Cover photograph taken by Robert D. Goodrich, U.S. Geological Survey, Iowa City, Iowa.
U.S. Department of the Interior

U.S. Geological Survey

Bathymetric Mapping, Sediment 

Quality, and Water Quality of Lake 

Delhi, Iowa, 2001–02

By DOUGLAS J. SCHNOEBELEN, JASON C. MCVAY, KYMM K. BARNES, and 

KENT D. BECHER

Water-Resources Investigations Report 03–4085

Prepared in cooperation with the

IOWA WASTE REDUCTION CENTER, UNIVERSITY OF NORTHERN IOWA and the

LAKE DELHI ASSOCIATION

Iowa City, Iowa

2003
U.S. Department of the Interior

Gale A. Norton, Secretary

U.S. Geological Survey

Charles G. Groat, Director

For additional information write to: Copies of this report can be purchased from:

District Chief U.S. Geological Survey

U.S. Geological Survey Information Services

P.O. Box 1230 Building 810

400 South Clinton Box 25286, Federal Center

Iowa City, IA 52244–1230 Denver, CO 80225–0286

The use of firm, trade, and brand names in this report is for identification purposes only and does not constitute endorsement 

by the U.S. Geological Survey.
Contents III

CONTENTS

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

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

Purpose and Scope....................................................................................................................................................... 3

Acknowledgments ....................................................................................................................................................... 3

Methods of Study................................................................................................................................................................... 5

Bathymetric Mapping .................................................................................................................................................. 5

Sediment Sampling and Analysis................................................................................................................................ 6

Water-Quality Sampling and Analysis ........................................................................................................................ 7

Bathymetry, Sediment Quality, and Water Quality................................................................................................................ 8

Bathymetry .................................................................................................................................................................. 8

Sediment Quality ......................................................................................................................................................... 15

Water Quality............................................................................................................................................................... 16

Additional Water-Quality Data.................................................................................................................................... 20

Summary and Conclusions .................................................................................................................................................... 20

References ............................................................................................................................................................................. 21

Supplemental Data................................................................................................................................................................. 23

FIGURES

1–5. Maps showing:

1. Location of Lake Delhi study area and sampling sites in eastern Iowa............................................................. 4

2. Bathymetry for upstream reach of Lake Delhi .................................................................................................. 11

3. Bathymetry for upstream-middle reach of Lake Delhi...................................................................................... 12

4. Bathymetry for middle reach of Lake Delhi...................................................................................................... 13

5. Bathymetry for downstream reach of Lake Delhi ............................................................................................. 14

TABLES

1. Sediment constituents, Chemical Abstract Registry number, National Water Information System database 

code, minimum reporting level, and reporting units ............................................................................................... 7

2. Nutrient and bacteria constituents analyzed in water samples, Chemical Abstract Registry number, National 

Water Information System database code, minimum reporting level, and reporting units ..................................... 8

3. Major ions, trace elements, and pesticides analyzed in water samples, Chemical Abstract Registry number, 

National Water Information System database code, laboratory reporting level, and reporting units ..................... 9

4. Statistical summary of selected trace metal and phosphorus concentrations in bottom-sediment samples from 

Lake Delhi, eastern Iowa, September 2001, and comparison to sediment-quality guidelines................................ 15

5. Statistical summary of nutrient and bacteria concentrations in water samples from Maquoketa River, 

Lake Delhi, and tributary sites, eastern Iowa, June 2001 through June 2002, and comparison to water-quality

guidelines ................................................................................................................................................................ 17

6. Nitrate concentrations in water samples from upstream, middle, and downstream portions of Lake Delhi, 

eastern Iowa, by season, June 2001 through July 2002........................................................................................... 18

7. Total coliform and E. coli bacteria concentrations in water samples from upstream, middle, and downstream

portions of Lake Delhi, eastern Iowa, by season, June 2001 through July 2002 .................................................... 18

8. Instantaneous discharge, suspended-sediment concentrations, loads, and yields by season for Maquoketa River 

and four tributary sites, eastern Iowa, June 2001 through July 2002...................................................................... 19
IV Bathymetric Mapping, Sediment Quality, and Water Quality of Lake Delhi, Iowa, 2001–02

TABLES—Continued

9. Phosphorus and trace-element concentrations in samples from sediment cores, Lake Delhi, eastern Iowa, 

September 18, 2001 ................................................................................................................................................ 24

10. Nutrient and bacteria concentrations in water samples collected from Marquoketa River, tributary, and lake sites, 

Lake Delhi, eastern Iowa, June 2001 through July 2002........................................................................................ 26

11. Instantaneous discharge, physical properties, and suspended-sediment concentrations in water samples 

collected from Marquoketa River, tributary, and lake sites, Lake Delhi, eastern Iowa, June 2001 through 

July 2002................................................................................................................................................................. 30

12. Pesticide concentrations in water samples collected at selected sites near or at Lake Delhi, eastern Iowa, 

June 2001................................................................................................................................................................ 34

13. Major-ion and trace-metal concentrations in water samples collected from Marquoketa River, tributary, and 

lake sites, Lake Delhi, eastern Iowa, June 2001 through March 2002 ................................................................... 36

Temperature can be converted to degree Celsius (°C) or degrees Fahrenheit (°F) by the equations: 

°C = 5/9 (°F - 32) 

°F = 9/5 (°C) + 32. 

Vertical datum: Vertical coordinate information is referenced to the National Geodetic Vertical Datum of 1929

(NGVD of 29). Elevation as used in this report, refers to distance above or below NGVD of 29. NGVD of 29

can be converted to the North America Vertical Datum of 1988 (NAVD of 88) by using the National Geodetic

Survey conversion utility available at URL http://www.ngs.noaa.gov/TOOLS/vertcon.html

Horizontal datum: Horizontal datum information is referenced to the North American Datum of 1983 (NAD

of 83).

Water year: In this report, "water year" is the 12-month period, October 1 through September 30. The water

year is designated by the calendar year in which it ends. Thus, the year ending September 30, 1998, is called the

"1998 water year." 

CONVERSION FACTORS, ABBREVIATIONS, DATUMS, AND DEFINITIONS

Multiply By To obtain

acre 4,047 square meter (m2)

cubic foot (ft3) 0.02832 cubic meter (m3)

cubic foot per second (ft3/s) 0.02832 cubic meter per second (m3

/s)

foot (ft) 0.3048 meter (m)

inch (in.) 2.54 centimeter (cm)

liter (L) 0.2642 gallon (gal)

meter (m) 3.281 foot (ft)

microgram per gram (μg/g) 1.0000 x 10-6 ounce per ounce (oz/oz)

microgram per kilogram (μg/kg) 1.000 x 10-3 ounce per ounce (oz/oz)

microgram per liter (μg/L) 1.0 part per billion (ppb)

micron (μ) 3.937 x 10-5 inch (in.)

mile (mi) 1.609 kilometer (km)

milligram (mg) 0.0000353 ounce (oz)

milligram per kilogram (mg/kg) 1.0 x 10-6 ounce per ounce (oz/oz)

milligram per liter (mg/L) 1.0 part per million (ppm)

millimeter (mm) 0.03937 inch (in.)

pound (lb) 453.6 gram (g)

pound per day (lb/d) 0.4536 kilogram per day (kg/d)

pound per square mile (lb/mi2

) 0.1751 kilogram per square kilometer (kg/km2)

square mile (mi2) 2.590 square kilometer (km2)
Abstract 1

Bathymetric Mapping, Sediment Quality, and Water Quality of 

Lake Delhi, Iowa, 2001–02

By Douglas J. Schnoebelen, Jason C. McVay, Kymm K. Barnes, and Kent D. Becher

Abstract

Lake Delhi was formed in 1929 when the 

Interstate Power Company dammed the 

Maquoketa River near Delhi, Iowa, for generation 

of hydroelectric power. The resulting 450-acre 

lake became a popular area in eastern Iowa for 

boating, swimming, and fishing. Hydroelectric 

power generation ended in 1973, and lakeside residents purchased the dam to maintain the recreational opportunities of the lake. Increasing 

concerns about sediment deposition and water 

quality by lakeside residents led to a 2-year study 

that included a bathymetric survey, an assessment 

of sediment quality, and an assessment of water 

quality of Lake Delhi.

A bathymetric map of Lake Delhi was constructed using more than 300,000 data points from 

echo sounding results and GIS (geographic information system) software. Results of bathymetric 

mapping showed that the upstream reach through 

most of the upstream-middle reach of Lake Delhi 

(approximately 3 miles) from about 0.25 mile 

upstream from the Greenslades coring site 

through Clair View Acres were particularly 

affected by sedimentation, with water depths 

ranging from less than 1 foot to a few areas that 

were as much as 10 feet deep. Numerous areas in 

the upstream-most 1-mile of the lake (about 

0.25 mile upstream from the Greenslades coring 

site to just downstream from The Cedars coring 

site) had depths of only 1 to 2 feet and were 

nearly impassable by boats. The middle reach of 

Lake Delhi (an approximately 2.5-mile segment) 

from about one-half mile upstream from the 

Linden Acres coring site to just downstream from 

the Hartwick Dredge coring site was less affected 

by sedimentation with water depths from less than 

1 to 16 feet. The deepest section (26 feet) of the 

lake was near the dam.

Eleven trace metals and phosphorus were analyzed in 20 samples from seven lake-bottom sediment cores. The median and average traceelement concentrations from the sediment cores 

were less than the U.S. Environmental Protection 

Agency threshold-effects-level and probableeffects-level guidelines for toxic biological 

effects. Water-quality samples from eight sites 

(Maquoketa River, three lake sites, and four tributaries) were collected for five sampling periods 

(June 2001–July 2002). Water-quality samples 

were analyzed for physical properties (specific 

conductance, pH, temperature, turbidity, dissolved oxygen, and alkalinity), nutrients (nitrate, 

ammonia, and phosphorus), bacteria (total 

coliform and E. coli), and suspended sediment. 

Selected water samples were analyzed for major 

ions, trace elements, and pesticides.

Water-quality sampling results indicate areas 

affected by elevated nutrient and bacteria concentrations in the lake and tributary streams. The tributary streams had the highest median nitrate 

concentrations (12.1 milligrams per liter) when 

compared to median nitrate concentrations in the 

lake (8.7 milligrams per liter) or the Maquoketa 

River (10.5 milligrams per liter). The maximum 

nitrate concentrations detected for Maquoketa 

River, lake, and tributary sites were 13.5, 13.5, 

and 18.6 milligrams per liter, respectively. Nitrate 

concentrations in the late summer decreased from 
2 Bathymetric Mapping, Sediment Quality, and Water Quality of Lake Delhi, Iowa, 2001–02

the upstream (7.8 milligrams per liter) to the 

downstream (5.0 milligrams per liter) one-third of 

Lake Delhi and most likely were the result of 

uptake of nitrate by algae and aquatic biota in the 

lake. Median concentrations of total coliform and 

E. coli bacteria for the lake sites were 450 and 

17 colonies per 100 milliliters of sample, respectively. The U.S. Environmental Protection Agency 

criteria for full body contact (swimming or bathing) are 200 colonies per 100 milliliters for fecal 

bacteria and 126 colonies per 100 milliliters for 

E. coli bacteria. The highest bacteria concentrations in the lake occurred after a rain and were 

25,000 colonies per 100 milliliters total coliform 

and 1,900 colonies per 100 milliliters E. coli.

INTRODUCTION

Lake Delhi (Federally recognized as Hartwick 

Lake) was formed in 1929 when the Interstate Power 

Company dammed the Maquoketa River to build a 

hydroelectrical generating plant. The local name 

“Lake Delhi” was adopted in recognition of the nearby 

town of Delhi, Iowa. The resulting 450-acre lake 

became a popular area in eastern Iowa for boating, 

swimming, and fishing. Hydroelectric power generation ended in 1973, and lakeside residents formed the 

Lake Delhi Association. The Lake Delhi Association 

purchased the dam to maintain the recreational opportunities of Lake Delhi.

Since 1973, the increased population around Lake 

Delhi, the increased recreational use, and possible 

contaminant inputs (point and nonpoint sources) are of 

concern to lake users. In particular, inputs of nutrients 

(nitrate, ammonia, and phosphorus), sediment, and 

bacteria can negatively affect water quality and recreational users of Lake Delhi. An assessment of the 

bathymetry (depth to lake bottom), sediment quality, 

and water quality of Lake Delhi are the main areas of 

concern that have been identified by the Lake Delhi 

Association board and lakeside residents. Documenting baseline concentrations of nutrients, sediment, and 

bacteria is a first step in understanding the effects of 

contaminants on Lake Delhi now and for monitoring 

changes in the future.

Several studies in eastern Iowa have identified 

nutrients as a major contaminant of concern in impairing water quality (Goolsby and Battaglin, 1993; Hallberg and others, 1996; Schnoebelen and others, 1999; 

Kalkhoff and others, 2000; Becher and others, 2001). 

