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The mission of the U.S. Geological Survey (USGS) is to 

assess the quantity and quality of the earth resources of the 

Nation and to provide information that will assist resource 

managers and policy makers at Federal, State, and local levels in 

making sound decisions. Assessment of water-quality conditions 

and trends is an important part of this overall mission.

One of the greatest challenges faced by water-resources 

scientists is acquiring reliable information that will guide the use 

and protection of the Nation’s water resources. That challenge is 

being addressed by Federal, State, interstate, and local waterresource agencies and by many academic institutions. These 

organizations are collecting water-quality data for a host of 

purposes that include: compliance with permits and water-supply 

standards; development of remediation plans for a specific 

contamination problem; operational decisions on industrial, 

wastewater, or water-supply facilities; and research on factors 

that affect water quality. An additional need for water-quality 

information is to provide a basis on which regional and nationallevel policy decisions can be based. Wise decisions must be 

based on sound information. As a society we need to know 

whether certain types of water-quality problems are isolated or 

ubiquitous, whether there are significant differences in conditions 

among regions, whether the conditions are changing over time, 

and why these conditions change from place to place and over 

time. The information can be used to help determine the efficacy 

of existing water-quality policies and to help analysts determine 

the need for and likely consequences of new policies.

To address these needs, the Congress appropriated funds in 

1986 for the USGS to begin a pilot program in seven project 

areas to develop and refine the National Water-Quality 

Assessment (NAWQA) Program. In 1991, the USGS began full 

implementation of the program. The NAWQA Program builds 

upon an existing base of water-quality studies of the USGS, as 

well as those of other Federal, State, and local agencies. The 

objectives of the NAWQA Program are to:

• Describe current water-quality conditions for a large part of 

the Nation’s freshwater streams, rivers, and aquifers.

• Describe how water quality is changing over time.

• Improve understanding of the primary natural and human 

factors that affect water-quality conditions.

This information will help support the development and 

evaluation of management, regulatory, and monitoring decisions 

by other Federal, State, and local agencies to protect, use, and 

enhance water resources.

The goals of the NAWQA Program are being achieved 

through ongoing and proposed investigations of 59 of the 

Nation’s most important river basins and aquifer systems, which 

are referred to as study units. These study units are distributed 

throughout the Nation and cover a diversity of hydrogeologic 

settings. More than two-thirds of the Nation’s freshwater use 

occurs within the 59 study units and more than two-thirds of the 

people served by public water-supply systems live within their 

boundaries.

National synthesis of data analysis, based on aggregation of 

comparable information obtained from the study units, is a major 

component of the program. This effort focuses on selected waterquality topics using nationally consistent information. 

Comparative studies will explain differences and similarities in 

observed water-quality conditions among study areas and will 

identify changes and trends and their causes. The first topics 

addressed by the national synthesis are pesticides, nutrients, 

volatile organic compounds, and aquatic biology. Discussions on 

these and other water-quality topics will be published in periodic 

summaries of the quality of the Nation’s ground and surface 

water as the information becomes available.

This report is an element of the comprehensive body of 

information developed as part of the NAWQA Program. The 

program depends heavily on the advice, cooperation, and 

information from many Federal, State, interstate, Tribal, and 

local agencies and the public. The assistance and suggestions of 

all are greatly appreciated.

Robert M. Hirsch

Chief Hydrologist
iv
v

0




Page

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

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

Background.......................................................................................................................................................................................2

Environmental setting.......................................................................................................................................................................4

Methods.......................................................................................................................................................................................................4

Site selection.....................................................................................................................................................................................4

Field methods....................................................................................................................................................................................8

Data analysis.....................................................................................................................................................................................8

Loads of nutrients and suspended sediment at fixed sites......................................................................................................................... 13

Total nitrogen.................................................................................................................................................................................. 13

Total phosphorus ............................................................................................................................................................................13

Suspended sediment........................................................................................................................................................................ 14

Instantaneous concentrations and yields of nutrients and suspended sediment ........................................................................................ 14

Comparisons of concentrations in increasing streamflow with other streamflow conditions........................................................ 14

Nitrogen in increasing streamflow.................................................................................................................................................. 14

Phosphorus in increasing streamflow............................................................................................................................................. 16

Suspended sediment in increasing streamflow............................................................................................................................... 16

Effects of land use and surficial geology on yields................................................................................................................................... 16

Land use.......................................................................................................................................................................................... 16

Surficial geology............................................................................................................................................................................. 20

Summary.................................................................................................................................................................................................... 21

References ................................................................................................................................................................................................. 22


	



Figures 1-3. Photographs showing:

1. Snowmelt runoff from the forested Trade River Basin, Wisconsin...................................................................................2

2. Snow and dirt in snow bank between cultivated field and Buffalo Creek in Minnesota ...................................................2

3. Construction activities, park, and mall parking lot adjacent to Shingle Creek in the Twin Cities 

metropolitan area, Minnesota.............................................................................................................................................2

Figures 4-5 Maps showing:

4. Location of the Upper Mississippi River Basin study unit, focused study area, Twin Cities 

metropolitan area, hydrology, selected towns, and major cities .......................................................................................3

5. Surficial geology, land use and land cover, and location of snowmelt runoff sampling sites in the Upper

Mississippi River Basin study unit.....................................................................................................................................5

Figure 6. Graph showing daily mean discharge, periods used to compute snowmelt loads, and sampling dates during

the 1997 snowmelt period at fixed sites in part of the Upper Mississippi River Basin study unit .................................. 12

Figures 7-9 Maps showing instantaneous:

7. Concentrations and yields of total nitrogen at sites sampled during 1997 snowmelt 

runoff in part of the Upper Mississippi River Basin study unit ...................................................................................... 15
vi


	

70



8. Concentrations and yields of total phosphorus at sites sampled during 1997 snowmelt

 runoff in part of the Upper Mississippi River Basin study unit ..................................................................................... 17

9. Concentrations and yields of suspended sediment at sites sampled during 1997 snowmelt 

runoff in part of the Upper Mississippi River Basin study unit ...................................................................................... 18

Figures10-11 Box plots showing instantaneous yields of:

10. Dissolved nitrate nitrogen and dissolved phosphorus for streams draining forested, agricultural,

 urban, and mixed land uses and land covers, during 1997 snowmelt runoff in part of the Upper 

Mississippi River Basin.................................................................................................................................................... 19 

11. Total nitrogen and total phosphorus in permeable and impermeable deposits for streams draining 

forested basins during 1997 snowmelt runoff in part of the Upper Mississippi River Basin .......................................... 20

84

1. Site characteristics for streams sampled during 1997 snowmelt runoff in the Upper Mississippi River Basin .....................................6

2. Summary statistics of load computation for total nitrogen, total phosphorus, and suspended sediment during 1997

and 1997 snowmelt runoff in Upper Mississippi River Basin study unit ............................................................................................ 12

0
	
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Multiply inch-pound unit By To obtain metric unit

inch (in.) 2.54 centimeter

ounce avoirdupois 28.35 gram

square mile (mi2

) 259.0 hectare

pounds per square mile per day (lb/mi2

/d) .175 kilograms per square kilometer per day

tons .907 metric tons

Chemical concentrations of substances are given in metric units of milligram per liter (mg/L). Milligrams per liter express the 

concentrations of the chemical constituent as a mass (mg) per unit volume (L). One milligram is one-thousandth of a gram.
1

86086

Water-quality degradation resulting from excessive nutrient and suspended-sediment transport is well 

known; however, the role of snowmelt 

runoff in transporting these constituents is less understood. Nutrients and 

suspended sediment are carried in 

streams all year, but increased concentrations and loads are associated 

with certain seasons and land uses. In 

temperate areas with seasonal snow 

and ice cover, spring snowmelt transports nutrients and sediment that have 

accumulated during the winter, adding 

to relatively constant sources such as 

ground water and wastewater treatment plants (WWTP). Forested areas 

may contribute nutrients and suspended sediment from decaying forest 

litter, wetlands, and eroding stream 

banks (fig. 1). Agricultural sources 

include material eroded by wind and 

water from cultivated fields, feedlots, 

and ditches (fig. 2). Urban sources 

include lawns, roads, parking lots, and 

winter construction activities (fig. 3). 

The quality of runoff from these land 

uses may also depend on surficial 

geologic characteristics or soil materials. For example, fine-grained surficial materials are typically less 

permeable and can contribute more 

fine-grained sediment to streams than 

coarse-grained, permeable deposits. 

As nutrients and sediment are transported by runoff from these landscapes, constituent loads (or mass of 

constituents transported by a stream in 

a specified time) can increase by 

orders of magnitude because both 

concentrations of constituents and 

rates of streamflow increase simultaneously.

During snowmelt runoff, the 

forms and concentrations of nutrients 

and suspended sediment carried by a 

stream vary with streamflow conditions. Immediately preceding snowmelt runoff streamflow is generally 

low; consequently, principal sources 

of nutrients may include ground-water 

discharge and WWTP effluent, in 

which soluble forms of nitrogen and 

phosphorus dominate. When snowmelt begins, streamflow and stream 

energy increase, as do concentrations 

of suspended sediment (and associated nutrients) (Guy, 1970). During 

the first few days of snowmelt, 

streams may carry substantial 

amounts of fine-grained sediment as a 

result of mass wasting and freezethaw cycles (Guy, 1970). Concentrations of suspended sediment generally 

peak on the rising limb of the 

hydrograph, before the streamflow 

peak, although characteristics of individual basins and runoff events affect 

this phenomenon (Guy, 1970). Particulate concentrations commonly 

decrease during the streamflow peak 

and recession because of decreased 

availability of source material, dilution by ground water and shallow subsurface flow, and decreased stream 

energy available for transporting suspended material. 

