U.S. GEOLOGICAL SURVEY

Water-Resources Investigations Report 00–4130

Trends in Precipitation and Streamflow

and Changes in Stream Morphology

in the Fountain Creek Watershed,

Colorado, 1939–99

By Robert W. Stogner, Sr.

Denver, Colorado

2000

Prepared in cooperation with the

TURKEY CREEK SOIL CONSERVATION DISTRICT,

EL PASO COUNTY SOIL CONSERVATION DISTRICT,

CENTRAL COLORADO SOIL CONSERVATION DISTRICT, and

PUEBLO COUNTY
U.S. DEPARTMENT OF THE INTERIOR

BRUCE BABBITT, Secretary

U.S. GEOLOGICAL SURVEY

Charles G. Groat, Director

The use of firm, trade, and brand names in this report is for identification purposes only and does

not constitute endorsement by the U.S. Geological Survey.

For additional information write to: Copies of this report can be purchased

U.S. Geological Survey

Information Services

Box 25286

Federal Center

Denver, CO 80225

from:

District Chief

U.S. Geological Survey

Box 25046, Mail Stop 415

Denver Federal Center

Denver, CO 80225–0046
CONTENTS III

CONTENTS

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

Introduction............................................................................................................................................................................ 2

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

Approach...................................................................................................................................................................... 2

Description of Study Area and General Land Use ................................................................................................................ 6

Precipitation........................................................................................................................................................................... 6

General Precipitation Characteristics........................................................................................................................... 6

Temporal Trends in Precipitation................................................................................................................................. 8

Synthesis of Precipitation Analysis ............................................................................................................................. 15

Streamflow ............................................................................................................................................................................. 15

Temporal Trends .......................................................................................................................................................... 17

Trends in High Streamflow Statistics................................................................................................................. 17

Instantaneous Peak Streamflow ............................................................................................................... 17

High Streamflow Percentiles ................................................................................................................... 19

Streamflow Duration................................................................................................................................ 21

Trends in Low Streamflow Statistics ................................................................................................................. 24

Low Streamflow Percentiles .................................................................................................................... 24

Streamflow Duration................................................................................................................................ 25

Spatial Trends .............................................................................................................................................................. 28

High Streamflow ................................................................................................................................................ 28

Low Streamflow................................................................................................................................................. 30

Relation between Precipitation and Streamflow.......................................................................................................... 32

Synthesis of Streamflow Analysis ............................................................................................................................... 34

Stream Morphology ............................................................................................................................................................... 36

Generalized Stream Channel Characteristics............................................................................................................... 36

Sediment Transport Capacity....................................................................................................................................... 37

Descriptive Assessment of Changes in Channel Morphology..................................................................................... 37

Summary and Conclusions .................................................................................................................................................... 41

Selected References ............................................................................................................................................................... 43

FIGURES

1. Map showing location of Fountain Creek watershed, streamflow and precipitation monitoring stations,

and river reaches......................................................................................................................................................... 3

2–14. Graphs showing:

2. Population of El Paso, Pueblo, and Teller Counties, 1890–1990, with projected year 2000 population........... 7

3. Annual precipitation, departure from annual mean precipitation, and cumulative departures from

annual mean precipitation at Ruxton Park and Colorado Springs ..................................................................... 9

4. Annual precipitation, departure from annual mean precipitation, and cumulative departures from

annual mean precipitation at Fountain and Pueblo ............................................................................................ 10

5. Distribution of precipitation at stations in and near the Fountain Creek watershed for period of

record, pre-1977, and post-1976 time periods ................................................................................................... 12

6. Total annual precipitation with estimated trend line for the period prior to 1977, 1977 to 1999,

and period of record ........................................................................................................................................... 13

7. Annual hydrograph of average mean-daily streamflow at Pinon, 1973 through 1999....................................... 16

8. Annual instantaneous peak streamflow at gaging stations in the Fountain Creek watershed,

1940–99.............................................................................................................................................................. 18

9. Magnitude of 7-, 14-, and 30-day high flows at gaging stations in the Fountain Creek watershed,

1940–99.............................................................................................................................................................. 22
IV CONTENTS

10. Magnitude of 7-, 14-, and 30-day low flows at gaging stations in the Fountain Creek watershed,

1940–99.............................................................................................................................................................. 26

11. Normalized high flow for selected reaches of Fountain and Monument Creeks, 1977 through 1999............... 29

12. Normalized low flow for selected reaches of Fountain and Monument Creeks, 1977 through 1999................ 31

13. Relation between cumulative average precipitation at four precipitation gages in the Fountain Creek

watershed and cumulative daily-mean streamflow at Pueblo, October 1959 through August 1997 ................. 33

14. Relation between cumulative average precipitation at four precipitation gages in the Fountain Creek

watershed and cumulative daily-mean streamflow at Pueblo, November through March and April

through October, 1959–97 ................................................................................................................................. 35

15. Photograph showing view looking south at the Overton Road bridge and edge of high terrace on

April 26, 1999. ........................................................................................................................................................... 39

16. Aerial photograph of Fountain Creek at the Overton Road bridge in September 1991 and periodic

changes in the general location of the high terrace from 1955 and 1970 through 1999 after the

April 1999 flood ......................................................................................................................................................... 40

17. Photograph showing streambank erosion and sediment deposition on the flood plain of Fountain Creek................ 41

TABLES

1. Precipitation stations in and near the Fountain Creek watershed and period of record .......................................... 4

2. Streamflow-gaging stations with 23 or more years of continuous record, period of record for each station,

and drainage area..................................................................................................................................................... 4

3. Range in magnitude of daily precipitation at precipitation-monitoring stations in and near the Fountain

Creek watershed ...................................................................................................................................................... 8

4. Seasonal distribution of daily precipitation of indicated magnitude at precipitation-monitoring stations in

and near the Fountain Creek watershed .................................................................................................................. 8

5. Frequency of receiving precipitation of 0.01 inch or greater during a 24-hour period at locations in the

Fountain Creek watershed for water year 1960 through the end of record, 1960 through water year 1976

and 1977 through the end of record ........................................................................................................................ 11

6. Kendall trend analysis of annual precipitation for the period of record, and pre-1977 and post-1976 time

periods ..................................................................................................................................................................... 14

7. Summary of Kendall trend analysis of spring precipitation.................................................................................... 14

8. Wilcoxon rank sum test of differences between mean annual precipitation during the pre-1977 and

post-1976 time periods............................................................................................................................................ 15

9. Kendall trend analysis of annual instantaneous peak streamflow for the indicated period of record,

and pre-1976 and post-1975 time periods............................................................................................................... 19

10. Summary of five largest streamflow events on Fountain Creek at Pueblo, Colorado, and magnitude and

general location of precipitation.............................................................................................................................. 19

11. Kendall trend analysis of 70th, 90th, and 100th percentiles of streamflow for the respective periods of

record, pre-1977, and post-1976 time periods ........................................................................................................ 20

12. Kendall trend analysis of 7-, 14-, and 30-day high daily-mean streamflow duration ............................................. 23

13. Kendall trend analysis for 0th, 10th, and 30th percentiles of streamflow for the respective periods of

record, pre-1977 and post-1976 time periods ......................................................................................................... 25

14. Kendall trend analysis of 7-, 14-, and 30-day low streamflow duration ................................................................. 27

15. Kendall trend analysis for 70th, 90th, and 100th percentiles of normalized streamflow for the post-1976

time period .............................................................................................................................................................. 30

16. Kendall trend analyses for the 0th, 10th, and 30th percentiles of normalized streamflow for the post-1976

time period .............................................................................................................................................................. 32
CONTENTS V

CONVERSION FACTORS AND VERTICAL DATUM

Sea level: In this report, “sea level” refers to the National Geodetic Vertical Datum of 1929 (NGVD of 1929)—a geodetic datum derived

from a general adjustment of the first-order level nets of both the United States and Canada, formerly called Sea Level Datum of 1929.

Multiply By To obtain

cubic foot per second (ft3/s) 0.02832 cubic meter per second

foot (ft) 0.3048 meter

inch 25.4 millimeters

inch per year (in/yr) 25.4 millimeters per year

mile 1.609 kilometer

square mile (mi2) 2.590 square kilometer
Abstract 1

Trends in Precipitation and Streamflow and

Changes in Stream Morphology in the Fountain

Creek Watershed, Colorado, 1939–99

By Robert W. Stogner, Sr.

Abstract

The Fountain Creek watershed, located in

and along the eastern slope of the Front Range

section of the southern Rocky Mountains, drains

approximately 930 square miles of parts of Teller,

El Paso, and Pueblo Counties in eastern Colorado.

Streamflow in the watershed is dominated by

spring snowmelt runoff and storm runoff during

the summer monsoon season. Flooding during

the 1990’s has resulted in increased streambank

erosion. Property loss and damage associated with

flooding and bank erosion has cost area residents,

businesses, utilities, municipalities, and State and

Federal agencies millions of dollars. Precipitation

(4 stations) and streamflow (6 stations) data,

aerial photographs, and channel reconnaissance

were used to evaluate trends in precipitation and

streamflow and changes in channel morphology.

Trends were evaluated for pre-1977, post-1976,

and period-of-record time periods.

Analysis revealed the lack of trend in

total annual and seasonal precipitation during

the pre-1977 time period. In general, the analysis

also revealed the lack of trend in seasonal precipitation for all except the spring season during the

post-1976 time period. Trend analysis revealed a

significant upward trend in long-term (period of

record) total annual and spring precipitation data,

apparently due to a change in total annual precipitation throughout the Fountain Creek watershed.

During the pre-1977 time period, precipitation

was generally below average; during the post1976 time period, total annual precipitation

was generally above average. During the post1976 time period, an upward trend in total annual

and spring precipitation was indicated at two

stations. Because two of four stations evaluated

had upward trends for the post-1976 period and

storms that produce the most precipitation are

isolated convection storms, it is plausible that

other parts of the watershed had upward precipitation trends that could affect trends in streamflow.

Also, because of the isolated nature of convection

storms that hit some areas of the watershed

and not others, it is difficult to draw strong

conclusions on relations between streamflow

and precipitation.

Trends in annual instantaneous peak

streamflow, 70th percentile, 90th percentile,

maximum daily-mean streamflow (100th percentile), 7-, 14-, and 30-day high daily-mean streamflow duration, minimum daily-mean streamflow

(0th percentile), 10th percentile, 30th percentile,

and 7-, 14-, 30-day low daily-mean streamflow

duration were evaluated. In general, instantaneous

peak streamflow has not changed significantly

at most of the stations evaluated. Trend analysis

revealed the lack of a significant upward trend in

streamflow at all stations for the pre-1977 time

period. Trend tests indicated a significant upward

trend in high and low daily-mean streamflow

statistics for the post-1976 period. Upward trends

in high daily-mean streamflow statistics may be

an indication that changes in land use within the

watershed have increased the rate and magnitude

of runoff. Upward trends in low daily-mean
2 Trends in Precipitation and Streamflow and Changes in Stream Morphology in the Fountain Creek Watershed,

Colorado, 1939–99

streamflow statistics may be related to changes

in water use and management. An analysis of

the relation between streamflow and precipitation

indicated that changes in water management have

had a marked effect on streamflow.

Observable change in channel morphology and changes in distribution and density of

vegetation varied with magnitude, duration,

and frequency of large streamflow events, and

increases in the magnitude and duration of low

streamflows. Although more subtle, low streamflows were an important component of day-to-day

channel erosion. Substantial changes in channel

morphology were most often associated with

infrequent large or catastrophic streamflow

events that erode streambed and banks, alter

stream course, and deposit large amounts of

sediment in the flood plain.

INTRODUCTION

The Fountain Creek watershed, in and along

the eastern slope of the Front Range section of the

southern Rocky Mountains, drains approximately

930 mi2

 of parts of Teller, El Paso, and Pueblo

Counties in eastern Colorado (fig. 1). Land-surface

elevation varies from 14,110 ft at the summit of Pike's

Peak to 4,640 ft at the confluence of Fountain Creek

and the Arkansas River.

Over the past several years, landowners,

farmers, resource managers, municipal, county,

local, and Federal agencies have expressed concern

that possible increases in streamflow have adversely

affected channel stability, resulting in substantial

bank erosion along Fountain Creek. Bank erosion

has resulted in property losses and damage to roads,

bridges, and other structures along the creek. Damages

associated with floods are costing property owners

and local and State governments millions of dollars to

reclaim, replace, and (or) repair affected property and

structures (National Oceanographic and Atmospheric

Administration, 1999).

In 1999, the U.S. Geological Survey (USGS), in

cooperation with the Turkey Creek Soil Conservation

District, El Paso County Soil Conservation District,

Central Colorado Soil Conservation District, and

Pueblo County, began a study to evaluate precipitation and streamflow trends and changes in stream

morphology in the Fountain Creek watershed.

Purpose and Scope

This report describes trends in precipitation and

trends in streamflow in the Fountain Creek watershed

and presents a qualitative assessment of changes in

channel morphology of selected reaches of Fountain

Creek downstream from Colorado Springs, Colorado.

Trends in precipitation were evaluated for four stations

in or near the Fountain Creek drainage basin for the

period of record (fig. 1, table 1). Selection of these

stations was based on length of record and location

in or near the Fountain Creek watershed. Trends

in streamflow were evaluated for the period of record

at six streamflow-gaging stations (fig. 1, table 2).

The six streamflow-gaging stations were selected

on the basis of length of streamflow record and location. The length of continuous record varied from 23

to 40 years. In addition to continuous record, several

stations had historical data, pre-dating the period of

continuous record, which also were included in the

evaluation of trends in streamflow. Changes in channel

morphology were evaluated using aerial photographs

of Fountain Creek downstream from Colorado Springs

taken between 1947 and 1999 and field reconnaissance

during 1999.

For the purpose of this study, the existence or

lack of trend was determined by the reported significance level as determined by the statistical test used.

Statistical significance was defined as highly significant, significant, and moderately significant, with

corresponding p-values of less than 0.01, 0.05, and

0.1, respectively. A nonsignificant trend was indicated

when the p-value was greater than 0.1. The estimated

slope of the trend, or rate of change per unit time

(trend slope estimate), was compared to trend slope

estimates of other stations.

Approach

Daily, seasonal, and annual precipitation data

from four stations in and near the Fountain Creek

watershed (fig. 1) were used to evaluate spatial and

temporal variations and trends in precipitation. Annual

precipitation statistics were computed for each water

year. A water year extends from October 1 through

September 30 of the following year and is identified

by the year in which it ends. Complete streamflow

records at some stations were not available until 1977;

therefore, precipitation data were divided into pre1977 and post-1976 time periods to (1) evaluate
INTRODUCTION 3

COLORADO

Pueblo

Grand Junction

Colorado Springs

Denver

U.S. Geological Survey streamflow gage and 

 station identifier

Precipitation gage and station identifier

Fountain Creek watershed boundary

R1 Morphological assessment reach and reach number

EXPLANATION

Base modified by Denver Water Board, 1998

From U.S. Geological Survey Digital Line Graphs, 100,000, 1981-1983

Roads and cities from Colorado Department of Transportation, 50,000, 1998.

