Water Quality Trends in the 

Entiat River Watershed: 

2007–2010

Richard D. Woodsmith, Pamela K. Wilkins, and Andy 

Bookter1

Pacific Northwest 

Research Station

Research Note 

PNW-RN-569

May 2013

DEPAR TMENT OF AGRICULT URE

1 Richard D. Woodsmith is an emeritus research hydrologist, Pamela K. Wilkins is a 

hydrologic technician, and Andy Bookter is a hydrologic technician, Forestry Sciences 

Laboratory, 1133 North Western Avenue, Wenatchee, WA 98801.

Abstract

A large, multiagency effort is underway in the interior Columbia River basin 

(ICRB) to restore salmon, trout, and char listed as threatened or endangered under 

the 1973 federal Endangered Species Act. Water quantity and quality are widely 

recognized as important components of habitat for these depleted salmonid populations. There is also broad concern about maintaining a high-quality water supply 

for other societal and ecosystem uses. A particularly active salmonid habitat restoration program is being conducted in the Entiat River, which drains a portion of the 

eastern slope of the Cascade Mountains in central Washington state. There, routine 

monitoring by the Washington Department of Ecology identifies pH and water 

temperature as water quality parameters of concern. In response, the U.S. Forest 

Service, Pacific Northwest Research Station is testing a more intensive approach to 

water quality monitoring that uses multiparameter data-logging instruments at four 

locations to measure fundamental water quality parameters (pH, water temperature, 

dissolved oxygen, and specific conductivity). This report presents results from the 

first 4 years of the study and discusses variation in water quality parameters with 

season, river discharge, and location. We demonstrate that unattended data-logging 

instruments effectively provide high-resolution data, which facilitate identification 

of forcing mechanisms such as direct solar radiation, air temperature, and river 

discharge. Results complement ongoing, broad-scale salmon recovery monitoring 

by quantifying concurrent changes in water quality. Although exploratory in nature, 

this study can inform future, more intensive monitoring programs.

Keywords: Water quality monitoring, salmon restoration, Columbia River 

basin, Entiat River.

United States Department of Agriculture

Forest Service
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RESEARCH NOTE PNW-RN-569

Introduction

An adequate supply of high-quality water is essential for the success of an ambitious, ongoing program to restore depleted salmonid populations in the largely 

semiarid, interior Columbia River basin (ICRB). This restoration is a cooperative 

effort among a number of governmental agencies, tribes, communities, and nongovernmental organizations (UCSRB 2012). The Bonneville Power Administration 

(BPA) is a primary sponsor of ICRB restoration efforts and is the primary funder 

of the National Oceanic and Atmospheric Administration (NOAA-Fisheries), 

Integrated Status and Effectiveness Monitoring Program (ISEMP) (BPA 2012). The 

ISEMP leads development of a regionwide program to assess the status of anadromous salmonid populations and their tributary habitat and to monitor effectiveness 

of restoration efforts (NOAA-Fisheries 2012).

Many of the entities involved in aquatic habitat restoration are also concerned 

with maintenance of a high-quality water supply for domestic, agricultural, 

industrial, recreational, and ecosystem uses. Within this context, the U.S. Forest 

Service, Pacific Northwest Research Station, in partnership with ISEMP, is testing 

an approach to status and trend monitoring of relevant water quality parameters 

(pH, water temperature, dissolved oxygen, and specific conductivity) in the Entiat 

River watershed. The Entiat is a Columbia River tributary in central Washington 

state (fig. 1). A particularly active program of habitat restoration is underway in the 

Entiat, where salmonid populations have been severely depleted (CCCD 2004). The 

watershed currently provides critical habitat for three salmonid populations listed 

under the 1973 federal Endangered Species Act (ESA), including spring Chinook 

salmon (Oncorhynchus tshawytscha) (endangered), summer steelhead (O. mykiss) 

(endangered), and bull trout (Salvelinus confluentus) (threatened) (CCCD 2004; 

UCSRB 2007, 2012).

As part of a coordinated federal and state effort to monitor compliance with 

the federal Clean Water Act of 1977, point measurements of water quality are 

taken monthly by the Washington State Department of Ecology (WDOE) near the 

Entiat gage, 2.5 river kilometers (RK) upstream from the river mouth (RK 2.5, fig. 

1) (WDOE 2012). In the 2008 WDOE, Water Quality Assessment 305(b) Report 

and 303(d) List, occasional excursions of the state water quality standard for pH 

are documented for the period 2004 through 2006. As a result of these excursions, 

the lower Entiat River in the vicinity of the Entiat gage is listed as a “category 5” 

(impaired) water body for pH (WDOE 2008).

In addition to pH, the Entiat River, in the vicinity of the Entiat gage, is also 

listed in the 2008 WDOE Water Quality Assessment as a “category 4B” impaired 

water body for water temperature. A category 4B listing recognizes a water quality 
3

Water Quality Trends in the Entiat River Watershed: 2007–2010

Figure 1—The Entiat River watershed. RK = river kilometer.
4

RESEARCH NOTE PNW-RN-569

impairment that is being addressed by a pollution control program (WDOE 2008). 

During most summers, WDOE measures water temperature continuously at this 

station (WDOE 2012). A program of distributed water temperature monitoring 

is also being conducted in the Entiat and Mad Rivers by the U.S. Forest Service, 

Entiat Ranger District. Details of the history of water quality measurement in 

the Entiat watershed are presented in the Entiat Water Resource Inventory Area 

(WRIA) 46 Management Plan (CCCD 2004).

The focus on salmonid restoration and concern over Clean Water Act listings 

make water quality a matter of particular interest to the Entiat Watershed Planning 

Unit (EWPU), tribes, agencies, and other interested parties (CCCD 2004; NOAAFisheries 2012; WDOE 2008, 2012). The study reported herein is largely a response 

to discussions among EWPU members in 2005 and 2006 regarding the need for 

additional information on river pH in the watershed. Primary objectives include 

defining the spatial and temporal extent of high pH conditions and identifying 

sections of river that may contribute high pH water. The scope is broad scale and 

exploratory in nature, although findings may lead to more focused and detailed 

investigations. Results for the years 2007 through 2008 were reported in Bookter et 

al. (2009). The present report includes results for the years 2007 through 2010.