Increases in streamflow and nutrient and suspended sediment loads are 

apt to be more homogeneous across a 

region as a result of snowmelt than 

from rainfall. Snowmelt runoff typi-


	


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.8.08

The U.S. Geological Survey sampled snowmelt runoff 

from 42 stream sites during March and April 1997 in part 

of the Upper Mississippi River Basin, Minnesota and Wisconsin, to characterize nutrient and suspended-sediment 

concentrations, yields, and loads. Ancillary data from 12 

sites provided data to estimate constituent loads delivered 

during snowmelt and 1997. The snowmelt period contributed from 1 to 50 percent of 1997 annual loads of total 

nitrogen, total phosphorus, and suspended sediment at 

small stream sites, and 17 to 70 percent of annual loads at 

mainstem river sites. Small streams in agricultural areas 

transported the greatest proportions of annual loads during 

snowmelt. Snowmelt from urban streams transported the 

least proportions of annual loads. Agricultural streams had 

significantly greater median yields (p < 0.025) of dissolved 

nitrite, nitrate, phosphorus, orthophosphate, total nitrogen, 

and total phosphorus than forested sites, and significantly 

greater median yields (p < 0.025) of dissolved nitrate and 

orthophosphate than all other land uses. In forested areas, 

yields of suspended sediment and all nutrient forms were 

significantly greater (p < 0.05) for streams draining impermeable deposits than permeable deposits. 
2

cally results from warm conditions 

across a large area of relatively uniform snow pack that has accumulated 

during the winter. Rainfall runoff typically is less spatially and temporally 

homogeneous. Consequently, spring 

snowmelt offers the best opportunity 

to make comparisons of nutrient and 

sediment concentrations between 

many streams sampled simultaneously under high flow conditions.

=#

Little information exists to assess 

comparable loads and yields (mass 

transported by stream per unit time 

divided by the basin drainage area), of 

nutrients and suspended sediment 

from snowmelt runoff in streams 

across the Upper Mississippi River 

Basin, Minnesota and Wisconsin (fig. 

4), although selected areas have been 

investigated in separate studies. In 

Twin Cities metropolitan area 

(TCMA) streams, Oberts (1990) 

found maximum concentrations of 

soluble constituents, such as nitrate, 

occurred during the initial increase on 

the rising limb of the snowmelt 

hydrograph; whereas concentrations 

of particulate constituents peaked 

later. In the Minnesota River Basin, 

Payne (1994) noted that maximum 

concentrations of suspended sediment peaked immediately before the 

streamflow peak, although these data 

were for rainfall runoff. Grazyck 

(1986) noted that loads of suspended 

sediment, total nitrogen, and total 

phosphorus were greatest during 

March through May in the St. Croix 

River at St. Croix Falls, Wisconsin, 

based on data from 1974-83. No separate analysis was made of snowmeltrunoff data. 

In the spring of 1997, snow covered much of the Upper Mississippi 

River Basin, setting the stage for 

spring floods. Four factors contributed to these floods (Minnesota State 

Climatology Office, 1997): heavy 

autumn precipitation in 1996, extraordinary winter snowfall, rapid snowFigure 1.--Snowmelt runoff from the forested Trade River Basin in Wisconsin.

Figure 2.--Snow and dirt in snow bank between cultivated field and Buffalo

Creek in Minnesota.

Figure 3.--Construction activities, park, and mall parking lot adjacent to Shingle

Creek in the Twin Cities metropolitan area, Minnesota.
3

Base from U.S.

Geological Survey

digital data 1:2,000,000, 1972,

1:100,000, 1990, Albers Equal-Area

Conic projection. Standard parallels:

29°30' and 45°30', central meridian: -93°00'

WISCONSIN

The NAWQA study unit

MINNESOTA

MINNESOTA

RIVER

BASIN

MINNESOTA

RIVER

BASIN

CANNON/

VERMILLION

RIVER

BASINS

MISSISSIPPI

RIVER

BASIN

MISSISSIPPI

RIVER

BASIN ST. CROIX

RIVER

BASIN

Figure 4.--Location of the Upper Mississippi River Basin study unit and focused study area, Twin Cities metropolitan area,

hydrology, selected towns and major cities.

0 25 50 75 Miles

0 25 50 75 Kilometers

Stillwater

Burkhardt

Somerset

St. Paul St. Paul

Prescott

Brooklyn Park

Champlin

Anoka

Brooklyn Center

Empire

45°

44°

46°

47°

95°

96°

97°

94° 93°

92°

91°

Lake

Pepin Minnesota River Straight R.

MINNESOTA MINNESOTA WISCONSIN WISCONSIN Mille

Lacs

Lake

Yellow River

Trade R. Trade R.

Sunrise R. Sunrise R.

Elm Cr.

Elk River

Apple R.

St. Croix

River

Clam R.

Willow R. Willow R. Willow R.

Wood

R.

Rush River Rush River

Kettle River

Lake

Itasca

S e n ka River

Namekagon Ri r ve

Sauk R iver

Rum River

Nort k h For

South or F k

Buffalo Creek

CrowR.

Ve o rmilli n R. Cannon

River

Burkhardt

Somerset

Stillwater

St. Paul

Prescott

Brooklyn Park

Champlin

Anoka

Hastings

Brooklyn Center

Empire

EXPLANATION

Twin Cities metropolitan area

Boundary of focused study area

Minneapolis

Beauford

Faribault

River

Falls

Woodland

Corner

Webster

Trade River Trade River

Osceola Range

Rockford

Glencoe

Biscay

Jordan

Mankato

Red Wing

Danbury

Leonards

Hinckley

Maiden

Rock

St. Francis St. Francis

Big Lake Big Lake

St. Croix Falls St. Croix Falls

St. Cloud St. Cloud

Paynesville

Beauford

Faribault

Welch

River

Falls

Woodland

Corner

Webster

Siren

Trade River

Osceola Range

Sunrise

Rockford

Glencoe

Biscay

Jordan

Mankato

Red Wing

Danbury

Leonards

Hinckley

Sandstone

Pine City

Maiden

Rock

St. Francis

Big Lake

Grantsburg

St. Croix Falls

St. Cloud

Paynesville

Bloomington

Nine Mile Cr.

L. b

Cob R. L. b Cob R. L. bCob R.

Shingle Cr.Shingle Cr.Shingle Cr.

Kinnick ni nic R.Kinnick ni nic R.Kinnick ni nic R.

Royalton

M i is s si si p e p i R v rM

i is

s

si si p

e

p i R

v

r

M i is s si si p e p i R v r

IOWA

S. DAK.
4

melt conditions, and heavy early 

spring precipitation. Autumn precipitation in 1996 was in the 95th percentile for most of Minnesota, resulting 

in above-median streamflows in the 

fall and winter. Heavy winter snowfall ranged from the 50th to 99th percentile based on 1931-91 records. 

Water equivalents of the snowpack in 

February 1997 ranged from 1 in. in 

the southern Minnesota River Basin to 

8 in. in the headwaters of the Minnesota and Mississippi Rivers. Snowpack in the headwaters of the St. 

Croix River Basin had a water equivalent of 5-7 in. (National Weather Service, 1997). Winter and early spring 

had few melting days, and an abrupt 

warming trend occurred the first week 

of April coinciding with as much as 

3.63 in. of rain in parts of the basin on 

April 5 and 6. These conditions 

resulted in near record streamflow for 

many streams. The third to fifth 

greatest recorded streamflow peaks 

occurred on the Mississippi River 

near Anoka and St. Paul, the Minnesota River near Jordan, and the Sauk, 

Crow, and Snake Rivers. Peak flows 

were more normal in the extreme 

southern part of the study unit 

because of an earlier and more gradual snowmelt.

The lack of information on snowmelt runoff and the deep snowpack of 

1997 in the Upper Mississippi River 

Basin led to a study of nutrients and 

suspended sediment in snowmelt runoff. The study was part of the U.S. 

Geological Survey’s National WaterQuality Assessment (NAWQA) Program. Goals of the NAWQA Program 

(Gilliom and others, 1995), which 

began full implementation in 1991, 

are to (1) describe the water quality in 

a large part of the Nation’s freshwater 

streams and aquifers; (2) describe 

water quality changes over time; and 

(3) improve the understanding of how 

physical, ecological, and human factors, including land use, affect water 

quality. The Upper Mississippi River 

Basin study unit of NAWQA encompasses the Upper Mississippi River 

Basin upstream from the outlet of 

Lake Pepin (fig. 4).

The purposes of the study were 

to: (1) compare the proportions of 

total nitrogen, total phosphorus, and 

suspended-sediment loads contributed 

during the 1997 snowmelt to annual 

loads; (2) characterize instantaneous 

concentrations and yields of nutrients 

and suspended sediment in streams 

during increasing streamflow conditions from snowmelt runoff; and (3) 

compare the concentrations and yields 

for streams draining different land 

uses and surficial deposits. 

The study was conducted in part 

of the Upper Mississippi River Basin 

NAWQA study unit (fig. 4) during 

March and April 1997. Sampling targeted a smaller focused study area in 

the southeastern one-third of the study 

unit (fig. 4) which included all of the 

St. Croix River Basin, the Mississippi 

River Basin from Royalton, Minnesota to Lake Pepin, and a part of the 

Minnesota River Basin. Twenty sites 

were sampled in the St. Croix River 

Basin, 3 in the Minnesota River 

Basin, and 19 along the Mississippi 

River mainstem and its tributaries 

(fig. 5). The purpose of this report is 

to present the results of the study. 