Albers Equal-Area projection

Standard parallels 37°30' N and 40°30' N Central meridian 105°30' W

PUEBLO COUNTY

EL PASO COUNTY

TELLER COUNTY

COLORADO SPRINGS

PUEBLO

Fountain Creek

Monument Creek

Fountain Creek

Arkansas River

Pikes Peak

Ruxton Park

Colorado Springs 

Fountain

Pueblo

Pikeview

Near CO Spgs

Nevada 

Street

Security

Pinon

Pueblo

MONUMENT

PALMER LAKE

WOODLAND 

PARK

R4

R2

R1

R3

Cottonwood Creek

Fort Carson 

Military Reservation

MANITOU 

SPRINGS

38°52'30"

38°30'

105° 104°30'

STUDY AREA

0 5 10 15 MILES

0 5 10 15 KILOMETERS

Figure 1. Location of Fountain Creek watershed, streamflow and precipitation monitoring stations, and river

reaches.
4 Trends in Precipitation and Streamflow and Changes in Stream Morphology in the Fountain Creek Watershed,

Colorado, 1939–99

whether changes in precipitation occurred within or

between these two time periods, and (2) make general

comparisons between trends in precipitation and

trends in streamflow. Kendall trend and Wilcoxon rank

sum tests were used to evaluate temporal trends for the

period of record and compare precipitation characteristics for pre-1977 and post-1976 periods. The Kendall

trend test is a nonparametric test used to evaluate the

significance of a monotonic trend in a variable over

time; a monotonic trend exists if variable x generally

increases or decreases as variable y (time) increases

(Helsel and Hirsch, 1995). It was used to evaluate

trends in total annual precipitation for the period

of record and for the pre-1977 and post-1976 time

periods. The Wilcoxon rank sum test is also a nonparametric test and is used to compare the distribution of two populations (Ott, 1993). In this report, the

Wilcoxon rank sum test was used to compare total

annual and seasonal precipitation during the pre-1977

period to total annual and seasonal precipitation

during the post-1976 period. In addition, precipitation

data were evaluated to determine long-term mean,

annual departure from mean, and cumulative departure

from mean.

Streamflow at gaging stations is computed

after developing the relation of stage to streamflow

for a particular location (Buchanan and Somers, 1968;

Carter and Davidian, 1968; Kennedy, 1983, 1984).

At a typical USGS streamflow-gaging station, stream

stage, or the level of water in the stream, is recorded

at periodic intervals. Based on the defined relation

between stage and streamflow, recorded stream stage

is converted to streamflow.

Trends in streamflow were evaluated using the

Kendall trend test. Streamflow data from six gaging

stations in the Fountain Creek watershed (table 1,

fig. 1) were evaluated for trends in the following

streamflow statistics: annual instantaneous peak

streamflow; annual maximum (100th percentile), 90th,

70th, 30th, 10th, and annual minimum (0th percentile)

Table 1. Precipitation stations in and near the Fountain Creek watershed and period of record

[AP, airport; WSO, Weather Service Office; mm, month; yy, year]

Colorado Climate

Center station number Station name Station identifierused in this report

Period of record

mm/yy to mm/yy

Elevation above

sea level

( in feet)

51778 Colorado Springs WSO Colorado Springs 08/48 to 09/99 6,170

53063 Fountain Fountain 08/48 to 09/97 5,550

56704 Pueblo WSO AP Pueblo 07/54 to 09/99 4,640

57309 Ruxton Park Ruxton Park 09/59 to 09/99 9,050

Table 2. Streamflow-gaging stations with 23 or more years of continuous record, period of record for each station, and

drainage area

[mi2, square miles; mm, month; yy, year]

U.S. Geological Survey

station number Station name

Station

identifier used

in this report

Period of record

(mm/yy to mm/yy)

Drainage

area

(mi2)

07104000 Monument Creek at Pikeview, CO Pikeview 10/38 to 09/49,

01/76 to 09/99

204

07103700 Fountain Creek near Colorado Springs, CO Near CO Spgs 04/58 to 09/99 103

07105500 Fountain Creek at Nevada Street at Colorado

Springs, CO

Nevada Street 10/21 to 09/24,

01/76 to 09/99

392

07105800 Fountain Creek at Security, CO Security 10/64 to 09/99 495

07106300 Fountain Creek at Pinon, CO Pinon 04/73 to 09/99 849

07106500 Fountain Creek at Pueblo, CO Pueblo 01/22 to 09/25,

10/40 to 09/65,

02/71 to 09/99

926
INTRODUCTION 5

daily-mean streamflow; and annual 7-, 14-, and 30-day

high daily-mean streamflow duration and annual 7-,

14-, and 30-day low daily-mean streamflow duration.

The annual instantaneous peak streamflows were

derived from the single highest recorded stream stage

during a given water year. Daily-mean streamflow was

computed by averaging all the periodic computed

instantaneous streamflows over a day. Mean-daily

streamflow was computed by averaging daily-mean

streamflow for days of consecutive years of data (for

example, October 1, 1978, October 1, 1979, and so

on). Annual streamflow statistics were computed by

sorting and ranking the daily-mean streamflows. The

annual minimum (0th percentile) equals the minimum

computed daily-mean streamflow during a year; the

annual maximum (100th percentile) equals the

maximum computed daily-mean streamflow during a

year. Intermediate percentiles, 10th, 30th, 70th, and

90th, are equivalent to the 36th, 109th, 255th, and

328th annual daily-mean streamflow values when

sorted from smallest to largest. The n-percentile indicates that n percent of the annual daily-mean streamflow is below a given streamflow, or (100 minus n)

percent is above it. The 7-, 14-, and 30-day high and

low daily-mean streamflow duration statistics were

computed by averaging daily mean streamflow for 7,

14, and 30 consecutive days. This procedure, termed

moving average (Helsel and Hirsch, 1995), was

used for every day of the water year, meaning that,

the average daily-mean streamflow for 7, 14, and

30 consecutive days was computed for October 1st,

and then for October 2d, 3d, and so on.

Time periods for the streamflow trend analyses

varied because of differences in data requirements and

availability for some of the various streamflow statistics evaluated. Trends in annual instantaneous peak

streamflow were evaluated for the period of record at

each station and for pre-1976 and post-1975 time

periods. This break point was selected because some

stations were not operational until January of 1976

and annual instantaneous peak streamflow data were

not available until the spring of 1976. Computation

of streamflow percentiles and streamflow-duration

statistics required continuous annual record; therefore,

trend analyses of streamflow percentiles and flow

duration were evaluated for respective periods of

continuous record at each station and for pre-1977

and post-1976 time periods. Annual streamflow

statistics were computed for each water year.

Spatial trends in selected streamflow statistics

were evaluated for the post-1976 time period. Differences in streamflow for five river reaches were normalized by the contributing drainage area. Evaluation of

trends in normalized differences in high daily-mean

streamflow statistics identify reaches within which

hydrologic responses (such as rainfall runoff) may be

different, may have changed as a result of changes in

precipitation, or may have been altered as a result of

human activities. Human activities that may alter the

hydrologic response of a reach include changing land

use from natural, pervious or semi-pervious surface

to an impervious surface; changing vegetative cover;

or concentrating and (or) rerouting surface runoff by

constructing storm drains. Additionally, evaluation

of trends in normalized differences in low streamflow

statistics provide information related to changes in

water management such as changes in discharge from

wastewater-treatment plants, changes in irrigation

return flows, and changes in tributary flow that occur

within the stream reaches.

The relation between streamflow and precipitation was evaluated using a double-mass curve

(Searcy and Hardison, 1960). In a double-mass curve,

the cumulation of one variable plotted against the

cumulation of another variable will result in a straight

line so long as the data are proportional (Searcy and

Hardison, 1960). A change in the slope of the doublemass curve indicates that the relation between the two

variables has changed. This analysis compared cumulative average daily precipitation from four precipitation gages to cumulative daily-mean streamflow at the

Pueblo station (fig. 1). The average precipitation was

used to smooth out spatial variation in precipitation.

Aerial photography from different time periods,

field reconnaissance, and topographic maps were used

to determine geomorphic characteristics and evaluate

changes in channel morphology along selected reaches

of Fountain Creek (fig. 1). Periodic aerial photographs

were used to characterize flood-plain vegetation

patterns, estimate channel width, and determine

channel location and sinuosity. This information was

used to relate large streamflow events to changes in

flood-plain characteristics and channel location as a

result of streambed and bank erosion. Photographs

selected for the analysis of changes in channel

morphology were taken in 1947, 1955, 1965, 1970,

1980, 1991, and 1999.
6 Trends in Precipitation and Streamflow and Changes in Stream Morphology in the Fountain Creek Watershed,

Colorado, 1939–99

Field reconnaissance was used to characterize

erosion patterns, which may be causing the changes

observed in channel location and flood-plain vegetation characteristics. Field reconnaissance was

conducted during April and May of 1999, prior to

and during the 1999 flood, and during September

and October 1999, when streambanks were visible.

DESCRIPTION OF STUDY AREA AND

GENERAL LAND USE

Land use within the Fountain Creek watershed

includes forests, urban areas, military reservations,

agriculture, and rangeland. Forested lands are located

predominantly in the northwestern mountainous part

of the watershed. The major urban center in the watershed is the Colorado Springs metropolitan area that

includes Colorado Springs and several smaller

communities in El Paso County. This metropolitan

area is located in the north-central part of the watershed. Of the three counties encompassing the watershed, El Paso County had the greatest economic

growth and population increase (fig. 2). Between

1890 and 1950, the population of Pueblo and El Paso

Counties increased at similar rates of about 900 people

per year. Between 1950 and 1990, the population

of El Paso County increased at a rate of about

8,000 people per year. Population projections for

the year 2000 indicate this rate has increased to

about 11,000 people per year during the 1990’s.

Between 1960 and 1990, population growth in Pueblo

County was relatively flat. Population projections for

the year 2000 indicate the rate of growth during the

1990’s has increased to about 1,600 people per year.

From 1900 through 1930, the population of Teller

County decreased at an annual rate of about 600

people per year. The population of Teller County

increased during the 1930’s, but declined during the

1940’s and 1950’s. Since 1970, the population of

Teller County has increased at a rate of about 300

people per year. This information is available at

http://www.ancestry.com/free/censtats/cocens.htm

(accessed 07/18/00). A small portion of the watershed

at and upstream from the confluence of Fountain

Creek and the Arkansas River is within the urban area

of the city of Pueblo. Agriculture and rangeland are

located predominantly south and east of Colorado

Springs. Agriculture is common along the alluvial

valley from Fountain to Pueblo and relies heavily

on water diverted from Fountain Creek. A large

expanse of rangeland is included within the boundaries of the military reservation at Fort Carson located

just south of Colorado Springs, west of Interstate 25

and Fountain Creek to just northwest of Pueblo

(fig. 1).

PRECIPITATION

Analysis of spatial distribution and temporal

trends in precipitation is constrained by the sparse

distribution of long-term precipitation-monitoring

stations in the watershed. Variations in the frequency

of daily precipitation, seasonal distribution, seasonal

and annual precipitation at four stations were evaluated. Seasonal and annual precipitation data were evaluated for the entire period of record to evaluate longterm trends and were divided into pre-1977 and post1976 time periods to be consistent with existing

streamflow record.

General Precipitation Characteristics

Climate within the watershed is broadly characterized as semiarid temperate continental. However, it

can vary from alpine arctic to semiarid, depending on

elevation and proximity to the Front Range (Hansen

and others, 1978). Depending on the precipitation

station, between about 40 and 60 percent of daily

precipitation that occurs is 0.1 inch or less in magnitude. Between about 70 and 80 percent of daily precipitation that occurs in the region is less than or equal to

0.25 inch (table 3). Daily precipitation of magnitude

0.25 inch or greater occurs most frequently between

July and September (table 4). Of the total number of

daily precipitation events that occurred during July

through September, between 25.2 and 34.1 percent

were greater than 0.25 inch in magnitude. Many of the

precipitation events during the summer are convection

storms driven by the inflow of monsoon moisture from

the southwest (Giannasca, 1999). Convection storms

are generally strong, isolated events that occur during

the late afternoon and early evening.

Annual precipitation generally decreases with

distance from the headwaters of the watershed and as

elevation decreases. The Ruxton Park station (fig. 1)

receives more precipitation than the Colorado Springs

station. Total annual precipitation at the Colorado

Springs station (fig. 3) generally is equivalent to total

annual precipitation at the Fountain station (fig. 4).
PRECIPITATION 7

550,000

50,000

500,000450,000400,000350,000300,000250,000200,000150,000100,000

POPULATION

0

1880 1900 1920 1940

YEAR

2020 1960 1980 2000

Projected year 2000 population

Projected year 2000 population

El Paso County

Pueblo County

Teller County

Figure 2. Population of El Paso, Pueblo, and Teller Counties, 1890–1990, with projected year 2000 population.
8 Trends in Precipitation and Streamflow and Changes in Stream Morphology in the Fountain Creek Watershed,

Colorado, 1939–99

Total annual precipitation at the Colorado Springs

and Fountain stations generally are greater than total

annual precipitation at the Pueblo station.

During the respective periods of record,

recorded annual precipitation was variable from year

to year at all stations (figs. 3 and 4). The Ruxton Park

station consistently received the most precipitation

annually, reporting a mean annual precipitation of

24.5 inches. The reporting station at the Pueblo

station received the least rainfall annually, reporting

a mean annual precipitation of 11.9 inches.

Temporal Trends in Precipitation

Temporal changes in precipitation characteristics were analyzed. The analysis revealed no appreciable difference in the percentage of days with

precipitation greater than or equal to 0.01 inch

(table 5) during the post-1976 time period compared

to the pre-1977 time period. Differences in the

frequency distribution of daily precipitation between

the pre-1977 and post-1976 time periods compared

to the entire period of record were slight (fig. 5).

Table 3. Range in magnitude of daily precipitation at precipitation-monitoring stations in and near the Fountain Creek

watershed

Magnitude

Precipitation monitoring station name

Colorado Springs Fountain Pueblo Ruxton Park

Percentage of daily precipitation values less than or equal to indicated magnitude

0.10 57.2 42.9 57.5 40.6

0.25 78.7 69.0 79.1 70.7

0.50 90.9 86.4 91.9 87.6

0.75 95.3 92.6 95.6 94.1

1.00 97.3 95.7 98.3 96.8

2.00 99.5 99.3 99.8 99.4

3.00 99.9 99.8 100.0 99.9

4.00 100.0 99.9 100.0 100.0

5.00 100.0 100.0 100.0 100.0

6.00 100.0 100.0 100.0 100.0

Table 4. Seasonal distribution of daily precipitation of indicated magnitude at precipitation-monitoring stations in and near the

Fountain Creek watershed

[≤, less than or equal to; >, greater than]

Magnitude

(inches)

October–March April–June July–September

Number of

events during

period of record

Percentage

of events

Number of

events during

period of record

Percentage

of events

Number of

events during

period of record

Percentage

of events

Colorado Springs

≤0.25 1,342 29.2 736 16.0 1,535 33.4

>0.25 176 3.8 264 5.8 540 11.8

Fountain

≤0.25 688 22.4 658 21.4 819 26.7

>0.25 165 5.4 316 10.3 424 13.8

Pueblo

≤0.25 1,005 31.8 709 22.4 809 25.6

>0.25 156 4.9 209 6.6 273 8.6

Ruxton Park

≤0.25 1,071 25.7 785 18.9 1,084 26.1

>0.25 315 7.6 386 9.3 520 12.5
PRECIPITATION 9

0

1940

604020

ANNUAL PRECIPITATION, IN INCHES

1950 1960 1970 1980 1990

Ruxton Park

Mean 24.5

2000

1940 2000 1950 1960 1970 1980 1990

-10

20

0

10

DEPARTURE FROM ANNUAL

MEAN PRECIPITATION, IN INCHES

1940 2000 1950 1960 1970 1980 1990 0

504020

2000 1940 1950 1960 1970 1980 1990

20

-10

0

10

1940 2000 1950 1960 1970 1980 1990

WATER YEAR

-60

20

-20-40

Colorado Springs

Ruxton Park Colorado Springs

Colorado Springs

Mean 16.4

2000 1940 1950 1960 1970 1980 1990

WATER YEAR

-60

20

-20-40

0

CUMULATIVE DEPARTURE FROM

ANNUAL MEAN PRECIPITATION, IN INCHES Ruxton Park

0

Figure 3. Annual precipitation, departure from annual mean precipitation, and cumulative departures from annual mean precipitation at Ruxton Park and Colorado

Springs.
10 Trends in Precipitation and Streamflow and Changes in Stream Morphology in the Fountain Creek Watershed,

Colorado, 1939–99

Fountain

Fountain

Pueblo

Fountain Pueblo

Pueblo

1940

302010

ANNUAL PRECIPITATION, IN INCHES

1940

-10

1510

-5

DEPARTURE FROM ANNUAL

MEAN PRECIPITATION, IN INCHES

1940

-60

20

-20-40

CUMULATIVE DEPARTURE FROM

ANNUAL MEAN PRECIPITATION, IN INCHES

0

1950 1960 1970 1980 1990

2000 1950 1960 1970 1980 1990

0

1940

302010

2000

2000 1950 1960 1970 1980 1990

WATER YEAR

1950

1950 1960 1970

-10

15

-5

50

10

1950 1960

-60

20

-20-40

0

Mean 15.7

2000 1980 19902000 1970 1980 1990

WATER YEAR

2000 1960 1970 1980 1990

Mean 11.9

500

Figure 4. Annual precipitation, departure from annual mean precipitation, and cumulative departures from annual mean precipitation at Fountain and Pueblo.
PRECIPITATION 11

Trend estimates for the period of record were

computed for all stations (fig. 6). Trend tests indicated

statistically significant (p < 0.05) upward trends in

total annual precipitation over the total period of

record at the Colorado Springs and Fountain stations

(fig. 6, table 6), and moderately significant upward

trends in total annual precipitation at the Ruxton Park

and Pueblo stations (fig. 6, table 6).