Measured Water Quality Parameters

pH—

The effective concentration of dissolved hydrogen ions [H+] is expressed as the 

logarithmic unit “pH,” where pH = -log [H+]. The pH scale ranges from 0 (most 

acidic) to 14 (most basic). Acidic solutions have a pH less than 7.0, and basic solutions have a pH greater than 7.0. Most chemical and biochemical processes are 

affected by pH, and excessively high or low values can be directly detrimental to 

biota. Magnitude of pH affects the solubility and biological availability of nutrients, 

such as nitrogen, phosphorus, and other components of a river’s dissolved load. A 

pH between 6 and 9 is generally considered an ecologically acceptable range for 

freshwater aquatic organisms (Hem 1985, Welch et al. 1998). The WDOE specifies 

a pH in the range 6.5 to 8.5 as its acceptable criterion for aquatic life in fresh water, 

with additional limits on human-caused variation (WDOE 2008).

Water temperature—

Water temperature is an important component of aquatic habitat. It affects chemical and biological processes, productivity, behavior, life history, and interspecies 

interactions. Temperature affects water chemistry by altering the rate of chemical 

reactions and affecting equilibria such as dissolved oxygen concentration (Allan 
5

Water Quality Trends in the Entiat River Watershed: 2007–2010

1995, Welch et al. 1998). The WDOE employs the 7-day average of the daily maximum temperatures as its aquatic life water temperature parameter. The average 

maximum temperature criterion at the Entiat gage is 17.5 °C (WDOE 2008).

Dissolved oxygen—

Dissolved oxygen (DO) is supplied to stream water by photosynthesis during 

daylight hours and is taken into solution from the atmosphere. It is consumed 

by respiration by aquatic organisms and by organic matter decomposition and 

other chemical processes. Dissolved oxygen concentration can also be reduced by 

influxes of deoxygenated ground water (Allan 1995, Welch et al. 1998). Warmer 

water temperatures reduce oxygen solubility and cause increased metabolic activity 

(growth, productivity, and respiration) and decomposition. This and the diurnal 

nature of photosynthesis interact to produce diurnal variation in DO concentration, 

which decreases at night, potentially to levels that are detrimental to certain fish 

species (Allan 1995, Welch et al. 1998, Williamson et al. 1997).

The U.S. Environmental Protection Agency (USEPA 1986) finds that, for the 

purpose of recommending criteria for salmonid waters, average DO concentrations greater than 11 mg/L are associated with no production impairment, average concentrations between 9 and 11 mg/L are associated with slight production 

impairment, and average concentrations between 7 and 8 mg/L are associated with 

severe production impairment. Hicks (2002) reviews the literature relevant to DO 

criteria for surface water. Brown and Hallock (2009) further discuss WDOE criteria 

development for DO. WDOE sets the minimum DO criterion for aquatic life in the 

Entiat watershed at 9.5 mg/L (Hallock 2011).

Specific conductivity—

Conductivity, a measure of the ability of a material to carry an electrical current, is 

the inverse of resistance, and is therefore commonly measured in units of 1/ohms 

called mhos or Siemens (S). Conductivity is a function of temperature. Specific 

conductivity (SC) is the conductivity of a solution standardized to 25 oC. Stream 

water conductivity increases with higher concentrations of dissolved minerals and 

salts, implying increased contact with reactive bedrock or other surface or subsurface materials. It is a useful indicator of change in dissolved constituents, including 

soluble reactive phosphorus and nitrate nitrogen, which are important nutrients in 

aquatic ecosystems. Specific conductivities less than thousands of microSiemens 

per centimeter (μS/cm) are generally not considered harmful to aquatic biota. 

Specific conductivities less than 100 μS/cm are common in precipitation, and values 

found in potable water may be as high as 1,500 μS/cm (Hem 1985, McCutcheon 

et al. 1993, Welch et al. 1998). The WDOE does not have aquatic life criteria for 

conductivity (WDOE 2008).
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RESEARCH NOTE PNW-RN-569

Methods

Study Area

The Entiat River is located on the eastern slope of the central Cascade Mountains in 

the state of Washington, 55 km (34 mi) northwest of Wenatchee. It is 85 km (53 mi) 

long, and its drainage area is approximately 1100 km2

 (425 mi2) (fig. 1). Wildfire, 

flooding, mass soil and debris movement, and land use were the primary historical 

disturbance processes. Land use included grazing, agriculture, timber harvesting, 

transport of logs within the river channel, dams for log storage ponds and hydropower generation, roading, flood plain and river channel modification projects and 

structures, residential development, and recreation (CCCD 2004).

Site Selection

Water quality measurement sites were located within the existing network of river 

gages. Specific sites were selected to maximize spatial distribution along the Entiat 

River and include the Mad River, the Entiat’s primary tributary. This distribution 

was consistent with the U.S. Geological Survey (USGS), National Water Quality 

Assessment Program approach of making intensive measurements at a few points 

that integrate critical drainage areas rather than randomly selecting measurement 

sites (USGS 2012). 

Instrumentation

In spring 2007, we deployed one In-Situ, Troll 95002 multiparameter, data-logging, 

water-quality instrument at each of four gaging stations (table 1, fig. 1). Instruments 

were secured in the channel inside protective 10-cm-diameter pipes. The lower 

60 cm of each pipe was perforated to ensure ample water circulation around the 

instrument sensors. Instruments were equipped with a separate sensor for each 

measured water-quality parameter and programmed to record data at 15-minute 

intervals. Instruments were removed during winter (typically December through 

February) to avoid damage from river ice and redeployed the following spring when 

ice conditions allowed. All sensors used an EPA-approved methodology (table 2). 

Dissolved oxygen sensors utilized an integrated barometer with vented cable, allowing the sensor to incorporate real-time barometric pressure into calibrations and 

calculations of percentage of DO saturation. Following 3 years of data collection, 

indicating that water quality was unlikely to be a concern at the North Fork gage, 

measurements there were discontinued as a cost-saving measure.

