Water-Quality Assessment of Lakes Maumelle and 

Winona, Arkansas, 1991 Through 2003

Prepared in cooperation with

CENTRAL ARKANSAS WATER

U.S. Department of the Interior

U.S. Geological Survey

Scientific Investigations Report 2004-5182
Front Cover: View of Lake Maumelle from the summit of Pinnacle Mountain. Photograph

provided by Richard Ates, Pinnacle Mountain State Park.
Water-Quality Assessment of Lakes 

Maumelle and Winona, Arkansas, 1991 

Through 2003

By Joel M. Galloway and W. Reed Green

U.S. Department of the Interior

U.S. Geological Survey

Prepared in cooperation with

CENTRAL ARKANSAS WATER

Scientific Investigations Report 2004-5182
Contents

 iii

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

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

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

Study Area Description....................................................................................................................................................................2

Previous Investigations....................................................................................................................................................................2

Methods .........................................................................................................................................................................................................5

Streamflow and Lake Volume .........................................................................................................................................................5

Lake Sampling ...................................................................................................................................................................................5

Inflow Sampling.................................................................................................................................................................................6

Data Analysis .....................................................................................................................................................................................6

Trophic State Indices........................................................................................................................................................................6

Loads and Yields................................................................................................................................................................................7

Flow-Weighted Concentrations......................................................................................................................................................7

Water-Quality Assessment.........................................................................................................................................................................7

Hydrologic Conditions ......................................................................................................................................................................7

Lake Maumelle.......................................................................................................................................................................7

Lake Winona...........................................................................................................................................................................9

Lake Water Quality.......................................................................................................................................................................... 10

Lake Maumelle..................................................................................................................................................................... 10

Temperature .............................................................................................................................................................. 10

Dissolved-Oxygen Concentrations ........................................................................................................................ 10

Nutrient and Organic Carbon Concentrations..................................................................................................... 13

Chlorophyll a Concentrations ................................................................................................................................. 17

Water Clarity.............................................................................................................................................................. 18

Trophic Status ........................................................................................................................................................... 19

Lake Winona......................................................................................................................................................................... 20

Temperature .............................................................................................................................................................. 20

Dissolved-Oxygen Concentrations ........................................................................................................................ 20

Nutrient and Organic Carbon Concentrations..................................................................................................... 20

Chlorophyll a Concentrations ................................................................................................................................. 20

Water Clarity.............................................................................................................................................................. 28

Trophic Status ........................................................................................................................................................... 29

Inflow Water Quality....................................................................................................................................................................... 30

Lake Maumelle..................................................................................................................................................................... 30

Constituent Concentrations .................................................................................................................................... 30

Loads and Yields of Nutrients, Dissolved Organic Carbon, and Suspended Sediment................................ 32

Flow-Weighted Concentrations of Nutrients, Dissolved Organic Carbon, and Suspended Sediment ...... 36

Lake Winona......................................................................................................................................................................... 36

Constituent Concentrations .................................................................................................................................... 38

Loads and Yields of Nutrients, Dissolved Organic Carbon, and Suspended Sediment................................ 39

Flow-Weighted Concentrations of Nutrients, Dissolved Organic Carbon, and Suspended Sediment ...... 43

Summary ...................................................................................................................................................................................................... 44

References .................................................................................................................................................................................................. 45
iv 

Figures

1. Map showing location of Lakes Maumelle and Winona....................................................................................................... 3

2. Map showing land use in the Lakes Maumelle and Winona watersheds ......................................................................... 4

3-10. Graphs showing:

3. Daily, monthly, and annual mean streamflow and water-quality sampling times for the Maumelle River at Williams 

Junction, Arkansas, 1991 through 2003 ............................................................................................................................... 8

4. Flow accumulation curve for the Maumelle River at Williams Junction, Arkansas, 1991 through 2003 .................. 8

5. Daily mean reservoir volumes for Lake Maumelle from stage recorded at Lake Maumelle at Natural Steps,

Arkansas (07263300), 1991 through 2003.............................................................................................................................. 9

6. Daily, monthly, and annual mean streamflow and water-quality sampling times for the Alum Fork Saline River near 

Reform, Arkansas, 1991 through 2003 .................................................................................................................................. 9

7. Flow accumulation curve for the Alum Fork Saline River near Reform, Arkansas, 1991 through 2003................... 10

8. Daily mean reservoir volumes for Lake Winona from stage recorded at Lake Winona dam at Reform

(07362591), 1991 through 2003.............................................................................................................................................. 10

9. Distribution of temperature with depth and time in Lake Maumelle near Natural Steps, Arkansas....................... 11

10. Distribution of dissolved oxygen concentration with depth and time in Lake Maumelle

near Natural Steps, Arkansas ............................................................................................................................................. 12

11. Boxplot showing distribution of nutrient concentrations for four sites on Lake Maumelle, Arkansas....................... 13

12. Graphs showing time series of nitrogen concentrations for three sites on Lake Maumelle, Arkansas,

1991 through 2003....................................................................................................................................................................... 14

13. Graphs showing time series of phosphorus concentrations for three sites on Lake Maumelle, Arkansas,

1991 through 2003....................................................................................................................................................................... 15

14. Boxplot showing distribution of organic carbon concentrations for four sites on Lake Maumelle, Arkansas ......... 16

15. Graphs showing time series of organic carbon concentrations for three sites on Lake Maumelle, Arkansas, 1991 

through 2003................................................................................................................................................................................ 16

16. Boxplot showing distribution of chlorophyll a concentrations for four sites on Lake Maumelle, Arkansas.............. 17

17. Graphs showing time series of chlorophyll a concentrations for three sites on Lake Maumelle, Arkansas,

1991 through 2003....................................................................................................................................................................... 17

18. Graph showing median monthly chlorophyll a concentrations for Lake Maumelle near Natural Steps,

Arkansas, 1991 through 2003.................................................................................................................................................... 17

19. Boxplot showing distribution of Secchi depths for four sites on Lake Maumelle, Arkansas ....................................... 18

20. Graph showing median monthly Secchi depths for Lake Maumelle near Natural Steps, Arkansas,

1991 through 2003....................................................................................................................................................................... 18

21. Graphs showing time series of Secchi depth for three sites on Lake Maumelle, Arkansas,

1991 through 2003....................................................................................................................................................................... 18

22. Boxplot showing trophic state indices for three sites on Lake Maumelle, Arkansas,

1991 through 2003....................................................................................................................................................................... 19

23. Graphs showing distribution of temperature with depth and time in Lake Winona at Reform, Arkansas.................. 21

24. Graphs showing distribution of dissolved oxygen concentration with depth and time in Lake Winona at

Reform, Arkansas....................................................................................................................................................................... 22

25. Boxplots showing distribution of nutrient concentrations for three sites on Lake Winona, Arkansas....................... 23

26. Graphs showing time series of nitrogen concentrations for three sites on Lake Winona, Arkansas......................... 24

27. Graphs showing time series of phosphorus concentrations for three sites on Lake Winona, Arkansas................... 25

28. Boxplots showing distribution of organic carbon concentrations for three sites on Lake Winona, Arkansas ......... 26

29. Graphs showing time series of organic carbon concentrations for three sites on Lake Winona, Arkansas ............ 26

30. Boxplot showing distribution of chlorophyll a concentrations for three sites on Lake Winona, Arkansas ............... 27

31. Graphs showing time series of chlorophyll a concentrations for three sites on Lake Winona, Arkansas................. 27

32. Graph showing median monthly chlorophyll a concentrations for Lake Winona at Reform, Arkansas,

1991 through 2003....................................................................................................................................................................... 27

33. Boxplot showing distribution of Secchi depths for three sites on Lake Winona, Arkansas ......................................... 28

34. Graph showing median monthly Secchi depths for Lake Winona at Reform, Arkansas, 1991 through 2003 ............. 28

35. Graphs showing time series of Secchi depth for three sites on Lake Winona, Arkansas ............................................ 28

36. Boxplots showing trophic state indices for three sites on Lake Winona, Arkansas...................................................... 29
v

37. Boxplots showing distribution of nutrient, dissolved organic carbon, and suspended-sediment concentrations

for four inflow sites to Lake Maumelle....................................................................................................................................30

38. Graphs showing time series of nutrient, dissolved organic carbon, and suspended-sediment concentrations

for the Maumelle River at Williams Junction, Arkansas, 1991 through 2003....................................................................31

39. Boxplot showing distribution of fecal indicator bacteria concentrations for four inflow sites to Lake Maumelle ...32

40-43. Graphs showing:

40. Graphs showing annual nutrient, dissolved organic carbon, and suspended-sediment loads estimated for the

Maumelle River at Williams Junction, Arkansas, 1991 through 2003 ..........................................................................33

41.Graphs showing seasonal nutrient, dissolved organic carbon, and suspended-sediment loads estimated for

the Maumelle River at Williams Junction, Arkansas, 1991 through 2003 ...................................................................35

42. Graphs showing annual nutrient yields for the Maumelle River at Williams Junction, Arkansas, Alum Fork

Saline River near Reform, Arkansas, and selected other stream basins ...................................................................36

43. Graphs showing annual flow-weighted nutrient concentrations for the Maumelle River at Williams Junction,

Arkansas, Alum Fork Saline River near Reform, Arkansas, and selected other stream basins .............................37

44. Boxplots showing distribution of nutrient, dissolved organic carbon, suspended-sediment, and fecal indicator

bacteria concentrations for the Alum Fork Saline River near Reform, Arkansas, 1991 through 2003..........................38

45. Graphs showing time series of nitrogen, phosphorus, dissolved organic carbon, and suspended-sediment 

concentrations for the Alum Fork Saline River near Reform, Arkansas, 1991 through 2003..........................................39

46. Graphs showing annual nutrient, dissolved organic carbon, and suspended-sediment loads estimated for the

Alum Fork Saline River near Reform, Arkansas, 1991 through 2003...................................................................................41

47. Graphs showing seasonal nutrient, dissolved organic carbon, and suspended-sediment loads estimated for

the Alum Fork Saline River, Arkansas, 1991 through 2003 ...................................................................................................42

Tables

1. Water-quality and streamflow sites for Lakes Maumelle and Winona ...............................................................................5

2. Estimated annual loads and yields for the Maumelle River at Williams Junction, Arkansas,

1991 through 2003....................................................................................................................................................................34

3. Annual flow-weighted concentrations computed for the Maumelle River at Williams Junction, Arkansas,

1991 through 2003....................................................................................................................................................................37

4. Estimated annual loads and yields for the Alum Fork Saline River near Reform, Arkansas, 1991 through 2003........40

5. Annual flow-weighted concentrations computed for the Alum Fork Saline River near Reform, Arkansas,

1991 through 2003....................................................................................................................................................................43
vi 

Conversion Factors and Datum and Abbreviations

Multiply By To obtain

Length

centimeter (cm) 0.3937 inch (in.)

meter (m) 3.281 foot (ft)

kilometer (km) 0.6214 mile (mi) 

Area

square kilometer (km2) 0.3861 square mile (mi2)

Volume

cubic meter (m3) 35.31 cubic foot (ft3) 

Flow rate

cubic meter per second (m3/s) 35.31 cubic foot per second (ft3/s)

Mass

kilogram (kg) 2.205 pound avoirdupois (lb)

kilogram per year (kg/yr) 2.205 pound per year (lb/yr)

Degrees Celsius (° C) may be converted to degree Fahrenheit (° F) by using the following equation:

° F = 1.8(° C) + 32

In this report vertical coordinate information is referenced to the National Geodetic Vertical datum of 1929 (NGVD of 1929). 

Horizontal coordinate information is referenced to North American Datum of 1983 (NAD 83).

Constituent concentrations in water are in milligrams per liter (mg/L), micrograms per liter (μg/L), and colonies per 100 

milliliters

mg/L, milligrams per liter

μg/L, micrograms per liter

mL, milliliters
Water-Quality Assessment of Lakes Maumelle and 

Winona, Arkansas, 1991 Through 2003

By Joel M. Galloway and W. Reed Green

Abstract

Lakes Maumelle and Winona are water-supply reservoirs 

for the Little Rock and North Little Rock metropolitan areas in 

central Arkansas. In addition to water supply, the reservoirs are 

used for recreation and fish and wildlife habitat. The purpose of 

this report is to describe the hydrology and water quality of 

Lakes Maumelle and Winona and their inflows from data collected by the U.S. Geological Survey in cooperation with Central Arkansas Water for calendar years 1991 through 2003.

The main inflows into Lakes Maumelle and Winona, the 

Maumelle River and Alum Fork Saline River, exhibited typical 

seasonal variability in streamflow with high flows usually 

occurring in the late fall, winter, and early spring, and low or no 

flow in the summer and early fall. The highest annual mean 

streamflow occurred in 1991 and the lowest annual mean 

streamflow occurred in 1992 for the Maumelle River and 1995 

for the Alum Fork Saline River. 

Water quality measured in Lakes Maumelle and Winona 

varied spatially and temporally. Although total phosphorus concentrations were substantially higher at the upper ends of the 

lakes than at the lower ends of the lakes, nitrogen and orthophosphorus concentrations were not significantly different 

among the sampling sites on each lake. The highest concentrations of nitrogen generally were measured in 1991 and from 

1998 through 2003 at all of the sampling sites. The highest total 

phosphorus concentrations were measured from 1994 to 1996 

and from 1998 to 2001 on Lake Maumelle and from 1993 to 

1994 on Lake Winona. Total and dissolved organic carbon concentrations were similar among sites on each lake and the greatest concentrations were measured in 1996 and 1997 at all of the 

sites. The chlorophyll a concentrations varied seasonally, with 

the highest concentrations in October and November, but were 

relatively uniform spatially and annually in Lakes Maumelle 

and Winona for 1991 through 2003. Water clarity was greater at 

the lower ends of the lakes than at the upper ends. Secchi depth 

varied seasonally, with the greatest depth from July to September and the least depth during October through December. 

There was no apparent trend in Secchi depth over the entire 

sampling period. 

The trophic state indices calculated from near-surface concentrations of total phosphorus and chlorophyll a for Lakes 

Maumelle and Winona indicated that they generally were oligotrophic although they fluctuated in time between mesotrophic 

and oligotrophic conditions. 

Water-quality concentrations generally were less for the 

main inflow to Lake Winona, the Alum Fork Saline River, than 

for the Maumelle River, Bringle, Yount, and Reece Creeks, 

which flow into Lake Maumelle. Nutrient concentrations for the 

Maumelle and Alum Fork Saline Rivers remained fairly uniform from 1991 through 2003. Suspended-sediment concentrations generally were greatest at Bringle Creek. Concentrations 

of fecal streptococci measured at the Alum Fork Saline River 

were similar to concentrations measured at the Maumelle River, 

and fecal coliforms concentrations for the Alum Fork Saline 

River were approximately half the concentration measured at 

the Maumelle River. Bringle and Reece Creeks had greater concentrations of fecal coliforms and fecal streptococci than the 

Maumelle River, and Yount Creek had the lowest concentration 

of fecal streptococci among all the sites.

Annual loads of nutrients, dissolved organic carbon, and 

suspended sediment estimated for the Maumelle River and the 

Alum Fork Saline River were similar between sites and varied 

with time from 1991 through 2003. Annual loads were greatest 

in 1991 for the Maumelle and Alum Fork Saline Rivers and the 

least in 2000 for the Maumelle River and 1995 for the Alum 

Fork Saline River. Estimated loads also demonstrated seasonal 

trends with the highest daily loads in the winter and fall and 

lowest daily loads in the summer for both sites.

Annual yields of nutrients and dissolved organic carbon 

computed for the Maumelle River were similar to yields for the 

Alum Fork Saline River and suspended-sediment yields were 

less for the period of 1991 through 2003. The Alum Fork Saline 

River had a mean total nitrogen yield that was slightly greater 

than the mean total nitrogen yield for Maumelle River and more 

than three times greater than yields for selected undeveloped 

sites across the Nation. 

Annual flow-weighted concentrations of nutrients and dissolved organic carbon for the Alum Fork Saline River generally 

were similar to those computed for the Maumelle River. Suspended-sediment flow-weighted concentrations for the Alum 

Fork Saline River were approximately one-half those computed 
2 Water-Quality Assessment of Lakes Maumelle and Winona, Arkansas, 1991 Through 2003

for the Maumelle River. The Alum Fork Saline River generally 

had flow-weighted nutrient concentrations similar to the mean 

flow-weighted concentrations for selected undeveloped basins 

across the Nation.

Introduction

Lakes Maumelle and Winona are water-supply reservoirs 

for the Little Rock and North Little Rock metropolitan areas in 

central Arkansas. In addition to water supply, the reservoirs are 

used for recreation and fish and wildlife habitat. As the urban 

and agricultural development of the basins has increased in the 

last 20 years, concerns about the sustainability of the quality of 

the water supply also have increased. Monitoring changes in the 

hydrology and water quality of the basin as the land use changes 

is critical to managing the resource. 

A long-term water-quality database is important to accurately assess present water-quality conditions, trends, and sensitivity to change. Hydrologic and water-quality data have been 

collected on Lakes Maumelle and Winona and their inflows 

from 1991 through 2003 by the U.S. Geological Survey (USGS) 

in cooperation with Central Arkansas Water (CAW), the utility 

that owns and operates the two water-supply reservoirs. 