Trend analysis was also done on the precipitation data for the pre-1977 and post-1976 time periods.

During the pre-1977 period, all stations generally

recorded below-average total annual precipitation and

cumulative departures from the mean annual precipitation generally were increasingly negative (figs. 3 and

4). During the post-1976 period, all stations generally

recorded above-average total annual precipitation

(figs. 3 and 4). Kendall trend analysis revealed no

significant trends in total annual precipitation at any

station for the pre-1977 time period, and the Colorado

Springs and Fountain stations for the post-76 time

period. Kendall trend analysis revealed a moderately

significant upward trend at the Pueblo station, and

significant upward trend in total annual precipitation

at the Ruxton Park station for the post-1976 period

(fig. 6, table 6). The indication of significant trends at

some stations and not others is probably a result of

storms that hit some areas but not others, which makes

it difficult to draw strong conclusions on relations

between precipitation and streamflow at different

stations.

Daily precipitation data were divided into

seasons to evaluate seasonal trends; October to

December – fall, January to March – winter, April to

June – spring, and July to September – summer. With

the exception of summer precipitation for the period

1949 – 97 at the Fountain station (p = 0.0018), trend

test revealed no significant trend in seasonal precipitation during the fall, winter, and summer for the period

of record, the pre-1977 period, or the post-1976

period. Kendall trend tests revealed highly significant

to significant upward trends in spring precipitation at

the Ruxton Park, Colorado Springs, and Pueblo

stations for the period of record and moderately

significant trends in spring precipitation at the Ruxton

Park and Pueblo stations in the post-1976 time period

(table 7). Trends in annual precipitation at the Ruxton

Park and Pueblo stations (table 6) are a function of

trends in springtime precipitation.

Table 5. Frequency of receiving precipitation of 0.01 inch or greater during a 24-hour period at locations in the Fountain

Creek watershed for water year 1960 through the end of record, 1960 through water year 1976 and 1977 through the end

of record

[<, less than; ≥, greater than or equal to]

Precipitation

Colorado Springs Fountain Pueblo Ruxton Park

Number of

precipitation

events

Percentage

of the total

number of

precipitation

events

Number of

precipitation

events

Percentage

of the total

number of

precipitation

events

Number of

precipitation

events

Percentage

of the total

number of

precipitation

events

Number of

precipitation

events

Percentage

of the total

number of

precipitation

events

Water year 1960–end of record

<0.01 10,237 74 10,903 79 11,051 80 9,797 71

≥0.01 3,451 25 2,334 17 2,615 19 4,003 29

Missing 191 1 642 5 213 2 79 1

Water years 1960–76

<0.01 4,741 76 5,124 83 5,078 82 4,449 72

≥0.01 1,465 24 949 15 1,132 18 1,749 28

Missing 4 0 137 2 0 0 12 0

1977–end of record

<0.01 6,047 72 5,779 75 6,543 78 5,861 70

≥0.01 2,167 26 1,385 18 1,643 20 2,420 29

Missing 187 2 505 7 213 2 119 1
12 Trends in Precipitation and Streamflow and Changes in Stream Morphology in the Fountain Creek Watershed,

Colorado, 1939–99

0

70605040302010

PERCENT

EXPLANATION

0.10

to

0.01

0.25

to

0.11

0.50

to

0.26

0.75

to

0.51

1.00

to

0.76

2.00

to

1.01

3.00

to

2.01

4.00

to

3.01

5.00

to

4.01

greater

or

5.01

DAILY PRECIPITATION, IN INCHES

Fountain Pueblo

0

70605040302010

Period of record pre-1977 post-1976

0.10

to

0.01

0.25

to

0.11

0.50

to

0.26

0.75

to

0.51

1.00

to

0.76

DAILY PRECIPITATION, IN INCHES

2.00

to

1.01

3.00

to

2.01

4.00

to

3.01

5.00

to

4.01

greater

or

5.01

0.10

to

0.01

0.25

to

0.11

0.50

to

0.26

0.75

to

0.51

1.00

to

0.76

2.00

to

1.01

3.00

to

2.01

4.00

to

3.01

5.00

to

4.01

greater

or

5.01 0

70605040302010

Ruxton Park Colorado Springs

0.10

to

0.01

0.25

to

0.11

0.50

to

0.26

0.75

to

0.51

1.00

to

0.76

2.00

to

1.01

3.00

to

2.01

4.00

to

3.01

5.00

to

4.01

greater

or

5.01 0

70605040302010

PERCENT

Figure 5. Distribution of precipitation at stations in and near the Fountain Creek watershed for period of record, pre-1977, and post-1976 time periods.
PRECIPITATION 13

1940 2000 1950 1960 1970 1980 1990 5

40353025201510

TOTAL ANNUAL PRECIPITATION, IN INCHESRuxton Park 1960-99, mean = 24.5, significance 0.09 1960-76, mean = 23.5, significance 1.00 1977-99, mean = 25.3, significance 0.01 Annual total

1940 2000 1950 1960 1970 1980 1990 5

40353025201510

Colorado Springs

1949-99, mean = 16.4, significance 0.0091949-76, mean = 14.8, significance 0.60

1977-99, mean = 18.3, significance 0.42Annual total

1940 2000 1950 1960 1970 1980 1990

WATER YEAR

5

40353025201510

TOTAL ANNUAL PRECIPITATION, IN INCHES

Fountain

1949-97, mean = 15.7, significance 0.0051949-76, mean = 13.7, significance 0.931977-97, mean = 19.1, significance 1.00Annual total

1940 2000 1950 1960 1970 1980 1990

WATER YEAR

5

40353025201510

Pueblo

1955-99, mean = 11.9, significance 0.061955-76, mean = 11.2, significance 0.311977-99, mean = 12.7, significance 0.08

Annual total

Figure 6. Total annual precipitation with estimated trend line for the period prior to 1977, 1977 to 1999, and period of record.
14 Trends in Precipitation and Streamflow and Changes in Stream Morphology in the Fountain Creek Watershed,

Colorado, 1939–99

The Wilcoxon rank-sum test was used to evaluate whether the mean precipitation during the periods

prior to 1977 and after 1976 were different. The

Wilcoxon rank-sum test revealed moderately significant differences in mean precipitation between the two

periods at the Pueblo station and highly significant

differences between the two periods at the Colorado

Springs and Fountain stations (table 8). This test also

indicated no significant differences in mean precipitation between the two periods at the Ruxton Park

station. Although tests revealed differences in the

mean precipitation for the periods prior to and since

the mid-1970’s, the distribution in the magnitude of

precipitation events during these time periods was

similar (fig. 5). Therefore, differences between the two

periods are not a result of more rain during any given

day but more days with “typical” rainfall.

The Wilcoxon rank-sum test was also used to

evaluate differences in seasonal precipitation during

the pre-1977 and post-1976 periods. The Wilcoxon

rank-sum test revealed no significant differences

between mean precipitation during the fall, winter, and

summer seasons, except for summer precipitation at

the Fountain station. The Wilcoxon rank-sum test

Table 6. Kendall trend analysis of annual precipitation for the period of record, and pre-1977 and post-1976 time periods

[Shaded p-value indicates period with significant trend; see table 1, fig. 1 for station location]

Station identifier Time period Time period

(water years) Kendall tau Two-sidep-value

Trend slope

(inches/year)

Colorado Springs Pre-1977 1950–76 0.07 0.6022 0.0855

Post-1976 1977–99 0.13 0.4298 0.1429

Period of record 1950–99 0.26 0.0086 0.1346

Fountain Pre-1977 1949–76 −0.01 0.9335 −0.0058

Post-1976 1977–97 −0.01 1.0000 −0.0143

Period of record 1949–97 0.30 0.0049 0.1415

Pueblo Pre-1977 1955–76 −0.16 0.3100 −0.1450

Post-1976 1977–99 0.27 0.0804 0.1120

Period of record 1955–99 0.20 0.0613 0.0714

Ruxton Park Pre-1977 1960–76 0.00 1.0000 0.0041

Post-1976 1977–99 0.39 0.0144 0.4012

Period of record 1960–99 0.20 0.0916 0.1468

Table 7. Summary of Kendall trend analysis of spring precipitation

[Shaded p-value indicates period with significant trend; see table 1, fig. 1 for location]

Station identifier Time period Time period

(water year) Kendall tau Two-sidep-value

Trend slope

(inches/year)

Colorado Springs Pre-1977 1950–76 0.07 0.6168 0.0257

Post-1976 1977–99 0.04 0.8215 0.0277

Period of record 1950–99 0.22 0.0279 0.0596

Fountain Pre-1977 1949–76 −0.08 0.5878 −0.0336

Post-1976 1977–97 0.06 0.7619 0.0700

Period of record 1949–97 0.16 0.1175 0.0312

Pueblo Pre-1977 1955–76 −0.14 0.3819 −0.0500

Post-1976 1977–99 0.28 0.0711 0.0693

Period of record 1955–99 0.22 0.0354 0.0376

Ruxton Park Pre-1977 1960–76 0.24 0.2016 0.1478

Post-1976 1977–99 0.27 0.0907 0.1329

Period of record 1960–99 0.32 0.0047 0.1000
STREAMFLOW 15

revealed highly significant differences in summer

precipitation at the Fountain station (p = 0.0048)

between the pre-1977 and post-1976 periods. The

Wilcoxon rank-sum test also revealed significant

differences in spring precipitation between the

pre-1977 and post-1976 periods at the Fountain

(p = 0.0454) and Ruxton Park (p = 0.0459) stations,

and moderately significant differences at the Colorado

Springs (p = 0.0622) and Pueblo stations (p = 0.0747).

Synthesis of Precipitation Analysis

Precipitation data from four stations were used

to characterize and evaluate changes and trends in

precipitation in the Fountain Creek watershed. Trend

analysis revealed significant increases in annual

precipitation at the Colorado Springs and Fountain

stations since the late 1940’s and moderate increases at

Ruxton Park and Pueblo stations since the mid- to late

1950’s. An analysis of the pre-1977 period indicates

that annual precipitation was generally below average

and no trends were detected in annual precipitation.

An analysis of the post-1976 period indicates that

annual precipitation was generally above average and

upward trends were detected at the Ruxton Park and

Pueblo stations. In addition, the post-1976 annual

precipitation at the Colorado Springs, Fountain,

and Pueblo stations were significantly greater than

the pre-1977 annual precipitation. However, there has

been no change in the distribution or magnitude of

rainfall occurring during a 24-hour period. Therefore,

the differences between the two periods result from

more days with rainfall rather than more rain during

any given day. Also, because two of the four stations

evaluated had upward trends for the post-1976 period

and storms that produce most of the precipitation are

isolated convection storms, it is plausible that other

parts of the watershed had increasing precipitation

that could affect trends in streamflow.

An analysis of seasonal trends indicated that

significant increases in spring precipitation have

occurred at the Ruxton Park, Colorado Springs, and

Pueblo stations since the 1940’s and 1950’s. An analysis of the pre-1977 period indicated no significant

trend during any season. An analysis of the post-1976

period indicated moderately significant upward trends

in spring precipitation at the Ruxton Park and Pueblo

stations. The upward trends in annual precipitation for

the post-1976 period at the Ruxton Park and Pueblo

stations are likely a result of the upward trends in

spring precipitation at these stations.

STREAMFLOW

Streamflow in the Fountain Creek watershed

varies seasonally and has three distinct flow regimes:

base flow, spring snowmelt and storm runoff that

occurs during the summer monsoon season (fig. 7).

The base-flow period begins in late September or early

October and extends until the following April. During

the base-flow period, streamflow is fairly uniform.

Depending on temperature and winter snowfall

amounts, the snowmelt period begins about mid-April

and extends until about mid-June. Early in the snowmelt period, streamflow increases substantially from

Table 8. Wilcoxon rank sum test of differences between mean annual precipitation during the pre-1977 and post-1976 time

periods

[Shaded values indicate significant differences in mean precipitation between the pre-1977 and post-1976 time periods; N, number of complete years of

record in period]

Station identifier Time period Time period

(water years) N Mean score p-value

Colorado Springs Pre-1977 1950–76 28 20.7 0.0083

Post-1976 1977–99 22 31.7

Fountain Pre-1977 1949–76 27 16.9 0.0006

Post-1976 1977–97 16 30.6

Pueblo Pre-1977 1955–76 22 18.9 0.0620

Post-1976 1977–99 22 26.1

Ruxton Park Pre-1977 1960–76 16 17.5 0.4713

Post-1976 1977–99 21 20.1
16 Trends in Precipitation and Streamflow and Changes in Stream Morphology in the Fountain Creek Watershed,

Colorado, 1939–99

Oct Nov Dec Jan Feb Mar Apr May June July Aug Sept 0

600

50

550500450400350300250200150100

MEAN-DAILY STREAMFLOW, IN CUBIC FEET PER SECOND

Base flow Snowmelt Summer

Figure 7. Annual hydrograph of average mean-daily streamflow at Pinon, 1973 through 1999.
STREAMFLOW 17

base-flow conditions. Streamflow decreases fairly

quickly after peaking in early to mid-May. The

summer flow period follows the snowmelt period and

generally begins about mid-June and extends through

September, sometimes into October. Streamflow

during the summer period is highly variable. Changes

in streamflow during the summer are primarily driven

by afternoon and evening storms.

Temporal Trends

Temporal trends in streamflow were evaluated

for the following streamflow statistics: annual instantaneous peak streamflow, high daily-mean streamflow

percentiles (70th, 90th, 100th percentile), high dailymean streamflow duration (7-, 14-, 30-day), low dailymean streamflow percentiles (0th, 10th, 30th percentile), and low daily-mean streamflow duration (7-, 14-,

30-day). The instantaneous peak streamflow statistic

was evaluated for the period of record, pre-1976, and

post-1975 time periods; all other statistics were evaluated for the period of record, pre-1977, and post-1976

time periods. The mismatch in the time periods is

due to the fact that two of the selected gaging stations

were not operational until January 1976 (water year).

The result was an incomplete year of record, which

prevented the evaluation of streamflow percentiles

and streamflow duration statistics. Instantaneous peak

streamflow data were available for the partial year

of record. Cumulative streamflow data were compared

to cumulative precipitation data to evaluate the relation

between streamflow and precipitation.

