AN ABSTRACT OF THE THESIS OF VICTOR THOMAS NEAL for the Ph. D.in Oceanography (Name) (Degree) (Major) Date thesis is presentedlOAl4Wf 19kc TitleA CALCULATION OF FLUSHING TIMES AND POLLUTION DISTRIBUTION FOR THE COLUMBIA RIVER ESTUARY Redacted for Privacy Abstract approved (Major pr6fessor) The probable pollution distribution and flushing times have been calculated for the Columbia River Estuary,a coastal plain estuary. The pollution distribution was determined by the fresh water fraction and by the diffusion equation.The flushing times were calculated by the modified tidal prism method and by the fraction of freshwater, These methods are explained and discussed in the study. The widely varying river flow and resulting salt water intrusion were considered, as well as the varying semi-diurnal tidal range. These changing factors cause a complex variation in estuarine classi- fication from well-mixed to stratified. The data used was taken principally from the U. S. Corps of Engineers current measurement program of 1959.The data show a stronger flow on the north side of the estuary during flood tide anda stronger flow on the south side during ebb tide.Due to this fact, the estuary was also treated as two separate channels in calculating the pollution distribution. The results of the various calculations for combinations of con- ditions are given in this study. A comparison of the different me- thods is also summarized. The estuary has been found to have a relatively short flushing time, even under low river flow conditions.The variation in strength of flow from the north side to the south side has been shown to pro- duce pollution distributions not normally expected in an estuary. A CALCULATION OF FLUSHING TIMES AND POLLUTION DISTRIBUTION FOR THE COLUMBIA RIVER ESTUARY by VICTOR THOMAS NEAL A THESIS submitted to OREGON STATE UNIVERSITY in partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY June 1965 APPROVED: Redacted for Privacy In Charge of Major Redacted for Privacy Head of Departmentf Oceanography Redacted for Privacy Dean of Graduate School Date thesis is presented I 0 M4t.fI 9(o Typed by Opal Grossnicklaus ACKNOWLEDGMENTS The author wishes to express his deepest appreciation to Mrs. Susan Borden and Professor Uno R. Kodres for their help in setting up the computer programs used in part of this study. The author also wishes to thank Messrs. Ed Thornton, Merritt Stevenson, and Jackson Blanton who assisted in checking some of the planimetered values used in this study.The generosity and cooperation of the U. S. Corps of Engineers, Portland Dis- trict, in supplying data and permitting free use of their library facilities is also deeply appreciated. TABLE OF CONTENTS I.INTRODUCTION . The Problem and Definitions of Terms Used .. 1 Statement of Problem................ 1 Justification of the Study..................... 1 Definitions of Terms Used............. 3 Organization of the Thesis................. 5 II.REVIEW OF LITERATURE..................... 7 General............................. 7 Oregon Estuaries...................... 11 Classification of Estuaries................ 11 Geography of the Columbia River............ 16 The Columbia Estuary................... 23 Description...................... 23 Salinity Intrusion................... 25 Classification..................... 25 III.DATASOURCESANDANALYSIS................. 31 Sources............................. 31 Analysis............................32 IV. SOLUTION OF THE PROBLEM................. 37 Classical Tidal Prism Method.............. 37 Modified Tidal Prism Method..............38 Fraction of Fresh Water Method............43 Diffusion Equation Method................. 4 V. COMPUTATIONS........................... 50 Modified Tidal Prism Method.............. 50 Fraction of Fresh Water Method............. 52 Diffusion Equation Method................ 54 VI.DISCUSSIONOF RESULTS..................... 61 VII. SUMMARY AND CONCLUSIONS................. 67 BIBLIOGRAPHY...........................70 APPENDIX...............................75 LIST OF FIGURES 1 The Columbia Estuary 24 2 Isohalines near the mouth 27 3 Longitudinal salinity distribution during high tide and low river flow 29 4 Longitudinal salinity distribution during high tide and high river flow 30 5 Segmentation by the modified tidal prism method 40 6 A comparison of the calculated distribution of a conservative distribution of a conservative pollutant during high and low river flow.Outfall locations assumed at Ft. Stevens, Astoria, and Tongue Point 53 7 Distribution of pollutants predicted by the diffusion equation 58 8 Pollution distribution for the south channel as determined by the diffusion equation and the fresh water fraction 59 9 Pollution distribution for the north channel as determined by the diffusion equation and the fresh water fraction 60 10 A comparison of flushing times calculated by the modified tidal prism method and the fresh water fraction method 62 LIST OF TABLES TABLE PAGE 1 Classification of the Columbia River Estuary by vertical changes in average salinity 26 2 Local and cumulative lotide volumes and tidal prisms, expressed in 10 ft3, for each nautical mile segment, beginning at the mouth 33 3 Segmentation of the estuary by the modified tidal prism method (ocean salinity taken as 32. 