In addition, the increased concentrations of nitrogen 

and phosphorus from Iowa streams are discharged to 

the Mississippi River and have been linked to the 

occurrence of hypoxia (low-oxygen zone) in the Gulf 

of Mexico (Turner and Rabalais, 1994; Goolsby and 

others, 1999). Even though these previous studies in 

eastern Iowa have not focused directly on Lake Delhi, 

results from these studies may be applicable to the 

lake. Nitrogen and phosphorus are compounds that can 

occur naturally in ambient stream and lake water but 

generally at low concentrations (less than 5 mg/L for 

nitrogen and less than 1 mg/L for phosphorus). High 

concentrations of nitrogen (5–25 mg/L) and phosphorus (greater than 1 mg/L) in streams and lakes can be 

the result of increased discharges from wastewater 

plants, leaking septic tanks, fertilizer runoff, livestock 

production, and soil erosion. Each of these potential 

sources is present in the Lake Delhi watershed or 

upstream from Lake Delhi. The city of Manchester 

(population 5,308; State Library of Iowa, 2000) wastewater plant is approximately 6 mi upstream from Lake 

Delhi, all lakeside residents use septic tanks, and there 

are numerous farms and livestock in the watershed. 

Riparian zones along the tributaries are often small 

(less than 200 ft wide) in the Lake Delhi watershed, 

and in many places agricultural land adjoins streams. 

High concentrations of nitrogen and phosphorus in 

streams and lakes can contribute to increased aquatic 

plant growth and eutrophication which degrade recreational use.

Lakeside residents typically identify sediment (or 

sediment deposition) as a constituent of most concern 

to recreational use. Sediment often is mentioned by 

residents because it is readily visible in the water column. The Iowa Department of Natural Resources lists 

sediment as the number one contaminant in rivers and 

lakes of Iowa (Iowa Department of Natural Resources, 

1994). Long-time lakeside residents report areas of the 

lake that are no longer navigable by boats because the 

water is too shallow. The Lake Delhi Association has 

discussed dredging and installation of sediment traps 

in the upstream part of the lake. Establishing baseline 

conditions of the bathymetry of Lake Delhi are important if future dredging does occur. If dredging does 

occur, the availability of historical baseline conditions 

would allow future bathymetric mapping to determine 

the amount of sediment deposition that has occurred 

by comparing new bathymetric maps to previous 

bathymetric maps. 
Introduction 3

Sediment quality is another area of concern before 

dredge work could begin. Trace metals, such as chromium and lead, often accumulate in lake-bottom sediments, and knowing the concentration of these metals 

in the lake-bottom sediments is important before 

dredging begins. Work on assisting farmers in implementing soil erosion control practices in the watershed 

has begun by the Lake Delhi Recreation Association, 

the Maquoketa River Water Quality Team, the Iowa 

Waste Reduction Center of the University of Northern 

Iowa, the Natural Resources Conservation Service 

(NRCS), and the Delaware County Soil and Water 

Conservation District (SWCD). 

Increasing bacteria levels are of concern to those 

using Lake Delhi. In recent years elevated “indicator 

bacteria” levels in several Iowa streams and lakes have 

resulted in the closing of some beaches (Iowa Department of Natural Resources, 2003). Because of the difficulties analyzing for and detecting many diseasecausing organisms, “indicator bacteria”—fecal 

coliform, total coliform, and E. coli bacteria—are used 

as the primary means of identifying fecal contamination. Pathogens causing many diseases live in the 

intestines of warmblooded animals and are passed 

along in feces. An increase in the concentrations of 

indicator bacteria above U.S. Environmental Protection Agency (USEPA) criteria in lake water may indicate the presence of pathogens. Water-borne pathogens 

can cause ear or skin infections and gastrointestinal illnesses. Data from water samples analyzed for indicator bacteria (total coliform and E. coli) are important 

information for residents that swim or water ski in 

Lake Delhi. 

To address the concerns of water managers and 

users of Lake Delhi, the U.S. Geological Survey 

(USGS), in cooperation with the Iowa Waste Reduction Center, University of Northern Iowa, and the Lake 

Delhi Association conducted a study of the bathymetry, sediment quality, and water quality of Lake Delhi 

from 2001 through 2002.

Purpose and Scope

The purpose of this report is to describe results of 

a study to map the depth of Lake Delhi and to assess 

sediment quality and selected water-quality constituents of Lake Delhi. Figure 1 shows the location of 

Lake Delhi and lake-bottom core and water-quality 

sampling sites. The sediment-quality information from 

the cores provide a better understanding of selected 

trace-metal constituents in the lake-bottom sediments, 

and the water-column samples provide information on 

nutrients and bacteria with selected information on 

major ions, trace elements, and pesticides. 

The bathymetric map can be used to identify possible dredging locations and to establish baseline lakebottom conditions both before and after dredging. 

Selected trace-element concentrations from lakebottom cores collected in September 2001 were analyzed to assess the quality of lake-bottom sediments. 

Water-quality samples were collected during June 

2001 through July 2002 from the Maquoketa River, 

Lake Delhi, and four small tributaries to assess concentrations of nutrients, bacteria, and suspended sediment in the water column. Water-quality samples were 

collected in June 2001 from the Maquoketa River and 

the downstream reach of Lake Delhi (site 080 near the 

dam) and analyzed for pesticides. Water-quality samples were collected in June and September 2001 from 

the Maquoketa River, lake, and tributary sites and analyzed for major ions and trace metals. 

A detailed examination of each of the sources of 

contaminants to Lake Delhi is beyond the scope of 

this report. The study results described in this report 

are not exhaustive but rather a first assessment of 

Lake Delhi.

Acknowledgments

The authors would like to thank the Iowa Waste 

Reduction Center, University of Northern Iowa, for 

assistance with project planning and coordination with 

lakeside residents, and facilitating access to the lake 

for water-quality sampling and mapping. In particular, 

Sue Behrns, Lake Delhi Association, helped with 

many activities. Mike Russell, a homeowner on the 

lake, volunteered to assist with the sediment coring. 

The USGS office in Lawrence, Kansas, provided the 

core boat and the assistance of Patrick Finnegan for 

the collection of the lake-bottom cores. Much appreciation goes to USGS Iowa employees—Jim Cerveny, 

Doug Goodrich, Mike Linhart, Jon Nania, and Nick 

VanderZwan—for their dedicated data-collection 

efforts throughout the study.

Special recognition and appreciation goes to Gray 

Krizanich with the USGS National Mapping Discipline (NMD) in Rolla, Missouri, who processed much 

of the collected data for the bathymetric map. In addition, Dan Christiansen with the USGS in Iowa assisted 

with finalizing the maps before publication.
4 Bathymetric Mapping, Sediment Quality, and Water Quality of Lake Delhi, Iowa, 2001–02

20

Dam

221th St. 

240th St. 

Jefferson Rd.

255th St.

267th St.

240th St.

210th Ave. 

220th Ave. 

220th Ave. 

230th St. 

210th Ave. 

197th Ave. 

190th Ave. 

180th Ave. 

245th St. 

250th St.

230th Ave. 

230th Ave. 

Sand

Lake

Delhi

Spring Branch

Creek

Sand

Turtle

Creek

Maquoketa River

Manchester

Delaware

Delhi

EXPLANATION

0 0.5 1.0 KILOMETERS

0 0.5 1.0 MILES

Index map

Study area

IOWA

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

Universal Transverse Mercater projection

Zone 15

020

024

015

010

015

Greenslades

The

Cedars

The Cedars

Maples

Maples

Clear

View

Acres

016

020

024

030

040

062

065

068

080

070

050

Water-quality sampling site and local site number

Lake-bottom core sampling site, local site number, 

 and local name

Lake-bottom core and water-quality sampling site, 

 local site number, and local name

Wellman's

Camp

Linden

Acres

Hartwick

Dredge

Deer Run

Hickory

Hollow

42°24'

42°28'

91°26' 91 24" °22'

26'

Figure 1. Location of Lake Delhi study area and sampling sites in eastern Iowa.
Methods of Study 5

METHODS OF STUDY

The bathymetric mapping incorporated a combination of global positioning system (GPS) technology 

and echo sounding to determine the lake-bottom surface. Seven lake bottom cores were collected at seven 

sites (016, 020, 024, 050, 062, 065, and 068) for trace 

element analysis (fig. 1). Water-quality samples were 

collected five times at eight sites from June 2001 

through July 2002 (fig.1)—one site on the Maquoketa 

River (site 010, upstream from Lake Delhi), three sites 

in Lake Delhi (sites 020, 050, and 080), and four tributary sites (sites 015, 030, 040, and 070). All sites in the 

report are identified by a local (three digit) site number 

(figs. 1–5) that corresponds to a standard (eight digit) 

USGS surface-water station number (tables 5–13).

Bathymetric Mapping

Bathymetric mapping was accomplished by use of 

GPS equipment, echo depth-sounding equipment, and 

HypackMax computer software. The HypackMax software is used to interpret and combine the depthsounding data with the GPS data. Initial measurements 

determined the elevation of the surface of the lake referenced to National Geodetic Vertical Datum (NGVD) 

of 1929 using a triangulation process by establishing 

reference points using GPS and rover-receiving 

(mobile) units. Lake-surface elevations were collected 

each day compared to known reference points—a 

downstream location at the dam and an upstream location at the northwest corner of the lake. The downstream lake reference point is located on a steel piece 

of angle iron on the right bank upstream side of the 

dam. The upstream lake reference point (at the northwest corner of the lake) is located on the top of a section of conduit at the end of the private boat ramp 

located just off 197th Avenue (near coring site 016). 

The reference points were established using the ASHTECH GPS system. These elevations were referenced 

to known benchmarks at two separate locations in Delaware County. The accuracy of these reference points 

is + 0.03 ft.

The bathymetry and elevation data were collected 

from July 17–20, 2001, and July 24–25, 2001. There 

was a slight elevation drop between the upstream and 

downstream end of the lake-surface elevation, which 

was approximately 0.50 ft. The HypackMax software 

compensated for this slope difference in all 

calculations. The lake-surface elevation accuracy was 

+ 0.20 ft. The lake-surface elevation during data collection varied from 896.52 to 895.93 ft at the downstream location (the dam) and from 895.31 to 896.06 ft 

at the upstream location (off 197th Avenue). These 

fluctuations in lake surface-elevation do not affect the 

accuracy of the bottom elevation due to the time tagging (from the elevation and time recorded at the reference points) that the HypackMax software calculates. 

This process subtracts the depth from assigned elevation from the time-tagged values. When the lakesurface elevation changes, so do the depths; however, 

the bottom elevation remains constant even though the 

surface elevation of the lake may change.

Equipment used in the data collection included a 

boat, an echo sounder, a GPS system, and a laptop 

computer. A 14-ft flat-bottom boat was used for most 

of the data collection, and a canoe was used in the 

shallower water where the 14-ft boat was unable to 

navigate. Depths were measured by a Bathy 500 MF

echo sounder (Ocean Data Equipment Corporation, 

Providence, Rhode Island). The echo sounder emitted 

pulses of sound that reflected off the lake bottom and 

were received by a transducer. Traveltimes were calculated taking into account the water temperature and 

speed of sound to determine the depth of water. The 

echo sounder transmitted at a frequency of 200 kilohertz. This is an ideal system for the Lake Delhi study 

due to the smooth and generally hard bottom of this 

lake. The only limitation was that this echo sounder 

would not measure depths less than 3.30 ft. When the 

depths were less than 3.30 ft, the depths were determined by hand using a USGS wading rod marked in 

0.10-ft increments. The accuracy of these measurements was 0.05 ft. Position was determined by marking GPS points as depth readings were collected. The 

manual determination of shallow depths was labor 

intensive, but resulted in detailed measurements in 

many areas the echo sounder was unable to measure. 

Quality-control checks were performed on the 

echo sounder each day to make sure it was 

calibrated correctly.

A bar check on the echo sounder was performed at 

the start of each day following established protocols 

(U.S. Army Corps of Engineers, 1994, chapter 9). The 

bar check involved lowering a 2-ft-diameter flat piece 

of 3/8-in. thick aluminum plate suspended directly 

below the echo sounder. The plate was lowered to the 

maximum survey depth, and the speed of sound was 

adjusted to match the true depth. The plate was 

lowered and raised until the full range of the survey 
6 Bathymetric Mapping, Sediment Quality, and Water Quality of Lake Delhi, Iowa, 2001–02

was correct. A check was performed on the offset 

value, which is related to the draft (depth at which the 

bottom of the echo sounder is below the lake surface). 

Each offset was stable and did not vary by more than 

0.30 ft.

The GPS system used on the boat was connected 

to the echo sounder through the laptop computer. The 

GPS system measured a time-tagged latitude and longitude location—that was differentially corrected to 

improve the accuracy—for data received from the 

echo sounder. The GPS allowed for accuracies of 

about 3.28 ft (approximately 1 m) in the horizontal 

direction.

The HypackMax software was used for survey 

planning, survey execution, data storage, and editing. 

The HypackMax software interpreted and coordinated 

all the GPS and depth data received from the GPS and 

echo sounder units. Every individual depth had a 

unique latitude and longitude associated with it that 

was recorded by the HypackMax software. The software also was used to generate a preliminary bathymetric map of the lake bottom. The field crews were 

able to view the depths collected in real time on the 

monitor of the laptop computer. Real-time data monitoring allowed evaluation of any abnormal data spikes 

or depths. Depths of the lake were measured along 

approximately 300 uniformly spaced cross sections 

over the entire 7.5-mi length of the lake. Depths were 

measured at more than 300,000 points.

Bathymetry data were obtained by subtracting the 

depths at each location from the reference surface elevation of the lake, and data were exported to a flat-file 

or ASCII (American Standard Code for Information 

Interchange) format. This file contained latitude, longitude, and depth to the lake bottom for the data 

points. The latitude and longitude locations had the 

following projection parameters: Universal Transverse 

Mercator, zone 15, datum WGS84. Using a geographic 

information system (GIS) software package, ArcInfo, 

a point coverage representing discrete point locations 

of bathymetry was created. This point coverage then 

was used to generate a three-dimensional surface representing depth to the lake bottom. This surface then 

was contoured. The contours were reviewed, and the 

surface was adjusted to correct for interpretive errors 

and the process repeated as needed.