2 The use of trade or firm names in this publication is for reader information and does not 

imply endorsement by the U.S. Department of Agriculture of any product or service.
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Water Quality Trends in the Entiat River Watershed: 2007–2010

Quality Assurance/Quality Control (QA/QC)

Reference instrument procedures—

Following initial installation and reinstallation each spring, instrument function and 

calibration were checked at least weekly for 2 to 4 weeks. After this initial period, 

instruments were inspected and data downloaded at 2-week intervals. During each 

site visit, a fifth multiparameter instrument, calibrated immediately before use and 

checked immediately afterward, was employed as a portable, hand-held reference 

for checking data from field instruments. Prior to recording measurements, the reference instrument was allowed to equilibrate to the stream water environment for 

a period of 5 to 20 minutes depending upon observed measurement stability. Field 

and reference instrument measurements were then recorded and compared. Fielddeployed sensors were recalibrated if deviation from the reference sensor exceeded 

a predefined standard (table 3) or under the following conditions:

Table 1—Location of water quality instruments in the Entiat River watershed 

River Coordinates 

River gage (short name) Gaging agency Gage ID kilometer (lat., long.)a

Entiat River near Entiat USGSb 12452990 2.5 47° 39' 48", 

(“Entiat”) 120° 14' 58"

Mad River at Ardenvoir USGS 12452800 0.64 47° 44' 13", 

(“Mad”) 120° 22' 03"

Entiat River near Ardenvoir USGS 12452890 29 47° 49' 07", 

(“Ardenvoir”) 120° 25' 19"

Entiat River at North Fork WDOEc/CCDd 46A170 53 47° 59' 15", 

Campground (“North Fork”) 120° 34' 47"

a Shown in degrees, minutes, and seconds.

b U.S. Geological Survey.

c Washington State Department of Ecology.

d Cascadia Conservation District.

Table 2—Sensor methodology and manufacturer’s stated accuracy

Variable Methodology Accuracy

pH Standard methods 4500-H+, EPA 150.2 0.1 pH units

Temperature EPA 170.1 0.1 °C

Dissolved oxygen In-Situ Method 1002-8-2009, EPA, ATP 0.2 mg/L

Case No. N05-0014, 40 CFR, Part 136.3.

Specific conductivity Standard methods 2510, EPA 120.1 2 μS/cm
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RESEARCH NOTE PNW-RN-569

1. Repeated, but within threshold, deviation from the reference. Typically, this 

occurred with each sensor one or fewer times per year.

2. Disturbance to the instrument, e.g., excessive sedimentation, biofouling, or 

mechanical disturbance. Sediment accumulation, commonly accompanied 

by biofouling, occurred each high-flow season. Following cleaning, the 

need for recalibration was determined by performance relative to the reference sensor. Mechanical disturbance was rare.

3. Calibration performance outside the manufacturer’s standards. This commonly occurred one or fewer times per year with each sensor, and was 

corrected by thorough cleaning or reconditioning according to the manufacturer’s guidelines.

Calibration—

Instruments were designed for field calibration at ambient, onsite temperature, 

elevation, and barometric pressure, thereby minimizing interruption of data collection and improving accuracy compared to offsite calibration. All calibration and 

testing employed the manufacturer’s software and met or exceeded the manufacturer’s specifications and guidelines (In-Situ 2008) as follows:

pH—A two-point pH calibration was done using buffer solutions of pH 7 and 10, 

thereby spanning the range of pH measured in the Entiat and Mad Rivers. The reference instrument sensor was calibrated in the lab immediately before field checks, 

and a one-point, pH 7 check was done immediately after returning. If this reading 

deviated from the standard by more than 0.2 pH units (the allowable deviation), then 

the reference measurements for that day were not used. If the pH calibration parameters (slope, offset, and response) were outside the manufacturer’s recommended 

range, then the recommended sensor maintenance or replacement was performed 

(In-Situ 2008).

Temperature—Temperature sensors were not designed for user calibration. 

Therefore they were replaced if deviations from the reference sensor were not 

within established limits.

Table 3—Maximum acceptable 

deviations from reference sensors

Variable Threshold deviation

pH 0.2 pH units

Temperature 0.5 °C

Dissolved oxygen 1 mg/L

Conductivity 5 μS/cm
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Water Quality Trends in the Entiat River Watershed: 2007–2010

Dissolved oxygen—Two-point DO calibrations were done at 100 and 0 percent saturation. One-hundred percent saturation was obtained by bubbling air through deionized water. A solution of sodium sulfite provided 0 percent saturation. Following 

calibration, the reference sensor was checked in a 100 percent oxygen-saturated 

solution immediately before and after each cycle of reference checks. If measurements deviated from the standard by more than 10 percent, then the reference DO 

sensor was recalibrated. If the end-of-the-day measurement was outside this limit, 

then the reference DO readings for that day were not used. Dissolved oxygen sensors provided extremely stable results. Differences between field and reference sensors exceeding 1.0 mg/L (the allowable deviation) rarely occurred more than once 

during the 9-month season.

Specific conductivity—A one-point SC calibration was done using a 147-μS/cm 

standard. The reference sensor was calibrated in the lab immediately before and 

after each field session. Direct measurements of the standard solution were taken 

before and after each calibration. If these deviated by more than 5 μS/cm from the 

standard, then the sensor was recalibrated. If the end-of-the-day measurement was 

outside this limit, then the reference conductivity readings for that day were not 

used. If the calibration constant fell outside specifications, then the recommended 

sensor maintenance or replacement was performed and the instrument recalibrated 

(In-Situ 2008).

Data Processing

All data were examined for outliers or extreme variability relative to surrounding 

data. These cases could occur as a result of ice effects, biofouling, or other factors. Data determined to be unreliable were considered missing and not included 

in analyses. However, data corrected for ordinary instrument drift, as determined 

through reference tests and field calibrations, were considered valid, first-quality 

data, following Carroll et al. (2006). All data, regardless of designations or adjustments, were recorded in the database along with notes regarding reference checks, 

calibrations, unreliable data, or other relevant issues. Temporal trends and the 

timing and longevity of water quality extremes were investigated by examining 

time series of data measured at 15-minute intervals along with longer term means 

or medians (pH). Spatial trends were interpreted by comparing results across the 

array of instrumented sites.