Trends in High Streamflow Statistics

Trends in annual instantaneous peak streamflow; 70th, 90th, and 100th daily-mean streamflow

percentiles; and 7-, 14-, and 30-day daily-mean

streamflow statistics were evaluated. Annual instantaneous peak streamflows were derived from the single

highest recorded stage during a given water year.

Streamflow percentiles, 70th, 90th, and 100th, are

equivalent to the 255th, 328th and annual maximum

daily-mean streamflow values when sorted from

smallest to largest. Flow-duration statistics, 7-, 14-,

and 30-day, were computed by averaging daily-mean

streamflows for n-days.

Instantaneous Peak Streamflow

Variations in annual instantaneous peak streamflow for the six gaging stations are shown in figure 8.

Kendall trend analysis indicated significant upward

trend in annual instantaneous peak streamflow at the

Pikeview station for the post-1975 period and highly

significant upward trend in annual instantaneous peak

streamflow at Security (table 9) for the period of

record (1967–99). However, significant trends in

annual instantaneous peak streamflow were not

detected during the pre-1976 period at any station

and post-1975 time period at any station except

the Pikeview station.

Evaluation of long-term streamflow data at

Pueblo (1941–65, 1971–99) indicates instantaneous

streamflow peaks of 10,000 ft3

/s or greater magnitude

occurred more frequently during the 1990’s than any

decade since the 1940’s (fig. 8). Annual instantaneous

peak streamflow during 1994–97 and 1999 ranked

in the top 16 of 59 (27 percent) all-time recorded

maximum streamflow events. Although large streamflow events occurred more frequently during the

1990’s than during previous decades since the 1940’s,

no significant trend was detected in the magnitude of

peak streamflow events. The magnitudes of streamflow events that occurred during the 1990’s were not

atypical of historical peaks.

Examination of streamflow data and historical

accounts of the period (Colorado Climate Center,

1999; National Oceanographic and Atmospheric

Administration, 1999; Snipes, 1974) indicates that

the four largest streamflow events at Pueblo occurred

during the spring snowmelt period, mid-April to midJune (table 10). Each of these events was caused by

several inches of rainfall that fell during intense storms

over large areas of the Fountain Creek watershed and

southeastern Colorado during a short period of time.

In some areas, rainfall amounts received during a

couple of days approached or exceeded the average

total annual rainfall in the Colorado Springs area

(table 10) (National Oceanographic and Atmospheric

Administration, 1999; Hansen and others, 1978;

Snipes, 1974). Also significant is the fact that the

most recent event, the flood of April 30, 1999, was

estimated to be about a 15-year flood for this station.

A 15-year flood is a streamflow event of a given

magnitude with a probability of recurring once every

15 years. This estimate is based on available record,

not including the 1935 peak streamflow. The peak

streamflow of 1935 is an estimate and considered
18 Trends in Precipitation and Streamflow and Changes in Stream Morphology in the Fountain Creek Watershed,

Colorado, 1939–99

0

1940 1950 1960 1970

6,0004,0002,000

Pikeview

1950 1960 1970 0

12,000

8,0006,0004,0002,000

10,000

STREAMFLOW, IN CUBIC FEET PER SECOND Nevada Street

1940 1950 1960 1970 1980 1990

WATER YEAR (OCTOBER - SEPTEMBER)

0

20,000

5,000

15,00010,000

Pinon

2000 1980 19902000

0

1940

5,000

1940 1950 1960

WATER YEAR (OCTOBER - SEPTEMBER)

0

30,00020,00010,000

Pueblo

2000 1950 1960 1970 1980 1990

20,00015,00010,000

Security

2000 1970 1980 1990

maximum streamflow during 1965 47,000 cubic feet per second

2000 1950 1960 1970 1980 1990 2000 1940 0

3,0002,0001,000

Near CO Spgs

1980 1990

1940

Figure 8. Annual instantaneous peak streamflow at gaging stations in the Fountain Creek watershed, 1940

–99.
STREAMFLOW 19

questionable. The flood of April 30, 1999, caused

millions of dollars of damage and resulted in Presidential declaration of several counties in the Fountain

Creek watershed as well as other downstream counties

as a Federal flood disaster area.

High Streamflow Percentiles

The 70th percentile (Q70), 90th percentile (Q90),

and 100th percentile (Q100) daily-mean streamflows

were computed for each year. The n-percentile indicates that n percent of the annual daily-mean streamflow is below a given streamflow, or (100 minus n)

percent is above it. Results of analysis of trends in

streamflow percentiles are summarized in table 11.

Two stations, Near CO Spgs and Security, had

continuous streamflow record dating back to the late

1950’s and mid 1960’s. Two other stations, Pikeview

and Pueblo, had historical streamflow record dating

back to the early 1920’s and early 1940’s; however,

this record was not continuous. Significant upward

trends (p<0.05) were evident in the Q70, Q90, and Q100

percentiles at the Security station and the Q70 and Q90

percentiles at the Near CO Spgs station for the respective periods of record. At the Near CO Spgs station,

estimated annual changes in the Q70 and Q90 streamflow regimes were small, with trend slopes of 0.22 and

0.49 ft3/s per year. At the Security station, estimated

annual changes in the Q70, Q90, and Q100 streamflow

Table 9. Kendall trend analysis of annual instantaneous peak streamflow for the indicated period of record, and pre-1976 and

post-1975 time periods

[Shaded p-value indicates period with a significant trend; ft3/s/yr, cubic feet per second per year; see table 1, figure 1 for location]

Station identifier Time period Time period

(water years) Kendall tau Two-sidep-value

Trend slope

(ft3/s/yr)

Pikeview pre-1976 1939–49 0.20 0.4363 20.0

post-1975 1976–99 0.29 0.0471 40.0

Near CO Spgs period of record 1958–99 −0.01 0.9051 −0.65

pre-1976 1958–75 −0.27 0.1297 −14.5

post-1975 1976–99 0.13 0.3989 18.6

Nevada Street post-1975 1976–99 0.22 0.1303 97.8

Security period of record 1967–99 0.41 0.0009 130

pre-1976 1967–75 −0.06 0.9170 −20.0

post-1975 1976–99 0.12 0.4419 60.0

Pinon post-1975 1976–99 0.13 0.3850 50.5

Pueblo pre-1976 1941–65 −0.07 0.6238 −114

post-1975 1976–99 0.14 0.3334 111

Table 10. Summary of five largest streamflow events on Fountain Creek at Pueblo, Colorado, and magnitude and general

location of precipitation

[ft3/s, cubic feet per second; na, not available; NE, northeast; yr, year]

Date

Peak

instantaneous

streamflow

(in ft3/s)

Recurrence

interval

exceeded

Streamflow at

recurrence interval

(in ft3/s)

Flow period

General storm

location within

watershed

Reported

precipitation

(in inches)

06/17/1965 47,000 200 yr 45,750 Snowmelt NE Colorado Springs 14

05/30/1935 35,000 50 yr 30,060 Snowmelt NE Colorado Springs 18

06/04/1921 34,000 50 yr 30,060 Snowmelt na na

04/30/1999 18,900 10 yr 15,750 Snowmelt Colorado Springs 10

07/10/1945 17,800 10 yr 15,750 Summer na na
20 Trends in Precipitation and Streamflow and Changes in Stream Morphology in the Fountain Creek Watershed,

Colorado, 1939–99

regimes were larger than the Near CO Spgs station,

with trend slopes of about 3.5, 5.2, and 26.7 ft3/s per

year. Analysis of trends for the period of record at

Pikeview and Pueblo was not conducted due to the

hiatus of continuous record prior to 1976.

Streamflow records were divided into pre-1977

and post-1976 time periods. Streamflow record from

four stations—Pikeview, Near CO Spgs, Security, and

Pueblo, as noted above—were used to evaluate trends

in the pre-1977 period. Significant trends were not

Table 11. Kendall trend analysis of 70th, 90th, and 100th percentiles of streamflow for the respective periods of record,

pre-1977, and post-1976 time periods

[Shaded p-values indicate periods with a significant trend; ft3/s/yr, cubic feet per second per year]

Station identifier Time period Time period

(water years) Kendall tau Two-sidep-value

Trend slope

(ft3/s/yr)

Annual 70th percentile of daily streamflow (Q70)

Pikeview pre-1977 1939–49 −0.04 0.9372 0.00

post-1976 1977–99 0.39 0.0096 1.21

Near CO Spgs period of record 1959–99 0.30 0.0052 0.22

pre-1977 1959–76 −0.07 0.7316 −0.02

post-1976 1977–99 0.34 0.0262 0.55

Nevada Street post-1976 1977–99 0.36 0.0187 2.40

Security period of record 1965–99 0.60 0.0000 3.53

pre-1977 1965–76 0.02 1.0000 0.17

post-1976 1977–99 0.48 0.0014 5.00

Pinon post-1976 1977–99 0.51 0.0008 6.78

Pueblo pre-1977 1941–65 −0.16 0.2721 −0.94

post-1976 1977–99 0.49 0.0011 6.57

Annual 90th percentile of daily streamflow (Q90)

Pikeview pre-1977 1939–49 −0.02 1.0000 −0.20

post-1976 1977–99 0.29 0.0571 1.55

Near CO Spgs period of record 1959–99 0.27 0.0125 0.49

pre-1977 1959–76 0.00 1.0000 0.00

post-1976 1977–99 0.26 0.0905 1.30

Nevada Street post-1976 1977–99 0.24 0.1191 5.00

Security period of record 1965–99 0.43 0.0003 5.25

pre-1977 1965–76 −0.29 0.2160 −2.67

post-1976 1977–99 0.31 0.0419 7.62

Pinon post-1976 1977–99 0.29 0.0571 7.75

Pueblo pre-1977 1941–65 −0.20 0.1803 −4.77

post-1976 1977–99 0.29 0.0538 8.13

Annual 100th percentile of daily streamflow (Q100)

Pikeview pre-1977 1939–49 0.13 0.6404 4.33

post-1976 1977–99 0.42 0.0055 13.07

Near CO Spgs period of record 1959–99 0.13 0.2293 1.00

pre-1977 1959–76 0.01 1.0000 0.14

post-1976 1977–99 0.16 0.2908 3.35

Nevada Street post-1976 1977–99 0.28 0.0645 22.75

Security period of record 1965–99 0.36 0.0025 26.70

pre-1977 1965–76 0.12 0.6312 28.00

post-1976 1977–99 0.32 0.0324 25.18

Pinon post-1976 1977–99 0.33 0.0302 50.88

Pueblo pre-1977 1941–65 −0.07 0.6238 −11.47

post-1976 1977–99 0.41 0.0071 54.00
STREAMFLOW 21

detected in the Q70, Q90, and Q100 streamflow regimes

at the Pikeview, Near CO Spgs, Security, and Pueblo

stations during the pre-1977 time period.

For the post-1976 time period, streamflow

records from all six stations were evaluated. Analyses

indicated significant upward trends in the Q70 streamflow regime at all stations. Trend-slope estimates

indicated that changes in the Q70 streamflow regime

generally increased from upstream to downstream and

ranged from 0.6 ft3/s per year at the Near CO Spgs

station to about 6.8 ft3/s per year at the Pinon station

and 6.6 ft3/s per year at the Pueblo station. Moderately

significant to significant trends were detected in the

post-1976 Q90 streamflow regime at the Pikeview,

Near CO Spgs, Security, Pinon, and Pueblo stations. A

significant trend was not detected in the Q90 streamflow regime at Nevada Street during the post-1976

period. Trend-slope estimates indicate that changes in

the Q90 streamflow regime increased from upstream to

downstream stations and ranged from 1.3 ft3

/s/yr at

Near CO Spgs to 8.1 ft3

/s/yr at Pueblo. Moderate to

highly significant trends were detected in the Q100

steamflow regimes at the Pikeview, Nevada Street,

Security, Pinon, and Pueblo stations. Trend-slope estimates indicated that changes in the Q100 streamflow

regime generally increased from upstream to downstream and ranged from about 13.1 ft3

/s per year at the

Pikeview station to 54.0 ft3/s per year at the Pueblo

station. A significant trend in the Q100 streamflow

regime was not detected in the post-1976 streamflow

record for the Near CO Spgs station.

The significant upward trend in precipitation

at the Ruxton Park station during the post-1976 period

(fig. 6) could possibly explain the upward trends in

Q70 and Q90 streamflow at the Near CO Spgs station.

In the absence of significant changes over time in

post-1976 precipitation at the Colorado Springs and

Fountain stations (fig. 6), upward trends in the high

streamflow regimes at the Nevada Street, Security,

and Pinon stations that were detected in the post-1976

period could be explained by changes in land use and

(or) water use and resultant rate of runoff in the watershed. However, it is plausible that precipitation has

increased over time in other parts of the watershed

but went undetected because of the sparse spatial

distribution of fairly long-term precipitation stations

and the scattered spatial distribution of convection

storms. Additionally, changes in high-flow regimes

at upstream locations generally would be transferred

to downstream locations.

Streamflow Duration

The 7-, 14-, and 30-day high daily-mean streamflow statistics were evaluated. The n-day high streamflow duration indicates the highest average daily-mean

streamflow for n-consecutive days during a year. Time

series of annual 7-, 14-, and 30-day high-flow magnitude are shown in figure 9.

Analysis of 7-, 14-, and 30-day high daily-mean

streamflow magnitudes at the Pikeview station did not

indicate trends during the 1939 through 1949 period

(table 12). However, moderately significant to significant upward trends were detected in the 7- and 14-day

daily-mean streamflow magnitudes during the 1977

through 1999 period. Although analysis indicated

upward trends in 7- and 14-day high daily-mean

streamflow since 1977, it is important to note that the

magnitudes of the high daily-mean streamflow durations since 1977 generally have been similar to, or

slightly less than, daily-mean streamflows of the same

durations during the 1939 through 1949 time period

(fig. 9).

At the Near CO Spgs station, analysis indicated

moderately significant upward trend in the high 7-day

daily-mean streamflow and significant upward trends

in the 14- and 30-day daily-mean streamflow statistics

for the period of record (1959–99). Significant trends

were not indicated in the 7- and 14-day high dailymean streamflow during the pre-1977 and post-1976

time periods; however, moderately significant upward

trends were indicated in the 30-day high daily-mean

streamflow statistic for the post-1976 period. Figure 9

illustrates that the 7-, 14-, and 30-day daily-mean

streamflow in the mid- to late 1990’s have been greater

than those of most of the historical record. Therefore,

the indicated upward significant trend in 14- and

30-day high daily-mean streamflow for the period

of record was affected by the high streamflows that

occurred in the mid- to late 1990’s.

At the Security station, highly significant

upward trends were indicated in the 7-, 14-, and

30-day high daily-mean streamflows for the period

of record, and moderately significant to significant

upward trends were indicated in the 7-, 14-, and

30-day high daily-mean streamflow for the post-1976

period. Similar to the Near CO Spgs station, no significant trends were indicated for the pre-1977 period at

the Security station. Again, the upward significant

trends in 7-, 14- and 30-day high daily-mean streamflows for the period of record were affected by the

high streamflows that occurred in the mid- to late

1990’s.
22 Trends in Precipitation and Streamflow and Changes in Stream Morphology in the Fountain Creek Watershed,

Colorado, 1939–99

1940 2000 1950 1960 1970 1980 1990 0

1,200

800600400200

1,000

1940 2000 1950 1960 1970 1980 1990 0

500400300200100

1940 2000 1950 1960 1970 1980 1990 0

3,5003,0002,0001,000

STREAMFLOW, IN CUBIC FEET PER SECOND 1940 2000 1950 1960 1970 1980 1990 0 5,000 4,000 3,000 2,000 1,000

1940 2000 1950 1960 1970 1980 1990

WATER YEAR

0

5,0004,0003,0002,0001,000

7-day high flow14-day high flow30-day high flow

1940 2000 1950 1960 1970 1980 1990

WATER YEAR

0

5,0004,0003,0002,0001,000

Pikeview Near CO Spgs

Nevada Street Security

Pinon Pueblo

Figure 9. Magnitude of 7-, 14-, and 30-day high flows at gaging stations in the Fountain Creek watershed, 1940

–99.
STREAMFLOW 23

High daily-mean streamflow duration analysis

at the Pinon station indicated moderately significant

upward trend in the magnitude of the 7-day high dailymean streamflow for the post-1976 period. Significant

trends were not detected in the magnitude of 14- or

30-day streamflow statistics.

