Attenuation of Runoff and Chemical Loads in 

Grass Filter Strips at Two Cattle Feedlots, 

Minnesota, 1995-98

By S.C. Komor and D.S. Hansen

Water-Resources Investigations Report 03-4036

Prepared in cooperation with the Minnesota Pollution Control Agency
U.S. DEPARTMENT OF THE INTERIOR

Gale A. Norton, Secretary

U.S. GEOLOGICAL SURVEY

Charles G. Groat, Director

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.

Mound View, Minnesota, 2003

For additional information write to:

U.S. Geological Survey

District Chief

2280 Woodale Drive

Mounds View, MN 55112

Copies of this report can be purchased from:

U.S. Geological Survey

Branch of Information Services

Box 25286, MS 517

Federal Center

Denver, CO 80225

Information regarding the USGS is available on the Internet via the World Wide Web. 

You may connect to the USGS Home Page using the Universal Resource Locator (URL) at 

http://wwwrvares.er.usgs.gov. 

You may also connect to the Minnesota District Home Page at 

http://mn.water.usgs.gov/.

For more information on all USGS reports and 

products (including maps, images, and computerized data), call 1-888-ASK-USGS

Water-Resources Investigations Report 03-4036
iii

CONTENTS

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

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

Purpose and scope.............................................................................................................................................................................1

Previous studies ................................................................................................................................................................................2

Description of study area ..................................................................................................................................................................2

Bock site....................................................................................................................................................................................2

Sanborn site...............................................................................................................................................................................3

Methods .................................................................................................................................................................................................... 3

Quality of water........................................................................................................................................................................................ 5

Bock site............................................................................................................................................................................................7

Sanborn site.....................................................................................................................................................................................10

Attenuation of runoff and chemical loads .............................................................................................................................................. 10

Summary................................................................................................................................................................................................. 14

References .............................................................................................................................................................................................. 14

ILLUSTRATIONS

Figure 1. Schematic showing plan view filter strips at Bock and Sanborn, Minnesota sites................................................................... 3

Figures 2–3. Photograph showing:

 2. Feedlot runoff in the settling basin at the upslope end of the Sanborn filter strip............................................................ 4

3. The Sanborn site looking north from near the filter-strip runoff flume ........................................................................... 4

Figures 4–5. Graphs showing:

4. Volumes of feedlot runoff, feedlot runoff plus rain on the filter strip, filter-strip runoff, and attenuation value

in the filter strip .................................................................................................................................................................. 10

5. Attenuation values for chemical constituents in four runoff events................................................................................ 13

TABLES

1. Hydrology at the Bock site.................................................................................................................................................................. 5

2. Constituent concentrations, loads, and attenuation values at the Bock site ........................................................................................ 6

3. Hydrology at the Sanborn site ............................................................................................................................................................. 7

4. Constituent concentrations, loads, and attenuation values at the Sanborn site ................................................................................... 8

5. Ground-water chemistry at the Bock and Sanborn sites ................................................................................................................... 11

CONVERSION FACTORS AND ABBREVIATIONS

Multiply metric unit By To obtain

Centimeter (cm) 0.3937 inch (in.)

Meter (m) 3.281 foot (ft)

Hectares (h) 2.471 acres 

Centimeter per second (cm/s) 0.03281 feet per second (ft/s)

Liter (L) 0.2642 gallon (gal)

Kilogram (kg) 2.205 pound (lb)

Degree Celsius (°C) (1.8 x temp °C) + 32 Degree Fahrenheit (°F)

Concentrations of substances are given milligrams per liter (mg/L), micrograms per liter (μg/L). A milligram is one thousandth of a 

gram, a microgram is one millionth of a gram. Electrical conductivity is measured as specific electrical conductance in units of 

microsiemens per centimeter (μS/cm) at 25 degrees Celsius.
iv
1

Attenuation of Runoff and Chemical Loads in 

Grass Filter Strips at Two Cattle Feedlots, 

Minnesota,1995-1998

by S.C. Komor and D.S. Hansen

ABSTRACT

Attenuation of cattle feedlot runoff in two grass-covered filter strips in Minnesota was estimated by measuring chemical 

loads into and out of the strips. Filter strips of the Bock and Sanborn sites were 60-m long and 20-m wide and received runoff from cattle feedlots that supported 35 and 225 cattle, respectively. Feedlot and filter-strip runoff were measured using 

flumes with stage sensors. Water samples were collected using automated samplers. Attenuation values were calculated 

from four storm-runoff events. Ground water sampled beneath and outside the filter strips indicated some infiltration losses 

of sulfate, chloride, and nitrogen at the Bock site where soil permeability was greater than at the Sanborn site. Chemical 

constituents in filter-strip runoff, and their corresponding ranges of attenuation were as follows: chemical oxygen demand, 

30–81 percent; dissolved chloride, 6–79 percent; dissolved sulfate, -3–82 percent; dissolved ammonia nitrogen, 33–80 percent; suspended ammonia plus organic nitrogen, 29–85 percent; dissolved organic nitrogen, 14–75 percent; suspended 

phosphorus, 24–82 percent; dissolved phosphorus, 14–72 percent; and fecal coliform bacteria, 18–79 percent. The ranges 

seem to be affected by barriers of direct contact of the runoff water with the soil. This varies seasonally by coverage of the 

soil by ice in winter and vegetation in summer months. Greater attenuation values occurred in October and May when mats 

of wilted, flat-lying grass covered the filter strips; attenuation values were less during the summer when tall growing grass 

covered the filter strips. 

INTRODUCTION

Runoff from animal feedlots commonly contains elevated concentrations of chloride, nitrogen, 

phosphorous, sediment, and bacteria. 

The elevated constituent concentrations can affect surface- and groundwater quality. Vegetated-filter strips 

(filter strips) frequently are installed 

downslope from feedlots to attenuate 

feedlot runoff before discharging to 

ground water and into receiving 

streams (Hammer, 1992). Filter strips 

are sloped areas, commonly planted 

with grass, intended to receive, attenuate, and filter feedlot runoff. Soil 

berms or other structures along the 

sides confine runoff within the filter 

strips. Filter strips remove suspended 

contaminants by slowing velocities of 

particles, resulting in deposition, and 

reduce concentrations of dissolved 

constituents by adsorption, uptake, 

infiltration, decomposition and volatilization (Clausen and Meals, 1989; 

Dickey and Vanderholm, 1981; 

Edwards and others, 1983; Schwer 

and Clausen, 1989). The U.S. Geological Survey (USGS), in cooperation 

with the Minnesota Pollution Control 

Agency (MPCA), investigated the 

effectiveness of filter strips to reduce 

concentrations and loads of feedlot 

runoff and to determine the effect of 

filter strips on ground-water quality.

PURPOSE AND SCOPE

 The purpose of this report is to 

describe the results of a study during 

1995-98 to determine the attenuation 

of cattle feedlot runoff and chemical 

loads in two grass covered filter strips 

at Bock and Sanborn, Minnesota. 

Data from 7 storm-runoff events and 

10 ground-water monitoring wells 

collected during 1995-98 were used. 