>	


	#

Land use and land cover, hereinafter referred to as land use, in the 

Upper Mississippi River Basin study 

unit and the focused study area ranges 

from relatively undisturbed secondgrowth forests and wetlands in the 

north to intense row crop (mostly corn 

and soybean) agriculture, dairy farms, 

and feed lots in the south and west 

(fig. 5). The seven county TCMA, 

with a population of 2.3 million people (U.S. Bureau of Census, 1991), 

overlays this land-use continuum in 

the southeast part of the focused study 

area. 

Surficial geology is characterized 

by relatively permeable fluvial deposits of outwash or alluvium, hereinafter 

referred to as permeable deposits, and 

by relatively impermeable deposits of 

glacial tills or lake sediments, hereinafter referred to as impermeable 

deposits. Permeable deposits are 

composed of sorted sand and gravel. 

Impermeable deposits are composed 

of unsorted mixtures of fine-grained 

(less than 0.063 millimeters) clay and 

silt, and coarser-grained sand, gravel, 

and larger particles; or sorted silts and 

clays. Soils developed on finegrained, unsorted impermeable deposits often are more vulnerable to erosion than coarser-grained, sorted 

permeable deposits (U.S. Department 

of Agriculture, 1978 and 1979). Distribution of these surficial deposits is 

complex, but generally, permeable 

deposits dominate the Wisconsin part 

of the upper St. Croix River Basin, 

and the Sunrise, lower Rum, Elk, 

North Fork Crow, and Vermillion 

River Basins (fig. 4 and 5). Impermeable deposits compose most of the 

rest of the focused study area. Land 

use and land cover, and surficial geology are discussed in more detail in 

Stark and others (1996).

98:6

This section summarizes the 

methods used to select sampling sites, 

sample, and analyze data. Methods 

and protocols of the NAWQA Program were used as cited unless noted 

otherwise. 

	

	

Twelve sampling sites were part 

of a regularly sampled network of 

Upper Mississippi River Basin 

NAWQA sites, referred to as fixed 

sites (fig. 5, table 1). At fixed sites, 

ancillary data from analyses of samples collected monthly or more frequently during 1996-98 were used to 

interpret results from this study and to 

estimate nutrient and suspended-sediment loads. Fixed sites were located 
5

45°

44°

46°

47°

95°

96°

97°

94° 93°

92°

91°

Base from U.S. Geological

Survey digital data 1:2,000,000, 1972,

1:100,000, 1990, Albers Equal-Area

Conic projection. Standard parallels:

29°30' and 45°30', central meridian: -93°00'

0 25 50 75 Miles

0 25 50 75 Kilometers

Surficial geology modified

from Olcott, 1992; land use

and land cover from Hitt, 1994.

1 2

3

4 5

6 9

11

12

10

13

16

15

14

17

19

20

18 21

22

23

24

25

26

27

29

30

31 32

33 34

35

36

37 38

39

40 41 42

28

7 8

Figure 5.--Surficial geology, land use and land cover, and location of snowmelt runoff sampling sites

in the Upper Mississippi River Basin study unit.

MINNESOTA MINNESOTA WISCONSIN WISCONSIN

D

D

D

D

D

D DD

D

D

D

D

D

D

D

D

D

D

D D

D

DD

D

D

D

D

D

D

D

D

D

D

D

D

D

DD

D D

D

D

Sampling site. Number corresponds to

map identifier in table 1:

Fixed site with three or more

samples collected

Synoptic site with one sample

collected

4

5

EXPLANATION

SURFICIAL GEOLOGY

Outwash

or alluvium

Forest

Agriculture

Urban

Rangeland

Water

Wetland

Other

Till or lake

sediment

LAND USE AND LAND COVER

D

D

Boundary of focused study area
6

Table 1. Site characteristics for streams sampled during 1997 snowmelt runoff in part of the Upper Mississippi 

[Bold text indicates fixed site (figure 5); mi2, square mile]

Land use (pe

Map 

identifier 

(shown in 

figure 5)

Site 

identifier Site name Latitude Longitude Dominant surficial geology Urban Agriculture Forest 

1 05267000 Mississippi River near Royalton, Minn. 45o51’40” 094o21’30” Outwash-Alluvium 0.6 25 49 82 05268000 Platte River at Royalton, Minn. 45o50’43” 094o17’40” Outwash-Alluvium 0.4 64 23 1

3 05270500 Sauk River near St. Cloud, Minn. 45o33’35” 094o14’00” Outwash-Alluvium 1.1 83 8.4 4

4 05275000 Elk River near Big Lake, Minn. 45o20’02” 093o40’00” Outwash-Alluvium 0.8 75 10 1

5 05276005 North Fork Crow River above Paynesville, Minn. 45o22’38” 094o47’00” Outwash-Alluvium 0.3 90 2.1 1

6 05278400 North Fork Crow River near Rock- ford, Minn. 45o05’44” 093o47’18” Till plain-Lake sediment 1.2 83 6.3 6

7 05278590 South Fork Crow River at Biscay, Minn. 44o50’11” 094o17’16” Till plain-Lake sediment 2.3 89 0.6 6

8 05278930 Buffalo Creek near Glencoe, Minn. 44o45’50” 094o05’27” Till plain-Lake sediment 0.7 96 0 1

9 05280000 Crow River at Rockford, Minn. 45o05’12” 093o44’02” Till plain-Lake sediment 1.4 87 3.7 4

10 05286000 Rum River near St. Francis, Minn. 45o19’40” 093o22’20” Outwash-Alluvium 0.5 47 22 1

11 05287890 Elm Creek near Champlin, Minn. 45o09’48” 093o26’11” Till plain-Lake sediment 8.7 84 1.6 2

12 05288500 Mississippi River near Anoka, Minn. 45o07’36” 093o17’48” Outwash-Alluvium 1.1 45 34 7

13 05288705 Shingle Creek at Queen Ave in Minneapolis, Minn. 45o03’00” 093o18’36” Outwash-Alluvium 71 20 0.9 4

14 05320270 Little Cobb River near Beauford, Minn. 43o59’48” 093o54’30” Till plain-Lake sediment 0.2 94 0.5 0

15 05330000 Minnesota River near Jordan, Minn. 44o41’35” 093o38’30” Till plain-Lake sediment 0.9 94 1.7 2

16 05330902 Nine Mile Creek near James Circle at Bloomington, Minn. 44o48’26” 093o18’05” Till plain-Lake sediment 87 5.7 2.2 3

17 05331580 Mississippi River below Lock & Dam #2 at Hastings, Minn. 44o44’48” 092o51’08” Till plain-Lake sediment 2.5 66 18 5

18 05331775 St. Croix River near Woodland Cor- ner, Wis. 46o07’00” 092o07’53” Outwash-Alluvium 0.2 1.0 86 3

19 05331833 Namekagon River at Leonards, Wis. 46o10’18” 091o19’50” Outwash-Alluvium 0.7 1.8 78 6

20 05333400 Namekagon River near Woodland Corner, Wis. 46o05’02” 092o06’47” Outwash-Alluvium 0.4 6.0 76 4

21 05333500 St. Croix River near Danbury, Wis. 46o04’28” 092o14’50” Outwash-Alluvium 0.3 4.9 79 4
7

22 053350006 Yellow River near Danbury, Wis. 45o58’59” 092o23’05” Outwash-Alluvium 0.8 23 56 9

23 05335170 Crooked Creek near Hinckley, Minn. 46o00’42” 092o31’45” Outwash-Alluvium 0 18 69 1

24 05335500 Clam River near Webster, Wis. 45o52’52” 092o29’16” Outwash-Alluvium 0.3 32 55 3

25 05336700 Kettle River below Sandstone, Minn. 46o06’20” 092o51’50” Outwash-Alluvium 0.5 27 53 1

26 05338500 Snake River near Pine City, Minn. 45o50’30” 092o56’00” Till plain-Lake sediment 0.4 40 42 1

27 05338975 Wood River at State Highway 70 near Grantsburg, Wis. 45o46’22” 092o42’29” Outwash-Alluvium 0.6 44 27 5

28 453049- 092512101 Sunrise River at Sunrise, Minn. 45o30’49” 092o51’21” Outwash-Alluvium 2.9 58 8.3 5

29 05340370 Trade River near Trade River, Wis. 45o35’58” 092o46’02” Outwash-Alluvium 0.5 47 38 2

30 05340500 St. Croix River at St. Croix Falls, Wis. 45o24’25” 092o38’49” Till plain-Lake sediment 0.4 26 56 2

31 053405524 St. Croix River tributary near Osceola, Wis. 45o20’52” 092o40’55” Till plain-Lake sediment 4.4 65 29 0

32 05341125 Apple River near Range, Wis. 45o23’45” 092o21’50” Outwash-Alluvium 0 44 40 5

33 05341500 Apple River near Somerset, Wis. 45o09’27” 092o42’59” Till plain-Lake sediment 0.5 63 24 5

34 05341540 Browns Creek at Stillwater, Minn. 45o04’35” 092o48’21” Till plain-Lake sediment 6.7 80 5.8 4

35 05341740 Willow River at Burkhardt, Wis. 45o01’30” 092o39’23” Outwash-Alluvium 1.1 89 7.8 0

36 05342000 Kinnickinnic River near River Falls, Wis. 44o49’50” 092o44’00” Till plain-Lake sediment 3.6 92 4.6 0

37 05344490 St. Croix River at Prescott, Wis. 44o44’57” 092o48’16” Till plain-Lake sediment 0.9 36.7 46.8 3

38 05345000 Vermillion River near Empire, Minn. 44o40’00” 093o03’17” Outwash-Alluvium 16 76 3.9 1

39 05353800 Straight River near Faribault, Minn. 44o15’29” 093o13’51” Till plain-Lake sediment 3.5 92 1.5 0

40 05355200 Cannon River at Welch, Minn. 44o33’50” 092o43’55” Till plain-Lake sediment 2.8 88 4.0 2

41 05355250 Mississippi River at Red Wing, Minn. 44o36’36” 092o36’36” Till plain-Lake sediment 2.3 62 22 4

42 05355330 Rush River near Maiden Rock, Wis. 44o34’15” 092o19’44” Till plain-Lake sediment 0.5 88 11 0

1.Percentages associated with each site may not total 100 percent because of rounding. 