At the Pueblo station, analysis indicated no

significant trends in the magnitude of the 7-, 14-, or

30-day streamflow statistics for the pre-1977 period.

Significant to moderately significant upward trend was

indicated in the 7-, 14-, and 30-day streamflow statistics for the post-1976 period. As occurred with many

Table 12. Kendall trend analysis of 7-, 14-, and 30-day high daily-mean streamflow duration

[Shaded p-values indicate periods with a significant trend; ft3/s/yr, cubic feet per second per year; see table 1, figure 1 for location]

Station identifier Time period Time period

(water years) Kendall tau Two-sidep-value

Trend slope

(ft3/s/yr)

7-day

Pikeview pre-1977 1939–49 0.05 0.8763 1.0

post-1976 1977–99 0.30 0.0447 5.4

Near CO Spgs period of record 1959–99 0.21 0.0506 0.8

pre-1977 1959–76 0.12 0.4954 0.7

post-1976 1977–99 0.24 0.1191 2.0

Nevada Street post-1976 1977–99 0.22 0.1538 8.6

Security period of record 1965–99 0.35 0.0029 11.4

pre-1977 1965–76 0.18 0.4507 13.4

post-1976 1977–99 0.33 0.0303 15.5

Pinon post-1976 1977–99 0.27 0.0725 15.5

Pueblo pre-1977 1941–65 −0.16 0.2825 −6.1

post-1976 1977–99 0.30 0.0447 24.7

14-day

Pikeview pre-1977 1939–49 0.09 0.7555 3.4

post-1976 1977–99 0.28 0.0645 3.3

Near CO Spgs period of record 1959–99 0.22 0.0398 0.8

pre-1977 1959–76 0.18 0.3247 0.6

post-1976 1977–99 0.21 0.1696 2.1

Nevada Street post-1976 1977–99 0.18 0.2452 5.5

Security period of record 1965–99 0.37 0.0017 8.5

pre-1977 1965–76 0.18 0.4507 8.8

post-1976 1977–99 0.30 0.0447 11.8

Pinon post-1976 1977–99 0.24 0.1131 12.5

Pueblo pre-1977 1941–65 −0.17 0.2336 −8.3

post-1976 1977–99 0.27 0.0725 18.0

30-day

Pikeview pre-1977 1939–49 0.02 1.0000 0.6

post-1976 1977–99 0.23 0.1256 2.1

Near CO Spgs period of record 1959–99 0.26 0.0157 0.6

pre-1977 1959–76 0.12 0.4954 0.3

post-1976 1977–99 0.25 0.0960 1.7

Nevada Street post-1976 1977–99 0.18 0.2345 6.0

Security period of record 1965–99 0.39 0.0010 6.8

pre-1977 1965–76 0.12 0.6312 3.4

post-1976 1977–99 0.27 0.0725 10.2

Pinon post-1976 1977–99 0.21 0.1696 10.1

Pueblo pre-1977 1941–65 −0.21 0.1412 −6.11

post-1976 1977–99 0.28 0.0683 15.1
24 Trends in Precipitation and Streamflow and Changes in Stream Morphology in the Fountain Creek Watershed,

Colorado, 1939–99

of the upstream stations, the streamflow durations in

the mid- to late 1990’s have generally been greater

than most of the historical record.

The relative ranks of streamflow magnitude of

the high daily-mean streamflow duration statistics

were compared. The evaluation of the rank of the high

daily-mean streamflow indicates that the magnitude of

streamflow within all the high daily-mean streamflow

duration statistics for 1999 were either ranked first or

second for the entire period of record at all the stations

evaluated. This indicates that high streamflows that

occurred during 1999 remained elevated for a longer

period of time than any other period of record.

Trends in Low Streamflow Statistics

Trends in 0th, 10th, and 30th daily-mean

streamflow percentiles and 7-, 14-, and 30-day low

daily-mean streamflow statistics were evaluated.

Streamflow percentiles, 0th, 10th, and 30th, are equivalent to the annual minimum, 36th, and 109th annual

daily-mean streamflow values when sorted from

smallest to largest. Low streamflow duration statistics,

7-, 14-, and 30-day, were computed by averaging

daily-mean streamflows for n-days.

Low Streamflow Percentiles

Specific streamflow statistics were computed

for each year: minimum (Q0), 10th percentile (Q10),

and 30th percentile (Q30) daily-mean streamflow.

The n-percentile indicates that n percent of the annual

daily-mean streamflow is below a given streamflow,

or (100 minus n) percent is above it. Results of analysis of trend in streamflow percentiles are summarized

in table 13.

Significant upward trends were detected in the

Q0, Q10, and Q30 streamflow regime at the Near CO

Spgs station (1959–99). Highly significant upward

trends were detected in the Q0, Q10, and Q30 streamflow regimes at the Security station (1965–99). At the

Near CO Spgs station, estimated annual changes in the

Q0, Q10, and Q30 streamflow regime were small, 0.05,

0.06, and 0.07 ft3

/s per year, respectively. Downstream

at the Security station, estimated changes in the Q0,

Q10, and Q30 were larger, about 1.7, 2.5, and 2.8 ft3

/s

per year, respectively.

Similar to the analysis of trends in the magnitude of high daily-mean streamflow statistics, analysis

did not indicate trends in the Q0, Q10, and Q30 streamflow regimes during the pre-1977 time period at the

Pikeview, Near CO Spgs, Security, or Pueblo stations.

For the post-1976 time period, analysis

indicated highly significant upward trends in the

Q0, Q10, and Q30 streamflow regimes at the Pikeview,

Nevada Street, Security, Pinon, and Pueblo stations

and a moderately significant upward trend in the Q30

streamflow regime at the Near CO Spgs station. No

significant trends were detected for this period in the

Q0 and Q10 flow statistics for the Near CO Spgs

station. Trend slope estimates indicate that changes

in the Q0 streamflow regime increased from Pikeview

and Nevada, with trend slopes of about 0.5 and

0.7 ft3

/s per year, to Security, with a trend slope of

2.2 ft3/s per year. The trend slope then decreased at

Pinon and Pueblo to about 0.8 ft3

/s per year. Similar

changes were indicated by the analysis of the Q10

streamflow regime. Trend slope estimates indicate

that changes in the Q10 streamflow regime increased

from Nevada Street (0.9 ft3

/s per year) to Security

(about 3.4 ft3/s per year) and then decreased at

Pinon (about 2.7 ft3/s per year). Trend slope estimates

indicate that changes in the Q30 streamflow regime

increased from Pikeview (about 0.7 ft3/s per year) and

Near CO Spgs (about 0.2 ft3/s per year) to Nevada

Street (about 1.1 ft3/s per yr), Security (about 3.9 ft3

/s

per year), and Pinon (6.1 ft3/s per year) and then

decreased at Pueblo (about 5.3 ft3

/s per year).

The upward trends in all three of the low streamflow statistics for the 1977–99 period indicate that

low streamflow conditions have significantly increased

throughout most of the watershed over the past

23 years.

In the Fountain Creek watershed, streamflow

consists of native and imported transbasin water.

Transbasin water is used to meet the growing

domestic, municipal, and industrial water uses in the

Colorado Springs metropolitan area. Return flows

associated with lawn watering throughout Colorado

Springs and the municipalities along Monument Creek

may explain the indicated trends in the low streamflow

regimes from the Pikeview to Nevada Street stations.

Return flows may explain a portion of the indicated

trends in low streamflow downstream from the Nevada

Street station. Upstream return flows combined with

increases in wastewater effluent and changes in water

management downstream from the Nevada Street

station result in the indicated increases in the low-flow

regimes (Q0 – Q30) downstream from the Nevada

Street station.
STREAMFLOW 25

Streamflow Duration

The magnitudes of low streamflow with 7-,

14-, and 30-day durations were evaluated. Low n-day

streamflow duration indicates the lowest average

daily-mean streamflow for n-consecutive days during

a year. Unlike graphical analysis of high daily-mean

streamflows (fig. 9 and table 12), trends in the magnitude of 7-, 14-, and 30-day low streamflows were quite

obvious for most stations (fig. 10) and are summarized

in table 14.

Table 13. Kendall trend analysis for 0th, 10th, and 30th percentiles of streamflow for the respective periods of record,

pre-1977 and post-1976 time periods

[Shaded p-values indicate stations and time periods with a significant trend; ft3/s/yr, cubic feet per second per year; see table 1, figure 1 for location]

Station identifier Time period Time period

(water years) Kendall tau Two-sidep-value

Trend slope

(ft3/s/yr)

Annual minimum (daily mean) streamflow (Q0)

Pikeview pre-1977 1939–49 0.33 0.1844 0.17

post-1976 1977–99 0.51 0.0006 0.47

Near CO Spgs period of record 1959–99 0.28 0.0110 0.05

pre-1977 1959–76 −0.01 0.9697 0.00

post-1976 1977–99 0.13 0.4125 0.03

Nevada Street post-1976 1977–99 0.42 0.0051 0.67

Security period of record 1965–99 0.66 0.0000 1.69

pre-1977 1965–76 0.35 0.1305 0.70

post-1976 1977–99 0.50 0.0010 2.20

Pinon post-1976 1977–99 0.71 0.0000 0.73

Pueblo pre-1977 1941–65 0.19 0.1889 0.01

post-1976 1977–99 0.62 0.0000 0.88

Annual 10th percentile of daily streamflow (Q10)

Pikeview pre-1977 1939–49 0.31 0.2101 0.22

post-1976 1977–99 0.58 0.0001 0.57

Near CO Spgs period of record 1959–99 0.24 0.0308 0.06

pre-1977 1959–76 −0.21 0.2377 −0.03

post-1976 1977–99 0.14 0.3548 0.08

Nevada Street post-1976 1977–99 0.43 0.0041 0.89

Security period of record 1965–99 0.66 0.0000 2.53

pre-1977 1965–76 0.30 0.1905 0.54

post-1976 1977–99 0.54 0.0004 3.36

Pinon post-1976 1977–99 0.64 0.0000 2.70

Pueblo pre-1977 1941–65 0.02 0.9248 0.00

post-1976 1977–99 0.61 0.0001 3.00

Annual 30th percentile of daily streamflow (Q30)

Pikeview pre-1977 1939–49 0.24 0.3502 0.29

post-1976 1977–99 0.48 0.0014 0.70

Near CO Spgs period of record 1959–99 0.29 0.0085 0.07

pre-1977 1959–76 −0.20 0.2535 −0.06

post-1976 1977–99 0.25 0.0952 0.17

Nevada Street post-1976 1977–99 0.44 0.0036 1.05

Security period of record 1965–99 0.72 0.0000 2.84

pre-1977 1965–76 0.30 0.1905 0.67

post-1976 1977–99 0.60 0.0001 3.85

Pinon post-1976 1977–99 0.58 0.0001 6.06

Pueblo pre-1977 1941–65 −0.15 0.2922 −0.08

post-1976 1977–99 0.51 0.0007 5.33
26 Trends in Precipitation and Streamflow and Changes in Stream Morphology in the Fountain Creek Watershed,

Colorado, 1939–99

1940 2000 1950 1960 1970 1980 1990 0

25

5

201510

1940 2000 1950 1960 1970 1980 1990 2

14

864

1210

1940 2000 1950 1960 1970 1980 1990 0

604020

STREAMFLOW, IN CUBIC FEET PER SECOND 1940 2000 1950 1960 1970 1980 1990 0 15050 100

1940 2000 1950 1960 1970 1980 1990

WATER YEAR

0

120

80604020

100

7-day low flow14-day low flow30-day low flow

1940 2000 1950 1960 1970 1980 1990

WATER YEAR

0

150

50

100

Pikeview Near CO Spgs

Nevada Street Security

Pinon Pueblo

Figure 10. Magnitude of 7-, 14-, and 30-day low flows at gaging stations in the Fountain Creek watershed, 1940

–99.
STREAMFLOW 27

Analysis of 7-, 14-, and 30-day low streamflows

at Pikeview did not indicate trends during the 1939

through 1949 time period. Highly significant trends

were detected in the 1977 through 1999 time period.

Estimated trend slopes in the 7-, 14-, and 30-day low

streamflow for the 1977 to 1999 time period were

about 0.5 and 0.6 ft3

/s/yr. Increases in low streamflow

appear to have begun in the early 1980’s, peaked in

the mid-1980’s, and have remained relatively constant

since 1985 (fig. 10).

Analysis of 7-, 14-, and 30-day low streamflow

at the Near CO Spgs station indicated significant

trends for the period of record, 1959–99. However,

although the analysis indicated that the trends were

Table 14. Kendall trend analysis of 7-, 14-, and 30-day low streamflow duration

[Shaded p-values indicated stations and time periods with significant trend; ft3/s/yr, cubic feet per second per year; see table 1, figure 1 for location]

Station identifier Time period Time period

(water years) Kendall tau Two-sidep-value

Trend slope

(ft3/s/yr)

7-day

Pikeview pre-1977 1939–49 0.27 0.2758 0.21

post-1976 1977–99 0.49 0.0011 0.48

Near CO Spgs period of record 1959–99 0.24 0.0277 0.06

pre-1977 1959–76 −0.29 0.0956 −0.09

post-1976 1977–99 0.16 0.2908 0.07

Nevada Street post-1976 1977–99 0.46 0.0022 0.86

Security period of record 1965–99 0.62 0.0000 2.14

pre-1977 1965–76 0.27 0.2437 0.73

post-1976 1977–99 0.47 0.0018 2.84

Pinon post-1976 1977–99 0.73 0.0000 1.66

Pueblo pre-1977 1941–65 0.11 0.4545 0.01

post-1976 1977–99 0.67 0.0000 1.74

14-day

Pikeview pre-1977 1939–49 0.35 0.1611 0.23

post-1976 1977–99 0.55 0.0003 0.54

Near CO Spgs period of record 1959–99 0.24 0.0310 0.06

pre-1977 1959–76 −0.33 0.0582 −0.10

post-1976 1977–99 0.17 0.2787 0.08

Nevada Street post-1976 1977–99 0.40 0.0082 0.84

Security period of record 1965–99 0.65 0.0000 2.37

pre-1977 1965–76 0.33 0.1499 0.76

post-1976 1977–99 0.52 0.0005 3.25

Pinon post-1976 1977–99 0.71 0.0000 2.28

Pueblo pre-1977 1941–65 0.08 0.5748 0.01

post-1976 1977–99 0.62 0.0000 2.30

30-day

Pikeview pre-1977 1939–49 0.31 0.2129 0.25

post-1976 1977–99 0.57 0.0002 0.59

Near CO Spgs period of record 1959–99 0.25 0.0240 0.06

pre-1977 1959–76 −0.27 0.1202 −0.05

post-1976 1977–99 0.15 0.3283 0.07

Nevada Street post-1976 1977–99 0.39 0.0096 0.84

Security period of record 1965–99 0.67 0.0000 2.49

pre-1977 1965–76 0.21 0.3727 0.57

post-1976 1977–99 0.57 0.0002 3.59

Pinon post-1976 1977–99 0.66 0.0000 2.95

Pueblo pre-1977 1941–65 −0.22 0.1288 −0.02

post-1976 1977–99 0.60 0.0001 2.81
28 Trends in Precipitation and Streamflow and Changes in Stream Morphology in the Fountain Creek Watershed,

Colorado, 1939–99

significant, the trend slope estimates were generally

small (0.06 ft3

/s/yr). Moderately significant downward

trends were indicated in the 7- and 14-day low streamflows for the pre-1977 period, and trends were not

indicated in the 30-day low streamflow for the pre1977 period or in the 7-, 14-, or 30-day low streamflows for the post-1976 time periods. Figure 10 indicates that long-term trends (1959–99) were affected

by relatively recent changes in low streamflow.