Data from four of the seven stormrunoff events were used to compute 

attenuation of runoff volumes and 

chemical loads. Data from six groundwater monitoring wells inside the filter strip were compared to data from 

seven wells outside the filter strips. 
2

PREVIOUS STUDIES

The effectiveness of filter strips 

can be evaluated using the percent 

reduction, on a weight basis, of constituents in outflow compared to 

inflow. Previous studies have found 

reductions of total suspended solids 

(TSS) of 33–98 percent, total organic 

nitrogen of 18–97 percent, total 

ammonia of 27–97 percent, total 

nitrogen of 43–92 percent, and total 

phosphorous of 12–97 percent (Young 

and others, 1980; Dickey and Vanderholm, 1981; Edwards and others, 

1983; Dillaha and others, 1988; Dillaha and others, 1989; Schwer and 

Clausen, 1989; Schellinger and 

Clausen, 1992; Chaubey and others, 

1994; and Srivastava and others, 

1996). 

Much of the reduction occurs in 

the first few meters of the filter strip 

(Robinson and others, 1996; Srivastava and others, 1996). Filter strips 

are less effective at removing dissolved constituents than removing 

suspended constituents. Some studies 

have found more dissolved nitrate and 

phosphorus in outflow than in inflow 

(Dillaha and others, 1988; Dillaha and 

others, 1989), probably resulting from 

the remobilization of nutrients in the 

filter strip. Reductions in fecal 

coliform bacterial colonies of 58–70 

percent have been reported (Young 

and others, 1980; Chaubey and others, 

1994). Other studies have found fecal 

coliform concentrations were not 

greatly reduced by filter strips 

(Dickey and Vanderholm, 1981; 

Srivastava and others, 1996).

Many of the controlling variables 

in filter-strip effectiveness have been 

documented. Filter strips become less 

effective at removing suspended solids and total nutrient mass when vegetation in the filter strips is short or on 

steep slopes, or where flow becomes 

channelized (Edwards and others, 

1983; Dillaha and others, 1988; Dillaha and others, 1989; Magette and 

others, 1989; Chaubey and others, 

1994; and Srivastava and others, 

1996). Filter strips also are less effective during snowmelt because water 

flows across the filter strips over frozen ground (Schwer and Clausen, 

1989; Schellinger and Clausen, 1992). 

Effectiveness declines when the filter 

strips become coated with dry solids 

from feedlot runoff, which reduce the 

capacity to accommodate additional 

solids, and when vegetation is killed 

or stunted by excessive water or nutrient concentrations because the filtering and adsorption quality is reduced. 

Other factors that may affect filter 

strip effectiveness includes the type 

and quantity of manure; the cleaning 

schedule of feedlots; the presence of 

settling basins for removing solids 

upgradient from the filter strip; the 

frequency, rate, and timing of rainfall; 

the vegetation height; antecedent 

moisture conditions; and soil type.

DESCRIPTION OF STUDY 

AREA

The two filter strips evaluated 

were located near the towns of Bock 

in central Minnesota and Sanborn in 

southwest Minnesota (fig.1). Average 

annual precipitation (1961-90) was 

about 73.4 cm near Bock and 64.5 cm 

near Sanborn (Midwest Regional Climate Center, Climate data and summaries, accessed February 6, 2003 at: 

URL http://mcc.sws.uiuc.edu/cgibin/greet.cgi/), and about 80 percent 

of the precipitation falls between 

April and September. Both filter strips 

were planted with grass. Feedlot runoff from each contributing catchment 

flowed into a settling basin to remove 

solids (fig. 1). Feedlot runoff entered 

the filter strip through the feedlot-runoff flume. Storm runoff often persisted after rainfall stopped due to 

ponding in the feedlots and plugging 

of the wooden filters that conveyed 

water to the filter strips. Runoff 

entered the upslope ends of the strips 

and was spread laterally by gravel 

strips that extended across the filter 

strips (fig. 1). Another gravel strip 

was located midslope in the filter 

strips. Water was contained within the 

filter strips by tapered soil berms. 

Water left the filter strip through the 

filter-strip runoff flume.

Bock Site

 The Bock filter strip was 79 m 

long by 24 m wide and had a downslope gradient of 1.2 percent. The ratio 

of filter strip area to feedlot area was 

0.20. The Bock site generally was 

mowed twice during the summer.

Soils in the Bock filter strip consisted of Adolph silt loam (mixed, 

frigid, Typic Epiaquoll) (U.S. Department of Agriculture, 1977). The top 

13 cm of soil is black or dark graybrown, silty clay, and clay with sand 

and roots. Soils from 13- to 32-cm 

depth are poorly drained black and 

gray silty clay and silt loam. On average, the water table was 1.3 m below 

land surface during the study, 

although during wet periods the water 

table was at land surface. Soil Engineering Testing of Bloomington, Minnesota conducted permeability tests 

on undisturbed soil cores. Saturated 

hydraulic conductivities were 7.6 x 

10-7 cm/s at the upslope end of the 

strip and 2.9 x 10-7 cm/s at the downslope end. 

The contributing catchment 

included the feedlot, feeding barns 

and cement manure-storage pad. The 

contributing catchment to the Bock 

filter strip was 0.97 h. Approximately 

30 percent of the catchment was 

paved. The feedlot was designed to 

accommodate 150–200 cattle, but 

only about 35 cattle occupied the 

feedlot during most of the study. 

Night time temperatures varied 

between –2.8 and 1.7°C from October 

17 to October 23, 1995, and the grass 

began wilting. During May 1996, 

shoots of new green grass were 

sprouting through a mat of the previous season’s brown, flat-lying grass. 
3

Sanborn Site

The Sanborn filter strip was 59 m 

long by 18.3 m wide and had a downslope gradient of 0.5 percent. The ratio 

of filter-strip area to feedlot area was 

0.20. The previous year’s vegetation 

was burned in the spring at the Sanborn site.

Soils in the Sanborn filter strip consisted of Normania loam (mixed, 

mesic, Aquic Haplustoll) (U.S. Department of Agriculture, 1985). The top 13 

cm of soil was black and dark grayishbrown, silty clay, and clay with sand 

and roots. Soils from the 13- to 40-cm 

depth were black and dark gray clay 

loam. Saturated hydraulic conductivities were 2.0 x 10-7 cm/s at the upslope 

and downslope ends of the filter strip. 

The water table averaged 0.81 m below 

land surface during the study. Under 

natural conditions, surface soils have 

organic-matter contents of 4–8 percent 

(United States Department of Agriculture, 1985). Organic contents in the filter strips were probably greater due to 

input of manure-laden water from the 

feedlots.

The contributing catchment at the 

Sanborn site was 0.55 h. About 48 percent of the catchment was paved and 

the feedlot typically contained 225 cattle. The manure-storage pad was about 

15 m from the inlet of the filter strip. 

The site was periodically cleaned.

Four storm-runoff events were 

monitored at the Sanborn site: July 27, 

1996; October 17, 1998; June 2, 1998; 

and June 27, 1998. During June 1996 

and 1998, and July 1996, there were 

thick growths of waist-high grass. 

Hard frosts (temperatures between -4 

and -5°C) on October 3, 4, 10, and 11, 

1996 caused the grass to wilt so that by 

the storm on October 17, it was brown 

and mostly lying flat. The design storm 

was 12.2 cm for the Sanborn site.

METHODS

Monitoring systems measured runoff volumes entering and exiting each 

filter strip and collected water samples 

Soil berm

Gravel strip

Gravel strip Flow direction

Autosampler

Fedlot-runoff

flume

Dike

Ground-water

monitoring wells

Autosampler

Filter-strip

runoff flume

fence

pipe with

slatted intake

Contributing catchment

(barns, feedlot, manure storage)

Grass filter strip

Datalogger

& modem

Outflow to pasture or

cultivated field

Sampling line

Sanborn site

Bock site

Minnesota

Minnesota R.