Purpose and Scope

The purpose of this report is to describe the hydrology and 

water quality of Lakes Maumelle and Winona and their inflows 

from calendar years 1991 through 2003. Samples were collected at four locations in Lake Maumelle and at three locations 

in Lake Winona. Samples also were collected at four inflow 

sites to Lake Maumelle and one inflow site to Lake Winona. 

Water samples were analyzed for several field parameters and 

constituents, including specific conductance, pH, water temperature, dissolved oxygen, nutrients, organic carbon, suspended 

sediment, chlorophyll a, Secchi depth, and fecal indicator bacteria. Annual and seasonal loads of nutrients, dissolved organic 

carbon, and suspended sediment were estimated for the main 

inflows into Lakes Maumelle and Winona, the Maumelle River 

at Williams Junction, Arkansas (Lake Maumelle), and the Alum 

Fork Saline River near Reform, Arkansas (Lake Winona). 

Yields and flow-weighted concentrations were calculated from 

estimated annual loads and compared with selected sites representing undeveloped basins across the Nation and one site representing a developed basin in Arkansas.

Study Area Description

Lakes Maumelle and Winona are located in central Arkansas, west of the city of Little Rock (fig. 1). Construction of Lake 

Maumelle on the Maumelle River was completed in 1956 

(Green, 2001). Lake Maumelle contains 2.70 x 108

 m3 of water 

at the spillway elevation (88.4 m above NGVD of 1929) and has 

2.31 x 108

 m3 of usable water (Green, 2001). The surface area 

of Lake Maumelle at the spillway elevation is approximately 36 

km2, the maximum length of the reservoir is 19 km, and maximum depth is 14 m with an average depth of 7.5 m. The reservoir has a drainage area of 355 km2 at the dam. The Lake 

Maumelle watershed consists mainly of forested land (91 percent, not including the reservoir area) and pasture (8 percent, 

not including the reservoir area). The land use for the Maumelle 

River watershed upstream from the reservoir is approximately 

98 percent forested land (fig. 2). 

Construction of Lake Winona on the Alum Fork Saline 

River was completed in 1938 (Green, 1994). Lake Winona contains 5.10 x 107 m3 at the spillway elevation (225.6 m above 

NGVD of 1929) with 4.69 x 107

 m3 of usable water (Green, 

1994). The surface area of Lake Winona at the spillway elevation is 4.1 km2

. The maximum length of Lake Winona is 7.2 km, 

with a maximum depth of 30 m and an average depth of 10.6 m. 

Lake Winona has a drainage area of 115 km2

 that is mainly forested land (94 percent, not including the reservoir area) (fig. 2). 

The Alum Fork Saline River above the reservoir has a watershed consisting of nearly 100 percent forested land. 

Previous Investigations

USGS and CAW have collected reservoir elevation, 

streamflow, and water-quality data for Lakes Maumelle and 

Winona and the main inflows, the Maumelle River and Alum 

Fork Saline River, respectively, since 1989 as part of an ongoing monitoring program. Data are stored in the USGS National 

Water Information System database and published annually 

(Moore and others, 1992; Porter and others, 1993; Westerfield 

and others, 1994; Evans and others, 1995; Porter and others, 

1996; 1997; 1998; 1999; 2000; 2001; 2002; Brossett and Evans, 

2003; Evans and others, 2004). Hydrologic data collected in 

Lakes Maumelle and Winona from May 1989 to October 1992 

(Green and Louthian, 1993) were used to assess water quality 

(Green, 1994). Green (1994) concluded that the water quality of 

Lakes Maumelle and Winona and the Maumelle River and 

Alum Fork Saline River are more pristine than other reservoirs 

and streams in the region. Green (2001) concluded that nutrient 

concentrations in Lake Maumelle and the Maumelle River were 

one to two orders of magnitude lower than estimates of national 

background nutrient concentrations. 

Green (2001) developed and calibrated a hydrodynamic 

and water-quality model of Lake Maumelle to simulate the temperature, dissolved oxygen, nutrient, and algal biomass dynamics in the reservoir from 1991 to 1992. The model also was used 

to evaluate reservoir response to a spill of a conservative material at the upper end of Lake Maumelle. The model simulated 

the release of a nearby nursery pond into a tributary of Lake 

Maumelle (Green, 2001). Simulation results showed elevated 

concentrations of some nutrients, organic carbon, iron, and 

manganese during simulated releases in 1991 through 1994 and 

1996 (Green, 1998). In addition, model simulations of the algal 

response to increases of nitrogen and phosphorus loads demon-
Figure 1. Location of Lakes Maumelle and Winona.

SALINE

COUNTY PULASKI

COUNTY

Little R

07362587

07362588 07362589

07362590

07362591

LakeMaumelle

Lake

Winona

PERRY

COUNTY

10

9

9

5 30

4

10

Maumelle

River

Arkansas

River

North

For k

Saline

Riv er

Alum

For k

Saline River

BringleCreek Reece Creek

Saline

River

Middle Fork

Little Maumelle River Paron Reform

Wye

Little

Italy

Na

St

Crossroads

Williams

Junction

Martindale

07263295

072632962

072632982

072632965

07263297

072632971

07263299

072632995

072

YountCreek

34°48'

34°36'

93° 92°30'

Base from U.S. GeologicalSurvey 1:100,000 digital data

0 2.5 

0 

07263295 07263299

07362591

07263300

07263300

EXPLANATIONSTREAMFLOW AND WATER-QUALITY MEASUREMENT SITEWATER-QUALITY MEASUREMENT SITESTAGE MEASUREMENT SITESTREAMFLOW MEASUREMENTSITE IDENTIFIER
Figure 2. Land use in the Lakes Maumelle and Winona watersheds.

SALINE

COUNTY

GARLAND

COUNTY

PULAS

COUN

Lake

Maumelle

Lake

Winona

PERRY

COUNTY

10

9

9

5

30

10

Maumelle

River

Arkansas

River

North

Fo r k

Saline

River

Alum

For k

Saline

River

Bringle

Creek

Reece Creek

Saline

River

Middle Fork

Little Maumelle

River

Williams

Junction

Natural

Steps

Paron Reform

Little

Wye Italy

Yount

Creek

93° 92°30'

34°48'34°36'

Base from U.S. GeologicalSurvey 1:100,000 digital dataLand cover from Vogelmannand others (2001)

EXPLANATION

URBAN AGRICULTURE

BARREN PASTUREFOREST DRAINAGE BASIN BOUNDARY
Methods 5

strated phosphorus limited conditions in Lake Maumelle 

(Green, 2001).

Pomes and others (1997; 1999) evaluated the sources of 

disinfection byproduct precursors in Lakes Maumelle and 

Winona. Aquatic humic substances in water that generate 

potentially harmful disinfection byproducts and dissolved 

organic carbon concentrations were found to be higher in Lake 

Winona than in Lake Maumelle and likely originate from deciduous leaf litter, twigs, and grass leachates (Pomes and others, 

1997; 1999).

Methods

Streamflow and Lake Volume

Stream stage was measured continuously at the main 

inflow to Lake Maumelle, the Maumelle River at Williams 

Junction, Arkansas (07263295); at Lake Maumelle dam near 

Natural Steps, Arkansas (07263300); the main inflow to Lake 

Winona, the Alum Fork Saline River near Reform, Arkansas 

(07362587); and at Lake Winona dam at Reform (07362591) 

(fig. 1). Stage and instantaneous discharge were measured to 

compute the continuous streamflow from stage-discharge rating 

curves using methods described in Rantz and others (1982) for 

the Maumelle River and Alum Fork Saline River inflows to 

Lakes Maumelle and Winona. The stage data from Lake 

Maumelle dam and Lake Winona dam were used to compute 

daily mean lake volume from stage-capacity curves (Central 

Arkansas Water, written commun., 1990).

Lake Sampling

Fixed sampling sites were established along the downstream gradient of Lakes Maumelle and Winona. Sample sites 

in the lakes were located along the original stream channel, the 

deepest location within the lake cross section. The four sampling sites on Lake Maumelle were west of Highway 10 Bridge 

(upper end; 072632965), east of Highway 10 Bridge (upper end; 

07263297), near Little Italy (middle; 07263299), and near Natural Steps (lower end; 072632995) (fig. 1 and table 1). The three 

sampling sites on Lake Winona were downstream from Stillhouse Branch (upper end; 07362588), downstream from Gillis 

Branch (middle; 07362589), and at Reform (lower end; 

07362590) (fig. 1 and table 1). Samples were collected from 

1991 to 1998 using a 1-m by 5-cm bailer to collect depth-integrated composite samples representing the entire water column 

when isothermal conditions were present. During thermal stratification, depth-integrated samples were collected representing 

the epilimnion (near-surface) and hypolimnion (near-bottom). 

Samples were collected after 1998 using a peristaltic pump, 

instead of a bailer, in the epilimnion and hypolimnion during 

thermal stratification, and only in the epilimnion during isotherTable 1. Water-quality and streamflow sites for Lakes Maumelle and Winona.

Station

number Station name Station type Period of data

07263295 Maumelle River at Williams Junction Discharge, Water Quality 1989 through 2003

072632962 Bringle Creek near Crossroads Water Quality 1998, 2000, 2003

072632965 Lake Maumelle west of Highway 10 Bridge Water Quality 1991 through 1992, 2000, 2002 through 2003

07263297 Lake Maumelle east of Highway 10 Bridge Water Quality 1989 through 2000, 2002 through 2003

072632971 Yount Creek near Martindale Water Quality 1998, 2000, 2003

072632982 Reece Creek near Little Italy Water Quality 1998, 2000, 2003

07263299 Lake Maumelle near Little Italy Water Quality 1989 through 2000, 2002 through 2003

072632995 Lake Maumelle near Natural Steps Water Quality 1989 through 2000, 2002 through 2003

07263300 Maumelle River at Maumelle Dam near Natural Steps Discharge, Lake Stage 1989 through 2003

07362587 Alum Fork Saline River near Reform Discharge, Water Quality 1989 through 2003

07362588 Lake Winona downstream from Stillhouse Branch Water Quality 1995 through 2000, 2002 through 2003

07362589 Lake Winona downstream from Gillis Branch Water Quality 1995 through 2000, 2002 through 2003

07362590 Lake Winona at Reform Water Quality 1989 through 2000, 2002 through 2003

07362591 Lake Winona Dam at Reform Lake Stage 1989 through 2003
6 Water-Quality Assessment of Lakes Maumelle and Winona, Arkansas, 1991 Through 2003

mal conditions. Water-quality samples were analyzed for nutrients (dissolved orthophosphorus, total phosphorus, total ammonia plus organic nitrogen, dissolved ammonia, and dissolved 

nitrite plus nitrate), total and dissolved organic carbon, and 

chlorophyll a. All sample analyses were conducted at USGS 

laboratories following USGS procedures (Fishman, 1993). 

Field parameters (water temperature, dissolved-oxygen concentration, pH, and specific conductance) were measured at various 

depths. When thermal stratification was present, measurements 

were made at depth intervals where the change in temperature 

was 1 °C or at 0.3-m intervals, whichever was greater. Secchi 

depth also was measured at each site as an indicator of water 

clarity.

Samples were collected at various time intervals in Lakes 

Maumelle and Winona from 1989 through 2003 (table 1). Samples were collected from Lake Maumelle east of Highway 10 

Bridge, near Little Italy, and near Natural Steps and Lake 

Winona near Reform several times each year from 1989 

through 2003. A period of more intensive sampling was conducted on Lake Maumelle in 1991 and 1992 to develop a hydrodynamic and water-quality model of the reservoir (Green, 

2001). Samples were collected from Lake Maumelle west of 

Highway 10 Bridge in 1991, 1992, 2000, 2002, and 2003. Sample sites downstream from Stillhouse Branch and downstream 

from Gillis Branch on Lake Winona were collected only from 

1995 through 2000 and 2002 through 2003. Samples were not 

collected at any of the sites on Lakes Maumelle and Winona 

during 2001. Although data has been collected since 1989, only 

data for 1991 through 2003 are described in this report because 

different sampling methods were used prior to 1991. 

Inflow Sampling

Water-quality samples were collected from fixed sampling 

sites at the Maumelle River at Williams Junction (07263295) 

and the Alum Fork Saline River near Reform (07362587) from 

May 1989 to December 2003. Samples also were collected from 

three smaller tributaries to Lake Maumelle in 1998, 2000, and 

2003; Bringle Creek near Crossroads (072632962), Yount 

Creek near Martindale (072632971), and Reece Creek near Little Italy (072632982) (fig. 1 and table 1). Water-quality samples 

were collected following equal-width increment methods using 

depth-integrated samplers. Samples were collected and processed using protocols described in Wilde and Radke (1998), 

Wilde and others (1998a, 1998b, 1998c, 1999a, and 1999b), and 

Meyers and Wilde (1999). Samples were analyzed for nutrients 

and dissolved organic carbon by the USGS Ocala Water Quality 

and Research Laboratory in Ocala, Florida, following procedures described in Fishman (1993). Suspended sediment was 

analyzed by the USGS Missouri District laboratory following 

procedures described in Guy (1969). Fecal indicator bacteria 

(fecal coliform and fecal streptococci) were analyzed in the 

field by USGS personnel following procedures in Meyers and 

Wilde (1999). Field parameters, including water temperature, 

dissolved-oxygen concentration, pH, and specific conductance, 

also were measured with each sample collected. Water-quality 

samples generally were collected four times a year from 1991 

through 2003 and during high-flow events in 1991, 1992, 1996, 

2002, and 2003 at the Maumelle River and Alum Fork Saline 

River. Samples were collected only during high-flow events at 

Bringle, Yount, and Reece Creeks.

Data Analysis

Streamflow and water-quality data (inflow and lake samples) were analyzed or summarized using several statistical and 

graphical techniques. Boxplots and time-series plots were used 

to compare concentrations of selected water-quality constituents among sites for data collected from 1991 through 2003. 

Concentrations reported as less than a laboratory reporting limit 

were converted to one-half the reporting limit for preparation of 

boxplots, calculation of total nitrogen concentrations (the sum 

of nitrite plus nitrate and ammonia plus organic nitrogen), and 

statistical analyses. The Wilcoxon rank sum test (Helsel and 

Hirsch, 1992) was used to test for differences in selected waterquality constituents between sites. The Wilcoxon rank sum test 

is a nonparametric test that determines the probability (p) that 

the mean of a dataset is similar to the mean of another dataset 

within a 95 percent confidence interval. A locally weighted 

smooth (LOWESS) line was included in scatter plots of constituent concentrations with time. The LOWESS line is a locally 

weighted polynomial regression, where at each point along the 

line, a low-degree polynomial is fit to a subset of the data. The 

polynomial is fit using weighted least squares, giving more 

weight to points near the point whose response is being estimated and less weight to points further away.

Trophic State Indices

One method of classifying the water quality of a lake is by 

computing water-quality or Trophic State Index (TSI) values 

based on near-surface total phosphorus and chlorophyll a concentrations (Carlson, 1977). TSI values based on phosphorus 

concentrations (TSIP) and chlorophyll a concentrations (TSIC) 

were computed for each sampling by means of equations 1-3: 

TSIP = 10[6-log2 0.048/total phosphorus

(in milligrams per liter)] (1)

TSIC = 10[6-log2 7.7/(chlorophyll a)

0.68

(in micrograms per liter)] (2)

Trophic state indices can range on a gradual scale from 0 to 100. 

Trophic state indices less than 30 are commonly considered oligotrophic conditions, indices ranging from 50 to 70 are indicative of eutrophic conditions, and values greater than 70 are 

commonly considered hypereutrophic conditions (Wetzel, 

2001).
Water-Quality Assessment 7

Loads and Yields

Water-quality constituent loads and yields were calculated 

from concentrations and streamflow measured at the main 

inflow sites including the Maumelle River at Williams Junction 

and the Alum Fork Saline River near Reform. The S-LOADEST computer program (David Lorenz, U.S. Geological Survey, written commun., 2003) was used to estimate annual and 

seasonal constituent loads at the two sites for 1991 through 

2003. Constituent load (L) is a function of the volumetric rate of 

water passing a point in the stream (Q) and the constituent concentration within the water (C). Regression methods used to 

estimate constituent loads use the natural logarithm (ln) transformed relation between Q and C to estimate daily C (or L) of 

the constituent. The regression method can account for non-normal data distributions, seasonal and long-term cycles, censored 

data, biases associated with using logarithmic transformations, 

and serial correlations of the residuals (Cohn, 1995). The 

regression method uses discrete water-quality samples often 

collected over several years and a daily streamflow hydrograph. 

The complete model includes relations between natural logarithmic-transformed L and Q, time (T) and seasonality:

(3)

where L represents the constituent load, in kilograms per day;

 is the regression constant;

 and are regression

coefficients;

Q represents daily streamflow, in cubic meters per

second; and

T represents decimal time.