Analysis of 7-, 14-, and 30-day low streamflow

at the Nevada Street station indicated highly significant upward trends. Trend slope estimates for 7-, 14-,

and 30-day low streamflow were about 0.8 ft3/s per

year. The pattern in low streamflow duration at the

Nevada Street station is similar to patterns at the

Pikeview station for the same time period (1977–99).

The similarities indicate that the changes in low

streamflow that occurred at the Nevada Street station

probably are largely the result of changes in land use

and(or) water management in the Monument Creek

watershed.

Streamflow data were available for the Security

station since 1965. Analysis indicated highly significant upward trends in the 7-, 14-, and 30-day low

streamflow duration statistics for the period of record

and post-1976 period. Analysis did not indicate a

significant trend in the low streamflow duration statistics for the pre-1977 period. Estimates of trend slope

indicate about a three- to sevenfold increase in the

average annual rate of change between the pre-1977

and post-1976 periods. Figure 10 indicates that

increases in low streamflow began in the early 1980’s.

Contrary to trends in high daily-mean streamflow, observed trends in low streamflow duration in the

upstream stations are observable at the downstream

locations at Pinon and Pueblo. At Pinon, analysis indicated highly significant upward trends in 7-day (about

1.7 ft3

/s per year), 14-day (about 2.3 ft3/s per year),

and 30-day (about 3.0 ft3/s per year) low streamflow

during the post-1976 time period. At Pueblo, analysis

did not indicate significant trends in low daily-mean

streamflow during the 1941 through 1965 time period.

Analysis did reveal highly significant trends in 7-, 14-,

and 30-day low streamflow during the post-1976 time

period, with estimates of trend slopes of about 1.7, 2.3,

and 2.8 ft3

/s per year. As with upstream stations,

increases in low daily-mean streamflow duration

began in the early 1980’s and are probably associated

with increases in wastewater-treatment plant

discharges and management of Colorado Springs’

transbasin return-flow exchange decree.

An evaluation of the ranks of the low streamflow duration statistics indicates that the magnitude of

low streamflows in 1999 were the largest or near the

largest at most of the stations in the watershed for the

period of record.

Spatial Trends

Trends in streamflow regimes between upstream

and downstream stations were evaluated for the period

1977 through 1999, the period of overlapping continuous record at all stations. Differences in daily-mean

streamflow for each river reach were normalized by

drainage area:

(1)

where

Qn = normalized change in daily-mean streamflow for stream reach, in cubic feet per

second per square mile;

Qd = daily-mean streamflow at downstream

station, in cubic feet per second;

Qu = daily-mean streamflow at upstream station,

in cubic feet per second;

Ad = drainage area at downstream station, in

square miles; and

Au = drainage area at upstream station, in square

miles.

A decrease in streamflow between an upstream and

downstream station indicated a decrease in streamflow

within the intervening drainage area, and conversely

an increase in streamflow between an upstream and

downstream station indicated an increase in the

amount of streamflow within the intervening drainage

area. The change in daily-mean streamflow for a

stream reach was normalized by dividing the change

in streamflow by the intervening drainage area, which

allows for direct comparison between stream reaches.

High Streamflow

Changes in Q70 high daily-mean streamflow

statistics for five river reaches for 23 years are

shown in figure 11. Trend analyses indicated moderately significant to highly significant increases in Q70

streamflow regime in four river reaches: Pikeview

to Nevada Street, Near CO Spgs to Nevada Street,

Qn

Qd Qu ( ) –

Ad Au ( ) – = ------------------------
STREAMFLOW 29

EXPLANATION

70th percentile90th percentileMaximum streamflow (100th percentile)

Pikeview to Nevada Street

Nevada Street to Security

Pinon to Pueblo

WATER YEAR

1975

100

0.050.020.01

0.50.20.1

521

502010

1975

0.001

100

0.0050.002

0.050.020.01

0.50.20.1

521

502010

Near CO Spgs to Nevada Street

Security to Pinon

2000 1980 1985 1990 1995

2000 1980 1985 1990 1995

1975

100

0.050.020.01

0.50.20.1

521

502010

1975

100

0.50.20.1

521

502010

CHANGE IN STREAMFLOW PER SQUARE MILE

1975 2000 1980 1985 1990 1995

WATER YEAR

100

0.050.020.01

502010

0.50.20.1

2000 1980 1985 1990 1995

2000 1980 1985 1990 1995

521

Figure 11. Normalized high flow for selected reaches of Fountain and Monument Creeks, 1977 through 1999.
30 Trends in Precipitation and Streamflow and Changes in Stream Morphology in the Fountain Creek Watershed,

Colorado, 1939–99

Nevada Street to Security, and Security to Pinon

(table 15). The reach between Nevada Street and

Security indicated the greatest and most significant

increase in streamflow, with a trend slope of about

0.03 [(ft3

/s)/mi2/yr] and a significance of 0.0000.

Analysis indicated a highly significant trend in the Q90

streamflow regime only in the reach between Nevada

Street and Security, with an estimated trend slope

of about 0.04 [(ft3

/s)/mi2/yr] and a significance of

0.0001. Analysis indicated there were no significant

trends at the Q100 streamflow regime within any of the

five river reaches.

The changes in Q70 high streamflow regime

along the reaches between Pikeview and Nevada

Street, Near CO Spgs and Nevada Street, Nevada

Street and Security, and Security and Pinon may be

partially explained by changes in land use, water use,

or both.

Changes in the Q70 and Q90 streamflow regimes

within the reach between the Nevada Street and

Security stations are probably due to changes in land

use within the intervening drainage area. Within the

intervening drainage, recent development has resulted

in changes in land use from rangeland to urban. Within

this drainage, increases in impervious area may have

altered the hydrologic response by increasing storm

runoff by about 0.03 [(ft3

/s)/mi2/yr] or about 3.1 ft3/s

per year, which is about 5 times larger than the estimated trend slopes for the other river reaches.

The small but significant changes in the Q70

streamflow regime along the reach between Security

and Pinon, about 0.004 [(ft3/s)/mi2/yr], probably is

largely a result of changes in land use within the upper

part of the reach.

Low Streamflow

Changes in selected low-streamflow

statistics for five river reaches for 23 years are

shown in figure 12. Trend analysis indicated that

during the period from 1977 through 1999, highly

significant to moderately significant upward trends in

normalized streamflow in the Q0 streamflow regime

(table 16) were detected in three reaches: Near CO

Spgs to Nevada Street, Nevada Street to Security,

and Pinon to Pueblo. The trend slopes indicated estimated increases of about 0.003 [(ft3/s)/mi2/yr] within

the reach from Near CO Spgs to Nevada Street, about

0.03 [(ft3/s)/mi2/yr] within the reach between Nevada

Street and Security, and about 0.11 [(ft3/s)/mi2

/yr]

within the reach from Pinon to Pueblo.

Table 15. Kendall trend analysis for 70th, 90th, and 100th percentiles of normalized streamflow for the post-1976 time period

[Shaded p-values indicate reaches and time periods with a trend; ft3/s, cubic feet per second; mi2, square mile; yr, year; see figure 1 for location]

Stream reach Time period

(water years) Kendall tau Two-sidep-value

Trend slope

[(ft3/s)/mi2/yr]

Annual 70th percentile of daily-mean streamflow (Q70)

Pikeview to Nevada Street 1977–99 0.29 0.0534 0.0058

Near CO Spgs to Nevada Street 1977–99 0.41 0.0065 0.0078

Nevada Street to Security 1977–99 0.69 0.0000 0.0282

Security to Pinon 1977–99 0.36 0.0185 0.0036

Pinon to Pueblo 1977–99 −0.10 0.5074 −0.0022

Annual 90th percentile of daily-mean streamflow (Q90)

Pikeview to Nevada Street 1977–99 0.20 0.1955 0.0126

Near CO Spgs to Nevada Street 1977–99 0.22 0.1538 0.0117

Nevada Street to Security 1977–99 0.57 0.0001 0.0370

Security to Pinon 1977–99 0.22 0.1462 0.0035

Pinon to Pueblo 1977–99 −0.01 0.9789 0.0000

Annual 100th percentile of daily-mean streamflow (Q100)

Pikeview to Nevada Street 1977–99 0.17 0.2787 0.0563

Near CO Spgs to Nevada Street 1977–99 0.23 0.1256 0.0516

Nevada Street to Security 1977–99 0.15 0.3417 0.0534

Security to Pinon 1977–99 0.22 0.1538 0.0611

Pinon to Pueblo 1977–99 0.08 0.5974 0.0633
STREAMFLOW 31

Nevada Street to Security

EXPLANATION

Minimum streamflow (0th percentile)10th percentile30th percentile

2000 1980 1985 1990 1995

Pikeview to Nevada Street

1975 1980 1985 1990

-0.1

0.2

0

0.1

Near CO Spgs to Nevada Street

1975 2000 1980 1985 1990 1995 1975 1980 1985 1990

WATER YEAR

-8

2

-2-4-6

0

Security to Pinon

Pinon to Pueblo

2000 1995

2000 1995

1975 2000 1980 1985 1990 1995

WATER YEAR

1975

-0.4

0.2

-0.2

0

-1-2-3

CHANGE IN STREAMFLOW PER SQUARE MILE

-10-15-20

-5

1050

Figure 12. Normalized low flow for selected reaches of Fountain and Monument Creeks, 1977 through 1999.
32 Trends in Precipitation and Streamflow and Changes in Stream Morphology in the Fountain Creek Watershed,

Colorado, 1939–99

Analysis indicated highly significant

changes in the Q10 streamflow regimes along

two reaches, Near CO Spgs to Nevada Street

and Nevada Street to Security (table 16). Streamflow

increased by an estimated 0.003 [(ft3

/s)/mi2/yr]

in the Near CO Spgs to Nevada Street reach and

about 0.02 [(ft3/s)/mi2/yr] in the Nevada Street to

Security reach.

Analysis indicated moderate to highly

significant changes in the Q30 streamflow regime

within four reaches: Pikeview to Nevada Street, Near

CO Spgs to Nevada Street, Nevada Street to Security,

and Security to Pinon (table 16). Estimated trend

slopes ranged from an estimated 0.003 [(ft3

/s)/mi2/yr]

in the Pikeview to Nevada Street reach to an estimated

0.025 [(ft3

/s)/mi2/yr] in the Nevada Street to Security

reach.

Trends in low streamflow that occurred

within selected reaches can be explained by:

(1) importation of non-native water, (2) increased

return flows, (3) increases in wastewater-treatmentplant discharge, and (4) changes in water management

and operations.

Relation between Precipitation and

Streamflow

The relation between precipitation and streamflow was evaluated for water years 1960 through

1997, the period when all four precipitation monitoring stations were active. Daily precipitation was

summed and average daily precipitation calculated.

Average daily precipitation was cumulated and

compared to the cumulative daily streamflow at

Pueblo using a double-mass plot (fig. 13). The analysis

revealed a marked change in the relation between

cumulative precipitation and cumulative streamflow

between 1980 and 1982. For the period 1960 through

about 1980, the relation between precipitation and

streamflow was reasonably linear with short-term

deviations in the slope, providing a baseline relation.

Between 1980 and 1982, cumulative streamflow

increased more rapidly than cumulative precipitation,

as indicated by the large deviation from the baseline

relation (fig. 13). As a result of the deviation, a new

relation was established; the new relation continued

through the end of water year 1997.

Table 16. Kendall trend analyses for the 0th, 10th, and 30th percentiles of normalized streamflow for the post-1976 time

period

[Shaded p-values indicate reaches and time periods with significant trend; ft3/s, cubic feet per second; mi2, square mile; yr, year; see figure 1 for location]

Stream reach Time period

(water years) Kendall tau Two-sidep-value

Trend slope

[(ft3/s)/mi2/yr]

Annual minimum (daily mean) streamflow (Q0)

Pikeview to Nevada Street 1977–99 0.02 0.9157 0.0003

Near CO Spgs to Nevada Street 1977–99 0.43 0.0047 0.0030

Nevada Street to Security 1977–99 0.28 0.0641 0.0338

Security to Pinon 1977–99 −0.15 0.3417 −0.0140

Pinon to Pueblo 1977–99 0.26 0.0811 0.1136

Annual 10th percentile of daily streamflow (Q10)

Pikeview to Nevada Street 1977–99 0.23 0.1243 0.0020

Near CO Spgs to Nevada Street 1977–99 0.48 0.0015 0.0029

Nevada Street to Security 1977–99 0.60 0.0001 0.0203

Security to Pinon 1977–99 0.24 0.1191 0.0024

Pinon to Pueblo 1977–99 0.11 0.4743 0.0026

Annual 30th percentile of daily streamflow (Q30)

Pikeview to Nevada Street 1977–99 0.27 0.0716 0.0026

Near CO Spgs to Nevada Street 1977–99 0.53 0.0004 0.0035

Nevada Street to Security 1977–99 0.59 0.0001 0.0251

Security to Pinon 1977–99 0.36 0.0184 0.0039

Pinon to Pueblo 1977–99 −0.12 0.4417 −0.0015
STREAMFLOW 33

0 100 200 300 400 500 600

CUMULATIVE PRECIPITATION, IN INCHES

0

1,300,000

100,000

200,000

300,000

400,000

500,000

600,000

700,000

800,000

900,000

1,000,000

1,100,000

1,200,000

CUMULATIVE STREAMFLOW, IN CUBIC FEET PER SECOND

Cumulative average precipitation relative

to cumulative daily-mean streamflow

Line (dashed) indicating baseline relation (1960-80 water years)

between cumulative average precipitation and cumulative 

daily-mean streamflow

Major change in relation between cumulative 

average precipitation and cumulative 

daily-mean streamflow

1980

1982

Line (dashed-dotted) indicating new relation (1980-97 water years) between 

cumulative average precipitation and cumulative daily-mean streamflow

Figure 13. Relation between cumulative average precipitation at four precipitation gages in the Fountain Creek watershed and cumulative daily-mean streamflow at Pueblo, October 1959 through August 1997.
34 Trends in Precipitation and Streamflow and Changes in Stream Morphology in the Fountain Creek Watershed,

Colorado, 1939–99

A seasonal evaluation of the relation between

precipitation and streamflow was conducted for the

typically dry base-flow months of November through

February and the wetter snowmelt and summer

months of March through October to determine if the

influence of spring snowmelt and summer thunderstorms were biasing the interpretation of the relation.

Precipitation and streamflow that coincided with dry

and wetter periods were summed, averaged, and

cumulated as before and compared using a doublemass curve (fig. 14). The analysis indicated that

changes in the relation between precipitation and

streamflow were nearly identical for the dry months of

November through February and the wetter months of

April through October. The similarity in the relation

between the full year, the wetter months of March

through October, and the dry months of November

through February, a period which typically receives

less than 15 percent of the total annual precipitation,

suggests that changes in water management in the

watershed had a pronounced effect on streamflow in

the watershed, particularly downstream from Colorado

Springs.

