Understanding Lake Data - Page 1

CONTENTS - Page 2

• ............................................................................Page
• PHYSICAL CHARACTERISTICS....................3
• Lake types...................................................3
• Water source...............................................3
• Mixing and stratification................................4
• Retention time..............................................5
• Drainage basin/lake area ratio(DB:LA).........5
• Lake water levels.........................................6
• Water clarity................................................6
• Trophic state................................................7
• CHEMICAL PROPERTIES..............................8
• Phosphorus.................................................8
• Nitrogen......................................................9
• Chloride....................................................11
• Sulfate.......................................................11
• Sodium and potassium...............................12
• DISSOLVED GASES.......................................12
• Oxygen.....................................................12
• Carbon dioxide.........................................13
• Nitrogen gas.............................................14
• Other gases..............................................14
• CARBONATE SYSTEMS..............................14
• pH-acidity................................................14
• Alkalinity and hardness.............................15
• Alkalinity-a lake's buffer against acid rain..15
• Marl deposits...........................................16
• SUMMARY.....................................................16
• BIBLIOGRAPHY AND ADDITIONAL REFERENCES.17
• GLOSSARY....................................................17-20

THIS GUIDE WAS WRITTEN to help people understand information about lake water quality and to interpret lake data. Each lake possesses a unique "personality," or set of physical and chemical characteristics which may change over time. Lakes exhibit chemical changes on a daily basis while other changes, such as plant and algae growth, occur seasonally.

Year-to-year changes in a lake are common because surface runoff, groundwater inflow, precipitation, temperature and sunlight vary. For example, the loss of dissolved oxygen can destroy a lake's fish population, but may improve water clarity. Eliminating fish allows algae-eating zooplankton (microscopic animals) to increase, which might reduce algae populations. Because of changes like these, data from several years are needed to show whether a lake is experiencing significant changes in water quality.

This publication explains the physical and chemical compositions of different types of lakes. It covers lakes' nutrient status (trophic condition), and their susceptibility to acid rain. It discusses toxic metals that accumulate in fish and tells how to use general water chemistry principles to document potential changes in water quality. A glossary of technical terms is included to help the reader understand the language used in the study of lakes (limnology).

Cover art by Dan Shaw

Authors:
Byron Shaw is a professor of soil and water science, University of Wisconsin-Stevens Point, and a water quality specialist with the University of Wisconsin-Extension, Cooperative Extension.
Lowell Klessig is a professor of resource management at the University of Wisconsin-Stevens Point, and a lake management specialist with the University of Wisconsin-Extension, Cooperative Extension.
Christine Mechenich is an Extension groundwater education specialist with the Central Wisconsin Groundwater Center, University of Wisconsin-Stevens Point.

An equal opportunity/affirmative action employer, University of Wisconsin-Extension provides equal opportunities in employment and programming, including Title IX requirements.

This publication (exit DNR) is available from your Wisconsin county Extension office or from Extension Publications (exit DNR Web Pages), Rm. 170, 630 W. Mifflin St., Madison, WI 53703, or by calling (608)262-3346.
G3582 Understanding Lake Data RP-09-96-3M-275

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For more information on this topic, contact:

James Vennie
Watershed Management
(608) 266-2212

Lakes Partnership | Watershed Management | Fish Wisconsin | Fisheries Management