Handbook for Lake Wabaunsee Water Quality Protection
David C. Schroeder, May 20, 1999
Lake Wabaunsee is located in Wabaunsee County, Kansas, about 30 miles southwest of Topeka. It is a relatively small lake, with a surface area of 210 acres and a maximum depth of 40 feet. Its drainage area in the Flint Hills region is 6700 acres (31 times as large as the lake area). Grassland and native vegetation make up 97% of the drainage area while the remaining 3% is occupied by homes and other structures in the immediate vicinity of the lake.
The lake is used for drinking water, contact recreation, wildlife habitat, and appreciation of its scenic beauty. It’s water quality was assessed as a part of the KDHE Lake and Wetland Monitoring program in 1985, 1988 and 1993. Additional measurements were made in 1997. Lake water quality was judged to be very good but requiring efforts to maintain that quality, given the likelihood that lake usage will increase due to its appeal and its close proximity to a major urban area.
A major step toward protecting water quality was made with the installation of a sewage collection system in 1990, replacing septic tanks that, even when properly operated, leak nutrients into the surrounding soil and probably into the lake. Current potential pollution sources include excessive fertilizer use on lawns and agricultural lands, animal waste from livestock, spills of solvents and fuels, improper pesticide use, soil erosion, and erosion of banks and sediments by power boats.
In 1996, the Wabaunsee Lake Water Resource Board, in cooperation with the Kansas Department of Health and Environment, decided to sponsor a detailed study of current lake conditions in order to maintain water quality and to identify any developing problems. This report summarizes the results of that study.
To identify current lake conditions, especially in regard to nutrients and pesticides,
To determine the current level of algal activity,
To prepare recommendations for the development of a water quality management plan for the lake to intend to maintain, or if necessary, to improve water quality,
To conduct a Clean Water Neighbor workshop to communicate project results to lake users, local policy makers, and other interested parties.
Approach and Methods
Surface water samples were collected twice a month, with longer sampling intervals during the winter, for one year beginning in July 1997. One set of samples, collected from five sites in the lake, was analyzed for coliform bacteria at the Kansas Department of Health and Environment laboratory at Forbes Field. Another set, from the same five sites, was analyzed for nutrients, chlorophyll, conductivity, and alkalinity at the Department of Chemistry laboratory at Emporia State University. Samples from two sites were analyzed for pesticides at the KDHE laboratory. Dissolved oxygen was measured every two to three months, including surface measurement at each site and a surface-to-bottom profile at the deepest part of the lake.
Water samples were tested for 43 organic contaminants (pesticides and related substances). In 30 water samples collected on 15 dates, none were detected. Some are probably not used in the watershed, and others apparently enter the lake at rates too low to be detected in the water. They may still be present in the lake sediment and in the tissues of wildlife, however.
Many species of bacteria are native to lakes, performing vital functions and posing no threat to humans or to water quality. Other bacteria, especially fecal coliform and fecal streptococci, are native to the digestive tracts of warm-blooded animals. When present in lake water in significant numbers, these coliform bacteria indicate the presence of animal waste, which can also transmit disease-causing organisms. The water is then judged unsuitable for contact recreation and requires extensive disinfect ion before use and drinking water.
For contact recreation, the State of Kansas Water Quality Standard states that the geometric mean of five or more consecutive samples over a 30-day period should not exceed 200 colonies per 100 mL, and no more that 10 percent can be greater than 400 colonies per 100 mL.
This project was not designed to identify violations of the standard, but to indicate where more date may be needed. On all but two sampling dates, the coliform counts were very low. On two dates in the fall of 1997, the numbers were much higher, possibly caused by migrating waterfowl, which were abundant at that time, or animals in the watershed.
Chlorophyll is the green pigment in plants and algae. In lakes, the chlorophyll concentration is a measure of the abundance of algae. Concentrations between 3 & 10 parts per billion (ppb) in the water indicate a healthy, balanced ecosystem. High concentrations, above 10 ppb indicate an overabundance of algae, usually resulting in undesirable tastes and odors in drinking water and possibly disrupting the oxygen supply to fish and other aquatic animals below the thermocline but not generally.
This condition, known as eutrophication, is a common one in lakes of the central US, especially in regions with high population or intense agriculture. Because Lake Wabaunsee is located in a drainage basin with very little fertilized cropland and because of the sewage collection system, this lake should be receiving very low nutrient amounts.
