U.S. Department of the Interior

U.S. Geological Survey

Scientific Investigations Report 2013–5119

Prepared in cooperation with the Bureau of Reclamation

Simulated Effects of Proposed Arkansas Valley Conduit 

on Hydrodynamics and Water Quality for Projected Demands 

through 2070, Pueblo Reservoir, Southeastern Colorado
Cover: Pueblo Reservoir looking southwest towards Round Top Mountain, August 2008.

Photograph by R.F. Ortiz, U.S. Geological Survey.
Simulated Effects of Proposed Arkansas 

Valley Conduit on Hydrodynamics and 

Water Quality for Projected Demands 

through 2070, Pueblo Reservoir, 

Southeastern Colorado

By Roderick F. Ortiz

Prepared in cooperation with the Bureau of Reclamation

Scientific Investigations Report 2013–5119

U.S. Department of the Interior

U.S. Geological Survey
U.S. Department of the Interior

SALLY JEWELL, Secretary

U.S. Geological Survey

Suzette M. Kimball, Acting Director

U.S. Geological Survey, Reston, Virginia: 2013

For more information on the USGS—the Federal source for science about the Earth, its natural and living 

resources, natural hazards, and the environment, visit http://www.usgs.gov or call 1–888–ASK–USGS.

For an overview of USGS information products, including maps, imagery, and publications, 

visit http://www.usgs.gov/pubprod

To order this and other USGS information products, visit http://store.usgs.gov

Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the 

U.S. Government.

Although this information product, for the most part, is in the public domain, it also may contain copyrighted materials 

as noted in the text. Permission to reproduce copyrighted items must be secured from the copyright owner.

Suggested citation:

Ortiz, R.F., 2013, Simulated effects of proposed Arkansas Valley Conduit on hydrodynamics and water quality

for projected demands through 2070, Pueblo Reservoir, southeastern Colorado: U.S. Geological Survey Scientific 

Investigations Report 2013–5119, 49 p., http://pubs.usgs.gov/sir/2013/5119/.
iii

Contents

Abstract...........................................................................................................................................................1

Introduction.....................................................................................................................................................1

Purpose and Scope ..............................................................................................................................2

Methods of Hydrodynamic and Water-Quality Simulation .....................................................................4

Reservoir Modeling Using CE-QUAL-W2..........................................................................................4

Streamflow and Water-Quality Modeling for Projected Demands in 2070 .................................6

Description of Simulation Scenarios..........................................................................................................6

No Action Scenario ..............................................................................................................................7

Comanche South Scenario .................................................................................................................7

Joint Use Pipeline North Scenario ....................................................................................................7

Master Contract Only Scenario..........................................................................................................7

Existing Conditions Scenario ..............................................................................................................7

General Comparisons Between All Simulation Scenarios .....................................................................7

Comparison of Results for Selected Simulation Scenarios....................................................................9

Comparison of Existing Conditions Scenario and No Action Scenario .....................................11

Water-Surface Elevations ........................................................................................................15

Water Temperature ...................................................................................................................15

Dissolved Oxygen.......................................................................................................................15

Dissolved Solids.........................................................................................................................16

Major Nutrients..........................................................................................................................17

Dissolved Ammonia..........................................................................................................17

Dissolved Nitrate ..............................................................................................................19

Total Phosphorus ..............................................................................................................19

Total Iron......................................................................................................................................19

Algal Groups and Chlorophyll-a ..............................................................................................20

Comparison of No Action Scenario and Other Simulation Scenarios .......................................24

Water-Surface Elevations ........................................................................................................24

Water Temperature ...................................................................................................................25

Dissolved Oxygen.......................................................................................................................25

Dissolved Solids.........................................................................................................................26

Major Nutrients..........................................................................................................................29

Dissolved Ammonia..........................................................................................................29

Dissolved Nitrate ..............................................................................................................29

Total Phosphorus ..............................................................................................................34

Total Iron......................................................................................................................................34

Algal Groups and Chlorophyll-a ..............................................................................................35

Summary and Conclusions.........................................................................................................................37

References Cited..........................................................................................................................................40

Appendixes ...................................................................................................................................................43
iv

Figures

1. Map showing location of the study area ..................................................................................3

2. Map showing location of selected sites on the Arkansas River and 

Pueblo Reservoir...........................................................................................................................5

3–9. Graphs showing:

 3. Comparison of water-surface elevations in Pueblo Reservoir for the 

Existing Conditions scenario (water years 2000 through 2002) and 

cumulative- and direct-effects analyses for selected simulation scenarios..............8

 4. Simulated water temperature profiles for Pueblo Reservoir, Colorado, 

at site 7B, April 2001 through January 2002 ....................................................................10

 5. Comparison of water temperatures in the epilimnion at site 7B in Pueblo 

Reservoir for the Existing Conditions scenario (water years 2000 through 

2002) and cumulative- and direct-analyses for selected simulation scenarios .......11

 6. Simulated dissolved oxygen profiles for Pueblo Reservoir, Colorado, at 

site 7B, April 2001 through January 2002.........................................................................12

 7. Comparison of dissolved oxygen concentrations at site 7B in Pueblo Reservoir 

for the Existing Conditions scenario (water years 2000 through 2002) and 

cumulative- and direct-effects analyses for selected simulation scenarios.................... 13

 8. Comparison of (A) dissolved solids and (B) dissolved ammonia concentrations

at site 7B in Pueblo Reservoir for the Existing Conditions scenario (water 

years 2000 through 2002) and cumulative- and direct-effects analyses for 

selected simulation scenarios................................................................................................14

 9. Comparison of water-surface elevations in Pueblo Reservoir for the Existing

Conditions (water years 2000 through 2002) and No Action scenarios......................15

10–16. Boxplots showing:

 10. Annual median water temperature in the epilimnion and hypolimnion at 

site 7B for the Existing Conditions (water years 2000 through 2002) and 

No Action (direct-effects analysis) scenarios................................................................16

 11. Annual median dissolved oxygen concentrations in the epilimnion and 

hypolimnion at site 7B for the Existing Conditions (water years 2000 

through 2002) and No Action (direct-effects analysis) scenarios...............................17

 12. Annual median dissolved solids concentrations in the epilimnion and 

hypolimnion at site 7B for the Existing Conditions (water years 2000 

through 2002) and No Action (direct-effects analysis) scenarios...............................19

 13. Annual median dissolved ammonia concentrations in the epilimnion 

and hypolimnion at site 7B for the Existing Conditions (water years 2000 

through 2002) and No Action (direct-effects analysis) scenarios...............................19

 14. Annual median dissolved nitrate concentrations in the epilimnion and 

hypolimnion at site 7B for the Existing Conditions (water years 2000 

through 2002) and No Action (direct-effects analysis) scenarios...............................20

 15. Annual median total phosphorus concentrations in the epilimnion and 

hypolimnion at site 7B for the Existing Conditions (water years 2000 

through 2002) and No Action (direct-effects analysis) scenarios...............................20

 16. Annual median total iron concentrations in the epilimnion and 

hypolimnion at site 7B for the Existing Conditions (water years 2000 

through 2002) and No Action (direct-effects analysis) scenarios...............................20
v

17–19. Graphs showing:

 17. Comparison of total iron concenrations in the hypolimnion at site 7B in 

Pueblo Reservoir for the Existing Conditions (water years 2000 through 

2002) and No Action (direct-effects analysis) scenarios..............................................21

 18. Relation between various algal groups in the epilimnion and hypolimnion 

at site 7B for the Existing Conditions (water years 2000 through 2002) and 

No Action (direct-effects analysis) scenarios................................................................22

 19. Relation between various algal groups in the epilimnion and hypolimnion 

at site 3B for the Existing Conditions (water years 2000 through 2002) and 

No Action (direct-effects analysis) scenarios................................................................23

20. Boxplot showing annual median chlorophyll-a concentrations in the epilimnion 

and hypolimnion at site 7B for the Existing Conditions (water years 2000 through 

2002) and No Action (direct-effects analysis) scenarios.....................................................24

21. Graph showing comparison of water-surface elevations in Pueblo Reservoir 

for the No Action, Comanche South, Joint Use Pipeline North, and Master 

Contract Only scenarios (direct-effects analyses)...............................................................25

22–28. Boxplots showing:

 22. Annual median water temperature in the epilimnion and hypolimnion 

at site 7B for the No Action, Comanche South, Joint Use Pipeline North, 

and Master Contract Only scenarios (direct-effects analyses)..................................26

 23. Annual median dissolved oxygen concentrations in the epilimnion and 

hypolimnion at site 7B for the No Action, Comanche South, Joint Use 

Pipeline North, and Master Contract Only scenarios (direct-effects 

analyses)...............................................................................................................................29

 24. Annual median dissolved solids concentrations in the epilimnion and

hypolimnion at site 7B for the No Action, Comanche South, Joint Use 

Pipeline North, and Master Contract Only scenarios (direct-effects analyses).............. 32

 25. Annual median dissolved ammonia concentrations in the epilimnion and

hypolimnion at site 7B for the No Action, Comanche South, Joint Use 

Pipeline North, and Master Contract Only scenarios (direct-effects analyses).............. 32

 26. Annual median dissolved nitrate concentrations in the epilimnion and 

hypolimnion at site 7B for the No Action, Comanche South, Joint Use 

Pipeline North, and Master Contract Only scenarios (direct-effects analyses).............. 33

 27. Annual median total phosphorus concentrations in the epilimnion and 

hypolimnion at site 7B for the No Action, Comanche South, Joint Use 

Pipeline North, and Master Contract Only scenarios (direct-effects analyses).............. 34

 28. Annual median total iron concentrations in the epilimnion and hypolimnion 

at site 7B for the No Action, Comanche South, Joint Use Pipeline North, and 

Master Contract Only scenarios (direct-effects analyses)..........................................34

29. Graph showing comparison of total iron concentrations in the hypolimnion 

at site 7B in Pueblo Reservoir for the No Action, Comanche South, Joint Use 

Pipeline North, and Master Contract Only scenarios (direct-effects analyses)..............35

30. showing relation between various algal groups in the epilimnion 

at sites 7B and 3B for the No Action, Comanche South, Joint Use Pipeline 

North, and Master Contract Only scenarios (direct-effects analyses).............................36

31. Boxplots showing annual median chlorophyll–a concentrations in the epilimnion 

and hypolimnion at site 7B for the No Action, Comanche South, Joint Use 

Pipeline North, and Master Contract Only scenarios (direct-effects analyses)..............37
vi

Tables

1. Comparison of Environmental Impact Statement alternatives associated with 

the proposed Arkansas Valley Conduit and identification of four alternatives 

selected for scenario simulation................................................................................................4

2. Percent change between annual median values for selected constituents in 

the epilimnion and hypolimnion at site 7B for the Existing Conditions scenario 

(water years 2000 through 2002) as compared to the No Action (direct-effects 

analysis) scenario.......................................................................................................................16

3. Percent change between annual median values for selected constituents in 

the epilimnion and hypolimnion at site 3B for the Existing Conditions scenario 

(water years 2000 through 2002) as compared to the No Action (direct-effects 

analysis) scenario.......................................................................................................................17

4. Percent change between annual 85th percentile values for selected constituents 

and the annual 15th percentile values for dissolved oxygen concentrations in 

the epilimnion and hypolimnion at site 7B for the Existing Conditions scenario 

(water years 2000 through 2002) as compared to the No Action (direct-effects 

analysis) scenario.......................................................................................................................18

5. Percent change between annual 85th percentile values for selected constituents 

and the annual 15th percentile values for dissolved oxygen concentrations in 

the epilimnion and hypolimnion at site 3B for the Existing Conditions scenario 

(water years 2000 through 2002) as compared to the No Action (direct-effects 

analysis) scenario.......................................................................................................................18

6. Percent change between annual median values for selected constituents in 

the epilimnion and hypolimnion at site 7B for direct-effects analyses for the 

Comanche South, Joint-Use Pipeline North, and Master Contract Only scenarios 

as compared to the No Action scenario.................................................................................27

7. Percent change between annual median values for selected constituents in 

the epilimnion and hypolimnion at site 3B for direct-effects analyses for the 

Comanche South, Joint Use Pipeline North, and Master Contract Only scenarios 

as compared to the No Action scenario.................................................................................28

8. Percent change between annual 85th percentile values for selected constituents 

and comparisons of the annual 15th percentile values for dissolved oxygen 

concentrations in the epilimnion and hypolimnion at site 7B for direct-effects 

analyses for the Comanche South, Joint Use Pipeline North, and Master Contract 

Only scenarios as compared to the No Action scenario.....................................................30

9. Percent change between annual 85th percentile values for selected constituents 

and comparisons of the annual 15th percentile values for dissolved oxygen 

concentrations in the epilimnion and hypolimnion at site 3B for direct-effects 

analyses for the Comanche South, Joint Use Pipeline North, and Master Contract 

Only scenarios as compared to the No Action scenario.....................................................31
vii

Appendix Tables

1. Percent change between annual median values for selected constituents 

in the epilimnion and hypolimnion at site 7B for the Existing Conditions scenario 

(water years 2000 through 2002) as compared to the No Action (cumulativeeffects analysis) scenario .........................................................................................................43

2. Percent change between annual median values for selected constituents in 

the epilimnion and hypolimnion at site 3B for the Existing Conditions scenario 

(water years 2000 through 2002) as compared to the No Action (cumulativeeffects analysis) scenario .........................................................................................................43

3. Percent change between annual 85th percentile values for selected constituents 

and the annual 15th percentile values for dissolved oxygen concentrations in the 

epilimnion and hypolimnion at site 7B for the Existing Conditions scenario (water 

years 2000 through 2002) as compared to the No Action (cumulative-effects 

analysis) scenario.......................................................................................................................44

4. Percent change between annual 85th percentile values for selected constituents 

and the annual 15th percentile values for dissolved oxygen concentrations in the

epilimnion and hypolimnion at site 3B for the Existing Conditions scenario (water 

years 2000 through 2002) as compared to the No Action (cumulative-effects 

analysis) scenario.......................................................................................................................44

5. Percent change between annual median values for selected constituents in the 

epilimnion and hypolimnion at site 7B for cumulative-effects analyses for the 

Comanche South, Joint Use Pipeline North, and Master Contract Only scenarios 

as compared to the No Action scenario.................................................................................45

6. Percent change between annual median values for selected constituents in 

the epilimnion and hypolimnion at site 3B for cumulative-effects analyses for 

the Comanche South, Joint Use Pipeline North, and Master Contract Only 

scenarios as compared to the No Action scenario..............................................................46

7. Percent change between annual 85th percentile values for selected constituents 

and comparisons of the annual 15th percentile values for dissolved oxygen 

concentrations in the epilimnion and hypolimnion at site 7B for cumulative-effects

analyses for the Comanche South, Joint Use Pipeline North, and Master Contract 

Only scenarios as compared to the No Action scenario.....................................................47

8. Percent change between annual 85th percentile values for selected constituents 

and comparisons of the annual 15th percentile values for dissolved oxygen 

concentrations in the epilimnion and hypolimnion at site 3B for cumulative-effects 

analyses for the Comanche South, Joint Use Pipeline North, and Master Contract 

Only scenarios as compared to the No Action scenario. ....................................................48
viii

Conversion Factors and Datums

Inch/Pound to SI

Multiply By To obtain

inch 2.54 centimeter

foot 0.3048 meter

mile 1.609 kilometer

acre-foot 1,233 cubic meter

foot per second 0.3048 meter per second

cubic foot per second 0.02832 cubic meter per second

gallons per day 0.00378 cubic meter per day

Temperature in degrees Celsius (°C) may be converted to degrees Fahrenheit (°F) as follows:

°F=(1.8×°C)+32

Temperature in degrees Fahrenheit (°F) may be converted to degrees Celsius (°C) as follows:

°C=(°F–32)/1.8

Vertical coordinate information is referenced to the North American Vertical Datum of 1988 

(NAVD 88).

Horizontal coordinate information is referenced to the North American Datum of 1983 (NAD 83).

Elevation, as used in this report, refers to distance above the vertical datum.

Concentrations of chemical constituents in water are given either in milligrams per liter (mg/L) 

or micrograms per liter (μg/L).

Water Year (WY) is defined as beginning October 1 and continuing through September 30 of the 

following year.

Abbreviations and acronyms used in this report:

AVC Arkansas Valley Conduit

Daily Model Arkansas River Daily Simulation Model

DO dissolved oxygen

DS dissolved solids

EIS Environmental Impact Statement

GIS Geographical Information System

NEPA National Environmental Policy Act

Project Fryingpan-Arkansas Project

Reclamation Bureau of Reclamation

SECWCD Southeastern Colorado Water Conservancy District

USGS U.S. Geological Survey

WY Water Year
Simulated Effects of Proposed Arkansas Valley Conduit 

on Hydrodynamics and Water Quality for Projected Demands 

through 2070, Pueblo Reservoir, Southeastern Colorado

By Roderick F. Ortiz

indirect- and cumulative-effects analyses indicated that, in 

general, the results were similar for most of the scenarios and 

comparisons in this report focused on results from the direct/

indirect-effects analyses.

Scenario simulations that represented existing 

conditions in Pueblo Reservoir were compared to the No 

Action scenario to assess changes in water quality from 

current demands (2006) to projected demands in 2070. 

Overall, comparisons of the results between the Existing 

Conditions and the No Action scenarios for water-surface 

elevations, water temperature, and dissolved oxygen, dissolved 

solids, dissolved ammonia, dissolved nitrate, total phosphorus, 

and total iron concentrations indicated that the annual median 

values generally were similar for all three simulated years. 

Additionally, algal groups and chlorophyll-a concentrations 

(algal biomass) were similar for the Existing Conditions and 

the No Action scenarios at site 7B in the epilimnion for the 

simulated period (Water Year 2000 through 2002).

The No Action scenario also was compared individually 

to the Comanche South, Joint Use Pipeline North, and Master 

Contract Only scenarios. These comparisons were made to 

describe changes in the annual median, 85th percentile, or 

15th percentile concentration between the No Action scenario 

and each of the other three simulation scenarios. Simulated 

water-surface elevations, water temperature, dissolved oxygen, 

dissolved solids, dissolved ammonia, dissolved nitrate, 

total phosphorus, total iron, algal groups, and chlorophyll-a

concentrations in Pueblo Reservoir generally were similar 

between the No Action scenario and each of the other three 

simulation scenarios.

Introduction

The Fryingpan-Arkansas Project (Project) is a multipurpose transmountain, transbasin water diversion and 

delivery project in Colorado. Authorized for construction in 

1962 under Public Law 87-590 (77 Stat. 393), the Project 

annually diverts an average of 69,200 acre-feet of surplus 

water from the western slope of the Rocky Mountains to 

the Arkansas River Basin on the eastern slope (Bureau of 

Abstract

The purpose of the Arkansas Valley Conduit (AVC) is 

to deliver water for municipal and industrial use within the 

boundaries of the Southeastern Colorado Water Conservancy 

District. Water supplied through the AVC would serve two 

needs: (1) to supplement or replace existing poor-quality 

water to communities downstream from Pueblo Reservoir; 

and (2) to meet a portion of the AVC participants’ projected 

water demands through 2070. The Bureau of Reclamation 

(Reclamation) initiated an Environmental Impact Statement 

(EIS) to address the potential environmental consequences 

associated with constructing and operating the proposed 

AVC, entering into a conveyance contract for the Pueblo 

Dam north-south outlet works interconnect (Interconnect), 

and entering into a long-term excess capacity master contract 

(Master Contract).

Operational changes, as a result of implementation of 

proposed EIS alternatives, could change the hydrodynamics 

and water-quality conditions in Pueblo Reservoir. An interagency agreement was initiated between Reclamation and the 

U.S. Geological Survey to accurately simulate hydrodynamics 

and water quality in Pueblo Reservoir for projected demands 

associated with four of the seven proposed EIS alternatives.

The four alternatives submitted to the USGS for scenario 

simulation included various combinations (action or no action) 

of the proposed Arkansas Valley Conduit, Master Contract, 

and Interconnect options. The four alternatives were the No 

Action, Comanche South, Joint Use Pipeline North, and 

Master Contract Only. Additionally, scenario simulations were 

done that represented existing conditions (Existing Conditions 

scenario) in Pueblo Reservoir. Water-surface elevations, water 

temperature, dissolved oxygen, dissolved solids, dissolved 

ammonia, dissolved nitrate, total phosphorus, total iron, and 

algal biomass (measured as chlorophyll-a) were simulated. 

Each of the scenarios was simulated for three contiguous water 

years representing a wet, average, and dry annual hydrologic 

cycle. Each selected simulation scenario also was evaluated 

for differences in direct/indirect effects and cumulative effects 

on a particular scenario. Analysis of the results for the direct/
2 Simulated Effects of Proposed Arkansas Valley Conduit, Pueblo Reservoir, Southeastern Colorado

Reclamation, 2011a). Together with available water supplies 

in the Arkansas River Basin, the Project provides an average 

annual water supply of 80,400 acre-feet for both municipal/

domestic use and the supplemental irrigation of 280,600 acres 

in the Arkansas River valley (Bureau of Reclamation, 2011a).

As part of the original 1962 law, authorization was 

included to construct a municipal water-supply pipeline to 

provide communities downstream from Pueblo Reservoir with 

a source of high-quality water; initially, no action was taken 

on the authorization. In 2009, renewed local interest drove an 

initiative to construct such a pipeline and Congress amended 

the original legislation in Public Law 111-11, which authorized appropriations and cost-sharing language to proceed with 

project planning and implementation of the Arkansas Valley 

Conduit (AVC). The purpose of the AVC is to deliver water 

to 41 participants for municipal and industrial use within the 

boundaries of the Southeastern Colorado Water Conservancy 

District (Southeastern Colorado Water Conservancy District, 

2013) (fig. 1). Water supplied through the AVC would serve 

two needs: (1) to supplement or replace existing poor-quality 

water to communities downstream from Pueblo Reservoir; and 

(2) to meet a portion of the AVC participants’ projected water 

demands through 2070 (Bureau of Reclamation, 2011b).

The Bureau of Reclamation (Reclamation) initiated an 

Environmental Impact Statement (EIS) to address the potential environmental consequences associated with constructing 

and operating the proposed AVC, entering into a conveyance 

contract for the Pueblo Dam north-south outlet works interconnect (Interconnect), and entering into a long-term excess 

capacity master contract (Master Contract). Reclamation chose 

to evaluate the environmental effects of these three independent 

proposed actions in the same EIS because of overlap in area, 

timing, and participants. A complete description of the Arkansas Valley Conduit Draft Environmental Impact Statement can 

be found at http://www.usbr.gov/avceis. The Interconnect is a 

pipeline designed to convey water between the existing south 

outlet works and a future north outlet works at Pueblo Reservoir 

to provide a redundant means for release of municipal and 

environmental water from the reservoir (Bureau of Reclamation, 

2011b). The purpose of the Master Contract is to use excesscapacity storage in Pueblo Reservoir to help provide a reliable 

water yield (through 2060) for 15 participants within the boundaries of the Southeastern Colorado Water Conservancy District 

(Bureau of Reclamation, 2011b).

A key element in the preparation of the AVC/Long-Term 

Excess Capacity Master Contract EIS (herein referred to as the 

AVC/Master Contract EIS) is the definition of the purpose, as 

well as, the analysis and documentation of the needs driving 

any proposed action that addresses the AVC and the Master 

Contract (Bureau of Reclamation, 2010). To that end, six action 

alternatives and one no action alternative were evaluated in the 

EIS to meet the purpose and needs of the AVC, Interconnect, 

and Master Contract. Reclamation understands that there 

may be water-based issues (surface-water hydrology, water 

quality, aquatic species, groundwater, wetlands, and recreation) 

associated with each of the proposed alternatives.