Substantial relations were not found between L and Q2, seasonality, and time for the data sets, and were not included in the 

regression analysis described in this report. Therefore, only the 

relations between natural logarithmic-transformed L and Q

were used to estimate annual and seasonal constituent loads:

(4)

Transforming the results of the model from logarithmic 

space to real space was accomplished using two methods; an 

adjusted maximum likelihood estimator (AMLE) (Cohn and 

others, 1992) and a least absolute deviation (LAD) (David 

Lorenz, U.S. Geological Survey, written commun., 2003). The 

AMLE method was used to transform the results if the constituent had censored values and the LAD method was used if no 

censored values were included in the data or if outliers in the 

residuals were present. 

Annual yields (kilograms per square kilometer) were calculated from estimated annual loads at each site. The yield was 

calculated by dividing the annual load (kilograms per year) by 

the drainage area contributing flow to the location of the sampling site (square kilometers). 

Flow-Weighted Concentrations

Flow-weighted concentrations also were calculated from 

the estimated annual loads. Flow-weighted concentrations were 

calculated by dividing the annual load by the annual mean 

streamflow, and applying appropriate conversion factors for 

dimensional units:

(5)

where CFW represents the flow-weighted concentration, in milligrams per liter,

L represents the annual constituent load in kilograms 

per year, and

Qannual represents the annual mean streamflow, in 

cubic meter per second.

Water-Quality Assessment

Hydrologic Conditions

Hydrologic conditions were monitored at the main inflows 

and outflows of Lakes Maumelle and Winona. Streamflow was 

continuously monitored at a station on the main inflow, the 

Maumelle River, upstream from Lake Maumelle at Williams 

Junction (07263295) (fig. 1). Continuous lake stage was 

recorded and reservoir outflow was measured at a station at 

Lake Maumelle dam at Natural Steps (07263300). Continuous 

streamflow was recorded upstream from Lake Winona at a station on the main inflow, the Alum Fork Saline River near 

Reform (07362587). Continuous lake stage was recorded at 

Lake Winona dam at Reform (07362591). 

Lake Maumelle

At the station at Williams Junction, the Maumelle River 

has a drainage area of 119.4 km2, which accounts for approximately 37 percent of the Lake Maumelle watershed at the dam. 

The Maumelle River exhibits typical seasonal variability with 

high-flows usually occurring in the winter (January through 

March), and spring (April through June), and low or no flow in 

the summer (July through September) and fall (October through 

December) (fig. 3). The mean annual streamflow for 1991 

through 2003 for the Maumelle River at Williams Junction was 

1.64 m3/s. The highest annual mean streamflow for the period 

of 1991 through 2003 was 2.51 m3/s in 1991 and the lowest 

annual mean streamflow was 1.11 m3/s in 1992 (fig. 3). The 

maximum instantaneous streamflow for the Maumelle River for 

the period of record (October 1989 through December 2003) 

was 183 m3/s that occurred on December 3, 1993 (Brossett and 

Evans, 2003).

ln( ) L βo β1 Q ) β2 Q2 ( )β3T β4T2

β5 ( )β 2πT 6 sin + cos( ) 2πT

+ +

+

= + ln + ln

βo

β1 β2 β3 β4 β5 ,,,, β6

() β L o β ln = + 1 ln( ) Q

CFW

L

Qannual

------------------- 3.171 –5 = × × 10
8 Water-Quality Assessment of Lakes Maumelle and Winona, Arkansas, 1991 Through 2003

Figure 3. Daily, monthly, and annual mean streamflow, and water-quality sampling times for the Maumelle River at Williams Junction, Arkansas, 1991 

through 2003.

MONTHLY MEAN STREAMFLOW

MONTH

STREAMFLOW, IN CUBIC METERS PER SECOND

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

0

1

2

3

4

ANNUAL MEAN STREAMFLOW

YEAR

1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004

0.0

0.5

1.0

1.5

2.0

2.5

3.0

MEAN

DAILY MEAN STREAMFLOW

DATE

1/1/91 1/1/92 1/1/93 1/1/94 1/1/95 1/1/96 1/1/97 1/1/98 1/1/99 1/1/00 1/1/01 1/1/02 1/1/03 1/1/04

0

20

40

60

80

100

WATER-QUALITY SAMPLE

MEAN

Much of the total streamflow in the Maumelle River during 1991 through 2003 occurred during relatively few days (fig. 

4). For example, 50 percent of the total streamflow (which 

delivers most of the constituent load to the reservoir) passed the 

station in about 18 days (5 percent of the year) in a typical year.

The water-level elevation (stage) and volume in Lake 

Maumelle demonstrated seasonal fluctuations resulting from 

seasonal inflows (fig. 5). Maximum volumes generally 

occurred in the fall and winter and minimum volumes occurred 

in late summer and fall. Lake volumes ranged from 224 million 

m3

 (1.2 m below the spillway elevation) to 299 million m3 (0.8 

m above the spillway elevation). The mean lake volume was 

262 million m3 with a corresponding stage of 88.2 m above 

NGVD of 1929 (0.2 m below the spillway elevation). 

Figure 4. Flow accumulation curve for the Maumelle River at Williams 

Junction, Arkansas, 1991 through 2003.

PERCENT CUMULATIVE DAYS

0 10 20 30 40 50 60 70 80 90 100

PERCENT CUMULATIVE STREAMFLOW

0

10

20

30

40

50

60

70

80

90

100
Water-Quality Assessment 9

Figure 5. Daily mean reservoir volumes for Lake Maumelle from stage

recorded at Lake Maumelle at Natural Steps, Arkansas (07263300), 1991 

through 2003.

Lake Winona

The Alum Fork Saline River upstream from Lake Winona 

has a drainage area of 69.9 km2

, or approximately 65 percent of 

the Lake Winona watershed at the dam. Similar to the 

Maumelle River, the Alum Fork Saline River demonstrates seasonal fluctuations with high flows in the late fall, winter, and 

early spring and low or no flows in the summer and early fall 

(fig. 6). The mean annual streamflow for the Alum Fork Saline 

River near Reform was 1.28 m3/s for 1991 through 2003. The 

highest annual mean streamflow was 2.32 m3/s that occurred in 

1991 and the lowest annual mean streamflow was 0.91 m3/s in 

1995 (fig. 6). The maximum instantaneous flow recorded at the 

Alum Fork Saline River for the period of record (October 1989 

through December 2003) was 382 m3/s on December 21, 1990 

DATE (Brossett and Evans, 2003). 

1/1/92 1/1/94 1/1/96 1/1/98 1/1/00 1/1/02 1/1/04

RESERVOIR VOLUME, IN MILLION CUBIC METERS 220

240

260

280

300

320

VOLUME AT SPILLWAY ELEVATION

Figure 6. Daily, monthly, and annual mean streamflow and water-quality sampling times for the Alum Fork Saline River near Reform Arkansas, 1991 

through 2003

MONTHLY MEAN STREAMFLOW

MONTH

STREAMFLOW, IN CUBIC METERS PER SECOND

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

0.0

0.5

1.0

1.5

2.0

2.5

3.0

willjunct

ANNUAL MEAN STREAMFLOW

1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004

0.0

0.5

1.0

1.5

2.0

2.5

MEAN

DAILY MEAN STREAMFLOW

DATE

1/1/91 1/1/92 1/1/93 1/1/94 1/1/95 1/1/96 1/1/97 1/1/98 1/1/99 1/1/00 1/1/01 1/1/02 1/1/03 1/1/04

0

20

40

60

80

100

WATER-QUALITY SAMPLE

MEAN
10 Water-Quality Assessment of Lakes Maumelle and Winona, Arkansas, 1991 Through 2003

Similar to the Maumelle River, much of the total streamflow in the Alum Fork Saline River during 1991 through 2003 

occurred during relatively few days (fig. 7). Fifty percent of the 

streamflow passed the station in 193 days (or 4 percent of the 

12-year period). This suggests that annually the upper 50 percent of the streamflow passes the station in about 15 days (4 percent of the year) in a typical year.

Figure 7. Flow accumulation curve for the Alum Fork Saline River near 

Reform, Arkansas, 1991 through 2003.

Seasonal fluctuations in the water level and volume 

occurred in Lake Winona from 1991 through 2003 as a result of 

seasonal fluctuations of the inflows and drinking-water withdrawals (fig. 8). Lake volumes ranged from 32.8 million m3

(4.3 m below the spillway elevation) to 53.9 million m3 (0.6 m 

above the spillway elevation). On average, the reservoir volume 

for the period was 46.1 million m3, with a stage of 224.4 m 

above NGVD of 1929 (1.1 m below the spillway elevation).

Figure 8. Daily mean reservoir volumes for Lake Winona from stage recorded at Lake Winona dam at Reform (07362591), Arkansas, 1991 

through 2003.

Lake Water Quality

This section describes the water-quality conditions monitored in Lakes Maumelle and Winona from 1991 through 2003 

(excluding 2001) pertaining to temperature, dissolved oxygen, 

nutrients, chlorophyll a, water clarity, and trophic status. Data 

were collected and analyzed for samples collected at four sites 

on Lake Maumelle and three sites on Lake Winona.

Lake Maumelle

Lake Maumelle was sampled at three locations from 1991 

through 2003 (excluding 2001) including sites east of Highway 

10 Bridge (07263297), near Little Italy (07263299) and near 

Natural Steps (072632995) (fig. 1). Lake Maumelle west of 

Highway 10 Bridge (072632965) was sampled only in 1991, 

1992, 2000, and 2003.

Temperature

The temperature distribution in Lake Maumelle exhibits 

typical seasonal cycles of lakes and reservoirs located within 

similar latitudes (Wetzel, 2001) (fig. 9). Lake Maumelle is a 

monomictic system, in which thermal stratification occurs 

annually during the summer and complete mixing occurs in the 

fall. Isothermal conditions exist throughout the winter and early 

spring.

Thermal stratification begins in the lower end of Lake 

Maumelle during May and June and generally becomes established by July (fig. 9). Thermal stratification is fully developed 

by late summer. Stratification occurs as the layer of water near 

the surface heats up during the spring, more rapidly than the 

heat is distributed throughout the water column, causing temperature or density gradients to develop. The warm, less dense 

water remains near the surface and the cooler, more dense water 

remains near the bottom. As a result of the density gradients, 

thermal resistance to mixing becomes established, physically 

isolating the epilimnion or mixing layer from the hypolimnion 

(Green, 1994). The thermocline usually is established at 

approximately 6 to 9 m depth in Lake Maumelle, with bottom 

temperatures ranging from 16 to 20 °C in the hypolimnion (fig. 

9).

Dissolved-Oxygen Concentrations

The distribution of dissolved oxygen in Lake Maumelle 

exhibits seasonal changes mainly because of the thermodynamics in the hypolimnion of the reservoir (fig. 10). Because the 

hypolimnion is isolated from the surface during periods of thermal stratification, reaeration from surface mixing is eliminated 

and very little, if any, oxygen input from photosynthetic activity 

from algae occurs below the thermocline (Green, 1994). Dissolved-oxygen concentrations during the winter remain uniform and near saturation levels because of complete water column mixing and isothermal conditions. As thermal stratification becomes established, dissolved-oxygen concentrations 

PERCENT CUMULATIVE DAYS

0 10 20 30 40 50 60 70 80 90 100

PERCENT CUMULATIVE STREAMFLOW

0

10

20

30

40

50

60

70

80

90

100

DATE

1/1/92 1/1/94 1/1/96 1/1/98 1/1/00 1/1/02 1/1/04

RESERVOIR VOLUME, IN MILLION CUBIC METERS

30

35

40

45

50

55

60

VOLUME AT SPILLWAY ELEVATION
Figure 9. Distribution of temperature with depth and time in Lake Maumelle near Natural Steps, Arkansas.

1512

9630

1512

9630

MAR-91 JUNE-91 AUG-91 NOV-91 FEB-92 MAY-92 AUG-92 NOV-92 FEB-93 MAY-93 AUG-93 NOV-93 FEB-94 MAY-94 AU

JAN-95 APR-95 JUNE-95 SEPT-91 DEC-95 MAR-96 JUNE-96 SEPT-96 DEC-96 MAR-97 JUNE-97 SEPT-97 DEC-97 MAR-98 JUNE-9

FEB-99 MAY-99 AUG-99 NOV-99 FEB-00 MAY-00 AUG-00 NOV-00 FEB-02 MAY-02 AUG-02 NOV-02 FEB-03 

1512

963

0

10 LINE OF EQUAL TEMPERATURE,

IN DEGREES CELSIUS - Interval 2degrees Celsius

EXPLANATION

DEPTH, IN METERS DEPTH, IN METERS DEPTH, IN METERS
Figure 10. Distribution of dissolved oxygen concentration with depth and time in Lake Maumelle near Natural Steps, Arkansas.

MAR-91 JUNE-91 AUG-91 NOV-91 FEB-92 MAY-92 AUG-92 NOV-92 FEB-93 MAY-93 AUG-93 NOV-93 FEB-94 MAY-94 A

JAN-95 APR-95 JUNE-95 SEPT-91 DEC-95 MAR-96 JUNE-96 SEPT-96 DEC-96 MAR-97 JUNE-97 SEPT-97 DEC-97 MAR-98 JUNE-9

FEB-99 MAY-99 AUG-99 NOV-99 FEB-00 MAY-00 AUG-00 NOV-00 FEB-02 MAY-02 AUG-02 NOV-02 FEB-03 

1512

9630

1512

9630

1512

963

0

10 LINE OF EQUAL DISSOLVED OXYGEN

CONCENTRATION, IN MILLIGRAMS PERLITER - Interval 1 milligram per liter

EXPLANATION

DEPTH, IN METERS DEPTH, IN METERS DEPTH, IN METERS
Water-Quality Assessment 13

in the hypolimnion decrease because of sediment and biochemical oxygen demand, and by summer, conditions in the hypolimnion are nearly anoxic (devoid of dissolved oxygen). In addition 

to sediment oxygen demand, Green (1994) suggests four possible factors contributing to the anoxic conditions in the hypolimnion in Lake Maumelle. First, the volume of water in the 

hypolimnion is relatively small, and as a result, the total mass of 

oxygen is limited. Second, the temperature of the hypolimnic 

water is relatively warm, further reducing the amount of oxygen 

that the water can contain because colder water can hold more 

dissolved oxygen than warmer water. Third, as phytoplankton 

and other particulate matter settles out of the water, oxygen is 

consumed by decay and chemical reduction within the hypolimnion. And fourth, once the surface water begins to heat up in the 

spring, the cooler inflow from the Maumelle River and other 

tributaries would tend to sink below the surface water because 

of the temperature related difference in water density. As a 

result, the organic and chemical load is displaced into the 

hypolimnion and adds to the consumption of oxygen.

Nutrient and Organic Carbon Concentrations 

The nutrient concentrations measured in the epilimnion 

varied both spatially and temporally in Lake Maumelle. Total 

ammonia plus organic nitrogen, nitrite plus nitrate, total nitrogen, and orthophosphorus measured in the upper reservoir (east 

of Highway 10) were not significantly different (p>0.05) than 

concentrations measured at the lower end (near Natural Steps) 

(figs. 1 and 11). Total phosphorus concentrations were significantly (p<0.05) less at the lower end of the lake than concentrations measured in the upper end of the lake for the period of 

1991 through 2003. Orthophosphorus concentrations were generally near or below laboratory detection limits for most of the 

samples.

The greatest concentrations of total nitrogen generally 

occurred in 1991 and from 1998 through 2003 at the three sites 

that were sampled since 1991 (fig. 12). Total ammonia plus 

organic nitrogen and nitrite plus nitrate concentrations generally were greatest in 1991. Nitrite plus nitrate concentrations in 

both ends of the lake were greatest from 1991 to 1992 and 1998 

through 2003. Total ammonia plus organic nitrogen concentrations increased from 1999 through 2003 in both ends of the lake.

Figure 11. Distribution of nutrient concentrations for four sites on Lake Maumelle, Arkansas.