Reconnaissance Surveys

Increased spatial resolution was desired to better quantify the rate of change in 

water quality parameters between stations. An abrupt change could suggest a local 
10

RESEARCH NOTE PNW-RN-569

source of water quality degradation. Therefore, water quality data from established 

sites were supplemented with reconnaissance-level point measurements between 

the Entiat and Ardenvoir gages. This included the section of river where pH and 

temperature measurements occasionally exceeded state water quality standards. 

In August 2007, we began taking point measurements at 2-week intervals with the 

hand-held reference instrument described previously. Locations with safe access at 

11.0, 17.0 (immediately upstream of the Mad River confluence), 22.5, and 27.0 RK 

were identified to achieve an approximately uniform distribution along the target 

section of river (fig. 1). For consistency, only uninterrupted surveys proceeding 

upstream were included in the analyses.

For each station in each survey, the parameter value, for example pH, at that 

station minus the parameter value at the next upstream station was taken as the 

change between stations. This change was divided by the distance between stations, 

giving a rate of change per kilometer of river. This value was assigned to the downstream station within each pair, and medians (pH) or means were calculated for the 

period of record. In general, pH, water temperature, and conductivity decreased 

in the upstream direction, making the change between stations positive. A similar 

point measurement survey was done once in the Mad River during September 2008 

(Bookter et al. 2010).

Temporal change in parameter values introduced uncertainty into calculations 

of spatial change. For example, temperature tended to increase from morning 

through mid to late afternoon, causing real-time spatial differences to be underestimated as measurements proceeded upstream. For parameters that increased in 

the upstream direction, real-time spatial differences were overestimated. Effects of 

these errors on calculated rates of spatial change were estimated for all parameters 

at the Entiat and Ardenvoir gages where diurnal variation was known. The 2009 

median diurnal change per unit time was applied to the median time and distance 

between measurements to arrive at an estimate of the error expressed in parameter 

units per kilometer.

Results

pH

For the years 2007 through 2010, median-daily pH remained below 8.5 at all sites. 

The highest daily medians occurred at either the Entiat or the Mad gage (fig. 2). 

The lowest pH values occurred during periods of high river discharge, principally 

during the spring snowmelt period (May through June). Maximum values of pH 

tended to occur during low discharge periods both before (March through April) 

and after (August through October) the spring peak flows (fig. 2, table 4a and 4b). 
11

Water Quality Trends in the Entiat River Watershed: 2007–2010

At the Entiat and Mad gages, pH metrics were nearly always markedly higher than 

farther upstream at the Ardenvoir and North Fork gages. This was particularly true 

during periods of high pH. Variation between the two upstream gages was relatively 

small despite their 24-km separation (figs. 2, 3a through 3d, table 4a and 4b). Each 

year the highest maximum-daily pH occurred at the Entiat gage, where values 

commonly exceeded 8.5 during higher pH periods and reached 9.5 in rare cases. 

Daily-maxima remained below 8.8 at the Mad gage and below 7.9 at the Ardenvoir 

and North Fork gages. Daily-minima less than 7.0 were rare at all locations, reaching as low as 6.5 at the Ardenvoir gage (fig. 3a through 3d).

Each day, pH magnitude in the Entiat and Mad Rivers varied from a minimum 

in the early morning to a maximum in the early to mid-afternoon. Magnitude of 

diurnal change varied with location and season, and generally decreased in the 

upstream direction, following the same seasonal trends as pH magnitude (figs. 

3a through 3d). Diurnal variation as large as 1.6 pH units occurred at the Entiat 

gage. Similar, although less extreme, variation occurred at the Mad gage. At both 

locations, daily maxima depart much farther from medians than do daily minima, 

indicating that maxima provide a poor characterization of central tendency 

(fig. 3a and 3b).

Figure 2—Median daily pH for all stations. Discharge data are from the Entiat gage.
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RESEARCH NOTE PNW-RN-569

Table 4a—2007–2008 monthly means (or pH medians) of water quality parameters

Entiat Mad Ardenvoir North Fork

Month pH Temp DO SC pH Temp DO SC pH Temp DO SC pH Temp DO SC

oC mg/L μS/cm oC mg/L μS/cm oC mg/L μS/cm oC mg/L μS/cm

May-07 7.42 7.77 12.34 52.32 7.27 4.38 11.63 32.86

Jun-07 7.47 10.06 11.59 41.19 7.57 9.19 10.98 50.34 7.31 8.54 10.90 30.57 5.77 11.27 31.57

Jul-07 7.58 15.46 10.29 52.81 15.39 9.50 87.16 7.23 12.75 10.12 36.13 7.41 9.14 10.31 33.08

Aug-07 7.82 16.89 9.89 90.28 8.05 14.62 9.64 111.3 7.58 14.30 9.56 47.45 7.57 10.14 10.02 41.13Sep-07 7.87 14.12 9.93 113.1 8.09 11.58 10.32 122.8 7.54 12.00 10.02 55.06 7.66 7.97 10.20 46.88

Oct-07 7.84 8.01 11.51 110.5 8.04 6.16 11.60 122.1 7.32 6.50 11.18 53.82 7.42 3.77 11.55 47.30

Nov-07 7.80 3.48 12.72 108.4 7.95 2.36 12.60 128.6 7.34 2.45 12.29 53.80

Apr-08 8.16 7.75 11.79 115.5 8.00 5.15 12.17 133.4 7.36 5.80 11.38 53.42 7.40 2.53 11.95 46.02

May-08 7.56 8.42 11.23 56.43 7.42 6.94 11.67 64.76 6.93 6.51 11.41 37.43 7.04 3.93 11.62

Jun-08 7.50 9.67 11.18 38.99 7.51 8.49 11.25 46.77 7.12 7.92 11.10 32.79 7.12 5.72 11.46 32.11

Jul-08 7.72 15.29 9.76 52.01 7.76 14.20 9.77 76.54 7.34 12.60 9.86 38.00 7.23 9.02 10.58 34.40

Aug-08 7.80 17.30 9.05 81.74 8.03 14.79 9.65 106.0 7.47 14.61 9.25 47.30 7.48 10.22 10.18 40.52

Sep-08 7.86 13.84 9.94 111.4 8.14 11.04 10.53 118.3 7.43 11.82 9.68 54.98 7.41 8.00 10.70 46.80

Oct-08 7.58 8.15 11.15 110.9 8.02 6.17 11.73 121.7 7.33 6.59 10.97 54.90 7.44 4.06 11.61 47.22

Nov-08 7.48 4.15 12.28 76.68 7.77 3.14 12.58 92.08 7.33 3.16 12.00 45.60 7.40 1.96 11.99 41.17

DO = disolved oxygen.

