Abstract:

A proper water allocation system for drought management involves many uncertainties. One of the least certain elements is the amount of evaporation and infiltration during time periods of drought. To date, there is no means for reliable estimation of those parameters for large basins. By applying a geographic information system this study demonstrated a procedure for forming an evaporation and infiltration image and illustrating water unavailability during periods of drought for a selected basin. Gaging stations of precipitation and streamflow in the studied basin were selected to spatially represent the area. Based on the method of truncation levels, 70 and 90% truncation levels were estimated for each gaging station. A 70% truncation level means that 70% of the historic records at the gage station were greater than the truncation value. Hence, the greater the truncation, the lower the availability of precipitation or streamflow. In this study, precipitation was recorded as depth of water and streamflow was expressed as equivalent water depth. Since hydrologic records were taken at gaging stations, truncation levels of precipitation and streamflow were location-dependent variables. Assuming the truncation levels at all gaging stations are regionalized variables, the kriging method was employed to estimate their regional distribution. Kriging is a spatial interpolation technique based on minimum variance unbiased estimation. The Kriging analysis of these truncation levels yielded vector values of precipitation and streamflow for a grid covering the entire drainage basin of interest. Point values for precipitation and streamflow were converted to a raster format and expressed as a spatial images. The streamflow image was then subtracted from the precipitation for each truncation level. The resulting images illustrate the unavailability of water throughout a basin at 70% and 90% truncation levels.

1. Professor, Civil Engineering Department, Ohio University, Athens, OH 45701.

2. Former Graduate Assistant, Civil Engineering Department, Ohio University, Athens, OH 45701.

3. Graduate Assistant, Civil Engineering Department, Ohio University, Athens, OH 45701.

For more information on this or any other paper contact Terry Chang by email at tjchang@bobcat.ent.ohiou.edu

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