As the terminal storage facility for the Project, Pueblo 

Reservoir is the primary source of water for the AVC. Located 

approximately 6 miles west of Pueblo, Colo. (fig. 1), the 

357,678 acre-feet reservoir is one of southeastern Colorado’s 

most valuable water resources (Bureau of Reclamation, 

1977). It provides irrigation, municipal, and industrial water 

to various entities throughout the region. Specifically, water 

is released from Pueblo Reservoir to the Arkansas River 

for downstream irrigation and municipal use, conveyed by 

pipeline for municipal use by Colorado Springs and other 

communities north of the reservoir, and diverted from the 

reservoir for irrigation east of Pueblo (Southeastern Colorado 

Water Conservancy District, 2007). Water also is conveyed to 

Pueblo and Pueblo West through the municipal outlet works in 

Pueblo Dam. A fish hatchery located immediately downstream 

from the reservoir relies on water from the reservoir to raise 

several cold- and warm-water species. The reservoir also 

provides flood control, recreational activities, sport fishing, 

and wildlife enhancement to the region.

Operational changes, as a result of implementation 

of these alternatives, could change the hydrodynamics and 

water-quality conditions in Pueblo Reservoir. Discussions 

with Reclamation and the U.S. Geological Survey (USGS) 

concerning the need to accurately simulate hydrodynamics 

and water quality in Pueblo Reservoir led to an interagency 

agreement between the two Federal agencies to simulate 

the hydrodynamics and water quality of Pueblo Reservoir, 

and to make comparisons of simulated hydrodynamics and 

water quality for projected demands associated with four of 

the seven proposed EIS alternatives. A hydrodynamic and 

water-quality model of Pueblo Reservoir was previously 

developed and calibrated, and the results of the modeling were 

documented by Galloway and others (2008). In this report, the 

modeling described in Galloway and others (2008) is referred 

to as the USGS Pueblo Reservoir model.

Purpose and Scope

The purpose of this report is to compare simulated effects 

on hydrodynamics and water quality for projected demands in 

Pueblo Reservoir resulting from changes in inflow entering the 

reservoir and from changes to withdrawals from the reservoir 

as projected for the year 2070 as described in the AVC/Master 

Contract EIS. Four of the seven EIS alternatives were selected 

for scenario simulations using the USGS Pueblo Reservoir 

model (Galloway and others, 2008) developed from the U.S. 

Army Corps of Engineers CE-QUAL-W2 model (version 3.2) 

(Cole and Wells, 2003). Comparisons of the simulated results 

were conducted to determine if substantial differences were 

observed among selected scenarios.

The four alternatives submitted to the USGS for scenario 

simulation included various combinations (action or no action) 

of the proposed AVC, Master Contract, and Interconnect 

options. Table 1 provides a schematic of how the four 
Introduction 3

Figure 1. Location of the study area.

105°24' 105°12' 105°00' 104°48' 104°36'

38°36'

38°48'

38°12'

38°24'

0 10 MILES

0 10 KILOMETERS

Roads and cities from Colorado Department of Transportation, 1998

Universal Transverse Mecator, Zone 12

North American Datum, 1927

Streamflow station and number 07097000

EXPLANATION

#

PUEBLO

COUNTY

FREMONT

COUNTY

TELLER

COUNTY EL PASO

COUNTY

Florence

Colorado Springs

Security

Fountain

Canon City

Pueblo

West Pueblo

,

Pueblo 

Reservoir

Pueblo

Fourmile C reek

Arkansas River

Hards crabble Creek

Fountain Creek

Turkey Creek

Beaver Cr eek

Williams Creek

50

50

25

115

96

07097000 07097000

07099200

07099400

#

#

#

Area shown 

in figure 2

!

COLORADO

!

!

!

Colorado Springs

Pueblo

DENVER
4 Simulated Effects of Proposed Arkansas Valley Conduit, Pueblo Reservoir, Southeastern Colorado

selected alternatives relate with regard to all the alternatives 

defined in the EIS. Specifically, the four alternatives identified for scenario simulation by the USGS were the No Action 

(EIS Alternative 1), the Comanche South (EIS Alternative 2), 

the Joint-Use Pipeline North (EIS Alternative 4), and the 

Master Contract Only (EIS Alternative 7). Each of the 

scenarios was simulated for three contiguous water years 

(WY) representing a wet (WY 2000), average (WY 2001), 

and dry (WY 2002) annual hydrologic cycle. Streamflow, 

diversion, reservoir storage, and return-flow quantity data for 

projected demands in 2070 were provided to the USGS by 

contractors for Reclamation (Lisa Fardal, MWH Americas, 

Inc., written commun., 2011). Water-quality data for this 

effort were originally provided to the USGS by contractors 

for Reclamation (Tracy Kosloff, MWH Americas, Inc., written commun., 2008) as described for the Existing Conditions 

simulation scenario in Ortiz and Miller (2009).

Additionally, each selected simulation scenario was 

evaluated for differences in direct/indirect effects and cumulative effects on a particular scenario. Direct/indirect effects 

(herein referred to as “direct effects”) are intended to isolate 

the future effects of the scenarios. Cumulative effects are 

intended to evaluate the effects of the scenarios in conjunction 

with all reasonably foreseeable future activities in the study 

area. The primary difference between the two sets of simulations was that the direct-effects simulations include existing levels of demand by nonparticipants in the AVC/Master 

Contract project, whereas the cumulative-effects simulations 

include projected demands in 2070 by the nonparticipants in 

the AVC/Master Contract project (Lisa Fardal, MWH Americas, Inc., oral commun., 2011).

Finally, scenario simulations were modeled using existing conditions in Pueblo Reservoir during water years 2000 

through 2002. The results of the Existing Conditions scenario 

were compared to the No Action scenario to assess changes 

in water quality from current demands (2006) to projected 

demands in 2070. All simulations used an external nutrientdecay model to simulate degradation and assimilation of 

selected nutrients along the riverine reach upstream from 

Pueblo Reservoir as described in Ortiz and Miller (2009).

Methods of Hydrodynamic 

and Water-Quality Simulation

Various modeling tools were used to simulate results for 

comparison between the different simulation scenarios. Reservoir simulations were conducted using a two-dimensional 

water-quality reservoir model. Input data to the reservoir 

model that represented the projected demands in 2070 were 

prepared by Reclamation’s consultant. Nutrient decay and 

assimilation along the riverine reach upstream from Pueblo 

Reservoir were simulated for selected constituents in the 

Arkansas River (Ortiz and Miller, 2009). A brief discussion 

of the reservoir model and development of the input data is 

described in the following sections.

Reservoir Modeling Using CE-QUAL-W2

The development, calibration, and testing of the USGS 

Pueblo Reservoir model was documented by Galloway 

and others (2008). In summary, the laterally averaged, twodimensional model was calibrated at four locations in the 

reservoir (fig. 2) using data collected from October 1985 to 

October 1987 and verified with data from October 1999 to 

October 2002. The 3-year contiguous period from October 1999 

through September 2002 had various hydrologic conditions that 

allowed for verification of the model during a relatively wet 

(WY 2000), average (WY 2001), and dry year (WY 2002). Lake 

hydrodynamics, water temperature, dissolved oxygen, dissolved 

solids, dissolved ammonia, dissolved nitrate (represented by 

dissolved nitrite-plus-nitrate concentrations), total phosphorus, 

total iron, algal groups, and chlorophyll-a (algal biomass) were 

simulated. The model accurately captured the most important 

seasonal and spatial influences on the reservoir water quality 

(Galloway and others, 2008).

CE-QUAL-W2 has been applied to many reservoir systems around the world, and the model will accurately simulate 

the heat budget and water temperature dynamics of a system 

when accurate bathymetric data, a balanced water budget, and 

good meteorological data are provided (Cole and Wells, 2003). 

Table 1. Comparison of Environmental Impact Statement alternatives associated with the proposed Arkansas Valley Conduit and 

identification of four alternatives selected for scenario simulation.

[Selected alternatives are in bold type]

Environmental Impact

Statement Alternative name

Alternative

number

Proposed action

Arkansas

Valley Conduit Interconnect Long-term Excess Capacity Master Contract

No Action Alternative 1 no no no

Comanche South Alternative 2 yes yes yes

Pueblo Dam South Alternative 3 yes no yes

Joint Use Pipeline North Alternative 4 yes yes no

Pueblo Dam North Alternative 5 yes yes yes

River South Alternative 6 yes no yes

Master Contract Only Alternative 7 no no yes
Methods of Hydrodynamic and Water-Quality Simulation 

5

Figure 2. Location of selected sites on the Arkansas River and Pueblo Reservoir.

105°00' 104°54' 104°48' 104°42'

38°24'38°21'38°18'38°15'

#

#

#

# Streamflow station and number

Pueblo Reservoir site location and identifier

07097000

7B

EXPLANATION

Roads and cities from Colorado Department of Transportation, 1998Universal Transverse Mecator, Zone 12North American Datum, 1927

0 3 6 MILES

0 3 6 KILOMETERS

07097000

07099200

07099400

Upper extent of 

the Pueblo Reservoir 

model grid

1B

3B

7B

5C

381628104381700

96

50

Pueblo

Reservoir

Beaver

Creek

Tu

rke y Creek Wildhors e Creek Arkansas River

Rush Creek

Peck

er C ek

Roc k Cr eek

Bo

ggs

Creek

Bessemer Ditch

Arkansas River

Pueblo West

Pueblo
6 Simulated Effects of Proposed Arkansas Valley Conduit, Pueblo Reservoir, Southeastern Colorado

Past performance and recent USGS applications of this model 

have demonstrated its success in simulating water temperature 

in reservoir systems (Galloway and others, 2008; Sullivan and 

others, 2007; Sullivan and Rounds, 2004; Bales and others, 

2001; Green, 2001; Rounds and Wood, 2001). Similarly, 

the model’s water-quality predictions should be useful and 

relatively accurate as long as the water-quality algorithms in 

CE-QUAL-W2 capture the most important processes affecting 

water quality in the reservoir, and if the processes that control 

the water quality in the reservoir do not change substantially 

over time. Although the Pueblo Reservoir model was constructed and calibrated for conditions observed in WY 1986 

through WY 1987, it should be able to make useful predictions of future changes in the hydrodynamic, thermal, and 

water-quality conditions in the reservoir. This usefulness was 

demonstrated by the results of the model verification that used 

data collected more than a decade after the calibration period 

(Galloway and others, 2008). Several other USGS studies have 

demonstrated the application of the CE-QUAL-W2 model to 

water-quality constituents (Green, 2001; Sullivan and Rounds, 

2005; and Galloway and Green, 2006).

Streamflow and Water-Quality Modeling 

for Projected Demands in 2070

Hydrologic operations of Pueblo Reservoir were 

simulated using the Arkansas River Daily Simulation Model 

(Daily Model), which used the MODSIM software developed 

by Colorado State University and Reclamation as the primary 

model engine (Labadie and others, 2000). The MODSIM 

software is driven by time-series inflow and demand data 

contained at nodes, water rights information contained in the 

links, and reservoir storage information contained at reservoir 

nodes. The Daily Model simulated basin operations on a daily 

time step by moving inflows and stored water to demands 

using the priority information contained in the links and 

other physical and operational constraints found in both links 

and nodes. Simulation for the AVC EIS was done on a daily 

time step for the study period of WY 1982 through WY 2009 

(Lisa Fardal, MWH Americas, Inc., written commun., 2011).

The Daily Model superimposed existing water rights, 

water development operations, and water demand conditions 

on historical hydrology. Data required for input into the model 

included historical streamflow data, historical and future 

diversion data, historical storage data, water-rights data, and 

other miscellaneous data. Ungaged gains and losses were 

calculated using the ArkExcel Microsoft Excel spreadsheet 

model, which is an adaptation of the previous ArkEx exchange 

model used by Colorado Springs Utilities for their Arkansas 

River Exchange Program (MWH Americas, Inc., 2008). 

Ungaged gains and losses then were entered in the Daily 

Model as constant values through the reaches for each day.

Streamflow and storage data pertinent to the modeling 

effort described in this report (reservoir inflows, outflows, and 

storage) were extracted from the Daily Model runs for selected 

simulation scenarios for October 1, 1999, to September 30, 2002 

(Lisa Fardal, MWH Americas, Inc., written commun., 2011).

Description of Simulation Scenarios

The simulation scenarios selected for modeling as part 

of this report were the No Action, Comanche South, Joint 

Use Pipeline North, and Master Contract Only scenarios. 

The four simulation scenarios are described in more detail 

below and a summary of how the four selected scenarios 

related to the seven EIS alternatives can be found in table 1. 

A detailed description of all the alternatives can be found 

in Chapter 2 of the Draft Environmental Impact Statement–

Arkansas Valley Conduit and Long-term Excess Capacity 

Master Contract, Fryingpan-Arkansas Project (Bureau of 

Reclamation, 2012). Additionally, a simulation scenario 

that represented existing conditions (demand conditions 

for 2011) was run using water-quality input files that were 

similar to those used in the verification period of the Pueblo 

Reservoir model (Galloway and others, 2008) and streamflow 

and storage data based on Daily Model results (Lisa Fardal, 

MWH Americas, Inc., written commun., 2011). For the 

purposes of this report, this scenario is described as the 

Existing Conditions scenario.

Input data that represented the projected streamflow, 

diversion data, and reservoir storage (stage) for each of 

the simulation scenarios were provided to the USGS by 

Reclamation’s consultant (Lisa Fardal, MWH Americas, 

Inc., written commun., 2011). Specifically, simulated streamflow data were provided for each scenario representing 

inflow to Pueblo Reservoir at Portland (USGS streamflow 

station 07097000) and outflow downstream from Pueblo 

Reservoir (USGS streamflow station 07099400) as simulated by Reclamation’s consultant. Diversion data also were 

provided representing projected removal of water from 

Pueblo Reservoir for delivery to various entities in the study 

area. Additionally, projected daily reservoir storage for each 

scenario was provided to the USGS.

The input water-quality data for all the simulation 

scenarios in this report were identical to those used in the 

Existing Conditions scenario as described in Ortiz and 

Miller (2009). The data reflect the results of an initial simulation effort to decay and assimilate nutrient concentrations. 

This approach to the scenario simulations was done to simulate changes in nutrient concentrations in the Arkansas River 

upstream from Pueblo Reservoir to Portland (fig. 1).
General Comparisons Between All Simulation Scenarios 7

No Action Scenario

Required by the National Environmental Policy Act, 

this alternative represents future conditions without the AVC, 

Interconnect, and Master Contract. Water-supply and waterquality needs for this scenario are met using regional water 

treatment systems or local independent systems. Participants 

with existing water supplies and treatment systems that meet 

primary drinking standards would continue to use these supplies, whereas participants under water-quality enforcement 

actions would either upgrade water treatment facilities to meet 

primary drinking water standards, or regionalize with a larger 

entity. The No Action scenario states that the Master Contract 

would not be issued and the Interconnect would not be constructed (Bureau of Reclamation, 2011b).

Comanche South Scenario

The Comanche South scenario represents water diverted 

from the existing Pueblo Reservoir south outlet works. A new 

pipeline would be built along the existing Comanche Power 

Plant pipeline route south of Pueblo and generally along 

Highway 50 east of Pueblo for 235 miles. Excess capacity 

storage in Pueblo Reservoir (about 30,000 acre-feet annually) 

would be issued as part of the Master Contract. The Comanche 

South scenario also states that construction of the Interconnect 

would be completed (Bureau of Reclamation, 2011b).

Joint Use Pipeline North Scenario

The Joint Use Pipeline North scenario utilizes excess 

capacity available in the existing Joint Use Pipeline from 

Pueblo Dam downstream about 4 miles. A new pipeline would 

be built from that location to the existing water treatment plant 

in northwest Pueblo. A new pipeline would be built from the 

water treatment plant generally to the north side of Highway 

50 east of Pueblo for about 233 miles. This scenario states that 

the Master Contract would not be issued but the Interconnect 

would be constructed (Bureau of Reclamation, 2011b).

Master Contract Only Scenario

As the Master Contract Only scenario implies, excess 

capacity storage in Pueblo Reservoir (about 30,000 acre-feet) 

would be issued as part of the Master Contract; the AVC 

and Interconnect are not constructed under this scenario. 

Participants would pursue actions similar to those for the 

No Action Alternative to meet their water-supply and waterquality needs (Bureau of Reclamation, 2011b).

Existing Conditions Scenario

This scenario represented the existing conditions in Pueblo 

Reservoir (demand conditions for 2006) as simulated during 

the verification period of the calibrated Pueblo Reservoir model 

(Galloway and others, 2008) with minor changes to the water 

quality that enters the reservoir resulting from simulated decay 

of nutrients in the riverine reach upstream from the reservoir 

(Ortiz and Miller, 2009). Specifically, simulation results for the 

No Action scenario were compared to results for the Existing 

Conditions scenario.

General Comparisons Between 

All Simulation Scenarios

Each of the four selected simulation scenarios was evaluated for the direct- and cumulative-effects analyses. As stated 

earlier in this report, direct effects are intended to isolate the 

future effects of the scenarios, whereas cumulative effects 

are intended to evaluate the effects of all reasonably foreseeable future activities in the study area on a simulation scenario 

(Lisa Fardal, MWH Americas, Inc., written commun., 2011). 

The primary difference between the two sets of simulations was 

that the direct-effects-scenario simulations include existing levels of demand by nonparticipants in the AVC/Master Contract 

project, whereas the cumulative-effects-scenario simulations 

include projected demands in 2070 by the nonparticipants in 

the AVC/Master Contract project. Quantification of the differences between the two different effects analyses was modeled 

by Reclamation’s consultant, and input data were provided to 

the USGS by the consultant (Lisa Fardal, MWH Americas, Inc., 

written commun., 2011). Additionally, the four scenarios were 

modeled and comparisons were made within the context of 

three (wet, average, and dry) hydrologic conditions.

Two of the four sites in the previous Pueblo Reservoir 

simulation effort (Galloway and others, 2008) were selected 

for comparison in this report. Results of scenario simulations 

at site 3B were characteristic of a riverine environment in 

the reservoir (fig. 2). The other upstream site, 1B, often was 

dry during the scenario simulations and was not chosen for 

comparisons in this report. Results of scenario simulations at 

site 7B were characteristic of the main body of the reservoir in 

the forebay near the dam wall (fig. 2). The other “deep water” 

site, 5C, displayed similar results to 7B and, as such, was not 

chosen for comparisons in this report. Simulation results in the 

epilimnion (near surface) and the hypolimnion (near bottom) 

at sites 7B and 3B were evaluated and compared. Located near 

the Pueblo Dam, the simulation results in the hypolimnion at 

site 7B were indicative of the quality of the water leaving the 

reservoir. Each of the sites also was compared with regard to 

depth in the water column.
8 Simulated Effects of Proposed Arkansas Valley Conduit, Pueblo Reservoir, Southeastern Colorado

The following discussion focuses on a general comparison 

between all simulation scenarios including the Existing 

Conditions scenario. The focus is to describe the general patterns 

observed for the simulated results, and discusses how the 

simulation scenarios compare to each other. Selected graphics 

are presented as a means to describe the results. Some discussion 

will involve the similarities and differences observed between 

the direct- and cumulative-effects analyses, as they pertain to 

individual scenarios. The following discussion primarily focuses 

on results from site 7B near the dam. Results from the upstream 

riverine site, 3B, were similar to those from 7B but more variable 

because of the dynamic changes in water-surface elevations 

observed at this upstream location. Additionally, water quality 

at this site tended to be more reactive given the proximity of the 

site to river inputs. When appropriate, results from site 3B will 

be discussed.

Water-surface elevations in Pueblo Reservoir were 

directly related to the active storage in the reservoir (Bureau 

of Reclamation, 1977) and were inherently driven by changes 

in inflow/outflow data. As such, storage in the reservoir was 

the primary differentiator between simulation scenarios 

described in this report. Water-quality inputs to the modeling 

were identical for all simulation scenarios as submitted by 

consultants for Reclamation (Lisa Fardal, MWH Americas, 

Inc., written commun., 2011).

Simulated water-surface elevations in Pueblo Reservoir 

were variable between the simulation scenarios, between the 

different effects analyses, and between the simulated hydrologic 

conditions (fig. 3). Generally, there was a substantial temporal 

decrease in water-surface elevations between the wet, average, 

and dry years. Water-surface elevations associated with the 

direct-effects analyses were higher than the water-surface 

elevations for the corresponding cumulative-effects analyses, 

and the differences between the effects analyses, for any 

scenario, increased temporally from wet to dry year. During 

the dry year (WY 2002), the lowest water-surface elevations 

for either the direct-effects or cumulative-effects analysis were 

associated with the No Action and Joint Use Pipeline North 

Figure 3. Comparison of water-surface elevations in Pueblo Reservoir for the Existing Conditions 

scenario (water years 2000 through 2002) and cumulative- and direct-effects analyses for selected 

simulation scenarios. Datum is North American Vertical Datum of 1988 (NAVD 88).

O N D J F M A M J J A S O N D J F M A M J J A S

Water year 2001

(average year)

O N D J F M A M J J A S

Water year 2002

(dry year)

Water year 2000

(wet year)

4,790

4,823

4,856

4,889

4,922

Reservoir water-surface elevation, in feet

1,460

1,470

1,480

1,490

1,500

Reservoir water-surface elevation, in meters

No Action—Cumulative effects

No Action—Direct effects

Comanche South—Cumulative effects

Comanche South—Direct effects

Joint Use North Pipeline—Cumulative effects

Joint Use North Pipeline—Direct effects

Master Contract Only—Cumulative effects

Master Contract Only—Direct effects

Existing Conditions

EXPLANATION
Comparison of Results for Selected Simulation Scenarios 9

scenarios; these two scenarios do not include an excess capacity 

storage component as part of the proposed EIS alternative. 

Simulated water-surface elevations for the direct-effects 

analysis of any simulation scenario during WY 2000 (wet year) 

and WY 2001 (average year) were similar to the water-surface 

elevations for the Existing Conditions scenario. Water-surface 

elevations during WY 2002 (dry year) remained similar to those 

of the Existing Conditions scenario with the exception of the 

Joint Use Pipeline North scenario.

Water temperature is an important component of the 

hydrodynamics in a reservoir. Life processes, chemical 

reactions, and the solubility of chemical constituents in 

water are all temperature dependent. Water temperature also 

is a major factor in controlling the density of freshwater 

that drives stratification in a reservoir and routing of 

inflows in a reservoir. Pueblo Reservoir has been shown to 

stratify during the summer (June-August) prior to mixing 

in September (Edelmann, 1989). Results from the various 

simulation scenarios showed a similar pattern (fig. 4), which 

also was consistent with previous simulations by Ortiz and 

Miller (2009). In general, the reservoir has been shown 

to be isothermal during the winter with the coldest water 

temperatures occurring from December to April. Typically, 

thermal stratification is apparent by May at site 3B (riverine 

site) and 7B (near-dam site). Maximum water temperatures 

were observed in August prior to when Pueblo Reservoir 

typically mixed in September at the deeper locations.

In general, the water temperatures in Pueblo Reservoir 

were similar for all the simulation scenarios for the 3-year 

simulation period regardless of the effects analysis (fig. 5). 