TOTAL PHOSPHORUS

CONCENTRATION, IN MILLIGRAMS PER LITER AS PHOSPHORUS

0.00

0.01

0.02

0.03

0.04

ORTHOPHOSPHORUS

0.000

0.001

0.002

0.003

0.004

0.005

0.006

NITRITE PLUS NITRATE

CONCENTRATION, IN MILLIGRAMS PER LITER AS NITROGEN 0.00

0.01

0.02

0.03

0.04

0.05

10th percentile

25th percentile

50th percentile

75th percentile

90th percentile

TOTAL AMMONIA PLUS ORGANIC NITROGEN

0.0

0.2

0.4

0.6

0.8

TOTAL NITROGEN

0.0

0.1

0.2

0.3

0.4

0.5

0.6

EXPLANATION

EAST OF

HWY 10

NEAR

NATURAL

STEPS

NEAR

LITTLE

ITALY

WEST OF

HWY 10

18

49 47 55

7 49 47

55

10

49

47 55

7

47

47

55

17

47

47 55

EAST OF

HWY 10

NEAR

NATURAL

STEPS

NEAR

LITTLE

ITALY

WEST OF

HWY 10

48 Number of samples

a a a a

a a

a

a

a

b b b

a

b b

a

a a

a

a

a Distributions associated with the same letter

are not significantly (p<0.05) different
TOTAL AMMONIA PLUS ORGANIC NITROGEN Jan-92 Jan-95 Jan-98 Jan-01 Jan-04 0.0 0.2 0.4 0.6 0.8 NITRITE PLUS NITRATE Jan-92 Jan-95 Jan-98 Jan-01 Jan-04 0.00 0.02 0.04 0.06 0.08 0.10 TOTAL NITROGEN Jan-92 Jan-95 Jan-98 

0.0 0.2 0.4 0.6 0.8 TOTAL AMMONIA PLUS ORGANIC NITROGEN Jan-92 Jan-95 Jan-98 Jan-01 Jan-04

CONCENTRATION, IN MILLIGRAMS PER LITER AS NITROGEN 0.0 0.2 0.4 0.6 0.8 NITRITE PLUS NITRATE Jan-92 Jan-95 Jan-98 Jan-01 Jan-04 0.00 0.02 0.04 0.06 0.08 0.10

LAKE MAUMELLE EAST OF HIGHWAY 10 BRIDGE (07263297)

LAKE MAUMELLE NEAR LITTLE ITALY (07263299)

LAKE MAUMELLE NEAR NATURAL STEPS (072632995)

TOTAL NITROGEN

Jan-92 Jan-95 Jan-98 

0.00.20.40.60.8

TOTAL AMMONIA PLUS ORGANIC NITROGEN

Jan-92 Jan-95 Jan-98 Jan-01 Jan-04

0.00.20.40.60.8

NITRITE PLUS NITRATE

DATE

Jan-92 Jan-95 Jan-98 Jan-01 Jan-04

0.000.020.040.060.080.10

TOTAL NITROGEN

Jan-92 Jan-95 Jan-98 J

0.00.20.40.60.8

EXPLANATION

SAMPLE CONCENTRATION

LOCALLY WEIGHTED SMOOTH LINE (LOWES

SAMPLE CONCENTRATION BELOW REPORT

Figure 12. Time series of nitrogen concentrations for three sites on Lake Maumelle, Arkansas, 1991 through 2003.
Water-Quality Assessment 15

Total phosphorus concentrations generally were greatest 

from 1994 to 1996 and from 1998 to 2001 and lowest from 2002 

through 2003 at all three sampling sites (fig. 13). Orthophosphorus concentrations did not show any noticeable trends and 

generally were near or below laboratory detection limits from 

1991 through 2003.

Dissolved and total organic carbon concentrations measured in the epilimnion of Lake Maumelle were similar among 

sites (fig. 14). The median concentrations of dissolved organic 

carbon in Lake Maumelle west of Highway 10 Bridge, east of 

Highway 10 Bridge, near Little Italy, and near Natural Steps 

were 2.85 mg/L, 2.90 mg/L, 2.90 mg/L, and 2.70 mg/L as carbon, respectively. The 75th percentile of concentrations from 

samples collected at Lake Maumelle west of Highway 10 

Bridge in 2000 and 2003 was higher than the 75th percentile of 

concentrations of all samples collected at the other sampling 

sites. The greatest concentrations of dissolved and total organic 

carbon in the upper, middle, and lower parts of the lake 

occurred in 1996 and 1997 (fig. 15). Green (2001) indicated that 

the residence time in 1996 for Lake Maumelle was nearly four 

times greater than other years from 1990 to 1997, which suggest 

that greater dissolved and total organic carbon concentrations 

may have occurred because of internal loading within the reservoir.

Figure 13. Time series of phosphorus concentrations for three sites on Lake Maumelle, Arkansas, 1991 through 2003.

ORTHOPHOSPHORUS

Jan-92 Jan-95 Jan-98 Jan-01 Jan-04

0.000

0.005

0.010

0.015

0.020

0.025

TOTAL PHOSPHORUS

Jan-92 Jan-95 Jan-98 Jan-01 Jan-04

0.000

0.005

0.010

0.015

0.020

0.025

0.030

0.035

Jan-92 Jan-95 Jan-98 Jan-01 Jan-04

CONCENTRATION, IN MILLIGRAMS PER LITER AS PHOSPHORUS 0.000

0.005

0.010

0.015

0.020

0.025 TOTAL PHOSPHORUS

Jan-92 Jan-95 Jan-98 Jan-01 Jan-04

0.00

0.01

0.02

0.03

0.04

LAKE MAUMELLE EAST OF HIGHWAY 10 BRIDGE (07263297)

LAKE MAUMELLE NEAR LITTLE ITALY (07263299)

LAKE MAUMELLE NEAR NATURAL STEPS (072632995)

ORTHOPHOSPHORUS

DATE

Jan-92 Jan-95 Jan-98 Jan-01 Jan-04

0.000

0.005

0.010

0.015

0.020

0.025 TOTAL PHOSPHORUS

DATE

Jan-92 Jan-95 Jan-98 Jan-01 Jan-04

0.00

0.01

0.02

0.03

0.04

ORTHOPHOSPHORUS

EXPLANATION

SAMPLE CONCENTRATION

LOCALLY WEIGHTED SMOOTH LINE (LOWESS)

SAMPLE CONCENTRATION BELOW REPORTING LIMIT
16 Water-Quality Assessment of Lakes Maumelle and Winona, Arkansas, 1991 Through 2003

Figure 14. Distribution of organic carbon concentrations for four sites on Lake Maumelle, Arkansas.

Figure 15. Time series of organic carbon concentrations for three sites on Lake Maumelle, Arkansas, 1991 through 2003. CONCENTRATION, IN MILLIGRAMS PER LITER AS CARBON

10th percentile

25th percentile

50th percentile

75th percentile

90th percentile

EXPLANATION

Number of samples 56

a Distributions associated

with the same letter

are not significantly

(p<0.05) different

DISSOLVED ORGANIC CARBON

0

2

4

6

8

7

50 48

a 56

a a a

TOTAL ORGANIC CARBON

0

2

4

6

8

EAST OF

HWY 10

NEAR

NATURAL

STEPS

NEAR

LITTLE

ITALY

WEST OF

HWY 10

31

7

31

38

a

a a a

DISSOLVED ORGANIC CARBON

Jan-92 Jan-95 Jan-98 Jan-01 Jan-04

0

2

4

6

8 TOTAL ORGANIC CARBON

Jan-92 Jan-95 Jan-98 Jan-01 Jan-04

0

2

4

6

8

10

DISSOLVED ORGANIC CARBON

Jan-92 Jan-95 Jan-98 Jan-01 Jan-04

CONCENTRATION, IN MILLIGRAMS PER LITER AS CARBON 0

2

4

6

8 TOTAL ORGANIC CARBON

Jan-92 Jan-95 Jan-98 Jan-01 Jan-04

0

2

4

6

8

10

LAKE MAUMELLE EAST OF HIGHWAY 10 BRIDGE (07263297)

LAKE MAUMELLE NEAR LITTLE ITALY (07263299)

LAKE MAUMELLE NEAR NATURAL STEPS (072632995)

DISSOLVED ORGANIC CARBON

DATE

Jan-92 Jan-95 Jan-98 Jan-01 Jan-04

0

2

4

6

8

SAMPLE CONCENTRATION

LOCALLY WEIGHTED SMOOTH LINE (LOWESS)

TOTAL ORGANIC CARBON

DATE

Jan-92 Jan-95 Jan-98 Jan-01 Jan-04

0

2

4

6

8

10

EXPLANATION
Water-Quality Assessment 17

Figure 16. Distribution of chlorophyll a concentrations or four sites on Lake Maumelle, Arkansas. CHLOROPHYLL a CONCENTRATION, IN MICROGRAMS PER LITER

0

2

4

6

8

EAST OF

HWY 10

NEAR

NATURAL

STEPS

NEAR

LITTLE

ITALY

WEST OF

HWY 10

47

44

51

7

10th percentile

25th percentile

50th percentile

75th percentile

90th percentile

EXPLANATION

47 Number of samples

a Distributions associated

with the same letter

are not significantly

(p<0.05) different

a

a a a

Chlorophyll a Concentrations

Concentrations of chlorophyll a were relatively uniform 

spatially and temporally in Lake Maumelle. Chlorophyll a is a 

photosynthetic pigment found in algae and other green plants. 

The concentration of chlorophyll a, therefore, is commonly 

used as a measure of the density of the algal population of a 

lake. The chlorophyll a concentrations east of Highway 10 

Bridge (upper end of the lake) had a median value of 2.60 μg/L, 

while concentrations from samples collected at the lower end of 

the lake (near Natural Steps) had a median concentration of 2.85 

μg/L for the period of 1991 through 2003 (fig. 16). Concentrations of chlorophyll a remained fairly uniform from 1991 

through 2003, although slightly higher concentrations were evident in 1998 to 2000 at all the sampled sites (fig. 17). The chlorophyll a concentrations varied seasonally, with the highest 

median concentrations generally during August through 

November, and the lowest concentrations during March 

through July (fig. 18).

Figure 18. Median monthly chlorophyll a concentrations for Lake 

Maumelle near Natural Steps, Arkansas, 1991 through 2003.

Figure 17. Time series of chlorophyll a concentrations for three sites on 

Lake Maumelle, Arkansas, 1991 through 2003.

MONTH

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

MEDIAN CHLOROPHYLL a CONCENTRATION,

IN MICROGRAMS PER LITER 0

1

2

3

4

5

6

7

NO DATA

LAKE MAUMELLE EAST OF HIGHWAY 10 BRIDGE (07263297)

Jan-92 Jan-94 Jan-96 Jan-98 Jan-00 Jan-02 Jan-04

0

2

4

6

8

10

12

14

16

18

LAKE MAUMELLE NEAR LITTLE ITALY (07263299)

Jan-92 Jan-94 Jan-96 Jan-98 Jan-00 Jan-02 Jan-04

CHLOROPHYLL a CONCENTRATION, IN MCROGRAMS PER LITER

0

2

4

6

8

10

12

14

16

18

LAKE MAUMELLE NEAR NATURAL STEPS (072632995)

DATE

Jan-92 Jan-94 Jan-96 Jan-98 Jan-00 Jan-02 Jan-04

0

2

4

6

8

10

12

14

16

18

SAMPLE CONCENTRATION

LOCALLY WEIGHTED SMOOTH LINE (LOWESS)

EXPLANATION
18 Water-Quality Assessment of Lakes Maumelle and Winona, Arkansas, 1991 Through 2003

Figure 19. Distribution of Secchi depths for four sites on Lake Maumelle, Arkansas. SECCHI DEPTH, IN METERS

0

1

2

3

4

10th percentile

25th percentile

50th percentile

75th percentile

90th percentile

EXPLANATION

EAST OF

HWY 10

NEAR

NATURAL

STEPS

NEAR

LITTLE

ITALY

WEST OF

HWY 10

26

61

59

65

65 Number of samples

a Distributions associated

with the same letter

are not significantly

(p<0.05) different

a

b

c

c

Water Clarity

During the study period, water clarity measured in Lake 

Maumelle was significantly greater at the lower end than in the 

upper end of the lake (fig. 19). The median Secchi depth measured in the upper end (west of Highway 10 Bridge) was 1.1 m, 

and median Secchi depth at the lower end was 2.4 m for the 

period of 1991 through 2003. Secchi depth varied seasonally, 

with the greatest median depth from July through September 

and the least median depth during October through December 

(fig. 20). However, no apparent trends during 1991 through 

2003 were observed at sites in the reservoir (fig. 21).

Figure 20. Median monthly Secchi depths for Lake Maumelle near

Natural Steps, Arkansas, 1991 through 2003.

Figure 21. Time series of Secchi depth for three sites on Lake Maumelle, 

Arkansas, 1991 through 2003.

MONTH

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

MEDIAN SECCHI DEPTH, IN METERS 0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

LAKE MAUMELLE EAST OF HIGHWAY 10 BRIDGE (07263297)

Jan-92 Jan-94 Jan-96 Jan-98 Jan-00 Jan-02 Jan-04

0

1

2

3

4

5

LAKE MAUMELLE NEAR LITTLE ITALY (07263299)

Jan-92 Jan-94 Jan-96 Jan-98 Jan-00 Jan-02 Jan-04

SECCHI DEPTH, IN METERS

0

1

2

3

4

5

LAKE MAUMELLE NEAR NATURAL STEPS (072632995)

DATE

Jan-92 Jan-94 Jan-96 Jan-98 Jan-00 Jan-02 Jan-04

0

1

2

3

4

5

SECCHI DEPTH MEASUREMENT

LOCALLY WEIGHTED SMOOTH LINE (LOWESS)

EXPLANATION
Water-Quality Assessment 19

Trophic Status

The trophic status of a reservoir is an indicator of the age 

of a reservoir as it progresses towards physical, chemical, and 

biological equilibrium. In general, as a reservoir matures, the 

trophic condition evolves from oligotrophy to mesotrophy, 

mesotrophy to eutrophy, and eutrophy to hypereutrophy. Oligotrophy is considered the most pristine water-quality condition, 

and hypereutrophy is the poorest water-quality condition (Wetzel, 2001). Influences from cultural activities can accelerate the 

natural progression of the reservoir towards equilibrium from 

hundreds of years to a few decades. 

The Trophic State Indices (TSI) indicated conditions ranging from oligotrophic to mesotrophic for three sites on Lake 

Maumelle. Epilimnetic TSI values for total phosphorus and 

chlorophyll a for three sites on Lake Maumelle indicated the 

lake is generally oligotrophic although some fluctuations 

between mesotrophic and oligotrophic conditions were 

observed over time (fig. 22). 

Figure 22. Trophic state indices for three sites on Lake Maumelle, Arkansas, 1991 through 2003.

TOTAL PHOSPHORUS

20

25

30

35

40

45

50

55

60

OLIGOTROPHIC

MESOTROPHIC

EUTROPHIC

CHLOROPHYLL a

TROPHIC STATE INDEX

20

25

30

35

40

45

50

55

60

OLIGOTROPHIC

MESOTROPHIC

EUTROPHIC

25th percentile

50th percentile

75th percentile

90th percentile

EXPLANATION

10th percentile

EAST OF

HWY 10

NEAR

LITTLE

ITALY

NEAR

NATURAL

STEPS
20 Water-Quality Assessment of Lakes Maumelle and Winona, Arkansas, 1991 Through 2003

Lake Winona

Lake Winona was sampled downstream from Stillhouse 

Branch (upper end of lake) (07362588) and downstream from 

Gillis Branch (middle) (07362589) from 1995 through 2003 

(excluding 2001). Lake Winona at Reform (lower end of the 

lake) (07362590) was sampled from 1991 through 2003 

(excluding 2001) (fig. 1).

Temperature

Lake Winona is representative of a monomictic system 

similar to Lake Maumelle that has a temperature distribution 

with seasonal cycles of thermal stratification occurring annually 

during the summer, complete mixing in the fall, and isothermal 

conditions in the winter (fig. 23). At the lower end of Lake 

Winona, mixing in the winter is not as complete as observed in 

Lake Maumelle, although the thermocline, which usually 

occurs at 3 to 6 m in depth, is more pronounced than in Lake 

Maumelle in the summer. Temperatures below a depth of 12 m 

in Lake Winona ranged from 8 to 13 °C during the summer.

Dissolved-Oxygen Concentrations

The distribution of dissolved-oxygen concentrations in 

Lake Winona differed from those observed at Lake Maumelle 

(fig. 24). Dissolved-oxygen concentrations in the hypolimnion 

generally were higher in Lake Winona than in Maumelle, 

because of the cooler temperatures in Lake Winona (fig. 23). 

The cooler temperatures in the hypolimnion allow inflow from 

the Alum Fork Saline River and other tributaries to move 

through the metalimnion (middle layers) of the lake, and the 

associated organic and chemical load would consume the oxygen in the metalimnion (Green, 1994). The volume of water in 

the hypolimnion also is greater in Lake Winona than in Lake 

Maumelle, allowing for greater concentrations of oxygen. During stratification, approximately 58 percent of the reservoir volume in Lake Winona is below the thermocline, whereas in Lake 

Maumelle, only about 28 percent of the reservoir volume is 

below the thermocline. The greater volume of water in the 

hypolimnion allows for more dissolved oxygen to be available 

for chemical and biological demand.

Nutrient and Organic Carbon Concentrations 

Nitrogen concentrations were not significantly different 

among sampling sites for the period of 1991 through 2003 (fig. 

25). Median total nitrogen concentrations ranged from 0.150 

mg/L in the middle of Lake Winona to 0.240 mg/L at the upper 

end of the lake. Nitrate plus nitrite concentrations were slightly 

greater at the lower end of the lake with a median value of 0.014 

mg/L, compared to median concentrations of 0.009 mg/L measured in the middle and upper end of the lake. Total ammonia 

plus organic nitrogen concentrations were mostly near or below 

detection limits at all three sampling sites.

Temporal differences were observed in nitrogen concentrations in Lake Winona. Total nitrogen concentrations generally were greater in 2000 through 2003 than in previous years at 

all three sampling sites and concentrations measured at the 

lower end of the lake also were greater in 1991 than subsequent 

years (fig. 26). Nitrite plus nitrate concentrations generally 

were greatest in 1995 through 1999 at all three sampling sites.