Several plausible reasons exist for the observed

changes between cumulative precipitation and streamflow relation: (1) importation of transbasin water from

outside the watershed, increased return flows, or

changes in water operations could explain part of

the increase in streamflow without a corresponding

increase in precipitation; (2) the sparse spatial distribution of precipitation stations may have inadequately

measured annual precipitation in the watershed, and

therefore the relation between precipitation and

streamflow was not accurately defined; (3) changes in

land use within the watershed could have altered the

hydrologic response of the watershed to precipitation

events; or (4) observed changes in the relation between

streamflow and precipitation in the watershed are due

to a combination of these variables.

Synthesis of Streamflow Analysis

In general, instantaneous peak streamflows have

not changed significantly during the periods of available record at most of the stations evaluated. The

exceptions are that peak streamflows at Security

have changed significantly since 1965 and peak

streamflows at Pikeview have changed significantly

since 1977.

Significant upward trends were detected in other

high daily-mean streamflow statistics (Q70, Q90, Q100,

7-, 14-, 30-day high streamflow duration) at the two

stations, Near CO Spgs and Security, that had continuous streamflow record dating back to the mid-1950’s

and mid-1960’s. After the streamflow records were

divided into the pre-1977 and post-1976 time periods,

no significant trends occurred in these high streamflow

statistics for the pre-1977 time period. For the post1976 period, highly to moderately significant upward

trends in some of these high streamflow statistics were

detected at most stations. The larger frequencies and

high significance level of trends detected in the Q70

streamflow regime may be an indication that changes

in land use within the watershed have increased the

rate and magnitude of runoff for more moderate rainfall events that occur more frequently in the watershed

than extreme rainfall events that affect the peak and

annual maximum streamflows.

Analysis of low streamflow statistics (Q0, Q10,

Q30, 7-, 14-, 30-day low streamflow duration) generally indicates that the low streamflow regime has

significantly increased throughout most of the watershed, particularly since the early 1980’s. In addition,

the average annual rate of increase in streamflow has

tended to be largest at the stations downstream from

Nevada Street. The increase in the low streamflow

regime may be attributed to changes in water management including management of the Fountain Creek

transbasin return-flow exchange decree, increases in

wastewater effluent, and return flow from lawn

watering and crop irrigation.

Analysis of changes in streamflow for

five stream reaches also indicated that significant

upward trends in high- and low-flow regimes

have occurred within four reaches: Pikeview to

Nevada Street, Near CO Spgs to Nevada Street,

Nevada Street to Security, and Security to Pinon.

Generally, the reach between Nevada Street and

Security indicated a greater magnitude in the rate

of increase in high streamflows than the other three

reaches where significant trends were detected.

Within this reach, the estimated annual increase

in Q70 and Q90 streamflow was about 5 times larger

than the estimated annual increase in the other three

reaches that had significant upward trends. This trend

is probably attributable to changes in the land use from

rangeland to urban that occurred in the intervening

drainage area over the past 23 years, altering the

hydrologic response and increasing storm runoff.
STREAMFLOW 35

340,000

80,00060,00040,00020,000

320,000300,000280,000260,000240,000220,000200,000180,000160,000140,000120,000100,000

CUMULATIVE STREAMFLOW, IN CUBIC FEET PER SECOND

0

0

70 10 20 30 40 50 60

CUMULATIVE PRECIPITATION, IN INCHES

0 600 100 200 300 400 500

CUMULATIVE PRECIPITATION, IN INCHES

0

1,000,000

900,000800,000700,000600,000500,000400,000300,000200,000100,000

Line (dashed-dotted) indicating new relation between cumulative average precipitation and cumulative daily-mean streamflow

Line (dashed) indicating baseline relationbetween cumulative average precipitationand cumulative daily-mean streamflow

Line (dashed) indicating baseline relationbetween cumulative average precipitation and cumulative daily-mean streamflow

1980

1982

1982

1980

Cumulative average precipitation relative

to cumulative daily-mean streamflow,November through February

Line (dashed-dotted) indicating new relation between cumulative average precipitation and cumulative daily-mean streamflow

Cumulative average precipitation relative

to cumulative daily-mean streamflow,March through October

Figure 14. Relation between cumulative average precipitation at four precipitation gages in the Fountain Creek watershed and cumulative daily-mean streamflow at Pueblo, November through March and April through October, 1959

–97.
36 Trends in Precipitation and Streamflow and Changes in Stream Morphology in the Fountain Creek Watershed,

Colorado, 1939–99

The significant increase and large annual increase

in the low streamflow regime in the reach between

Nevada Street and Security have resulted from

increased wastewater-treatment plant discharge associated with population growth and importation of transbasin water and management of Fountain Creek

transbasin return-flow exchange decree.

The relation between streamflow at Pueblo

and average precipitation in the watershed was evaluated. A marked change in the relation between streamflow and cumulative precipitation occurred between

1980 and 1982. A seasonal evaluation indicated that

similar breaks occurred in the relation of cumulative

streamflow and cumulative average precipitation for

the base flow and snowmelt/summer flow regimes.

This similarity indicates that changes in water

management have had a marked effect on streamflow

regimes for the entire year and not only during the

base-flow period when precipitation is minimal. Other

plausible reasons for the observed changes in the

relation between precipitation and streamflow are:

(1) the sparse spatial distribution of precipitation

stations may have inadequately measured annual

precipitation in the watershed, and therefore, the

relation between precipitation and streamflow was

not accurately defined; (2) changes in land use within

the watershed could have altered the hydrologic

response of the watershed to precipitation events; or

(3) observed changes in the relation between streamflow and precipitation in the watershed are due to a

combination of these variables.

STREAM MORPHOLOGY

Stream channels naturally change over time in

response to streamflow characteristics and sediment

delivery from the surrounding watershed (Leopold,

and others, 1964; Schumm, 1977; Karlinger and

others, 1983). Change in streamflow characteristics

and(or) sediment delivery from the surrounding watershed will in turn initiate a series of responses

as the channel adjusts to the changes.

Generalized Stream Channel

Characteristics

Fountain and Monument Creeks are the

primary perennial streams in the watershed. Although

detailed morphological characterization of Fountain

and Monument Creeks is beyond the scope of this

report, in general, morphological characteristics of

Fountain and Monument Creeks differ downstream

from their origins in the Rampart Range to the confluence of Fountain Creek and the Arkansas River

(fig. 1). Channel gradients decrease for both streams

from the mountainous regions to the alluvial valley.

Channel shape ranges from steep and narrow in the

mountainous regions to broad and flat in the alluvial

valley. The main sources of streamflow to Fountain

and Monument Creeks are snowmelt, runoff from

thunderstorms, wastewater-treatment-plant discharge,

and irrigation return flows from municipal and agricultural water use.

Fountain Creek originates in the Pike National

Forest at an elevation of about 9,200 ft near the

community of Woodland Park (fig. 1). Fountain Creek

generally flows to the southeast through the communities of Manitou Springs, Colorado Springs, Security,

and Fountain and then south to Pueblo and the confluence with the Arkansas River. The stream channel

upstream from Manitou Springs is characterized as

meandering with a step-pool regime; bed material

ranges from sand and gravel to cobbles and boulders.

From Manitou Springs to the confluence with

Monument Creek, Fountain Creek flows through a

series of alluvial terraces into a wide alluvial valley.

The stream channel in this valley is characterized as

meandering with a pool-and-riffle regime and has bed

material composed predominantly of sand, gravel,

and cobbles. Downstream from the confluence with

Monument Creek to the confluence with the Arkansas

River, the channel of Fountain Creek is generally characterized as braided, and bed and bank material is

predominantly sand and gravel. In this reach, the

alluvial valley can be described as an arroyolike

feature bounded on both sides by a steep, scarplike

break that separates the active flood plain and high

terraces (John Elliott, U.S. Geological Survey, written

commun., 1999) upon which county roads, State and

Federal highways, and railroad railbeds are located.

Active streambank erosion is evident throughout this

reach of the channel.

Monument Creek also originates in the Pike

National Forest at an elevation of about 9,200 ft and

flows east-northeast to the communities of Palmer

Lake and Monument, then south to Colorado Springs

and the confluence with Fountain Creek. Upstream

from the confluence with Cottonwood Creek, the

stream channel is characterized as meandering with a

riffle-and-pool regime and has bed material consisting

of sand, gravel, and cobbles (von Guerard, 1988). Just
STREAM MORPHOLOGY 37

upstream from the confluence with Cottonwood Creek

and continuing through the city limits, the streamchannel banks are lined with concrete and the channel

becomes constrained laterally and possibly detached

from the flood plain. Bed material is composed

predominantly of sand and gravel.

Sediment Transport Capacity

The ability of streamflow to transport sediment

(transport capacity) can be described by using the

Shields dimensionless shear-stress relation for estimating the particle size of bed material at the threshold

of movement (von Guerard, 1989). Maximum particle

sizes of bed material that can be transported for

various streamflows were estimated by using the

following equation (von Guerard, 1989; Elliott

and others, 1984):

(2)

where

dc = particle size of bed material, in millimeters,

at threshold of movement;

= mean channel depth, in feet;

S = water-surface slope;

= ratio of specific weights of sediment and

water (2.65);

= dimensionless critical shear stress (the critical shear stress necessary for movement

of bed material); and

304.8 = a unit conversion constant, in millimeters per

foot.

Values of τ*

c of 0.045 and 0.060 were used

as the upper and lower limits for the transport of

coarse materials in Fountain Creek (von Guerard,

1989).

Streamflow and channel morphology data

collected during streamflow measurements at the

Pueblo station were used to evaluate the capacity of

streamflows to transport coarse sand and gravel of 1-

to 32-mm size fractions. Analysis indicated that the

minimum measured streamflow of 0.97 ft3

/s had the

capacity to transport coarse to very coarse sands of

1 to 2 mm. This is consistent with field observations

of bed-material transport during low-flow conditions.

Analysis also indicated that the transport of bed

material of the coarse gravel of 16- to 32-mm-size

fractions was possible as streamflows approached

and exceeded 2,000 ft3

/s. Analyses conducted by

von Guerard (1989) indicated that, in the Colorado

Springs area, Fountain and Monument Creeks were

capable of transporting bed material of grain sizes

similar to bed material at the Pueblo station.

Descriptive Assessment of Changes in

Channel Morphology

Dramatic changes in channel morphology are

most often associated with infrequent or catastrophic

floods that cause rapid changes in channel shape and

(or) location and capture the attention of area residents. Peak annual streamflow events greater than

10,000 ft3

/s on Fountain Creek at Pueblo occurred in

1921, 1924, 1935, 1942, 1944–46, 1951, 1955, 1965,

1980, 1994–97, and 1999. However, more frequent

conditions associated with bankfull streamflow,

while less striking, are considered to be the dominant

force in development and maintenance of channel

morphology (Leopold and others, 1964; Rosgen,

1996).

Changes in channel morphology along four

reaches of Fountain Creek (fig. 1) were investigated

using periodic aerial photography and field reconnaissance. River reaches R1, R2, and R3 were two linear

miles long and extended north from the Highway 47

bridge (R1), extended 1 mile upstream and 1 mile

downstream from the Overton Road bridge (R2),

and extended north from the Pinon Road bridge (R3).

River reach R4 extended about 20 miles from the town

of Widefield to the Pinon Road bridge. Reconnaissance trips were conducted in April, May, September,

and October of 1999. The September 1999 reconnaisance of river reach R4 from Widefield to the Pinon

Road bridge was conducted by canoeing down

Fountain Creek. All other reconnaisance was

conducted by driving a motor vehicle to locations

in or near the respective reaches and hiking to and

along Fountain Creek. Evaluation of these four river

reaches was used to make a general descriptive assessment of changes in channel morphology that occurred

immediately after and during the interval between

large streamflow events.

dc DS

γs

γw

------     – 1     τ

*

c    

---------------------------------------

   

 

= ( ) 308.4

D

γs

γw

------

τ

*

c
38 Trends in Precipitation and Streamflow and Changes in Stream Morphology in the Fountain Creek Watershed,

Colorado, 1939–99

Analysis of aerial photographs taken in 1947,

1955, 1960, 1970, 1980, 1991, 1993, and 1999 indicated a pattern to changes in vegetation, channel

width and length, and location of Fountain Creek

within the alluvial valley between the steep scarps of

the bounding high terrace. Initial aerial photography

taken in 1947 and 1955 indicated sandbars denuded of

vegetation. Spatial distribution of vegetation in the

flood plain varied and generally was sparse. The

sparseness of vegetation along Fountain Creek shown

in the 1947 and 1955 aerial photographs represents a

period when streamflow in lower Fountain Creek was

intermittent, due to diversion of all streamflow for irrigation prior to increased low streamflows in the 1980’s

and 1990’s, as noted earlier. The sparseness is also

indicative of changes in vegetation in the alluvial

valley following streamflow events of 10,000 ft3/s or

greater, as recorded at Pueblo. Streamflow events of

this magnitude occurred in the months or years immediately prior to the 1947 and 1955 aerial photographs.

Streamflow events of 10,000 ft3/s at Pueblo have an

annual exceedance probability of 0.2, meaning that

flows of this magnitude have a probability of occurring

once every 5 years (5-yr flood) and are, hereinafter,

referred to as large streamflow events. Aerial photography taken in 1970 and 1991 following extended

periods of time during which streamflows at Pueblo

did not exceed 10,000 ft3

/s indicated a gradual

return of vegetation to the flood plain and sandbars.

The increase in vegetation appeared more striking in

aerial photographs taken in 1991 and 1993 than 1970

and may be related to the lack of large streamflow

events during the 1981 to 1993 time period, or to

increased water availability due to increased low flows

as noted in previous sections, or both. Aerial photographs taken in May 1999 again show the effects of

large streamflow events. Extensive streambank and

flood-plain erosion and the subsequent removal of

vegetation were noted throughout much of river

reaches R1, R2, and R3.

Visible changes in channel width, length,

and location between the scarps of the high terrace

were only observed in photographs taken after large

streamflow events. Morphological changes after large

streamflow events included increased channel width

as banks and flood plain were scoured of vegetation;

altered channel course as floodwaters reoccupied

previously abandoned meanders or eroded valley

alluvium to create a new channel; straightened channels as streamflow cut off meanders, thus shortening

the stream reach; and increased meander amplitude

as cutbanks at meander bends were further eroded

by the energy of the floodwaters.

Increasing meander amplitude and channel

migration were evident at the Overton Road bridge,

the centroid of river reach R2 (fig. 15). At the centroid

of R2, Fountain Creek flows in a wide meander from

the northwest to the base of a high terrace and then

southwest. The high terrace at this location is approximately 50 ft above the alluvial valley. Moderate to

high streamflows in this meander undercut the high

terrace. As the high terrace is undercut, large blocks of

overlying material collapse into Fountain Creek. From

1955 to 1999, erosion of the cutbank or outer bank of

the meander (fig. 16) resulted in eastward migration of

the edge of the high terrace by approximately 280 ft.

The eastward migration has occurred at increasing

rates since 1970. Despite the historical peak streamflows of 1965, no appreciable changes in the distance

between the edge of the high terrace and Overton

Road were noted in aerial photographs taken between

1955 and 1970. During the period from 1970 to 1991,

one large streamflow event occurred (1980) and the

edge of the high terrace moved eastward approximately 100 ft, an average rate of about 5 ft per

year. During the period from 1991 to 1999, five

large streamflow events occurred and erosion of the

cutbank resulted in the migration of the edge of the

high terrace eastward about 160 ft, an average rate

of about 20 ft per year. Reconnaissance from atop the

high terrace prior to and after the April 1999 flood

revealed that the edge of the high terrace migrated

eastward about 15 ft (fig. 16) as a result of the high

streamflows during the spring of 1999. Similar examples of erosion of the high terrace during the 1999

flood were observed or documented throughout the

Fountain Creek watershed (Jay Frost, landowner,

oral commun., 1999; Mackey and Williamson, written

commun., 1999).