SC = Specific conductivity.
13

Water Quality Trends in the Entiat River Watershed: 2007–2010

Table 4b—2009–2010 Monthly means (or pH medians) of water quality parameters

Entiat Mad Ardenvoir North Fork

Month pH Temp DO SC pH Temp DO SC pH Temp DO SC pH Temp DO SC

oC mg/L μS/cm oC mg/L μS/cm oC mg/L μS/cm oC mg/L μS/cm

Mar-09 7.99 4.66 12.67 114.28 8.12 2.32 13.02 132.00 7.41 3.39 11.90 55.70

Apr-09 7.98 8.01 11.69 87.99 8.08 5.54 12.11 107.44 7.42 6.03 11.35 48.96 7.34 2.68 11.85 39.78May-09 7.70 8.75 11.50 53.57 7.75 6.83 11.75 62.82 7.28 7.08 11.11 33.26 7.27 4.31 11.50 31.98

Jun-09 7.40 10.85 10.84 36.39 7.50 9.10 11.10 42.19 7.20 8.87 10.68 28.06 7.08 6.30 10.94 28.11

Jul-09 7.65 17.23 9.53 56.15 7.87 14.90 9.65 78.35 7.41 14.40 8.85 35.88 7.30 10.05 10.07 31.64

Aug-09 7.79 18.30 9.18 82.60 8.10 15.38 9.57 100.01 7.44 15.63 8.95 44.17 7.39 11.10 9.77 37.07

Sep-09 7.74 15.11 9.71 95.73 7.99 12.17 10.24 107.04 7.36 12.93 9.35 48.16 7.36 8.87 10.23 40.44

Oct-09 7.69 7.97 11.22 98.57 7.97 5.80 11.81 107.00 7.40 6.28 10.85 47.87 7.37 3.37 11.51 41.21

Nov-09 7.55 3.80 12.58 70.87 7.85 2.51 12.77 96.20 7.37 2.59 12.16 41.99

Mar-10 7.81 6.80 12.16 111.54 7.98 4.23 12.38 127.36 7.35 4.85 11.38 51.96Apr-10 7.88 8.16 11.42 91.08 7.97 5.67 11.95 107.45 7.34 5.84 10.51 46.10

May-10 7.48 8.29 11.45 50.59 7.68 6.49 11.76 61.13 7.17 6.33 10.68 34.68

Jun-10 7.31 9.10 11.19 35.59 7.32 7.93 11.43 38.38 7.00 7.18 11.10 27.19Jul-10 7.39 13.50 10.11 40.45 7.75 13.30 10.03 63.69 7.14 10.77 9.93 29.47

Aug-10 7.67 16.27 9.42 65.69 7.90 14.39 9.72 92.74 7.35 13.32 9.31 38.93

Sep-10 7.68 13.95 9.91 82.13 7.91 11.41 10.43 99.33 7.37 11.48 9.60 44.55

Oct-10 7.74 9.13 11.02 81.10 7.90 7.18 11.46 106.46 7.37 7.31 10.66 45.08

Nov-10 7.74 5.04 12.16 68.47 7.88 3.55 12.44 93.43 7.42 3.55 11.68 41.78

DO = disolved oxygen.

SC = Specific conductivity.
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RESEARCH NOTE PNW-RN-569

Figure 3a—Daily pH parameters and discharge at the Entiat gage.

Figure 3b—Daily pH parameters and discharge at the Mad gage.
15

Water Quality Trends in the Entiat River Watershed: 2007–2010

Figure 3c—Daily pH parameters and discharge at the Ardenvoir gage.

Figure 3d—Daily pH parameters and discharge at the North Fork gage.
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RESEARCH NOTE PNW-RN-569

Point measurements indicated that median rate of change in pH between the 

North Fork and Ardenvoir gages was negligible and only a small increase of 0.013 

pH units/km occurred between the Ardenvoir and RK 27 sites (fig. 4). However, 

between RK 27 and the hatchery site, rate of pH increase varied from 0.02 to 

greater than 0.06 pH units/km. Rate of change shifted abruptly between the Hatchery site and the Entiat gage from 0.031 to -0.015 pH units/km (fig. 4). Estimated 

error in these rates at the Entiat and Ardenvoir gages, owing to diurnal change, was 

0.004 and 0.002 pH units/km, respectively.

Water Temperature

At all stations, water temperature follows generally predictable seasonal trends, 

increasing steadily from near 0 °C at the beginning of each year’s measurement 

season in the early spring. This temperature increase is slowed by the annual 

snowmelt-driven high flows, then resumes in early to late June as flows recede. 

Temperatures begin to decrease in late August or early September, and return 

to near 0 oC by December (fig. 5). The highest mean-daily, maximum-daily, and 

Figure 4—Median rate of spatial change in pH. The magnitude displayed is the pH at each station minus 

that at the closest upstream station. Thus, positive values indicate increasing pH in the downstream 

direction. The negative value for the Entiat station indicates decreasing pH moving downstream from 

the Hatchery station.
17

Water Quality Trends in the Entiat River Watershed: 2007–2010

Figure 5—Mean daily water temperature for all stations. Discharge data are from the Entiat gage.

mean-monthly temperatures occur at the Entiat gage, commonly during early- to 

mid-August (figs. 6a through 6d, table 4a and 4b). At the Entiat gage, some maximum daily temperatures exceeded 21 oC in all years, while in 2008 and 2009, some 

mean-daily temperatures reached or exceeded 21 oC. Temperatures at the Mad gage 

were, in general, similar to those at the Ardenvoir gage, with mean-daily values not 

exceeding 19 oC. Temperatures at the North Fork gage were consistently the coldest. 