Phosphorus concentrations in Lake Winona varied spatially and temporally. Median total phosphorus concentrations 

were significantly greater at the upper end of Lake Winona than 

at the middle and lower ends of the lake (fig. 25). Total phosphorus concentrations measured at the lower end of Lake 

Winona generally were less in 1991, 1992, 2002, and 2003, and 

greater concentrations were measured in 1993 and 1994 (fig. 

27). Concentrations of total phosphorus generally were greatest 

in 1995 through 1997 in the upper and middle portions of the 

lake. Orthophosphorus concentrations mostly were near or 

below the laboratory detection limits at all three sampling sites 

for the period. 

Concentrations of total and dissolved organic carbon were 

not significantly different among sampling sites but did vary 

temporally. The highest concentrations of organic carbon were 

observed at the lower end of Lake Winona with median concentrations of 3.40 mg/L as carbon for total organic carbon and 

3.20 mg/L as carbon for dissolved organic carbon (fig. 28). The 

upper end of Lake Winona had similar values, and the middle 

had the lowest values with median concentrations of 3.00 mg/L 

as carbon for total organic carbon and 2.80 mg/L as carbon for 

dissolved organic carbon. The highest concentrations of organic 

carbon were measured in 1996 and 1997 (fig. 29). Similar to 

Lake Maumelle, high concentrations in 1996 and 1997 for Lake 

Winona may have occurred because of internal loading within 

the reservoir. At the lower end of Lake Winona, where samples 

were analyzed for dissolved organic carbon since 1991, concentrations of dissolved organic carbon also were relatively higher 

in 1991 compared to subsequent years.

Chlorophyll a Concentrations

Chlorophyll a concentrations in Lake Winona were not 

significantly different among sampling sites, although the concentrations generally decreased from the upper end of the lake 

to the lower end (fig. 30). The median concentrations of chlorophyll a measured in the upper end, middle, and lower end of 

Lake Winona were 2.00 μg/L, 1.70 μg/L, and 1.3 μg/L, respectively.

Chlorophyll a concentrations varied annually and seasonally in Lake Winona. The greatest concentrations of chlorophyll 

a were observed in 1997 and 2000 at all three sampling sites 

(fig. 31). Concentrations of chlorophyll a did not have as noticeable of a seasonal trend as observed in Lake Maumelle, with the 

highest concentrations occurring in October and November 

(fall) and the lowest concentrations occurring in December, 

January, and February (winter), and June (early summer) (fig. 

32).
Figure 23. Distribution of temperature with depth and time in Lake Winona at Reform, Arkansas.

MAR-91 JUNE-91 AUG-91 NOV-91 FEB-92 MAY-92 AUG-92 NOV-92 FEB-93 MAY-93 AUG-93 NOV-93 FEB-94 MAY-94 AU

APR-95 JUNE-95 SEPT-91 DEC-95 MAR-96 JUNE-96 SEPT-96 DEC-96 MAR-97 JUNE-97 SEPT-97 DEC-97 MAR-98 JUNE-98 

FEB-99 MAY-99 AUG-99 NOV-99 FEB-00 MAY-00 AUG-00 FEB-02 MAY-02 AUG-02 NOV-02 FEB-03 

2421181512

9630

2421181512

9630

2421181512

9630

10 LINE OF EQUAL TEMPERATURE,

IN DEGREES CELSIUS - Interval 2 degrees Celsius

EXPLANATION

DEPTH, IN METERS DEPTH, IN METERS DEPTH, IN METERS
Figure 24. Distribution of dissolved oxygen concentration with depth and time in Lake Winona at Reform, Arkansas.

MAR-91 JUNE-91 AUG-91 NOV-91 FEB-92 MAY-92 AUG-92 NOV-92 FEB-93 MAY-93 AUG-93 NOV-93 FEB-94 MAY-94 AU

APR-95 JUNE-95 SEPT-91 DEC-95 MAR-96 JUNE-96 SEPT-96 DEC-96 MAR-97 JUNE-97 SEPT-97 DEC-97 MAR-98 JUNE-98 

FEB-99 MAY-99 AUG-99 NOV-99 FEB-00 MAY-00 AUG-00 FEB-02 MAY-02 AUG-02 NOV-02 FEB-03 

2421181512

9630

2421181512

9630

2421181512

9630

10 LINE OF EQUAL DISSOLVED OXYGEN

CONCENTRATION, IN MILLIGRAMS PERLITER - Interval 1 milligram per liter

EXPLANATION

DEPTH, IN METERS DEPTH, IN METERS DEPTH, IN METERS
 Water-Quality Assessment 23

Figure 25. Distribution of nutrient concentrations for three sites on Lake Winona, Arkansas.

TOTAL PHOSPHORUS

CONCENTRATION, IN MILLIGRAMS PER LITER AS PHOSPHORUS

0.000

0.005

0.010

0.015

0.020

ORTHOPHOSPHORUS

0.000

0.001

0.002

0.003

0.004

0.005

NITRITE PLUS NITRATE

CONCENTRATION, IN MILLIGRAMS PER LITER AS NITROGEN 0.00

0.02

0.04

0.06

0.08

0.10

25th percentile

50th percentile

75th percentile

90th percentile

TOTAL AMMONIA PLUS ORGANIC NITROGEN

0.0

0.1

0.2

0.3

0.4

0.5

TOTAL NITROGEN

0.0

0.2

0.4

0.6 EXPLANATION

DOWNSTREAM

FROM STILLHOUSE BRANCH

AT

REFORM

DOWNSTREAM

FROM GILLIS

BRANCH

30

28 29

47

47

28

28 47

29

10th percentile

27

30

47

28 30 47

DOWNSTREAM

FROM STILLHOUSE BRANCH

AT

REFORM

DOWNSTREAM

FROM GILLIS

BRANCH

47 Number of samples

a Distributions associated

with the same letter

are not significantly

(p<0.05) different

a

a a

a a

a

a

a a

a

a

a

a

b b
Figure 26. Time series of nitrogen concentrations for three sites on Lake Winona, Arkansas.

TOTAL AMMONIA PLUS ORGANIC NITROGEN

Jan-92 Jan-95 Jan-98 Jan-01 Jan-04

0.00.20.40.60.81.0

NITRITE PLUS NITRATE

Jan-92 Jan-95 Jan-98 Jan-01 Jan-04

0.000.050.100.150.200.25

TOTAL NITROGEN

Jan-92 Jan-95 Jan-98 Ja

0.00.20.40.60.81.0

TOTAL AMMONIA PLUS ORGANIC NITROGEN

Jan-92 Jan-95 Jan-98 Jan-01 Jan-04

CONCENTRATION, IN MILLIGRAMS PER LITER AS NITROGEN 0.0 0.2 0.4 0.6 0.8 1.0 NITRITE PLUS NITRATE Jan-92 Jan-95 Jan-98 Jan-01 Jan-04 0.00 0.05 0.10 0.15 0.20 0.25

LAKE WINONA DOWNSTREAM FROM STILLHOUSE BRANCH (07362588)

LAKE WINONA DOWNSTREAM FROM GILLIS BRANCH (07362589)

LAKE WINONA AT REFORM (07362590)

TOTAL NITROGEN

Jan-92 Jan-95 Jan-98 Jan-

0.00.20.40.60.81.0

TOTAL AMMONIA PLUS ORGANIC NITROGEN

Jan-92 Jan-95 Jan-98 Jan-01 Jan-04

0.00.20.40.60.81.0

NITRITE PLUS NITRATE

DATE

Jan-92 Jan-95 Jan-98 Jan-01 Jan-04

0.000.050.100.150.200.25

TOTAL NITROGEN

Jan-92 Jan-95 Jan-98 Jan-

0.00.20.40.60.81.0

EXPLANATION

SAMPLE CONCENTRATION

LOCALLY WEIGHTED SMOOTH LINE (LOW

SAMPLE CONCENTRATION BELOW REPOR
 Water-Quality Assessment 25

Figure 27. Time series of phosphorus concentrations for three sites on Lake Winona, Arkansas.

ORTHOPHOSPHORUS

Jan-92 Jan-95 Jan-98 Jan-01 Jan-04

0.000

0.005

0.010

0.015

0.020

TOTAL PHOSPHORUS

Jan-92 Jan-95 Jan-98 Jan-01 Jan-04

0.000

0.005

0.010

0.015

0.020

ORTHOPHOSPHORUS

Jan-92 Jan-95 Jan-98 Jan-01 Jan-04

CONCENTRATION, IN MILLIGRAMS PER LITER AS PHOSPHORUS

0.000

0.005

0.010

0.015

0.020 TOTAL PHOSPHORUS

Jan-92 Jan-95 Jan-98 Jan-01 Jan-04

0.000

0.005

0.010

0.015

0.020

LAKE WINONA DOWNSTREAM FROM STILLHOUSE BRANCH (07362588)

LAKE WINONA DOWNSTREAM FROM GILLIS BRANCH (07362589)

LAKE WINONA AT REFORM (07362590)

ORTHOPHOSPHORUS

DATE

Jan-92 Jan-95 Jan-98 Jan-01 Jan-04

0.000

0.004

0.008

0.012

0.016

0.020 TOTAL PHOSPHORUS

DATE

Jan-92 Jan-95 Jan-98 Jan-01 Jan-04

0.000

0.004

0.008

0.012

0.016

0.020

EXPLANATION

SAMPLE CONCENTRATION

LOCALLY WEIGHTED SMOOTH LINE (LOWESS)

SAMPLE CONCENTRATION BELOW REPORTING LIMIT
26 Water-Quality Assessment of Lakes Maumelle and Winona, Arkansas, 1991 Through 2003

Figure 28. Distribution of organic carbon concentrations for three sites on Lake Winona, Arkansas.

Figure 29. Time series of organic carbon concentrations for three sites on Lake Winona, Arkansas. CONCENTRATION, IN MILLIGRAMS PER LITER AS CARBON

10th percentile

25th percentile

50th percentile

75th percentile

90th percentile

EXPLANATION

46 Number of samples

a Distributions associated

with the same letter

are not significantly

(p<0.05) different

DISSOLVED ORGANIC CARBON

0

2

4

6

8

27 29

46

a a

a

TOTAL ORGANIC CARBON

0

2

4

6

8

DOWNSTREAM

FROM STILLHOUSE BRANCH

AT

REFORM

DOWNSTREAM

FROM GILLIS

BRANCH

27

29 37

a a a

DISSOLVED ORGANIC CARBON

Jan-92 Jan-95 Jan-98 Jan-01 Jan-04

0

2

4

6

8

10

TOTAL ORGANIC CARBON

Jan-92 Jan-95 Jan-98 Jan-01 Jan-04

0

2

4

6

8

10

DISSOLVED ORGANIC CARBON

Jan-92 Jan-95 Jan-98 Jan-01 Jan-04

CONCENTRATION, IN MILLIGRAMS PER LITER AS CARBON

0

2

4

6

8

10 TOTAL ORGANIC CARBON

Jan-92 Jan-95 Jan-98 Jan-01 Jan-04

0

2

4

6

8

10

LAKE WINONA DOWNSTREAM FROM STILLHOUSE BRANCH (07362588)

LAKE WINONA DOWNSTREAM FROM GILLIS BRANCH (07362589)

LAKE WINONA AT REFORM (07362590)

DISSOLVED ORGANIC CARBON

DATE

Jan-92 Jan-95 Jan-98 Jan-01 Jan-04

0

2

4

6

8

10

SAMPLE CONCENTRATION

LOCALLY WEIGHTED SMOOTH LINE (LOWESS)

TOTAL ORGANIC CARBON

DATE

Jan-92 Jan-95 Jan-98 Jan-01 Jan-04

0

2

4

6

8

10

EXPLANATION
Water-Quality Assessment 27

Figure 30. Time series of chlorophyll a concentrations for three sites on Lake Winona, Arkansas. CHLOROPHYLL a CONCENTRATION, IN MICROGRAMS PER LITER

0

1

2

3

4

5

DOWNSTREAM

FROM STILLHOUSE BRANCH

AT

REFORM

DOWNSTREAM

FROM GILLIS

BRANCH

27

29

44

10th percentile

25th percentile

50th percentile

75th percentile

90th percentile

EXPLANATION

44 Number of samples

a Distributions associated

with the same letter

are not significantly

(p<0.05) different

a

a

a

Figure 31. Time series of chlorophyll a concentrations for three sites on 

Lake Winona, Arkansas.

Figure 32. Median monthly chlorophyll a concentrations for Lake Winona 

at Reform, Arkansas, 1991 through 2003.

LAKE WINONA DOWNSTREAM FROM STILLHOUSE BRANCH (07362588)

Jan-92 Jan-94 Jan-96 Jan-98 Jan-00 Jan-02 Jan-04

0

1

2

3

4

5

6

LAKE WINONA DOWNSTREAM FROM GILLIS BRANCH (07362589)

Jan-92 Jan-94 Jan-96 Jan-98 Jan-00 Jan-02 Jan-04

CHLOROPHYLL a CONCENTRATION, IN MICROGRAMS PER LITER

0

1

2

3

4

5

6

LAKE WINONA AT REFORM (07362590)

DATE

Jan-92 Jan-94 Jan-96 Jan-98 Jan-00 Jan-02 Jan-04

0

1

2

3

4

5

6

SAMPLE CONCENTRATION

LOCALLY WEIGHTED SMOOTH LINE (LOWESS)

EXPLANATION

MONTH

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

CHLOROPHYLL a CONCENTRATION,

IN MICROGRAMS PER LITER

0.0

0.5

1.0

1.5

2.0

2.5

NO DATA
28 Water-Quality Assessment of Lakes Maumelle and Winona, Arkansas, 1991 Through 2003

Figure 33. Distribution of Secchi depths for three sites on Lake Winona, Arkansas. SECCHI DEPTH, IN METERS

0

1

2

3

4

5

10th percentile

25th percentile

50th percentile

75th percentile

90th percentile

EXPLANATION

DOWNSTREAM

FROM STILLHOUSE BRANCH

AT

REFORM

DOWNSTREAM

FROM GILLIS

BRANCH

31

32 47

47 Number of samples

a Distributions associated

with the same letter

are not significantly

(p<0.05) different

a

b b

Water Clarity

The water clarity in Lake Winona varied spatially and temporally. The Secchi depth measured in the upper lake generally 

was significantly less than Secchi depth measured in the middle 

and lower lake (fig. 33). The median Secchi depth for the upper 

lake was 1.90 m and for the lower lake was 2.44 m. The water 

clarity in the middle of the lake was slightly greater than measured in the lower lake with a median Secchi depth of 2.50 m. 

Although water clarity changes seasonally throughout a given 

year (fig. 34), no noticeable trend was observed for the entire 

study period (fig. 35). However, Secchi depth measurements 

made in 2002 and 2003 were slightly less than previous years.

Figure 34. Median monthly Secchi depths for Lake Winona at Reform,

Arkansas, 1991 through 2003. Figure 35. Time series of Secchi depth for three sites on Lake Winona, 

Arkansas.

MONTH

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

MEDIAN SECCHI DEPTH, IN METERS 0

1

2

3

4

NO DATA

LAKE WINONA DOWNSTREAM FROM STILLHOUSE BRANCH (07362588)

Jan-92 Jan-94 Jan-96 Jan-98 Jan-00 Jan-02 Jan-04

0

1

2

3

4

5

LAKE WINONA DOWNSTREAM FROM GILLIS BRANCH (07362589)

Jan-92 Jan-94 Jan-96 Jan-98 Jan-00 Jan-02 Jan-04

SECCHI DEPTH, IN METERS

0

1

2

3

4

5

LAKE WINONA AT REFORM (07362590)

DATE

Jan-92 Jan-94 Jan-96 Jan-98 Jan-00 Jan-02 Jan-04

0

1

2

3

4

5

SECCHI DEPTH MEASUREMENT

LOCALLY WEIGHTED SMOOTH LINE (LOWESS)

EXPLANATION
Water-Quality Assessment 29

Trophic Status

TSI calculated from near-surface concentrations of total 

phosphorus and chlorophyll a classify Lake Winona as mainly 

oligotrophic. Green (1994) presented similar conditions using 

data from 1989 through 1992, which indicates that little change 

in the trophic status of Lake Winona has occurred from 1989 

through 2003.

Figure 36. Trophic state indices for three sites on Lake Winona, Arkansas.

TOTAL PHOSPHORUS

20

25

30

35

40

45

50

55

60

OLIGOTROPHIC

MESOTROPHIC

EUTROPHIC

CHLOROPHYLL a

TROPHIC STATE INDEX

20

25

30

35

40

45

50

55

60

OLIGOTROPHIC

MESOTROPHIC

EUTROPHIC

25th percentile

50th percentile

75th percentile

90th percentile

EXPLANATION

10th percentile

DOWNSTREAM

FROM

STILLHOUSE

BRANCH

DOWNSTREAM

FROM

GILLIS

BRANCH

AT REFORM
30 Water-Quality Assessment of Lakes Maumelle and Winona, Arkansas, 1991 Through 2003

Inflow Water Quality

Lake Maumelle

Samples were collected at four inflow sites on Lake 

Maumelle. The Maumelle River at Williams Junction (fig. 1) is 

the main inflow and was sampled from 1991 through 2003 

(excluding 2001). Bringle, Yount, and Reece Creeks (fig. 1) 

were sampled only in 1998, 2000, and 2003 during high-flow 

events because these creeks are intermittent. This section summarizes the constituent concentrations for the four inflows, and 

presents the estimated annual and seasonal loads, yields, and 

flow-weighted concentrations for the Maumelle River.

