Date of Award:


Document Type:


Degree Name:

Doctor of Philosophy (PhD)


Civil and Environmental Engineering


J. Paul Riley


The development of a model capable of predicting the long term (seasonal) distribution of water quality constituents within Great Salt Lake was undertaken as a portion of the ongoing Great Salt Lake project at Utah State University. The overall goal of the project is the development of a modeling framework to assist the relevant decision making bodies in the comprehensive management of the Great Salt Lake system. Phase I of the project provided the overall structural framework for management of the Great Salt Lake system, identified data needs, and established priorities for the development of submodels for incorporation into the overall framework. Phase II of the project involves the process of developing submodels, and Phase III will be concerned with application of the framework of models to specific management problems.

This study provides, as part of the second phase of the Great Salt Lake project, a model capable of predicting the long term distribution of quality constituents within the lake. This capability is a necessary component of the modeling framework since it will allow the investigation of the effects which alternative water quality management plans will have on the distribution of water quality constituents within the lake.

The water quality model of the lake is based on the application of the advection-diffusion equation to the three-dimensional transport of a quality constituent. The modeling technique is formulated by discretizing the system as a network of nodes interconnected by channels in both the horizontal and vertical directions. This representation of the system allowed the horizontal transport to be treated mathematically as one-dimensional. The resulting modeling technique is applicable to any lake, estuary, or bay in which the concentration gradients must be described in all three coordinate directions.

In applying the model to Great Salt Lake a two-layered vertical network was employed due t o the physical characteristics of the system. The model was further simplified by describing vertical transport by diffusion alone. Using observed total dissolved solids concentrations, a method was developed during the study for establishing the vertical diffusion coefficient as a function of depth.

A unique feature of this water quality modeling technique is that it allows the seasonal distribution of a quality constituent to be studied without the necessity of developing a hydrodynamic model of the system . The advective transport is designed to be input to the model based on observed long term circulation patterns . In the case of Great Salt Lake, circulation patterns are not yet well known. However, approximate patterns h a ,, e been established from some observations to date , and those were used to provide preliminary tests of the validity and response characteristics of the model. These tests have demonstrated that the model will be a practical and useful tool for monitoring the distribution of quality constituents within the lake.