The results of chlorophyll measurements in 72 lake samples during the study period were averaged for the five sites on a given day. The values ranged from 3 ppb to 15 ppb. The overall average, 9.4 ppb, was not excessive, but 40% of the samples had chlorophyll levels above 10 ppb. The previous studies found an average chlorophyll concentration of only 4.25 ppb. Since the chlorophyll concentration varies over a wide range from week to week, the difference may be due to pure chance, or a difference in methods of analysis, or it may indicate a developing algae problem.
Phosphorus is a nutrient for plants and algae, originating in fertilizers, detergents, animal wastes, and natural decomposition of plant and animal remains. In lakes, it is often the "limiting factor": added phosphorus frequently causes increases in plant and algal growth. High phosphorus levels almost always result in high chlorophyll content. Lakes with average phosphorus concentrations above 30 ppb, a very common situation in Kansas lakes, are considered eutrophic and usually have algal problems.
The phosphorus concentrations during the study period averaged 26 ppb, about the same as the previous studies (33 ppb average). Like the chlorophyll results, this indicates a "borderline" condition, nearly eutrophic.
The observed average chlorophyll concentration (see Chlorophyll) is about the same as in other lakes around the world with this level of phosphorus where phosphorus is the limiting factor. Based on the pattern seen in other lakes, phosphorus is probably the limiting factor in Lake Wabaunsee. An increase in phosphorus concentration is likely to stimulate algal blooms.
Like phosphorus, nitrogen is a nutrient for plants and algae. It occurs in water in several forms, including nitrate, nitrite, ammonia, organic nitrogen, and dissolved nitrogen gas. Algae require about seven times as much nitrogen as phosphorus (on a weight basis), so eutrophic lakes typically average 200 ppb nitrogen or higher. To support the average chlorophyll level in Lake Wabaunsee would require an average nitrogen concentration of 182 ppb.
The cyanobacteria, commonly known as "blue-green algae", can use nitrogen gas, unlike other algae. In general, blue-green algae are more likely to cause blooms and related water quality problems but are usually found in water with higher phosphorus levels that observed in Lake Wabaunsee. A follow-up study to determine relative numbers of the types of algae would be useful.
All aquatic animals, including fish, breathe oxygen gas dissolved in the water. Oxygen is also consumed by bacteria in the process of breaking down organic matter. At the lake surface, this oxygen is replaced by absorption from the air and by photosynthesis in plants and algae, powered by sunlight. In deeper water, where light does not penetrate, the dissolved oxygen can become depleted.
This depletion can be especially pronounced in the deeper water during the summer. The surface water, warmed by the air and sun, expands and floats atop the deeper, cooler water. The region where the two meet is called the thermocline, and it acts as a barrier to mixing. Organic debris settling into the lower region is decomposed by bacteria, causing oxygen depletion.
One type of organic debris is dead algae following a "bloom". Lakes with high and fluctuating chlorophyll levels at the surface typically have oxygen depletion in the deep water during the summer. Organic debris can also wash into the lake from the surroundings, so deep-water oxygen depletion does not necessarily indicate algal blooms, but deep-water oxygen depletion is considered another sign of eutrophication.
Lake Wabaunsee’s temperature and oxygen profile, taken on June 27, 1998, is natural for any mid-latitude lake that is at least 10 meters (30 feet) deep. The termocline occurred at a depth of 8 to 9 meters. Dissolved oxygen was high at the surface, deceased sharply at the thermocline, and was completely depleted in the bottom, indicating that the bottom water is receiving organic debris of some sort.
Only a small portion of the lake volume lies below the thermocline, so this oxygen depletion has little effect on the lake as a whole, but the cause and rate of depletion warrant further study.
Conductivity is the ability of the water to conduct electricity and is caused by charged particles, called ions, in the water. Several substances, such as calcium, magnesium, sodium, potassium, chloride, sulfate, and bicarbonate, occur mainly in water as ions and contribute to conductivity. The higher the measured conductivity, the higher the concentration of ions. In Lake Wabaunsee, these come mainly (and naturally) from the slow breakdown of limestone rock in the drainage area.
One use of conductivity measurements is to identify wet or day periods. Rain is very low in conductivity, so the lake conductivity drops during wet periods. The result shown in the fall of 1997 indicate it was relatively wet and the spring of 1998 was dry. These may explain the decline in phosphorus levels in 1998; runoff from rainfall adds phosphorus to the lake from the surroundings during wet periods, and algae will gradually deplete the lake phosphorus during wet periods, and algae will gradually deplete the lake phosphorus during extended dry periods.