Mississippi River

0 5 10 METERS

0 10 20 30 FEET

settling basin

Berm surrounding

watershed

Plan view of filter strips at Bock and Sanborn, Minnesota sites.

Feeding barns

Cement manurestorage pad

Figure 1.

Three storm-runoff events were 

monitored at the Bock site: October 

23, 1995; May 5, 1996; and May 14, 

1996. The filter strips were designed 

to accommodate peak runoffs from 

25-year, 24-hour rainfalls, having 

water depths of 1.3 cm in the filter 

strips and minimum detention times 

of 15 minutes. The design storm was 

11.7 cm for the Bock site. 
4

The volume of rain on filter strips 

was calculated from the measured rain 

depths and the filter-strip areas. The 

volume retained in the filter strip was 

the volume of rain falling on the filter 

strips plus the volume of feedlot runoff 

entering the flume minus the volume 

exiting the filter strip. Attenuation 

value (Av), in percent, in the filter strip 

(percent of water retained) was determined by the following equation:

Feedlot runoff in the settling basin at the upslope end of Sanborn filter strip.

Photo by M.A. Menheer, U.S. Geological Survey.

Monitoring well

Feedlot-runoff

flume

Figure 2.

for chemical analyses. Feedlot runoff 

that entered each filter strip was measured with a Parshall flume (feedlotrunoff flume) attached to PVC pipe 

that conveyed water from the feedlot 

to the strip (fig. 2). Filter-strip runoff 

was routed by a dike into a second 

flume (filter-strip runoff flume). 

Water levels (stage) in the flumes 

were measured continuously with 

pressure transducers (Accubar 5600-

1025) and converted to discharges 

with stage-discharge rating curves 

verified with discharge measurements. Water samples were drawn 

through Teflon tubing from the base 

of the flumes into 1-liter plastic bottles by automatic samplers. Sampling 

lines were back flushed with runoff 

before each sample was collected. 

Samplers began collecting samples 

when the stage in the flumes rose 

above 2.3 cm. During most runoff 

events, samples were collected every 

10 minutes for the first hour and 

every half hour (or longer) thereafter. 

Samples were taken more frequently 

during the initial stages of a runoff 

event to better characterize the first 

flush of runoff. Some runoff events 

were sampled at a constant frequency 

(one sample every half hour) after the 

threshold depth was exceeded. 

Because auto samplers held only 24 

sample bottles, runoff events longer 

than about 10–12 hours were not 

sampled in their entirety. Chemical 

load calculations were not extended 

beyond the sample period. Incremental rainfall volumes were measured 

with tipping-bucket rain gages 

installed at the site. Sampling and 

measuring equipment was controlled 

by programmable data loggers (fig. 

1).

Rainfall was scarce at the Sanborn 

site during 1998. Consequently, a 

dam was installed at the feedlot outlet, just upgradient of the feedlot-runoff flume. When sufficient feedlot 

runoff from rainfall had accumulated 

upgradient of the dam, the water was 

released into the filter strip through the 

feedlot-runoff flume (fig. 3). These 

events, which occurred June 2 and 27, 

1998, are different tests of filter-strip 

performance than the natural runoff 

events monitored July 27 and October 

17, 1996. The runoff rate from the filter 

strip at the Sanborn site for June 27, 

1998 was not great enough to activate 

the autosamplers, so two grab samples 

were collected near the middle of the 

filter strip and the filter-strip flume.

The Sanborn site from near the filter-strip runoff flume.

Photo by M.A. Menheer, U.S. Geological Survey.

Looking north

Monitoring well

Filter-strip runoff

flume

Figure 3.
5

(1)

Water samples were removed from 

autosamplers within a few hours after 

collection and chilled to preserve their 

compositions. Samples were analyzed for chemical oxygen demand, 

sulfate, chloride, nitrite plus nitrate 

nitrogen, ammonia nitrogen, ammonia 

plus organic nitrogen, and phosphorus 

at the USGS National Water-Quality 

Laboratory (NWQL) in Lakewood, 

Colorado using protocols of Frishman 

and Friedman (1989). The Minnesota 

Department of Health (MDH) measured concentrations of fecal coliform 

bacteria in most samples within 24 

hours of sample collection using a 

membrane-filter technique (American Public Health Association, 1985).

Chemical loads (kg) in runoff were 

calculated by multiplying chemical 

concentrations (mg/L) by the volume 

of discharge accumulated since the 

previous sample had been collected. 

For example, a load occurring 

between 10:00 and 10:30 would be 

calculated by multiplying the chemical concentrations in the 10:30 sample 

by the volume of discharge occurring 

between 10:00 and 10:30. Loads for 

an entire storm were calculated by 

summing the incremental loads. Mean 

storm runoff concentrations (mg/L) 

were calculated by dividing the total 

loads by the total volumes of water 

measured in the feedlot-runoff flume. 

The resulting values represent the 

weighted constituent concentrations 

of each event. Attenuation values for 

chemical loads were calculated as follows:

(2)

Ground water was sampled 

throughout the study period to evaluate the effect of infiltration from the 

filter strips. Samples were collected 

from shallow water-table wells inside 

and outside the strips (fig.1). Most 

well screens were from 60- to 90- cm 

long to allow for variations in the 

water-table level. A peristaltic pump 

was used to pump ground water from 

the wells into flow-through chambers 

in which pH, specific conductance, 

temperature, and dissolved oxygen 

were monitored until stabilized then 

recorded. Samples were then filtered 

through 0.45-μm in-line cartridges 

and collected for analyses of sulfate, 

chloride, nitrate, nitrite, ammonia 

nitrogen, organic nitrogen; and phosphorous by the USGS NWQL in 

Lakewood, Colorado. The MDH analyzed unfiltered samples for fecalcoliform bacteria counts.

 QUALITY OF WATER

Hydrologic and chemical characteristics of runoff events at the Bock 

(tables 1 and 2) and Sanborn sites 

(tables 3 and 4) characterize runoff 

from the filter strips. The runoff duration from the feedlot value represents 

the time the stage remained above 2.3 

cm in the flumes. 

Ground-water quality is a concern 

where feedlot-runoff infiltration is 

significant. Chemical constituent concentrations in water from wells 

installed inside and outside the filter 

strips at the Bock and Sanborn sites 

are listed in table 5. Chemical changes 

in ground water from wells sampled 

inside the filter strips indicate that, for 

some parameters, filter-strip runoff 

degrades ground-water quality. 

Ground-water quality differences at

Av 100 = 1 volume of filter strip runoff

volume of feedlot runoff volume of rain + ------------------------------------------------------------------------------------------------------ ⎝ ⎠ ⎛ ⎞ • –

Av feedlot runoff load – filter strip runoff load

feedlot runoff load ------------------------------------------------------------------------------------------------------ ⎝ ⎠ ⎛ ⎞ = • 100

Table 1. Hydrology at the Bock site.