Constituent Concentrations

Nutrient concentrations generally were lower in samples 

from the Maumelle River than in samples from the smaller 

inflows (Bringle, Yount, and Reece Creeks) (fig. 37). However, 

samples were collected only during high-flow events at all of 

the smaller inflows and mostly during base-flow conditions on 

the Maumelle River. Median concentrations of total ammonia 

plus organic nitrogen, nitrite plus nitrate, and total nitrogen for 

the Maumelle River were 0.200, 0.016, and 0.244 mg/L as 

nitrogen, respectively. Median nitrogen and phosphorus concentrations for Bringle, Yount, and Reece Creeks were approximately double the concentrations measured on the Maumelle 

River and the median nitrite plus nitrate concentration on Bringle Creek was five times the median concentration for the 

Maumelle River. Total phosphorus concentrations for the 

Maumelle River had a median value of 0.012 mg/L as phosphorus and orthophosphorus concentrations were mostly near or 

below the laboratory detection limit for the period.

The median dissolved organic carbon concentration for the 

Maumelle River was 3.25 mg/L as carbon. Bringle, Yount, and 

Reece Creeks had only one sample at each site analyzed for dissolved organic carbon with values of 3.8, 5.6, and 3.8 mg/L as 

carbon, respectively.

Figure 37. Distribution of nutrient, dissolved organic carbon, and suspended-sediment concentrations for four inflow sites to Lake Maumelle. CONCENTRATION, IN MILLIGRAMS PER LITER AS PHOSPHORUS CONCENTRATION, IN MILLIGRAMS PER LITER AS NITROGEN

DISSOLVED ORGANIC CARBON

CONCENTRATION, IN MILLIGRAMS

PER LITER AS CARBON 0

2

4

6

8

10

12

14

61

Maumelle

River

CONCENTRATION, IN

MILLIGRAMS PER LITER

10th percentile

25th percentile

50th percentile

75th percentile

90th percentile

EXPLANATION

58 Number of samples

a Distributions associated

with the same letter

are not significantly

(p<0.05) different

TOTAL AMMONIA PLUS ORGANIC NITROGEN

0.0

0.2

0.4

0.6

0.8

1.0

63

5

5

6

a

a

a

a

NITRITE PLUS NITRATE

0.00

0.05

0.10

0.15

0.20

0.25

0.30

0.35

63

5

5 a a 6

b a

TOTAL NITROGEN

0.0

0.2

0.4

0.6

0.8

1.0

Maumelle

River

Reece

Creek

Yount

Creek

Bringle

Creek

63 5 5

6

a

a a

a

ORTHOPHOSPHORUS

0.000

0.005

0.010

0.015

0.020

63

4

5

6

a a a

b

TOTAL PHOSPHORUS

0.00

0.02

0.04

0.06

0.08

63

5

5 6

a

a

a a

SUSPENDED SEDIMENT

0

20

40

60

80

100

Maumelle

River

Reece

Creek

Yount

Creek

Bringle

Creek

5

63

4

4

a

a

a a
Water-Quality Assessment 31

Nutrients and dissolved organic carbon concentrations for 

the Maumelle River generally varied seasonally but remained 

fairly uniform from 1991 through 2003 (fig. 38). However, 

samples collected from 2001 through 2003 yielded slightly 

higher nitrogen and dissolved organic carbon concentrations 

and slightly lower total phosphorus concentrations than previous years. 

Concentrations of suspended sediment remained fairly 

uniform at the Maumelle River for the entire sample period, 

although higher concentrations were measured periodically 

during high-flow events (fig. 38). Suspended-sediment concentrations from samples collected at the inflow sites generally 

were greatest at Bringle Creek (from samples collected during 

high-flow events) and lowest at the Maumelle River (fig. 37). 

However, 10 percent of the samples collected at the Maumelle 

River had suspended-sediment concentrations that were greater 

than concentrations at the other inflow sites. 

Fecal indicator bacteria are measures of the sanitary quality of water and are correlated to the presence of water-borne 

pathogens (Hem, 1989). Sources of fecal indicator bacteria can 

include septic tanks; animal wastes from feedlots, barnyards, 

and pastures; and manure application areas. Concentrations of 

fecal coliform bacteria measured in the Maumelle River ranged 

from less than 1 to 4,900 colonies per 100 mL, with a median 

concentration of 120 colonies per 100 mL. Bringle, Yount, and 

Reece Creeks had greater concentrations of fecal coliform bacteria with median values of 120, 370, and 842 colonies per 100 

mL, respectively. Bringle and Reece Creeks had greater median 

concentrations of fecal streptococci than the Maumelle River, 

and Yount Creek had the least median fecal streptococci concentration (fig. 39). 

Figure 38. Time series of nutrient, dissolved organic carbon, and suspended-sediment concentrations for the Maumelle River at Williams Junction, Arkansas, 1991 through 2003.

SUSPENDED SEDIMENT

DATE

Jan-92 Jan-94 Jan-96 Jan-98 Jan-00 Jan-02 Jan-04

0

40

80

120

160

200

DISSOLVED ORGANIC CARBON

Jan-92 Jan-94 Jan-96 Jan-98 Jan-00 Jan-02 Jan-04

0

2

4

6

8

10

12

14

16

TOTAL PHOSPHORUS

Jan-92 Jan-94 Jan-96 Jan-98 Jan-00 Jan-02 Jan-04

CONCENTRATION, IN

MILLIGRAMS PER LITER

AS PHOSPHORUS

CONCENTRATION, IN

MILLIGRAMS PER LITER

AS CARBON 0.00

0.02

0.04

0.06

0.08

0.10

0.12

ORTHOPHOSPHORUS

DATE

Jan-92 Jan-94 Jan-96 Jan-98 Jan-00 Jan-02 Jan-04

CONCENTRATION, IN

MILLIGRAMS PER LITER

AS PHOSPHORUS 0.000

0.005

0.010

0.015

0.020

0.025

0.030

TOTAL AMMONIA PLUS ORGANIC NITROGEN

Jan-92 Jan-94 Jan-96 Jan-98 Jan-00 Jan-02 Jan-04

0.0

0.2

0.4

0.6

0.8

1.0

1.2

NITRITE PLUS NITRATE

Jan-92 Jan-94 Jan-96 Jan-98 Jan-00 Jan-02 Jan-04

CONCENTRATION, IN MILLIGRAMS PER LITER AS NITROGEN

0.00

0.05

0.10

0.15

0.20

0.25

TOTAL NITROGEN

Jan-92 Jan-94 Jan-96 Jan-98 Jan-00 Jan-02 Jan-04

0.0

0.2

0.4

0.6

0.8

1.0

1.2

EXPLANATION

LOCALLY WEIGHTED SMOOTH LINE (LOWESS)

SAMPLE CONCENTRATION

SAMPLE CONCENTRATION BELOW REPORTING LIMIT

CONCENTRATION, IN

MILLIGRAMS PER LITER
32 Water-Quality Assessment of Lakes Maumelle and Winona, Arkansas, 1991 Through 2003

Figure 39. Distribution of fecal indicator bacteria concentrations for four inflow sites to Lake Maumelle. BACTERIA CONCENTRATION, IN COLONIES PER 100 MILLILITERS

0

2000

4000

6000

8000

10000

12000

14000

10th percentile

25th percentile

50th percentile

75th percentile

90th percentile

Maumelle River Bringle Creek Yount Creek Reece Creek

FECAL

STREPTOCOCCI

FECAL

COLIFORMS

FECAL

STREPTOCOCCI

FECAL

COLIFORMS

FECAL

STREPTOCOCCI

FECAL

COLIFORMS

FECAL

STREPTOCOCCI

FECAL

COLIFORMS

,

,

,

,

,

,

,

EXPLANATION

65

65

5

5

5

5

6

6

6 Number of samples

a Distributions associated

with the same letter

are not significantly

(p<0.05) different

a

a a

a a a a a

Loads and Yields of Nutrients, Dissolved Organic Carbon, and

Suspended Sediment

Estimated annual loads of nutrients, dissolved organic carbon, and suspended sediment for the Maumelle River varied 

from 1991 through 2003 (fig. 40 and table 2). Because loads are 

a function of streamflow, periods of higher streamflow generally produced higher loads. The greatest annual loads occurred 

in 1991 and the least annual loads occurred in 2000. Annual 

total nitrogen loads ranged from 18,000 kg/yr in 2000 to 46,500 

kg/yr in 1991, and total phosphorus loads ranged from 822 kg/

yr in 2000 to 1,960 kg/yr in 1991. The ratio of annual total nitrogen load to total phosphorus load for the Maumelle River 

ranged from 23 to 24 indicating that loading of nutrients entering Lake Maumelle are phosphorus limited (Redfield, 1958; 

Wetzel, 2001). Total ammonia plus organic nitrogen loads were 

approximately 17 times the nitrite plus nitrate loads and composed most of the total nitrogen loads. Dissolved organic carbon 

loads followed similar trends as the nutrients with loads ranging 

from 170,000 kg/yr in 2000 to 431,000 kg/yr in 1991. Annual 

suspended-sediment loads ranged from 1,020,000 kg/yr in 2000 

to 2,870,000 in 1991 (fig. 40, table 2).

Estimated loads differed seasonally with the highest daily 

loads in the winter and fall and the lowest daily loads in the 

summer for the Maumelle River for 1991 through 2003 (fig. 

41). Average daily nitrogen loads in the winter were approximately 27 (nitrite plus nitrate) to 38 (total nitrogen) times the 

average daily loads estimated for the summer. Average daily 

total phosphorus loads for the winter were 33 times the average 

daily loads for the summer. Similarly, daily dissolved organic 

carbon loads were 38 times higher in the winter than in the summer, and suspended-sediment loads were 48 times higher in the 

winter than in summer.

Annual nutrient yields computed for the Maumelle River 

(table 2) were compared to 82 sites representative of undeveloped basins identified across the Nation including two sites in 

Arkansas (Clark and others, 2000) and to the Illinois River 

south of Siloam Springs, Arkansas, which is representative of a 

developed basin (Green and Haggard, 2001) (fig. 42). The mean 

annual yield of nitrite plus nitrate for the undeveloped sites was 

twice the yield for the Maumelle River while the mean annual 

total nitrogen yield for the Maumelle River was 2.8 times 

greater than for the undeveloped sites. Orthophosphorus and 

total phosphorus yields for the Maumelle River were similar to 

the yields for the undeveloped sites. Mean annual yields for the 

Illinois River (Green and Haggard, 2001) for all nutrients were 

substantially greater than the yields computed for the Maumelle 

River. The mean annual yield of nitrite plus nitrate for the Illinois River was 79 times greater than the yield for the Maumelle 

River, and mean total nitrogen yield for the Illinois River was 6 

times greater than the yield for the Maumelle River. Mean 

annual yields of orthophosphorus and total phosphorus for the 

Illinois River were 50 times and 17 times greater than the yields 

for the Maumelle River, respectively. 
 Water-Quality Assessment 33

Figure 40. Annual nutrient, dissolved organic carbon, and suspended-sediment loads estimated for the Maumelle River at Williams Junction,

Arkansas, 1991 through 2003.

ANNUAL LOAD, IN

KILOGRAMS PER

YEAR AS CARBON ANNUAL LOAD, IN KILOGRAMS PER YEAR AS PHOSPHORUS

ORTHOPHOSPHORUS

0

1991199219931994199519961997199819992000200120022003

100

200

300

400

ANNUAL LOAD, IN KILOGRAMS PER YEAR AS NITROGEN

NITRITE PLUS NITRATE

0

1991199219931994199519961997199819992000200120022003

500

1000

1500

2000

2500

ESTIMATED ANNUAL LOAD

LOCALLY WEIGHTED SMOOTH LINE (LOWESS)

EXPLANATION

TOTAL AMMONIA PLUS ORGANIC NITROGEN

0

1991199219931994199519961997199819992000200120022003

10000

20000

30000

40000

50000 ,

,

,

,

,

,

,

,

TOTAL NITROGEN

YEAR

0

1991199219931994199519961997199819992000200120022003

10000

20000

30000

40000

50000

,

,

,

,

,

,

TOTAL PHOSPHORUS

0

1991199219931994199519961997199819992000200120022003

500

1000

1500

2000

2500 ,

,

,

,

DISSOLVED ORGANIC CARBON

0

1991199219931994199519961997199819992000200120022003

100000

200000

300000

400000

500000 ,

,

,

,

,

,

ANNUAL LOAD, IN

KILOGRAMS PER YEAR, ,

, ,

, ,

, ,

, ,

, ,

,

SUSPENDED SEDIMENT

YEAR

0

1991199219931994199519961997199819992000200120022003

500000

1000000

1500000

2000000

2500000

3000000

3500000
Table 2. Estimated annual loads and yields for the Maumelle River at Williams Junction, Arkansas, 1991 through 2003. [kg/yr, kilograms per year; SD, standard deviation; kg/yr/km2, kilograms per year per square kilometer; N, nitrogen; P, phosphorus; C, carbon] Year Total ammonia plus organic nitrogen as N Nitrite plus nitrate as N Total nitrogen as N Orthophosphorus as P Total phosphorus as P Dissolved organic carbon as 

Load (kg/yr) (+/-SD) Yield (kg/yr/ km2) Load (kg/yr) (+/-SD) Yield (kg/yr/ km2) Load (kg/yr) (+/-SD) Yield (kg/yr/ km2) Load (kg/yr) (+/-SD) Yield (kg/yr/ km2) Load (kg/yr) (+/-SD) Yield (kg/yr/ km2) Load (kg/yr) (+/-SD) Yield (kg/yr/ km2) 

1991 39,600+/-140 332 2,280+/-20 19 46,500+/-185 389 352+/-4.0 2.9 1,960+/-14 16 431,000+/-2,093 3,610 1992 16,500+/-59 138 1,020+/-9 9 18,900+/-75 158 146+/-1.6 1.2 822+/-5.0 7 174,000+/-738 1,460 1993 31,600+/-112 265 1,880+/-17 16 36,600+/-145 307 280+/-3.1 2.3 1,570+/-10 13 338,000+/-1,529 2,830 1994 29,700+/-106 249 1,790+/-16 15 34,200+/-136 287 263+/-2.9 2.2 1,480+/-9.4 12 315,000+/-1,307 2,640 1995 16,600+/-60 139 1,040+/-9 7 19,000+/-77 159 147+/-1.6 1.2 832+/-4.9 7 173,000+/-702 1,450 1996 24,000+/-85 201 1,460+/-13 12 27,600+/-109 231 213+/-2.3 1.8 1,200+/-7.5 10 254,000+/-1,088 2,130 1997 24,700+/-88 207 1,480+/-13 12 28,600+/-113 239 219+/-2.4 1.8 1,230+/-8.0 10 263,000+/-1,169 2,210 1998 29,900+/-106 251 1,760+/-16 15 34,900+/-138 292 265+/-3.0 2.2 1,480+/-10 12 323,000+/-1,507 2,700 1999 21,200+/-75 178 1,280+/-11 11 25,500+/-97 205 188+/-2.1 1.6 1,050+/-6.8 9 226,000+/-996 1,890 2000 16,400+/-60 138 834+/-9 7 18,600+/-76 156 145+/-1.6 1.2 822+/-4.7 7 170,000+/-673 1,420 2001 24,400+/-87 205 1,040+/-13 12 28,700+/-115 241 217+/-2.4 1.8 1,210+/-8.6 10 267,000+/-1,330 2,240 2002 24,100+/-85 202 1,430+/-13 12 28,000+/-111 234 214+/-2.4 1.8 1,200+/-7.9 10 258,000+/-1,165 2,160 2003 28,300+/-100 237 1,650+/-15 14 33,100+/-131 277 251+/-2.8 2.1 1,400+/-9.7 12 306,000+/-1,455 2,570 Mean 25,166 211 1,503 13 29,170 244 223 1.9 1,249 10 269,175 2,254 Median 24,458 205 1,465 12 28,572 239 217 1.8 1,208 10 263,370 2,260 
 Water-Quality Assessment 35

Figure 41. Seasonal nutrient, dissolved organic carbon, and suspended-sediment loads estimated for the Maumelle River at Williams Junction,

Arkansas, 1991 through 2003.

