Geometrically incremental volume sampling for ephemeral channel pollutants
1996
Tremwel, T.K. | Campbell, K.L. | Miller, L.W.
Storage-based upland hydrology complicates the measurement of surface water contaminant parameters on Florida's flatwoods soils. Ephemeral streams and ditches may seldom contain any flow, but may suddenly fill with flow that persists for days or weeks. If the first-flush effect is to be studied, sampling programs must sample frequently on the quick rising limb of a runoff event, while conserving sampler bottles for the slow falling limb. A datalogger-controlled sampling technique which uses a geometrically increasing runoff volume relationship was developed to sample both small and large natural events adequately and automatically. Hydrographs of actual field data are used to illustrate the performance of the technique during one large and one small event. Comparisons to standard flow proportional sampling techniques are included. The new technique provides adequate sampling for about a 100-fold range of runoff volumes, allowing accurate calibration and verification of field-scale water quality models. Nutrient data is superimposed onto hydrographs to show the trends revealed using the technique. The principal advantage of the technique is that it is less labor and resource intensive than traditional methods and yet it gives a more accurate determination of pollutant loading in ephemeral ditches and streams. The increased level of accuracy could allow the determination of dominant physical processes present in contaminant solubilization or detachment and transport during natural storms of various sizes.
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