Daily maxima remained below 16 oC (fig. 5, 6a through 6d).

Water temperature increased, but at varying rates, along the Entiat River downstream from the North Fork gage. The highest estimated rates of increase occurred 

between the Ardenvoir gage and RK 22.5, reaching nearly 0.13 oC/km. (fig. 7). 

Downstream from RK 22.5, the rate of temperature increase decreases sharply 

before increasing again to a moderate rate between the hatchery site and the Entiat 

gage (fig. 7). Error in these rates owing to diurnal variation is estimated to be 0.019 

and 0.036 °C/km at the Entiat and Ardenvoir gages, respectively.
18

RESEARCH NOTE PNW-RN-569

Figure 6b—Daily water temperature parameters and discharge at the Mad gage.

Figure 6a—Daily Water temperature parameters and discharge at the Entiat gage.
19

Water Quality Trends in the Entiat River Watershed: 2007–2010

Figure 6c—Daily water temperature parameters and discharge at the Ardenvoir gage.

Figure 6d—Daily water temperature parameters and discharge at the North Fork gage.
20

RESEARCH NOTE PNW-RN-569

Dissolved Oxygen

Except on rare occurrences, mean-daily DO concentrations varied between 8 and 

14 mg/L at all measurement sites. This range spanned the WDOE minimum DO 

criterion for aquatic life in the Entiat watershed (9.5 mg/L) (Hallock 2011). Dissolved oxygen is inversely related to water temperature. Accordingly, the lowest 

DO concentrations occurred from July through September. Annual minima in 

DO commonly occurred from mid-July through mid-August. During this time, 

concentrations below 8 mg/L occurred rarely at the Entiat and Ardenvoir gages (fig. 

8). Maximum DO concentrations commonly occurred during times of lowest water 

temperature, immediately before and after the December through February period 

when instruments were removed from the river (figs. 9a through 9d). Mean daily 

DO concentrations, expressed as a percentage of saturation, remained high throughout the measurement period. Values less than 90 percent were unusual, occurring 

on only a few days at all sites except the Mad gage where concentrations remained 

above 95 percent.

Point sampling indicated that DO changed little from the North Fork gage 

downstream to the Ardenvoir gage, despite a marked increase in water temperature 

(figs. 7 and 10). Dissolved oxygen then decreased in the downstream direction to 

Figure 7—Mean rate of spatial change in water temperature. The magnitude displayed is the temperature at each station minus that at the closest upstream station. Thus, positive values indicate increasing 

temperature in the downstream direction. Rate varies among stations, nevertheless all differences are 

positive, indicating an uninterrupted increase in water temperature moving downstream from the North 

Fork gage.
21

Water Quality Trends in the Entiat River Watershed: 2007–2010

Figure 8—Mean daily dissolved oxygen for all stations. Discharge data are from the Entiat gage.

the RK 27 site before increasing sharply between RK 27 and RK 22.5. Dissolved 

oxygen continued to increase, although at lower rates, from RK 22.5 downstream 

to the hatchery site before decreasing between the hatchery site and the Entiat gage 

(fig. 10). Estimated error in the rate of change in DO owing to diurnal variation was 

0.008 and 0.012 mg/L/km at the Entiat and Ardenvoir gages, respectively.

Specific Conductivity

At all sites and across all years, mean daily SC remained below 160 μS/cm (fig. 11). 

These very low levels indicated concentrations of minerals and dissolved salts well 

below levels that might adversely affect aquatic biota (Hem 1985, McCutcheon et al. 

1993, Welch et al. 1998). Temporal trends in SC resembled those in pH in that the 

lowest values occurred during the peak of the snowmelt runoff period and highest 

values occurred during the spring and fall low-flow periods. 

Spatial trends in SC were also broadly similar to pH. Both parameters were 

notably larger at the Entiat and Mad gages than at the Ardenvoir and North Fork 

gages (figs. 2 and 11). Both SC and pH changed little in the downstream direction 

from the North Fork gage to the Ardenvoir gage. Downstream of the Ardenvoir 

gage, both increased rapidly. The largest rate of increase in SC occurred in the 

downstream direction from the Ardenvoir gage to RK 27.0. Specific conductivity 
22

RESEARCH NOTE PNW-RN-569

Figure 9b—Daily dissolved oxygen parameters and discharge at the Mad gage.

Figure 9a—Daily dissolved oxygen parameters and discharge at the Entiat gage.
23

Water Quality Trends in the Entiat River Watershed: 2007–2010

Figure 9c—Daily dissolved oxygen parameters and discharge at the Ardenvoir gage.

Figure 9d—Daily dissolved oxygen parameters and discharge at the North Fork gage.
24

RESEARCH NOTE PNW-RN-569

continued to increase at lower rates in the downstream direction to the hatchery site 

(fig. 12). The pattern of change in pH was similar, although the largest rate of pH 

increase occurred between RK 27.0 and RK 22.5 (fig. 4). The rate of change in both 

parameters switched from positive to negative in the downstream direction from the 

hatchery site to the Entiat gage (figs. 4 and 12). Error in the rate of spatial change in 

SC owing to diurnal variation was estimated to be 0.023 and 0.011 μS/cm/km at the 

Entiat and Ardenvoir gages, respectively.

Discussion

pH

Reconnaissance-level point sampling of water quality establishes that neither pH 

magnitude nor rate of change is spatially uniform along the Entiat River. Indeed, 

the rate of change can vary by a factor of five between adjacent river sections only 

a few kilometers in length. Furthermore, although these results cannot identify specific sources of high pH water, they can help to focus more intensive future surveys. 