Analysis of aerial photography provided other

examples of channel migration within river reaches

R1, R2, and R3. Between 1955 and 1970, westward

channel migration of approximately 1,000 ft occurred

along the upper 1-mile stretch of reach R2 and 1,500 ft

of a 0.2-mile stretch of reach R3. The apparent

cause of channel migration was erosion of streambank

and flood-plain sediments during the flood of 1965.
STREAM MORPHOLOGY 39

Subsequent aerial photography revealed that high

streamflows since 1965 have at times reoccupied

all or parts of the abandoned channel.

Reconnaissance of Fountain Creek following

the 1999 flood revealed the erosive power of the

floodwaters as well as the sediment deposition as

floodwaters receded. Structures and property affected

by channel erosion and migration during the flood

included railway roadbeds, bridges, roadways, and

farmland. Extensive areas of the flood plain were

also denuded of vegetation. News broadcasts during

the flood and aerial photographs taken after the flood

documented the loss of mature cottonwood trees,

many of which were transported considerable

distances downstream.

Observations of flood-plain aggradation prior to

the flood of 1999 of about 1-ft at fence posts (Jay Frost,

landowner, oral commun., 1999) indicate that floodplain aggradation occurred at an average rate of about

0.3 in/yr for the period 1965 through 1998. However,

it is more likely that flood-plain aggradation occurred

during the five large streamflow events of 1980, and

1994 through 1997, depositing an average 2.4 inches of

sediment during each of these large streamflow event

years. Field reconnaissance of the four river reaches

during September and October of 1999 and local

accounts (Bill Alt, landowner, oral commun., 1999)

revealed flood-plain aggradation as large amounts of

sediment were deposited in the flood plain of Fountain

Creek (fig. 17) following the 1999 flood.

More subtle changes in the channel occur at

lower streamflows. Channel erosion in the form of

bank erosion (figs. 17) and transport of bed material

was commonly observed in 1999 throughout much of

Fountain Creek from Widefield to Pueblo. Undercutting of the streambank occurs during bankfull and

lower streamflows. Assuming a large streamflow

event does not interrupt the process, bank and floodplain sediments slough from the roots of the riparian

vegetation as streamflow shifts laterally. If these

sediments were not redeposited along the bank downstream, bank undercutting and sloughing would be

followed by the eventual loss of the riparian vegetation. Channel modifications incurred during low flows

Figure 15. View looking south at the Overton Road bridge and edge of high terrace on April 26, 1999.

Following the flood of April 28 through May 5, Overton Road at this location was reduced to one lane

due to bank erosion after which the edge of the terrace extended a few feet into the southbound lane

from the near foreground to the bridge.
40 Trends in Precipitation and Streamflow and Changes in Stream Morphology in the Fountain Creek Watershed,

Colorado, 1939–99

generally progress slowly and are not as obvious or

striking as those incurred during large streamflow

events but are still important.

During periods lacking large streamflow events,

1970–80 and 1980–93, gradual increases in vegetation

were noted along the streambank, sandbars, and flood

plain. In conjunction with increases in streambank

vegetation, mean channel widths decreased, and little

if any change in channel location and length was noted.

The apparent stability and lack of channel erosion as

viewed in aerial photographs does not imply that

changes were not occurring, only that they were not

visible at the resolution available in the aerial photographs.

Channel aggradation may also be occurring,

particularly in reaches within the lower one-half of

reach R4. Reconnaissance during September 1999

revealed that the channel width and depth gradually

changed from the upper one-half to the lower one-half

of reach R4. The channel in the upper one-half of R4

was characterized by a relatively narrow channel with

moderate flow depths capable of being canoed. The

channel in the lower one-half of R4 was characterized

by a broader channel with numerous sandbars and

very shallow streamflow that generally was not negotiable by canoe. Based on observations made during

the reconnaissance, it appears that sediment transport

capabilities diminish in the lower one-half relative to

the upper one-half of R4, resulting in the development

of broad sandbars. With the diminished transport of

stream sediments, streambed elevation increases,

streamflow becomes shallower and flows over a

broader area, and flow paths tend to move laterally,

eroding bank sediments and periodically reworking

the bed sediments.

Direction

of streamflow

Overton Road

Overton Road bridge

Fountain

Creek

Figure 16. Aerial photograph of Fountain Creek at the Overton

Road bridge in September 1991 and periodic changes in the

general location of the high terrace from 1955 and 1970 (dashed

line) through 1999 (dotted line) after the April 1999 flood.
SUMMARY AND CONCLUSIONS 41

Several plausible reasons exist for the

observed changes in streambank erosion and channel migration. (1) Mass wasting of streambanks and

the high terrace has been documented during and

following large streamflow events. Accelerated

rates of this type of erosion are the direct result of

the increased frequency of large storm events and

subsequent floods during the mid- to late-1990’s and

increased low streamflows of the 1980’s and 1990’s.

(2) Differences in sedimentation patterns within

selected reaches may be increasing streambed elevation, causing lateral shifts in flow paths. Increasing

stage and(or) lateral shifts in the path of streamflow

in Fountain Creek would cause erosion and instability

of streambank sediments. Even with vegetation cover,

coarse to very coarse sand is easily eroded. (3) Bankfull to low flows appear to be laterally eroding streambanks and aiding in the collapse of undercut regions

of the high terrace. Estimates of sediment-transport

capacity indicate that streamflows as low as 1.0 ft3

/s

are capable of reworking the coarse sands to very

coarse sands that are the predominant streambed

and streambank sediments. Further investigation is

needed to evaluate sedimentation characteristics

of Fountain Creek and its effects on channel

morphology.

SUMMARY AND CONCLUSIONS

Precipitation characteristics and trends in total

annual and seasonal precipitation were evaluated for

four stations in the Fountain Creek watershed.

1. An analysis of the pre-1977 period indicates

that annual precipitation was generally below

average, and no trends were detected in annual

precipitation. An analysis of the post-1976 period

indicates that annual precipitation was generally

above average and upward trends were detected

at the Ruxton Park and Pueblo stations.

2. There has been no change in the distribution or

magnitude of rainfall occurring during a 24-hour

period. However, mean annual precipitation was

significantly greater during the post-1976 period

than the pre-1977 period at Colorado Springs,

Fountain, and Pueblo. Therefore, the differences

between the two periods result from more days

with rainfall rather than more rain during any

given day.

3. An analysis of the pre-1977 period indicated no

significant trend during any season. An analysis

of the post-1976 period indicated moderately

significant upward trends in spring precipitation

at the Ruxton Park and Pueblo stations. The

upward trends in annual precipitation for the

Figure 17. Streambank erosion and sediment deposition on the flood plain of Fountain Creek.
42 Trends in Precipitation and Streamflow and Changes in Stream Morphology in the Fountain Creek Watershed,

Colorado, 1939–99

post-1976 period at the Ruxton Park and Pueblo

stations are likely a result of the upward trends in

spring precipitation at these stations.

Streamflow in the Fountain Creek watershed has

three distinct flow regimes: base flow, spring snowmelt

and storm runoff during the summer monsoon period.

Trends in streamflow were evaluated for six stations in

the Fountain Creek watershed. Data were divided into

pre-1977, post-1976, and period of record time periods.

Trends in annual instantaneous peak streamflow, 70th

percentile, 90th percentile, maximum daily-mean

streamflow (100th percentile), 7-, 14-, and 30-day

high-flow duration, minimum daily-mean streamflow

(0th percentile), 10th percentile, 30th percentile,

and 7-, 14-, 30-day low-flow duration were evaluated.

1. In general, instantaneous peak streamflows have not

changed significantly during the periods of available record at most of the stations evaluated. The

exceptions being, peak streamflows at Security

have changed significantly since 1965 and peak

streamflows at Pikeview have changed significantly since 1977.

2. Significant upward trends were detected in other

high streamflow statistics (Q70, Q90, Q100, 7-,

14-, 30-day high daily-mean streamflow duration) at the two stations that had continuous

streamflow record dating back to the mid-1950’s

and mid-1960’s. After the streamflow records

were divided into the pre-1977 and post-1976

time periods, no significant trends occurred in

these high streamflow statistics for the pre-1977

time period. For the post-1976 period, highly to

moderately significant upward trends in some of

these high streamflow statistics were detected at

most stations. The larger frequencies and high

significance level of trends detected in the Q70

streamflow regime may be an indication that

changes in land use within the watershed have

increased the rate and magnitude of runoff for

more moderate rainfall events that occur more

frequently in the watershed than extreme rainfall

events that effect the peak and annual maximum

streamflows.

3. Analysis of low streamflow statistics (Q70, Q90,

Q100, 7-, 14-, 30-day low streamflow duration)

generally indicate that the low streamflow regime

has significantly increased throughout most of

the watershed, particularly since the early 1980’s.

The increase in the low streamflow regime may

be attributed to changes in water management

including management of the Fountain Creek

transbasin return-flow exchange decree, increases

in wastewater effluent, and return flow from lawn

watering and crop irrigation.

4. Analysis of changes in streamflow for five stream

reaches also indicated that significant increasing

trends in high- and low-flow regimes have

occurred. Trends are probably attributable to

changes in the land use from rangeland to urban

that occurred over the past 23 years altering the

hydrologic response and increasing storm runoff,

increased wastewater-treatment-plant discharge

associated with population growth, and importation of transbasin water and management of

Fountain Creek transbasin return-flow exchange

decree.

5. The relation between streamflow at Pueblo and

average precipitation in the watershed was evaluated. A marked change in the relation between

daily-mean streamflow and cumulative average

precipitation occurred between 1980 and 1982.

A seasonal evaluation indicated that similar

breaks occurred in the relation of cumulative

streamflow and cumulative average precipitation

for the base flow and snowmelt/summer flow

regimes. This similarity indicates that changes in

water management have had a marked effect on

streamflow regimes for the entire year and not

only during the base-flow period when precipitation is minimal. Other plausible reasons for the

observed changes in the relation between precipitation and streamflow include (1) the sparse

spatial distribution of precipitation stations may

have inadequately measured annual precipitation

in the watershed, and therefore, the relation

between precipitation and streamflow was not

accurately defined; (2) changes in land use within

the watershed could have altered the hydrologic

response of the watershed to precipitation events;

or (3) observed changes in the relation between

streamflow and precipitation in the watershed

are due to a combination of these variables.

Bed and bank material of Fountain Creek is

composed predominantly of sand and gravel. The

capacity of streamflows in Fountain Creek at Pueblo

to transport sediment in the sand- and gravel-size fractions was evaluated. Estimates of transport capacity

indicate that streamflows less than 1 ft3/s had the

capacity to transport coarse to very coarse sands

of the 1- to 2-mm-size fraction, and streamflows of

2,000 ft3

/s or more had the capacity to transport very

coarse gravel in the 32-mm-size fraction.
SELECTED REFERENCES 43

Changes in channel morphology within four

reaches of Fountain Creek were evaluated with aerial

photography and field reconnaissance.

1. Analysis indicated changes in vegetation and

channel characteristics were associated with the

frequency of large streamflow events. Sandbars,

streambanks, and the flood plain were denuded

following large streamflow events, whereas

gradual revegetation occurred over extended

time periods that lacked large streamflow events.

2. While subtle, erosion caused by low streamflows

were an important component of day-to-day

channel erosion.

3. Substantial changes in channel morphology were

most often associated with infrequent large

or catastrophic streamflow events that erode

streambed and banks, alter stream course, and

deposit large amounts of sediment in the flood

plain.

SELECTED REFERENCES

Buchanan, T. J., and Somers, W.P., 1968, Stage measurement at gaging stations: U.S. Geological Survey Techniques of Water-Resources Investigations, book 3,

chap. A7, 28 p.

Carter, R.W., and Davidian, Jacob, 1968, General procedure

for gaging streams: U.S. Geological Survey Techniques of Water-Resources Investigations, book 3,

chap. A6, 13 p.

Colorado Climate Center, 1999,

http://ulysses.atmos.colostate.edu/dly_form.html,

accessed February 2, 2000.

Douglas, Ian, 1983, The urban environment: Baltimore,

Edward Arnold Publishers Ltd., 229 p.

Dunne, Thomas, and Leopold, L.B., 1978, Water in environmental planning: New York, W. H. Freeman and

Company, 818 p.

Elliott, J.G., Kircher, J.E., and von Guerard, Paul, 1984,

Sediment transport in the Lower Yampa River, Northwestern Colorado: U.S. Geological Survey WaterResources Investigations Report 84–4141, 44 p.

GEI Consultants, Inc., 1998, SECWCD/Arkansas Basin

future water and storage needs assessment: Englewood, Colo., 192 p.

Giannasca, Frank, 1999, Where west’s summer rain comes

from, http://www.usatoday.com/weather/wtsm5.htm,

accessed February 2, 2000.

Goudie, Andrew, 1986, The human impact on the natural

environment: Cambridge, Mass., The MIT Press,

338 p.

Hansen, W.R., Chronic, John, and Matelock, John, 1978,

Climatography of the Front Range urban corridor and

vicinity, Colorado: U.S. Geological Survey Professional Paper 1019, 59 p.

Helsel, D.R., and Hirsch, R.M., 1995, Statistical methods in

water resources: New York, Elsevier Science, 529 p.

Karlinger, M.R., Eschner, T.R., Hadley, R.F., and Kircher,

J.E., 1983, Relation of channel-width maintenance to

sediment transport and river morphology—Platte

River, south-central Nebraska: U.S. Geological Survey

Professional Paper 1277–E, 19 p.

Kennedy, E.J., 1983, Computation of continuous records of

streamflow: U.S. Geological Survey Techniques of

Water-Resources Investigations, book 3, chap. A13,

53 p.

———1984, Discharge ratings at gaging stations: U.S.

Geological Survey Techniques of Water-Resources

Investigations, book 3, chap. A10, 59 p.

Leopold, L.B., Wolman, M.G., and Miller, J.P., 1964,

Fluvial processes in geomorphology: New York, Dover

Publications, Inc., 522 p.

Lins, H.F. and Slack, J.R., 1999, Streamflow trends in the

United States: Geophysical Research Letters, v. 26,

no. 2, p. 227–230.

National Oceanic and Atmospheric Administration, 1999,

Noteworthy Colorado floods, http://www.crh.noaa.gov/

den/floods.html, accessed January 25, 2000.

Ott, Lyman, 1993, An introduction to statistical methods

and data analysis (4th ed.): Belmont, Calif., Duxbury

Press, 1051 p.

Rosgen, Dave, 1996, Applied river morphology: Pagosa

Springs, Colo., Wildland Hydrology, 352 p.

Schumm, S.A., 1977, The fluvial system: New York,

John Wiley and Sons, 338 p.

Searcy, J.K., and Hardison, C.H., 1960, Double-mass

curves, manual of hydrology–Part 1. General surfacewater techniques: U.S. Geological Survey WaterSupply Paper 1541–B, 66 p.

Snipes, R.J., 1974, Floods of June 1965 in Arkansas River

Basin, Colorado, Kansas, and New Mexico: U.S.

Geological Survey Water-Supply Paper 1850–D, 97 p.

von Guerard, Paul, 1988, Suspended sediment and sediment

source areas in the Fountain Creek drainage basin

upstream from Widefield, southeastern Colorado:

U.S. Geological Survey Water-Resources Investigations Report 88–4136, 36 p.

———1989, Sediment-transport characteristics and

effects of sediment transport on benthic invertebrates

in the Fountain Creek drainage basin upstream from

Widefield, southeastern Colorado, 1985–1988:

U.S. Geological Survey Water-Resources Investigations Report 89–4161, 133 p.

Wells, J.V.B., 1959, Surface-water supply of the United

States, 1957: U.S. Geological Survey Water-Supply

Paper 1511–D, 527 p.