Table 1. Site characteristics for streams sampled during 1997 snowmelt runoff in part of the Upper Mississippi River B

[Bold text indicates fixed site (figure 5); mi2, square mile]

Land use (pe

Map 

identifier 

(shown in 

figure 5)

Site 

identifier Site name Latitude Longitude Dominant surficial geology Urban Agriculture Forest 
8

on either small streams or large mainstem rivers. Fixed sites on small 

streams, with drainage areas of 28.2 to 

232 mi2, were located downstream of 

a predominant land use—either forested, agricultural, or urban. Because 

water quality from these streams is 

indicative of a predominant land use, 

they are referred to as indicator sites. 

Fixed sites on mainstem rivers, 

including the Mississippi, Minnesota, 

and St. Croix Rivers, drained large 

areas (1,510 to 46,800 mi2). These 

sites were located at transitional areas 

of rivers, such as at the transition 

between forested and agricultural 

areas or between agricultural and 

urban areas. Because water quality at 

these sites represents integrated 

effects from large areas and sometimes varying land use, they are 

referred to as integrator sites.

Thirty additional sites, referred to 

as synoptic sites, were selected to 

encompass combinations of land use 

and surficial geology common in the 

focused study area (figs. 4 and 5). 

Twenty-four synoptic sites represented the only sampling location on a 

particular stream. Larger tributaries 

had multiple sites. Drainage areas 

upstream of synoptic sites ranged 

from 10.0 to 7,690 mi2

. To supplement this analysis, data from Elm 

Creek near Champlin, Minnesota (site 

11, fig. 5) were included because samples were collected using similar protocols and were analyzed for similar 

constituents. Although technically 

not part of this study, that site is 

included as one of the 30 synoptic 

sites.

Percentages of land use (forested, 

agricultural, urban, wetland, water, or 

other, which includes rangeland) and 

surficial geology (permeable or 

impermeable deposits) were computed for basins upstream of each site. 

Streams were classified by the predominant land use and surficial geology of each basin. Streams were 

classified as forested if they drained 

more than 65 percent forests and wetlands; agricultural if they drained 

more than 80 percent agricultural 

area, urban if they were located in the 

TCMA and drained more than 5 percent urban area, and mixed if they fell 

between these categories (36-75 percent agricultural, 22-59 percent forest 

and wetlands, and 0-5 percent urban). 

No urban sites were located downstream of WWTPs. Ten stream sites 

were classified as forested, 13 as agricultural, 5 as urban, and 14 as mixed 

land use. Similarly, streams were 

classified as draining either permeable 

or impermeable geologic deposits if 

they drained more than 50 percent of 

each respective deposit. Twenty-two 

stream sites were classified as draining permeable geologic deposits and 

20 were classified as draining impermeable deposits. Selected streams 

draining small basins were sampled to 

account for combinations of land use 

and surficial geology that did not exist 

in larger basins, such as urban or forested areas in permeable deposits. 

Characteristics of stream sites sampled in this investigation are given in 

Stark and others (1999).

5	


At fixed sites, samples were collected and processed using NAWQA 

protocols (Shelton, 1994). Additional 

samples were collected at these sites 

before and after the increasing streamflow of snowmelt runoff so that concentrations and yields associated with 

increasing streamflow conditions 

could be compared to concentrations 

and yields associated with other 

streamflow conditions during snowmelt.

At the 30 synoptic sites, samples 

were collected and processed using 

modified equipment and protocols to 

shorten sampling times and increase 

sampling coverage. Modifications 

included: reducing the number of 

equal-width-increment sampling 

transects from 10-20 to 3-5; collecting 

suspended-sediment samples separate 

from nutrients; and splitting composite samples for total nutrients by mixing and pouring from 3-liter 

polypropylene bottles instead of using 

cone splitters. When two or more 

sites were sampled with the same 

equipment on the same day, equipment was triple rinsed with both 

deionized water after sampling and 

rinsed with native water from each 

subsequent site prior to sampling. 

Equipment was cleaned according to 

NAWQA protocols at the end of each 

day (Shelton, 1994). 

Nutrient samples were chilled and 

shipped on ice within 48 hours to the 

USGS National Water-Quality Laboratory in Arvada, Colorado. Analyses 

included dissolved nitrite nitrogen, 

dissolved nitrite plus nitrate nitrogen, 

dissolved ammonia plus organic nitrogen, total ammonia plus organic nitrogen, total phosphorus, dissolved 

phosphorus, and dissolved orthophosphate. Sediment samples were 

shipped to a USGS sediment laboratory in Iowa City, Iowa, for analysis 

of total suspended-sediment concentration and percentage suspended-sediment material that is either finegrained (less than 0.063 millimeters) 

or sand sized (0.063 to 2.0 millimeters).

Stream mixing was assessed by 

taking measurements of water temperature, pH, specific conductance, and 

dissolved oxygen and comparing 

results across the stream. Stream stage 

was measured before and after sampling to document changing stage 

conditions. Streamflow was measured at sites lacking current stagedischarge relations or obtained from 

stage-discharge relations where available. Barometric pressure was 

recorded to calibrate dissolved oxygen meters and to calculate the percent saturation of dissolved oxygen in 

streams.


(
	

Total nitrogen was calculated as 

the sum of total ammonia plus organic 
9

nitrogen and dissolved nitrite plus 

nitrate nitrogen, for use in determining concentrations, yields, and loads. 

Particulate nitrogen was calculated as 

total ammonia and organic nitrogen 

minus dissolved ammonia and organic 

nitrogen. Particulate phosphorus was 

calculated as the difference between 

total phosphorus and dissolved phosphorus. 

Nutrient and suspended-sediment 

loads at the fixed sites were determined using the U.S. Geological Survey’s ESTIMATOR program (T. Cohn 

and E. Gilroy, U.S. Geological Survey, written commun., 1993; Cohn 

and others, 1989: Cohn and others, 

1992a; Cohn and others, 1992b) by 

summing the daily-mean loads of the 

annual or snowmelt periods. ESTIMATOR computes a logarithm-linear 

model that uses a minimum-variance, 

unbiased estimator to minimize error 

from the retransformation bias associated with logarithm-linear regression 

models and uses an adjusted maximum likelihood estimator to compensate for censored values below 

method reporting limits. The regression equations used in ESTIMATOR 

contained some or all of the following 

terms based on a statistical significance of p < 0.05: a constant; logarithm of flow, logarithm of flow 

squared, and square root of flow fits 

to discharge; fractional time fits for 

temporal trends; sine and cosine fits 

to accommodate seasonality. Models 

were calibrated with daily-mean 

streamflow data and with sediment 

and nutrient sample analyses from 

fixed sites during 1996-98 (Mitton 

and others, 1997, 1998, and 1999). 

Because the accuracy of load calculations depends on many factors, 

including range of concentrations and 

streamflow, number of samples, and 

climatological conditions, the accuracy of the model should be considered for each site and load estimate. 

For these reasons, error estimates are 

presented as confidence intervals 

along with load estimates in table 2.

Confidence intervals for the 95th

percentile were computed by multiplying the standard error of prediction 

by 1.96 (two standard deviations) 

from the standard normal distribution 

curve. The standard error of prediction was included in the ESTIMATOR 

output as the daily mean per month 

and as the daily mean per year. The 

95th percentile for the annual loads 

was calculated from the daily mean 

per year standard error of prediction. 

For the snowmelt loads the 95th percent confidence interval was calculated from the daily standard error of 

prediction from monthly data and was 

used in the same manner that the 

monthly mean daily loads were used 

to compute snowmelt loads. In the 

case of total nitrogen, the standard 

errors of prediction were calculated 

by taking the square root of the sum 

of the standard error of predictions 

squared for total nitrite plus nitrate 

nitrogen and total organic plus ammonia nitrogen standard errors of prediction.

Annual loads were calculated for 

the 1997 calendar year for the 12 

fixed sites. Loads contributed by 

snowmelt were based on the individual snowmelt hydrograph for each 

fixed site. The snowmelt part of the 

hydrograph was defined as the period 

from the initial increase in streamflow 

after winter through peak flow and 

part of the recession. The end of the 

recession was considered to occur 

when the decrease in daily mean 

streamflow was less than 20 percent 

of the maximum decrease in daily 

mean streamflow for any three consecutive days during the recession. 

Snowmelt hydrographs and periods 

used for computing constituent loads 

are shown in figure 6. This method 

worked well for 11 of 12 fixed sites. 