For example, the reach between RK 27 and RK 22.5, where rate of pH increase is 

Figure 10—Mean rate of spatial change in dissolved oxygen (DO). The magnitude displayed is the DO 

concentration at each station minus that at the closest upstream station. Thus, positive values indicate 

increasing DO in the downstream direction. Negative values indicate two areas of decreasing DO moving downstream from the North Fork gage.
25

Water Quality Trends in the Entiat River Watershed: 2007–2010

Figure 11—Mean daily specific conductivity for all stations. Discharge data are from the Entiat gage.

the highest, warrants additional investigation (fig. 4). Similarly, the high rate of pH 

increase between the Mad River confluence and the hatchery suggests the importance of the Mad River as a source of high-pH water (figs. 2 and 4) for the Entiat. 

Point measurements in September 2008 indicate a clear downstream increase in pH 

along the Mad River from the headwaters to the mouth (Bookter et al. 2009). The 

decrease in pH from the hatchery site to the Entiat gage suggests input of relatively 

low pH water from tributaries or ground water.

Factors that affect river pH include the watershed’s soil and bedrock chemistry, 

water contact time with soil and bedrock, land use effects, exposure of river water 

to sunlight, and aquatic biological processes (Hem 1985, Welch et al. 1998). In the 

Entiat River, periods of high pH are correlated with either high exposure to solar 

radiation owing to low canopy cover (early spring) or high water temperatures (late 

summer and fall) (fig. 2). Both solar radiation and high water temperature are likely 

to increase periphyton (attached algae and other micro- and macro-organisms), photosynthesis, and productivity, which can increase pH in rivers (Welch et al. 1998, 

CCCD 2004). During daylight hours, periphyton photosynthesis removes carbon 
26

RESEARCH NOTE PNW-RN-569

dioxide from river water, leaving free hydroxyl ions (OH-) to combine with hydrogen, thereby reducing the concentration of free hydrogen ions (H+) and increasing 

pH. Daytime pH values greater than 9 are common in surface water, although pH 

commonly drops at night as photosynthesis declines (Welch et al. 1998). Analyses 

of periphyton biomass in the Entiat and Mad Rivers in 2008 support a positive correlation between pH and periphyton productivity (Bookter et al. 2009).

Land use effects that can stimulate periphyton productivity include increases in 

water temperature and enrichment in nutrients, such as nitrogen and phosphorus. 

Water temperature can be increased by removal of riparian shading, water withdrawals, or delivery of high-temperature water to the river. Common sources of 

nutrient enrichment include nonpoint agricultural sources, septic tank effluent, and 

livestock waste. Soluble forms of phosphorus and nitrogen are commonly delivered 

to streams by runoff or irrigation return flow and can reach shallow ground water 

through infiltration of precipitation or irrigation water. In addition, phosphorus can 

be readily delivered to surface water when bound to mobile soil particles (Fuhrer et 

al. 2004, Welch et al. 1998, Williamson et al. 1997).

Figure 12—Mean rate of spatial change in specific conductivity (SC). The magnitude displayed is the 

SC at each station minus that at the closest upstream station. Thus, positive values indicate increasing 

SC in the downstream direction. A negative value for the Entiat station indicates decreasing SC moving 

downstream from the Hatchery station.
27

Water Quality Trends in the Entiat River Watershed: 2007–2010

Methods of reducing nutrient enrichment and associated periphyton biomass 

include control of contaminant sources, maintenance of high-quality riparian habitat, and enhancement of nitrogen-fixing riparian vegetation. Invertebrate grazing 

is another important control on periphyton; therefore, maintenance of high-quality 

invertebrate habitat is important. Periphyton biomass can also be reduced by 

substrate disruption and scour during high flows, especially flows with high loads 

of entrained sediment (Fuhrer et al. 2004, Welch et al. 1998).

Although patterns of high pH in the Entiat and Mad Rivers are consistent with 

photosynthetic forcing, nutrient enrichment has not been identified as a concern in 

the WDOE monthly sampling program (WDOE 2008). Measured levels of ammonia-nitrogen, nitrate-nitrogen, total nitrogen, orthophosphate, and total phosphorus 

are, in general, similar to what would be expected in streams draining relatively 

undisturbed watersheds (McCutcheon et al. 1993). Ratios of total persulfate nitrogen to total phosphorus in this same data set range from 6.9 to 68.4 (WDOE 2008).

Even where nutrient concentrations are relatively low, periphyton biomass can 

respond strongly to enrichment, depending on water temperature and velocity, 

solar radiation, invertebrate grazing, and other factors. Concentrations of total 

phosphorus as low as 0.005 mg/L can cause excessive algal growth (McCutcheon 

et al. 1993, Murphy 1998, Welch et al. 1998). At the Entiat gage, total phosphorus 

concentrations that exceed the usual range of data, measured by WDOE since 

October 1996, include 15 values ranging from 0.017 to 0.054 mg/L (WDOE 2008). 

Additional, detailed investigations will be required to fully assess the distribution of 

nutrients and their effects on periphyton productivity and biomass, including analyses of chlorophyll-a dry mass to determine functional algal biomass (McCutcheon 

et al. 1993, Steinman and Lamberti 1996).

Watershed geology can have an important influence on river pH. In the Entiat 

valley, an accumulation of till, glacial outwash, and other alluvium creates a valleybottom aquifer (Dixon 2003), and accumulations of till are also present in the Mad 

River valley (Dragovich et al. 2002, Faux and Archibald 2002, Tabor et al. 1987). 

These bodies of till create a setting for shallow ground water to interact chemically 

with the large mineral surface area present in fragmented till and outwash. Newton 

et al. (1987) reported that ground water pH increased substantially after exposure to 

a similar geologic setting in the Adirondack Mountains.

In the Entiat watershed, other opportunities for enhanced chemical interactions 

with ground water are provided by prominent bedrock fractures in the dominant 

intrusive igneous and high-grade metamorphic rocks (Dragovich et al. 2002, Tabor 

et al. 1987). These fractures can act as ground water storage zones and pathways. 