 [cm, centimeter; hr, hour; L, liter; L/s, liters per second; --, equipment malfunction]

Hydrology

Storm-runoff event

10/23/1995 5/5/1996 5/14/1996

Rain depth (cm) 1.5 1.4 2.3

Rainfall duration (hr) 10.3 6.9 13.9

Runoff duration from feedlot (hr) 18.0 7.6 9.9

Runoff duration at filter-strip exit (hr) -- 2.8 7.5

Maximum discharge from feedlot (L/s) 3.2 2.8 3.0

Maximum discharge at filter-strip exit (L/s) -- 1.2 1.9

Time between first discharges from feedlot and at filter-strip exit (hr) -- 0.2 1.8

Time between hydrograph peaks from feedlot and at filter-strip exit (hr) -- 0.1 1.1

Volume of rain in filter strip (L) 27,470 24,466 40,776

Volume of feedlot runoff (L) 142,333 52,627 58,166

Volume of feedlot runoff plus rain on filter strip (L) 169,803 77,093 98,942

Volume of filter-strip runoff (L) -- 16,812 52,882

Total water retained in filter strip (L) -- 60,281 46,060

Attenuation value (percent of water retained) -- 78 47
6

Table 2. Constituent concentrations, loads, and attenuation values at the Bock site

 [mg/L, milligrams per liter; N, nitrogen; --, equipment failure]

Chemical concentrations

Constituent Chemical oxygen demand 

(mg/L) Sulfate, dissolved (mg/L) Chloride, dissolved (mg/L) Nitrate + nitrite, dissolved (mg/L) Ammonia N, dissolved (mg/L)

Sample date 10/23/95 5/5/96 5/14/96 10/23/95 5/5/96 5/14/96 10/23/95 5/5/96 5/14/96 10/23/95 5/5/96 5/14/96 10/23/95 5/5/96 5/14/96Feedlot 

runoff 

Number of samples 11 6 11 11 6 11 11 6 11 11 6 11 11 6 11Maximum 920 5200 -- 100 47.0 23.0 190 280.0 270.0 30.0 0.7 0.2 7 100 120.0Minimum 10 4400 -- 83 4.8 5.0 150 250.0 190.0 17.0 0.2 0.1 0.97 61 89.0Average 500 4700 -- 94.4 23.9 11.6 170.9 265.0 235.5 27.3 0.4 0.2 3.5 84.8 105.8Standard deviation 380 294.4 -- 5.3 16.5 6.9 11.4 10.5 30.1 4.2 0.2 0.0 1.8 16.5 11.7

Filter-strip 

runoff

Number of samples 0 0 12 0 0 12 0 0 12 0 0 12 0 0 12Maximum -- -- -- -- -- 8.8 -- -- 220.0 -- -- 0.1 -- -- 65.0Minimum -- -- -- -- -- 1.9 -- -- 190.0 -- -- 0.1 -- -- 36.0Average -- -- -- -- -- 4.1 -- -- 207.5 -- -- 0.1 -- -- 45.3Standard deviation -- -- -- -- -- 6.9 -- -- 30.1 -- -- 0.0 -- -- 9.3

Constituent Ammonia +organic N, 

suspended (mg/L) Organic N, dissolved (mg/L) Phosphorous, dissolved (mg/L) Phosphorous, suspended (mg/L) Fecal coliform (colonies/100 mL)

Sample date 10/23/95 5/5/96 5/14/96 10/23/95 5/5/96 5/14/96 10/23/95 5/5/96 5/14/96 10/23/95 5/5/96 5/14/96 10/23/95 5/5/96 5/14/96Feedlot 

runoff

Number of samples 11 6 11 11 6 11 11 6 11 11 6 11 11 6 11Maximum 34.0 80.0 200.0 16.0 169.0 140.0 15.0 68.0 72.0 9 22.0 48.0 3.90E+06 2.40E+05 5.30E+05Minimum 3.6 40.0 0.0 4.2 117.0 70.0 6.9 61.0 45.0 1 10.0 13.0 2.27E+05 9.10E+04 8.60E+04Average 24.1 60.0 89.1 12.4 131.8 101.5 12.7 64.3 57.9 6.2 15.8 24.5 2.26E+06 1.67E+05 3.15E+05Standard deviation 8.9 14.1 52.4 3.4 19.5 23.3 2.4 3.0 9.5 2.9 4.8 12.7 1.18E+06 6.29E+04 1.21E+05

Filter-strip 

runoff

Number of samples 0 0 12 0 0 12 0 0 12 0 0 12 0 0 12Maximum -- -- 34.0 -- -- 110.0 -- -- 36.0 -- -- 11.0 -- -- 2.40E+05Minimum -- -- 0.0 -- -- 30.0 -- -- 17.0 -- -- 0.0 -- -- 5.80E+03Average -- -- 15.4 -- -- 50.3 -- -- 25.4 -- -- 5.0 -- -- 1.06E+05Standard deviation 10.1 20.5 6.3 3.0 1.21E+05

Chemical loads

Constituent Chemical oxygen demand Sulfate, dissolved Chloride, dissolved Nitrite plus nitrate, dissolved Ammonia N, dissolvedSample date 10/23/95 5/5/96 5/14/96 10/23/95 5/5/96 5/14/96 10/23/95 5/5/96 5/14/96 10/23/95 5/5/96 5/14/96 10/23/95 5/5/96 5/14/96Feedlot runoff (kg) 214.30 190.66 -- 31.90 1.32 0.78 59.16 10.91 15.32 8.13 0.19 0.01 1.63 3.98 6.14Filter-strip runoff (kg) -- -- -- -- -- 0.19 -- -- 10.35 -- -- 0.00 -- -- 2.40Attenuation value, in percent -- -- -- -- -- 75 -- -- 32 -- -- 84 -- -- 61Constituent Ammonia + organic N, 

suspended Organic N, dissolved Phosphorous, dissolved Phosphorous, suspended Fecal coliform (colonies/100 mL)

Sample date 10/23/95 5/5/96 5/14/96 10/23/95 5/5/96 5/14/96 10/23/95 5/5/96 5/14/96 10/23/95 5/5/96 5/14/96 10/23/95 5/5/96 5/14/96Feedlot runoff (kg) 9.89 2.30 5.13 4.45 5.53 5.60 4.58 2.61 1.86 2.61 0.58 1.41 3.753E+06 8.180E+10 1.206E+11Filter-strip runoff (kg) -- -- 0.75 -- -- 2.87 -- -- 1.40 -- -- 0.25 -- -- 4.60E+10 Attenuation value, in percent -- -- 85 -- -- 49 -- -- 25 -- -- 82 -- -- 62
7

both sites are not from specific storm 

events or runoff described in this 

report, but are the result of storm runoff and infiltration over time. 

BOCK SITE

Three storm-runoff events were 

monitored at the Bock site on October 

23, 1995; May 5, 1996; and May 14, 

1996. Due to equipment malfunctions, 

only flow volumes exiting the filter 

strip were measured during stormrunoff events on May 5, 1996, and 

May 14, 1996, and filter-strip runoff 

quality was evaluated for May 14, 

1996 (table 1). 

The storm-runoff event of October 23, 1995 generated the greatest 

volume of feedlot-runoff (142,333 L). 

Feedlot runoff from the storm of 

October 23, 1995, measured at the 

feedlot-runoff flume, contained the 

smallest loads of dissolved ammonia 

nitrogen, organic nitrogen, and fecal 

coliform bacteria compared to the 

other storm-runoff events (table 2). 

Sulfate, chloride, and nitrite plus 

nitrate loads were much larger in the 

October 23, 1995 storm than in other 

storms. 

The storms of May 5, 1996 and 

May 14, 1996 were approximately 

equivalent in terms of the feedlot-runoff volumes through the feedlot-runoff flume (52,627 and 58,166 L, 

respectively). However, the storms 

differed substantially in the volume of 

water that exited the filter strip and 

the percentages of water retained in 

the filter strip (78 percent and 47 percent, respectively) (table 1; fig. 4). 

