U.S. Department of the Interior

U.S. Geological Survey

Fact Sheet 2010–3030

June 2010

Hydrology of Johnson Creek Basin, a Mixed-Use Drainage 

Basin in the Portland, Oregon, Metropolitan Area

Johnson Creek forms a wildlife and recreational corridor through densely 

populated areas of the Portland, Oregon, metropolitan area and through rural 

and agricultural land in unincorporated Multnomah and Clackamas Counties. 

Johnson Creek has had a history of persistent flooding and water-quality 

problems. The U.S. Geological Survey (USGS) has conducted streamflow 

monitoring and other hydrologic studies in the basin since 1941.

Basin Description

Johnson Creek is about 26 miles long and drains an area of about 54 

square miles (fig. 1). The headwaters as well as the several tributaries on the 

southern side of the basin originate in volcanic hills. Johnson Creek arises 

in unincorporated agricultural areas and flows westward through the cities 

of Gresham, Portland, and Milwaukie, where it enters the Willamette River. 

The largest tributary is Kelley Creek, which enters Johnson Creek from the 

south in midbasin (fig. 2). Few tributaries flow into Johnson Creek from 

the relatively flat area north of the stream because water percolates into the 

permeable deposits left by massive glacial outburst floods that coursed through 

the Columbia River basin during the last ice age. The primary northern 

tributary is Crystal Springs Creek, which enters Johnson Creek about a mile 

from the mouth. 

The Johnson Creek basin has a temperate marine climate, with wet 

winters and dry summers. About two-thirds of the annual precipitation, nearly 

all rain, falls from November through March. Annual precipitation in the basin 

decreases with elevation, from more than 60 inches in the uplands of the upper 

basin to about 40 inches at the mouth of the creek, near sea level. 

Figure 1. The Johnson Creek basin, Oregon.

Johnson Creek drains diverse landscapes. Top to bottom: Rural 

upper basin stream, upper basin nursery, commercial/industrial 

area near the mouth at the Portland–Milwaukie city boundary. 

(Photographs by Karl Lee, U.S. Geological Survey, August 29, 2003 

[top and middle] and January 17, 2007 [bottom].)

Printed on recycled paper

RIVER

Sandy

Eagle

COLUMBIA

Willamette

Columbia Slough

Creek

Creek

Clackamas

River

River

River

Creek

Fanno Tualati

Johnson

n

MULTNOMAH

CLACKAMAS

212

99W

212

224

43

217 

211

99E 14

26

205

205

405

5

84 Johnson Creek 

drainage basin

Portland

Gresham

MilwaukieMilwaukie Happy 

Valley

DamascusDamascus

Portland

International Airport

122°45' 122°30' 122°15'

45°

35'

45°

30'

45°

20'

45°

25'

0 2 4 6 8 10 MILES

0 2 4 6 8 10 KILOMETERS

Base modified from U.S. Geological Survey data and other digital sources. 

Projection: UTM, Zone 10N, North American Datum 1983, 

Scale factor= 0.9996, False easting = 500,000, False northing = 0.
Land cover in the Johnson Creek basin 

generally follows a gradient from forested, 

agricultural, and rural-residential areas in the 

headwaters to urban and industrial development 

in the lower basin (fig. 2). About three-quarters 

of the basin is rural and open space; the rest is 

residential, commercial, and industrial. Urban 

development in recent years has resulted in the 

widespread conversion of agricultural lands to 

residential use. Land cover in the southern part 

of the basin includes forest, nurseries, row crops, 

and light to dense urban development. Future 

expansion of the cities of Gresham, Damascus, 

Happy Valley, and Portland, and possibly new 

urban centers, likely will result in conversion 

of current agricultural and light-residential 

development to a densely urban land use, if 

current trends continue. The northern part of the 

basin that is within the Portland metropolitan 

area is already densely populated.

Hydrology

Streamflow in Johnson Creek is derived 

from precipitation runoff and groundwater 

discharge. Groundwater discharge is particularly 

important in maintaining summer flows. In some 

areas of the Johnson Creek basin, particularly 

along the northern boundary, the direction of 

groundwater flow is not toward Johnson Creek 

or its tributaries but out of the drainage basin 

toward the lower-elevation Sandy, Columbia, or 

Willamette Rivers. As a result, recharge to the 

Crystal Springs Creek, shown here near its confluence with Johnson Creek, is one of the largest 

tributaries to Johnson Creek. (Photograph by Karl Lee, October 1, 2008.)