There were no substantial changes in the annual thermal 

pattern between the three simulated years (fig. 5).

Adequate concentrations of dissolved oxygen (DO) 

are critical to the health of a water body and its aquatic 

biota. Results of the scenario simulations showed the typical 

stratification patterns that occur in Pueblo Reservoir (Edelmann, 

1989) including anoxic conditions observed near the bottom 

of the reservoir during the summer before the reservoir turned 

over and mixed (fig. 6). DO concentrations in the epilimnion 

and hypolimnion of the reservoir near the dam were similar to 

the Existing Conditions scenario for all the simulation scenarios 

regardless of the effects analysis (fig. 7). At either depth, 

maximum DO concentrations occurred in the early spring when 

water temperatures also were at minimum; colder water has 

the capacity for higher DO concentrations (Hem, 1985). DO 

concentrations of less than 6 milligrams per liter (mg/L) were 

simulated in the epilimnion during September and October for 

all selected simulation scenarios. These lower concentrations 

lagged about a month behind the anoxic conditions simulated 

in the hypolimnion. It did not appear that the anoxic period 

was substantially longer for any particular simulation scenario 

and there appeared to be no substantial change in the general 

seasonal pattern in the epilimnion and hypolimnion between 

the wet, average, and dry years.

Typically, the simulated dissolved solids (DS) 

concentrations for the Existing Conditions scenario were 

similar to concentrations for all the direct-effects simulation 

scenarios (fig. 8A). Concentrations for the cumulative-effects 

simulation scenarios were slightly larger than concentrations 

for the Existing Conditions scenario; typically less than 

5 percent different but could be as much as 10 percent 

different during the winter months. Concentrations for the 

cumulative-effects simulation scenarios were similar among 

themselves. These results would be expected given that the 

reservoir storage for the cumulative-effects analyses was 

less, due to an increase water demand in the future, than that 

for the direct-effect analyses (fig. 3) and water-quality inputs 

were identical.

Nitrogen is essential for primary production in a 

reservoir. Ammonia is one of the more commonly used and 

measured aqueous nitrogen species. In the CE-QUAL-W2 

model, dissolved ammonia concentrations are inherently 

linked to other simulated constituents such as water 

temperature, DO concentrations, and algal concentrations. 

Simulated dissolved ammonia concentrations provided 

another illustration of the general patterns observed between 

the various simulation scenarios and between the directand cumulative-effects analyses. In general, the simulated 

dissolved ammonia concentrations for the Existing Conditions 

scenario were similar to the concentrations for all the other 

simulation scenarios whether for direct-effects or cumulativeeffects analyses (fig. 8B).

Comparison of Results for

Selected Simulation Scenarios

The previous discussion compared the results of the 

simulation scenarios in the context of general similarities or 

differences in the simulated results. However, quantitative 

comparisons between specific scenarios were done to support 

Reclamation’s decisions as part of the EIS process. These 

comparisons will be discussed in the following sections of 

this report. Specifically, comparisons were made between 

the Existing Conditions scenario and the No Action scenario 

to determine what differences, if any, were observed 

between existing conditions in Pueblo Reservoir (demand 

conditions for 2006) and the most likely conditions in 2070 

assuming the absence of a major Reclamation action, such 

as the AVC or a storage contract. Additionally, comparisons 

were made between the No Action scenario and each of 

the other scenarios—the Comanche South scenario, the 

Joint Use Pipeline North scenario, and the Master Contract 

Only scenario. These comparisons provided information 

that allowed for a correlation of the effectiveness of each 

scenario relative to a common simulated result, the No 

Action scenario.
10 Simulated Effects of Proposed Arkansas Valley Conduit, Pueblo Reservoir, Southeastern Colorado

Figure 4. Simulated water temperature profiles for Pueblo Reservoir, Colorado, at site 7B, April 2001 through January 2002. 

Datum is North American Vertical Datum of 1988 (NAVD 88).

April 8, 2001 May 24, 2001 June 15, 2001

August 23, 2001 October 10, 2001 January 18, 2002

4,750

4,775

4,800

4,825

4,850

4,875

4,900

4,750

4,775

4,800

4,825

4,850

4,875

4,900

Reservoir water elevation, in feet Reservoir water elevation, in feet

Water temperature, in degrees Celsius 

1,448

1,456

1,464

1,471

1,479

1,487

1,495

Reservoir water elevation, in meters Reservoir water elevation, in meters

1,448

1,456

1,464

1,471

1,479

1,487

1,495

0 10 20 30 0 10 20 30 0 10 20 30

0 10 20 30 0 10 20 30 0 10 20 30
Comparison of Results for Selected Simulation Scenarios 11

Figure 5. Comparison of water temperatures in the epilimnion at site 7B in Pueblo Reservoir 

for the Existing Conditions scenario (water years 2000 through 2002) and cumulative- and directanalyses for selected simulation scenarios.

Comparison of Existing Conditions Scenario 

and No Action Scenario

For the purposes of this report, comparisons between 

scenarios were conducted for site 3B in the upstream riverine 

section of the reservoir and site 7B in the main body in 

Pueblo Reservoir near the dam structure (fig. 2). Analysis 

of the results for the direct- and cumulative-effects analyses 

indicated that, in general, the results were similar for most of 

the scenarios. Additionally, simulated results for cumulativeeffects analyses scenarios were more likely to be reported as 

uncomputed at the more shallow upstream riverine site (3B) 

as reservoir water-surface elevations decreased in WY 2001 

and WY 2002 and the site “dried up.” As such, comparisons in 

this section and throughout this report will focus on the results 

from the direct-effects analysis for each modeled scenario. 

Results from the cumulative-effects analyses were tabulated 

and are presented in the appendixes at the back of the report.

Annual median concentrations were calculated for each 

constituent for each of the simulated water years in the epilimnion and hypolimnion for each of the two reservoir sites. 

The annual 85th percentile concentrations also were compared 

as they relate to possible water-quality standards; for DO, the 

15th percentile was used because anoxic conditions are important in Pueblo Reservoir. It should be noted that simulation 

results and any comparisons to water-quality standards should 

not be interpreted as definitive values but as an estimate given 

the uncertainties of the modeling processes. Water-surface elevations at site 3B were insufficient to compute results for some 

of the simulation scenarios during the later period of WY 2001 

(August and September) and much of WY 2002. As such, 

annual summary statistics only were calculated when 70 percent or more of the simulated daily values were available for 

computation. Caution should be used when comparing summary statistics for WY 2001 and WY 2002 at site 3B because 

the resultant value may be skewed due to the lack of seasonal 

values in the computation. Comparisons were made using the 

O N D J F M A M J J A S O N D J F M A M J J A S

Water year 2001

(average year)

O N D J F M A M J J A S

Water year 2002

(dry year)

Water year 2000

(wet year)

0

5

10

15

20

25

30

Surface-water temperature, in degrees Celsius

No Action—Cumulative effects

No Action—Direct effects

Comanche South—Cumulative effects

Comanche South—Direct effects

Joint Use North Pipeline—Cumulative effects

Joint Use North Pipeline—Direct effects

Master Contract Only—Cumulative effects

Master Contract Only—Direct effects

Existing Conditions

EXPLANATION
12 Simulated Effects of Proposed Arkansas Valley Conduit, Pueblo Reservoir, Southeastern Colorado

Figure 6. Simulated dissolved oxygen profiles for Pueblo Reservoir, Colorado, at site 7B, April 2001 through January 2002. 

Datum is North American Vertical Datum of 1988 (NAVD 88).

0 3 6 9 12 0 3 6 9 12 0 3 6 9 12

0 3 6 9 12 0 3 6 9 12 0 3 6 9 12

Dissolved oxygen, in milligrams per liter 

April 8, 2001 May 24, 2001 June 15, 2001

August 23, 2001 October 10, 2001 January 18, 2002

4,750

4,775

4,800

4,825

4,850

4,875

4,900

4,750

4,775

4,800

4,825

4,850

4,875

4,900

Reservoir water-surface elevation, in feet Reservoir water-surface elevation, in feet

1,448

1,456

1,464

1,471

1,479

1,487

1,495

1,448

1,456

1,464

1,471

1,479

1,487

1,495

Reservoir water-surface elevation, in meters Reservoir water-surface elevation, in meters
Comparison of Results for Selected Simulation Scenarios 13

Figure 7. Comparison of dissolved oxygen concentrations at site 7B in Pueblo Reservoir for the Existing Conditions 

scenario (water years 2000 through 2002) and cumulative- and direct-effects analyses for selected simulation scenarios.

O N D J F M A M J J A S O N D J F M A M J J A S O N D J F M A M J J A S

Water year 2001

(average year)

Water year 2002

(dry year)

Water year 2000

(wet year)

O N D J F M A M J J A S O N D J F M A M J J A S O N D J F M A M J J A S

Water year 2001

(average year)

Water year 2002

(dry year)

Water year 2000

(wet year)

Epilimnion

Hypolimnion

A

B

0

3

6

9

12

15

Dissolved oxygen, in milligrams per liter Dissolved oxygen, in milligrams per liter

0

3

6

9

12

15

No Action—Cumulative effects

No Action—Direct effects

Comanche South—Cumulative effects

Comanche South—Direct effects

Joint Use Pipeline North—Cumulative effects

Joint Use Pipeline North—Direct effects

Master Contract Only—Cumulative effects

Master Contract Only—Direct effects

Existing Conditions

EXPLANATION
14 Simulated Effects of Proposed Arkansas Valley Conduit, Pueblo Reservoir, Southeastern Colorado

Figure 8. Comparison of (A) dissolved solids and (B) dissolved ammonia concentrations at site 7B in Pueblo Reservoir for 

the Existing Conditions scenario (water years 2000 through 2002) and cumulative- and direct-effects analyses for selected 

simulation scenarios.

O N D J F M A M J J A S O N D J F M A M J J A S O N D J F M A M J J A S

Water year 2001

(average year)

Water year 2002

(dry year)

Water year 2000

(wet year)

O N D J F M A M J J A S O N D J F M A M J J A S O N D J F M A M J J A S

Water year 2001

(average year)

Water year 2002

(dry year)

Water year 2000

(wet year)

Epilimnion

Epilimnion

A

B

0.00

0.01

0.02

0.03

0.04

0.05

Dissolved solids, in milligrams per liter

100

150

200

250

300

350

400

Dissolved ammonia, in milligrams per liter

No Action—Cumulative effects

No Action—Direct effects

Comanche South—Cumulative effects

Comanche South—Direct effects

Joint Use Pipeline North—Cumulative effects

Joint Use Pipeline North—Direct effects

Master Contract Only—Cumulative effects

Master Contract Only—Direct effects

Existing Conditions

EXPLANATION
Comparison of Results for Selected Simulation Scenarios 15

Figure 9. Comparison of water-surface elevations in Pueblo Reservoir for the Existing Conditions (water 

years 2000 through 2002) and No Action scenarios. Datum is North American Vertical Datum of 1988 (NAVD 88).

differences in the calculated summary statistic (median, 85th 

or 15th percentiles) and by calculating the percent change in 

concentrations between the Existing Conditions and the No 

Action scenarios and between the No Action scenario and each 

of three other simulation scenarios.

Water-Surface Elevations

In general, simulated water-surface elevations in Pueblo 

Reservoir were similar between the Existing Conditions and No 

Action scenarios (fig. 9). Overall, there was a temporal decrease 

in water-surface elevations from the wet year (WY 2000) to 

the dry year (WY 2002). Over the three-year simulation period, 

maximum water-surface elevations decreased from about 

4,890 feet (ft) to about 4,870 ft (1,489 meters (m) to 1,484 m, 

respectively); the annual maximum elevation decreased about 

6 ft per year. Typically, maximum storage occurred in late 

March of each year as winter storage was nearly complete and 

releases of water to downstream irrigators had not yet started.

Water Temperature

Comparisons of the results between the Existing 

Conditions and the No Action scenarios indicated similar patterns in water temperature over the simulation period (fig. 10). 

At site 7B near the dam, the percent change from the Existing 

Conditions scenario was within 4 percent for all simulated years 

and was nearly identical for all comparisons in the epilimnion 

(table 2). Water temperatures in the hypolimnion were about 

4 degrees Celsius (°C) cooler than those in the epilimnion 

but relatively similar between scenarios at site 7B. At site 3B, 

the annual median water temperatures in the epilimnion and 

hypolimnion were similar (less than or equal to a 3 percent 

change) between the two scenarios (table 3). At site 3B, water 

temperatures in the hypolimnion were about 2 °C cooler than 

those in the epilimnion but relatively similar between scenarios 

(table 3).

Dissolved Oxygen

Comparisons of the DO simulation results between the 

Existing Conditions and No Action scenarios indicated that 

the annual median values for the two scenarios generally 

were similar (fig. 11). At site 7B, the percent change from the 

Existing Conditions scenario was within 3 percent of the No 

Action scenario for all simulated years in both the epilimnion 

or the hypolimnion (table 2). The median values in the hypolimnion generally were about 0.5 mg/L lower than concentrations in the epilimnion. At site 3B, median DO concentrations 

were similar between scenarios and reservoir depths (table 3); 

the largest observed difference was 0.2 mg/L during WY 2001.

O N D J F M A M J J A S O N D J F M A M J J A S O N D J F M A M J J A S

Water year 2001

(average year)

Water year 2002

(dry year)

Water year 2000

(wet year)

4,790

4,823

4,856

4,889

4,922

Reservoir water-surface elevation, in feet

1,460

1,470

1,480

1,490

1,500

Reservoir water-surface elevation, in meters

No Action—Direct effects

Existing Conditions

EXPLANATION
16 Simulated Effects of Proposed Arkansas Valley Conduit, Pueblo Reservoir, Southeastern Colorado

Figure 10. Annual median water temperature in the epilimnion 

and hypolimnion at site 7B for the Existing Conditions (water 

years 2000 through 2002) and No Action (direct-effects analysis) 

scenarios.

Table 2. Percent change between annual median values for selected constituents in the epilimnion and hypolimnion at site 7B for the 

Existing Conditions scenario (water years 2000 through 2002) as compared to the No Action (direct-effects analysis) scenario.

[N, nitrogen; P, phosphorus; °C, degrees Celsius; mg/L, milligrams per liter; μg/L, micrograms per liter; NA, not applicable; <, less than]

Water

year

Simulation

scenario

Percent of

annual

results

available

Water

temperature

(°C)

Dissolved

oxygen

(mg/L)

Dissolved

solids

(mg/L)

Dissolved

ammonia

as N

(mg/L)

Dissolved

nitrate

as N

(mg/L)

Total

phosphorus

as P

(mg/L)

Total

iron

(mg/L)

Chlorophyll-a

(μg/L)

Epilimnion

2000 Existing Conditions 100 14.6 7.8 283 0.003 0.006 0.014 <0.001 0.55

No Action 100 14.5 7.9 281 .003 .006 .014 <.001 .53

Percent change –0.7% 1.3% –0.7% 0% 0% 0% NA –3.6%

2001 Existing Conditions 100 14.6 7.8 229 .003 .009 .016 <.001 .26

No Action 100 14.6 7.8 231 .003 .009 .017 <.001 .25

Percent change 0% 0% 0.9% 0% 0% 6.2% NA –3.8%

2002 Existing Conditions 100 14.4 8.0 233 .003 .007 .017 <.001 .30

No Action 100 14.4 8.0 235 .004 .007 .017 <.001 .30

Percent change 0% 0% 0.9% 33% 0% 0% NA 0%

Hypolimnion

2000 Existing Conditions 100 10.7 7.5 284 .010 .006 .015 .005 .12

No Action 100 10.5 7.6 281 .009 .005 .015 .005 .12

Percent change –1.9% 1.3% –1.1% –10% –17% 0% 0% 0%

2001 Existing Conditions 100 9.6 7.6 233 .007 .008 .017 .003 .07

No Action 100 9.3 7.7 234 .007 .009 .018 .003 .05

Percent change –3.1% 1.3% .4% 0% 12% 5.9% 0% –29%

2002 Existing Conditions 100 9.7 8.0 233 .006 .005 .017 <.001 .06

No Action 100 9.6 7.8 235 .006 .005 .018 <.001 .07

Percent change –1.0% –2.5% 0.9% 0% 0% 5.9% NA 17%

The minimum DO concentration suitable to meet the DO 

water-quality standard in Pueblo Reservoir as defined by the 

State of Colorado is 6.0 mg/L as measured in the epilimnion 

of the water body (Colorado Department of Public Health 

and Environment, 2007). The standard is compared to the 

15th percentile of the annual data values. For the Existing 

Conditions and No Action scenarios, the simulated 15th percentile value in the epilimnion at sites 7B and 3B was typically at or slightly below the standard value (tables 4 and 5). 

Caution should be used when comparing these results to the 

water-quality standard because the absolute mean error of 

the DO calibration was 1.42 mg/L at site 7B for the Pueblo 

Reservoir model (Galloway and others, 2008). Simulated DO 

concentrations (daily) were suppressed below 6.0 mg/L during 

much of August through November for each of the simulated 

water years (fig. 7).

Dissolved Solids

Dissolved solids concentrations for the Existing Conditions 

and No Action scenarios were similar between the two scenarios 

and at both of the simulated depths for any particular water 

year (fig. 12). Typically, the percent change between the annual 

median DS concentration for either of the scenarios was less 

than 2 percent (tables 2 and 3).

No water-quality standard for DS exists for Pueblo 

Reservoir. However, a guideline for aesthetic considerations, 

such as taste, color, and odor in public water systems, the secondary maximum contaminant level, is set at 500 mg/L by the 

0

5

10

15

20

25

Water temperature, in degress Celsius

Water year

2000 2001 2002

Existing Conditions—Epilimnion

No Action—Epilimnion

Existing Conditions—Hypolimnion

No Action—Hypolimnion

EXPLANATION
Comparison of Results for Selected Simulation Scenarios 17

Table 3. Percent change between annual median values for selected constituents in the epilimnion and hypolimnion at site 3B for the 

Existing Conditions scenario (water years 2000 through 2002) as compared to the No Action (direct-effects analysis) scenario. 

[N, nitrogen; P, phosphorus; °C, degrees Celsius; mg/L, milligrams per liter; μg/L, micrograms per liter; NA, not applicable; <, less than]

Water

year

Simulation

scenario

Percent of

annual

results

available

Water

temperature

(°C)

Dissolved

oxygen

(mg/L)

Dissolved

solids

(mg/L)

Dissolved

ammonia

as N

(mg/L)

Dissolved

nitrate

as N

(mg/L)

Total

phosphorus

as P

(mg/L)

Total

iron

(mg/L)

Chlorophyll-a

(μg/L)

Epilimnion

2000 Existing Conditions 100 14.1 7.9 287 0.001 0.005 0.015 0.010 0.98

No Action 100 14.0 7.9 282 .001 .005 .015 .010 .91

Percent change –.7% 0% –1.7% 0% 0% 0% 0% –7.1%

2001 Existing Conditions 100 13.5 8.0 235 .002 .019 .018 .010 .74

No Action 100 13.9 7.8 235 .002 .017 .018 .009 .75

Percent change 3.0% –2.5% 0% 0% –11% 0% –10% 1.4%

2002 Existing Conditions 100 13.4 7.9 260 .003 .008 .023 .013 1.41

No Action 100 13.4 7.9 260 .003 .008 .023 .014 1.29

Percent change 0% 0% 0% 0% 0% 0% 7.7% –8.5%

Hypolimnion

2000 Existing Conditions 100 12.1 7.8 286 .002 .013 .016 .029 .68

No Action 100 12.0 7.8 282 .002 .012 .016 .031 .70

Percent change –8% 0% –1.4% 0% –7.7% 0% 6.9% 2.9%

2001 Existing Conditions 100 11.1 7.8 239 .003 .036 .019 .027 .51

No Action 100 11.2 7.6 239 .003 .033 .019 .027 .51

Percent change .9% –2.6% 0% 0% –8.3% 0% 0% 0%

2002 Existing Conditions 100 12.2 7.8 260 .003 .009 .022 .020 1.40

No Action 100 12.3 7.8 260 .003 .009 .022 .022 1.31

Percent change .8% 0% 0% 0% 0% 0% 10% –6.4%

Figure 11. Annual median dissolved oxygen concentrations 

in the epilimnion and hypolimnion at site 7B for the Existing 

Conditions (water years 2000 through 2002) and No Action (directeffects analysis) scenarios.

Water year

2000 2001 2002

0

3

6

9

12

15

Dissolved oxygen, in milligrams per liter

Existing Conditions—Epilimnion

No Action—Epilimnion

Existing Conditions—Hypolimnion

No Action—Hypolimnion

EXPLANATION

U.S. Environmental Protection Agency (U.S. Environmental 

Protection Agency, 1992). Neither the annual median nor the 

85th percentile values exceeded this threshold in the epilimnion 

and hypolimnion at sites 7B and 3B for either of two simulation 

scenarios (tables 4 and 5).

Major Nutrients

Compounds of nitrogen (N) and phosphorus (P) are 

referred to as “major nutrients” because they are needed for 

plant growth. In excess concentrations, nutrients can promote 

nuisance algal growth in streams, reservoirs, and other water 

bodies (eutrophication). Natural sources of nutrients include 

precipitation and biogeochemical processes in the watershed. 

Anthropogenic sources of nutrients include but are not limited 

to urban runoff, domestic effluent, livestock waste, and erosion 

caused by development (Graffy and others, 1996).

Dissolved Ammonia

Generally, the annual median dissolved ammonia 

concentrations (as nitrogen (N)) in the epilimnion of 

Pueblo Reservoir at site 7B were similar for the Existing 

Conditions and the No Action scenarios. Concentrations in 

the epilimnion were slightly larger in WY 2002 for the No 

Action scenario but the difference was only 0.001 mg/L as 

N (fig. 13 and table 2). Concentrations in the hypolimnion 

were slightly larger in WY 2000 for the Existing Conditions 

scenario but, again, the difference was only 0.001 mg/L as 

N. Concentrations in the hypolimnion generally were about 
18 Simulated Effects of Proposed Arkansas Valley Conduit, Pueblo Reservoir, Southeastern Colorado

Table 4. Percent change between annual 85th percentile values for selected constituents and the annual 15th percentile values for 

dissolved oxygen concentrations in the epilimnion and hypolimnion at site 7B for the Existing Conditions scenario (water years 2000 

through 2002) as compared to the No Action (direct-effects analysis) scenario.