The average depth to the water table 

beneath the filter strip decreased from 

0.6 m on April 19, 1996 to 0.2 m on 

May 16, 1996. The smaller percentage 

of retained water on May 14, 1996 

probably reflects the presence of shallower saturated soils compared to the 

event on May 5, 1996. Feedlot-runoff 

loads tended to be larger on May 14, 

1996 than on May 5, 1996, with the 

exceptions of dissolved nitrite plus 

nitrate, dissolved phosphorus, and sulfate.

 Ground water from wells sampled 

inside the filter strips at the Bock site 

had elevated specific conductance, 

dissolved sulfate, dissolved chloride, 

dissolved nitrate, dissolved ammonia 

nitrogen, and dissolved organic nitrogen concentrations beneath the filter 

strip when compared to ground water 

in wells outside the filter strip 

(table 5). The average chemical constituent concentrations in water from 

wells installed inside the filter strip 

was generally larger than the concentrations of chemical constituents in 

water from wells located outside the 

filter strip (table 5). Average dissolved sulfate, chloride, and nitrate 

were 62, 167, and 2.6 mg/L, respectively, inside the filter strip and 53, 

123, and 0.35 mg/L, respectively, outside the filter strip. The greater effect 

on ground water at the Bock site 

likely is due to the greater hydraulic 

conductivity of soil compared to the 

Sanborn site. 

Table 3. Hydrology at the Sanborn site

[cm, centimeter; hr, hour; cm/hr, centimeters per hour; L, liter; L/s, liters per second; --, equipment malfunction; †, release of dammed water]

Date sampled

7/27/96 10/17/96 6/2/98 6/27/98

Rain depth (cm) 9.1 3.6 0.5 0.6

Rainfall duration (hr) 52 6.5 45 82

Rainfall intensity (cm/hr) 0.54 0.47 † †

Runoff duration from feedlot (hr) 14.9 16.5 40 7.25

Runoff duration at filter-strip exit (hr) 27.1 11.2 -- 2.2

Maximum discharge from feedlot (L/s) 9.8 4.5 13.5 10.3

Maximum discharge from filter-strip-exit (L/s) 7.7 1.5 -- 1.34

Time between first discharges from feedlot and at filter-strip exit (hr) 2.0 5.3 41.0 40.2

Time between hydrograph peaks from feedlot and at filter-strip exit (hr) 10.8 3.7 -- 41.1

Volume of rain in filter strip (L) 117,048 46,305 6,534 8,232

Volume of feedlot runoff (L) 12,888 97,379 79,574 143,576

Volume of feedlot runoff plus rain on filter strip (L) 129,936 143,684 † †

Volume of filter-strip runoff (L) 19,273 24941 -- 3,160

Volume retained in filter strip (L) 110,662 118,743 -- 148,647

Attenuation value (percent of water retained) 85 83 -- 98
8

Table 4. Constituent concentrations, loads and attenuation values at the Sanborn site

 [mg/L, milligrams per liter; colonies/100 mL, colonies per 100 milliliter; --, equipment malfunction; N, nitrogen; E, multiplyed by 10 to the indicated power]

Chemical concentrations

Constituent Chemical oxygen demand (mg/L) Dissolved sulfate (mg/L) Dissolved chloride (mg/L)

Sample date 7/27/96 10/17/96 6/2/98 6/27/98 7/27/96 10/17/96 6/2/98 6/27/98 7/27/96 10/17/96 6/2/98 6/27/98

Feedlot runoff Number of samples 13 10 8 10 13 10 8 10 13 10 8 10

Maximum 3,300 4,900 21,000 2,320 68 280 174.5 83 120 700 857.5 244.7Minimum 560 150 16,000 1,385 33 110 137.3 58.4 49 210 792.5 137.3Average 1,058 3,470 17,788 1,764 45.8 160 164.2 72 69.8 374 836.9 165.4Standard deviation 831 1,798 1,723 282 9.3 55.8 12.8 9.2 17.7 168.1 21.5 34.7

Filter-strip runoff Number of samples 15 5 -- 2 15 5 -- 2 15 5 -- 2

Maximum 710 3,300 -- 1,640 63 140 -- 102.3 76 260 -- 231.1Minimum 470 2,900 -- 1,535 41 27 -- 80.8 58 200 -- 217.4Average 574 3,120 -- 1,588 49.8 109.4 -- 91.5 65.3 234 -- 224.3Standard deviation 66 148 -- 74 6.2 46.6 -- 15.2 5.1 23 -- 9.7

Constituent Dissolved nitrate + nitrite as N (mg/L) Dissolved ammonia N (mg/L) Suspended ammonia + organic N (mg/L)

Sample date 7/27/96 10/17/96 6/2/98 6/27/98 7/27/96 10/17/96 6/2/98 6/27/98 7/27/96 10/17/96 6/2/98 6/27/98

Feedlot runoff Number of samples 13 10 8 10 13 10 8 10 13 10 8 10

Maximum 0.2 0.3 0.1 0.6 25 65 0.7 31.7 71 185 709.8 113.5Minimum 0 0.1 0.1 0.1 4.2 25 0.6 17.3 6 2 0 74.8Average 0.1 0.1 0.1 0.3 6.8 35.9 0.6 25.6 23.1 103.7 264.9 95.3Standard deviation 0 0.1 0 0.2 5.7 12.3 0.0 5.5 16.6 50.2 275.2 13.4

Filter-strip runoff Number of samples 15.0 5.0 -- 2.0 15 5 -- 2 15 5 -- 2

Maximum 15.4 0.3 -- 0.1 62 41 -- 23.9 25 183 -- 122Minimum 0 0.1 -- 0.1 25 21 -- 8.7 0 60 -- 100.9Average 1.3 0.1 -- 0.1 37.1 25.6 -- 16.3 14.7 115.8 -- 111.4Standard deviation 4.1 0.1 -- 0 8.1 8.6 -- 10.7 6.2 45.5 -- 14.9

Chemical loads

Constituent Chemical oxygen demand Dissolved sulfate Dissolved chloride

Sample date 7/27/96 10/17/96 6/2/98 6/27/98 7/27/96 10/17/96 6/2/98 6/27/98 7/27/96 10/17/96 6/2/98 6/27/98

Feedlot runoff (kg) 254.96 394.34 677.54 251.97 14.48 12.69 6.29 10.4 21.86 25.94 31.95 25.45Filter-strip runoff (kg) 127.03 73.87 -- 176.3 11.02 2.27 -- 10.71 15.76 5.36 -- 23.9Attenuation value, 

in percent 50 81 -- 30 24 82 -- -3 28 79 -- 6

Dissolved nitrite + nitrate as N Dissolved ammonia N Suspended ammonia + organic N

7/27/96 10/17/96 6/2/98 6/27/98 7/27/96 10/17/96 6/2/98 6/27/98 7/27/96 10/17/96 6/2/98 6/27/98

Feedlot runoff (kg) 0.02 0.01 0 .03 1.72 2.9 0.02 3.72 6.5 10.25 9.35 15.99Filter-strip runoff (kg) 0.07 0 -- .02 1.15 0.59 -- 1.24 2.96 2.55 -- 11.38Attenuation value, in 

percent

-235 63 -- 42

33 80 -- 67 54 75 -- 29
9

Table 4. Constituent concentrations, loads and attenuation values at the Sanborn site--Continued

Chemical concentrations

Constituent Dissolved organic N (mg/L) Dissolved phosphorus (mg/L)