Figure 2. The Johnson Creek basin has a mix of land covers, which grade from forest and agricultural land in the upper basin to urban and 

industrial development in the lower basin.

45° 30'

45° 25'

122°37'30" 122°30'00" 122°22'30"

Land cover category

Water

Barren and urban

Agriculture

Forest (closed canopy)

Forest (open canopy) and shrub

Meadow and grass

EXPLANATION

MULTNOMAH

COUNTY

CLACKAMAS

COUNTY

Johnson Creek drainage boundary

Crystal Springs

Johnson Creek

Veterans Creek

Kelley Creek

Mitchell Cr

Johns on Creek

Johnson Creek

Clatsop Cr

Creek

Crystal Springs

Johnson Creek

Veterans Creek

Kelley Creek

Mitchell Cr

Johns on Creek

Hogan CreekHogan Creek

Johnson Creek

WILLAMETTE

RIVER

Clatsop Cr

Creek Butler Creek

Butler Creek

N. Fork Johnson CreekN. Fork Johnson Creek

Sunshine CreekSunshine CreekSunshine Creek

Badger CreekBadger CreekBadger Creek

Study

area

Portland

OREGON

0 1 2 3 4 Miles

0 1 2 3 4 Kilometers
groundwater system within some areas of the basin does not 

discharge to Johnson Creek but instead flows out of the basin. 

The result is lower streamflows in Johnson Creek than might be 

expected for the amount of precipitation that falls on the basin.

Streamflow characteristics in an undeveloped drainage 

basin are shaped by topography, geology, and land cover. In 

the upper Johnson Creek basin, prior to human development, 

most of the precipitation ran off to streams from the steep and 

relatively impermeable volcanic soils, resulting in a rapid rise 

and fall in streamflow after storms. In the lower basin, most of 

the precipitation percolated into the ground and then discharged 

to streams through the generally flat-lying, permeable flood 

deposits, resulting in a more muted response to storms than in 

the upper basin. 

Modification of the landscape in the Johnson Creek basin 

has altered its natural hydrology. Delivery of stormwater to 

the stream in the upper basin is now expedited by agricultural 

drains and runoff from ditches, roads, and other impermeable 

surfaces, resulting in a more rapid streamflow increase 

in response to precipitation than likely occurred before 

development. In the lower, mostly urban basin, some of the 

runoff that might otherwise flow to streams across the land 

surface and in small drainages is directed to the subsurface 

through infiltration sumps (also known as “drywells”) and 

to sewer systems that discharge outside the basin. Channel 

simplification, rock lining of the stream channel, establishment 

of a network of storm drains, and paving of once-permeable 

areas also likely have affected runoff volume and response to 

precipitation.

Nonetheless, analysis of streamflow data collected 

from 1941 to 2006 in the Johnson Creek basin did not 

detect increases in peak flows and flooding that typically are 

associated with urban development. This lack of change could 

be because much of the infrastructure that affects runoff from 

residential and urban development, such as roads, ditches, 

drywells, and sewer systems, was in place prior to collection of 

hydrologic data in the basin. 

Holgate Lake appears intermittently, during periods when the water table is particularly high. (Photograph by Karl Lee, March 13, 2006.)

Streamflows are minimal in the Johnson Creek basin 

during the summer owing to a near lack of precipitation. 

Summer low flows of Johnson Creek vary from year to year 

with fluctuations in groundwater discharge to the creek, which 

are related to annual fluctuations in the amount of recharge from 

precipitation. Seepage measurements during low-flow periods 

from 1988 to 2006 indicated small contributions of groundwater 

to streamflow upstream of river mile 5.5 (about one-half mile 

west of Interstate Highway 205 [fig. 1]) and relatively large 

contributions downstream of that point owing to the differences 

in topography and aquifer characteristics between the upper and 

middle basins and the lower basin. 