However, at the Namekagon River at 

Leonards, Wisconsin, the slope of the 

streamflow recession was so flat that 

the snowmelt period defined using 

these methods would have been much 

shorter than other sites. To make 

results more comparable, the second 

local maximum daily decrease was 

used in place of the first maximum to 

effectively lengthen the snowmelt 

period. The lengths of the snowmelt 

periods vary because of different 

basin sizes and characteristics, snowpack conditions, precipitation during 

snowmelt, daily temperature, land 

use, and surficial geology.

For samples collected at all 42 

sites during increasing streamflow 

conditions, instantaneous yields of 

selected constituents were calculated 

as the product of the constituent concentration and the instantaneous 

streamflow at the time of sampling 

divided by the drainage area of the 

stream. For convenience, these yields 

are reported in pounds per square mile 

per day (lb/mi2/d). 

In some streams, such as mainstem river sites, the contribution of 

water stored in pools and reservoirs 

upstream of dams could confound the 

effects of snowmelt runoff on water 

quality by contributing substantial 

amounts of water from non-snowmelt 

origin. However, samples collected 

from mainstem rivers for comparisons 

of instantaneous concentrations were 

collected near the peaks of streamflow 

hydrographs (fig. 5). Consequently, 

the large volumes of water transported 

during streamflow rises from snowmelt runoff would likely have flushed 

most water that was stored in pools 

and reservoirs prior to snowmelt.

Concentrations of suspended sediment and nutrients can vary substantially during the rising part of the 

hydrograph. Consequently, individual 

comparisons of instantaneous concentrations and yields between sites were 

not made. Instead, sites were grouped 

by land use and surficial geology (permeable or impermeable deposits) for 

statistical analysis to minimize the 
10

Table 2. Summary statistics of load computations for total nitrogen, total phosphorus, and suspended sediment during 1997 a

[mi2, square mile; Ave., Avenue; Cir., Circle; L&D, Lock and Dam; St., Saint]

1997 annual statistics 1997 sn

Site type and name

Map 

identifier 

(figure 5)

 Principal land 

use and land 

cover

 Load (tons)

 95thpercentile 

confidence 

interval 

(percent)

 Yield

 (tons per 

mi2)

 Load

 (tons)

p

co

(

Total nitrogen

Indicator (small stream) sites

North Fork Crow River above Paynesville, Minn. 5 Ag 347 25 1.49 142 Shingle Creek at Queen Ave. in Minneapolis, Minn. 13 Urban 26 17 0.93 3.4 Little Cobb River near Beauford, Minn. 14 Ag 1,000 42 7.72 507 9-Mile Creek near James Cir. at Bloomington, Minn. 16 Urban 45 26 1.00 2.3 Namekagon River at Leonards, Wis. 19 Forest 55 9 0.43 9.5 

Integrator (mainstem river) sites

Mississippi River near Royalton, Minn. 1 Forest 6,830 12 0.59 1,950 Mississippi River near Anoka, Minn. 12 Mixed 19,200 22 1.00 7,440 Minnesota River near Jordan, Minn. 15 Ag 85,900 63 5.29 37,000 Mississippi River below L&D 2 at Hastings, Minn. 17 Mixed 97,800 27 2.64 47,800 St. Croix River near Danbury, Minn. 21 Forest 641 12 0.43 110 St. Croix River at St. Croix Falls, Minn. 30 Forest 3,660 16 0.61 1,440 Mississippi River at Red Wing, Minn. 41 Mixed 99,000 25 2.12 47,500 

Total phosphorus

Indicator (small stream) sites

North Fork Crow River above Paynesville, Minn. 5 Ag 26 43 0.11 13 Shingle Creek at Queen Ave. in Minneapolis, Minn. 13 Urban 2.3 25 0.08 0.2 Little Cobb River near Beauford, Minn. 14 Ag 18 35 0.14 7.7 9-Mile Creek near James Cir. at Bloomington, Minn. 16 Urban 4.1 31 0.09 0.2 

Integrator (mainstem river) sites

Mississippi River near Anoka, Minn. 12 Mixed 1,060 22 0.06 381 Minnesota River near Jordan, Minn. 15 Ag 3,150 32 0.19 1,700 Mississippi River below L&D 2 at Hastings, Minn. 17 Mixed 5,170 18 0.14 2,530 Mississippi River at Red Wing, Minn. 41 Mixed 4,580 15 0.10 1,810 
11

Suspended sediment

Indicator (small stream) sites

North Fork Crow River above Paynesville, Minn. 5 Ag 6,130 36 26.4 1,620 Shingle Creek at Queen Ave. in Minneapolis, Minn. 13 Urban 903 32 32.2 99 Little Cobb River near Beauford, Minn. 14 Ag 13,900 35 107 6,020 9-Mile Creek nr James Cir. at Bloomington, Minn. 16 Urban 7,060 120 157 65 Namekagon River at Leonards, Wis. 19 Forest 567 21 4.43 106 

Integrator (mainstem river) sites

Mississippi River near Royalton, Minn. 1 Forest 135,000 35 11.6 64,000 Mississippi River near Anoka, Minn. 12 Mixed 325,000 45 16.9 172,000 Minnesota River near Jordan, Minn. 15 Ag 2,130,000 21 131 805,000 Mississippi River below L&D 2 at Hastings, Minn. 17 Mixed 2,650,000 39 71.5 1,280,000 St. Croix River near Danbury, Minn. 21 Forest 8,820 20 5.86 2,070 St. Croix River at St. Croix Falls, Minn. 30 Forest 102,000 43 17.0 71,100 Mississippi River at Red Wing, Minn. 41 Mixed 2,400,000 48 51.2 1,050,000 

Table 2. Summary statistics of load computations for total nitrogen, total phosphorus, and suspended sediment during 1997 and 199

[mi2, square mile; Ave., Avenue; Cir., Circle; L&D, Lock and Dam; St., Saint]

1997 annual statistics 1997 sn

Site type and name

Map 

identifier 

(figure 5)

 Principal land 

use and land 

cover

 Load (tons)

 95thpercentile 

confidence 

interval 

(percent)

 Yield

 (tons per 

mi2)

 Load

 (tons)

p

co

(
12

February 1 March 1

1997

Figure 6.--Daily mean discharge, periods used to compute snowmelt loads, and sampling dates during the 1997 snowmelt period

at fixed sites in part of the Upper Mississippi River Basin study unit.

1,000

100

10

1

10,000

100,000

1,000,000

DAILY MEAN DISCHARGE, IN CUBIC FEET PER SECOND

April 1 May 1

Daily mean

discharge

Daily mean

discharge on

sample date

Daily mean discharge

used to calculate

snowmelt loads

41

17

41

Map identifier as

shown in Table 1

12 1

15

5

14

16

13

19

21

30

Drains forested land use areas

Drains agricultural land use areas

Drains urban land use areas

Drains mixed land use areas
13

bias introduced by variability among 

individual samples. 

Comparisons of instantaneous 

yields for streams draining different 

categories of land use or surficial 

geology were made using the nonparametric, Kruskal-Wallis, one-way 

analysis of variance (ANOVA) of the 

medians, because the data were not 

normally distributed and because 

sample sizes were small and variable 

(5 to 14 samples per site). For comparisons between the four land-use 

categories, a multiple-stage test was 

performed on the Kruskal-Wallis statistics (Helsel and Hirsch, 1992). 

Results were considered statistically 

significant between the four land-use 

categories for p < 0.05 during the first 

step of the test and p < 0.025 for the 

final step between any two categories 

(Helsel and Hirsch, 1992). Within 

both the forested and mixed land-use 

categories, comparisons for yields for 

streams draining permeable and 

impermeable deposits were considered significantly different for p < 

0.05. Comparisons for yields for 

streams draining permeable and 

impermeable deposits in agricultural 

and urban areas were not possible 

because there were not enough agricultural and urban streams with both 

types of deposits for valid statistical 

analyses. Only samples collected during increasing stream stages were 

used for comparisons to minimize the 

variability in concentrations that 

occur over the hydrograph.

;6.6&898.

'99998.8

&<989

At fixed sites, from 1 to 70 percent of 1997 annual loads of total 

nitrogen, total phosphorus, and suspended sediment were transported 

during the snowmelt period. Agricultural streams generally transported the 

greatest proportions of loads during 

snowmelt. 

?
$	
#

At indicator sites, total nitrogen 

loads ranged from 26 to 1,000 tons in 

1997 (table 2). Snowmelt loads 

ranged from 2.3 to 507 tons, composing 5 to 50 percent of respective 

annual loads (table 2). Snowmelt from 

urban streams transported the least 

proportions of annual loads (table 2). 

Relatively large amounts of impervious surfaces in urban areas reduce 

vegetation and soil cover compared to 

other land covers, which limit nutrient 

sources more than in agricultural or 

forested areas. Furthermore, nutrient 

accumulation during winter may be 

limited by more frequent small runoff 

events resulting from sun-warmed 

impervious surfaces and application 

of road de-icers compared to other 

land uses. These small runoff peaks 

are evident at Shingle and Nine Mile 

Creeks (sites 13 and 16, respectively, 

fig. 5) in late February and early 

March (fig. 6) prior to the large snowmelt event. Furthermore, the largest 

annual streamflow peak occurred during summer in these streams whereas 

snowmelt produced the largest annual 

peaks in other streams, indicating that 

annual snowmelt peaks are reduced in 

urban basins, or that rainfall peaks are 

increased, or both. Agricultural 

streams transported 2–10 times more 

total nitrogen during snowmelt, in 

terms of percent of annual load, than 

streams in other land uses. Agricultural streams in the study unit have 

greater sources of nutrients available 

as a result of commercial fertilizer or 

livestock manure application (Kroening, 1998). Manure is often spread on 

snow covered or exposed fields that 

are vulnerable to erosion. Proportions 

of loads delivered during snowmelt at 

the forested site were intermediate 

between urban and agricultural sites, 

perhaps because forested basins have 

more nitrogen sources and winter 

accumulation than urban streams yet 

fewer nutrient sources or more vegetative cover to protect soils than agricultural basins.