Sediment Sampling and Analysis

Lake-bottom sediments were cored at seven sites 

on Lake Delhi (fig. 1). Informal, “local names” near 

the seven coring sites included Greenslades 

(station 05417175, site 016), The Cedars 

(station 05417200, site 020), Maples 

(station 05417230, site 024), Linden Acres 

(station 05417320, site 050), Hartwick Dredge 

(station 05417390, site 062), Deer Run 

(station 05417440, site 065), and Hickory Hollow 

(station 05417460, site 068). The seven sites were 

located in areas where previous work (Mohn Surveying, Lansing, Iowa, written commun., October 1, 

1999) and the Lake Delhi Association had indicated 

future dredging might be necessary. A latitude and 

longitude position was determined at each site using a 

handheld GPS receiver. Water depths were less than 

5 ft deep in the areas selected for coring. The liner 

used in the corer was cellulose acetate butylate transport tubing with an inside diameter of 2.62 in. 

Initially, a Benthos gravity corer mounted on a 

pontoon boat was used, but the shallow water did not 

allow the Benthos corer to gather enough momentum 

to fully penetrate the bottom sediment. Instead, all 

cores were collected by driving the core liner into the 

bottom sediment by hand. The core liner was driven 

until refusal or until pre-lake bottom material was 

encountered (bedrock or glacial till). 

Cores ranged from approximately 2 to 5 ft in 

length and were transported to the USGS sediment 

laboratory in Iowa City, Iowa. Cores were numbered in 

a downstream order and identified by an eight-digit 

USGS station number, local name, and local site number. For example, the upstream-most lake core was 

from station 05417175, Lake Delhi at Greenslades, 

local site 016. Core numbers and station numbers 

increased in downstream order. 

In the laboratory, each core liner was split lengthwise to expose the sediment for sampling and description. A total of 20 sediment samples from the seven 

cores were analyzed for selected trace-metal and phosphorus constituents. Each core was measured in tenths 

of feet from the bottom of the core (0.0 ft) to the top of 

the core (nearest the sediment/water interface). Two to 

four sediment samples were selected from each core 

starting at the base of the core (0.0 ft) and moving 

upwards. Sediment samples for analysis were typically 

collected every foot or where there was a change in the 

sediment type within the core. The presence of prelake bottom material was determined by a change in 
Methods of Study 7

particle-size composition of the sediment indicating 

the presence of glacial till. The till had a brown color 

and a compacted texture. 

Sediment samples (from the seven cores) selected 

for analysis were labeled (station number, date, time, 

and depth interval) and were shipped by overnight 

express on ice to the USGS National Water-Quality 

Laboratory in Denver, Colorado, for chemical analyses. Table 1 lists the sediment constituents analyzed, 

Chemical Abstract Registry (CAS) number, USGS 

National Water Information System (NWIS) database 

code, and minimum reporting level (MRL). The 

MRL is determined by the laboratory as the lowest 

concentration at which a constituent can be 

accurately be measured.

Water-Quality Sampling and Analysis

Water-quality samples were collected at eight sites 

(fig. 1)—one site on the Maquoketa River upstream 

from the lake (station 05416900, site 010), three sites 

on Lake Delhi (station 05417200, site 020; station 

05417320, site 050; and station 05417480, site 080), 

and four tributary sites (station 05417170, site 015; 

station 05417275, site 030; station 05417300, site 040; 

and station 05417470, site 070). Each of the eight sites 

were sampled five times—June 2001, September 

2001, March 2002, June 2002, and July 2002—and 

analyzed for physical properties, nutrients, bacteria, 

and suspended sediment. A few samples were collected to provide a limited assessment of major ions, 

trace metals, and pesticides in the water column. A 

one-time sampling for major ions and trace metals in 

the water column was done at all eight sites in September 2001. Two samples were collected for pesticides—one (June 2001) at the Maquoketa River site 

(station 05416900, site 010) and one at the upstream 

Lake Delhi site (station 05417480, site 080). All water 

samples were collected using USGS protocols (Shelton, 1994; U.S. Geological Survey, 1998). Water samples for analysis of nutrients, major ions, and trace 

metals were filtered onsite through a 0.45-μ capsule 

filter. Water samples for analysis of pesticides were filtered onsite through a 0.70-μ glass-fiber filter.

Physical properties (specific conductance, pH, 

temperature, turbidity, dissolved oxygen, and alkalinity) were recorded at each site. Samples for bacteria 

analysis (total coliform and E. coli) were collected by 

membrane filtration and incubation at the USGS laboratory Iowa City, Iowa, following standard methods 

(U.S. Geological Survey, 1998). All water samples 

(with the exception of samples for bacteria) were 

shipped overnight on ice to the USGS National WaterQuality Laboratory (NWQL) in Denver, Colorado, for 

analysis. Water samples were analyzed at the NWQL 

for dissolved nutrient species that included dissolved 

ammonia as nitrogen, dissolved ammonia plus organic 

nitrogen, dissolved nitrate plus nitrite nitrogen, dissolved nitrite nitrogen, dissolved phosphorus, and dissolved orthophosphorus. Dissolved orthophosphorus is 

the phosphorus species most available for aquatic 

plant growth and was analyzed in all samples. Total 

phosphorus is typically sorbed on sediment and was 

only analyzed in a few water samples. Nitrate as used 

in this report included the nitrite species as this form 

of the nitrogen species is typically a small concentration (less than 0.1 mg/L). Suspended-sediment concentrations were analyzed at the USGS sediment 

laboratory in Iowa City.

Table 2 lists the nutrient and bacteria constituents 

analyzed for in the water column, the Chemical 

Abstract Registry (CAS) number, USGS National 

Water Information System (NWIS) database code, and 

minimum reporting level (MRL). Tables 3 lists the 

major ions, trace elements, and pesticides analyzed for 

in the water column, the Chemical Abstract Registry 

(CAS) number, USGS National Water Information 

System (NWIS) database code, and the laboratory 

reporting level (LRL). The LRL is used instead of the 

Table 1. Sediment constituents, Chemical Abstract Registry (CAS) 

number, National Water Information System (NWIS) database code, 

minimum reporting level (MRL), and reporting units

[μg/g, micrograms per gram; mg/kg, milligrams per kilogram]

Sediment

constituent CAS number NWIS code MRL

Reporting 

units

Aluminum 7429–90–5 01108 2.8 μg/g

Cadmium 7440–66–6 01028 .1 μg/g

Chromium 7440–47–3 01029 .4 μg/g

Cobalt 7440–48–4 01038 .1 μg/g

Copper 7440–50–8 01043 2.0 μg/g

Iron 7439–89–6 01170 2.1 μg/g

Lead 7439–92–1 01052 .1 μg/g

Manganese 7439–96–5 01053 .3 μg/g

Mercury 7439–97–6 71921 .01 μg/g

Nickel 7440–02–0 01068 .1 μg/g

Phosphorus 7723–14–0 00668 40 mg/kg

Zinc 7440–66–6 01093 3.1 μg/g
8 Bathymetric Mapping, Sediment Quality, and Water Quality of Lake Delhi, Iowa, 2001–02

MRL for specifying quantifiable limits for the majority of constituents listed in table 3 (unless footnoted). 

The LRL is defined more rigorously by statistics than 

the MRL and is replacing the MRL at the USGS 

NWQL (Oblinger-Childress and others, 1999).

BATHYMETRY, SEDIMENT QUALITY, AND WATER 

QUALITY

Bathymetry

The results of the bathymetric mapping show a 

number of areas with shallow water (less than 4 ft 

deep). In general, Lake Delhi can be divided into four 

reaches that show increasingly deeper water in a 

downstream direction toward the dam area. Figures 2 

through 5 illustrate the bathymetry for the upstream 

(A), upstream-middle (B), middle (C), and downstream (D) lake reaches. The upstream reach through 

most of the upstream-middle reach of Lake Delhi 

(approximately 3 mi) from about 0.25 mi upstream 

from the Greenslades coring site through Clair View 

Acres includes the shallowest areas of the lake, with 

water depths ranging from less than 1 ft to a few areas 

as much as 10 ft deep (figs. 2 and 3). In particular, the 

upstream-most 1 mi of Lake Delhi (from about 

0.25 mi upstream from the Greenslades coring site to 

0.25 mi downstream from The Cedars coring site is 

particularly shallow (on average 1 to 2 ft) with some 

areas only accessible by canoe (fig. 2). The middle 

reach of Lake Delhi (approximately 2.5 mi, fig. 4) is 

less affected by sediment accumulation, with water 

depths from less than 1 to 16 ft, but near the Linden 

Acres coring site and Wellman’s Camp there are shallow areas that average 2 to 8 ft. The downstream reach 

of Lake Delhi (approximately 1.75 mi, fig. 5) has 

depths from less than 1 to 26 ft deep. The deepest 

section measured on the lake was 26 ft just upstream 

from the dam.

Figures 2 through 5 show indications of the original Maquoketa River channel in Lake Delhi. The deepest part of the lake seems to follow the original river 

channel. Typically, the shallow parts of the lake were 

along the inside bank curves of the lake (inner area of 

the bank curve when looking in a downstream direction). Perhaps the flow through the lake could be following the old river channel where water velocities 

would be slower on the inner bank side of a curve. The 

slower velocities allow sediment to “drop out” of suspension and accumulate near the inner bank side. The 

bathymetric maps also show the possible sediment 

accumulation near the mouths of three tributaries that 

discharge into Lake Delhi. The mouths of the three 

tributaries—an unnamed tributary (fig. 3), Turtle 

Creek (fig. 4), and an unnamed tributary northwest of 

Turtle Creek (fig. 4)—all have shallow (less than 1 to 

4 ft) water where the tributaries merge with Lake 

Delhi. The sediment from Turtle Creek appears to be 

accumulating just downstream from a small island 

near site 050 (fig. 4). Possibly, the island acts as an 

obstacle further slowing water velocities and allowing 

sediment to accumulate. The water level between the 

island and the west bank is currently too shallow to 

boat through; however, long-time lakeside residents 

have reported that 20 years ago a boat could pass 

through on the west side of the island.

Table 2. Nutrient and bacteria constituents analyzed in water samples, Chemical Abstract Registry (CAS) number, National Water Information System 

(NWIS) database code, minimum reporting level (MRL), and reporting units

[mg/L, milligrams per liter; colonies/100 mL, colonies per 100 milliliters of sample; --, no data]

Water-quality constituent CAS number NWIS code MRL Reporting units

Nutrients

Nitrogen, ammonia, dissolved as N 7664–41–7 00608 0.041 mg/L

Nitrogen, ammonia + organic, dissolved as N 17778–88–0 00623 .10 mg/L

Nitrogen, nitrate + nitrite, dissolved as N -- 00631 .047 mg/L

Nitrogen, nitrite, dissolved as N 14797–65–0 00613 .008 mg/L

Phosphorus, dissolved as P 7723–14–0 00666 .0044 mg/L

Phosphorus, ortho, dissolved as P 14265–44–2 00671 .018 mg/L

Bacteria

Total coliform -- 31501 -- colonies/100 mL

E. coli -- 31633 -- colonies/100 mL
Bathymetry, Sediment Quality, and Water Quality 9

Table 3. Major ions, trace elements, and pesticides analyzed in water samples, Chemical Abstract Registry (CAS) number, National Water Information 

System (NWIS) database code, laboratory reporting level (LRL), and reporting units—Continued

Water-quality constituent CAS number NWIS code LRL Reporting units

Major ions

Calcium 7440–70–2 00915 0.012 mg/L

Chloride 16887–00–6 00940 .20 mg/L

Fluoride 16984–48–8 00950 1.17 mg/L

Magnesium 7439–95–4 00925 .008 mg/L

Potassium 7440–09–7 00935 .11 mg/L

Silica 7631–86–9 00955 .13 mg/L

Sodium 7440–23–5 00930 .09 mg/L

Sulfate 14808–79–8 00945 .18 mg/L

Trace elements

Barium 7440–39–3 01005 .9 μg/L

Beryllium 7440–41–7 01010 .5 μg/L

Cadmium 7440–43–9 01025 8 μg/L

Chromium 7440–47–3 01030 10 μg/L

Cobalt 7440–48–4 01035 8 μg/L

Copper 7440–50–8 01040 5.8 μg/L

Iron 7439–89–6 01046 10 μg/L

Lead 7439–92–1 01049 .08 μg/L

Lithium 7439–93–2 01130 3.9 μg/L

Manganese 7439–96–5 01056 1.6 μg/L

Molybdenum 7439–98–7 01060 30 μg/L

Nickel 7440–02–0 01065 29 μg/L

Silver 7440–22-4 01075 9 μg/L

Strontium 7440–24–6 01080 .6 μg/L

Vanadium 7440–62–2 01085 8 μg/L

Zinc 7440–66–6 01090 24 μg/L

Pesticides

2,6-Diethylaniline 579–66–8 82660 .006 μg/L

Acetochlor 34256–82–1 49260 .006 μg/L

Alachlor 15972–60–8 46342 .0045 μg/L

Atrazine 1912–24–9 39632 .007 μg/L

Azinphos-methyl 86–50–0 82686 .05 μg/L

Benfluralin 1861–40–1 82673 .010 μg/L

Butylate 2008–41–5 04028 .002 μg/L

Carbaryl 63–25–2 82680 .041 μg/L

Carbofuran 1563–66–2 82674 .020 μg/L

Chlorpyrifos 2921–88–2 38933 .005 μg/L

cis-Permethrin 54774–45–7 82687 .006 μg/L

Cyanazine 21725–46–2 04041 .018 μg/L

Dacthal 1861–32–1 82682 .0030 μg/L

Table 3. Major ions, trace elements, and pesticides analyzed in water samples, Chemical Abstract Registry (CAS) number, National Water Information 