In the Mad River watershed, much of the river closely follows the contact between 

the Entiat pluton and the high-grade metamorphic rocks of the Mad River terrane 
28

RESEARCH NOTE PNW-RN-569

(Dragovich et al. 2002, Tabor et al. 1987). If bedrock has been altered by contact 

metamorphism or fracturing along this zone, then chemical interaction between bedrock and ground water may be enhanced. Consistent relationships between mapped 

geology and water chemistry are not apparent at the present spatial scales of data 

collection, and will remain hypothetical pending additional, detailed investigations.

Water Temperature

River and valley geomorphology may be affecting Entiat River temperatures. The 

highest estimated rates of water temperature increase are measured at the Ardenvoir, RK 27.0, and RK 22.5 sites. These sites are located within, or a short distance 

downstream of, the low-gradient “stillwater” section of the river. The broad flood 

plain of the stillwater section permits relatively high exposure of the river to solar 

radiation, and low flow velocity extends the duration of this exposure. 

Although a portion of the lower Entiat River is listed as impaired owing to high 

water temperatures, the “category 4B” listing allows the EWPU and cooperating 

agencies and groups to address the impairment through a pollution control program 

(CCCD 2004, WDOE 2008). An active restoration strategy is being pursued in the 

Entiat, including measures that directly address the water temperature issue, such 

as riparian vegetation enhancement and reductions in both water withdrawal and 

return of heated agricultural water (CCCD 2004).

Dissolved Oxygen

Dissolved oxygen concentration varies inversely with water temperature, and is 

reduced by biologic oxygen demand, including respiration and oxygen-consuming 

decay processes. Dissolved oxygen increases through photosynthetic input and 

aeration at riffles and rapids, and is typically near saturation in forested rivers 

(Welch et al. 1998). 

Point measurements suggest that DO is more variable in rate and direction 

of spatial change than the other measured water quality parameters. Although 

temperature increases markedly downstream from the North Fork to the Ardenvoir 

sites, the associated change in DO is less than measurement error (fig. 10). In this 

case, temperature effects may be countered by increased photosynthetic input of 

DO in the wide-valley, low-velocity stillwater section discussed previously. The 

decrease in DO from the Ardenvoir to the RK 27.0 site probably results from the 

associated high rate of temperature increase within the stillwater section (fig. 7). 

The sharp increase in DO from RK 27.0 to RK 22.5, despite continuing temperature 

increase, is likely caused by increased aeration, owing to steeper gradient below 

the stillwater section. Especially vigorous turbulent aeration occurs at RK 22.5. 

Dissolved oxygen continues to increase downstream through this steeper section 
29

Water Quality Trends in the Entiat River Watershed: 2007–2010

of river to the Hatchery site. However, increasing water temperature contributes 

to declining rates of DO increase. A sharp increase in temperature may drive the 

marked decrease in DO between the Hatchery to the Entiat gage (fig. 10).

A few unusually low DO measurements occur at the Ardenvoir gage in 2010. 

Each of these is a sequence of several consecutive measurements, rather than a single 

outlier; therefore, they are retained in the record. These likely reflect short-term 

biofouling of the sensor, owing to mobilization of large amounts of organic detritus 

by multiple runoff peaks during that year’s protracted snowmelt runoff (fig. 8).

Specific Conductivity

Although conductivity in the Entiat is far too low to be a water quality concern, 

temporal and spatial variation can indicate changes in water sources or dissolved 

constituents. Increases in SC downstream of the Ardenvoir gage (fig. 12) suggest 

the addition of conductive solutes, possibly nutrients, which can affect biological 

processes. Previously noted similar spatial patterns in pH suggest a related response 

to an increase in solutes. Relative high conductivity and pH in the Mad River suggest that the Mad may be an important source of such constituents.

Conclusions

This report summarizes results from the first 4 years of a study testing a more 

intensive approach to watershed-scale, status and trend monitoring of water quality 

than previously employed in the Entiat River. This approach has clear advantages 

over the commonly applied federal Clean Water Act compliance monitoring, which 

is generally conducted at much lower spatial and temporal resolution. To date, 

results of Clean Water Act monitoring include listings for water temperature and 

pH. More intensive monitoring including spatially distributed measurements at 

points that integrate critical drainage areas within the watershed allow inferences 

to be made regarding the source and distribution of extreme values in water quality 

metrics. Measuring variation in water quality parameters at frequencies of 1 hour 

or less allows temporal trends and cycles to be identified that clarify the duration 

and severity of extreme values. This measurement intensity can be a great aid in 

identifying potential causes and mechanisms of water quality extremes and their 

relationship to other factors such as river discharge, temperature, solar exposure, 

or seasonality. This study further demonstrates that water quality monitoring at 

this intensity is logistically and economically feasible as part of the broader salmon 

recovery monitoring program. Although the scope is broad scale and exploratory in 

nature, findings will aid investigators in designing more focused and detailed studies as needed. The value of these data sets will increase and inferences will become 

more robust as the length of record increases.
30

RESEARCH NOTE PNW-RN-569

Acknowledgments

This study was jointly funded by (1) The Bonneville Power Administration, Division of Environment, Fish, and Wildlife, Project number 2003-017-00, through the 

NOAA–Fisheries, Integrated Status and Effectiveness Monitoring Program, and (2) 

the USDA, Forest Service, Pacific Northwest Research Station. The manuscript was 

improved by thoughtful reviews from Peter Bisson and Karl Polivka.

English Equivalents

When you know: Multiply by: To find:

Meters (m) 3.2808 Feet

Kilometers (km) 0.6214 Miles

Hectares (ha) 2.4711 Acres

Square kilometers (km2

) 0.3861 Square miles

Grams (g) 0.3527 Ounces

Kilograms (kg) 2.2046 Pounds

Milligrams per liter (mg/L) 0.0010 Ounces per cubic foot

Liters per second (L/s) 0.0353 Cubic feet per second (cfs)

Cubic meters per second (m3/s) 35.3147 Cubic feet per second

Siemens or mhos 1.0000 1/ohm

MicroSiemens per centimeter (ms/cm) 2.5400 Micromhos per inch

Degrees Celsius (1.8 oC) + 32 Degrees Fahrenheit
31

Water Quality Trends in the Entiat River Watershed: 2007–2010

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