At integrator sites, total nitrogen 

loads ranged from 641 to 99,000 tons 

in 1997 (table 2). Snowmelt loads 

ranged from 110 to 47,800 tons, 

accounting for 17 to 49 percent of the 

respective annual loads (table 2). 

Streams draining substantial amounts 

of agricultural land had the larger proportions; whereas, forested sites had 

smaller proportions.

?
)

Total phosphorus loads were not 

estimated for forested sites because 

many samples had concentrations 

below the method reporting limit. At 

indicator sites, total phosphorous 

loads ranged from 2.3 to 26 tons in 

1997 (table 2). Snowmelt loads 

ranged from 0.2–13 tons, composing 

4–48 percent of annual loads (table 2). 

Results were similar to those of total 

nitrogen. In urban streams, the proportion of annual loads from snowmelt was small—from 4 to 8 percent 

(table 2). These loads are slightly 

smaller, but comparable to those of 

Oberts (1982), who found that snowmelt contributed 8–20 percent of the 

annual phosphorus loads in small 

streams of the TCMA. Agricultural 

streams had the greatest proportions 

of loads delivered by snowmelt—

almost one-half of the annual load. 

Five to 12 times more of the annual 

total phosphorus load, in terms of percent of annual load, was delivered 

during snowmelt in agricultural 

streams than in urban streams. 

Annual loads at mainstem integrator sites ranged from 1,060 to 

5,170 tons (table 2). Snowmelt loads 

ranged from 381 to 2,530 tons, composing 36–54 percent of annual loads 

(table 2). Results were similar to 

those of total nitrogen. Although estimates of phosphorus loads were not 

made for forested sites, it is apparent 

from the magnitude of total phosphorus concentrations and streamflow 
14

that annual loads would have been 

less than those of other sites. 

	


At indicator sites, annual loads of 

suspended sediment ranged from 567 

to 13,900 tons in 1997 (table 2). 

Snowmelt loads ranged from 65 to 

6,020 tons, composing 1–43 percent 

of the annual loads (table 2). Like 

nutrients, proportions of sediment 

flushed during the snowmelt period 

were least at urban sites and greatest 

at agricultural sites.

At integrator sites, annual loads 

ranged from 8,820 tons to 2.65 million tons (table 2). Snowmelt loads 

ranged from 2,070 tons to 1.28 million tons, accounting for 23 to 70 percent of annual loads (table 2). The 

proportion of suspended sediment 

delivered during snowmelt was greatest at one of the forested sites (St. 

Croix River near St. Croix Falls, Wisconsin, site 30, fig. 5).

These results indicate that during 

1997, proportionately more of the 

annual loads of nutrients and suspended sediment at agricultural and 

forested streams were delivered during the snowmelt period than during 

other periods. At some sites, the 

snowmelt period delivered the majority of the annual load. Accordingly, 

the snowmelt period should be considered in strategies aimed at reducing 

loads of these constituents to streams.

8.8.960609(

8.86.=9;6&

898.

'99998

Samples were collected from all 

sites during snowmelt runoff under 

increasing streamflow conditions 

when constituent concentrations were 

expected to be greatest. Nutrient 

analyses were unavailable for the Vermillion River near Empire, Minnesota. Instantaneous concentrations 

and yields for streams draining representative combinations of land use 

and surficial geology were determined 

to assess those combinations that contribute nutrient and suspended sediment during snowmelt.

	
&


		"	#


	
@



	
	

To test the assumption that 

streams sampled during rising streamflow conditions would have the greatest concentrations, additional samples 

were collected at fixed sites before 

and after increasing streamflow (fig. 

6). Eighty-seven percent of the concentrations of nutrients and suspended 

sediments were greatest in samples 

collected during increasing streamflow. This suggests that at sites where 

one sample was collected during 

increasing streamflow, concentrations are among the greatest that 

occurred there. 

Exceptions occurred at two agricultural streams (North Fork Crow 

River above Paynesville, Minnesota, 

and Little Cobb River near Beauford, 

Minnesota; sites 5 and 14, respectively, fig. 5) and a forested stream 

(St. Croix River near Danbury, Wisconsin; site 21, fig. 5). In these 

streams, concentrations of dissolved 

nitrate and total nitrogen (composed 

mostly of dissolved nitrate) were 

greatest during streamflow recession. Other analyses (Mitton and others, 1997, 1998, and 1999) of water 

from these sites indicate these streams 

commonly have high concentrations 

of nitrate during base flow. This may 

indicate a substantial ground-water 

contribution during the streamflow 

recession, perhaps related to the 

sandy, permeable soils of the North 

Fork Crow River Basin and shallow 

drain tiles in the Little Cobb River 

Basin. Suspended-sediment concentrations also were greatest during the 

recession in the Little Cobb River—

perhaps because the sample collected 

during increasing streamflow was collected early, before sediment concentrations had increased substantially. 

Finally, in samples from the St. Croix 

River near Danbury, Wisconsin, differences between concentrations of 

dissolved ammonia plus organic nitrogen collected during increasing 

streamflow and those collected during 

the recession were within the analytical variability of the method (Maloney and others, 1994; U.S. 

Geological Survey, 1999). 

$	
#	"	#




During increasing streamflow 

conditions of snowmelt runoff, total 

nitrogen concentrations ranged from 

0.52 to 7.70 mg/L. The median concentration was 2.02 mg/L. Concentrations generally were greater in the 

southern and western parts of the 

focused study area (fig. 7a), where 

basins have greater proportions of 

agricultural land use (fig. 5). 

Principal nitrogen forms were dissolved nitrate, dissolved organic 

nitrogen, or particulate nitrogen. Dissolved nitrate concentrations ranged 

from 0.1 to 6.0 mg/L and composed 

32–94 percent of total nitrogen. Dissolved nitrate was the principal nitrogen form in streams across most of 

the focused study area, it composed 

more than one-half of total nitrogen in 

all sampled agricultural streams in the 

southern and western parts of the 

focused study area. In contrast, nine 

forested streams of the Upper Mississippi and St. Croix Rivers contained 

dissolved organic nitrogen as the predominant nitrogen form, composing 

31–52 percent of total nitrogen. Concentrations ranged from 0.15 to 0.88 

mg/L. Particulate nitrogen was the 

most common form in four other 

streams in the St. Croix River Basin, 

with concentrations ranging from 0.1 

to 0.88 mg/L. 

Dissolved ammonia and nitrite 

nitrogen formed lesser amounts of 

total nitrogen. Dissolved ammonia 
15

45°

45°

44°

44°

46°

46°

47°

47°

95°

95°

96°

96°

97°

97°

94°

94°

93°

93°

92°

92°

91°

91°

Base from

U.S. Geological

Survey digital data

1:2,000,000, 1972,

1:100,000, 1990, Albers

Equal-Area Conic projection.

Standard parallels: 29°30' and

45°30', central meridian: -93°00'

Base from

U.S. Geological

Survey digital data

1:2,000,000, 1972,

1:100,000, 1990, Albers

Equal-Area Conic projection.

Standard parallels: 29°30' and

45°30', central meridian: -93°00'

0

0

25

25

50

50

75

75

Miles

Miles

0

0

25

25

50

50

75

75

Kilometers

Kilometers

Figure 7.--Instantaneous (a) concentrations and (b) yields of t at sites sampled during 1997

snowmelt runoff in part of the Upper Mississippi River Basin study unit.

otal nitrogen

MINNESOTA

MINNESOTA

WISCONSIN

WISCONSIN

D

D

D

D

D

D

D

D

D

D

D

D

D

D

D

D

D

D

D

D

D

D

D

D

D

D

D

D

D

D

D

D

D

D

D

D

D

D

D

D

D

D

D

D

D

D

D

D

D

D

D

D

D

D

D

D

D

D D

D

D

D

D

D

D D

D

D

D

D

D

D

D

D

D

D

D

D

D

D

D

D

D

D

(a)

(b)

Boundary of focused study area

Boundary of focused study area

EXPLANATION

D

D

D

D

D

D 0.52-0.88

1.04-1.49

1.58-2.3

2.8 -4.1

5.1 -7.7

Data not available

Concentration, in milligrams

per liter

D

D

D

D

D

D

EXPLANATION

4.9- 10.4

13.1- 20.8

23.3- 34.4

40.3- 83.2

124 -270

Data not available

Yield, in pounds per square

mile per day
16

concentrations ranged from less than 

0.15 to 0.92 mg/L (0.3–26 percent of 

total nitrogen concentrations). Dissolved nitrite concentrations ranged 

from less than 0.01 to 0.12 mg/L. No 

samples had concentrations of dissolved un-ionized ammonia, nitrite, 

nitrate, or nitrite plus nitrate, that 

exceeded state water-quality standards for aquatic health (Minnesota 

Pollution Control Agency, 1999, Wisconsin Department of Natural 

Resources, 1997, 1998, and 1999).

Instantaneous yields of total nitrogen ranged from 4.9 to 270 lb/mi2

/d, 

with a median of 24.8 lb/mi2/d. 

Yields generally were greatest for 

streams west of the Mississippi River 

(fig. 7b). However, the yield for one 

stream in the St. Croix River Basin, 

Crooked Creek near Hinckley, Minnesota (site 23, fig. 5), ranked in the 

upper quartile of total nitrogen yields 

(54 lb/mi2

/d).