[N, nitrogen; P, phosphorus; °C, degrees Celsius; mg/L, milligrams per liter; μg/L, micrograms per liter; NA, not applicable; <, less than]

Water

year

Simulation

scenario 

Percent of

annual

results

available

Water

temperature

(°C)

Dissolved

oxygen

(mg/L)

Dissolved

solids

(mg/L)

Dissolved

ammonia

as N

(mg/L)

Dissolved

nitrate

as N

(mg/L)

Total

phosphorus

as P

(mg/L)

Total

iron

(mg/L)

Chlorophyll-a

(μg/L)

Epilimnion

2000 Existing Conditions 100 25.2 5.8 294 0.006 0.012 0.017 0.017 1.17

No Action 100 25.2 5.7 289 .006 .017 .016 .005 1.11

Percent change 0% –1.7% –.1.7% 0% 42% –.5.9% –71% –5.1%

2001 Existing Conditions 100 24.5 5.0 237 .007 .016 .017 .005 .94

No Action 100 24.6 5.0 238 .006 .016 .017 .006 .97

Percent change .4% 0% .4% –14% 0% 0% 20% 3.2%

2002 Existing Conditions 100 24.5 5.5 275 .011 .028 .018 <.001 1.08

No Action 100 24.6 5.5 280 .013 .030 .019 <.001 .97

Percent change .4% 0% 1.8% 18% 7.1% 5.6% NA –.10%

Hypolimnion

2000 Existing Conditions 100 18.3 <.1 296 .016 .009 .020 6.49 .82

No Action 100 17.7 <.1 290 .015 .009 .019 5.87 .80

Percent change –3.3% NA –2.0% –.6.3% 0% –.5.0% –.9.6% –.2.4%

2001 Existing Conditions 100 18.9 <.1 238 .016 .014 .022 5.65 .14

No Action 100 18.9 <.1 238 .015 .014 .022 6.98 .13

Percent change 0% NA 0% –.6.3% 0% 0% 24% –.7.1%

2002 Existing Conditions 100 15.5 <.1 249 .013 .007 .022 2.18 .25

No Action 100 14.8 .6 247 .010 .007 .022 .60 .25

Percent change –4.5% NA –.8% –.23% 0% 0% –.72% 0%

Table 5. Percent change between annual 85th percentile values for selected constituents and the annual 15th percentile values for 

dissolved oxygen concentrations in the epilimnion and hypolimnion at site 3B for the Existing Conditions scenario (water years 2000 

through 2002) as compared to the No Action (direct-effects analysis) scenario.

[N, nitrogen; P, phosphorus; °C, degrees Celsius; mg/L, milligrams per liter; μg/L, micrograms per liter; NA, not applicable; <, less than]

Water

year

Simulation

scenario

Percent of

annual

results

available

Water

temperature

(°C)

Dissolved

oxygen

(mg/L)

Dissolved

solids

(mg/L)

Dissolved

ammonia

as N

(mg/L)

Dissolved

nitrate

as N

(mg/L)

Total

phosphorus

as P

(mg/L)

Total

iron

(mg/L)

Chlorophyll-a

(μg/L)

Epilimnion

2000 Existing Conditions 100 23.8 6.1 296 0.002 0.034 0.017 0.098 1.89

No Action 100 24.0 6.1 291 .003 .030 .016 .070 1.87

Percent change .8% 0% –1.7% 50% –12% –5.9% –29% –1.1%

2001 Existing Conditions 100 23.3 5.9 243 .008 .063 .021 .181 1.21

No Action 100 23.2 5.9 247 .006 .064 .021 .187 1.34

Percent change –.4% 0% 1.6% –25% 1.6% 0% 3.3% 11%

2002 Existing Conditions 100 23.2 6.1 326 .010 .059 .027 .041 5.27

No Action 100 23.1 5.8 329 .009 .060 .027 .047 4.43

Percent change –.4% –4.9% .9% –10% 1.7% 0% 15% –16%

Hypolimnion

2000 Existing Conditions 100 23.1 4.8 299 .004 .032 .018 .498 1.50

No Action 100 23.3 4.7 294 .004 .031 .017 .445 1.40

Percent change .9% –2.1% –1.7% 0% –3.1% –5.6% –11% –6.7%

2001 Existing Conditions 100 23.3 5.9 243 .008 .063 .021 .181 1.21

No Action 100 22.4 5.0 252 .006 .058 .020 .733 1.16

Percent change –3.9% –15% 3.7% –25% –7.9% –4.8% 305% –4.1%

2002 Existing Conditions 100 23.0 5.9 326 .009 .047 .027 .047 4.92

No Action 100 22.8 5.6 330 .008 .047 .028 .054 3.85

Percent change –.9% –5.1% 1.2% –11% 0% 3.7% 15% –22%
Comparison of Results for Selected Simulation Scenarios 19

two to three times higher than what were observed in the 

epilimnion at site 7B. At the upstream site in the reservoir 

(3B), similar annual dissolved ammonia concentrations 

were observed between the two scenarios and between the 

epilimnion and the hypolimnion (table 2).

Dissolved Nitrate

The annual median dissolved nitrate concentrations 

(as N) in the epilimnion and the hypolimnion at site 7B 

near the dam generally were similar between the Existing 

Conditions and the No Action scenarios (fig. 14). The 

difference in concentrations between the two scenarios 

for any simulated year was no more than 0.001 mg/L at 

site 7B (table 2). It should be noted that dissolved nitrite 

plus nitrate concentrations were input as a surrogate for 

nitrate; nitrate is the predominant fraction of the nitrite plus 

nitrate analysis in Pueblo Reservoir (Edelmann, 1989). At 

the upstream site (3B), the percent change from the Existing 

Conditions scenario in the epilimnion and hypolimnion was 

within 11 percent for all simulated years but did not exceed 

0.003 mg/L (table 3).

The water-quality standard for dissolved nitrate is 

10 mg/L as N, as set by the Colorado Department of Public 

Health and Environment (Colorado Department of Public 

Health and Environment, 2007). The standard was not 

exceeded by any of the annual median or annual 85th percentile values for either simulation scenario for any simulated 

year in either the epilimnion or hypolimnion (tables 2–5).

Figure 13. Annual median dissolved ammonia concentrations 

in the epilimnion and hypolimnion at site 7B for the Existing 

Conditions (water years 2000 through 2002) and No Action (directeffects analysis) scenarios.

Figure 12. Annual median dissolved solids concentrations in 

the epilimnion and hypolimnion at site 7B for the Existing Conditions 

(water years 2000 through 2002) and No Action (direct-effects 

analysis) scenarios.

Water year

2000 2001 2002

Water year

2000 2001 2002

0

100

200

300

400

500

Dissolved solids, in milligrams per liter

0.00

0.01

0.02

0.03

Dissolved ammonia, in milligrams per liter as nitrogen

Existing Conditions—Epilimnion

No Action—Epilimnion

Existing Conditions—Hypolimnion

No Action—Hypolimnion

EXPLANATION

Existing Conditions—Epilimnion

No Action—Epilimnion

Existing Conditions—Hypolimnion

No Action—Hypolimnion

EXPLANATION

Total Phosphorus

Annual median total phosphorus concentrations in the 

epilimnion and hypolimnion of Pueblo Reservoir generally 

were similar between the two simulation scenarios (fig. 15). 

At site 7B and site 3B, the change in concentration between 

the epilimnion and hypolimnion from the Existing Conditions 

scenario was only 0.001 mg/L for all of the water years 

(tables 2 and 3). No specific water-quality standards were 

applicable for comparison to the simulated results.

Total Iron

The annual median total iron concentrations for the 

Existing Conditions and No Action scenarios in the epilimnion 

at site 7B were typically at the minimum calculation threshold 

(0.001 mg/L; Galloway and others, 2008) for the Pueblo 

Reservoir model (fig. 16); little or no total iron was simulated in 

the epilimnion of the reservoir at this site. Only slightly larger 

annual median concentrations of total iron were simulated in the 

hypolimnion at site 7B, and there were little differences in the 

results between the two simulation scenarios for any of the three 

simulated years (table 2). The largest simulated annual median 

total iron concentration in the hypolimnion was 0.005 mg/L. 

Temporally, larger total iron concentrations were simulated in 

the hypolimnion during the summer months at 7B (fig. 17). 

Total iron concentrations increased in the hypolimnion during 

the same relative time when anoxic conditions were simulated 

at depth at site 7B near the dam.
20 Simulated Effects of Proposed Arkansas Valley Conduit, Pueblo Reservoir, Southeastern Colorado

Figure 14. Annual median dissolved nitrate concentrations in 

the epilimnion and hypolimnion at site 7B for the Existing Conditions 

(water years 2000 through 2002) and No Action (direct-effects 

analysis) scenarios.

Figure 15. Annual median total phosphorus concentrations in 

the epilimnion and hypolimnion at site 7B for the Existing Conditions 

(water years 2000 through 2002) and No Action (direct-effects 

analysis) scenarios.

Overall, the concentrations of total iron at site 3B were 

substantially larger than those simulated at the downstream 

site (tables 2 and 3) likely from suspension of particulate 

material at this more riverine site. Comparisons between the 

Existing Conditions and No Action scenarios in the epilimnion 

and hypolimnion at site 3B indicated that there was little 

difference between the results for the simulations during any 

water year. Similar to site 7B, larger concentrations were 

observed in the hypolimnion than in the epilimnion at site 3B.

The State chronic surface-water water-quality standard 

for total iron in Pueblo Reservoir is set at 1 mg/L (Colorado 

Department of Public Health and Environment, 2007). No 

calculated annual median concentration in the epilimnion or 

in the hypolimnion at sites 7B or 3B exceeded the standard 

for either simulated scenario (tables 2 and 3). Caution should 

be used when applying the simulated total iron concentrations 

to water-quality standards because the absolute mean error 

reported for the calibrated Pueblo Reservoir model was 1.48 

mg/L (Galloway and others, 2008).

Algal Groups and Chlorophyll-a

The composition and dynamics of the algal community 

in a reservoir can be highly complex, and modeling is a 

simplification of what actually occurs in a reservoir. In the 

Pueblo Reservoir model, diverse-species composition was 

generalized into four main groups to reduce the complexity of 

the modeling effort. The four algal groups simulated as part of 

Water year

2000 2001 2002

Water year

2000 2001 2002 0.00

0.01

0.02

Dissolved nitrate, in milligrams per liter as nitrogen

0.00

0.02

0.04

0.06

0.08

0.10

Total phosphorus, in milligrams per liter

Existing Conditions—Epilimnion

No Action—Epilimnion

Existing Conditions—Hypolimnion

No Action—Hypolimnion

EXPLANATION

Existing Conditions—Epilimnion

No Action—Epilimnion

Existing Conditions—Hypolimnion

No Action—Hypolimnion

EXPLANATION

less than valueless than valueless than valueless than valueless than valueless than valueless than valueless than value

2000 2001 2002

Water year

0.00

0.01

0.02

Total iron, in milligrams per liter

Existing Conditions—Epilimnion

No Action—Epilimnion

Existing Conditions—Hypolimnion

No Action—Hypolimnion

EXPLANATION

Figure 16. Annual median total iron concentrations in the 

epilimnion and hypolimnion at site 7B for the Existing Conditions 

(water years 2000 through 2002) and No Action (direct-effects 

analysis) scenarios.
Comparison of Results for Selected Simulation Scenarios 21

O N D J F M A M J J A S O N D J F M A M J J A S O N D J F M A M J J A S

Water year 2001

(average year)

Water year 2002

(dry year)

Water year 2000

(wet year)

0

10

20

30

40

50

Total iron, in milligrams per liter

No Action—Direct effects

Existing Conditions

EXPLANATION

Figure 17. Comparison of total iron concenrations in the hypolimnion at site 7B in Pueblo Reservoir 

for the Existing Conditions (water years 2000 through 2002) and No Action (direct-effects analysis) 

scenarios.

this report included blue-green algae (cyanobacteria), green 

algae, diatoms, and flagellates. Algal growth in the Pueblo 

Reservoir model was affected by temperature, light, and the 

availability of nutrients. Decreases in algal population in the 

model generally are due to mortality, respiration, and settling 

to the bottom sediments (Cole and Wells, 2003).

The simulated distribution of algal populations was 

highly variable in Pueblo Reservoir from WY 2000 through 

WY 2002 (figs. 18 and 19). The largest algal biomass in 

Pueblo Reservoir generally occurred from May through 

September when blue-green and green algae were the 

dominant algal groups at site 7B near the dam of the reservoir. The smallest algal biomass generally occurred from 

November through March when diatoms and flagellates were 

the dominant groups. Seasonal differences in algal communities were the result of nutrient and light availability, 

and differences in water temperature. Generally, simulated 

biomass concentrations of green algae, diatoms, and flagellates were less than 0.5 mg/L in the epilimnion and hypolimnion at sites 7B and 3B for either of the two simulation 

scenarios (Existing Conditions and No Action). Blue-green 

algae biomass concentrations in the epilimnion at 7B and 

3B and in the hypolimnion at 3B could be about 2 to 3 times 

these concentrations.

Generally, algae biomass concentrations were similar for 

the Existing Conditions and the No Action scenarios at site 7B 

in the epilimnion for the simulated period (WY 2000 through 

WY 2002) (fig. 18). The increase in blue-green algae biomass 

concentrations occurred each year during May and June 

when water temperature, light, and nutrient availability were 

conducive for increased growth in surface waters. Maximum 

biomass concentrations of blue-green algae in the epilimnion 

were less than 1 mg/L for the two scenarios at site 7B. In the 

hypolimnion, there was no marked difference between the two 

simulation scenarios (fig. 18). Overall, biomass concentrations 

were less than 0.4 mg/L for any of the algal types at this site.

At site 3B, concentrations of blue-green algae, green 

algae, diatoms, and flagellates generally were similar between 

scenarios at any depth (fig. 19). Diatoms were the predominant 

algal type at this upstream site on Pueblo Reservoir in 

WY 2000 but transitioned to blue-green algae in WY 2002.

Harmful algal blooms in freshwater, particularly from 

blue-green algae, can occur when water use is impaired due 

to excessive accumulations of nutrients. This occurrence is 

affected by a complex set of physical, chemical, biological, 

hydrological, and meteorological conditions making it 

difficult to isolate specific causative environmental factors 

(Graham, 2006). Potential impairments include reduction in 
22 Simulated Effects of Proposed Arkansas Valley Conduit, Pueblo Reservoir, Southeastern Colorado

Figure 18. Relation between various algal groups in the epilimnion and hypolimnion at site 7B for the Existing Conditions (water years 

2000 through 2002) and No Action (direct-effects analysis) scenarios.

Epilimnion

Existing Conditions Scenario No Action Scenario

Epilimnion

Hypolimnion Hypolimnion

O N D J F M A M J J A S O N D J F M A M J J A S O N D J F M A M J J A S

Water year 2000 Water year 2001 Water year 2002

O N D J F M A M J J A S O N D J F M A M J J A S O N D J F M A M J J A S

Water year 2000 Water year 2001 Water year 2002

O N D J F M A M J J A S O N D J F M A M J J A S O N D J F M A M J J A S

Water year 2000 Water year 2001 Water year 2002

O N D J F M A M J J A S O N D J F M A M J J A S O N D J F M A M J J A S

Water year 2000 Water year 2001 Water year 2002

0.0

0.2

0.4

0.6

0.8

1.0

Algal biomass, in milligrams per liter as carbon

0.0

0.2

0.4

0.6

0.8

1.0

Algal biomass, in milligrams per liter as carbon

0.0

0.2

0.4

0.6

0.8

1.0

Algal biomass, in milligrams per liter as carbon

0.0

0.2

0.4

0.6

0.8

1.0

Algal biomass, in milligrams per liter as carbon

Blue-green algae

Green algae

Diatoms

Flagellates

EXPLANATION
Comparison of Results for Selected Simulation Scenarios 23

Figure 19. Relation between various algal groups in the epilimnion and hypolimnion at site 3B for the Existing Conditions (water years 

2000 through 2002) and No Action (direct-effects analysis) scenarios.

Epilimnion

Existing Conditions Scenario No Action Scenario

Epilimnion

Hypolimnion Hypolimnion

O N D J F M A M J J A S O N D J F M A M J J A S O N D J F M A M J J A S

Water year 2000 Water year 2001 Water year 2002

O N D J F M A M J J A S O N D J F M A M J J A S O N D J F M A M J J A S

Water year 2000 Water year 2001 Water year 2002

O N D J F M A M J J A S O N D J F M A M J J A S O N D J F M A M J J A S

Water year 2000 Water year 2001 Water year 2002

O N D J F M A M J J A S O N D J F M A M J J A S O N D J F M A M J J A S

Water year 2000 Water year 2001 Water year 2002

Algal biomass, in milligrams per liter as carbonAlgal biomass, in milligrams per liter as carbon

Algal biomass, in milligrams per liter as carbonAlgal biomass, in milligrams per liter as carbon

0.0

0.5

1.0

1.5

2.0

0.0

0.5

1.0

1.5

2.0

0.0

0.5

1.0

1.5

2.0

0.0

0.5

1.0

1.5

2.0

Blue-green algae

Green algae

Diatoms

Flagellates

EXPLANATION
24 Simulated Effects of Proposed Arkansas Valley Conduit, Pueblo Reservoir, Southeastern Colorado

Figure 20. Annual median chlorophyll-a concentrations in the 

epilimnion and hypolimnion at site 7B for the Existing Conditions 

(water years 2000 through 2002) and No Action (direct-effects 

analysis) scenarios.

Water year

2000 2001 2002

0.0

0.2

0.4

0.6

0.8

1.0

Chloropyll-a, in micrograms per liter

Existing Conditions—Epilimnion

No Action—Epilimnion

Existing Conditions—Hypolimnion

No Action—Hypolimnion

EXPLANATION

water quality, accumulation of malodorous scum in beach 

areas, algal production of toxins potent enough to poison 

both aquatic and terrestrial organisms, and algal production 

of taste-and-odor compounds that cause unpalatable drinking 

water. Simulated algae biomass concentrations associated with 

Existing Conditions and No Action scenarios would not be 

expected to pose any health issues or produce any taste-andodor problems in Pueblo Reservoir (Graham, 2006).

Chlorophyll-a is the primary pigment in plants 

responsible for photosynthesis and can be used as a general 

indicator of primary production and the quantity of algae 

present in a water body. Because chlorophyll-a concentrations can be affected by various environmental and nutritional factors without affecting algal biomass (Britton and 

Greeson, 1989), chlorophyll-a measurements are considered 

to provide only an approximation of primary production and 

algal biomass. Nevertheless, a widely used measure of algal 

and blue-green algal biomass is the chlorophyll-a concentration. Peak values of chlorophyll-a for an oligotrophic lake 

are about 1 to 10 micrograms per liter (μg/L). Concentrations in a eutrophic lake can reach 300 μg/L (Chorus and 

Bartram, 1999). For protection from health outcomes not due 

to cyanotoxins, but due to the irritative or allergenic effects of 

other cyanobacterial compounds, a guideline level of 10 μg/L

of chlorophyll-a (under conditions of cyanobacterial dominance) can be derived from the prospective epidemiological 

study by Pilotto and others (1997). In temperate regions of 

the United States, the occurrence of cyanobacteria and the 

potential presence of microcystin are most common during 

late summer and early autumn and may last 2 to 4 months. 

Blooms of microcystis (a toxin-forming cyanobacteria) typically are found in lakes with average summer chlorophyll-a

concentrations of 20 to 50 μg/L and a secchi depth of 3 to 6 ft 

(Chorus and Bartram, 1999). Secchi depth is a measurement 

of the clarity of a reservoir defined as the depth at which an 

8-inch diameter black and white disk is no longer visible in 

the water column.

Annual median chlorophyll-a concentrations in the 

epilimnion and hypolimnion near the dam (site 7B) were 

similar for the No Action scenario and the Existing Conditions 

scenario (fig. 20, table 2). In the epilimnion, the differences 

in median concentrations between the two scenarios differed 

by no more than 0.02 μg/L over the three simulated years; the 

percent change from the Existing Conditions scenario was 

less than 4 percent for all simulated years (table 2). In the 

hypolimnion, annual median concentrations differed by no 

more than 0.02 μg/L over the three years. Concentrations were 

consistently larger in the epilimnion where photosynthesis was 

greater than in the hypolimnion.

Annual median chlorophyll-a concentrations in the 

epilimnion and hypolimnion at site 3B were similar between 

the No Action and Existing Conditions scenarios (table 3). 

Generally, concentrations differed by no more than 0.1 μg/L 

at any depth.

Comparison of No Action Scenario 

and Other Simulation Scenarios

The following comparisons were made between the No 

Action scenario and each of the other scenarios as described 

in the previous section entitled “Description of Simulation 

Scenarios.” Specifically, the No Action scenario was compared individually to the Comanche South, Joint Use Pipeline 

North, and Master Contract Only scenarios. Comparisons were 

made to describe changes in the annual median, 85th percentile, 

or 15th percentile concentration between the No Action scenario 

and each of the other three simulation scenarios. Comparisons 

between scenario results in this section of the report will be similar to those described in the section “Comparison of Existing 

Conditions Scenario and No Action Scenario.”

Water-Surface Elevations

Simulated water-surface elevations in Pueblo Reservoir 

generally were similar between the No Action scenario and 

each of the other three simulation scenarios (fig. 21). However, 

differences in reservoir water-surface elevation (storage) 

among the four scenarios did increase each year. Reservoir 

storage for the Master Contract Only and Comanche South 

scenarios was greater than the No Action scenario, whereas, 
Comparison of Results for Selected Simulation Scenarios 25

storage for the Joint Use Pipeline North was less. Overall, 

there was a temporal decrease in water-surface elevations from 

WY 2000 through WY 2002 for all the simulated scenarios. At 

the peak annual storage, the difference between the surfacewater elevation for the No Action scenario and any other 

comparable simulated elevation was no more than 1 ft in 

WY 2000, 3 ft in WY 2001, and 6 ft in WY 2002. Typically, 

maximum storage occurred in late March of each year as 

winter storage was nearly complete and releases of water to 

downstream irrigators had yet to start.

Water Temperature

Comparisons of the results between the No Action 

scenario and each of the other three simulation scenarios 

for water temperature indicated that the simulated scenarios 

generally provided similar results (fig. 22). At site 7B, the 

percent change from the No Action scenario in the epilimnion 

was less than 5 percent for all simulated years (table 6). 

Water temperatures in the hypolimnion were similar but more 

variable between the simulation scenarios. In WY 2000, there 

were no differences in the simulated annual hypolimnetic 

water temperature between the No Action scenario and the 

Figure 21. Comparison of water-surface elevations in Pueblo Reservoir for the No Action, Comanche 

South, Joint Use Pipeline North, and Master Contract Only scenarios (direct-effects analyses). Datum is 

North American Vertical Datum of 1988 (NAVD 88).

O N D J F M A M J J A S O N D J F M A M J J A S O N D J F M A M J J A S

Water year 2001

(average year)

Water year 2002

(dry year)

Water year 2000

(wet year)

4,790

4,823

4,856

4,889

4,922

Reservoir water-surface elevation, in feet

1,460

1,470

1,480

1,490

1,500

Reservoir water-surface elevation, in meters

No Action—Direct effects

Comanche South—Direct effects

Joint Use Pipeline North—Direct effects

Master Contract Only—Direct effects

EXPLANATION

other three modeled simulations. In WY 2001, the difference 

in annual median water temperature between the No Action 

and the Master Contract Only scenarios was 1 °C (11 percent) 

increasing to 1.7 °C (18 percent) in WY 2002. The water 

temperature associated with the Master Contract Only scenario 

was higher during both years. Generally, temperatures in 

the hypolimnion were 4 °C to 5 °C lower than those in 

the epilimnion. Annual median water temperatures in the 

epilimnion and the hypolimnion at site 3B between scenarios 

also were similar; the differences were within 10 percent when 

compared to the No Action scenario (table 7).

Dissolved Oxygen

Comparisons between the No Action scenario and the 

three other scenarios indicated that the annual median values 

of simulated DO concentrations in the epilimnion at site 

7B generally were similar (fig. 23). Typically, the percent 

change from the No Action scenario was within 2 percent in 

the epilimnion for the simulated scenarios for any simulated 

year at site 7B (table 6). The percent change from the No 

Action scenario in the hypolimnion was less than 6 percent 

for the simulated scenarios for any simulated year (table 6). 
26 Simulated Effects of Proposed Arkansas Valley Conduit, Pueblo Reservoir, Southeastern Colorado

Figure 22. Annual median water temperature in the epilimnion and hypolimnion at site 7B for the No Action, Comanche South, Joint 

Use Pipeline North, and Master Contract Only scenarios (direct-effects analyses).