SPRING SUMMER FALL WINTER

0

200

400

600

800

1000

1200

1400

1600

DISSOLVED ORGANIC CARBON

SPRING SUMMER FALL WINTER

MEAN LOAD,IN

KILOGRAMS PER DAY,

AS NITROGEN

MEAN LOAD,IN

KILOGRAMS PER DAY,

AS PHOSPHORUS

0

20

40

60

80

100

120

140

160

180

TOTAL AMMONIA PLUS ORGANIC NITROGEN

NITRITE PLUS NITRATE

TOTAL NITROGEN

SPRING SUMMER FALL WINTER

0

2

4

6

8

ORTHOPHOSPHORUS

TOTAL PHOSPHORUS

SPRING SUMMER FALL WINTER

0

2000

4000

6000

8000

10000

SUSPENDED SEDIMENT

,

,

,

,

,

,

,

,

,

a

a

b

c

a

a

b

c

a

a

b

c

a

a

b

c

EXPLANATION

DISTRIBUTIONS ASSOCIATED WITH THE SAME LETTER

ARE NOT SIGNIFICANTLY (p<0.05) DIFFERENT

a

MEAN LOAD,IN

KILOGRAMS PER DAY,

AS CARBON

MEAN LOAD,IN

KILOGRAMS PER DAY
36 Water-Quality Assessment of Lakes Maumelle and Winona, Arkansas, 1991 Through 2003

Figure 42. Annual nutrient yields for the Maumelle River at Williams Junction, Arkansas, Alum Fork Saline River near Reform, Arkansas, and

selected other stream basins. MEAN ANNUAL YIELD, IN KILOGRAMS PER YEAR, PER SQUARE KILOMETER

1

10

100

1000

10000

ALUM FORK SALINE RIVER NEAR REFORM, ARKANSAS (1991-2003, MEAN)

MAUMELLE RIVER AT WILLIAMS JUNCTION, ARKANSAS (1991-2003, MEAN)

NATIONAL UNDEVELOPED BASINS (1990-1995, MEAN)

NORTH SYLAMORE CREEK, ARKANSAS (1990-1995, MEAN)

COSSATOT RIVER, ARKANSAS (1990-1995, MEAN)

ILLINOIS RIVER SOUTH OF SILOAM SPRINGS, ARKANSAS (1997-1999, MEAN)

NITRITE PLUS NITRATE

AS NITROGEN

TOTAL NITROGEN

AS NITROGEN

ORTHOPHOSPHORUS

AS PHOSPHORUS

TOTAL PHOSPHORUS

AS PHOSPHORUS

0.1

1

10

100

1000

EXPLANATION

,

,

,

Flow-Weighted Concentrations of Nutrients, Dissolved Organic 

Carbon, and Suspended Sediment

Flow-weighted concentrations computed for the Maumelle 

River did not vary substantially on an annual basis (table 3). 

Total ammonia plus organic nitrogen flow-weighted concentrations ranged from 0.46 to 0.50 mg/L as nitrogen, nitrite plus 

nitrate flow-weighted concentrations were consistently 0.029 

mg/L as nitrogen, and total nitrogen flow-weighted concentrations ranged from 0.52 to 0.59 mg/L as nitrogen. Orthophosphorus flow-weighted concentrations were consistently 0.004 mg/

L as phosphorus, and total phosphorus concentrations ranged 

from 0.023 to 0.025 mg/L as phosphorus. Dissolved organic 

carbon flow-weighted concentrations ranged from 4.74 to 5.48 

mg/L as carbon with a mean of 5.15 mg/L as carbon. Suspended-sediment flow-weighted concentrations ranged from 

28.4 to 37.2 mg/L with a mean of 32.9 mg/L. 

The flow-weighted concentrations computed for the 

Maumelle River also were compared to 82 undeveloped sites 

identified across the Nation including 2 sites in Arkansas (Clark 

and others, 2000) and to the Illinois River south of Siloam 

Springs, Arkansas, which is representative of a developed basin 

(Green and Haggard, 2001) (fig. 43). The mean nitrite plus 

nitrate flow-weighted concentration for undeveloped sites was 

more than 5 times greater than mean flow-weighted concentration computed for the Maumelle River. However, the mean total 

nitrogen flow-weighted concentration for the Maumelle River 

was similar to the mean concentration for the undeveloped 

basins. The mean orthophosphorus flow-weighted concentration for undeveloped basins was 3.8 times greater than for the 

Maumelle River, and the mean total phosphorus flow-weighted 

concentrations for the undeveloped basins was slightly more 

than the flow-weighted concentrations for the Maumelle River. 

The mean nitrite plus nitrate flow-weighted concentration for 

the Illinois River was 83 times the mean concentration for the 

Maumelle River. The mean total nitrogen flow-weighted concentration for the Illinois River was more than 6 times greater 

than the concentrations for the Maumelle River. The mean 

orthophosphorus and total phosphorus flow-weighted concentrations were 55 times and 17 times greater, respectively, than 

the mean flow-weighted concentrations for the Maumelle 

River. 

Lake Winona

Samples were collected at the main inflow to Lake 

Winona, the Alum Fork Saline River, from 1991 through 2003 

(excluding 2001). This section summarizes the constituent concentrations and presents the estimated annual and seasonal 

loads, and computed yields and flow-weighted concentrations 

for the Alum Fork Saline River for the period.
 Water-Quality Assessment 37

Figure 43. Annual flow-weighted nutrient concentrations for the Maumelle River at Williams Junction, Arkansas, Alum Fork Saline River near

Reform, Arkansas, and selected other stream basins.

Table 3. Annual flow-weighted concentrations computed for the Maumelle River at Williams Junction, Arkansas, 1991 through 2003.

[Concentrations are in milligrams per liter; N, nitrogen; P, phosphorus; C, carbon]

Year

Total

ammonia

plus organic

nitrogen

as N

Nitrite

plus

 nitrate

as N

Total

 nitrogen

as N

Orthophosphorus

as P

Total

 phosphorus

as P

Dissolved

 organic

carbon

as C

Suspended

sediment

1991 0.50 0.029 0.59 0.004 0.025 5.45 36.2

1992 0.47 0.029 0.54 0.004 0.023 4.96 31.2

1993 0.49 0.029 0.56 0.004 0.024 5.21 33.5

1994 0.48 0.029 0.55 0.004 0.024 5.10 32.1

1995 0.46 0.029 0.53 0.004 0.023 4.82 29.2

1996 0.48 0.029 0.55 0.004 0.024 5.03 31.6

1997 0.48 0.029 0.56 0.004 0.024 5.16 32.8

1998 0.49 0.029 0.58 0.004 0.024 5.32 34.8

1999 0.48 0.029 0.56 0.004 0.024 5.12 32.6

2000 0.46 0.029 0.52 0.004 0.023 4.74 28.4

2001 0.50 0.029 0.59 0.004 0.025 5.48 37.2

2002 0.49 0.029 0.57 0.004 0.024 5.22 33.5

2003 0.50 0.029 0.58 0.004 0.025 5.38 35.4

Mean 0.48 0.029 0.56 0.004 0.024 5.15 32.9

Median 0.48 0.029 0.56 0.004 0.024 5.16 32.8 FLOW-WEIGHTED CONCENTRATION, IN MILLIGRAMS PER LITER

0.001

0.01

0.1

1

10

ALUM FORK SALINE RIVER NEAR REFORM, ARKANSAS (1991-2003, MEAN)

MAUMELLE RIVER AT WILLIAMS JUNCTION, ARKANSAS (1991-2003, MEAN)

NATIONAL UNDEVELOPED BASINS (1990-1995, MEAN)

NORTH SYLAMORE CREEK, ARKANSAS (1990-1995, MEAN)

COSSATOT RIVER, ARKANSAS (1990-1995, MEAN)

ILLINOIS RIVER SOUTH OF SILOAM SPRINGS, ARKANSAS (1997-1999, MEAN)

NITRITE PLUS NITRATE

AS NITROGEN

TOTAL NITROGEN

AS NITROGEN

ORTHOPHOSPHORUS

AS PHOSPHORUS

TOTAL PHOSPHORUS

AS PHOSPHORUS

0.0001

0.001

0.01

0.1

1

EXPLANATION
38 Water-Quality Assessment of Lakes Maumelle and Winona, Arkansas, 1991 Through 2003

Constituent Concentrations

Nutrient and dissolved organic carbon concentrations 

measured on the Alum Fork Saline River (fig. 44) generally 

were less than concentrations measured at the Maumelle River 

(fig. 37). Total ammonia plus organic nitrogen, nitrite plus 

nitrate, and total nitrogen had median concentrations of 0.100, 

0.012, and 0.204 mg/L as nitrogen, respectively, for 1991 

through 2003. Total phosphorus had a median concentration of 

0.008 mg/L as phosphorus, and orthophosphorus was usually 

near or below laboratory detection limits from 1991 through 

2003. Dissolved organic carbon concentrations had a median 

concentration of 2.4 mg/L as carbon, which was slightly less 

than the median concentration measured at the Maumelle River. 

The greatest concentrations of nutrients and dissolved organic 

carbon for the Alum Fork Saline River generally were measured 

in 1995 and 1996, but no noticeable trend in concentration was 

observed over the entire period of 1991 through 2003 (fig. 45).

Similar to the nutrient concentrations, suspended-sediment 

concentrations measured at the Alum Fork Saline River were 

less than suspended-sediment concentrations measured at the 

Maumelle River. The median suspended-sediment concentration at the Alum Fork was 9.00 mg/L, which is approximately 

28 percent less than the median concentration measured at the 

Maumelle River (12.5 mg/L) for 1991 through 2003 (figs. 37 

and 44). The greatest concentrations of suspended sediment 

were measured in 1995 and 1996, and the lowest concentrations 

were measured in 1991 and 1992 (fig. 45). No noticeable trend 

in concentration was observed over the entire period of 1991 

through 2003.

Concentrations of fecal streptococci bacteria measured at 

the Alum Fork Saline River were similar to concentrations measured at the Maumelle River and concentrations of fecal 

coliform were less. Concentrations of fecal streptococci bacteria had a median concentration of 230 colonies per 100 mL (fig. 

44), compared to a median concentration of 265 colonies per 

100 mL at the Maumelle River. Fecal coliform bacteria concentrations had a median of 50 colonies per 100 mL, which was 

approximately half the median concentration measured at the 

Maumelle River (110 colonies per 100 mL) (fig. 39).

Figure 44. Distribution of nutrient, dissolved organic carbon, suspended-sediment, and fecal indicator bacteria concentrations for the Alum Fork Saline 

River near Reform, Arkansas, 1991 through 2003. CONCENTRATION, IN MILLIGRAMS PER LITER AS NITROGEN

CONCENTRATION, IN MILLIGRAMS

PER LITER AS PHOSPHORUS

0.0

0.2

0.4

0.6

0.8

10th percentile

25th percentile

50th percentile

75th percentile

90th percentile

TOTAL

NITROGEN

NITRITE

PLUS

NITRATE

TOTAL

AMMONIA

PLUS ORGANIC

NITROGEN

EXPLANATION

61

61

61

0.00

0.01

0.02

0.03

0.04

TOTAL

PHOSPHORUS

ORTHOPHOSPHORUS

61

61

BACTERIA CONCENTRATION, IN

COLONIES PER 100 MILLILITERS

0

2000

4000

6000

8000

FECAL

STREPTOCOCCI

FECAL

COLIFORM

,

61

61

CONCENTRATION, IN MILLIGRAMS PER LITER

0

10

20

30

40

50

54

CONCENTRATION, IN MILLIGRAMS

PER LITER AS CARBON

0

2

4

6

8

10

12

14

SUSPENDED

SEDIMENT

DISSOLVED

ORGANIC

CARBON

,

,

,

57 Number of samples

61
Water-Quality Assessment 39

Figure 45. Time series of nitrogen, phosphorus, dissolved organic carbon, and suspended-sediment concentrations for the Alum Fork Saline River near 

Reform, Arkansas, 1991 through 2003.

SUSPENDED SEDIMENT

DATE

Jan-92 Jan-94 Jan-96 Jan-98 Jan-00 Jan-02 Jan-04

0

20

40

60

80

100

DISSOLVED ORGANIC CARBON

Jan-92 Jan-94 Jan-96 Jan-98 Jan-00 Jan-02 Jan-04

0

5

10

15

20

25

TOTAL PHOSPHORUS

Jan-92 Jan-94 Jan-96 Jan-98 Jan-00 Jan-02 Jan-04

CONCENTRATION, IN

MILLIGRAMS PER LITER

AS PHOSPHORUS

CONCENTRATION, IN

MILLIGRAMS PER LITER

AS CARBON

CONCENTRATION, IN

MILLIGRAMS PER LITER 0.00

0.02

0.04

0.06

0.08

0.10

0.12

ORTHOPHOSPHORUS

DATE

Jan-92 Jan-94 Jan-96 Jan-98 Jan-00 Jan-02 Jan-04

CONCENTRATION, IN

MILLIGRAMS PER LITER

AS PHOSPHORUS 0.000

0.005

0.010

0.015

0.020

0.025

0.030

TOTAL AMMONIA PLUS ORGANIC NITROGEN

Jan-92 Jan-94 Jan-96 Jan-98 Jan-00 Jan-02 Jan-04

0.0

0.4

0.8

1.2

1.6

NITRITE PLUS NITRATE

Jan-92 Jan-94 Jan-96 Jan-98 Jan-00 Jan-02 Jan-04

CONCENTRATION, IN MILLIGRAMS PER LITER AS NITROGEN 0.0

0.1

0.2

0.3

0.4

TOTAL NITROGEN

Jan-92 Jan-94 Jan-96 Jan-98 Jan-00 Jan-02 Jan-04

0.0

0.4

0.8

1.2

1.6

EXPLANATION

LOCALLY WEIGHTED SMOOTH LINE (LOWESS)

SAMPLE CONCENTRATION

SAMPLE CONCENTRATION BELOW REPORTING LIMIT

Loads and Yields of Nutrients, Dissolved Organic Carbon, and 

Suspended Sediment

Annual loads estimated for the Alum Fork Saline River 

(fig. 46 and table 4) varied with time and were similar to loads 

estimated for the Maumelle River (fig. 40 and table 2). Nutrients, dissolved organic carbon, and suspended sediment at the 

Alum Fork Saline River had the greatest annual loads in 1991 

and the least loads in 1995. Estimated annual total nitrogen 

loads ranged from 13,700 in 1995 to 41,400 kg/yr in 1991 with 

a mean load of 20,243 kg/yr for the period of 1991 through 

2003. The mean annual total nitrogen load for the Alum Fork 

Saline River was approximately 30 percent less than the loads 

for the Maumelle River. Total ammonia plus organic nitrogen 

accounted for most of the annual nitrogen load with a mean of 

18,072 kg/yr. The annual mean nitrite plus nitrate load was only 

1,307 kg/yr. The annual total phosphorus load for the Alum 

Fork Saline River ranged from 468 kg/yr in 1995 to 1,380 kg/yr 

in 1991 with a mean load of 685 kg/yr. The ratios of annual total 

nitrogen load to total phosphorus load for the Alum Fork River 

ranged from 29 to 30, indicating that the nutrient loads entering 

Lake Winona are phosphorus limited (Redfield, 1958; Wetzel, 

2001). The mean annual load of orthophosphorus was 181 kg/

yr. Total phosphorus loads computed for the Alum Fork Saline 

River were half the phosphorus loads for the Maumelle River. 

The mean annual dissolved organic carbon load estimated for 

the Alum Fork Saline River was 257,895 kg/yr, which was 

slightly less than the mean dissolved organic carbon load estimated for the Maumelle River. The mean estimated suspendedsediment load was 705,729 kg/yr, which was approximately 60 

percent less than the suspended-sediment load estimated for the 

Maumelle River (figs. 40 and 46 and tables 2 and 4). 

Seasonal loads estimated for the Alum Fork Saline River 

(fig. 47) demonstrated a similar pattern to seasonal loads for the 

Maumelle River (fig. 41). The greatest loads generally occurred 

in the winter and the least loads occurred in the summer. Nutrient and suspended-sediment loads generally were more than 33 

times greater in the winter than in the summer and dissolved 

organic carbon loads were 42 times greater in the winter than in 

the summer.