)	"	#




Total phosphorus concentrations 

ranged from less than 0.03 to 0.57 

mg/L. The median concentration was 

0.18 mg/L. Like nitrogen, total phosphorus concentrations generally were 

greater in streams west of the Mississippi River (fig. 8a), where the greatest proportions of agricultural lands in 

the focused study area are located 

(fig. 5). 

Particulate phosphorus was the 

predominant form of phosphorus in 

more than one-half of the streams 

sampled, regardless of land use. Concentrations ranged from less than 0.01 

to 0.29 mg/L, composing 18–92 percent of total phosphorus. Dissolved 

phosphorus concentrations ranged 

from less 0.01 to 0.4 mg/L and composed 8–81 percent of total phosphorus. Dissolved phosphorus was the 

principal phosphorus form at 13 agricultural streams in the southern and 

western parts of the focused study 

area. At six of these sites, dissolved 

orthophosphate, a component of dissolved phosphorus, was the predominant form of total phosphorus. 

Dissolved orthophosphate concentrations ranged from less than 0.01 to 

0.36 mg/L.

Yields of total phosphorus ranged 

from less than 0.3 to 19.8 lb/mi2

/d, 

with a median of 2.4 lb/mi2/d. The 

greatest yields were found west of the 

Mississippi River (fig. 8b), although 

above-median yields also were found 

for forested streams of the Upper St. 

Croix River Basin.

	
	

"	#


Suspended-sediment concentrations ranged from 6.2 to 249 mg/L. 

The greatest concentrations occurred 

in streams west of the Mississippi 

River, although some streams in the 

Upper St. Croix River also had concentrations above the median of 56 

mg/L (fig. 9a). 

Fractions of fine-grained sediment and sand-sized suspended sediment were determined for 38 sites. 

Fine-grained sediment is commonly 

associated with water-quality degradation. The median percentage of 

fine-grained sediment was 31 percent; 

indicating most of the sediment transported was sand sized. However, the 

percentage of fine-grained sediment 

was highly variable, ranging from 16 

to 95 percent. 

Instantaneous yields of suspended 

sediment ranged from 35.3 to 

7,880 lb/mi2/d, with a median of 

619 lb/mi2

/d. In contrast to nutrient 

yields, many of the greatest sediment 

yields occurred for forested streams 

draining the Upper St. Croix River, as 

well as streams west of the Mississippi River (fig. 9b). Fine-grained 

suspended-sediment yields ranged 

from 25 to 3,100 lb/mi2/d. The distribution of sites containing the greatest 

yields of fine-grained suspended sediment was similar to that of suspended 

sediment. 

9&&9086&;.9.

&0.;96;6=6

=9;

Yields are important for identifying basins that are contributing the 

greatest mass of constituent per unit 

area. The greatest instantaneous 

yields of nutrients and suspended sediment during snowmelt runoff generally occurred for streams west of the 

Mississippi River that drain basins 

with intense agricultural land use. 

However, combinations of land use 

and surficial geology containing 

lesser amounts of agriculture also 

contribute substantial yields and favor 

the transport of certain forms of nitrogen and phosphorus.

/

Of the land uses in the focused 

study area, the forests and wetlands in 

the northern part are least disturbed by 

human activities. Streams draining 

these forested areas offer the best 

background conditions to compare to 

other sites, even though most represent different ecoregions (Northern 

Lakes and Forests, and North Central 

Hardwood Forests) than other land 

uses (North Central Hardwood Forests, Western Cornbelt Plains, and 

Driftless Area) (Omernik and Gallant, 

1988). Other differences also exist. 

Forested areas generally contain more 

lakes and wetlands than the southern 

part of the focused study area, 

because lakes and wetlands were less 

extensive or were drained in the 

southern part. The southern part of 

the focused study area generally has 

more topographical relief and agricultural land use. Because forested areas 

are relatively undisturbed, differences in water-quality constituents, 

such as nutrient and sediment yields, 

may be more sensitive to disturbances. 

During snowmelt, particulate 

nutrients were the principal nutrient 

forms in the 10 streams draining forested areas. Particulate- and dis-
17

Figure 8.--Instantaneous (a) concentrations and (b) yields of t at sites sampled during 1997

snowmelt runoff in part of the Upper Mississippi River Basin study unit.

otal phosphorus

D

D

D

D

D

D

D

D

D

D

D

D

D

D

D

D

D

D

D

D

D

D

D

D

D

D

D

D

D

D

D

D

D

D

D

D

D

D

D

D

D

D

D

D

D

D

D

D

D

D

D

D

D

D

D

D

D

D D

D

D

D

D

D

D D

D

D

D

D

D

D

D

D

D

D

D

D

D

D

D

D

D

D

45°

45°

44°

44°

46°

46°

47°

95°

95°

96°

96°

97°

97°

94°

94°

93°

93°

92°

92°

91°

91°

Base from

U.S. Geological

Survey digital data

1:2,000,000, 1972,

1:100,000, 1990, Albers

Equal-Area Conic projection.

Standard parallels: 29°30' and

45°30', central meridian: -93°00'

Base from

U.S. Geological

Survey digital data

1:2,000,000, 1972,

1:100,000, 1990, Albers

Equal-Area Conic projection.

Standard parallels: 29°30' and

45°30', central meridian: -93°00'

0

0

25

25

50

50

75

75

Miles

Miles

0

0

25

25

50

50

75

75

Kilometers

Kilometers

MINNESOTA

MINNESOTA

WISCONSIN

WISCONSIN

(a)

(b)

Boundary of focused study area

Boundary of focused study area

D

D

D

D

D

D

D

EXPLANATION

Concentration, in milligrams

per liter

Less than 0.03

0.03-0.09

0.11-0.16

0.18-0.22

0.27-0.36

0.40-0.57

Data not available

D

D

D

D

D

D

D

EXPLANATION

Yield, in pounds per square

mile per day

Less than 0.3

0.3 - 1.0

1.2 - 1.9

2.4 - 3.5

4.3 - 8.6

16.4 -19.8

Data not available
18

Figure 9.--Instantaneous (a) concentrations and (b) yields of s at sites sampled during 1997

snowmelt runoff in part of the Upper Mississippi River Basin study unit.

uspended sediment

D

D

D

D

D

D

D

D

D

D

D

D

D

D

D

D

D

D

D

D

D

D

D

D

D

D

D

D

D

D

D

D

D

D

D

D

D

D

D

D

D

D

D

D

D

D

D

D

D

D

D

D

D

D

D

D

D

D D

D

D

D

D

D

D D

D

D

D

D

D

D

D

D

D

D

D

D

D

D

D

D

D

D

45°

45°

44°

44°

46°

46°

47°

95°

95°

96°

96°

97°

97°

94°

94°

93°

93°

92°

92°

91°

91°

Base from

U.S. Geological

Survey digital data

1:2,000,000, 1972,

1:100,000, 1990, Albers

Equal-Area Conic projection.

Standard parallels: 29°30' and

45°30', central meridian: -93°00'

Base from

U.S. Geological

Survey digital data

1:2,000,000, 1972,

1:100,000, 1990, Albers

Equal-Area Conic projection.

Standard parallels: 29°30' and

45°30', central meridian: -93°00'

0

0

25

25

50

50

75

75

Miles

Miles

0

0

25

25

50

50

75

75

Kilometers

Kilometers

MINNESOTA

MINNESOTA

WISCONSIN

WISCONSIN

(a)

(b)

EXPLANATION

D

D

D

D

D 6.2- 14

19 - 43

50 - 81

95 -160

203 -249

Concentration, in milligrams

per liter

D

D

D

D

D

EXPLANATION

156 - 464

606 - 625

904 -1,510

1,840 -7,880

Yield, in pounds per square

mile per day

35.3- 69.3

Boundary of focused study area

Boundary of focused study area
19

solved organic nitrogen were the 

principal nitrogen forms at eight sites. 

Particulate phosphorus was the principal phosphorus form at all ten sites. 

Kroening and Andrews (1997) also 

found that total organic plus ammonia 

nitrogen, composed mostly of dissolved organic and particulate nitrogen, constituted more than 70 percent 

of the median annual loads of total 

nitrogen in rivers draining forested 

parts of the focused study area. 

Organic nitrogen and particulate 

phosphorus may be transported from 

naturally occurring organic material 

that has accumulated in forest soils 

and wetlands as a result of very slow 

nitrification and denitrification processes during low temperatures in the 

winter (Wetzel, 1983). In a study of 

forested streams, Likens and Borman 

(1995) found that most particulate 

matter was transported during runoff. 

In contrast, dissolved nitrate was 

the principal nitrogen form in all 13 

agriculture streams during snowmelt, 

and dissolved phosphorus was the 

predominant phosphorus form in 11 

streams. Kroening and Andrews 

(1997) also found that nitrate composed more than 80 percent of median 

total nitrogen loads annually in agricultural streams of the focused study 

area. The predominance of these 

nutrient forms in agricultural streams 

indicates these constituents likely 

result from agricultural practices and 

fertilizer application.

Agricultural streams had significantly greater median yields (p < 

0.025) of nutrients (dissolved nitrite, 

nitrate, phosphorus, orthophosphate, 

and total nitrogen and total phosphorus) than forested streams. The comparison for dissolved nitrate is shown 

in fig. 10. Agricultural streams also 

had significantly greater median 

yields (p < 0.025) of dissolved nitrate 

and orthophosphate than streams 

draining other land uses. Median 

yields of other nitrogen forms, including dissolved and total ammonia plus 

organic nitrogen and particulate nitrogen, were greater at agricultural sites 

than forested, but not significantly (p 

> 0.025). This suggests that naturally 

occurring organic material in forests 

and wetlands contribute loads of particulate and organic nitrogen comparable to agricultural areas. 