Epilimnion Hypolimnion

2000 2001 2002

Water year

2000 2001 2002

Water year

0

5

10

15

20

Water temperature, in degrees Celsius

0

5

10

15

20

Water temperature, in degrees Celsius

No Action 

EXPLANATION

Comanche South

Joint Use Pipeline North

Master Contract Only

Comparisons of DO concentrations in the epilimnion and 

hypolimnion at site 3B generally showed similar results for 

WY 2000 through WY 2002 (table 7). The Joint Use Pipeline 

North scenario had a median concentration in 2002 that was 

substantially higher than the No Action (18 percent), however, 

only 83 percent of data were available to compute this 

statistic; the Joint Use Pipeline North scenario was the only 

scenario that “dried up” during model simulations.

Differences between the annual 15th percentile DO 

concentrations in the epilimnion at site 7B were similar to the 

differences observed for the annual median values at this depth. 

The results from the No Action scenario differed by no more 

than 2 percent (0.1 mg/L) from any of the other three compared 

scenarios (table 8). Overall, the annual 15th percentile values in 

the epilimnion at site 7B were at least 4.9 mg/L for any of the 

simulation scenarios.

Seasonal periods of anoxic conditions in Pueblo Reservoir 

have been documented by Edelmann (1989). Simulated results 

for the No Action scenario show depleted concentrations of 

DO during the summer months in the hypolimnion at site 7B 

(fig. 6). Simulated results for the Comanche South, Joint Use 

Pipeline North, and Master Contract Only scenarios also show 

similar results (fig. 7). The 15th percentile concentration was 

1.6 mg/L or less in the hypolimnion for all of these scenarios 

(table 8).

The minimum DO concentration suitable to meet the DO 

water-quality standard in Pueblo Reservoir (measured in the 

epilimnion) was 6.0 mg/L (Colorado Department of Public 

Health and Environment, 2007). The standard is compared 

to the 15th percentile of the data. The standard value was 

not always attained when compared to the simulated annual 

15th percentile value in the epilimnion at sites 7B and 3B 

(tables 8 and 9). Caution should be used when comparing 

these results to the water-quality standard because the absolute 

mean error of the DO calibration for the Pueblo Reservoir 

model was 1.42 mg/L at site 7B (Galloway and others, 2008).

Dissolved Solids

Comparisons of simulated dissolved solids concentrations indicated that the annual medians were relatively similar 

between the No Action and the Comanche South, Joint Use 

Pipeline North, and Master Contract Only scenarios in the epilimnion and hypolimnion at site 7B (near-dam site) (fig. 24). 

Simulated results for the No Action scenario were no more 

than 3 percent larger than the annual medians for the other 

three scenarios during WY 2000 through WY 2002 (table 6). 

The results were similar for both the epilimnion and the hypolimnion. For the most part, similar results also were observed 

in the epilimnion and hypolimnion at site 3B (table 7).

No water-quality standard for dissolved solids exists for 

Pueblo Reservoir. However, a guideline does exist to assist 

managers of public water systems in managing their drinking water for aesthetic considerations, such as taste, color, 

and odor. The secondary maximum contaminant level is set 

at 500 mg/L (U.S. Environmental Protection Agency, 1992). 

The largest annual median dissolved solids concentration was 

reported at site 3B (284 mg/L) in WY 2000 (tables 6 and 7). 

No annual 85th percentile value exceeded the recommended 

guideline for any of the simulated scenarios at sites 7B and 3B 

(tables 8 and 9).
Comparison of Results for Selected Simulation Scenarios 27

Table 6. Percent change between annual median values for selected constituents in the epilimnion and hypolimnion at site 7B for 

direct-effects analyses for the Comanche South, Joint-Use Pipeline North, and Master Contract Only scenarios as compared to the 

No Action scenario.

[N, nitrogen; P, phosphorus; °C, degrees Celsius; mg/L, milligrams per liter; μg/L, micrograms per liter; NA, not applicable; <, less than]

Water

year

Simulation

scenario 

Percent of

annual

results

available

Water

temperature

(°C)

Dissolved

oxygen

(mg/L)

Dissolved

solids

(mg/L)

Dissolved

ammonia

as N

(mg/L)

Dissolved

nitrate

as N

(mg/L)

Total

phosphorus

as P

(mg/L)

Total

iron

(mg/L)

Chlorophyll-a

(μg/L)

Epilimnion

2000

No Action 100 14.5 7.9 281 0.003 0.006 0.014 <0.001 0.53

Comanche South 100 14.6 7.9 280 .003 .006 .014 <.001 .54

Percent change .7% 0% –.4% 0% 0% 0% NA 1.9%

No Action 100 14.5 7.9 281 .003 .006 .014 <.001 .53

Joint Use Pipeline North 100 14.6 7.8 281 .003 .006 .014 <.001 .53

Percent change .7% –1.3% 0% 0% 0% 0% NA 0%

No Action 100 14.5 7.9 281 .003 .006 .014 <.001 .53

Master Contract Only 100 14.6 7.8 278 .003 .006 .014 <.001 .52

Percent change .7% –1.3% –1.1% 0% 0% 0% NA –1.9%

Hypolimnion

2000

No Action 100 10.5 7.6 281 .009 .005 .015 .005 .12

Comanche South 100 10.5 7.6 281 .009 .005 .015 .005 .12

Percent change 0% 0% 0% 0% 0% 0% 0% 0%

No Action 100 10.5 7.6 281 .009 .005 .015 .005 .12

Joint Use Pipeline North 100 10.5 7.6 281 .010 .006 .015 .005 .12

Percent change 0% 0% 0% 11% 20% 0% 0% 0%

No Action 100 10.5 7.6 281 .009 .005 .015 .005 .12

Master Contract Only 100 10.5 7.6 279 .009 .005 .015 .005 .12

Percent change 0% 0% –.7% 0% 0% 0% 0% 0%

Epilimnion

2001

No Action 100 14.6 7.8 231 .003 .009 .017 <.001 .25

Comanche South 100 14.5 7.9 227 .002 .009 .016 <.001 .25

Percent change –.7% 1.3% –1.7% –33% 0% –5.9% NA 0%

No Action 100 14.6 7.8 231 .003 .009 .017 <.001 .25

Joint Use Pipeline North 100 14.7 7.9 233 .002 .008 .016 <.001 .26

Percent change .7% 1.3% .9% –33% –11% –5.9% NA 4.0%

No Action 100 14.6 7.8 231 .003 .009 .017 <.001 .25

Master Contract Only 100 14.0 7.8 224 .003 .012 .017 <.001 .26

Percent change –4.1% 0% –3.0% 0% 33% 0% NA 4.0%

Hypolimnion

2001

No Action 100 9.3 7.7 234 .007 .009 .018 .003 .05

Comanche South 100 10.2 7.5 231 .006 .009 .017 .003 .05

Percent change 9.7% –2.6% –1.3% –14% 0% –5.6% 0% 0%

No Action 100 9.3 7.7 234 .007 .009 .018 .003 .05

Joint Use Pipeline North 100 9.4 7.7 235 .007 .007 .017 .003 .06

Percent change 1.1% 0% .4% 0% –22% –5.6% 0% 20%

No Action 100 9.3 7.7 234 .007 .009 .018 .003 .05

Master Contract Only 100 10.3 7.5 228 .006 .008 .018 .003 .04

Percent change 11% –2.6% –2.6% –14% –11% 0% 0% –20%

Epilimnion

2002

No Action 100 14.4 8.0 235 .004 .007 .017 <.001 .30

Comanche South 100 14.5 8.0 230 .003 .009 .017 <.001 .26

Percent change .7% 0% –2.1% –25% 29% 0% NA –13%

No Action 100 14.4 8.0 235 .004 .007 .017 <.001 .30

Joint Use Pipeline North 100 14.3 8.1 238 .003 .008 .018 <.001 .26

Percent change –.7% 1.3% 1.3% –25% 14% 5.9% NA –13%

No Action 100 14.4 8.0 235 .004 .007 .017 <.001 .30

Master Contract Only 100 14.2 8.1 228 .003 .009 .017 <.001 .22

Percent change –1.4% 1.3% –3.0% –25% 29% 0% NA –27%

Hypolimnion

2002

No Action 100 9.6 7.8 235 .006 .005 .018 <.001 .07

Comanche South 100 9.0 8.1 230 .006 .005 .017 <.001 .07

Percent change –6.3% 3.8% –2.1% 0% 0% –5.6% NA 0%

No Action 100 9.6 7.8 235 .006 .005 .018 <.001 .07

Joint Use Pipeline North 100 9.8 7.9 237 .006 .006 .018 <.001 .06

Percent change 2.1% 1.3% .9% 0% 20% 0% NA –14%

No Action 100 9.6 7.8 235 .006 .005 .018 <.001 .07

Master Contract Only 100 11.3 7.4 228 .006 .005 .018 <.001 .07

Percent change 18% –5.1% –3.0% 0% 0% 0% NA 0%
28 Simulated Effects of Proposed Arkansas Valley Conduit, Pueblo Reservoir, Southeastern Colorado

Table 7. Percent change between annual median values for selected constituents in the epilimnion and hypolimnion at site 3B for directeffects analyses for the Comanche South, Joint Use Pipeline North, and Master Contract Only scenarios as compared to the No Action scenario.

[N, nitrogen; P, phosphorus; °C, degrees Celsius; mg/L, milligrams per liter; μg/L, micrograms per liter; NA, not applicable; <, less than]

Water

year

Simulation

scenario

Percent of

annual

results

available

Water

temperature

(°C)

Dissolved

oxygen

(mg/L)

Dissolved

solids

(mg/L)

Dissolved

ammonia

as N

(mg/L)

Dissolved

nitrate

as N

(mg/L)

Total

phosphorus

as P

(mg/L)

Total

iron

(mg/L)

Chlorophyll-a

(μg/L)

Epilimnion

2000

No Action 100 14.0 7.9 282 <0.001 0.005 0.015 0.010 0.91

Comanche South 100 14.0 7.9 284 <.001 .004 .015 .009 .90

Percent change 0% 0% .7% 0% –20% 0% –10% –1.1%

No Action 100 14.0 7.9 282 <.001 .005 .015 .010 .91

Joint Use Pipeline North 100 14.0 7.9 284 <.001 .005 .015 .011 1.02

Percent change 0% 0% .7% NA 0% 0% 10% 12%

No Action 100 14.0 7.9 282 <.001 .005 .015 .010 .91

Master Contract Only 100 14.0 7.8 282 <.001 .004 .015 .007 .87

Percent change 0% –1.3% 0% NA –20% 0% –30% –4.4%

Hypolimnion

2000

No Action 100 12.0 7.8 282 .002 .012 .016 .031 .70

Comanche South 100 12.1 7.8 283 .002 .012 .016 .031 .69

Percent change .8% 0% .4% 0% 0% 0% 0% –1.4%

No Action 100 12.0 7.8 282 .002 .012 .016 .031 .70

Joint Use Pipeline North 100 12.0 7.8 283 .002 .012 .016 .034 .72

Percent change 0% 0% .4% 0% 0% 0% 9.7% 2.9%

No Action 100 12.0 7.8 282 .002 .012 .016 .031 .70

Master Contract Only 100 12.1 7.8 281 .002 .011 .016 .030 .71

Percent change .8% 0% –.4% 0% –8.3% 0% –3.2% 1.4%

Epilimnion

2001

No Action 100 13.9 7.8 235 .002 .017 .018 .009 .75

Comanche South 100 13.8 7.7 230 .002 .014 .017 .006 .71

Percent change –.7% –1.3% –2.1% 0% –18% –5.6% –33% –5.3%

No Action 100 13.9 7.8 235 .002 .017 .018 .75

Joint Use Pipeline North 100 13.4 8.0 239 .003 .026 .019 .014 .64

Percent change –3.6% 2.6% 1.7% 50% 53% 5.6% 56% –15%

No Action 100 13.9 7.8 235 .002 .017 .018 .009 .75

Master Contract Only 100 13.9 7.7 227 .002 .016 .017 .006 .73

Percent change 0% –1.3% –3.4% 0% –5.9% –5.6% –33% –2.7%

Hypolimnion

2001

No Action 100 11.2 7.6 239 .003 .033 .019 .027 .51

Comanche South 100 10.9 7.7 235 .003 .027 .018 .027 .53

Percent change –2.7% 1.3% –1.7% 0% –18% –5.3% 0% 3.9%

No Action 100 11.2 7.6 239 .003 .033 .019 .027 .51

Joint Use Pipeline North 100 11.1 7.9 242 .004 .035 .019 .035 .52

Percent change –.9% 3.9% 1.3% 33% 6.1% 0% 30% 2%

No Action 100 11.2 7.6 239 .003 .033 .019 .027 .51

Master Contract Only 100 11.0 7.6 233 .003 .029 .018 .024 .50

Percent change –1.8% 0% –2.5% 0% –12% –5.3% –11% –2.0%

Epilimnion

2002

No Action 100 13.4 7.9 260 .003 .008 .023 .014 1.29

Comanche South 100 14.3 7.9 258 .003 .009 .022 .010 1.19

Percent change 6.7% 0% -.8% 0% 12% –4.3% –29% –7.8%

No Action 100 13.4 7.9 260 .003 .008 .023 .014 1.29

Joint Use Pipeline North 100 12.2 8.1 282 .009 .037 .024 .032 .64

Percent change –9.0% 2.5% 8.5% 200% 362% 4.3% 129% –50%

No Action 100 13.4 7.9 260 .003 .008 .023 .014 1.29

Master Contract Only 100 14.5 8.0 255 .003 .010 .022 .008 1.14

Percent change 8.2% 1.3% -1.9% 0% 25% –4.3% –43% –12%

Hypolimnion

2002

No Action 100 12.3 7.8 260 .003 .009 .022 .022 1.31

Comanche South 100 12.4 7.7 254 .003 .010 .021 .017 1.12

Percent change .8% –1.3% –2.3% 0% 11% –4.5% –23% –15%

No Action 100 12.3 7.8 260 .003 .009 .022 .022 1.31

Joint Use Pipeline North 831 11.4 9.2 261 .006 .034 .024 .033 .62

Percent change –7.3% 18% .4% 100% 278% 9.1% 50% –53%

No Action 100 12.3 7.8 260 .003 .009 .022 .022 1.31

Master Contract Only 100 12.1 7.6 249 .003 .010 .021 .015 .91

Percent change –1.6% –2.6% –4.2% 0% 11% –4.5% –32% –31%

1

Computational cells in the model “dry up” for this scenario due to drought conditions observed in 2002. Percent change calculated on less than 100 percent 

of the daily values for this water year.
Comparison of Results for Selected Simulation Scenarios 29

Figure 23. Annual median dissolved oxygen concentrations in the epilimnion and hypolimnion at site 7B for the No Action, Comanche 

South, Joint Use Pipeline North, and Master Contract Only scenarios (direct-effects analyses).

Major Nutrients

Nutrients are essential for plant growth. The main nutrients of concern in lakes and streams are nitrogen and phosphorus, which can be found in various forms. Factors such as 

water temperature, pH, dissolved oxygen concentrations, and 

biological activity influence the concentrations of nitrogen 

and phosphorus forms found in lakes and streams. Natural 

sources of nitrogen and phosphorus include precipitation and 

biogeochemical processes in the watershed. Anthropogenic 

sources of nutrients include but are not limited to urban runoff, 

domestic effluent, livestock waste, and erosion caused by 

development (Gaffey and others, 1996).

Dissolved Ammonia

The annual median dissolved ammonia (as nitrogen 

(N)) concentrations in the epilimnion and hypolimnion of 

Pueblo Reservoir at site 7B were similar between the No 

Action scenario and either the Comanche South, Joint Use 

Pipeline North, or Master Contract Only scenarios (fig. 25). 

Annual median simulated ammonia concentrations at either 

depth for the No Action scenario were within 0.001 mg/L of 

any of the other simulated scenarios (table 6). Annual median 

simulated ammonia concentrations in the epilimnion at site 

7B were less than annual median simulated concentrations in 

the hypolimnion.

Similar results were observed in the epilimnion and 

hypolimnion at site 3B in the upstream riverine section of 

the reservoir with the exception of comparisons to the Joint 

Use Pipeline North scenario in WY 2002 (table 7). Typically, 

differences from the No Action scenario did not exceed more 

than 0.001 mg/L for these comparisons. Larger differences in 

concentration, however, were observed between the No Action 

scenario and the Joint Use Pipeline North scenario at either 

of the two simulated depths; the differences were as large as 

0.006 mg/L.

Dissolved Nitrate

The annual median dissolved nitrate concentrations in 

the epilimnion of Pueblo Reservoir at site 7B generally were 

similar between the No Action scenario and any of the three 

simulated scenarios (fig. 26). Percent differences from the No 

Action scenario compared to the three simulated scenarios did 

not exceed 33 percent for these comparisons (table 6). Because 

of the relatively small concentrations of nitrate in Pueblo 

Reservoir, a change of 33 percent equated to an overall difference of only 0.003 mg/L as N between the annual median 

concentrations. Similar results were observed in the hypolimnion at site 7B (table 6).

Overall, observed results in the epilimnion and hypolimnion at site 3B were more variable with regard to the 

percent change in concentrations when compared to the No 

Action scenario (table 7). Whereas, concentrations varied by 

only 0.003 mg/L as N at site 7B, concentrations at site 3B 

varied from the No Action results by as much as 0.029 mg/L 

as N (Joint Use Pipeline North in WY 2002). Annual median 

nitrate concentrations at this upstream site also were larger 

than concentrations observed at site 7B near the dam. Denitrification processes and consumption from algal growth likely 

resulted in the decrease in concentration in the lower portion 

of the reservoir. A maximum annual median concentration of 

0.037 (Joint Use Pipeline North in WY 2002) was still small in 

terms of nitrate concentrations with public health implications. 

The water-quality standard for dissolved nitrate is 10 mg/L 

Epilimnion Hypolimnion

2000 2001 2002

Water year

2000 2001 2002

Water year

0

2

4

6

8

10

12

Dissolved oxygen, in milligrams per liter

0

2

4

6

8

10

12

Dissolved oxygen, in milligrams per liter

No Action 

EXPLANATION

Comanche South

Joint Use Pipeline North

Master Contract Only
30 Simulated Effects of Proposed Arkansas Valley Conduit, Pueblo Reservoir, Southeastern Colorado

Table 8. Percent change between annual 85th percentile values for selected constituents and comparisons of the annual 15th percentile 

values for dissolved oxygen concentrations in the epilimnion and hypolimnion at site 7B for direct-effects analyses for the Comanche 

South, Joint Use Pipeline North, and Master Contract Only scenarios as compared to the No Action scenario.

[N, nitrogen; P, phosphorus; °C, degrees Celsius; mg/L, milligrams per liter; μg/L, micrograms per liter; NA, not applicable; <, less than]

Water

year

Simulation

scenario

Percent of

annual

results

available

Water

temperature

(°C)

Dissolved

oxygen

(mg/L)

Dissolved

solids

(mg/L)

Dissolved

ammonia

as N

(mg/L)

Dissolved

nitrate

as N

(mg/L)

Total

phosphorus

as P

(mg/L)

Total

iron

(mg/L)

Chlorophyll-a

(μg/L)

Epilimnion

2000

No Action 100 25.2 5.7 289 0.006 0.017 0.016 0.005 1.11

Comanche South 100 25.2 5.7 290 .006 .017 .016 .005 1.08

Percent change 0% 0% 0.3% 0% 0% 0% 0% –2.7%

No Action 100 25.2 5.7 289 .006 .017 .016 .005 1.11

Joint Use Pipeline North 100 25.2 5.7 290 .006 .011 .016 .008 1.13

Percent change 0% 0% .3% 0% –35% 0% 60% 1.8%

No Action 100 25.2 5.7 289 .006 .017 .016 .005 1.11

Master Contract Only 100 25.2 5.7 288 .006 .017 .016 .005 1.07

Percent change 0% 0% –.3% 0% 0% 0% 0% –3.6%

Hypolimnion

2000

No Action 100 17.7 <.1 290 .015 .009 .019 5.87 .80

Comanche South 100 17.6 <.1 291 .015 .009 .019 6.71 .80

Percent change –.6% NA .3% 0% 0% 0% 14% 0%

No Action 100 17.7 <.1 290 .015 .009 .019 5.87 .80

Joint Use Pipeline North 100 18.3 <.1 292 .015 .009 .020 6.86 80

Percent change 3.4% NA .7% 0% 0% 5.3% 17% 0%

No Action 100 17.7 <.1 290 .015 .009 .019 5.87 .80

Master Contract Only 100 17.3 <.1 289 .015 .009 .019 6.40 .79

Percent change –2.3% NA –.3% 0% 0% 0% 9.0% –1.3%

Epilimnion

2001

No Action 100 24.6 5.0 238 .006 .016 .017 .006 .97

Comanche South 100 24.7 4.9 233 .007 .016 .017 .006 .90

Percent change .4% –2.0% –2.1% 17% 0% 0% 0% –7.2%

No Action 100 24.6 5.0 238 .006 .016 .017 .006 .97

Joint Use Pipeline North 100 24.8 5.0 241 .007 .015 .017 .003 .93

Percent change .8% 0% 1.3% 17% –6.3% 0% –50% –4.1%

No Action 100 24.6 5.0 238 .006 .016 .017 .006 .97

Master Contract Only 100 24.7 5.0 231 .007 .020 .017 .006 .89

Percent change .4% 0% –2.9% 17% 25% 0% 0% –8.2%

Hypolimnion

2001

No Action 100 18.9 <.1 238 .015 .014 .022 6.98 .13

Comanche South 100 18.7 <.1 234 .014 .014 .022 6.10 .13

Percent change –1.1% NA –1.7% –6.7% 0% 0% –13% 0%

No Action 100 18.9 <.1 238 .015 .014 .022 6.98 .13

Joint Use Pipeline North 100 19.3 <.1 240 .014 .012 .021 2.76 .17

Percent change 2.1% NA .8% –6.7% –14% –4.5% –60% 31%

No Action 100 18.9 <.1 238 .015 .014 .022 6.98 .13

Master Contract Only 100 18.5 <.1 233 .014 .016 .022 6.35 .10

Percent change –2.1% NA –2.1% –6.7% 14% 0% –9.0% –23%

Epilimnion

2002

No Action 100 24.6 5.5 280 .013 .030 .019 <.001 .97

Comanche South 100 24.5 5.5 277 .014 .034 .018 .002 .90

Percent change –.4% 0% –1.1% 7.7% 13% –5.3% NA –7.2%

No Action 100 24.6 5.5 280 .013 .030 .019 <.001 .97

Joint Use Pipeline North 100 24.6 5.5 282 .010 .013 .020 <.001 1.11

Percent change 0% 0% .7% –23% –57% 5.3% NA 14%

No Action 100 24.6 5.5 280 .013 .030 .019 <.001 .97

Master Contract Only 100 24.5 5.5 271 .013 .034 .018 <.001 .92

Percent change –.4% 0% –3.2% 0% 13% –5.3% NA –5.2%

Hypolimnion

2002

No Action 100 14.8 .6 247 .010 .007 .022 .605 .25

Comanche South 100 14.5 1.6 243 .009 .008 .021 .209 .23

Percent change –2.0% 167% –1.6% –10% 14% –4.5% –66% –8%

No Action 100 14.8 .6 247 .010 .007 .022 .605 .25

Joint Use Pipeline North 100 17.0 <.1 255 .014 .009 .024 2.38 .18

Percent change 15% NA 3.2% 40% 29% 9.1% 293% –28%

No Action 100 14.8 .6 247 .010 .007 .022 .605 .25

Master Contract Only 100 15.0 .2 242 .010 .008 .022 1.48 .18

Percent change 1.4% –67% –2.0% 0% 14% 0% 144% –28%
Comparison of Results for Selected Simulation Scenarios 31

Table 9. Percent change between annual 85th percentile values for selected constituents and comparisons of the annual 15th percentile 

values for dissolved oxygen concentrations in the epilimnion and hypolimnion at site 3B for direct-effects analyses for the Comanche 

South, Joint Use Pipeline North, and Master Contract Only scenarios as compared to the No Action scenario.

