9431

• UCREFRP Catalog Number: 9431
• Author: Chafin, D. T.
• Title: Evaluation of Trends in pH in the Yampa River, Northwestern Colorado, 1950-2000.
• USFW Year: 2002.
• USFW - Doc Type: Denver.
• Copyright Material: NO

CONTENTS
Abstract ..................................................................................................................................................................................
1
Introduction ............................................................................................................................................................................
2
Purpose and Scope ....................................................................................................................................................... 4
Description of Study Area ........................................................................................................................................... 4
Sample Collection and Measurements ......................................................................................................................... 5
Acknowledgments ....................................................................................................................................................... 6
Interpretation of Data Collected for this Study ...................................................................................................................... 6
Summer 1999 ............................................................................................................................................................... 7
Synoptic Sampling ............................................................................................................................................. 7
Diurnal Measurements .........................................:............................................................................................. 12
Reconnaissance Measurements in Dinosaur National Monument .................................................................... 16
Winter 2000 Synoptic Sampling .................................................................................................................................. 18
Estimate of Maximum Potential Late-Afternoon pH in the Lower Yampa River Basin ............................................. 20
Interpretation of Historical Data from Yampa River near Maybell ....................................................................................... 25
Trends in Dissolved Solids and Major Ions ................................................................................................................. 26
Trends in Thermodynamic Properties .............................:............................................................................................ 29
Causes of Historical Increase in Measured pH at Yampa River near Maybell ...................................................................... 32
Summary ................................................................................................................................................................................
35
References Cited ....................................................................................................................................................................
37
Supplemental Information ..................................................................................................................................................... 39
FIGURES
1. Map showing study area and water-quality-sampling sites ....................................................................................... 3
2-25. Graphs showing:
2. Temporal distribution of measured pH values at Yampa River near Maybell ................................................... 4
3. Specific conductance at Yampa River and tributary sites, August 16-19, 1999 ............................................... 8
4. Concentrations of calcium and alkalinity at Yampa River and main tributary sites, August 16-19, 1999....... 9
5. pH and other geochemical indicators at Yampa River and tributary sites, August 16-19, 1999 ...................... 10
6. Measured and simulated pH at Yampa River sites, August 16-19, 1999 .......................................................... 12
7. Diurnal measurements at Yampa River above Elk River, August 23-24, 1999 ................................................ 13
8. Diurnal measurements at Yampa River below Craig, August 23-24, 1999 ...................................................... 13
9. Diurnal measurements at Yampa River near Maybell, August 23-24, 1999 .................................................... 15
10. Diurnal measurements at Yampa River at Deerlodge Park, August 25-26, 1999 ............................................. 15
11. Diurnal measurements at Yampa River at mouth, August 25-26, 1999 ........................................................... 16
12. Reconnaissance measurements on Yampa River in Dinosaur National Monument, August 30-
September 3, 1999 ............................................................................................................................................. 17
13. Specific conductance at Yampa River and tributary sites, March 13-16, 2000 ................................................ 19
14. pH and other geochemical indicators at Yampa River and tributary sites, March 13-16, 2000 ....................... 21
15. Measured and simulated pH at Yampa River sites, March 13-16, 2000 ........................................................... 22
16. Simulated maximum potential pH for water-quality sites in the lower Yampa River Basin,
August 16-19, 1999, and March 13-16, 2000 .................................................................................................. 23
17. Simulated maximum potential pH for water sample collected at the Yampa River at Deerlodge Park on
August 18, 1999, at varying salinities ............................................................................................................... 24
18. Temporal distribution of measured pH and dissolved solids at Yampa River near Maybell, 1950-99 ............. 27
19. Temporal distribution of concentrations of major cations at Yampa River near Maybell, 1950-99 ................. 28
20. Temporal distribution of concentrations of major anions at Yampa River near Maybell, 1950-99 .................. 29
21. Temporal distribution of dissolved carbon dioxide saturation factor at Yampa River near Maybell,
1950-99 ............................................................................................................................................................. 30
22. Relation between measured pH and dissolved carbon dioxide saturation factor at Yampa River near
Maybell, 1950-99 .............................................................................................................................................. 30
CONTENTS iii