Sample date 7/27/96 10/17/96 6/2/98 6/27/98 7/27/96 10/17/96 6/2/98 6/27/98

Feedlot runoff Number of samples 13 10 8 10 13 10 8 10

Maximum 74 195 2745 56.5 21.0 36.0 251.2 35.1Minimum 8.8 51 890.4 31.9 3.6 19.0 154.2 22.1Average 20 97.4 1326.1 38.9 6.5 22.6 196.5 27.4Standard deviation 17 46.4 591.4 9.2 4.9 5.3 29.0 4.5

Filter-strip runoff Number of samples 15 5 -- 2 15.0 5.0 ---- 2

Maximum 21 99 -- 77.7 10.0 30.0 -- 40.9Minimum 10.6 53 -- 40.8 4.5 19.0 -- 18.4Average 16.3 64.6 -- 59.2 6.7 23.0 -- 29.7Standard deviation 3.1 19.3 -- 26 1.5 4.5 -- 16.0

Constituent Suspended phosphorus (mg/L) Fecal coliform (colonies/100ml)

Sample date 7/27/96 10/17/96 6/2/98 6/27/98 7/27/96 10/17/96 6/2/98 6/27/98

Feedlot runoff Number of samples 13 10 8 10 10 10 8 10

Maximum 17 54 151 32.1 3.70E+07 2.4E+8 2.6E+7 6.0E+6Minimum 0.9 4 23.7 19.3 5.80E+06 7.9E+7 1.0E+7 3.0E+5Average 5.4 27.6 95.6 25.6 1.10E+07 1.3E+8 2.1E+7 2.0E+6Standard deviation 4.1 13.4 51.5 4.4 8.60E+06 4.8E+7 5.2E+6 2.0E+6

Filter-strip runoff Number of samples 15 5 -- 2 15 5 -- 2

Maximum 6 42 -- 36.2 1.30E+07 2.8E+8 -- 4.0E+6Minimum 0 12 -- 29.3 7.50E+06 1.5E+8 -- 1.1E+6Average 2.2 30.4 -- 32.7 9.60E+06 1.9e+8 -- 2.6E+6Standard deviation 1.7 11.8 -- 4.8 1.3E+6 5.5E+7 -- 2.1E+6

Chemical loads

Constituent Dissolved organic N Suspended phosphorus

Sample date 7/27/96 10/17/96 6/2/98 6/27/98 7/26/96 10/17/96 6/2/98 6/27/98

Feedlot runoff (kg) 4.69 6.55 48.2 6.09 1.43 2.58 3.19 4.35Filter-strip runoff (kg) 4.04 1.64 -- 5.15 0.89 0.68 -- 3.32Attenuation value, in percent 14 75 -- 15 38 74 -- 24

Constituent Dissolved phosphorus Fecal coliform bacteria (colonies/100 mL)

Sample date 7/27/96 10/17/96 6/2/98 6/27/98 7/27/96 10/17/96 6/2/98 6/27/98

Feedlot runoff (kg) 1.60 2.03 7.82 4.07 2.8E+13 1.3E+14 8.2E+5 3.8E+5Filter-strip runoff (kg) 1.38 .56 -- 2.43 2.7E+13 2.7E+13 -- 1.8E+5Attenuation value, in percent 14 72 -- 40 18 79 -- 53
10

Constituent concentration, loads 

from feedlot and filter-strip runoff, 

and attenuation values for the Bock 

and Sanborn sites are listed in tables 

2 and 4, respectively. Periodically, 

some constituent concentrations were 

greater in the filter-strip than in feedlot runoff. For example, filter-strip 

runoff had greater concentrations for 

all constituents sampled than feedlot 

runoff except chemical oxygen 

demand. Filter-strip runoff could 

contain greater concentrations of certain constituents than the feedlot runoff because any given runoff event 

can entrain settled and adsorbed constituents left behind by preceding 

events. 

Dissolved chloride concentrations were the dominant inorganic 

constituent in feedlot runoff and 

undoubtedly comes primarily from 

the urine component of manure. Sulfate loads were large in certain samples, particularly at the Bock site on 

October 23, 1995 (table 2). Mammals 

excrete approximately 40 percent of 

ingested sulfate (A.N. Pell, Cornell 

University, written, commun., 2000). 

This excretory component is the 

likely source of sulfate in feedlot runoff. 

Decrease of chloride concentrations in filter-strip runoff compared 

to feedlot runoff may be due to two 

processes. First, chloride is an essential plant nutrient that has a role in 

photosynthesis, adenosine triphosphate production, and phosphorylation reactions (Kadlec and Knight, 

1996). Plant uptake is therefore a 

potential chloride sink. Second, 

increases of chloride concentration in 

ground water at both sites indicates 

that chloride infiltrated through the 

soil substrate into ground water. 

Although only the Bock site has 

greater chloride concentrations in 

ground water underlying the filter 

strips than ground water outside of 

the filter strip, it is possible that chloride at the Sanborn site did not infilSANBORN SITE

Four storm-runoff events were 

monitored at the Sanborn site: July 

27, 1996; October 17, 1996; June 2, 

1998; and June 27, 1998. Due to 

equipment malfunctions, flow volumes exiting the filter strip were not 

measured during the storm-runoff 

event on June 2, 1998. Percentages of 

water retained in the strip ranged from 

83 percent on October 17, 1996 to 98 

percent on June 27, 1998. The storm 

of July 27, 1996 generated the most 

rain (9.1 cm) and the greatest volume 

of rain on the filter strip (table 3). 

Excluding the partially monitored 

storm of June 2, 1998, the storm of 

June 27, 1998 produced the least rain 

(0.6 cm) and the smallest flow volumes. The storm of October 17, 1996 

was intermediate in rainfall (not flow 

volumes), with 3.6 cm of rain.

Average specific conductance of 

water from wells inside the filter strip 

was 2,603 μS/cm compared to 2,160 

μS/cm outside the filter strip. Average 

chemical constituent concentration in 

water from wells located inside the 

filter strip is similar to average chemical constituent concentrations in water 

from wells located outside the filter 

strip. 

ATTENUATION OF RUNOFF 

AND CHEMICAL LOADS

Attenuation values for runoff in 

the filter strips ranged from 47 to 98 

percent (tables 1 and 2; fig. 4). The 

smallest value was at the Bock site on 

May 14, 1996 where the soils were 

wet from previous rainfalls, which 

limited the ability to absorb new 

water. The largest value was at the 

Sanborn site on June 27, 1998 (table 

3). 

Sanborn

7/27/96

Sanborn

10/17/96

Sanborn

6/2/98

Sanborn

6/27/98

Bock

Bock

5/14/96

10/23/95

Bock

5/5/96

100

80

60

40

20

0

500,000

400,000

300,000

200,000

100,000

0

WATER VOLUME, IN LITERS

ATTENUATION VALUE IN FILTER STRIP, IN PERCENT

Volumes of feedlot runoff, feedlot runoff plus rain on the filter strip,

filter-strip runoff, and attenuation value in the filter strip.