Annual yields of nutrients and dissolved organic carbon 

computed for the Alum Fork Saline River (table 4) were slightly 

greater than yields for the Maumelle River and suspended-sediment yields were less for the period of 1991 through 2003 
Table 4. Estimated annual loads and yields for the Alum Fork Saline River near Reform, Arkansas, 1991 through 2003. [kg/yr, kilograms per year; SD, standard deviation; kg/yr/km2, kilograms per year per square kilometer; N, nitrogen; P, phosphorus; C, carbon] Year Total ammonia plus organic nitrogen as N Nitrite plus nitrate as N Total nitrogen as N Orthophosphorus as P Total phosphorus as P Dissolved organic carbon as C Suspe

Load (kg/yr) (+/-SD) Yield (kg/yr km2) Load (kg/yr) (+/-SD) Yield (kg/yr/ km2) Load (kg/yr) (+/-SD) Yield (kg/yr/ km2) Load (kg/yr) (+/-SD) Yield (kg/yr/ km2) Load (kg/yr) (+/-SD) Yield (kg/yr/ km2) Load (kg/yr) (+/-SD) Yield (kg/yr/ km2) Load (kg/yr

(+/-SD

1991 35,700+/-184 511 2,510+/-34 36 41,400+/-221 593 349+/-5.1 5 1,380+/-15 20 563,000+/-2,478 8,000 1,450,000+/1992 13,000+/-60 186 954+/-12 14 14,400+/-68 206 132+/-1.7 2 488+/-4.5 7 179,000+/-802 2,560 500,000+/-21993 21,500+/-103 307 1,540+/-20 22 24,300+/-121 348 214+/-2.9 3 819+/-8.1 12 316,000+/-1,400 4,520 848,000+/-51994 19,800+/-92 283 1,440+/-18 21 21,900+/-105 313 199+/-2.7 3 745+/-6.9 11 273,000+/-1,227 3,900 763,000+/-41995 12,400+/-57 178 911+/-11 13 13,700+/-66 197 126+/-1.7 2 468+/-4.3 7 170,000+/-768 2,440 479,000+/-21996 19,500+/-90 279 1,420+/-18 20 21,700+/-104 310 196+/-2.6 3 736+/-6.9 11 271,000+/-1,214 3,880 755,000+/-41997 17,500+/-82 250 1,270+/-16 18 19,500+/-94 279 176+/-2.4 3 662+/-6.2 9 245,000+/-1,097 3,500 680,000+/-41998 18,000+/-84 257 1,310+/-16 19 20,000+/-96 286 181+/-2.4 3 679+/-6.4 10 249,000+/-1,121 3,570 696,000+/-41999 14,000+/-65 201 1,030+/-13 15 15,600+/-74 223 142+/-1.9 2 529+/-4.9 8 194,000+/-872 2,780 542,000+/-32000 13,200+/-60 190 975+/-12 14 14,500+/-69 208 134+/-1.8 2 496+/-4.5 7 178,000+/-803 2,540 506,000+/-22001 19,800+/-96 283 1,420+/-18 20 22,500+/-113 322 196+/-2.7 3 757+/-7.5 11 294,000+/-1,302 4,210 785,000+/-52002 14,500+/-67 207 1,060+/-13 15 16,000+/-76 228 147+/-1.9 2 544+/-5.0 8 196,000+/-888 2,800 556,000+/-32003 15,800+/-74 226 1,150+/-14 16 17,700+/-85 253 159+/-2.1 2 599+/-5.7 9 224,000+/-999 3,200 616,000+/-3Mean 18,072 258 1,307 19 20,243 289 181 2.6 685 10 257,895 3,688 705,729 Median 17,505 250 1,271 18 19,494 279 176 2.5 662 9 244,646 3,498 679,550 
 Water-Quality Assessment 41

Figure 46. Annual nutrient, dissolved organic carbon, and suspended-sediment loads estimated for the Alum Fork Saline River near Reform, Arkansas, 

1991 through 2003.

ANNUAL LOAD, IN KILOGRAMS

PER YEAR AS PHOSPHORUS

TOTAL PHOSPHORUS

0

1991199219931994199519961997199819992000200120022003

200

400

600

800

1,000

1,200

1,400

1,600

ORTHOPHOSPHORUS

0

1991199219931994199519961997199819992000200120022003

100

200

300

400

ANNUAL LOAD, IN KILOGRAMS PER YEAR AS NITROGEN

ESTIMATED ANNUAL LOAD

LOCALLY WEIGHTED SMOOTH LINE (LOWESS)

EXPLANATION

AMMONIA PLUS ORGANIC NITROGEN

0

1991199219931994199519961997199819992000200120022003

10,000

20,000

30,000

40,000

NITRITE PLUS NITRATE

0

1991199219931994199519961997199819992000200120022003

500

1,000

1,500

2,000

2,500

3,000

DISSOLVED ORGANIC CARBON

ANNUAL LOAD, IN

1991199219931994199519961997199819992000200120022003

KILOGRAMS PER YEAR

AS CARBON

0

100,000

200,000

300,000

400,000

500,000

600,000

TOTAL NITROGEN

YEAR

0

1991199219931994199519961997199819992000200120022003

10,000

20,000

30,000

40,000

50,000

SUSPENDED SEDIMENT

YEAR

1991199219931994199519961997199819992000200120022003

ANNUAL LOAD, IN

KILOGRAMS PER YEAR

0

200,000

400,000

600,000

800,000

1,000,000

1,200,000

1,400,000

1,600,000
42 Water-Quality Assessment of Lakes Maumelle and Winona, Arkansas, 1991 Through 2003

Figure 47. Seasonal nutrient, dissolved organic carbon, and suspended-sediment loads estimated for the Alum Fork Saline River, Arkansas, 1991 

through 2003.

SPRING SUMMER FALL WINTER

MEAN LOAD,IN

KILOGRAMS PER DAY,

AS NITROGEN

MEAN LOAD,IN

KILOGRAMS PER DAY,

AS PHOSPHORUS

0

20

40

60

80

100

120

TOTAL AMMONIA PLUS ORGANIC NITROGEN

NITRITE PLUS NITRATE

TOTAL NITROGEN

SPRING SUMMER FALL WINTER

0

1

2

3

4

DISSOLVED PHOSPHORUS

ORTHOPHOSPHORUS

SPRING SUMMER FALL WINTER

0

500

1000

1500

2000

2500

3000

3500

SUSPENDED SEDIMENT

SPRING SUMMER FALL WINTER

0

200

400

600

800

1000

1200

DISSOLVED ORGANIC CARBON

,

,

,

,

,

,

,

,

c

a

b

a

c

a

b

a

c

a

b

a

c

a

b

a

EXPLANATION

DISTRIBUTIONS ASSOCIATED WITH THE SAME LETTER

ARE NOT SIGNIFICANTLY (p<0.05) DIFFERENT

a

MEAN LOAD,IN

KILOGRAMS PER DAY,

AS CARBON

MEAN LOAD,IN

KILOGRAMS PER DAY,
Water-Quality Assessment 43

(tables 2 and 4). The mean total nitrogen yield was 289 kg/yr/

km2

, which was slightly greater than the mean total nitrogen 

yield for the Maumelle River. The mean total phosphorus was 

10 kg/yr/km2

, which was the same as the mean total phosphorus 

yield for the Maumelle River. The mean dissolved organic 

carbon yield for the Alum Fork Saline River was 3,688 kg/yr/

km2

, approximately 1.6 times greater than the mean yield for 

the Maumelle River. The Maumelle River had a mean suspended-sediment yield that was 1.4 times the mean suspendedsediment yield for the Alum Fork Saline River. 

Annual yields of total nitrogen and phosphorus for the 

Alum Fork Saline River were greater than yields for 82 sites 

representative of undeveloped basins identified across the 

Nation including 2 sites in Arkansas (Clark and others, 2000), 

and less than yields for the Illinois River south of Siloam 

Springs, Arkansas, which is representative of a developed basin 

(Green and Haggard, 2001) (fig. 42). The mean total nitrogen 

yield for the Alum Fork Saline River was more than three times 

the mean yield for the undeveloped basins and the total phosphorus was similar to the yields for the undeveloped sites. The 

Alum Fork Saline River had a mean yield of total phosphorus 

that was approximately 6 percent of the mean yield for the Illinois River near Siloam Springs. The mean yield of total nitrogen for the Alum Fork Saline River was approximately 16 percent of the total nitrogen yield for the Illinois River. 

Flow-Weighted Concentrations of Nutrients, Dissolved Organic 

Carbon, and Suspended Sediment

Annual flow-weighted concentrations of nutrients and dissolved organic carbon (table 5) generally were the same as those 

computed for the Maumelle River (table 3). Suspended-sediment flow-weighted concentrations for the Alum Fork Saline 

River were approximately one-half those computed for the 

Maumelle River. 

The Alum Fork Saline River generally had lower flowweighted concentrations compared to the mean flow-weighted 

concentrations for undeveloped sites and substantially lower 

flow-weighted concentrations than those for the Illinois River 

south of Siloam Springs, Arkansas, representative of a developed basin (fig. 43). Flow-weighted concentrations of nitrite 

plus nitrate for the undeveloped sites were 4.7 times greater 

than the flow-weighted concentration for the Alum Fork Saline 

River, although the flow-weighted concentration of total nitrogen was slightly greater for the Alum Fork Saline River than for 

the undeveloped sites. Orthophosphorus flow-weighted concentrations for the Alum Fork Saline River were approximately 

26 percent of the flow-weighted concentrations for the undeveloped sites, and total phosphorus flow-weighted concentrations 

were approximately 50 percent of the flow-weighted concentrations for the undeveloped sites.

Table 5. Annual flow-weighted concentrations computed for the Alum Fork Saline River near Reform, Arkansas, 1991 through 2003.

[Concentrations are in milligrams per liter; N, as nitrogen; P, phosphorus; C, carbon]

Year

Total

ammonia

plus organic

nitrogen

as N

Nitrite

plus

 nitrate

as N

Total

 nitrogen

as N

Orthophosphorus

as P

Total

 phosphorus

as P

Dissolved

 organic

carbon

as C

Suspended

sediment

1991 0.49 0.034 0.57 0.005 0.019 7.70 19.8

1992 0.43 0.031 0.47 0.004 0.016 5.90 16.5

1993 0.46 0.033 0.52 0.005 0.017 6.71 18.0

1994 0.44 0.032 0.49 0.004 0.017 6.05 16.9

1995 0.43 0.032 0.48 0.004 0.016 5.92 16.6

1996 0.44 0.032 0.49 0.004 0.017 6.10 17.0

1997 0.44 0.032 0.49 0.004 0.017 6.12 17.2

1998 0.44 0.032 0.49 0.004 0.017 6.09 17.0

1999 0.44 0.032 0.48 0.004 0.016 6.02 16.8

2000 0.43 0.031 0.47 0.004 0.016 5.72 16.3

2001 0.46 0.033 0.52 0.005 0.018 6.86 18.3

2002 0.43 0.032 0.48 0.004 0.016 5.84 16.6

2003 0.44 0.032 0.50 0.004 0.017 6.27 17.3

Mean 0.44 0.032 0.50 0.004 0.017 6.26 17.3

Median 0.44 0.032 0.49 0.004 0.017 6.09 17.0
44 Water-Quality Assessment of Lakes Maumelle and Winona, Arkansas, 1991 Through 2003

Summary

Lakes Maumelle and Winona are water-supply reservoirs 

for the Little Rock and North Little Rock metropolitan areas in 

central Arkansas. In addition to water supply, the reservoirs are 

used for recreation and fish and wildlife habitat. Monitoring the 

changes in the hydrology and water quality in the basin as land 

use changes is critical to managing the resource.

The purpose of this report is to describe the hydrology and 

water quality of Lakes Maumelle and Winona and their inflows 

from data collected by the USGS in cooperation with CAW for 

calendar years 1991 through 2003. Water-quality samples were 

collected at four locations in Lake Maumelle and at three locations in Lake Winona. Samples also were collected at four 

inflow sites to Lake Maumelle and one inflow site to Lake 

Winona. Annual and seasonal loads of nutrients, dissolved 

organic carbon, and suspended sediment were estimated for the 

main inflows into Lakes Maumelle and Winona including the 

Maumelle River at Williams Junction, Arkansas, and the Alum 

Fork Saline River near Reform, Arkansas. Yields and flowweighted concentrations were calculated from estimated annual 

loads for comparison with selected undeveloped basins and one 

developed basin.

The main inflows into Lakes Maumelle and Winona, the 

Maumelle River and Alum Fork Saline River, exhibited typical 

seasonal variability in streamflow with high flows usually 

occurring in the late fall, winter, and early spring, and low or no 

flow in the summer and early fall. The mean annual streamflow 

for 1991 through 2003 for the Maumelle River at Williams 

Junction was 1.64 m3

/s and for the Alum Fork Saline River near 

Reform was 1.28 m3

/s. The highest annual mean streamflow for 

both streams occurred in 1991, and the lowest annual mean 

streamflow occurred in 1992 for the Maumelle River and 1995 

for the Alum Fork Saline River. 

Lakes Maumelle and Winona are monomictic systems, in 

which thermal stratification occurs annually during the summer 

and complete mixing occurs in the fall. Isothermal conditions 

exist throughout the winter and early spring. The distribution of 

dissolved oxygen in Lakes Maumelle and Winona exhibits seasonal changes mainly because of the thermodynamics in the 

hypolimnion of the reservoir. Dissolved-oxygen concentrations 

during the winter remain uniform and near saturation levels and 

as thermal stratification becomes established, concentrations in 

the hypolimnion decrease until summer when conditions in the 

hypolimnion are nearly anoxic (devoid of dissolved oxygen).

Water quality measured in Lakes Maumelle and Winona 

varied spatially and temporally. Although total phosphorus concentrations were significantly less in the lower ends of lakes 

than concentrations in the upper ends of the lakes, nitrogen and 

orthophosphorus concentrations did not vary significantly 

among the sampling sites on each lake. The highest concentrations of nitrogen generally were measured in 1991 and from 

1998 through 2003 at all of the sampling sites. The highest total 

phosphorus concentrations were measured from 1994 to 1996 

and from 1998 to 2001 on Lake Maumelle and from 1993 to 

1994 on Lake Winona. Total and dissolved organic carbon concentrations were similar among sites on each lake and the greatest concentrations were measured in 1996 and 1997 at all of the 

sites. The chlorophyll a concentrations varied seasonally, with 

the highest concentrations in October and November, but were 

relatively uniform spatially and annually in Lakes Maumelle 

and Winona for 1991 through 2003. Water clarity was greater at 

the lower ends of the lakes than the upper ends. Secchi depth 

varied seasonally, with the greatest depth from July to September and the least depth during October through December, 

although there was no apparent trend in Secchi depth over the 

entire sampling period. 

The TSI calculated from near-surface concentrations of 

total phosphorus and chlorophyll a for Lakes Maumelle and 

Winona indicated that they generally were oligotrophic 

although they fluctuated in time between mesotrophic and oligotrophic conditions. 

Water-quality concentrations generally were less for the 

Alum Fork Saline River, the main inflow to Lake Winona, than 

for the Maumelle River, Bringle, Yount, and Reece Creeks, 

which flow into Lake Maumelle. Nutrient and dissolved organic 

carbon concentrations for the Maumelle and Alum Fork Saline 

Rivers remained fairly uniform from 1991 through 2003. The 

median suspended-sediment concentration at the Alum Fork 

Saline River was approximately 28 percent less than the median 

concentration measured at the Maumelle River. Suspended-sediment concentrations generally were greatest at Bringle Creek. 

Concentrations of fecal streptococci measured at the Alum Fork 

Saline River were similar to concentrations measured at the 

Maumelle River, and fecal coliforms had a median concentration for the Alum Fork Saline River that was approximately half 

the median concentration measured at the Maumelle River. 

Bringle and Reece Creeks had greater median concentrations of 

fecal coliforms and fecal streptococci than the Maumelle River, 

and Yount Creek had the least median concentration of fecal 

streptococci among all the sites although Bringle, Yount, and 

Reece Creeks were sampled only during high-flow events while 

the Maumelle and Alum Fork Saline Rivers were sampled 

mainly during base-flow conditions.

Annual loads estimated for the Maumelle River and the 

Alum Fork Saline River were similar between sites and varied 

annually and seasonally from 1991 through 2003. Annual loads 

were greatest in 1991 for the Maumelle and Alum Fork Saline 

Rivers and were the least in 2000 for the Maumelle River and in 

1995 for the Alum Fork Saline River. Estimated annual total 

nitrogen loads ranged from 18,000 to 46,500 kilograms per year 

for the Maumelle River and from 13,700 to 41,400 kilograms 

per year for the Alum Fork Saline River. Total phosphorus 

loads ranged from 822 to 1,960 kilograms per year for the 

Maumelle River and 468 to 1,380 kilograms per year for the 

Alum Fork Saline River. Estimated loads also demonstrated 

seasonal trends with the highest daily loads in the winter and 

fall and lowest daily loads in the summer for both sites.

Annual yields of nutrients and dissolved organic carbon 

computed for the Maumelle River were similar to yields for the 

Alum Fork Saline River and suspended-sediment yields were 
References 45

less for the period of 1991 through 2003. The Alum Fork Saline 

River had a mean total nitrogen yield that was slightly greater 

than the mean total nitrogen yield for Maumelle River and more 

than 3 times greater than yields for selected undeveloped sites 

across the Nation. The mean total phosphorus yield for 1991 

through 2003 for both the Maumelle and Alum Fork Saline 

River was 10 kilograms per year per square kilometer, which 

was similar to the selected undeveloped sites. The mean dissolved organic carbon yields for the Maumelle and Alum Fork 

Saline Rivers were 2,254 and 3,688 kilograms per year per 

square kilometer, respectively. The mean suspended-sediment 

yields for the Maumelle and Alum Fork Saline Rivers were 

14,486 and 10,092 kilograms per year per square kilometer, 

respectively.

Annual flow-weighted nutrient and dissolved organic carbon concentrations computed for the Maumelle and Alum Fork 

Saline Rivers were similar and suspended-sediment flowweighted concentrations for the Maumelle River were approximately twice the suspended-sediment flow-weighted concentrations for the Alum Fork Saline River. Nutrient concentrations 

for the Maumelle River and Alum Fork Saline River also were 

similar to selected undeveloped sites across the Nation.

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Galloway, J.M., and Green, W.R.—WATER-QUALITY ASSESSMENT OF LAKES MAUMELLE AND WINONA, ARKANSAS, 1991 THROUGH 2003—

U.S. Geological Survey Scientific Investigations Report 2004-5182