Crystal Springs Creek (fig. 2) is the largest northern 

tributary to Johnson Creek. Nearly all of Crystal Springs 

Creek’s flow is supplied by springs and seepage from 

groundwater discharge that is derived either locally or from the 

middle or lower basin. Variations in streamflow of the creek 

over time can be explained by long-term trends in groundwater 

recharge and subsequent discharge to the creek. Flow increased 

following record precipitation in 1996 and 1997, and this 

increase persisted for about 4 years. In 2005, flow was the 

lowest since measurements began in 1987. A relation was 

developed during a recent study that provides an estimate of the 

flow of Crystal Springs Creek based on water level in a nearby 

well. This information can be used to anticipate both high and 

low streamflow, for protection of people, property, and wildlife.

“Holgate Lake” (as it is known locally) in Southeast 

Portland appears intermittently, sometimes inundating nearby 

residences. The lake forms when the water table rises above 

land surface. The water-surface elevation of Holgate Lake 

closely follows the elevation of the water table in a nearby 

observation well equipped with a continuous data recorder. 

Antecedent water-table elevations, coupled with fall and 

winter precipitation totals, have been used to predict the lake’s 

emergence.
Selected References 

Johnson Creek Watershed Council, 2003, Meet Johnson 

Creek: accessed March 15, 2010, at http://www.jcwc.org/

johnsonCreek/creek.htm.

Lee, K.K., and Snyder, D.T., 2009, Hydrology of the Johnson 

Creek basin, Oregon: U.S. Geological Survey Scientific 

Investigations Report 2009–5123, 56 p. (Also available at 

http://pubs.usgs.gov/sir/2009/5123/.)

Tanner, D.Q., and Lee, K.K., 2004, Organochlorine pesticides 

in the Johnson Creek basin, Oregon, 1988–2002: U.S. 

Geological Survey Scientific Investigations Report 

2004–5061, 36 p. (Also available at http://pubs.usgs.gov/

sir/2004/5061/.)

Water Quality

Summer temperatures of Johnson Creek and tributary 

streams are affected by groundwater discharge, air temperature, 

and solar radiation. Measurements of the temporal and spatial 

distribution of groundwater discharge to streams, coupled with 

comparisons of stream temperature to air temperature, suggest 

that groundwater discharge cools the stream in some reaches, 

and that significant warming occurs in stream reaches with 

shallow, unshaded ponds, such as those in Crystal Springs Creek.

High flow in Johnson Creek typically mobilizes sediment 

and sediment-borne contaminants, including organochlorine 

pesticides. Upper-basin characteristics, such as more rainfall 

and runoff, greater slopes, a network of roads and ditches 

associated with agricultural and rural-residential land uses, and 

a relative abundance of sources of sediment and sediment-borne 

contaminants, make management of runoff in the upper part of 

the basin important to the ecological health of the entire basin. 

Organochlorine pesticides were detected in unfiltered 

samples from Johnson Creek that were collected during a storm 

in March 2002. Concentrations and loads of the pesticides were 

largest at the most upstream sampling site, suggesting that 

agricultural activities were the primary source. Concentrations 

and loads were smaller at downstream locations, and there were 

only a few detections from storm drains. Total DDT (the sum of 

DDT and its metabolites) concentrations potentially exceeded 

Oregon chronic, freshwater criteria at all stream-sampling sites. 

The total DDT criterion was also potentially exceeded at an 

urban storm drain. 

The use of DDT was banned by the U.S. Environmental 

Protection Agency in 1972. Concentrations of DDT in water 

samples from Johnson Creek have decreased by an order 

of magnitude since previous sampling in 1989–1990. This 

decrease was probably due to the movement of residual, soilbound DDT out of the basin and to degradation processes. 

For More Information:

Oregon Water Science Center

2130 SW 5th Avenue, Portland, OR 97201

Phone: (503) 251-3200

E-mail: info-or@usgs.gov 

http://or.water.usgs.gov/

Johnson Creek Basin Hydrologic Monitoring Website 

http://or.water.usgs.gov/johnsoncreek

Authors: John S. Williams, Karl K. Lee, and Daniel T. Snyder 

High flows in the upper basin mobilize large amounts of sediment. (Photograph 

by Karl Lee, April 10, 2006.)

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