Date of Award
Fall 2006
Document Type
Dissertation - Restricted
Degree Name
Doctor of Philosophy (PhD)
Department
Civil, Construction, and Environmental Engineering
First Advisor
Melching, Charles S.
Second Advisor
Crandall, Clifford J.
Third Advisor
Novotny, Vladimir
Abstract
Wet weather impacts arising from urban catchments are widely recognized as a major cause of unsatisfactory receiving water quality and violation of the water quality standards. In the U.S., water quality standards define water quality goals that are related to the designated use of the water body. If the water body has been classified as partially supporting or not supporting the designated use, the states or designated agencies perform an Use Attainability Analysis (UAA) to determine the proper use of the water body and the water quality conditions needed to achieve this use. An UAA determines what levels of water quality can possibly be attained by implementation of various feasible point and nonpoint source control abatement measures and other measures (i.e. in-stream aeration, low-flow augmentation, etc). An UAA requires a strong scientific background to accomplish its tasks. This study contributes to future UAA studies aiding the accurate identification of water quality problems and the effectiveness of management alternatives to achieve designated uses by developing a methodology to determine the duration of storm effects, i.e. wet weather conditions, on water quality. The methodology to determine the duration of storm effects on water quality involves mainly two steps. First, calibration of an appropriate water quality model that is capable of simulation of unsteady-state conditions. Second, execution of the calibrated model with a number of storm loadings randomly sampled from a specific probability distribution that represents realistic ranges of pollutant concentrations. Several sampling methods are available and Latin Hypercube Sampling is the most appropriate sampling method because it can provide satisfactory results with a reasonable computational time (i.e. small sample) for complex unsteady-state models. The purpose is to observe the variations in the simulated water quality constituents to determine the duration of the wet weather condition for a given storm. It is proposed that when the variations in the simulated water quality parameters become negligible, the river system goes back to prestorm, dry-weather conditions. It is important to develop a general approach to predict the duration of storm effects on water quality. Precipitation (which was not used in the calibration of water quality model) was correlated with the duration of storm effects on water quality and the relation obtained between the magnitude of precipitation and the duration of the storm effect on in-stream water quality can be easily applied to other storms. Similar relations could be developed in other studies.