The sudden changes during February, April and May 1998 accompanied large temperature changes and probably result from chemical changes in the lake. It is interesting to note that a similar pattern occurred with chlorophyll, indicating changes in the biological activity as well. In any case, in a small lake such as Lake Wabaunsee, changes can occur abruptly.
Lake water can become turbid from two main causes: eroding soil, especially if high in clay content, and algal growth. The clarity of water is measured by lowering a black and white disk (called a Secchi disk) into the water until it just disappears and noting the depth of the disk. Lakes without algae problems and not receiving substantial erosion typically have Secchi depths of two meters (six feet) or more, although one meter is considered good for Kansas lakes.
The average Secchi depth in Lake Wabaunsee was one meter, about the same as the previous studies. Algal growths, bank erosion within the lake, resuspension of bottom sediment in shallow areas, and soil erosion from the surrounding watershed all contribute to the turbidity.
Summary and Conclusions
1. No pesticides were detected in the lake water.
2. Coliform bacteria counts were very low except on two dates when migratory waterfowl were abundant.
3. Chlorophyll, phosphorus, water clarity, and oxygen measurements indicate that algal activity in the lake may be increasing.
4. The Water Quality Management plan should attempt to control phosphorus levels, since phosphorus appears to be the key factor in controlling algal activity.
Comments on this report are welcome. They can be addressed to:
David C Schroeder 620-341-5989
Division of Physical Sciences, Box 4030
Emporia State University
Emporia, KS 66801
Water Quality Protection Measures: Lake Wabaunsee & Watershed
1. Pesticides and Fertilizers
Concerns: Excess nutrients, toxic chemicals
A. Follow label (application) instructions and rates
B. Avoid application before intense storms
C. Use effective alternatives
D. Scout pests and test soils before treating
E. Use anti-back-siphon devices on spigots
F. Apply away from water resources
G. Avoid windy conditions
H. Dispose of containers properly and either give (over the counter) away what is left of take to a household hazardous waste collection site
I. Use composted material to add nutrients and structure to soil
2. Maintenance and Mechanical Fluids: Fuels, solvents, oil, deicers, etc.
Concerns: Toxic Chemicals, heavy metals
A. Avoid spills by not topping off tank, storing in stable containers, checking hoses and containers for cracks
B. Properly dispose of fluids and containers
C. Use environmentally- sound alternative cleaners
D. Contain rinse from greasy/oil-treated parts
E. Keep all water craft/mechanical equipment/storage tanks/hoses in good repair
F. Dispose of waste oil at a recognized collection site
Spills which potentially threaten water quality, human health, or property should be reported immediately to the following agencies:
Wabaunsee County Sheriff 785-765-3323
KDHE Central Office: 785-296-0614
3. Animal Areas
Concerns: Nutrient, bacteria, organic matter
A. Avoid concentrating feeding, shelter, and/or watering by giving alternatives to these sites or occasionally moving the site.
B. Avoid concentrating waterfowl populations by feeding or other attractions, especially around the swimming area and drinking water intake.
C. Fish remains or dead fish should be buried on your own property and can be used as garden or shrub fertilizer.
4. Solid Waste (non-biodegradable)
Concerns: litter, trash, pest animal attraction
A. Reduce, recycle, and reuse
B. Dispose of in designated receptacles
C. Mulch mow
D. Compost leaves, limbs, non-animal waste, organic kitchen waste
E. Avoid discharging grass from lawn mower directly into lake. Don’t dump grass and yard waste in ditches or streams leading to the lake.
5. Erosion/silt control during construction and maintenance
Concerns: Silt, sediment, turbidity
A. Mulch bareground areas
B. Construct silt fences
C. Stabilize banks with structures or vegetation
D. Use quick seeding on bare ground
E. Avoid making steep slopes
F. Divert runoff
G. Add trees and grass plantings
Any project disturbing more than 5 acres should contact KDHE, 785-296-5547, to inquire about a water quality protection permit (NPDES).
6. Volunteer Monitoring
Concerns: Regular collection of information
A. Rainfall, storm event information
B. Temperature, pH, dissolved oxygen, etc.
C. Secchi Disk depths (water clarity)
D. Aquatic life (algae, rooted plants, fish, other)
E. Waterfowl counts