[N, nitrogen; P, phosphorus; °C, degrees Celsius; mg/L, milligrams per liter; μg/L, micrograms per liter; NA, not applicable; <, less than]

Water

year

Simulation

scenario

Percent of

annual

results

available

Water

temperature

(°C)

Dissolved

oxygen

(mg/L)

Dissolved

solids

(mg/L)

Dissolved

ammonia

as N

(mg/L)

Dissolved

nitrate

as N

(mg/L)

Total

phosphorus

as P

(mg/L)

Total

iron

(mg/L)

Chlorophyll-a

(μg/L)

Epilimnion

2000

No action 100 24.0 6.1 291 0.003 0.030 0.016 0.070 1.87

Comanche South 100 24.3 6.1 292 .003 .029 .016 .062 1.79

Percent change 1.3% 0% .3% 0% –3.3% 0% –11% –4.3%

No action 100 24.0 6.1 291 .003 .030 .016 .070 1.87

Joint Use Pipeline North 100 23.8 6.1 292 .002 .030 .017 .083 1.82

Percent change –.8% 0% .3% –33% 0% 6.2% 19% –2.7%

No action 100 24.0 6.1 291 .003 .030 .016 .070 1.87

Master Contract only 100 24.4 6.1 289 .003 .030 .016 .061 1.84

Percent change 1.7% 0% –.7% 0% 0% 0% –13% –1.6%

Hypolimnion

2000

No action 100 23.3 4.7 294 .004 .031 .017 .445 1.40

Comanche South 100 23.2 4.7 295 .004 .030 .017 .493 1.36

Percent change –.4% 0% .3% 0% –3.2% 0% 11% –2.9%

No action 100 23.3 4.7 294 .004 .031 .017 .445 1.40

Joint Use Pipeline North 100 22.7 4.8 296 .005 .035 .018 .541 1.60

Percent change –2.6% 2.1% .7% 25% 13% 5.9% 22% 14%

No action 100 23.3 4.7 294 .004 .031 .017 .445 1.40

Master Contract only 100 23.2 4.6 294 .004 .029 .017 .469 1.38

Percent change –.4% –2.1% 0% 0% –6.5% 0% 5.4% –1.4%

Epilimnion

2001

No action 100 23.2 5.9 247 .006 .064 .021 .187 1.34

Comanche South 100 23.6 6.0 242 .005 .056 .020 .092 1.21

Percent change 1.7% 1.7% –2.0% –17% –12% –4.8% –51% –9.7%

No action 100 23.2 5.9 247 .006 .064 .021 .187 1.34

Joint Use Pipeline North 100 22.4 5.5 258 .009 .073 .022 .373 1.15

Percent change –3.4% –6.8% 4.5% 50% 14% 4.8% 99% –14%

No action 100 23.2 5.9 247 .006 .064 .021 .187 1.34

Master Contract only 100 23.7 6.0 239 .006 .049 .020 .069 1.18

Percent change 2.2 % 1.7% –3.2% 0% –23% –4.8% –63% –12%

Hypolimnion

2001

No action 100 22.4 5.0 252 .006 .058 .020 .733 1.16

Comanche South 100 22.8 4.8 247 .005 .051 .020 .462 1.09

Percent change 1.8% –4.0% –2.0% –17% –12% 0% –37% –6.0%

No action 100 22.4 5.0 252 .006 .058 .020 .733 1.16

Joint Use Pipeline North 100 22.0 5.1 263 .008 .068 .021 .791 .80

Percent change –1.8% 2.0% 4.4% 33% 17% 5.0% 7.9% –31%

No Action 100 22.4 5.0 252 .006 .058 .020 .733 1.16

Master Contract only 100 22.8 4.8 244 .005 .051 .020 .498 1.03

Percent change 1.8% –4.0% –3.2% –17% –12% 0% –32% –11%

Epilimnion

2002

No Action 100 23.1 5.8 329 .009 .060 .027 .047 4.43

Comanche South 100 23.2 6.1 324 .009 .048 .026 .042 5.46

Percent change .4% 5.2% –1.5% 0% –20% –3.7% –11% 23%

No Action 100 23.1 5.8 329 .009 .060 .027 .047 4.43

Joint Use Pipeline North 100 22.5 5.4 336 .016 .073 .032 .175 1.94

Percent change –2.6% –6.9% 2.1% 78% 22% 18% 272% –56%

No Action 100 23.1 5.8 329 .009 .060 .027 .047 4.43

Master Contract Only 100 23.3 6.1 313 .009 .041 .024 .034 4.14

Percent change .9 % 5.2% –4.9% 0% –32% –11% –28% –6.5%

Hypolimnion

2002

No Action 100 22.8 5.6 330 .008 .047 .028 .054 3.85

Comanche South 100 23.0 5.9 324 .008 .033 .026 .054 5.24

Percent change .9% 5.4% –1.8% 0% –30% –7.1% 0% 36%

No Action 100 22.8 5.6 330 .008 .047 .028 .054 3.85

Joint Use Pipeline North 83 22.1 5.6 313 .014 .067 .027 .139 2.04

Percent change –3.1% 0% –5.2% 75% 43% –3.6% 157% –47%

No action 100 22.8 5.6 330 .008 .047 .028 .054 3.85

Master Contract only 100 23.1 5.6 315 .008 .035 .024 .035 4.02

Percent change 1.3% 0% –4.5% 0% –26% –14% –35% 4.4%
32 Simulated Effects of Proposed Arkansas Valley Conduit, Pueblo Reservoir, Southeastern Colorado

Figure 24. Annual median dissolved solids concentrations in the epilimnion and hypolimnion at site 7B for the No Action, Comanche 

South, Joint Use Pipeline North, and Master Contract Only scenarios (direct-effects analyses).

Figure 25. Annual median dissolved ammonia concentrations in the epilimnion and hypolimnion at site 7B for the No Action, Comanche 

South, Joint Use Pipeline North, and Master Contract Only scenarios (direct-effects analyses).

Epilimnion Hypolimnion

2000 2001 2002

Water year

2000 2001 2002

Water year

0

100

200

300

400

500

Dissolved solids, in milligrams per liter

0

100

200

300

400

500

Dissolved solids, in milligrams per liter

No Action 

EXPLANATION

Comanche South

Joint Use Pipeline North

Master Contract Only

Epilimnion Hypolimnion

2000 2001 2002

Water year

2000 2001 2002

Water year

0.000

0.005

0.010

0.015

0.020

Dissolved ammonia,

in milligrams per liter as nitrogen

Dissolved ammonia,

in milligrams per liter as nitrogen

0.000

0.005

0.010

0.015

0.020

No Action 

EXPLANATION

Comanche South

Joint Use Pipeline North

Master Contract Only
Comparison of Results for Selected Simulation Scenarios 33

Figure 26. Annual median dissolved nitrate concentrations in the epilimnion and hypolimnion at site 7B for the No Action, Comanche 

South, Joint Use Pipeline North, and Master Contract Only scenarios (direct-effects analyses).

Epilimnion Hypolimnion

2000 2001 2002

Water year

2000 2001 2002

Water year

0.000

0.005

0.010

0.015

0.020

Dissolved nitrate,

in milligrams per liter as nitrogen

0.000

0.005

0.010

0.015

0.020

Dissolved nitrate,

in milligrams per liter as nitrogen

No Action 

EXPLANATION

Comanche South

Joint Use Pipeline North

Master Contract Only

(Colorado Department of Public Health and Environment, 

2007). The standard was not exceeded by any of the annual 

85th percentile values for any simulated scenario for any 

simulated year at either site (tables 8 and 9).

Total Phosphorus

Comparisons among scenarios for annual median total 

phosphorus concentrations at site 7B were similar to the 

comparisons of dissolved nitrate concentrations. The annual 

median concentrations in the epilimnion at site 7B generally 

were the same between the No Action scenario and either 

the Comanche South, Joint Use Pipeline North, or Master 

Contract Only scenarios (fig. 27). The largest percent difference from the No Action scenario did not exceed 6 percent; 

an increase of this magnitude equated to a difference of only 

0.001 mg/L. Similar results were observed in the hypolimnion 

at site 7B (table 6).

Similar comparisons were made between the No Action 

scenario and the other simulation scenarios at site 3B (table 7). 

Annual median total phosphorus concentrations at site 3B 

were similar in magnitude to concentrations observed in the 

epilimnion and hypolimnion at site 7B. No specific waterquality standards were applicable for comparison to the 

simulated results.

Total Iron

The annual median total iron concentrations were small 

in the epilimnion at site 7B for the No Action scenario and the 

three other simulation scenarios (fig. 28). Simulation results 

for these various scenarios indicated that concentrations were 

less than or equal to 0.001 mg/L during much of the year.

Annual median total iron concentrations in the hypolimnion 

at site 7B were larger than in the epilimnion but still were 

relatively small. However, a seasonal analysis of total iron 

concentrations in the hypolimnion at this site showed periods 

of increased concentrations (fig. 29). The seasonal periods 

occurred at similar times when anoxic conditions in the reservoir were observed (fig. 6). It is likely that iron was released 

from the reservoir bottom during these times. These relatively 

short episodes of high iron concentrations were reflected in the 

annual 85th percentile concentrations shown in table 8.

Concentrations generally were similar between the No 

Action scenario and each of the three other simulation scenarios at site 3B. Differences in concentration from the No Action 

scenario were no more than 0.01 mg/L for any comparison 

to the Comanche South or Master Contract Only scenarios 

(table 7). Comparisons of simulated iron concentrations 

between the No Action scenario and the Joint Use Pipeline 

North scenario were more variable, particularly in WY 2002 

when the difference in the epilimnion was 0.018 mg/L. Larger 

annual median total iron concentrations were observed near 

the upstream end of Pueblo Reservoir (site 3B) than those near 

the surface at site 7B (tables 6 and 7). Total iron concentrations would be expected to be larger in response to suspension 

of particulate matter at the upstream site.

The chronic surface-water water-quality standard 

for total iron in Pueblo Reservoir is 1 mg/L (Colorado 

Department of Public Health and Environment, 2007). The 

impacts of iron on aquatic life are uncertain, and the benefit 

of iron as a water-quality standard is more an indicator of 

sediment loading (Colorado Department of Public Health 

and Environment, 2005). No calculated annual median 

value at sites 7B or 3B exceeded this standard value at any 

reservoir depth for any of the four simulation scenarios 

(tables 6 and 7). Caution should be used when applying the 
34 Simulated Effects of Proposed Arkansas Valley Conduit, Pueblo Reservoir, Southeastern Colorado

Figure 28. Annual median total iron concentrations in the epilimnion and hypolimnion at site 7B for the No Action, Comanche South, 

Joint Use Pipeline North, and Master Contract Only scenarios (direct-effects analyses).

Epilimnion

Less than 0.001 Less than 0.001 Less than 0.001

Hypolimnion

Less than 0.001

2000 2001 2002

Water year

2000 2001 2002

Water year

0.000

0.002

0.004

0.006

0.008

0.010

Total iron, in milligrams per literTotal iron, in milligrams per liter

0.000

0.002

0.004

0.006

0.008

0.010

No Action 

EXPLANATION

Comanche South

Joint Use Pipeline North

Master Contract Only

Figure 27. Annual median total phosphorus concentrations in the epilimnion and hypolimnion at site 7B for the No Action, Comanche 

South, Joint Use Pipeline North, and Master Contract Only scenarios (direct-effects analyses).

Epilimnion Hypolimnion

2000 2001 2002

Water year

2000 2001 2002

Water year

0.00

0.01

0.02

0.03

0.04

0.05

Total phosphorus, in milligrams per liter

0.00

0.01

0.02

0.03

0.04

0.05

Total phosphorus, in milligrams per liter

No Action 

EXPLANATION

Comanche South

Joint Use Pipeline North

Master Contract Only
Comparison of Results for Selected Simulation Scenarios 35

Figure 29. Comparison of total iron concentrations in the hypolimnion at site 7B in Pueblo 

Reservoir for the No Action, Comanche South, Joint Use Pipeline North, and Master Contract 

Only scenarios (direct-effects analyses).

O N D J F M A M J J A S O N D J F M A M J J A S O N D J F M A M J J A S

Water year 2001

(average year)

Water year 2002

(dry year)

Water year 2000

(wet year)

0

10

20

30

40

50

60

Total iron, in milligrams per liter

No Action

Comanche South

Joint Use Pipeline North

Master Contract Only

EXPLANATION

simulated total iron concentrations to water-quality standards 

since the absolute mean error reported for the calibrated 

Pueblo Reservoir model was 1.48 mg/L (Galloway and 

others, 2008).

Algal Groups and Chlorophyll-a

The simulated distribution of algal populations was 

highly variable in Pueblo Reservoir from WY 2000 through 

WY 2002 (fig. 30). The largest algal biomass at site 7B 

generally occurred from May through September when 

blue-green and green algae were the dominant algal groups; 

blue-green algae increased sharply during the summer months. 

Generally, simulated algae biomass concentrations in the epilimnion at site 7B were similar for the No Action, Comanche 

South, Joint Use Pipeline North, and Master Contract Only 

scenarios and typically were less than 1 mg/L for any group 

(fig. 30).

Algae biomass concentrations in the epilimnion at 

site 3B were more variable than in the epilimnion at site 

7B, but the general relation between the biomass concentrations for the simulated scenarios remained similar to those 

observed at site 7B (fig. 30). The diatoms and flagellates were 

the dominant algal group at this upstream site in the reservoir 

in WY 2000 and WY 2001; biomass concentrations for the 

scenarios were less than 1 mg/L for all the algal groups. The 

blue-green algae were the dominant algal group in WY 2002 

and biomass concentrations were less than 2 mg/L.

Harmful algal blooms in freshwater, particularly from 

blue-green algae, can occur when water use is impaired due to 

excessive accumulations of nutrients. Simulated algae biomass 

concentrations associated with No Action, Comanche South, 

Joint Use Pipeline North, or Master Contract Only scenarios 

would not be expected to pose a health issue or produce tasteand-odor problems in Pueblo Reservoir (Graham, 2006).

Annual median chlorophyll-a concentrations in the 

epilimnion at site 7B generally were similar between the No 

Action scenario and the Comanche South, Joint Use Pipeline 

North, and the Master Contract Only scenario (fig. 31). 

Specifically, the difference between the median chlorophyll-a

concentrations and each of these scenarios did not exceed 

0.08 μg/L in the epilimnion (table 6). Similar relations 

were observed in the hypolimnion, but concentrations were 

consistently smaller than concentrations in the epilimnion 

and the difference between the median chlorophyll-a did not 

exceed 0.01 μg/L.
36 Simulated Effects of Proposed Arkansas Valley Conduit, Pueblo Reservoir, Southeastern Colorado

Figure 30. Relation between various algal groups in the epilimnion at sites 7B and 3B for the No Action, Comanche South, Joint Use 

Pipeline North, and Master Contract Only scenarios (direct-effects analyses).

No Action 

Site 7B Site 3B

No Action 

Comanche South Comanche South

Joint Use Pipeline North Joint Use Pipeline North

Master Contract Only Master Contract Only

O N D J F M A MJ J A S O N D J F M A MJ J A S O N D J F M A MJ J A S

Water year 2000 Water year 2001 Water year 2002

O N D J F M A MJ J A S O N D J F M A M J J A S O N D J F M A MJ J A S

Water year 2000 Water year 2001 Water year 2002

0

1

2

3

0

1

2

3

Algal biomass, in milligrams per liter as carbon

0

1

2

3

0

1

2

3

0

1

2

3

0

1

2

3

0

1

2

3

0

1

2

3

EXPLANATION

Blue-green algae

Green algae

Diatoms

Flagellates
Summary and Conclusions 37

Figure 31. Annual median chlorophyll–a concentrations in the epilimnion and hypolimnion at site 7B for the No Action, Comanche 

South, Joint Use Pipeline North, and Master Contract Only scenarios (direct-effects analyses).

Summary and Conclusions

The Fryingpan-Arkansas Project (Project) is a 

multipurpose transmountain, transbasin water diversion and 

delivery project that annually diverts surplus water from the 

western slope of the Rocky Mountains to the Arkansas River 

Basin. As part of the Public Law 87-590 which authorized the 

Project, authorization was included to construct a municipal 

water-supply pipeline to provide communities downstream 

from Pueblo Reservoir with a source of high-quality water. 

In 2009, Congress authorized appropriations and cost-sharing 

language to proceed with project planning and implementation 

of the Arkansas Valley Conduit (AVC). The purpose of the 

AVC is to deliver water for municipal and industrial use 

within the boundaries of the Southeastern Colorado Water 

Conservancy District. Water supplied through the AVC 

would serve two needs: (1) to supplement or replace existing 

poor-quality water to communities downstream from Pueblo 

Reservoir; and (2) to meet a portion of the AVC participants’ 

projected water demands through 2070. The Bureau of 

Reclamation (Reclamation) initiated an Environmental Impact 

Statement (EIS) to address the potential environmental 

consequences associated with constructing and operating 

the proposed AVC, entering into a conveyance contract 

for the Pueblo Dam north-south outlet works interconnect 

(Interconnect), and entering into a long-term excess capacity 

master contract (Master Contract). Reclamation chose to 

evaluate the environmental effects of these three independent 

proposed actions in the same EIS because of overlap in 

area, timing, and participants. A complete description of 

the Arkansas Valley Conduit Draft Environmental Impact 

Statement can be found at http://www.usbr.gov/avceis. To 

that end, six action alternatives and one no action alternative 

were evaluated in the EIS to meet the purpose and needs of 

the AVC, Interconnect, and Master Contract. Reclamation 

understands that there may be water-based issues (surfacewater hydrology, water quality, aquatic species, groundwater, 

wetlands, and recreation) associated with each of the proposed 

alternatives.

Operational changes, as a result of implementation 

of these alternatives, could change the hydrodynamics and 

water-quality conditions in Pueblo Reservoir. The reservoir, 

located west of Pueblo, Colo., is the primary source of water 

for the conduit and is one of southeastern Colorado’s most 

valuable water resources. It provides irrigation, municipal, 

and industrial water to various entities throughout the region 

as well as providing flood control, recreational activities, 

sport fishing, and wildlife enhancements to the region. The 

hydrodynamics and water quality of Pueblo Reservoir were 

modeled previously (2008), and the results of the modeling 

were documented by the USGS.

Discussions with Reclamation and the U.S. Geological 

Survey (USGS) led to an interagency agreement between 

the two Federal agencies to simulate the hydrodynamics and 

water quality of Pueblo Reservoir and to make comparisons 

of simulated hydrodynamics and water quality for projected 

demands associated with four of the seven proposed EIS 

alternatives. Scenario simulations were done using the 

documented USGS Pueblo Reservoir model developed 

from the U.S. Army Corps of Engineers CE-QUAL-W2 

model (version 3.2). Comparisons of the simulated results 

were conducted to determine if substantial differences were 

observed between selected scenarios.

The four alternatives submitted to the USGS for scenario 

simulation included various combinations (action or no action) 

of the proposed AVC, Master Contract, and Interconnect 

Epilimnion Hypolimnion

2000 2001 2002

Water year

2000 2001 2002

Water year

0.0

0.2

0.4

0.6

0.8

1.0

Chlorophyll-a, in micrograms per liter

0.0

0.2

0.4

0.6

0.8

1.0

Chlorophyll-a, in micrograms per liter

No Action 

EXPLANATION

Comanche South

Joint Use Pipeline North

Master Contract Only
38 Simulated Effects of Proposed Arkansas Valley Conduit, Pueblo Reservoir, Southeastern Colorado

options. The four scenario simulations were the No Action 

(AVC and Interconnect, no action; Master Contract, no action), 

the Comanche South (AVC and Interconnect, proposed action; 

Master Contract, proposed action), the Joint Use Pipeline 

North (AVC and Interconnect, proposed action; Master 

Contract, no action), and the Master Contract Only (AVC and 

Interconnect, no action; Master Contract, proposed action). 

Each of the scenarios was simulated for three contiguous 

water years (WY) representing a wet, average, and dry annual 

hydrologic cycle. Streamflow, diversion, reservoir storage, 

and return-flow quantity data for projected demands in 2070 

were provided to the USGS by contractors for Reclamation. 

Water-quality data for this effort was originally provided to the 

USGS (2009) by contractors for Reclamation as described for 

the Existing Conditions simulation scenario documented by 

the USGS in a previous report.

Additionally, each selected simulation scenario was 

evaluated for differences in direct/indirect effects (herein 

referred to as “direct effects”) and cumulative effects on a 

particular scenario. Direct effects are intended to isolate the 

future effects of the scenarios. Cumulative effects are intended 

to evaluate the effects of the scenarios in conjunction with 

all reasonably foreseeable future activities in the study area. 

The primary difference between the two sets of simulations 

was that the direct-effects simulations include existing levels 

of demand by nonparticipants in the AVC/Master Contract 

project, whereas the cumulative-effects simulations include 

projected demands in 2070 by the nonparticipants in the AVC/

Master Contract project.

Finally, scenario simulations were done that represented 

existing conditions in Pueblo Reservoir. The results of the 

Existing Conditions scenario were compared to the No Action 

scenario to assess changes in water quality from current 

demands (2006) to projected demands in 2070. All simulations 

used an external nutrient-decay model to simulate degradation 

and assimilation of selected nutrients along the riverine reach 

upstream from Pueblo Reservoir as described in previous 

USGS simulation reports on Pueblo Reservoir.

Various tools were used to simulate results for 

comparison between the different simulation scenarios. 

Reservoir simulations were done using a two-dimensional 

water-quality model. Lake hydrodynamics, water temperature, 

dissolved oxygen, dissolved solids, dissolved ammonia, 

dissolved nitrate, total phosphorus, total iron, algal groups, and 

algae biomass (measured as chlorophyll-a) were simulated. 

The model accurately captured the most important seasonal 

and spatial influences on the reservoir water quality. Input 

data to the reservoir model that represented the projected 

demands in 2070 were modeled externally and provided to the 

USGS by Reclamation’s consultant. Nutrient decay along the 

riverine reach upstream from Pueblo Reservoir was simulated 

to account for the degradation and assimilation of selected 

constituents in the Arkansas River.

Two sites were selected for comparison in this report. 

Results of scenario simulations at site 3B were characteristic 

of a riverine environment in the reservoir, whereas results at 

site 7B (near the dam) were characteristic of the main body 

of the reservoir. Simulated results for the epilimnion and 

hypolimnion at these two sites were evaluated and compared. 