Feedlot runoff entering filter strip

Feedlot runoff plus rain on filter strip

Filter strip runoff

Attenuation value in filter strip

EXPLANATION

Figure 4.
11

Table 5. Ground-water chemistry of the Bock and Sanborn site

[m, meter, μS/cm, micorsiemens per centimeter; °C degrees Celsius; mg/L, milligrams per liter; mL, milliliter; --, no data]

Average value

Number 

of wells

Number 

of samples

Average 

water 

level 

below 

ground 

surface 

(m)

Specific 

condutance 

(μS/cm)

pH Tempera- ture (°C)

Dissolved 

oxygen 

(mg/L)

Sulfate, 

dissolved 

(mg/L)

Chloride, 

dissolved 

(mg/L)

Nitrate, 

dissolved 

(mg/L)

Nitrite, 

dissolved 

(mg/L)

Ammonia, dissolved 

(mg/L)

Organic 

nitrogen, dissolved 

(mg/L)

Phosphorous, dissolved 

(mg/L)

Phophorous, 

ortho, 

dissolved 

(mg/L)

fecal 

coliform 

(colonies/100m

L)

Bock site

Wells inside 

filter strip

3 14 -- 1194 7.1 8.7 2.9 62 167 2.60 0.16 0.09 0.81 0.03 0.02 9 to 72

Standard deviation -- -- -- 520 0.3 4.0 1.9 36 110 4.73 0.32 0.10 0.63 0.05 0.02 --Wells outside 

filter strip

2 9 -- 890 7.3 7.8 2.9 53 123 0.35 0.02 0.04 0.29 0.02 0.02 <9

Standard deviation -- -- -- 95 0.3 3.7 2.0 11 22 0.37 0.01 0.03 0.14 0.01 0.01 --

Sanborn site

Wells inside 

filter strip

3 15 0.39 2603 6.9 10.1 1.0 408 272 0.13 0.03 0.48 0.95 0.03 0.02 <9

Standard deviation -- -- -- 405 0.4 1.4 1.2 173 72 0.13 0.06 0.20 0.72 0.03 0.01 --Wells outside 

filter strip

5 21 1.29 2160 7.1 8.6 2.5 414 237 0.16 0.02 0.25 0.67 0.04 0.03 <9

Standard deviation -- -- -- 483 0.4 2.2 1.9 102 70 0.33 0.03 0.33 0.45 0.06 0.03 --
12

trate completely to the water table and 

was stored in the soil. 

Sulfate is another plant essential 

nutrient that in its reduced form, sulfhydryl (SH-

), is used to synthesize 

amino acids (Kadlec and Knight, 

1996). Sulfate may also be reduced to 

volatile H2S gas. Increased sulfate 

concentrations in ground water 

beneath the Bock site filter strip indicates that sulfate infiltrated into 

ground water.

Nitrogen species in most feedlot 

runoff were dominated by organic 

nitrogen and ammonia plus organic 

nitrogen; while dissolved ammonia 

concentrations were comparatively 

smaller (tables 2 and 4). Such results 

are typical for runoff from cattle feedlots (Vellidis and others, 1996; Reaves 

and DuBowry, 1997). Exceptions 

occurred in feedlot runoff at the Bock 

site on May 5, 1996, and May 14, 

1996 when dissolved ammonia loads 

are approximately equivalent to the 

other two nitrogen species. Suspended 

phosphorous loads were larger than 

dissolved phosphorus loads in some 

samples, but the reverse was true in 

other samples. It is likely that suspended phosphorus was adsorbed to 

manure and soil particles. Sharpley 

and Smith (1995) indicated that suspended, adsorbed phosphorus is converted to inorganic phosphorus in 

soils receiving manure. The variability in the ratios of organic suspended 

and dissolved phosphorus species 

may reflect this process. 

Phosphorous is an essential plant 

nutrient and major cellular constituent. Plant uptake of dissolved orthophosphate may cause decreases of 

dissolved phosphorus loads in filterstrip runoff. Suspended phosphorous 

also may be bound to manure and soil 

particles. Decomposition of manure 

and release of phosphorus from soils 

would make it available for plant 

uptake. Suspended phosphorous also 

may be removed by filtration and sedimentation. 

Fecal coliform bacteria are not disease causing, but are indicators of 

pathogens. Fecal-coliform contaminated surface water typically contains 

200 to greater than 2,000,000 colonies/100 mL (Myers and Sylvester, 

1999). Feedlot runoff at the Sanborn 

site contained as much as 2.8x 10 13

colonies/100 mL. The decrease of 

fecal coliform colony counts in filterstrip runoff compared to feedlot runoff may be due to physical filtration, 

or prolonged exposure to sunlight, 

which can kill bacteria.

Loads of all constituents except 

two were less in filter strip runoff than 

in feedlot runoff at both sites (tables 2 

and 4). Nitrite plus nitrate nitrogen 

loads increased at the Sanborn site on 

July 27, 1996, but the feedlot runoff 

and filter-strip runoff loads were so 

small as to be practically indistinguishable. Sulfate loads also increased 

by 3 percent at the Sanborn site on 

June 27, 1998, but this small increase 

probably was within the error of the 

load calculation.

Decreases in ammonia loads in the 

filter strip may be due to plant uptake 

or volatilization. Oxidation of ammonia to nitrate is unimportant judging 

from the small nitrite plus nitrate 

loads. A source of ammonia is conversion from organic nitrogen by mineralization. Mineralization may be the 

cause of decreases in dissolved and 

suspended organic nitrogen. Organic 

nitrogen also may have decreased due 

to physical filtration by grass in the 

filter strip. 

Loads of fecal coliform bacteria 

were largest in the Sanborn samples 

from 1996 and smallest in the Sanborn samples from 1998. Despite the 

large fecal coliform loads in runoff, 

ground water beneath the filter strips 

contains only small concentrations of 

these bacteria (table 5). 

Attenuation of chemical loads 

could be evaluated for four events, 

three at the Sanborn site and one at the 

Bock site (fig. 5; tables 2 and 4). 

Attenuation values were uniformly 

largest for the storm of October 17, 

1996 at the Sanborn site and ranged 

from 72 to 82 percent (except for 

nitrate; table 4). The storm of July 27, 

1996 had attenuation values of 14 to 

54 percent (except for nitrate), and the 

storm of June 27, 1998 had values of 

6 to 67 percent (except for sulfate). 

Attenuation was greatest at colder 

temperatures (storm of October 17, 

1996) probably because freezing temperatures affected the filter-strip vegetation by causing the grass to wilt and 

lay close to the ground. The storm of 

May 14, 1996 at the Bock site had the 

next largest overall attenuation values, 

which ranged from 25 to 85 percent 

(table 2). Dissolved chloride, which is 

generally conservative in surface 

water, was attenuated 32 percent. The 

chloride lost in the filter strip may 

have infiltrated. Attenuation values 

for suspended constituents (62–85 

percent) tended to be larger than those 

for dissolved constituents (25–75 percent).

The time that feedlot runoff 

remains in the filter strip seems to 

have little systematic effect on attenuation values. For example, the duration of filter-strip runoff at the 

Sanborn site was 27.1 hours on July 

27, 1996, and 2.2 hours on June 27, 

1998 (table 3). Although runoff 

remained in the filter strip about 25 

hours longer on July 27, 1996, attenuation values were 85 percent on July 

27, 1996 and 98 percent on July 27, 

1998. Despite these differences in 

retention time, attenuation values 

were not demonstrably related to 

retention times.