System (NWIS) database code, laboratory reporting level (LRL), and reporting units

[μg/L, micrograms per liter; mg/L milligrams per liter; --, no data]
10 Bathymetric Mapping, Sediment Quality, and Water Quality of Lake Delhi, Iowa, 2001–02

Pesticides—Continued

Deethylatrazine 6190–65–4 04040 0.006 μg/L

Diazinon 333–41–5 39572 .005 μg/L

Dieldrin 60–57–1 39381 .0048 μg/L

Disulfoton 298–04–4 82677 .021 μg/L

EPTC 759–94–4 82668 .0020 μg/L

Ethalfluralin 55283–68–6 82663 .009 μg/L

Ethoprophos 13194–48–4 82672 .005 μg/L

Fonofos 944–22–9 04095 .0027 μg/L

Lindane 58–89–9 39341 .0040 μg/L

Linuron 330–55–2 82666 .035 μg/L

Malathion 121–75–5 39532 .027 μg/L

Metolachlor 51218–45–2 39415 .013 μg/L

Metribuzin 21087–64–9 82630 .006 μg/L

Molinate 2212–67–1 82671 .0016 μg/L

Napropamide 15299–99–7 82684 .007 μg/L

p,p'-DDE 72–55–9 34653 .0025 μg/L

Parathion 56–38–2 39542 .010 μg/L

Parathion-methyl 298–00–0 82667 .006 μg/L

Pebulate 1114–71–2 82669 .0041 μg/L

Pendimethalin 40487–42–1 82683 .022 μg/L

Phorate 298–02–2 82664 .011 μg/L

Prometon 1610–18–0 04037 .015 μg/L

Propachlor 1918–16–7 04024 .010 μg/L

Propanil 709–98–8 82679 .011 μg/L

Propargite 2312–35–8 82685 .023 μg/L

Simazine 122–34–9 04035 .005 μg/L

Tebuthiuron 34014–18–1 82670 .016 μg/L

Terbacil 5902–51–2 82665 .034 μg/L

Terbufos 13071–79–9 82675 .017 μg/L

Thiobencarb 28249–77–6 82681 .0048 μg/L

Triallate 2303–17–5 82678 .0023 μg/L

Trifluralin 1582–09–8 82661 .009 μg/L

1

Minimum reporting level (MRL).

Table 3. Major ions, trace elements, and pesticides analyzed in water samples, Chemical Abstract Registry (CAS) number, National Water Information 

System (NWIS) database code, laboratory reporting level (LRL), and reporting units—Continued

Water-quality constituent CAS number NWIS code LRL Reporting units
Bathymetry, Sediment Quality, and Water Quality 11

2

2

4

4

6

A.

B.

C. D.

020

020

016

016

015 015

015

2

950

Greenslades

The CedarsThe Cedars

42°25'35"

42°26'23"

91°24'30" 24' 91°23'30"

26'

Base from U.S. Geological Survey

Manchester 1:24,000, 1973

0 0.25 0.50 KILOMETER

0 0.25 0.50 MILE

A.

Index map

Depth, in feet below

water surface

0 – 2

2 – 4

4 – 6

6 – 8

8 – 10

10 – 12

12 – 14

14 – 16

16 – 18

18 – 20

20 – 22

22 – 24

24 – 26

Line of equal depth to lake-bottom sediment—Interval is 2 feet. 

 Datum is lake surface (896.0 feet above NGVD of 29)

Topographic contour—Shows elevation of land surface.

 Contour interval 10 feet. Datum is NGVD of 29

Water-quality sampling site and local site number

Lake-bottom core sampling site and local site number

Lake-bottom core and water-quality sampling site and 

 local site number

Lake boundary

Water body

Island

EXPLANATION

Figure 2. Bathymetry for upstream reach of Lake Delhi.
12 Bathymetric Mapping, Sediment Quality, and Water Quality of Lake Delhi, Iowa, 2001–02

Figure 3. Bathymetry for upstream-middle reach of Lake Delhi.
Bathymetry, Sediment Quality, and Water Quality 13

Figure 4. Bathymetry for middle reach of Lake Delhi.
14 Bathymetric Mapping, Sediment Quality, and Water Quality of Lake Delhi, Iowa, 2001–02

Figure 5. Bathymetry for downstream reach of Lake Delhi.
Bathymetry, Sediment Quality, and Water Quality 15

The tributary streams typically have small streamflows (less than 1.0 ft3

/s); however; the tributary 

streams can carry large volumes of sediment during 

storm runoff. For example, during storm runoff (September 2001) Turtle Creek transported more than four 

times the sediment load compared to nonrunoff (July 

2002) conditions. Sediment loads and yields for the 

Maquoketa River and tributary streams are discussed 

in more detail in the “Water Quality” section of 

this report, and results are tabulated in table 8 of 

that section.

Sediment Quality

The USEPA has established sediment-quality 

guidelines in the form of “level-of-concern concentrations” for several trace metals (U.S. Environmental 

Protection Agency, 1997). These level-of-concern concentrations were derived from biological effects correlations made on the basis of paired onsite and 

laboratory data to relate incidence of adverse biological effects to dry-weight sediment concentrations. Two 

such level-of-concern concentrations defined by the 

USEPA are the threshold effects level (TEL) and the 

probable effects level (PEL). The TEL is the smaller of 

the two levels of concern and is defined as the concentration below which toxic biological effects rarely 

occur. At concentrations above the PEL, toxic effects 

typically occur. In the range of concentrations between 

the TEL and PEL, adverse effects occasionally occur. 

Both the TEL and PEL are guidelines to be used as 

screening tools for possible contaminant effects and 

are not regulatory criteria. The USEPA (1997) has 

made this statement because, although biological 

effects correlation identifies level-of-concern concentrations associated with adverse organism response, 

the procedure does not demonstrate that a particular 

contaminant is solely responsible. In particular, chromium concentrations were of interest at Lake Delhi 

because lakeside residents had mentioned that a tanning factory once operated upstream of Lake Delhi in 

Manchester, Iowa. Chromium and its salts are typically used in the tanning industry. Chromium in large 

quantities can cause health problems in humans 

(Agency for Toxic Substances and Disease Registry, 

2002). It is unknown if the tanning factory ever used or 

discharged chromium to the Maquoketa River.

The median and average trace-element concentrations in the lake-bottom sediment samples did not 

exceed the TEL or PEL guidelines as set by the 

USEPA (table 4). Only one sample from site 016 

(Greenslades) contained concentrations that slightly 

exceeded the TEL guidelines for copper and nickel 

(table 4). The potential source of the nickel and copper 

concentrations is unknown. However, nickel and copper are two common metals that naturally occur in 

soils and commonly are used in the production of 

metal alloys. Nickel often is used in stainless-steel 

production, and copper is often used in bronze or brass 

Table 4. Statistical summary of selected trace metal and phosphorus concentrations in bottom-sediment samples from Lake Delhi, eastern Iowa, 

September 2001, and comparison to sediment-quality guidelines

[μg/g, micrograms per gram; mg/kg, milligrams per kilogram; TEL, threshold effects level; PEL, probable effects level]

Constituent

Concentrations in bottom-sediment samples 

(μg/g, except for phosphorus which is mg/kg) 1

Sediment guidelines (μg/g)

1

Sediment-quality guidelines from U.S. Environmental Protection Agency (1997).

Minimum Maximum Median Average TEL PEL

Aluminum 1,500 19,000 4,900 6,950 -- --

Cadmium <.03 .4 .20 .18 0.68 4.21

Chromium 2.6 22 6.50 9.30 52.3 160

Cobalt .9 9.2 4.40 4.28 -- --

Copper <2 20 7.0 7.1 18.7 108

Iron 2,200 25,000 8,900 10,440 -- --

Lead 1 20 6.85 8.16 30.2 112

Manganese 22 510 255 240 -- --

Mercury <.01 .11 .02 .29 .13 .696

Nickel 1.9 23 10.4 9.7 15.9 42.8

Phosphorus 1,300 190 495 540 -- --

Zinc 5 80 30 32.4 124 271
16 Bathymetric Mapping, Sediment Quality, and Water Quality of Lake Delhi, Iowa, 2001–02

production. Chromium, a constituent of some concern 

because of the former tanning factory, did not have 

concentrations above the TEL or PEL (table 4).

Water Quality

Nutrients, bacteria, and suspended sediment were 

the main constituents of concern in Lake Delhi. Nutrients in the tributary streams and Lake Delhi include 

several species of nitrogen (ammonia, ammonia plus 

organic, nitrite plus nitrate, and nitrite) and phosphorus (orthophosphate and total phosphorus) that are dissolved in the water or attached to suspended sediment. 

Nutrients concentrations at specific sites are affected 

by numerous environmental and human factors such as 

climate, instream processing (algal growth, biotic 

uptake, and denitrification in bed material), soil transport, proximity to sources, land use, and magnitude of 

rainfall and storm runoff. Concentrations of total 

coliform and E. coli bacteria in the water column may 

originate from municipal sewage, agricultural wastes, 

and septic tanks. Bacteria concentrations can vary substantially in type and number depending on proximity 

to source, concentration of source material, soil type, 

rainfall, and runoff. Suspended sediment in the lake 

and the tributaries originates from upland erosion and 

erosion within the tributaries and lake. Storms can 

transport large loads of suspended sediment.

Results from the water-quality sampling in the 

lake and the tributaries show areas that are affected by 

nutrients, bacteria, and sediment. Table 5 summarizes 

the water-quality results for nutrients and bacteria collected from the Marquoketa River sampling site 

upstream from Lake Delhi (site 010), the lake sites 

(upstream lake site 020, middle lake site 050, and 

downstream lake site 080), and the tributary sites (030, 

040, 060, 070). Sixty-eight percent of the samples collected (17 of 25 samples, table 10 in the “Supplemental Data” section at the end of this report) had nitrate 

concentrations (nitrite plus nitrate as nitrogen) greater 

than the 10-mg/L MCL (Maximum Contaminant 

Level) established by the USEPA (1986) for drinking 

water. The maximum nitrate concentration recorded 

was 18.6 mg/L (site 015, unnamed tributary) during 

the June 2002 sampling (table 10). The E. coli concentrations (that indicate the presence of feces from 

warmblooded animals) were particularly high (greater 

than 1,000 colonies per 100 mL) after storm runoff 

(September 2001) in the watershed (table 10). 

Supplemental data tables 9–13 at the end of this report 

list all the sediment-quality and water-quality data collected for the report.

The median nutrient concentrations were typically 

higher in the tributary samples than in the river and 

lake samples (table 5). Median concentrations of 

nitrate in samples from the river and tributary sites 

ranged from 10.5 to 12.1 mg/L, respectively, as compared to a median nitrate concentration of 8.7 mg/L in 

samples from the Lake Delhi sites. Other studies in 

eastern Iowa have shown that runoff from livestock 

waste and fertilizers may rapidly enter tributary 

streams during storms and increase nutrient and bacteria concentrations in the stream (Schnoebelen and others, 1999; Kalhoff and others, 2000; Becher and 

others, 2001). Livestock (in or near the tributary 

streams) and fertilizer runoff may be contributing to 

increased inputs of nutrients and bacteria in the tributary streams compared to those in the lake. Typically, a 

decrease in nitrate concentrations in Lake Delhi was 

observed in samples from the upstream lake site (010) 

to the downstream lake site (080) during each of the 

sample periods (reading across the columns of 

table 6). This decrease in nitrate concentrations from 

upstream to downstream in the lake was most likely 

the result of uptake of nitrate by algae and aquatic 

biota in the lake. The one exception to this pattern 

were the samples collected from Lake Delhi during 

March 2002 when all sites had similar nitrate concentrations (table 6). In this case, the March sample collection occurred just after “ice-out” of the lake, and 

most likely there was little (if any) processing of 

nitrate by algae. The lack of uptake by algae or other 

aquatic biota probably resulted in similar nitrate concentrations throughout the lake at this time. 

Seasonal variations of nitrate concentrations in 

Lake Delhi also were found (reading down the columns of table 6), with large nitrate concentration 

occurring in the samples collected during spring and 

late spring (May/June) and with small concentrations 

in samples collected during the summer and late summer (July and September). In eastern Iowa, large 

nitrate concentrations typically occur in the spring 

owing to applications of fertilizers followed by spring 

rain that transports nitrate to streams and lakes 

(Schnoebelen and others, 1999; Kalkhoff and others; 

2000; Becher and others, 2001). However, as the 

growing season continues, nitrate concentrations 

decrease as runoff becomes smaller (less rain) and the 

agricultural crops use the fertilizer. In addition, aquatic 
Bathymetry, Sediment Quality, and Water Quality 17

Table 5. Statistical summary of nutrient and bacteria concentrations in water samples from Maquoketa River, Lake Delhi, and tributary sites, eastern Iowa, 

June 2001 through June 2002, and comparison to water-quality guidelines 

[Constituent concentrations in milligrams per liter unless otherwise noted. USEPA, U.S. Environmental Protection Agency; MCL, Maximum Contaminant 

Level; E, estimated value; mg/L, milligrams per liter; colonies/100 mL, colonies per 100 milliliters of sample; --, no data; <, less than]

Constituent

Concentration

Minimum Maximum Median Average EPA MCL or guideline

Maquoketa River [station 05416900 (site 010) upstream of Lake Delhi]

Nitrogen, ammonia, dissolved as nitrogen E0.032 0.065 0.050 0.049 1Temperture and pH dependent

1U.S. Environmental Protection Agency (1999).

