HR: 0800h
AN: H51D-1186    [Abstracts]
TI: Using Residence-Time Distributions to Compare Water-Level Hydrographs
AU: * Walker, J F
EM: jfwalker@usgs.gov
AF: U.S. Geological Survey, 8505 Research Way, Middleton, WI 53562 United States
AU: Hunt, R J
EM: rjhunt@usgs.gov
AF: U.S. Geological Survey, 8505 Research Way, Middleton, WI 53562 United States
AB: The availability of accurate, high-frequency water-level data has greatly improved the potential for site-specific hydrologic assessments. Traditional comparisons between sites included summary statistics (mean/median water level) and qualitative assessments of hydrographs. In many instances traditional summary statistics are not adequate to convey the importance of water-level fluctuation or the amount of time water levels are at or above a critical level. For instance, plant growth in wetlands depends on water levels reaching the root zone and sustaining inundation for adequate periods during the growing season. In this paper we present a method of analyzing continuous high-frequency water-level data to determine the distribution of residence time for a specific water level. Typically the root-zone elevation is used as the specific water level, resulting in the distribution of root-zone residence times. We compare this approach to traditional methods at a range of hydrological settings in Wisconsin. In addition to the information contained in the graphical display of the distribution functions, pairs of sites can be compared by examining the duration for specific probabilities. Using the Smirnov test it is possible to determine whether there are statistically significant differences between the distributions for two sites. This insight helps describe hydrologic conditions that drive biological responses--a relation difficult to explain using simple summary statistics derived from water-level measurements.
DE: 1829 Groundwater hydrology
DE: 1851 Plant ecology
DE: 1866 Soil moisture
DE: 1890 Wetlands
SC: Hydrology [H]
MN: 2004 AGU Fall Meeting