0%, maximum salinity intrusion of 2. 0 nautical miles, and a tidal range of 8.0 feet) 51 4 Summary of results obtained by the modified tidal prism method for various combinations of river flow, salinity intrusion, tidal range, and ocean salinity 51 5 Flushing times calculated by the fraction of fresh water method 54 6 Conservative pollutant distribution, as determined by the diffusion equation (concentration, c, in lb/ft3 xl06 andn expressed in one-half nautical mile intervals from the mouth) 56 7 Calculated conservative pollution distribution in the Columbia Estuary by channels.River flow, R, in ft3/sec, concentration in 100 lb/ft3 (C is the concen- tration calculated by the fraction of fresh water me- thod), and the distance from the mouth, n, in nautical miles LIST OF SYMBOLS R volume rate of riverflow (cfs) v velocity of flow A cross-sectionalarea T ratio of cross-sectionalarea to wetted perimeter W wetted perimeter G surface slope Ah increment of verticaldistance L longitudinal distance M total pollution, as a multiple of pollutiondischarged into the estuaryper tidal cycle y proportion of waternot renewed eachtidal cycle (classical tidal prism method) Q volume river flowper tidal cycle P tidal prism V low tide volume r exchange ratio n segment number,expressed as distancefrom mouth m number of tidalcycles E accumulated volumeof river water z depth of estuary H depth of mixed layer LIST OF SYMBOLS (Continued) S salinity U total volume of given type of water f fresh water fraction rate of pollutant introduction C concentration of pollution by fresh water fraction method c concentration of pollution by the diffusion equation x distance along the longitudinal axis (x-axis) D turbulent eddy diffusivity F(x) net seaward flux of pollutant -r half-life of pollutant e increment of segment length along the x-axis R A D -An-1D n-1ADn n U - n-i+ n+l n+l 2a 2 2 a A nfl fl1 a2 R (A D -A D n+1 n+l n+l n-1 n-1)ADn n 2a 2 2 a A CALCULATION OF FLUSHING TIMES AND POLLUTION DISTRIBUTION FOR THE COLUMBIA RIVER ESTUARY I.INTRODUCTION The Problem and Definitions of Terms Used Statement of Problem The purposes of this study are to estimate the probable distri- bution of any pollutants that might be introduced into the Columbia River Estuary, and to estimate the flushing times for the estuary during different stages of river flow.More than one method has been used and the results are compared.Different conditions were chosen to give a broad range of possible results.Where a choice was suit- able, the worst conditions to be expected were used. Justification of the Study Estuaries are used by many groups of people.Some of the more important groups are the fishing industry, the military, the merchant fleet, recreation groups, manufacturers, and the municipalities lo- cated on the estuary.Any contamination of an estuary could have ad- verse effects on the activities of any one or several of the above groups. With n increasing population in our country, more andmore 2 demands will undoubtedly be made upon our estuaries both by industry, which needs water sources as well as waste disposal areas, and by the ensuing influx of people who also need water, recreational areas, food (supplied partly by the estuary in the form ofsea food), and waste disposal.Pollution that conceivably could result from these demands would very likely have an adverse effect upon thesea food and other marine populations normally found in the estuaries, and might make them unfit for human use, as well. In our modern age we need to consider the effects of possible contamination such as would develop if a nuclear catastrophe were to occur either in the estuary itself or upstream in the tributary nv- er.The military as well as civilian populations would be concerned and vitally affected. A thorough search of the literature revealed no studiescon- cerning the flushing times and probable pollution distribution in the Columbia Estuary, although considerable concern has been expressed regarding the increase of certain types of pollutants (Osterberg, Pattullo, and Pearcy, 1964; U. S. Public Health Service, Oregon State Sanitary Authority, and Washington Pollution Control Commis- sion, 1958).The pollution of this estuary has not yet been considered