Nitrogen, ammonia + organic, dissolved as nitrogen .22 .49 .39 .37 --

Nitrogen, nitrite + nitrate, dissolved as nitrogen 8.28 13.5 10.5 10.7 210 mg/L

2

U.S. Environmental Protection Agency (1996).

Nitrogen, nitrite, dissolved as nitrogen .027 .065 .049 .049 2

1 mg/L

Phosphorus, dissolved as phosphorus .050 .158 .071 .088 3

0.1 mg/L

3

U.S. Environmental Protection Agency (1986).

Phosphorus, ortho, dissolved as phosphorus .500 .146 .460 .660 --

Total coliform (colonies/100 mL) 1,300 21,000 1,600 5,750 4200 colonies/100 mL (fecal)

4Iowa Department of Natural Resources (2003), bacteria standards are for body contact. Also, U.S. Environmental Protection Agency (1998).

E. coli (colonies/100 mL) 100 3,100 310 452 4126 colonies/100 mL

Lake sites [stations 05417200 (site 020), 05417320 (site 050), and 05417480 (site 080)]

Nitrogen, ammonia, dissolved as nitrogen <.040 .198 .040 .065 1Temperture and pH dependent

Nitrogen, ammonia + organic, dissolved as nitrogen .21 .71 .46 .45 --

Nitrogen, nitrite + nitrate, dissolved as nitrogen .500 13.5 8.7 9.66 210 mg/L

Nitrogen, nitrite, dissolved as nitrogen .031 .110 .061 .062 21 mg/L

Phosphorus, dissolved as phosphorus .033 .213 .072 .079 30.1 mg/L

Phosphorus, ortho, dissolved as phosphorus .010 .199 .047 .058 --

Total coliform (colonies/100 mL) 17 25,000 450 3,510 4200 colonies/100 mL (fecal)

E. coli (colonies/100 mL) 0 1,900 17 350 4126 colonies/100 mL

Tributary sites [stations 05417170 (site 015), 05417275 (site 030), 05417300 (site 040), and 05417470 (site 070)]

Nitrogen, ammonia, dissolved as nitrogen .029 .751 .046 .122 1Temperture and pH dependent

Nitrogen, ammonia + organic, dissolved as nitrogen .23 2.1 .58 .79 --

Nitrogen, nitrite + nitrate, dissolved as nitrogen 1.30 18.6 12.1 10.7 210 mg/L

Nitrogen, nitrite, dissolved as nitrogen .020 .158 .041 .074 21 mg/L

Phosphorus, dissolved as phosphorus .032 .658 .098 .203 3.1 mg/L

Phosphorus, ortho, dissolved as phosphorus <.020 .396 .065 .168 --

Total coliform (colonies/100 mL) 1 140,000 8,200 26,100 4200 colonies/100 mL (fecal)

E. coli (colonies/100 mL) 1 29,000 1,600 6,560 4

126 colonies/100 mL
18 Bathymetric Mapping, Sediment Quality, and Water Quality of Lake Delhi, Iowa, 2001–02

plants process much of the nitrate that moves to 

streams and lakes in Iowa during the summer and early 

fall (Becher and others, 2001). Algae blooms in Iowa 

during the late summer (September) confirm the large 

amount of aquatic plant growth and instream processing of nitrate during this time.

Total coliform bacteria concentrations were more 

variable in samples from the lake (table 7) when compared to nitrate concentrations (table 6). In general, 

bacteria concentrations decreased in samples from the 

upstream to downstream lake sites (reading across the 

columns, table 7). This decrease most likely was 

related to the decrease in sediment particles settling 

out because bacteria often are attached to sediment 

particles. However, exceptions to this occur during 

runoff. During the September 2001 sample collection, 

rainfall caused runoff at the downstream lake site, and 

the bacteria concentrations quickly increased at this 

site. Typically, large bacteria concentrations were 

related to runoff, and no seasonal patterns were noted. 

The one exception to this was the March 2002 sample 

collection that occurred during ice-out when the 

weather was still cold and no runoff was entering the 

lake. The combination of no runoff and colder temperatures resulted in the lowest bacteria concentrations 

measured for this report.

Sediment was a constituent of concern. Suspended-sediment concentrations and instantaneous 

loads and yields were calculated for the Maquoketa 

River and the four tributary water-quality sampling 

sites (table 8). An instantaneous load is the 

concentration of the suspended sediment multiplied by 

the streamflow (discharge) at the time of sediment collection. The load number helps identify how much 

sediment a stream is transporting. The sediment yield 

for a drainage area is the instantaneous load divided by 

the drainage area. The sediment yield for a drainage 

area is particularly important because the sediment 

yield allows a comparison that can identify the relative 

contribution of sediment by an area.

The results from the suspended-sediment analyses 

indicated large loads of sediment being transported to 

Lake Delhi from the Maquoketa River. Sediment loads 

calculated for the Maquoketa River (station 05416900, 

site 010) during the five sampling periods had loads 

that ranged from 12,600 to 98,000 lb/d (table 8). Loads 

for the tributary streams were smaller and ranged from 

0.1 to 5,300 lb/d (table 8). However, some of the tributary streams were shown to have high yields during 

rainfall and runoff. The unnamed tributary site 030 had 

the highest sediment yield (2,300 lb/mi2

) of any site 

during runoff in September 2001 (table 8). In general, 

Table 6. Nitrate concentrations in water samples from upstream, middle, 

and downstream portions of Lake Delhi, eastern Iowa sites, by season, 

June 2001 through July 2002

Season

(sampling date)

Nitrate concentrations, in milligrams per liter 

of nitrogen

Upstream 

(station 

05417200, 

site 020)

Middle 

(station 

05417320, 

site 050)

Downstream 

(station 

05417480, 

site 080)

Early spring 

(March 2002)

8.65 8.61 8.76

Spring

(May/June 2002)

13.5 13.1 8.49

Late spring

(June 2001)

12.7 12.2 12.0

Summer

(July 2002)

7.30 6.53 6.32

Late summer 

(September 2001)

7.80 5.11 5.00

Table 7. Total coliform and E. coli bacteria concentrations in water samples from upstream, middle, and downstream portions of Lake Delhi, eastern 

Iowa, by season, June 2001 through July 2002

[--, no data; E, estimated; M, material verified but not quantified]

Season

(sampling date)

Total coliform and E. coli concentrations, in colonies per 100 milliliters of sample

Upstream

(station 05417200, site 020)

Middle 

(station 05417320, site 050)

Downstream 

(station 05417480, site 080)

Early spring (March 2002) 420 (30) 20 (0) 17 (0)

Spring (May/June 2002) 5,300 (1,100) 1,000 (380) 450 (280)

Late spring (June 2001) 4,300 (--) 530 (E0) E40 (E2)

Summer (July 2002) 330 (170) 68 (4) 291 (0)

Late summer (September 2001) E 25,000 (M1) 1,900 (1,000) S13,000 (E1,900)
Bathymetry, Sediment Quality, and Water Quality 19

Table 8. Instantaneous discharge, suspended-sediment concentrations, loads, and yields by season for Maquoketa River and four 

tributary sites, eastern Iowa, June 2001 through July 2002 

[ft3/s, cubic feet per second; mg/L, milligrams per liter; lb/d, pounds per day; lb/mi2; pounds per square mile; mi2, square miles]

Season 

(sample date)

Instantaneous

discharge

(ft3

/s)

Suspended-sediment 

concentration

(mg/L)

Load

(lb/d)

Yield

(lb/mi2

)

Maquoketa River (station 05416900, site 010)—drainage area 275 mi2

Early spring (March 2002) 164 28 24,800 90

Spring (May/June 2002) 395 46 98,000 360

Late spring (June 2001) 240 41 53,100 190

Summer (July 2002) 1

122

1

Flow from stream gage.

19 12,600 46

Late summer (September 2001) 356 34 65,300 240

Average 255 34 50,800 180

Unnamed tributary (station 05417170, site 015)—drainage area 2.09 mi2

Early spring (March 2002) .64 1 3.5 1.7

Spring (May/June 2002) 2.3 6 74 35

Late spring (June 2001) .34 10 18 8.8

Summer (July 2002) .35 2.5 4.7 2.3

Late summer (September 2001) .41 13 29 14

Average .81 6.5 26 12

Unnamed tributary (station 05417275, site 030)—drainage area 2.29 mi2

Early spring (March 2002) .79 26 110 48

Spring (May/June 2002) 1.8 28 270 120

Late spring (June 2001) .70 10 38 17

Summer (July 2002) .49 15 40 18

Late summer (September 2001) 3.5 280 5,300 2,300

Average 1.46 72 1,200 500

Turtle Creek (station 05417300, site 040)—drainage area 2.10 mi2

Early spring (March 2002) .80 8 34 16

Spring (May/June 2002) 1.1 33 200 93

Late spring (June 2001) .87 120 550 260

Summer (July 2002) .88 26 120 58

Late summer (September 2001) 1.1 98 580 280

Average .95 57 300 140

Unnamed tributary (station 05417470, site 070)—drainage area 1.51 mi2

Early spring (March 2002) .16 17 15 9.7

Spring (May/June 2002) .07 23 8.7 5.8

Late spring (June 2001) .08 36 15 10

Summer (July 2002) 2.001

2

Flow observed but was too small to measure, estimated value.

21 .1 .1

Late summer (September 2001) .82 48 210 140

Average .23 29 50 33
20 Bathymetric Mapping, Sediment Quality, and Water Quality of Lake Delhi, Iowa, 2001–02

the watershed upstream from site 030 has little if any 

riparian zone near the stream. Typically, a larger riparian zone near a stream provides beneficial effects to 

water quality in the stream (Sorenson and others, 

1999). The loads from the tributary sites may be small 

when compared to the input from the Maquoketa 

River, but on a yield basis, the tributaries can contribute substantial amounts of sediment during runoff 

(table 8).

Additional Water-Quality Data

Additional water-quality data include the analytical results of two pesticide samples and a one-time 

sampling of major ions and trace metals that are listed 

in tables 9–13 in the “Supplemental Data” section at 

the back of this report. The pesticides detected were 

acetochlor (0.024 and 0.179 μg/L), alachlor 

(0.007 μg/L), atrazine (0.613 and 1.48 μg /L), and 

metolachlor (0.142 and 0.448 μg /L). Other pesticides 

were not detected (table 12). Acetochlor, atrazine, and 

metolachlor are the three most commonly used pesticides in eastern Iowa and are typically the most frequently detected (Akers and others, 2000; Kalkhoff 

and others, 2000). In general, the results of the majorion and trace-metal data also were typical of results 

collected from other streams in eastern Iowa for these 

constituents. Large concentrations of trace metals in 

the water column that might pose a human health concern were not detected. 

SUMMARY AND CONCLUSIONS

Lake Delhi (Federally recognized as Hartwick 

Lake) was formed in 1929 when the Interstate Power 

Company dammed the Maquoketa River to build a 

hydroelectrical generating plant. The local name 

“Lake Delhi” was adopted in recognition of the nearby 

town of Delhi, Iowa. The resulting 450-acre lake 

became a popular area in eastern Iowa for boating, 

swimming, and fishing. Hydroelectric power generation ended in 1973, and lakeside residents formed the 

Lake Delhi Association. The Lake Delhi Association 

purchased the dam to maintain the recreational opportunities of Lake Delhi.

Since 1973, the increased population around Lake 

Delhi, the increased recreational use, and possible 

contaminant inputs (point and nonpoint sources) are of 

concern to lake users. In particular, inputs of nutrients 

(nitrate, ammonia, and phosphorus), bacteria, and sediment can negatively affect water quality and recreational use of Lake Delhi. Increasing concerns of 

sediment deposition and water quality by lakeside residents led to the study described in this report that 

included a bathymetric survey and an assessment of 

sediment quality and water quality of Lake Delhi. The 

USGS conducted the study from June of 2001 through 

July 2002. 

A bathymetric map of Lake Delhi was constructed 

using over 300,000 data points from echo-sounding 

results and GIS software. Results of the bathymetric 

mapping showed that the upstream reach through most 

of the upstream-middle reach of Lake Delhi 

(approximately 3 mi) from about 0.25 mi upstream 

from the Greenslades coring site through Clair View 

Acres were the shallowest areas of the lake, with water 

depth ranging from less than 1 ft to a few areas that 

were as much as 10 ft deep. The upstream-most 1 mi 

of Lake Delhi (from about 0.25 mi upstream from the 

Greenslades coring site to 0.25 mi downstream from 

The Cedars coring site) was particularly shallow (on 

average 1 to 2 ft) with some areas only accessible by 

canoe. The middle reach of Lake Delhi (approximately 

2.5 mi) was less affected by sediment accumulation 

with water depths ranging from less than 1 to 16 ft, but 

near the Linden Acres coring site and Wellman’s 

Camp the lake had shallow areas that averaged 2 to 8 ft 

deep. The deepest section measured in the lake was 

26 ft just upstream from the dam. Tributary streams 

can contribute significant sediment loads during rainfall and runoff. Bathymetric mapping indicated that 

the deeper areas of the lake may follow the original 

Maquoketa River channel. 

