A Buffered Advection/Dispersion Lake Water Quality Transport Framework for Modeling Lake Gaston Pipeline Intake Water Withdrawal

Date of Award

Spring 2000

Document Type


Degree Name

Master of Science (MS)


Civil & Environmental Engineering


Environmental Engineering

Committee Director

Jaewan Yoon

Committee Member

A. Osman Akan

Committee Member

Mujde Erten-Unal

Call Number for Print

Special Collections LD4331.E553 G38


Water quality response to reservoir water withdrawal is investigated in Pea Hill Arm of Lake Gaston, a non-tidal reservoir tributary, where the point of water withdrawal is in an upstream tributary and influences the direction of tributary flow causing longitudinal velocity null flow conditions to occur. The study also focuses on control of withdrawal rate and timing to optimize both quality of water remaining in the tributary and quantity of water that can be safely withdrawn.

Research was conducted assuming steady state conditions and later under spatial and temporal variability experienced in the reservoir with main lake pool elevation fluctuations at the tributary boundary resulting from hydroelectric power plant operation and other main lake influences.

A steady state source-sink water quality model was first developed to predict tributary flow and total suspended solids (TSS) pollutant transport. The source model used the USEP A SWMM model to determine runoff components from drainage areas that were combined with tributary base flow and direct rainfall. Source components were then used as headwater and incremental flow in the USEPA QUAL2EU sink model to predict tributary flow and TSS concentrations. Dry weather and wet weather model runs using historical rainfall data collected by NOAA were then conducted.

From comparison of model run data with historical data, it was concluded that TSS at the intake reduced at the 60-cfs intake rate by rejecting the null hypothesis HO: μTss(priori) = μTss(posterior) at a=0.05. Field data showed increased Secchi depth of 1.9 meters that correlated with this conclusion. The study also indicated intake rates between 18 cfs and 23 cfs would result in a TSS peak concentration of 31.9 mg/L between the intake and main lake due to reduced longitudinal velocities as they approach a velocity null condition.

Dynamic changes in tributary flow and TSS concentration were found to be buffered by mixing with tributary storage leading to conceptualization of a dynamic flow model developed from the Saint Venant equations and a water quality model conceptualized using advection-dispersion equations. Finally, intake flow rates that optimize both water quality and intake quantity were developed and are proposed for use to optimize tributary water quality.


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