The results in the hypolimnion at site 7B were indicative of 

the quality of the water leaving the reservoir.

A general comparison of results for site 7B (near the 

dam) between all simulation scenarios was conducted for 

water-surface elevations, water temperatures, dissolved oxygen, dissolved solids, and ammonia concentrations. Similarities and differences between the direct- and cumulative-effects 

analyses also were compared.

Simulated water-surface elevations in Pueblo Reservoir 

were variable between the simulation scenarios, between 

the different effects analyses, and between the simulated 

hydrologic conditions. Generally, there was a substantial 

temporal decrease in water-surface elevations between the wet, 

average, and dry years. Water-surface elevations associated 

with the direct-effects analyses were larger than the watersurface elevations for the corresponding cumulative-effects 

analyses, and the differences between the effects analyses, 

for any scenario, increased temporally from wet to dry year. 

During the dry year (WY 2002), the lowest water-surface 

elevations for either the direct-effects or cumulative-effects 

analysis were associated with the No Action and Joint Use 

Pipeline North scenarios; these two scenarios do not include 

an excess capacity storage component as part of the proposed 

EIS alternative. Simulated water-surface elevations for the 

direct-effects analysis of any simulation scenario during 

WY 2000 (wet year) and WY 2001 (average year) were similar 

to the water-surface elevations for the Existing Conditions 

scenario. Water-surface elevations during WY 2002 (dry year) 

remained similar to those of the Existing Conditions scenario 

with the exception of the Joint Use Pipeline North scenario.

Water temperatures in Pueblo Reservoir have been 

shown to stratify during the summer (June-August) prior to 

mixing in September. Results from the various simulation 

scenarios showed a similar pattern. In general, the reservoir 

has been shown to be isothermal during the winter and 

water temperatures were coldest from December to April. 

Thermal stratification is apparent by May. Maximum water 

temperatures were observed in August prior to when Pueblo 

Reservoir typically mixed in September at the deeper 

locations. In general, the water temperatures in Pueblo 

Reservoir were similar for all the simulation scenarios for the 

3-year simulation period regardless of the effects analysis.

Results of the scenario simulations for dissolved oxygen 

showed the typical stratification patterns that occur in Pueblo 

Reservoir. This included anoxic conditions near the bottom of 

the reservoir during the summer before the reservoir turned 

over and mixed. Dissolved oxygen concentrations in the 
Summary and Conclusions 39

epilimnion and hypolimnion of the reservoir near the dam 

were similar to the Existing Conditions scenario for all the 

simulation scenarios regardless of the effects analysis.

Typically, simulated dissolved solids concentrations 

for the Existing Conditions scenario were similar to 

concentrations for all the direct-effects simulation scenarios. 

Concentrations for the cumulative-effects simulation scenarios 

were slightly larger than concentrations for the Existing 

Conditions scenario. Typically, the percent differences were 

less than 5 percent but could be as much as 10 percent during 

the winter months. Concentrations for the cumulative-effects 

simulation scenarios were similar among themselves. These 

results would be expected given that the reservoir storage 

for the cumulative-effects analyses was less than that for the 

direct-effect analyses and water-quality inputs were identical.

Comparisons were made between the Existing Conditions 

scenario and the No Action scenario to determine what 

differences, if any, were observed between existing conditions 

in Pueblo Reservoir (demand conditions for 2006) and the 

most likely conditions in 2070 assuming the absence of a 

major Reclamation action, such as the AVC or a storage 

contract. Analysis of the results for the direct- and cumulativeeffects analyses indicated that, in general, the results were 

similar for most of the scenarios. As such, comparisons 

between the Existing Conditions and No Action scenarios 

focused on the results from the direct-effects analysis for 

each modeled scenario. Overall, comparisons of the results 

between the Existing Conditions and the No Action scenarios 

for water-surface elevations, water temperature, dissolved 

oxygen, dissolved solids, dissolved ammonia, dissolved 

nitrate, total phosphorus, and total iron concentrations 

indicated that the annual median values generally were similar 

for all three simulated years. Additionally, algal groups and 

chlorophyll-a concentrations (algal biomass) were similar for 

the Existing Conditions and the No Action scenarios at site 7B 

in the epilimnion for the simulated period (WY 2000 through 

WY 2002).

The No Action scenario also was compared individually 

to the Comanche South, Joint Use Pipeline North, and 

Master Contract Only scenarios. Comparisons were made to 

describe changes in the annual median, 85th percentile, or 

15th percentile concentration between the No Action scenario 

and each of the other three simulation scenarios.

Simulated water-surface elevations in Pueblo Reservoir 

generally were similar between the No Action scenario 

and each of the other three simulation scenarios. Overall, 

differences in reservoir water-surface elevation increased 

each year and there was a temporal decrease in water-surface 

elevations from WY 2000 through WY 2002 for all the 

simulated scenarios.

Comparisons of the results between the No Action 

scenario and each of the other three simulation scenarios 

for water temperature indicated that the simulated scenarios 

generally provided similar results. At site 7B, the percent 

change from the No Action scenario in the epilimnion was less 

than 5 percent for all simulated years.

Comparisons of simulated DO concentrations between 

the No Action scenario and the three other scenarios indicated 

that the annual median values in the epilimnion at site 7B 

generally were similar to results for the No Action scenario. 

Typically, the percent change from the No Action scenario was 

within 2 percent for the simulated scenarios for any simulated 

year. The percent change from the No Action scenario in 

the hypolimnion was less than 6 percent for the simulated 

scenarios for any simulated year.

Comparisons of simulated dissolved solids concentrations 

indicated that the annual medians were relatively similar 

between the No Action and the Comanche South, Joint Use 

Pipeline North, and Master Contract Only scenarios in the 

epilimnion and hypolimnion at site 7B. Simulated results for 

the No Action scenario were 3 percent or less of the annual 

medians for the other three scenarios during WY 2000 through 

WY 2002. The results were similar for both the epilimnion and 

the hypolimnion. For the most part, similar results also were 

observed in the epilimnion and hypolimnion at site 3B.

The annual median dissolved ammonia (as nitrogen) 

and dissolved nitrate concentrations in the epilimnion and 

hypolimnion of Pueblo Reservoir at site 7B were similar 

between the No Action scenario and either the Comanche 

South, Joint Use Pipeline North, or Master Contract Only 

scenarios.

The annual median total iron concentrations were small 

in the epilimnion at site 7B for the No Action scenario and 

the three other simulation scenarios. Simulation results for 

these various scenarios indicated that concentrations were 

less than or equal to 0.001 mg/L during much of the year. Iron 

concentrations at site 3B generally were similar between the 

No Action scenario and the each of the three other simulation 

scenarios. Differences in concentration from the No Action 

scenario were no more than 0.01 mg/L for any comparison 

to the Comanche South or Master Contract Only scenarios.

Comparisons of simulated iron concentrations between the 

No Action scenario and the Joint Use Pipeline North scenario 

were more variable, particularly in WY 2002.

Generally, simulated algae biomass concentrations in 

the epilimnion at site 7B were similar for the No Action, 

Comanche South, Joint Use Pipeline North, and Master 

Contract Only scenarios and concentrations typically were 

less than 1 mg/L. Annual median chlorophyll-a concentrations 

in the epilimnion at site 7B generally were similar between 

the No Action scenario and the Comanche South, Joint Use 

Pipeline North, and the Master Contract Only scenario. 

Specifically, the difference between the median chlorophyll-a

concentrations and each of these scenarios did not exceed 

0.08 μg/L.
40 Simulated Effects of Proposed Arkansas Valley Conduit, Pueblo Reservoir, Southeastern Colorado

References Cited

Bales, J.D., Sarver, K.M., and Giorgino, M.J., 2001, Mountain 

Island Lake, North Carolina—Analysis of ambient 

conditions and simulation of hydrodynamics, constituent 

transport, and water-quality characteristics, 1996–97: 

U.S. Geological Survey Water-Resources Investigations 

Report 01–4138, 85 p.

Britton, L.J., and Greeson, E.E., eds., 1989, Methods 

for collection and analysis of aquatic biological and 

microbiological samples: U.S. Geological Survey Techniques 

of Water-Resources Investigations, book 5, chap. A4, 363 p.

Bureau of Reclamation, 1977, Pueblo Reservoir area-capacity 

table and curves: U.S. Department of Interior, FryingpanArkansas Project, Colorado, unnumbered pages.

Bureau of Reclamation, 2010, Public scoping meeting: 

Arkansas Valley conduit and excess capacity master contract 

Environmental Impact Statement, presented August 16–19, 

2010, at various locations, accessed December 1, 2011, at 

http://www.usbr.gov/avceis/introandparticipants.pdf.

Bureau of Reclamation, 2011a, Fryingpan-Arkansas Project: 

U.S. Department of Interior, accessed November 30, 

2011, at http://www.usbr.gov/projects/Project.jsp?proj_

Name=Fryingpan-Arkansas+Project.

Bureau of Reclamation, 2011b, Newsletter: Arkansas Valley 

Conduit and long-term excess capacity master contract, 

released October 2011, accessed November 30, 2011, at 

http://www.usbr.gov/avceis/newsletter_10_2011.pdf.

Bureau of Reclamation, 2012, Draft Environmental Impact 

Statement–Arkansas Valley Conduit and long-term excess 

capacity master contract, Fryingpan-Arkansas Project: 

U.S. Department of the Interior, accessed January 30, 2013, 

at http://www.usbr.gov/avceis.

Chorus, Ingrid, and Bartram, Jamie, eds, 1999, Toxic 

cyanobacteria in water—A guide to their public health 

consequences, monitoring and management: London 

and New York, Routledge Publishing, World Health 

Organization, 400 p.

Cole, T.M., and Wells, S.A., 2003, CEQUAL-W2: A twodimensional, laterally averaged, hydrodynamic and water 

quality model, version 3.2: U.S. Army Corps of Engineers 

Instruction Report EL-03-1, variously paginated.

Colorado Department of Public Health and Environment, 

2005, The basic standards and methodologies for surface 

water: Water Quality Control Commission, 5 CCR 1002-31, 

Regulation number 31, p. 178.

Colorado Department of Public Health and Environment, 

2007, Classifications and numeric standards for the 

Arkansas River Basin: Water Quality Control Commission, 

5 CCR 1002-32, Regulation number 32, p. 72.

Edelmann, Patrick, 1989, Reconnaissance of water quality 

in Pueblo Reservoir—May through December 1985: 

U.S. Geological Survey Water-Resources Investigations 

Report 88–4118, 53 p.

Galloway, J.M., and Green, W.R., 2006, Analysis of 

ambient conditions and simulation of hydrodynamics and 

water-quality characteristics in Beaver Lake, Arkansas, 

2001 through 2003: U.S. Geological Survey Scientific 

Investigations Report 2006–5003, 55 p.

Galloway, J.M., Ortiz, R.F., Mau, D.P., Miller, L.D., and 

Bales, J.D., 2008, Simulation of hydrodynamics and water 

quality in Pueblo Reservoir, southeastern Colorado, for 

1985 to 1987 and 1999 to 2002: U.S. Geological Survey 

Scientific Investigations Report 2008–5056, 56 p.

Graffy, E.A., Helsel, D.R., and Mueller, D.K., 1996, Nutrients 

in the Nation’s waters; identifying problems and progress: 

U.S. Geological Survey Factsheet 218–96, 6 p.

Graham, J.L., 2006, Harmful algal blooms: U.S. Geological 

Survey Fact Sheet 2006–3147, 2 p.

Green, W.R., 2001, Analysis of ambient conditions and 

simulation of hydrodynamics, constituent transport, and 

water-quality characteristics in Lake Maumelle, Arkansas, 

1991–92: U.S. Geological Survey Water-Resources 

Investigations Report 2001–4045, 60 p.

Hem, J.D., 1985, Study and interpretation of the chemical 

characteristics of natural water (3rd ed.): U.S. Geological 

Survey Water-Supply Paper 2254, 263 p.

Labadie, J.W., Baldo, M.L., and Larson, R., 2000, 

MODSIM— Decision support system for river basin 

management documentation and user manual: Colorado 

State University and Bureau of Reclamation, May 2000, 

53 p.

MWH Americas, Inc., 2008, Water-quality technical 

report, Southern Delivery System Environmental Impact 

Statement: Prepared for the Bureau of Reclamation, 198 p.

Ortiz, R.F., and Miller, L.D., 2009, Revised comparisons of 

simulated hydrodynamics and water quality for projected 

demands in 2046, Pueblo Reservoir, Southeastern 

Colorado: U.S. Geological Survey Scientific Investigations 

Report 2009–5083, 78 p.
References Cited 41

Pilotto, L.S., Douglas, R.M., Burch, M.D., Cameron, S., 

Beers, M., Rouch, G.R., Robinson, P., Kirk, M., Cowie, 

C.T., Hardiman, S., Moore, C., and Attewell, R.G., 1997, 

Health effects of recreational exposure to cyanobacteria 

(blue-green) during recreational water-related activities: 

Australian and New Zealand Journal of Public Health, v. 21, 

p. 562–566.

Rounds, S.A., and Wood, T.M., 2001, Modeling water quality 

in the Tualatin River, Oregon, 1991–1997: U.S. Geological 

Survey Water-Resources Investigations Report 2001–4041, 

53 p.

Southeastern Colorado Water Conservancy District, 2007, 

History and description of the Fryingpan-Arkansas Project: 

Southeastern Colorado Water Conservancy District, 

accessed March 13, 2007, at http://www.secwcd.com/

History%20and%20Description.htm.

Southeastern Colorado Water Conservancy District, 2013, 

District boundaries map: Southeastern Colorado Water 

Conservancy District, accessed January 13, 2013, at 

http://www.secwcd.org/map.htm.

Sullivan, A.B., and Rounds, S.A., 2004, Modeling streamflow 

and water temperature in the North Santiam and Santiam 

Rivers, Oregon, 2001–02: U.S. Geological Survey Scientific 

Investigations Report 2004–5001, 35 p.

Sullivan, A.B., and Rounds, S.A., 2005, Modeling 

hydrodynamics, temperature, and water quality in Henry 

Hagg Lake, Oregon, 2000–2003: U.S. Geological Survey 

Scientific Investigations Report 2004–5261, 38 p.

Sullivan, A.B., Rounds, S.A., Sobieszczyk, S., and Bragg, 

H.M., 2007, Modeling hydrodynamics, water temperature, and suspended sediment in Detroit Lake, Oregon: 

U.S. Geological Survey Scientific Investigations 

Report 2007–5008, 40 p.

U.S. Environmental Protection Agency, 1992, Secondary 

drinking water regulations—Guidance for Nuisance 

Chemicals: U.S. Environmental Protection Agency 

EPA 810/K-92-001, accessed August 27, 2007, at http://

www.epa.gov/safewater/consumer/2ndstandards.html.

Appendixes 43

Appendix 1. Percent change between annual median values for selected constituents in the epilimnion and hypolimnion at site 7B for 

the Existing Conditions scenario (water years 2000 through 2002) as compared to the No Action (cumulative-effects analysis) scenario.

[N, nitrogen; P, phosphorus; °C, degrees Celsius; mg/L, milligrams per liter; μg/L, micrograms per liter; NA, not applicable; <, less than]

Water

year

Simulation

scenario

Percent of

annual

results

available

Water

temperature

(°C)

Dissolved

oxygen

(mg/L)

Dissolved

solids

(mg/L)

Dissolved

ammonia 

as N

(mg/L)

Dissolved

nitrate

as N

(mg/L)

Total

phosphorus

as P

(mg/L)

Total

iron

(mg/L)

Chlorophyll-a

(μg/L)

Epilimnion

2000 Existing Conditions 100 14.6 7.8 283 0.003 0.006 0.014 <0.001 0.55

No Action 100 14.6 7.9 284 .003 .006 .014 <.001 .52

Percent change 0% 1.3% .4% 0% 0% 0% NA –5.5%

2001 Existing Conditions 100 14.6 7.8 229 .003 .009 .016 <.001 .26

No Action 100 13.4 8.2 237 .002 .007 .017 <.001 .44

Percent change –8.2% 5.1% 3.5% –33% –22% 6.2% NA 69%

2002 Existing Conditions 100 14.4 8.0 233 .003 .007 .017 <.001 .30

No Action 100 14.2 8.4 252 .003 .006 .019 <.001 .38

Percent change –1.4% 5.0% 8.2% 0% –14% 12% NA 27%

Hypolimnion

2000 Existing Conditions 100 10.7 7.5 284 .010 .006 .015 .005 12

No Action 100 10.4 7.6 284 .009 .006 .015 .005 14

Percent change –2.8% 1.3% 0% –10% 0% 0% 0% 17%

2001 Existing Conditions 100 9.6 7.6 233 .007 .008 .017 .003 .07

No Action 100 10.4 7.6 242 .007 .010 .018 .003 .08

Percent change 8.3% 0% 3.9% 0% 25% 5.9% 0% 14%

2002 Existing Conditions 100 9.7 8.0 233 .006 .005 .017 <.001 .06

No Action 100 10.4 7.8 250 .006 .004 .019 .004 .10

Percent change 7.2% –2.5% 7.3% 0% –20% 12% NA 67%

Appendix 2. Percent change between annual median values for selected constituents in the epilimnion and hypolimnion at site 3B for 

the Existing Conditions scenario (water years 2000 through 2002) as compared to the No Action (cumulative-effects analysis) scenario.

[N, nitrogen; P, phosphorus; °C, degrees Celsius; mg/L, milligrams per liter; μg/L, micrograms per liter; --, summary statistic not calculated; NA, not applicable]

Water

year

Simulation

scenario

Percent of

annual

results

available

Water

temperature

(°C)

Dissolved

oxygen

(mg/L)

Dissolved

solids

(mg/L)

Dissolved

ammonia

as N

(mg/L)

Dissolved

nitrate

as N

(mg/L)

Total

phosphorus

as P

(mg/L)

Total

iron

(mg/L)

Chlorophyll-a

(μg/L)

Epilimnion

2000 Existing Conditions 100 14.1 7.9 287 0.001 0.005 0.015 0.010 0.98

No Action 100 14.0 7.9 289 .001 .010 .016 .018 .84

Percent change –.7% 0% .7% 0% 100% 6.7% 80% –14%

2001 Existing Conditions 100 13.5 8.0 235 .002 .019 .018 .010 .74

No Action 100 11.3 8.3 246 .010 .083 .022 .122 .20

Percent change –16% 3.8% 4.7% 400% 337% 22% 1,120% –73%

2002 Existing Conditions 100 13.4 7.9 260 .003 .008 .023 .013 1.41

No Action 100 9.0 8.1 271 .020 .092 .026 .466 .15

Percent change –33% 2.5% 4.2% 567% 1,050% 13% 3,480% –89%

Hypolimnion

2000 Existing Conditions 100 12.1 7.8 286 .002 .013 .016 .029 .68

No Action 100 12.0 7.8 289 .002 .015 .016 .038 .60

Percent change –.8% 0% 1.0% 0% 15% 0% 31% –12%

2001 Existing Conditions 100 11.0 7.8 239 .003 .036 .019 .027 .51

No Action 88 8.4 9.3 245 .010 .081 .022 .133 .20

Percent change –24% 19% 2.5% 233% 125% 16% 393% –61%

2002 Existing Conditions 100 12.2 7.8 260 .003 .009 .022 .020 1.40

No Action 15 -- -- -- -- -- -- -- --

Percent change NA NA NA NA NA NA NA NA
44 Simulated Effects of Proposed Arkansas Valley Conduit, Pueblo Reservoir, Southeastern Colorado

Appendix 3. Percent change between annual 85th percentile values for selected constituents and the annual 15th percentile values 

for dissolved oxygen concentrations in the epilimnion and hypolimnion at site 7B for the Existing Conditions scenario (water years 2000 

through 2002) as compared to the No Action (cumulative-effects analysis) scenario.

[N, nitrogen; P, phosphorus; °C, degrees Celsius; mg/L, milligrams per liter; μg/L, micrograms per liter; NA, not applicable; <, less than]

Water

year

Simulation

scenario

Percent of

annual

results

available

Water

temperature

(°C)

Dissolved

oxygen

(mg/L)

Dissolved

solids

(mg/L)

Dissolved

ammonia

as N

(mg/L)

Dissolved

nitrate

as N

(mg/L)

Total

phosphorus

as P

(mg/L)

Total

iron

(mg/L)

Chlorophyll-a

(μg/L)

Epilimnion

2000 Existing Conditions 100 25.2 5.8 294 0.006 0.012 0.017 0.017 1.17

No Action 100 25.2 5.6 294 .006 .016 .016 .006 1.11

Percent change 0% –3.4% 0% 0% 33% –5.9% –65% –5.1%

2001 Existing Conditions 100 24.5 5.0 237 .007 .016 .017 .005 .94

No Action 100 24.5 5.1 248 .006 .019 .018 .008 1.10

Percent change 0% 2.0% 4.6% –14% 19% 5.9% 60% 17%

2002 Existing Conditions 100 24.5 5.5 275 .011 .028 .018 <.001 1.08

No Action 100 24.6 5.1 288 .010 .016 .021 .003 1.27

Percent change .4% –7.3% 4.7% –9.1% –43% 17% NA 18%

Hypolimnion

2000 Existing Conditions 100 18.3 <.1 296 .016 .009 .020 6.49 .82

No Action 100 18.4 <.1 295 .014 .009 .018 4.97 .82

Percent change .5% NA –.3% –12% 0% –10% –23% 0%

2001 Existing Conditions 100 18.9 <.1 238 .016 .014 .022 5.65 .14

No Action 100 20.6 .4 248 .012 .018 .018 .432 .15

Percent change 9.0% NA 4.2% –25% 29% –18% –92% 7.1%

2002 Existing Conditions 100 15.5 <.1 249 .013 .007 .022 2.18 .25

No Action 100 19.2 <.1 269 .021 .009 .027 3.07 .29

Percent change 24% NA 8.0% 62% 29% 23% 41% 16%

Appendix 4. Percent change between annual 85th percentile values for selected constituents and the annual 15th percentile values 

for dissolved oxygen concentrations in the epilimnion and hypolimnion at site 3B for the Existing Conditions scenario (water years 2000 

through 2002) as compared to the No Action (cumulative-effects analysis) scenario.

[N, nitrogen; P, phosphorus; °C, degrees Celsius; mg/L, milligrams per liter; μg/L, micrograms per liter; --, summary statistic not calculated; NA, not applicable]

Water

year

Simulation

scenario

Percent of

annual

results

available

Water

temperature

(°C)

Dissolved

oxygen

(mg/L)

Dissolved

solids

(mg/L)

Dissolved

ammonia

as N

(mg/L)

Dissolved

nitrate

as N

(mg/L)

Total

phosphorus

as P

(mg/L)

Total

iron

(mg/L)

Chlorophyll-a

(μg/L)

Epilimnion

2000 Existing Conditions 100 23.8 6.1 296 0.002 0.034 0.017 0.098 1.89

No Action 100 23.0 6.0 299 .003 .033 .018 .094 1.80

Percent change –3.4% –1.6% 1.0% 50% –2.9% 5.9% –4.1% –4.8%

2001 Existing Conditions 100 23.3 5.9 243 .008 .063 .021 .181 1.21

No Action 100 20.9 5.6 303 .020 .103 .025 1.30 1.51

Percent change –10% –5.1% 25% 150% 63% 19% 618% 25%

2002 Existing Conditions 100 23.2 6.1 326 .010 .059 .027 .041 5.27

No Action 100 17.2 6.2 360 .020 .099 .029 .880 .40

Percent change –26% 1.6% 10% 100% 68% 7.4% 2,050% –92%

Hypolimnion

2000 Existing Conditions 100 23.1 4.8 299 .004 .032 .018 .498 1.50

No Action 100 22.4 4.9 304 .007 .037 .018 .450 1.52

Percent change –3.0% 2.1% 1.7% 75% 16% 0% –9.6% 1.3%

2001 Existing Conditions 100 23.3 5.9 243 .008 .063 .021 .181 1.21

No Action 88 20.6 5.4 282 .019 .103 .024 1.81 1.34

Percent change –12% –8.5% 16% 138% 63% 14% 900% 11%

2002 Existing Conditions 100 23.0 5.9 326 .009 .047 .027 .047 4.92

No Action 15 -- -- -- -- -- -- -- --

Percent change NA NA NA NA NA NA NA NA
Appendixes 45

Appendix 5. Percent change between annual median values for selected constituents in the epilimnion and hypolimnion at site 7B for 

cumulative-effects analyses for the Comanche South, Joint Use Pipeline North, and Master Contract Only scenarios as compared to the 

No Action scenario.