Eleven trace metals and phosphorus were analyzed 

in 20 samples collected from seven bottom-sediment 

cores. The median and average concentrations from 

the lake bottom sediments did not exceed the threshold-effects-level or probable-effects-level guidelines 

for toxic biological effects established by USEPA. 

Chromium, a constituent of some concern (because of 

possible use in a former tanning factory in Manchester 

upstream from Lake Delhi) did not occur in concentrations that exceeded the threshold-effects-level or probable-effects-level guidelines.

Water-quality samples were collected at eight 

sites—one site on the Maquoketa River upstream from 

the lake, three sites on Lake Delhi, and four tributary 

sites. Each of the eight sites were sampled five times— 

June 2001, September 2001, March 2002, June 2002, 
References 21

and July 2002—and analyzed for physical properties 

(specific conductance, pH, temperature, dissolved 

oxygen, turbidity, and alkalinity), nutrients, bacteria 

(total coliform and E. coli), and suspended sediment. 

Two sites were sampled for pesticides in June 2001. A 

one-time sampling for major ions and trace metals in 

the water column was done at all eight sites in September 2001. Trace metals in the water column were not 

found in concentrations exceeding USEPA guidelines. 

Two samples were collected for pesticide analysis during the June 2001 sampling. The pesticides detected 

were acetochlor (0.024 and 0.179 μg/L), alachlor 

(0.007 μg/L), atrazine (0.613 and 1.48 μg/L), and 

metolachlor (0.142 and 0.448 μg/L).

Results from the water-quality sampling of the 

lake and tributaries showed areas that have been 

affected by nutrients and bacteria. The tributary 

streams had the highest median nitrate concentrations 

(12.1 mg/L) when compared to median nitrate concentrations in the lake (8.7 mg/L) or the Maquoketa River 

(10.5 mg/L). The maximum nitrate concentrations 

occurred during the spring, with 13.5 mg/L in a sample from the Maquoketa River, 13.5 mg/L in a sample 

from upstream lake site, and 18.6 mg/L in a sample 

from a tributary site. Median nitrate concentrations 

during the late summer decreased in samples from 

upstream (7.8 mg/L) to the downstream (5.0 mg/L) 

reaches of Lake Delhi, indicating possible 

instream processing of nitrate by algae and other 

aquatic organisms.

Median concentrations of total and E. coli bacteria 

in samples from the lake sites were 450 and 17 colonies per 100 mL, respectively. The highest bacteria 

concentrations observed in lake samples were 

25,000 total coliform per 100 mL (upstream lake site) 

and 1,900 E. coli per 100 mL (downstream lake site) 

after a rain and subsequent runoff (September 2001). 

Median total coliform and E. coli concentrations in 

samples from the tributary sites had the highest bacteria counts (of all sites) and were 8,200 and 1,600 colonies per 100 mL, respectively. In general, the tributary 

sites have small (less than 200 ft wide) riparian zones 

near the stream and agricultural land commonly 

adjoins the tributary streams. Runoff from livestock 

waste and fertilizers can enter tributary streams rapidly 

during storm runoff increasing nutrient and bacteria 

concentrations in the stream. Livestock in or near the 

tributary streams can contribute to increased inputs of 

nutrients and bacteria compared to those in the lake. 

Typically, a decrease in nitrate concentrations in Lake 

Delhi occurred in samples from the upstream lake 

site (010) to the downstream lake site (080) during 

each of the sample periods. The decrease in nitrate 

concentrations in samples from the upstream lake site 

to the downstream lake site was most likely the result 

of uptake of nitrate by algae and aquatic biota in the 

lake. 

Seasonal variations of nitrate concentrations in 

samples from Lake Delhi also were found, with larger 

nitrate concentrations (8.49–13.5 mg/L) occurring in 

the late spring (May/June) and smaller concentrations 

(5.0–7.8 mg/L) in the middle to late summer (July and 

September). In Iowa larger nitrate concentrations typically occur in the spring due to applications of fertilizers followed by spring rain that mobilize large 

concentrations of nitrate to streams and lakes. However, as the growing season continues nitrate concentrations decrease as runoff becomes smaller (less rain) 

and as agricultural plants grow and use more of the 

fertilizer. In addition, aquatic plants process much of 

the nitrate that moves to streams and lakes in Iowa during the summer and early fall.

In general, bacteria concentrations decreased from 

the upstream to downstream lake sites. This reduction 

was most likely related to the decrease in sediment 

particles settling out as bacteria often are attached to 

sediment particles. However, exceptions to this observation occurred during rainfall and runoff conditions. 

For example, during the September 2001 sample collection, rain caused runoff at the downstream lake site 

(site 080) that quickly increased the bacteria concentrations at this site to 13,000 total coliform colonies 

per 100 mL and 1,900 E. coli colonies per 100 mL. 

Typically, the larger bacteria concentrations recorded 

during the study were related to runoff, and no seasonal patterns were noted. 

REFERENCES

Agency for Toxic Substances and Disease Registry 

(ATSDR), 2002, Toxicological profile for chromium: 

Information available on the World Wide Web, 

accessed July 17, 2002, at URL 

http://www.atsdr.cdc.gov/toxprofiles/tp7.html

Akers, K.K.B., Montgomery, D.L., Christiansen, D.E., Savoca, M.E., Schnoebelen, D.J., Becher, K.D., and 

Sadorf, E.M., 2000, Water-quality assessment of the 

Eastern Iowa Basins—hydrologic and biologic data, 

October 1996 through September 1998: U.S. Geological Survey Open-File Report 00–67, 300 p.
22 Bathymetric Mapping, Sediment Quality, and Water Quality of Lake Delhi, Iowa, 2001–02

Becher, K.D., Kalkhoff, S.J., Schnoebelen, D.J., Barnes, 

K.K., and Miller, V.E., 2001, Water-quality assessment 

of the Eastern Iowa Basins—nitrogen, phosphorus, 

suspended sediment, and organic carbon in surface 

water, 1996–98: U.S. Geological Survey WaterResources Investigations Report 01–4175, 56 p.

Goolsby, D.A., and Battaglin, W.A., 1993, Occurrence, distribution, and transport of agricultural chemicals in 

surface water of the Midwestern United States, in 

Goolsby, D.A., Boyer, L.L., and Mallard, G.E., compilers, Selected papers on agricultural chemicals in water 

resources of the mid-continental United States: U.S. 

Geological Survey Open-File Report 93–418, p. 1–25.

Goolsby, D.A., Battaglin, W.A., Lawrence, G.B., Artz, R.S., 

Aulenbach, B.T., Hoper, R.P., Keeney, D.R., and Stensland, G.J., 1999, Flux and sources of nutrients in the 

Mississippi-Atchafalaya River Basin, Topic 3 Report 

of the integrated assessment on hypoxia in the Gulf of 

Mexico: Silver Spring, Maryland, National Oceanic 

and Atmospheric Administration Coastal Ocean 

Program, 130 p.

Hallberg, G.R., Riley, D.G., Kantamneni, J.R., Weyer, P.J., 

and Kelley, R.D., 1996, Assessment of Iowa safe 

drinking water act monitoring data, 1988–1995: Iowa 

City, University of Iowa Hygienic Laboratory Research 

Report 97–1, 132 p.

Iowa Department of Natural Resources, 1994, Water-quality 

in Iowa during 1992 and 1993: Iowa Environmental 

Protection Division, Water Resources section 305(b) 

Report, 226 p.

———2003, Water-quality testing at beaches in Iowa state 

parks and recreation areas: Information available on 

the World Wide Web, accessed January 30, 2003, at 

URL http://www.state.ia.us/government/dnr/

beach2000.htm

Kalkhoff, S.J., Barnes, K.K., Becher, K.D., Savoca, M.E., 

Schnoebelen, D.J., Sadorf, E.M., Porter, S.D., and Sullivan, D.J., 2000, Water quality in the Eastern Iowa 

Basins, Iowa and Minnesota, 1996–98: U.S. Geological Survey Circular 1210, 37 p.

Oblinger-Childress, C.J., Foreman, W.T., Connor, B.F., and 

Maloney, T.J., 1999, New reporting procedures based 

on long-term method detection levels and some considerations for interpretations of water-quality data provided by the U.S. Geological Survey National Water 

Quality Laboratory: U.S. Geological Survey OpenFile Report 99–193, 19 p.

Schnoebelen, D.J., Becher, K.D., Bobier, M.W., and Wilton, 

Tom, 1999, Selected nutrients and pesticides in 

streams of the Eastern Iowa Basins, 1970–95: U.S. 

Geological Survey Water-Resources Investigations 

Report 99–4028, 105 p.

Shelton, L.R., 1994, Field guide for collecting and processing stream-water samples for the National WaterQuality Assessment Program: U.S. Geological Survey 

Open-File Report 94–455, 42 p.

Sorenson, S.K., Porter, S.D., Akers, K.K., Harris, M.A., 

Kalkhoff, S.J., Lee, K.E., Roberts, L.R., and Terrio, 

P.J., 1999, Water quality and habitat conditions in 

upper Midwest streams relative to riparian vegetation 

and soil characteristics, August 1997—study design, 

methods, and data: U.S. Geological Survey Open-File 

Report 99–202, 53 p.

State Library of Iowa, 2000, 2000 census data for incorporated towns in Iowa and counties: Information available on the World Wide Web, accessed May 9, 2003, at 

URL http://www.silo.lib.ia.us/specialized-services/ 

datacenter/data-tables/scpopurbanruralsf32000.pdf

Turner, R.E., and Rabalais, N.N., 1994, Coastal eutrophication near the Mississippi River Delta: Nature, v. 364, 

p. 619–621.

U.S. Army Corps of Engineers, 1994, Engineering and 

design: Hydrographic survey EM 1110–2–1003, 

chap. 9–3, p. 9–4 to 9–9.

U.S. Environmental Protection Agency, 1986, Quality 

criteria for water 1986: Washington, D.C., 

Report 440/5–86–001, 453 p.

———1996, Drinking water regulations and health advisories: Washington, D.C., Report 822–R–96–001, 16 p.

———1997, The incidence and severity of sediment contamination in surface waters of the United States, 

volume 1—national sediment survey: Washington, 

D.C., Report 823–R–97–006, various pagination.

———1998, Bacteria water-quality standards for recreational waters (freshwater and marine), U.S. Environmental Protection Agency Office of Water 4305, Status 

Report—May 1998: EPA–823–R–98–003, various 

pagination.

———1999, Ammonia and aquatic life: U.S. Environmental Protection Agency Office of Water, Technical Fact 

Sheet, EPA-823–F–99–013, p. 2, information available 

on World Wide Web, accessed August 7, 2002, at URL 

http://www.epa.gov/ost/standards/ammonia/

technical.html

U.S. Geological Survey, 1998, National field manual for the 

collection of water-quality data: U.S. Geological Survey Techniques of Water-Resources Investigations, 

book 9, various pagination.
Supplemental Data 23

SUPPLEMENTAL DATA
24 Bathynetric mapping, Sediment Quality, and Water Quality of Lake Delhi, 2001–02 Table 9. Phosphorus and trace-element concentrations in samples from sediment cores, Lake Delhi, eastern Iowa, September 18, 2001

[mg/kg, milligrams per kilogram; μg/g, micrograms per gram; P, phosphorus; CD, cadmium; CO, cobalt; CU, copper; FE, iron; PB, lead; HG, mercury; NI, nicke

verified but not quantified]

Local site number

(fig. 1) Station number Station name

Time of sample 

collection

(24-hour)

Core sample interval 

(feet)

Moisture

content

dry weight

(percent of total)

Ph

tota

m

(mg

016 05417175 Lake Delhi at Greenslades 1000 0.2–0.5 42 

1005 1.0–1.3 42 1010 1.35–1.65 29 1015 2.0–2.3 17 

020 05417200 Upstream Lake Delhi near The Cedars 1100 0.2–0.5 39 

1105 1.0–1.3 29 1110 1.35–1.65 31 1115 1.8–2.1 39 

024 05417230 Lake Delhi at Maples 1200 0.2–0.5 17 

1205 1.3–1.6 29 1210 1.95–2.25 21 

050 05417320 Middle Lake Delhi near Linden Acres 1300 0.7–1.0 9 

1305 2.6–3.1 15 

062 05417390 Hartwick Dredge at Lake Delhi 1400 0.2–0.5 16 

1405 1.0–1.3 25 1410 1.7–2.0 24 1415 2.7–3.0 36 

065 05417440 Lake Delhi at Deer Run 1500 0.95–1.25 12 068 05417460 Lake Delhi at Hickory Hollow 1600 0.3–0.6 8 

1605 1.1–1.4 13 
Supplemental Data 25

Table 9. Phosphorus and trace-element concentrations in samples from sediment cores, Lake Delhi, eastern Iowa, September 18, 2001—Continued

Local

site number 

(fig. 1)

Station 

number

Cadmium,

recoverable 

from bottom 

material

(μg/g as Cd)

Chromium,

recoverable 

from bottom

material 

(μg/g as Cr)

Cobalt,

recoverable 

from

bottom

material

(μg/g as Co)

Copper,

recoverable 

from

bottom

material

(μg/g as Cu)

Iron,

sediment,

bed 

material

(μg/g as Fe)

Lead,

recoverable

from 

bottom 

material

(μg/g as Pb)

Manganese,

recoverable 

from

bottom 

material

(μg/g as Mn)

