design, Inc., 233 North Graham St., Charlotte, North Carolina 28202 (E-Mail/Chang: chang@ohiou-edu).
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  • Timothy A. Bartrand,

    1. Respectively, Professor, Civil Engineering Department, Ohio University, 147 Stocker Center, Athens, Ohio 45701; Environmental Specialist, Ohio Environmental Protection Agency, 122 South Front Street, Columbus, Ohio 43216; and Land Design Engineer, Land Design, Inc., 233 North Graham St., Charlotte, North Carolina 28202 (E-Mail/Chang: chang@ohiou-edu).
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  • Richard Germain

    1. Respectively, Professor, Civil Engineering Department, Ohio University, 147 Stocker Center, Athens, Ohio 45701; Environmental Specialist, Ohio Environmental Protection Agency, 122 South Front Street, Columbus, Ohio 43216; and Land Design Engineer, Land Design, Inc., 233 North Graham St., Charlotte, North Carolina 28202 (E-Mail/Chang: chang@ohiou-edu).
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  • 1

    Paper No. 99149 of the Journal of the American Water Resources Association.Discussions are open until October 1, 2001.

Abstract

ABSTRACT: A regional water conservation system for drought management involves many uncertain factors. Water received from precipitation may stay on the ground surface, evaporate back into the atmosphere, or infiltrate into the ground. Reliable estimates of the amount of evapotranspiration and infiltration are not available for a large basin, especially during periods of drought. By applying a geographic information system, this study develops procedures to investigate spatial variations of unavailable water for given levels of drought severity. Levels of drought severity are defined by truncated values of monthly precipitation and daily streamflow to reflect levels of water availability. The greater the truncation level, the lower the precipitation or streamflow. Truncation levels of monthly precipitation are recorded in depth of water while those of daily streamflow are converted into monthly equivalent water depths. Truncation levels of precipitation and streamflow treated as regionalized variables are spatially interpolated by the unbiased minimum variance estimation. The interpolated results are vector values of precipitation and streamflow at a grid of points covering the studied basin. They are then converted into raster-based values and expressed graphically. The image subtraction operation is used to subtract the image of streamflow from that of precipitation at their corresponding level of drought severity. It is done on a cell-by-cell basis resulting in new attribute values to form the spatial image representing a spatial distribution of potential water loss at a given level of drought severity.

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