[N, nitrogen; P, phosphorus; °C, degrees Celsius; mg/L, milligrams per liter; μg/L, micrograms per liter; NA, not applicable; <, less than]

Water

year

Simulation

scenario

Percent of

annual

results

available

Water

temperature

(°C)

Dissolved 

oxygen

(mg/L)

Dissolved

solids

(mg/L)

Dissolved

ammonia

as N

(mg/L)

Dissolved

nitrate

as N

(mg/L)

Total

phosphorus

as P

(mg/L)

Total

iron

(mg/L)

Chlorophyll-a

(μg/L)

Epilimnion

2000

No Action 100 14.6 7.9 284 0.003 0.006 0.014 <0.001 0.52

Comanche South 100 14.7 7.8 281 .003 .005 .014 <.001 .53

Percent change .7% –1.3% –1.1% 0% –17% 0% NA 1.9%

No Action 100 14.6 7.9 284 .003 .006 .014 <.001 .52

Joint Use Pipeline North 100 14.6 7.9 285 .003 .006 .014 <.001 .54

Percent change 0% 0% .4% 0% 0% 0% NA 3.8%

No Action 100 14.6 7.9 284 .003 .006 .014 <.001 .52

Master Contract Only 100 14.7 7.8 282 .003 .005 .014 <.001 .52

Percent change .7% –1.3% –.7% 0% –17% 0% NA 0%

Hypolimnion

2000

No Action 100 10.4 7.6 284 .009 .006 .015 .005 .14

Comanche South 100 10.6 7.6 281 .010 .006 .015 .005 .14

Percent change 1.9% 0% –1.1% 11% 0% 0% 0% 0%

No Action 100 10.4 7.6 284 .009 .006 .015 .005 .14

Joint Use Pipeline North 100 10.5 7.6 284 .010 .006 .015 .005 .13

Percent change 1.0% 0% 0% 11% 0% 0% 0% –7.1%

No Action 100 10.4 7.6 284 .009 .006 .015 .005 .14

Master Contract Only 100 10.6 7.6 282 .010 .006 .015 .005 .13

Percent change 1.9% 0% –.7% 11% 0% 0% 0% –7.1%

Epilimnion

2001

No Action 100 13.4 8.2 237 .002 .007 .017 <.001 .44

Comanche South 100 14.4 8.2 238 .002 .007 .017 <.001 .45

Percent change 7.5% 0% .4% 0% 0% 0% NA 2.3%

No Action 100 13.4 8.2 237 .002 .007 .017 <.001 .44

Joint Use Pipeline North 100 14.4 8.2 239 .002 .007 .017 <.001 .48

Percent change 7.5% 0% .8% 0% 0% 0% NA 9.1%

No Action 100 13.4 8.2 237 .002 .007 .017 <.001 .44

Master Contract Only 100 14.4 8.2 239 .002 .008 .017 <.001 .42

Percent change 7.5% 0% .8% 0% 14% 0% NA –4.5%

Hypolimnion

2001

No Action 100 10.4 7.6 242 .007 .010 .018 .003 .08

Comanche South 100 9.4 7.9 242 .007 .009 .018 .004 .08

Percent change –9.6% 3.9% 0% 0% –10% 0% 33% 0%

No Action 100 10.4 7.6 242 .007 .010 .018 .003 .08

Joint Use Pipeline North 100 9.6 7.8 242 .007 .009 .018 .004 .09

Percent change –7.7% 2.6% 0% 0% –10% 0% 33% 12%

No Action 100 10.4 7.6 242 .007 .010 .018 .003 .08

Master Contract Only 100 9.3 8.0 241 .007 .008 .018 .003 .07

Percent change –11% 5.3% –.4% 0% –20% 0% 0% –12%

Epilimnion

2002

No Action 100 14.2 8.4 252 .003 .006 .019 <.001 .38

Comanche South 100 14.2 8.3 251 .003 .006 .018 <.001 .37

Percent change 0% –1.2% –.4% 0% 0% –5.3% NA –2.6%

No Action 100 14.2 8.4 252 .003 .006 .019 <.001 .38

Joint Use Pipeline North 100 14.2 8.4 252 .003 .005 .019 <.001 .37

Percent change 0% 0% 0% 0% –17% 0% NA –2.6%

No Action 100 14.2 8.4 252 .003 .006 .019 <.001 .38

Master Contract Only 100 14.1 8.3 248 .003 .008 .018 <.001 .35

Percent change –.7% –1.2% –1.6% 0% 33% –5.3% NA –7.9%

Hypolimnion

2002

No Action 100 10.4 7.8 250 .006 .004 .019 .004 .10

Comanche South 100 10.1 7.8 249 .006 .005 .019 .004 .11

Percent change –2.9% 0% –.4% 0% 25% 0% 0% 10%

No Action 100 10.4 7.8 250 .006 .004 .019 .004 .10

Joint Use Pipeline North 100 10.6 7.7 250 .006 .004 .019 .004 .11

Percent change 1.9% –1.3% .0% 0% 0% 0% 0% 10%

No Action 100 10.4 7.8 250 .006 .004 .019 .004 .10

Master Contract Only 100 10.3 7.7 247 .006 .005 .019 .004 .13

Percent change –1.0% –1.3% –1.2% 0% 25% 0% 0% 30%
46 Simulated Effects of Proposed Arkansas Valley Conduit, Pueblo Reservoir, Southeastern Colorado

Appendix 6. Percent change between annual median values for selected constituents in the epilimnion and hypolimnion at site 3B for 

cumulative-effects analyses for the Comanche South, Joint Use Pipeline North, and Master Contract Only scenarios as compared to the 

No Action scenario.

[N, nitrogen; P, phosphorus; °C, degrees Celsius; mg/L, milligrams per liter; μg/L, micrograms per liter; --, summary statistic not calculated; NA, not applicable; 

<, less than]

Water 

year

Simulation

scenario

Percent of

annual

results

available

Water

temperature

(°C)

Dissolved

oxygen

(mg/L)

Dissolved

solids

(mg/L)

Dissolved

ammonia

as N

(mg/L)

Dissolved 

nitrate

as N

(mg/L)

Total

phosphorus

as P

(mg/L)

Total

iron

(mg/L)

Chlorophyll-a

(μg/L)

Epilimnion

2000

No Action 100 14.0 7.9 289 <0.001 0.010 0.016 0.018 0.84

Comanche South 100 14.0 7.9 285 <.001 .008 .016 .018 .89

Percent change 0% 0% –1.4% NA –20% 0% 0% 6.0%

No Action 100 14.0 7.9 289 <.001 .010 .016 .018 .84

Joint Use Pipeline North 100 14.0 7.9 289 <.001 .011 .016 .019 .81

Percent change 0% 0% 0% NA 10% 0% 5.6% –3.6%

No Action 100 14.0 7.9 289 <.001 .010 .016 .018 .84

Master Contract Only 100 14.0 7.9 286 <.001 .008 .015 .016 .85

Percent change 0% 0% –1.0% NA –20% –6.3% –11% 1.2%

Hypolimnion

2000

No Action 100 12.0 7.8 289 .002 .015 .016 .038 .60

Comanche South 100 12.0 7.8 285 .002 .014 .016 .035 .66

Percent change 0% 0% –1.4% 0% –6.7% 0% –7.9% 10%

No Action 100 12.0 7.8 289 .002 .015 .016 .038 .60

Joint Use Pipeline North 100 12.0 7.8 290 .003 .016 .016 .041 .55

Percent change 0% 0% .3% 50% 6.7% 0% 7.9% –8.3%

No Action 100 12.0 7.8 289 .002 .015 .016 .038 .60

Master Contract Only 100 12.0 7.8 286 .003 .014 .016 .034 .64

Percent change 0% 0% –1.0% 50% –6.7% 0% –11% 6.7%

Epilimnion

2001

No Action 100 11.3 8.3 246 .010 .083 .022 .122 .20

Comanche South 100 11.5 8.4 246 .010 .074 .022 .100 .24

Percent change 1.8% 1.2% 0% 0% –11% 0% –18% 20%

No Action 100 11.3 8.3 246 .010 .083 .022 .122 .20

Joint Use Pipeline North 100 11.2 8.1 248 .011 .084 .022 .187 .18

Percent change –.9% –2.4% .8% 10% 1.2% 0% 53% –10%

No Action 100 11.3 8.3 246 .010 .083 .022 .122 .20

Master Contract Only 100 11.7 8.5 246 .010 .066 .022 .093 .33

Percent change 3.5% 2.4% 0% 0% –20% 0% –24% 65%

Hypolimnion

2001

No Action 100 8.4 9.3 245 .010 .081 .022 .133 .20

Comanche South 92 9.3 8.8 245 .010 .076 .022 .138 .22

Percent change 11% –5.4% 0% 0% –6.2% 0% 3.8% 10%

No Action 100 8.4 9.3 245 .010 .081 .022 .133 .20

Joint Use Pipeline North 90 9.3 9.1 246 .010 .083 .022 .186 .18

Percent change 11% –2.2% .4% 0% 2.5% 0% 40% –10%

No Action 100 8.4 9.3 245 .010 .081 .022 .133 .20

Master Contract Only 98 10.5 8.4 245 .010 .069 .022 .130 .24

Percent change 25% –9.7% 0% 0% –15% 0% –2.3% 20%

Epilimnion

2002

No Action 100 9.0 8.1 271 .020 .092 .026 .466 .15

Comanche South 79 8.8 8.2 273 .020 .090 .026 .420 .15

Percent change –2.2% 1.2% .7% 0% –2.2% 0% –9.9% 0%

No Action 100 9.0 8.1 271 .020 .092 .026 .466 .15

Joint Use Pipeline North 74 8.6 8.3 267 .020 .093 .026 .455 .15

Percent change –4.4% 2.5% –1.5% 0% 1.1% 0% –2.4% 0%

No Action 100 9.0 8.1 271 .020 .092 .026 .466 .15

Master Contract Only 86 9.6 8.0 283 .019 .080 .026 .326 .17

Percent change 6.7% –1.2% 4.4% –5.0% –13% 0% –30% 13%

Hypolimnion

2002

No Action 100 -- -- -- -- -- -- -- --

Comanche South 36 -- -- -- -- -- -- -- --

Percent change NA NA NA NA NA NA NA NA

No Action 100 -- -- -- -- -- -- -- --

Joint Use Pipeline North 16 -- -- -- -- -- -- -- --

Percent change NA NA NA NA NA NA NA NA

No Action 100 -- -- -- -- -- -- -- --

Master Contract Only 56 -- -- -- -- -- -- -- --

Percent change NA NA NA NA NA NA NA NA
Appendixes 47

Appendix 7. Percent change between annual 85th percentile values for selected constituents and comparisons of the annual 

15th percentile values for dissolved oxygen concentrations in the epilimnion and hypolimnion at site 7B for cumulative-effects analyses 

for the Comanche South, Joint Use Pipeline North, and Master Contract Only scenarios as compared to the No Action scenario.

[N, nitrogen; P, phosphorus; °C, degrees Celsius; mg/L, milligrams per liter; μg/L, micrograms per liter; NA, not applicable; <, less than]

Water

year

Simulation

scenario

Percent of

annual

results

available

Water 

temperature

(°C)

Dissolved

oxygen

(mg/L)

Dissolved

solids

(mg/L)

Dissolved

ammonia

as N

(mg/L)

Dissolved 

nitrate

as N

(mg/L)

Total

phosphorus

as P

(mg/L)

Total

iron

(mg/L)

Chlorophyll-a

(μg/L)

Epilimnion

2000

No Action 100 25.2 5.6 294 0.006 0.016 0.016 0.006 1.11

Comanche South 100 25.2 5.7 290 .006 .010 .016 .022 1.10

Percent change 0% 1.8% –1.4% 0% –38% 0% 267% –.9%

No Action 100 25.2 5.6 294 .006 .016 .016 .006 1.11

Joint Use Pipeline North 100 25.2 5.7 294 .006 .014 .017 .010 1.10

Percent change 0% 1.8% 0% 0% –12% 6.3% 67% –.9%

No Action 100 25.2 5.6 294 .006 .016 .016 .006 1.11

Master Contract Only 100 25.2 5.7 290 .006 .011 .016 .008 1.13

Percent change 0% 1.8% –1.4% 0% –31% 0% 33% 1.8%

Hypolimnion

2000

No Action 100 18.4 <.1 295 .014 .009 .018 4.97 .82

Comanche South 100 18.9 <.1 291 .013 .009 .018 4.38 .81

Percent change 2.7% NA –1.4% –7.1% 0% 0% –12% –1.2%

No Action 100 18.4 <.1 295 .014 .009 .018 4.97 .82

Joint Use Pipeline North 100 19.2 <.1 295 .014 .010 .018 4.54 .82

Percent change 4.3% NA 0% 0% 11% 0% –8.7% 0%

No Action 100 18.4 <.1 295 .014 .009 .018 4.97 .82

Master Contract Only 100 18.6 <.1 293 .014 .009 .019 5.35 .81

Percent change 1.1% NA –.7% 0% 0% 5.6% 7.6% –1.2%

Epilimnion

2001

No Action 100 24.5 5.1 248 .006 .019 .018 .008 1.10

Comanche South 100 24.6 5.0 246 .007 .021 .018 .003 1.03

Percent change .4% –2.0% –.8% 17% 11% 0% –63% –6.4%

No Action 100 24.5 5.1 248 .006 .019 .018 .008 1.10

Joint Use Pipeline North 100 24.6 5.1 247 .006 .021 .018 .003 1.04

Percent change .4% 0% –.4% 0% 11% 0% –63% –5.5%

No Action 100 24.5 5.1 248 .006 .019 .018 .008 1.10

Master Contract Only 100 24.8 5.0 241 .007 .015 .017 .003 .93

Percent change 1.2% –2.0% –2.8% 17% –21% –5.6% –63% –15%

Hypolimnion

2001

No Action 100 20.6 .4 248 .012 .018 .018 .432 .15

Comanche South 100 20.3 <.1 249 .013 .019 .019 1.44 .15

Percent change –1.5% NA .4% 8.3% 5.6% 5.6% 233% 0%

No Action 100 20.6 .4 248 .012 .018 .018 .432 .15

Joint Use Pipeline North 100 20.3 .1 249 .013 .019 .019 1.16 .16

Percent change –1.5% –75% .4% 8.3% 5.6% 5.6% 168% 6.7%

No Action 100 20.6 .4 248 .012 .018 .018 .432 .15

Master Contract Only 100 20.1 <.1 248 .013 .018 .029 1.16 .16

Percent change –2.4% NA 0% 8.3% 0% 61% 169% 6.7%

Epilimnion

2002

No Action 100 24.6 5.1 288 .010 .016 .021 .003 1.27

Comanche South 100 24.7 5.2 290 .010 .020 .021 .003 1.24

Percent change .4% 2.0% .7% 0% 25% 0% 0% –2.4%

No Action 100 24.6 5.1 288 .010 .016 .021 .003 1.27

Joint Use Pipeline North 100 24.7 5.2 291 .009 .016 .021 .003 1.32

Percent change .4% 2.0% 1.0% –10% 0% 0% 0% 3.9%

No Action 100 24.6 5.1 288 .010 .016 .021 .003 1.27

Master Contract Only 100 24.6 5.5 282 .010 .013 .020 .001 1.11

Percent change 0% 7.8% –2.1% 0% –19% –4.8% –67% –13%

Hypolimnion

2002

No Action 100 19.2 <.001 269 .021 .009 .027 3.07 .29

Comanche South 100 17.6 <.001 265 .020 .009 .027 2.13 .27

Percent change –8.3% NA –1.5% –4.8% 0% 0% –31% –6.9%

No Action 100 19.2 <.001 269 .021 .009 .027 3.07 .29

Joint Use Pipeline North 100 18.4 <.001 267 .022 .010 .027 2.41 .27

Percent change –4.2% NA –.7% 4.8% 11% 0% –21% –6.9%

No Action 100 19.2 <.001 269 .021 .009 .027 3.07 .29

Master Contract Only 100 19.7 <.001 265 .025 .011 .025 3.96 .25

Percent change 2.6% NA –1.5% 19% 22% –5.6% 29% –14%
48 Simulated Effects of Proposed Arkansas Valley Conduit, Pueblo Reservoir, Southeastern Colorado

Appendix 8. Percent change between annual 85th percentile values for selected constituents and comparisons of the annual 15th 

percentile values for dissolved oxygen concentrations in the epilimnion and hypolimnion at site 3B for cumulative-effects analyses for 

the Comanche South, Joint Use Pipeline North, and Master Contract Only scenarios as compared to the No Action scenario.

[N, nitrogen; P, phosphorus; °C, degrees Celsius; mg/L, milligrams per liter; μg/L, micrograms per liter; --, summary statistic not calculated; NA, not applicable]

Water

year

Simulation

scenario

Percent of

annual

results

available

Water 

temperature

(°C)

Dissolved 

oxygen

(mg/L)

Dissolved

solids

(mg/L)

Dissolved

ammonia

as N

(mg/L)

Dissolved 

nitrate

as N

(mg/L)

Total

phosphorus

as P

(mg/L)

Total 

iron

(mg/L)

Chlorophyll-a

(μg/L)

Epilimnion

2000

No Action 100 23.0 6.0 299 .003 .033 .018 .094 1.80

Comanche South 100 23.0 6.0 295 .003 .032 .017 .108 1.74

Percent change 0% 0% –1.3% 0% –3.0% –5.6% 15% –3.3%

No Action 100 23.0 6.0 299 .003 .033 .018 .094 1.80

Joint Use Pipeline North 100 22.7 5.9 301 .004 .037 .018 .126 1.83

Percent change –1.3% –1.7% .7% 33% 12% 0% 34% 1.7%

No Action 100 23.0 6.0 299 .003 .033 .018 .094 1.80

Master Contract Only 100 23.0 6.0 295 .003 .030 .017 .106 1.78

Percent change 0% 0% –1.3% 0% –9.1% –5.6% 13% –1.1%

Hypolimnion

2000

No Action 100 22.4 4.9 304 .007 .037 .018 .450 1.52

Comanche South 100 22.5 4.9 300 .006 .033 .018 .449 1.43

Percent change .4% 0% –1.3% –14% –11% 0% –.2% –5.9%

No Action 100 22.4 4.9 304 .007 .037 .018 .450 1.52

Joint Use Pipeline North 100 22.3 4.9 304 .007 .038 .018 .466 1.48

Percent change –.4% 0% 0% 0% 2.7% 0% 3.6% –2.6%

No Action 100 22.4 4.9 304 .007 .037 .018 .450 1.52

Master Contract Only 100 22.5 4.9 301 .006 .032 .018 .434 1.42

Percent change –4% 0% –1.0% –14% –14% 0% –3.6% –6.6%

Epilimnion

2001

No Action 100 20.9 5.6 303 .020 .103 .025 .131 1.51

Comanche South 100 21.2 5.6 301 .019 .099 .025 .780 1.47

Percent change 1.4% 0% –.7% –5.0% –3.9% 0% 495% –2.6%

No Action 100 20.9 5.6 303 .020 .103 .025 .131 1.51

Joint Use Pipeline North 100 20.7 5.5 305 .020 .104 .025 .147 1.67

Percent change –1.0% –1.8% .7% 0% 1.0% 0% 12% 11%

No Action 100 20.9 5.6 303 .020 .103 .025 .131 1.51

Master Contract Only 100 21.3 5.5 295 .019 .098 .024 .683 1.41

Percent change 1.9% –1.8% –2.6% –5.0% –4.9% –4.0% 421% –6.6%

Hypolimnion

2001

No Action 100 20.6 5.4 282 .019 .103 .024 1.82 1.34

Comanche South 92 21.1 5.3 283 .019 .098 .024 1.52 .96

Percent change 2.4% –1.9% .4% 0% –4.9% 0% –16% –28%

No Action 100 20.6 5.4 282 .019 .103 .024 1.82 1.34

Joint Use Pipeline North 90 20.8 5.4 285 .019 .104 .024 1.70 1.40

Percent change 1% 0% 1.1% 0% 1.0% 0% –6.6% 4.5%

No Action 100 20.6 5.4 282 .019 .103 .024 1.82 1.34

Master Contract Only 98 20.9 5.2 290 .019 .094 .024 .890 .89

Percent change 1.5% –3.7% 2.8% 0% –8.7% 0% –51% –34%

Epilimnion

2002

No Action 100 17.2 6.2 360 .020 .099 .029 .880 .40

Comanche South 79 19.0 5.9 360 .020 .099 .029 .814 .37

Percent change 10% –4.8% 0% 0% 0% 0% –7.5% –7.5%

No Action 100 17.2 6.2 360 .020 .099 .029 .880 .40

Joint Use Pipeline North 74 16.3 6.4 360 .020 .099 .029 .827 .45

Percent change –5.2% 3.2% 0% 0% 0% 0% -6.0% 12%

No Action 100 17.2 6.2 360 .020 .099 .029 .880 .40

Master Contract Only 86 21.9 5.5 359 .020 .097 .030 .551 .62

Percent change 27% –11% –.3% 0% –2.0% 3.4% –37% 55%

Hypolimnion

2002

No Action 100 -- -- -- -- -- -- -- --

Comanche South 36 -- -- -- -- -- -- -- --

Percent change NA NA NA NA NA NA NA NA

No Action 100 -- -- -- -- -- -- -- --

Joint Use Pipeline North 16 -- -- -- -- -- -- -- --

Percent change NA NA NA NA NA NA NA NA

No Action 100 -- -- -- -- -- -- -- --

Master Contract Only 56 -- -- -- -- -- -- -- --

Percent change NA NA NA NA NA NA NA NA
Appendixes 49

Publishing support provided by:

Denver Publishing Service Center, Denver, Colorado

Raleigh Publishing Service Center, Raleigh, North Carolina

For more information concerning this publication, contact:

Director, USGS Colorado Water Science Center

Box 25046, Mail Stop 415

Denver, CO 80225

(303) 236-4882

Or visit the Colorado Water Science Center Web site at:

http://co.water.usgs.gov/

This publication is available online at:

http://pubs.usgs.gov/sir/2013/5119/
Ortiz—Simulated Effects of Proposed Arkansas Valley Conduit, Pueblo Reservoir, Southeastern Colorado—Scientific Investigations Report 2013–5119