Mercury,

recoverable 

from bottom 

material

(μg/g as Hg)

016 05417175 0.40 22 9.2 20 25,000 20 500 0.04 

.40 22 8.4 17 25,000 19 510 .06 .20 12 5.2 10 14,000 12 290 .05 

<.03 3.5 1.4 <2.0 3,300 2.0 83 <.01 

020 05417200 .40 17 7.1 13 18,000 17 450 .11 

.20 17 4.9 9.0 13,000 10 270 .06 .30 13.6 5.7 10 15,000 16 280 .06 .20 12 4.5 8.0 12,000 9.9 270 .03 

024 05417230 M 4.3 1.6 <2.0 3,400 1.7 22 <.01 

.20 11 4.0 8.0 11,000 9.6 160 .03 .10 5.6 2.0 3.0 5,500 4.0 79 .01 

050 05417320 <.03 3.2 1.3 <2.0 2,800 1.3 33 <.01 

<.03 2.6 .9 <2.0 2,200 1.0 73 <.01 

062 05417390 .10 6.5 4.6 7.0 8,900 5.7 500 .02 

.20 6.3 5.2 7.0 8,200 7.8 320 .02 .20 7.9 5.5 9.0 8,900 7.6 270 .02 .10 6.2 4.3 5.0 7,100 6.1 200 .02 

065 05417440 .10 6.6 2.5 3.0 8,900 2.8 240 <.01 068 05417460 .10 5.9 3.5 3.0 9,900 4.0 140 .01 

.10 4.9 3.7 6.0 6,700 5.8 110 .01 
26 Bathynetric mapping, Sediment Quality, and Water Quality of Lake Delhi, 2001–02 Table 10. Nutrient and bacteria concentrations in water samples collected from Marquoketa River, tributary, and lake sites, Lake Delhi, eastern Iowa, June 2001 th

Local site number (fig. 1) Station number Station name Sampling date (month/day/year) Time of sample collection (24-hour) Nitrogen, ammonia, dissolved (mg/L as N

010 05416900 Maquoketa River at Manchester, Iowa 6/27/2001 1755 E0.039 

9/20/2001 0810 .061 3/19/2002 1545 E.032 6/01/2002 0830 .065 7/16/2002 1410 .045 

015 05417170 Unnamed tributary near Bailey Ford 6/27/2001 0955 E.038 

9/20/2001 1230 E.040 3/19/2002 1445 .084 6/01/2002 0945 E.027 7/17/2002 0810 .071 

020 05417200 Upstream Lake Delhi near The Cedars 6/27/2001 0835 E.039 

9/20/2001 0935 .109 3/19/2002 1245 E.023 5/31/2002 1550 .077 7/16/2002 1240 <.040 

030 05417275 Unnamed tributary at County Highway 267 and 205 Avenue 6/27/2001 1215 E.031 

9/19/2001 1050 .165 3/19/2002 1400 .174 5/31/2002 1740 E.029 7/17/2002 0905 <.040 

040 05417300 Turtle Creek at Turtle Creek recreation area 6/27/2001 1435 .072 

9/19/2001 1550 E.026 3/19/2002 1115 E.033 5/31/2002 1630 .047 7/16/2002 0925 <.040 

Table 10. Nutrient and bacteria concentrations in water samples collected from Marquoketa River, tributary, and lake sites, Lake Delhi, eastern Iowa, June 2001 th[mg/L, milligrams per liter; N, nitrogen; E, estimated value; <, less than; P, phosphorus; --, no data; colonies/100 mL, colonies per 100 milliliters of sample; S, most pr

quantified; N, presumptive evidence of presence; V, contamination; mL, milliliters]
Supplemental Data 27

050 05417320 Middle Lake Delhi near Linden Acres 6/26/2001 1520 E0.040 

9/19/2001 1655 <.040 3/19/2002 1155 <.040 5/31/2002 1510 .161 7/16/2002 1215 .140 

070 05417470 Unnamed Creek at cove near dam, site 070 6/26/2001 1150 .045 

9/19/2001 1430 .236 3/20/2002 1045 .751 5/31/2002 1335 .147 7/16/2002 1030 <.04 

080 05417480 Downstream Lake Delhi near dam 6/26/2001 1230 .046 

9/19/2001 1330 E.022 3/20/2002 0940 <.040 5/31/2002 1415 .198 

7/16/2002 1115 .123 

Table 10. Nutrient and bacteria concentrations in water samples collected from Marquoketa River, tributary, and lake sites, Lake Delhi, eastern Iowa, June 2001 th

Local site number 

(fig. 1) Station number Station name

Sampling date

(month/day/year)

Time of sample 

collection

(24-hour)

Nitrogen,

ammonia,

dissolved

(mg/L as N)
28 Bathynetric mapping, Sediment Quality, and Water Quality of Lake Delhi, 2001–02

Table 10. Nutrient and bacteria concentrations in water samples collected from Marquoketa River, tributary, and lake sites, Lake Delh

Iowa, June 2001 through July 2002—Continued

Local 

number

(fig. 1)

Station

number

Sampling

date

(month/day/year)

Phosphorus,

dissolved

(mg/L as P)

Phosphorus,

ortho,

dissolved

(mg/L as P)

Phosphorus,

total

(mg/L as P)

Total

coliform

(colonies/100 mL)

E

(colon

010 05416900 6/27/2001 0.081 0.029 0.111 1,300 

9/20/2001 .158 .146 -- S21,000 S33/19/2002 E.050 .040 -- 1,600 6/01/2002 .061 .051 .134 4,000 17/16/2002 .038 <.040 .100 830 

015 05417170 6/27/2001 .059 E.011 .071 E16,000 E9

9/20/2001 .297 .275 -- S120,000 223/19/2002 E.040 .034 -- 6,100 6/01/2002 .032 .027 .046 4,300 7/17/2002 .041 .026 .065 13,900 1

020 05417200 6/27/2001 .072 E.016 .107 4,300 

9/20/2001 .213 .199 -- E25,000 3/19/2002 E.033 .029 -- 420 5/31/2002 .072 .056 .164 5,300 17/16/2002 .042 .029 .106 330 

030 05417275 6/27/2001 .060 <.020 .066 5,300 

9/19/2001 .658 .62 -- V1 3/19/2002 E.054 .043 -- 4,600 5/31/2002 .052 .046 .105 8,600 7/17/2002 .072 .063 .096 11,800 1

040 05417300 6/27/2001 .104 <.020 .417 E64,000 E29

9/19/2001 .536 .51 -- S72,000 S183/19/2002 .060 .048 -- 1,800 5/31/2002 .092 .081 .159 6,900 47/16/2002 .102 .091 .158 7,800 7

050 05417320 6/26/2001 .071 E.011 .103 530 

9/19/2001 .064 .057 -- -- 3/19/2002 E.034 .025 -- 20 5/31/2002 .106 .086 .197 1,000 7/16/2002 .064 .044 .175 68 

070 05417470 6/26/2001 .268 .187 .399 E2,400 

9/19/2001 .434 .386 -- E140,000 3/20/2002 .237 .161 -- 13,000 45/31/2002 .267 .221 .375 19,000 127/16/2002 .256 .213 .328 3,700 20
Supplemental Data 29

080 05417480 6/26/2001 0.048 E0.010 0.071 E40 

9/19/2001 .079 .071 -- S13,000 E13/20/2002 E.043 .037 -- 17 5/31/2002 .114 .093 .209 450 7/16/2002 .054 .036 .090 291 

Table 10. Nutrient and bacteria concentrations in water samples collected from Marquoketa River, tributary, and lake sites, Lake Delh

Iowa, June 2001 through July 2002—Continued

Local 

number

(fig. 1)

Station

number

Sampling

date

(month/day/year)

Phosphorus,

dissolved

(mg/L as P)

Phosphorus,

ortho,

dissolved

(mg/L as P)

Phosphorus,

total

(mg/L as P)

Total

coliform

(colonies/100 mL)

E

(coloni
30 Bathynetric mapping, Sediment Quality, and Water Quality of Lake Delhi, 2001–02 Table 11. Instantaneous discharge, physical properties, and suspended-sediment concentrations in water samples collected from Marquoketa River, tributary, and la

2001 through July 2002—Continued Local site number (fig. 1) Station number Station name Sampling date (month/day/ year) Time of sample collection (24-hour) Discharge, instanta- neous (ft3/s) Specific conduc- tance (μS/cm) p

fi

d

010 05416900 Maquoketa River at Manchester, Iowa 6/27/2001 1755 240 532 

9/20/2001 0810 356 502 3/19/2002 1545 164 519 6/01/2002 0830 395 507 7/16/2002 1410 122 514 

015 05417170 Unnamed tributary near Bailey Ford 6/27/2001 0955 .34 485 

9/20/2001 1230 .407 653 3/19/2002 1445 .64 337 6/01/2002 0945 2.3 497 7/17/2002 0810 .35 550 

020 05417200 Upstream Lake Delhi near The Cedars 6/27/2001 0835 -- 530 

9/20/2001 0935 -- 497 3/19/2002 1245 -- 517 5/31/2002 1550 -- 490 7/16/2002 1240 -- 513 

030 05417275 Unnamed tributary at County Highway 267 and 205 Avenue 6/27/2001 1215 .70 512 

9/19/2001 1050 3.5 487 3/19/2002 1400 .79 402 5/31/2002 1740 1.8 455 7/17/2002 0905 .49 547 

040 05417300 Turtle Creek at Turtle Creek recreation area 6/27/2001 1435 .87 418 

9/19/2001 1550 1.10 536 3/19/2002 1115 .80 557 5/31/2002 1630 1.1 528 7/16/2002 0925 .88 585 

Table 11. Instantaneous discharge, physical properties, and suspended-sediment concentrations in water samples collected from Marquoketa River, tributary, June 2001 through July 2002[ft3/s, cubic feet per second; μS/cm, microsiemens per centimeter; oC, Celsius degrees; NTU, nephelometric turbidity units; mg/L, milligrams per liter; CaCO3, calciu

carbonate; --, no data; E, estimated]
Supplemental Data 31

050 05417320 Middle Lake Delhi near Linden Acres 6/26/2001 1520 -- 499 

9/19/2001 1655 -- 486 3/19/2002 1155 -- 494 5/31/2002 1510 -- 454 7/16/2002 1215 -- 497 

070 05417470 Unnamed tributary at cove near dam 6/26/2001 1150 0.08 286 

9/19/2001 1430 .82 390 3/20/2002 1045 .16 373 5/31/2002 1335 .07 486 7/16/2002 1030 E .001 462 

080 05417480 Downstream Lake Delhi near dam 6/26/2001 1230 -- 492 

9/19/2001 1330 -- 426 3/20/2002 0940 -- 495 5/31/2002 1415 -- 400 7/16/2002 1115 -- 473 

Table 11. Instantaneous discharge, physical properties, and suspended-sediment concentrations in water samples collected from Marquoketa River, tributary, and la

2001 through July 2002—Continued

Local site 

number

(fig. 1) Station number Station name

Sampling 

date

(month/day/

year)

Time of sample 

collection

(24-hour)

Discharge, 

instantaneous

(ft3/s)

Specific 

conductance 

(μS/cm)

p

fie

da
32 Bathynetric mapping, Sediment Quality, and Water Quality of Lake Delhi, 2001–02 Table 11. Instantaneous discharge, physical properties, and suspended-sediment concentrations in water samples collected from Marqu

tributary, and lake sites, Lake Delhi, eastern Iowa, June 2001 through July 2002—Continued Local site number (fig. 1) Station number Station name Turbidity, laboratory (NTU) Oxygen, dissolved (mg/L) Oxygen, dissolved (percent saturation) Alkalinity, water, dis- solved, total, field (mg/L as CaCO3) Bicarbon- ate, water, dissolved, field (mg/L as HCO3) Carbonate, water, dis- solved, field (mg/L as CaCO3) 

010 05416900 6/27/2001 13 8.2 101 -- -- -- 

9/20/2001 20 9.3 97 177 214 0 3/19/2002 3.9 12.5 100 178 215 0 6/01/2002 130 9.8 103 145 175 0 7/16/2002 8.8 9.2 110 203 244 2 

015 05417170 6/27/2001 4.4 8.8 102 -- -- -- 

9/20/2001 9.5 8.7 -- 200 241 1 3/19/2002 2.1 13.2 106 150 182 0 6/01/2002 3.3 10.1 111 125 151 0 7/17/2002 3.1 7.9 82 188 228 0 

020 05417200 6/27/2001 21 7.3 86 -- -- -- 

9/20/2001 14 8.2 86 180 217 1 3/19/2002 2.9 12.5 100 179 216 0 5/31/2002 30 8.8 98 144 174 0 7/16/2002 9.9 10.8 134 192 229 3 

030 05417275 6/27/2001 4.9 9.2 102 -- -- -- 

9/19/2001 48 1.7 18 149 182 0 3/19/2002 7.3 12.4 96 140 170 0 5/31/2002 18 10.3 102 120 145 0 7/17/2002 7.0 8.7 89 175 212 0 

040 05417300 6/27/2001 62 7.8 87 -- -- -- 

9/19/2001 22 -- -- 186 226 0 3/19/2002 5.0 12.5 98 184 223 0 5/31/2002 14 9.7 98 149 180 0 7/16/2002 14 9.0 89 208 252 0 