 Some studies reported that suspended constituents are attenuated 

more efficiently than their dissolved 

equivalents (Dillaha and others, 

1986). This relation is apparent in the 

single set of attenuation values (May 

14, 1996) available for the Bock site 

(fig. 5; table 2). Attenuation values of 

nitrogen species are 61 percent for
13

dissolved ammonia-nitrogen and 49 

percent for dissolved organic nitrogen, but 85 percent for suspended 

ammonia plus organic nitrogen. Similarly, attenuation of dissolved phosphorus is 25 percent compared to 82 

percent for suspended phosphorus. At 

the Sanborn site on July 27, 1996, 

attenuation values of dissolved nitrogen species were less than those of 

suspended nitrogen species. On October 17, 1996, attenuation values of 

dissolved and suspended nitrogen species were generally equivalent. On 

June 27, 1998, the attenuation value 

for dissolved ammonia nitrogen was 

greater than for suspended ammonia 

plus organic nitrogen, but the attenuation value for dissolved organic nitrogen was less than the attenuation 

value for the suspended species. A 

similar pattern of dissolved greater 

than suspended was expressed for 

phosphorus species. The attenuation 

value for dissolved phosphorus was 

less than the attenuation value for suspended phosphorus on July 27, 1996, 

was nearly equivalent to the attenuation value for suspended phosphorus 

on October 17, 1996, and was greater 

than the attenuation value for suspended phosphorus on June 27, 1998. 

These complex patterns show that no 

single statement can be made concerning relative attenuation values of 

dissolved and suspended nitrogen and 

phosphorus species.

Attenuation of fecal coliform bacteria indicate that deposition of bacteria is increased when grass is flat 

lying (tables 2 and 4). There may also 

be an effect in which bacterial survival is improved at greater temperatures, perhaps because of beneficial 

physiological effects on bacteria. 

SANBORN

7/27/96

SANBORN

10/17/96

SANBORN

6/27/98

BOCK

5/14/96

80

60

40

20

0

10

30

50

70

90

PERCENT ATTENUATION

Attenuation values for chemical constituents in four runoff events.

Sulfate, dissolved

Chloride, dissolved

Ammonia, dissloved

Ammonia + organic N, suspended

Organic N, dissolved

P, disolved

P, suspended

Log fecal coliform bacteria

EXPLANATION

Figure 5.
14

REFERENCES

American Public Health Association, 

1985, Standard methods for examination of waste and wastewater 

(16th ed.): New York, American 

Public Health Association, 1268 p.

Chaubey, I., Edwards, D.R., Daniel, 

T.C., Moore, P.C., and Nichols, 

D.J., 1994, Effectiveness of vegetative filer strips in retaining surface-applied swine manure 

constituents: Transactions of 

American Society of Agricultural 

Engineering, v. 37, p. 845–850.

Clausen, J.C., and Meals, D.W., 1989, 

Water quality achievable with best 

management practices: Journal of 

Soil and Water Conservation, v. 

44, p. 593–596.

Dickey, E.C., and Vanderholm, D.H., 

1981, Vegetative filter treatment 

of livestock feedlot runoff: Journal 

of Environmental Quality, v. 10, p. 

279–284.

Dillaha, T.A., Reneau, R.B., 

Mostaghimi, S., and Lee, D., 1989, 

Vegetative filter strips for agricultural nonpoint source pollution 

control: Transactions of American 

Society of Agricultural Engineering, v. 32, p. 513–519.

Dillaha, T.A., Sherrard, J.H., Lee, D., 

Mostaghimi, D., and Shaholtz, 

V.O., 1988, Evaluation of vegetative filter strips as a best management practice for feed lots: Journal 

of Water Pollution Control Federation, v. 60, p. 1231–1238.

Dillaha, T.A., Sherrard, J.H., Lee, D., 

Shanholtz, V.O., and Mostaghimi, 

S., 1986 Use of vegetative filter 

strips to minimize sediment and 

phosphorus losses from feedlots—

Phase 1. Experimental plot studies: Blacksburg, VA, Virginia 

Water Resources Research Center, VPI-VWRRC-BULL-151, 68 

p.

Edwards, W.M., Owens, L.B., and 

White, R.K., 1983, Managing runoff from a small, paved beef feedlot: Journal of Environmental 

Quality, v. 12, p. 281–286.

Fishman, M.J., and Friedman, L.C., 

1989, Methods for determination 

of inorganic substances in water 

and fluvial sediments: U.S. Geological Survey Techniques of 

Water-Resources Investigations, 

book 5, chap. A1, p. 545.

Hammer, D.A., 1992, Designing constructed wetlands systems to treat 

agricultural nonpoint source pollution: Ecological Engineering, v. 1, 

p. 49–82.

Kadlec, R.H., and Knight, R.L., 1996, 

Treatment wetlands: Boca Raton, 

FL, CRC Press, Lewis, 893 p.

Magette, W.L., Brinsfield, R.B., 

Palmer, R.E., and Wood, J.D., 

1989, Nutrient and sediment 

removal by vegetative filter strips: 

Transactions of American Society 

of Agricultural Engineering, v. 32, 

p. 663–667.

Midwest Regional Climate Center, 

Climate data and summaries, 

SUMMARY

The attenuation efficiency of cattle feedlot runoff in two 

grass-covered filter strips in Minnesota was estimated by 

measuring chemical loads entering and leaving the filter 

strips. The Bock and Sanborn filter strips measured 60-m 

long and 20-m wide and received runoff from cattle feedlots that housed 35 and 225 cattle, respectively. Feedlot and 

filter-strip runoff was measured using flumes with stage 

sensors. Water samples were collected using automated 

samplers. 

Ground-water quality is a concern where feedlot-runoff 

infiltration is significant. Chemical changes in ground 

water from wells sampled inside the filter strips indicate 

that, for some parameters, filter-strip runoff degrades 

ground-water quality. Ground water from wells sampled 

inside the filter strips at the Bock site had elevated specific 

conductance, dissolved sulfate, dissolved chloride, dissolved nitrate, dissolved ammonia nitrogen, and dissolved 

organic nitrogen concentrations compared to ground water 

from wells outside the filter strip. Ground water from wells 

inside the Sanborn filter strip had increased ground-water 

levels, temperature, and dissolved ammonia nitrogen concentrations, and decreased dissolved oxygen concentrations 

beneath the filter strip compared to ground water from 

wells outside the filter strip. The greater effect on ground 

water at the Bock site likely is due to the greater hydraulic 

conductivity of soil compared to the Sanborn site.

Attenuation efficiencies from four storm-runoff events 

were calculated. Ground water sampled beneath and outside the filter strips indicated some infiltration losses of sulfate, chloride, and nitrogen at the Bock site where soil 

permeability was greater than the Sanborn site. Chemical 

constituents in filter-strip runoff, and their corresponding 

ranges of attenuation efficiency were as follows: chemical 

oxygen demand, 30 to 81 percent; dissolved sulfate, -3 to 

82 percent; dissolved chloride, 6 to 79 percent; dissolved 

ammonia nitrogen, 33 to 80 percent; suspended ammonia 

plus organic nitrogen, 29 to 85 percent; dissolved organic 

nitrogen, 14 to 75 percent; suspended phosphorus, 24 to 82 

percent; dissolved phosphorus, 14 to 72 percent; and fecal 

coliform bacteria, 18 to 79 percent. The ranges seem to be 

affected by barriers of direct contact of the runoff water 

with the soil. This varies seasonally by coverage of the soil 

by ice in winter and vegetation in summer months. Greater 

attenuation values occurred in October and May when mats 

of wilted, flat-lying grass covered the filter strips; values 

were less during the summer when tall growing grass covered the filter strips. 
15

accessed February 6, 2003, at: 

URL http://mcc.sws.uiuc.edu/cgibin/greet.cgi/

Myers, D.N., and Sylvester, M.A., 

1999, Fecal indicator bacteria, in

Wilde, F.D., and Radtke, D.B., 

eds., Field measurements: U.S. 

Geological Survey National Field 

Manual for the Collection of 

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