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WWRC 88-17
Techniques for Augmenting Water Quality Data: Application to Flaming Gorge Reservoir and to Sampling Protocols

Organization of the Report

Section 1

Introduction

In this section we briefly comment on the geology, climate, soils, land cover and hydrology of the Green River watershed. This is followed by a description of Flaming Gorge and a discussion of how the process of eutrophication differs in lakes and reservoirs.

Section 2

Predicting export of water quality parameters from the
Green River basin to Flaming Gorge Reservoir;
Multiple regression using basin characteristics

Here we develop multiple regression models describing the export of total phosphorus (TP), nitrate-nitrogen (NO3), total dissolved solids (TDS), total alkalinity, and turbidity (JTU) as functions of basin attributes. Models are verified both by a sequential split-plot analysis and by application to an adjacent but separate drainage. The models are developed from an initial set of over sixty independent variables, or basin attributes. Because data on water quality are sparse, the analyses are based on only sixteen stations or subbasins.

Section 3

Use of Data Augmentation Techniques and Time Series Analysis for
Estimating Loading to Flaming Gorge Reservoir

Infrequent and intermittent sampling may have biased results of the multiple regressions in Section 2, so we next develop an augmented data set for the Green River basin daily loads of TP and TDS for the years 1965-1979. And, by resampling these daily data, we determine the mean annual load and yearly loads of TP based upon three different sampling intervals and two sampling strategies. Then we derive an optimum scheme for sampling TP and TDS.

Secondly, we explore temporal features of phosphorus loads in the augmented data set. Time series models are developed and analyzed for phosphorus loading. For example we identify years with loading significantly different from each other, and different from the mean annual load, and we indicate which estimates of loading we judge to be the best.

Section 4

Potential effects of loading on eutrophication in
Flaming Gorge Reservoir;
Analysis with a Vollenweider model

We begin this section by describing the derivation and assumptions of Vollenweider models, which relate phosphorus loading to the trophic state of lakes. Then we use all our loading estimates to evaluate whether excessive loading is predicted to occur for Flaming Gorge reservoir, and whether elimination of point source input might alter the trophic status. Unfortunately, we cannot associate an estimate of uncertainty with our analyses.

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