050 05417320 6/26/2001 18 10.4 128 -- -- -- 
Supplemental Data 33

050 05417320 9/19/2001 14 9.2 101 194 236 0 

3/19/2002 6.0 13.4 105 171 207 0 5/31/2002 34 8.1 92 136 164 0 7/16/2002 25 8.4 103 183 219 0 

070 05417470 6/26/2001 17 7.8 92 -- -- -- 

9/19/2001 34 7.9 87 152 185 0 3/20/2002 15 13.7 110 213 255 2 5/31/2002 18 9.7 108 202 242 0 7/16/2002 33 8.2 91 197 237 0 

080 05417480 6/26/2001 7.9 10.6 127 -- -- -- 

9/19/2001 13 7.2 79 178 216 0 3/20/2002 4.9 15.7 120 165 199 0 5/31/2002 33 8.3 96 130 157 0 7/16/2002 11 9.0 112 130 158 0 

Table 11. Instantaneous discharge, physical properties, and suspended-sediment concentrations in water samples collected from Marqu

tributary, and lake sites, Lake Delhi, eastern Iowa, June 2001 through July 2002—Continued

Local site 

number

(fig. 1) Station number Station name

Turbidity, 

laboratory 

(NTU)

Oxygen, 

dissolved 

(mg/L)

Oxygen, 

dissolved 

(percent 

saturation)

Alkalinity, 

water, dissolved, 

total, field 

(mg/L as 

CaCO3)

Bicarbonate, water, 

dissolved, 

field (mg/L 

as HCO3)

Carbonate, 

water, dissolved, field 

(mg/L as 

CaCO3)
34 Bathymetric Mapping, Sediment Quality, and Water Quality of Lake Delhi, Iowa, 2001–02

Table 12. Pesticide concentrations in water samples collected at selected sites near or at Lake Delhi, eastern Iowa, June 2001—Continued

Pesticide compound 

(unit of measurement)

Maquoketa River at Manchester, Iowa

(site 010, station 05416900, sampled 

June 27, 2001; fig. 1)

Lake Delhi near dam 

(site 080, station 05417480, sampled 

June 26, 2001; fig. 1)

2,6-Diethylaniline, dissolved (μg/L) <0.002 <0.002

Acetochlor, dissolved (μg/L) .024 .179

Alachlor, dissolved (μg/L) .007 <.002

Atrazine, dissolved (μg/L) .613 1.48

Azinphos-methyl, dissolved (μg/L) <.050 <.050

Benfluralin, dissolved (μg/L) <.010 <.010

Butylate, dissolved (μg/L) <.002 <.002

Carbaryl, dissolved (μg/L) <.041 <.041

Carbofuran, dissolved (μg/L) E.007 E.072

Chlorpyrifos, dissolved (μg/L) <.005 <.005

cis-Permethrin, dissolved (μg/L) <.006 <.006

Cyanazine, dissolved (μg/L) <.018 E.004

Dacthal, dissolved (μg/L) <.003 <.003

Deethylatrazine, dissolved (μg/L) E.081 E.109

Diazinon, dissolved (μg/L) <.005 <.005

Dieldrin, dissolved (μg/L) <.005 <.005

Disulfoton, dissolved (μg/L) <.021 <0.21

EPTC, dissolved (μg/L) <.002 <.002

Ethalfluralin, dissolved (μg/L) <0.009 <0.009

Ethoprophos, dissolved (μg/L) <.005 <.005

Fonofos, dissolved (μg/L) <.003 <.003

Lindane, dissolved (μg/L) <.004 <.004

Linuron, dissolved (μg/L) <.035 <.035

Malathion, dissolved (μg/L) <.027 <.027

Metolachlor, dissolved (μg/L) .142 .448

Metribuzin, dissolved (μg/L) <.006 <.006

Molinate, dissolved (μg/L) <.002 <.002

Napropamide, dissolved (μg/L) <.007 <.007

P,P’-DDE, dissolved (μg/L) <.003 <.003

Parathion, dissolved (μg/L) <.007 <.007

Parathion-methyl, dissolved (μg/L) <.006 <.006

Pebulate, dissolved (μg/L) <.002 <.002

Pendimethalin, dissolved (μg/L) <.010 <.010

Phorate, dissolved (μg/L) <.011 <.011

Prometon, dissolved (μg/L) E.004 E.004

Table 12. Pesticide concentrations in water samples collected at selected sites near or at Lake Delhi, eastern Iowa, June 2001

[μg/L, micrograms per liter; <, less than; E, estimated; U, analyzed for but not detected]
Supplemental Data 35

Propachlor, dissolved (μg/L) <0.010 <0.010

Propanil, dissolved (μg/L) <.011 <.011

Propargite, dissolved (μg/L) <.023 <.023

Simazine, dissolved (μg/L) E.004 E.007

Tebuthiuron, dissolved (μg/L) E.004 <.016

Terbacil, dissolved (μg/L) <.034 <.034

Terbufos, dissolved (μg/L) <.017 <.017

Thiobencarb, dissolved (μg/L) <.005 <.005

Triallate, dissolved (μg/L) <.002 <.002

Trifluralin, dissolved (μg/L) <.009 <.009

Table 12. Pesticide concentrations in water samples collected at selected sites near or at Lake Delhi, eastern Iowa, June 2001—Continued

Pesticide compound 

(unit of measurement)

Maquoketa River at Manchester, Iowa

(site 010, station 05416900, sampled 

June 27, 2001; fig. 1)

Lake Delhi near dam 

(site 080, station 05417480, sampled 

June 26, 2001; fig. 1)
36 Bathynetric mapping, Sediment Quality, and Water Quality of Lake Delhi, 2001–02 Table 13. Major-ion and trace-metal concentrations in water samples collected from Marquoketa River, tributary, and lake sites, Lake Delhi, eastern Iowa, Jun

Local site number (fig. 1) Station number Station name Sampling date (month/day/year) Time of sample collection (24-hour) Hardness, total (mg/L as CaCO3) Cal

diss

(mg/

010 05416900 Maquoketa River at Manchester, Iowa 6/27/2001 1755 260 7

9/20/2001 810 250 73/19/2002 1545 250 6

015 05417170 Unnamed tributary near Bailey Ford 6/27/2001 955 240 7

9/20/2001 1230 270 83/19/2002 1445 240 7

020 05417200 Upstream Lake Delhi near The Cedars 6/27/2001 835 250 7

9/20/2001 935 240 63/19/2002 1245 240 6

030 05417275 Unnamed Creek at County Highway 267 and 205 Avenue 6/27/2001 1215 250 6

9/19/2001 1050 210 53/19/2002 1400 230 6

040 05417300 Turtle Creek at Turtle Creek recreation area 6/27/2001 1435 270 7

9/19/2001 1550 260 73/19/2002 1115 270 7

050 05417320 Middle Lake Delhi near Linden Acres 6/26/2001 1520 230 6

9/19/2001 1655 230 63/19/2002 1155 240 6

070 05417470 Unnamed tributary at cove near dam 6/26/2001 1150 270 6

9/19/2001 1430 160 33/20/2002 1045 250 6

080 05417480 Downstream Lake Delhi near dam 6/26/2001 1230 240 6

9/19/2001 1330 200 53/20/2002 940 230 6

Table 13. Major-ion and trace-metal concentrations in water samples collected from Marquoketa River, tributary, and lake sites, Lake Delhi, eastern Iowa, Jun[mg/L, milligrams per liter; CaCO3, calcium carbonate; Ca, calcium; Cl, chloride; F, fluoride; Mg, magnesium; K, potassium; SiO2, silica; Na, sodium; SO4, sulfa

Ba, barium; Be, beryllium; Cd, cadmium; Cr, chromium; Co, cobalt; Cu, copper; Fe, iron, Pb, lead; Li, lithium; Mn, manganese; Mo, molybdenum; Ni, nickel, Ag

Zn, zinc; --, no data; M, presence verified but not quantified; <, less than; E, estimated value]
Supplemental Data 37

Table 13. Major-ion and trace-metal concentrations for water samples collected from river, tributary, and lake sites for Lake Delhi, eastern Iowa, September 2001 

Local site 

number

(fig. 1)

Station

number

Sampling date 

(month/day/year)

Magnesium,

dissolved

(mg/L as Mg)

Potassium,

dissolved

(mg/L as K)

Silica, 

dissolved 

(mg/L as SiO2)

Sodium,

dissolved

(mg/L as Na)

Sulfate,

dissolved

(mg/L as 

SO4)

Barium,

dissolved

(μg/L as Ba)

Beryllium,

dissolved

(μg/L as Be)

C

d

(μ

010 05416900 6/27/2001 18.8 1.77 11.0 8.7 25.7 -- -- 

9/20/2001 17.3 -- 11.7 7.7 -- 80.5 <1.00 3/19/2002 18.6 -- 7.6 11.7 -- 67.9 E.720 

015 05417170 6/27/2001 14.0 1.60 10.8 5.1 20.2 -- -- 

9/20/2001 15.7 -- 11.8 7.5 -- 76.7 <1.00 3/19/2002 13.4 -- 7.9 6.4 -- 73.3 E.850 

020 05417200 6/27/2001 17.9 1.59 10.2 7.8 25.1 -- -- 

9/20/2001 17.2 -- 11.3 8.2 -- 77.5 <1.00 3/19/2002 17.7 -- 6.6 8.5 -- 63.8 1.15 

030 05417275 6/27/2001 20.1 1.27 13.4 7.3 21.9 -- -- 

9/19/2001 16.3 -- 14.7 10.6 -- 125 <1.00 3/19/2002 17.7 -- 10.5 8.2 -- 111 E.760 

040 05417300 6/27/2001 22.1 4.19 12.8 6.6 23.1 -- -- 

9/19/2001 19.7 -- 14.6 8.1 -- 100 <1.00 3/19/2002 22.8 -- 8.6 6.3 -- 85.8 1.25 

050 05417320 6/26/2001 16.3 1.82 10.3 6.2 21.2 -- -- 

9/19/2001 18.0 -- 10.6 7.4 -- 73 <1.00 3/19/2002 17.8 -- 6.8 8.8 -- 63.9 E.730 

070 05417470 6/26/2001 26.0 4.58 8.1 8.2 14.4 -- -- 

9/19/2001 15.5 -- 7.8 7.2 -- 67.2 <1.00 3/20/2002 24.5 -- 5.3 8.2 -- 70.3 1.21 

080 05417480 6/26/2001 16.4 1.87 10.2 6.8 21.4 -- -- 

9/19/2001 16.8 -- 8.8 6.9 -- 69 <1.00 3/20/2002 17.5 -- 7.3 7.4 -- 64.4 E.810 
38 Bathynetric mapping, Sediment Quality, and Water Quality of Lake Delhi, 2001–02 Table 13. Major-ion and trace-metal concentrations for water samples collected from river, tributary, and lake sites for Lake Delhi, eastern Iowa, September 2001 

Local site number (fig. 1) Station number Sampling date (month/day/year) Copper, dissolved (μg/L as Cu) Iron, dissolved (μg/L as Fe) Lead, dissolved (μg/L as Pb) Lithium, dissolved (μg/L as Li) Manganese, dissolved (μg/L as Mn) Molybde- num, dissolved (μg/L as Mo) Nickel, dissolved (μg/L as Ni) Silver, dissolved (μg/L as Ag) S

(

010 05416900 6/27/2001 -- <10 -- -- 13.9 -- -- -- 

9/20/2001 <5.0 M <0.08 <4.0 7.8 <50.0 <50.0 <5.0 3/19/2002 <6.0 20 .08 E2.4 26.1 <50.0 <30.0 <9.0 

015 05417170 6/27/2001 -- <10 -- -- 35.0 -- -- -- 

9/20/2001 <5.0 40 E.06 E2.5 52.1 <50.0 <50.0 <5.0 3/19/2002 <6.0 40 E.06 <4.0 29.4 <50.0 <30.0 <9.0 

020 05417200 6/27/2001 -- <10 -- -- 14.2 -- -- -- 

9/20/2001 <5.0 M <.08 <4.0 9.1 <50.0 <50.0 <5.0 3/19/2002 <6.0 20 .1 <4.0 42.8 <50.0 <30.0 <9.0 

030 05417275 6/27/2001 -- <10 -- -- 26.4 -- -- -- 

9/19/2001 E2.6 20 <.08 <4.0 94.5 <50.0 <50.0 <5.0 3/19/2002 <6.0 <10 <.08 E2.1 27.0 <50.0 <30.0 <9.0 

040 05417300 6/27/2001 -- <10 -- -- 118 -- -- -- 

9/19/2001 <5.0 30 .24 E2.1 73.5 <50.0 <50.0 <5.0 3/19/2002 <6.0 10 E.05 E2.0 62.5 <50.0 <30.0 <9.0 

050 05417320 6/26/2001 -- <10 -- -- 12.5 -- -- -- 

9/19/2001 <5.0 <10 <.08 <4.0 6.7 <50.0 <50.0 <5.0 3/19/2002 <6.0 M .08 <4.0 24.1 <50.0 <30.0 <9.0 

070 05417470 6/26/2001 -- <10 -- -- 10.2 -- -- -- 

9/19/2001 <5.0 30 .22 <4.0 58.9 <50.0 <50.0 <5.0 3/20/2002 <6.0 40 <.08 E3.4 31.1 <50.0 <30.0 <9.0 

080 05417480 6/26/2001 -- <10 -- -- <3.0 -- -- -- 

9/19/2001 <5.0 <10 .1 <4.0 <3.0 <50.0 <50.0 <5.0 3/20/2002 <6.0 <10 <.08 <4.0 13.5 <50.0 <30.0 <9.0