Suspended-sediment and finegrained sediment yields were similar 

for agricultural and forested streams. 

This suggests that forested basins are 

as vulnerable to erosion as agricultural streams during snowmelt even 

though agricultural areas generally 

have more exposed soil, or that other 

factors, such as surficial geology, 

have a greater effect than land use on 

sediment yield. In any land use, substantial sediment load may originate 

from bank erosion and instream 

sources, which greater streamflow 

may resuspend. Payne (1994) attributed suspended sediment gains in 

selected stream reaches of the Minnesota River Basin during snowmelt to 

scouring of previously deposited sediment and bank and bed erosion, considering the lack of substantial 

inflows between sampling points. 

Median yields of nutrients and 

suspended sediment for urban streams 

were significantly less (p < 0.025) 

than agricultural streams, generally 

less than mixed land use streams, and 

similar to forested streams. The comparisons for dissolved phosphorus are 

shown in fig. 10. Urban land cover 

75th Percentile

90th Percentile

Number of samples

Median

25th Percentile

10th Percentile

EXPLANATION

Outside points

0

16

2

4

6

8

10

12

14

Forested Agricultural Agricultural

YIELD, IN POUNDS PER SQUARE MILE PER DAY

YIELD, IN POUNDS PER SQUARE MILE PER DAY

Urban Urban Mixed Mixed Forested 0

200

20

40

60

80

100

120

140

160

180

Figure 10.--Instananeous yields of (a) dissolved nitrate nitrogen and (b) dissolved phosphorus for streams draining forested,

urban, and mixed land uses and land covers, during 1997 snowmelt runoff

in part of the Upper Mississippi River Basin Study unit.

agricultural,

13 13

14

14

10

10 5

5

5

(a) (b)
20

generally has less nutrient and suspended sediment sources than agricultural and forested areas during 

snowmelt. Natural sources of organic 

nutrients and particulate matter such 

as wetlands are often drained or filled 

and vegetative mass is reduced. 

Urban areas have lower application 

rates of nutrients, and less exposed 

soil subject to erosion, than agricultural areas. Also, urban areas tend 

have more frequent and smaller snowmelt runoff events than other land 

covers because of application of deicers and warmer temperatures resulting from the thermal heat sink of an 

urban area, as evident at Shingle and 

Nine Mile Creeks (fig. 6). The 

greater frequency of winter runoff 

events in urban streams also may limit 

nutrient accumulation. Consequently, although urbanization has 

been cited as a cause of increased 

nutrient yields (Wetzel, 1983), in this 

study nutrient yields from urban areas 

without WWTPs were not significantly greater than forested areas during snowmelt runoff. However, 

annual yields of total nitrogen and 

suspended sediment for urban streams 

were greater than forested streams 

(table 2). Urban sources of nutrients 

and sediment may be more substantial 

during other seasons when fertilizer 

application, leaf litter, storm runoff, 

and storm sewer drainage activities 

increase. Consequently, limiting nutrients and suspended sediment during 

the growing season may be more 

effective than during snowmelt.

		#


Significant differences (p < 0.05) 

in water quality were observed among 

streams draining permeable and 

impermeable deposits in forested 

areas. Median yields of total nitrogen 

and total phosphorus were greater for 

forested streams draining mostly 

impermeable deposits than for mostly 

permeable deposits (fig. 11). Median 

yields of suspended sediment and 

every nitrogen and phosphorus form 

analyzed also were significantly 

greater (p < 0.05) for streams draining 

impermeable deposits. Median yields 

were greater in basins draining impermeable deposits, probably because 

soils in these basins are more vulnerable to erosion (U.S. Department of 

Agriculture, 1978 and 1979) and 

water-quality degradation, and contribute greater yields to downstream 

lakes and rivers, especially during 

runoff. While percentages of agricultural land in basins draining mostly 

permeable or mostly impermeable 

deposits could be a contributing factor, differences in the amounts of agricultural land were not statistically 

significant (p > 0.05). In forested 

areas, the type of surficial geology 

may be important to consider in strategies to reduce loads during snowmelt 

runoff.

In streams draining mixed land 

use, yields of dissolved nitrite and 

total nitrogen were significantly 

greater (p < 0.05) in streams draining 

impermeable deposits than streams 

draining permeable deposits. These 

differences may be due to variable 

amounts of agricultural land use in 

these basins.

75th Percentile

90th Percentile

Number of samples

Median

25th Percentile

10th Percentile

EXPLANATION

YIELD, IN POUNDS PER SQUARE MILE PER DAY

YIELD, IN POUNDS PER SQUARE MILE PER DAY

Permeable

deposits

Impermeable

deposits

Permeable

deposits

Impermeable

deposits

0

6.0

1.0

2.0

3.0

4.0

5.0

Figure 11.--Instananeous yields of (a) total nitrogen and (b) total phosphorus in permeable and impermeable deposits

for streams draining forested basins, during 1997 snowmelt runoff

in part of the Upper Mississippi River Basin Study unit.

0

60

10

20

30

40

50

4

4

6 6

6

(a) (b)
21

.=

The USGS sampled snowmelt runoff from 42 stream 

sites in part of the Upper Mississippi River Basin, Minnesota and Wisconsin, to characterize nutrient and suspendedsediment concentrations, yields, and loads. Streams sampled drained combinations of land use and surficial geology 

common in the focused study area of the Upper Mississippi 

River Basin NAWQA study unit. Streams were classified 

by the predominant land use (forested, agricultural, urban, 

or mixed) and the predominant type of surficial geologic 

deposit (permeable or impermeable). Drainage areas 

ranged from 10 to 46,800 mi2

. Streams were sampled during March and April 1997, when melting of the snowpack 

combined with rainfall to produce near-record streamflow. 

Samples were collected during increasing streamflow conditions when concentrations were greatest. Ancillary data 

from 12 sites provided comparative concentrations from 

before and after streamflow increases and provided data to 

estimate constituent loads delivered during snowmelt and 

1997. 

The snowmelt period contributed from 1 to 50 percent 

of 1997 annual loads of total nitrogen, total phosphorus, 

and suspended sediment at small stream sites, and 17–70 

percent of annual loads at mainstem river sites. Small 

streams draining agricultural areas transported the greatest 

proportions of annual loads during snowmelt. Agricultural 

areas have greater sources of nitrogen, phosphorus, and 

suspended sediment available as a result of commercial fertilizer or livestock manure application. Manure is often 

spread on snow-covered or exposed soils that are vulnerable to erosion. Snowmelt from urban streams transported 

the least proportions of annual loads. Impervious surfaces 

in urban areas reduce vegetation and soil cover, which limit 

nutrient and suspended-sediment sources. Furthermore, 

nutrient accumulation during winter may be limited by 

more frequent small runoff events resulting from sunwarmed impervious surfaces and application of road deicers. Proportions of the annual loads of total nitrogen and 

suspended sediment from snowmelt at the forested site 

were between urban and agricultural sites. Forested basins 

may have more nutrient and sediment sources and winter 

accumulation than urban streams, yet less sources or more 

vegetative cover to protect soils than agricultural basins. 

In snowmelt runoff samples, total nitrogen, total phosphorus, and suspended sediment concentrations and instantaneous yields were greatest for streams draining 

agricultural areas, especially those west of the Mississippi 

River. Dissolved nitrate was the principal nitrogen form for 

all agricultural streams, likely the result agricultural practices and fertilizer application. Dissolved organic nitrogen 

and particulate nitrogen were the principal nitrogen forms 

for forested streams, as these constituents are transported 

from naturally occurring organic material that has accumulated in forest soils and wetlands. No nitrogen concentrations (including dissolved un-ioinized ammonia, nitrite, 

nitrate, or nitrite plus nitrate) exceeded applicable Minnesota or Wisconsin water-quality standards for human or 

aquatic health. Dissolved phosphorus, mostly orthophosphate, was the principal phosphorus form for agricultural 

streams. 

Median instantaneous yields of nutrients for agricultural streams were greater than for streams draining other 

land uses. Agricultural streams had significantly greater 

median yields (p < 0.025) of dissolved nitrite, nitrate, phosphorus, orthophosphate, total nitrogen, and total phosphorus than forested sites, and significantly greater median 

yields (p < 0.025) of dissolved nitrate and orthophosphate 

than all other land uses. Suspended-sediment and finegrained sediment yields were similar for agricultural and 

forested streams, suggesting that forested basins are as vulnerable to erosion as agricultural streams during snowmelt.

In forested areas, yields of suspended sediment and all 

nutrient forms were significantly greater (p < 0.05) for 

streams draining impermeable deposits than permeable 

deposits. Soils developed on impermeable deposits in 

these basins are more vulnerable to erosion and water-quality degradation, and contribute greater yields to downstream lakes and rivers, especially during runoff.

In agricultural and forested streams, the snowmelt 

period can deliver greater proportions of annual loads of 

nutrients and suspended sediment than other equivalent 

periods, and occasionally, the majority of the annual load. 

Consequently, the snowmelt period should be considered in 

strategies aimed at reducing loads of nutrients and suspended sediment to streams. For forested areas, the type of 

surficial geology may be important to consider in strategies 

to reduce loads during snowmelt runoff. For urban areas, 

limiting nutrients and suspended sediment during the growing season runoff may be more effective than during snowmelt.
22

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