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 U.S. Department of the Interior 

 U.S. Geological Survey 

 Fact Sheet 2005–3093 

 August 2005 

 Prepared in cooperation with the city of Olathe, Kansas 

 Monitoring the Water Quality of Lake 

Olathe, Johnson County, Kansas 

 By Patrick P. Rasmussen1 and DeWayne H. McAllister2 

Printed on recycled paper

 1 U.S. Geological Survey, Lawrence, Kansas. 

 2 City of Olathe, Olathe, Kansas. 

 Photograph showing USGS technician working on the intake structure 

at Lake Olathe. 

 Why Monitor Water Quality? 

 Lake Olathe was built in 1956 and provides recreation and 

supplements the drinking water for an estimated 105,000 residents of Olathe, Kansas (U.S. Census Bureau, 2003). The water 

quality of the lake is affected by land use and activities occurring 

in the Lake Olathe watershed. Since construction of the reservoir, 

drinking water from Lake Olathe has experienced seasonal tasteand-odor problems caused by algae blooms (Lee and Sears, 1985; 

Mau, 2004) and elevated manganese concentrations. Although 

the water can be treated to remove taste and odor, the process is 

expensive, and objectionable taste and odor is not always easy to 

detect because individuals have different sensitivities. During the 

summer months, higher manganese concentrations in the deeper 

parts of the lake also can cause drinking-water-quality issues. 

 An ongoing study of Lake Olathe water quality began in 2000 

as a cooperative agreement between the city of Olathe and the 

U.S. Geological Survey (USGS). As part of the study, sediment 

and chemical transport from the watershed to the reservoir were 

defined, and the monitoring of sediment and chemical transport 

continues. Information from this study assisted city of Olathe 

officials in developing a comprehensive watershed protection 

plan (Lake Olathe Watershed Protection Citizen Advisory Board, 

2004) and currently (2005) is used to inform the drinking-watertreatment managers of Lake Olathe water quality. 

 As part of the study, chemical and biological processes that 

cause taste and odor also are being investigated with the aid of 

a water-quality monitor in Lake Olathe and water samples collected from Cedar Creek (the main tributary to Lake Olathe) and 

Lake Olathe. A profiling water-quality monitor was installed 

in 2005 to monitor ever-changing water-quality conditions at 

various depths in the lake. Measurements at the 5.0-foot depth 

are displayed on the World Wide Web (http:// waterdata.usgs.gov/

ks/nwis/uv/?site_no=06892450) in real time so that water-treatment managers can determine the most desirable water-withdrawal strategies to best meet Olathe’s drinking-water needs. 

 What Causes Taste and Odor? 

 The historical taste-and-odor occurrences observed in water 

from Lake Olathe are caused primarily by a specific group of 

algae called blue-green algae. A healthy lake has a balanced 

algal community that causes little or no taste and odor. This 

balance can be disrupted by any number or combination of the 

following conditions: 

 • Excessive nutrient concentrations (such as nitrogen and 

phosphorus) in the lake promote algal growth. 

 • Sunlight and water temperatures can favor certain algal 

species more than others. 

 • Pesticides applied within the watershed and transported to 

the lake in runoff can affect certain algal species. 

 A disruption of the algal community balance that results in 

blue-green algae becoming the dominant species will frequently 

have a negative effect on the taste and odor of lake water. Compounds released from blue-green algal blooms and the death and 

decay of blue-green algae can result in taste and odor in the water. 

Therefore, maintaining good water quality in the lake reduces the 

possibility of blue-green algal blooms. A blue-green algae sensor 

was installed in 2005 to provide drinking-water managers with 

data to monitor the probability of a taste-and-odor occurrence. 

 What’s Been Done So Far? 

 To gain a historical perspective of the watershed water quality, 

sampling of lake-bottom sediment at Lake Olathe and Cedar Lake 

was done in 2000. Chemical concentrations and diatoms in the 

sediment indicate historical water-quality conditions. Results from 

this part of the study (Mau, 2002) were: 

 • Cedar Lake is effective at trapping sediment that would have 

been deposited in Lake Olathe. 

 • Fifty percent of the original storage capacity of Cedar 

Lake is filled with sediment. 

 • Ten percent of the original storage capacity of Lake 

Olathe is filled with sediment. 

 • Phosphorus concentrations in the bottom sediment of Cedar 

Lake and Lake Olathe are some of the largest values for 

small reservoirs surveyed in eastern Kansas (Juracek, 2004). 

 • Diatoms (microscopic algae) observed in the bottom sediment indicate conditions that were favorable to taste-andodor occurrences throughout much of Lake Olathe’s life. 
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 Figure 1. Dissolved-oxygen concentrations in water at intake structure, 

Lake Olathe, March 4–June 24, 2005. 

 Where Does Olathe’s 

Drinking Water Come 

From? 

 Drinking water for Olathe residents 

comes from aquifers recharged by the 

Kansas River, with Lake Olathe supplementing water supply during high-use, 

summer months. Ninety percent of 

Olathe’s drinking water is pumped from 

wells in the Kansas River alluvium 

and treated and distributed at Water 

Treatment Plant 2. Typically, from July 

to September, Water Treatment Plant 1 

treats and distributes water from Lake 

Olathe, supplementing increased needs 

sustained during summer months. Since 

2000, lake levels have been drawn down 

as much as 8.5 feet during the summer 

months. However, intakes at two different elevations on the intake structure 

allow water to be pumped from the lake 

when lake levels decline (fig. 2). 

 The intake structure also can be 

operated on the basis of water-quality 

conditions. In June 2004, elevated manganese concentrations in the deeper part 

of the lake prompted the city to close 

the lower intake and open the upper 

intake. Although not the case in 2004, 

taste and odor caused by algae blooms 

has been an issue for water pumped 

from the upper intake. 

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 A report describing surface-water-quality conditions in the 

Lake Olathe watershed during 2000−02 was based on waterquality samples and continuous measurement of water-quality 

characteristics (Mau, 2004). Results from this part of the study 

were: 

 • Nitrogen and phosphorus are transported from the watershed to Cedar Creek and Lake Olathe. 

 • Phosphorus is released from the bottom sediment into the 

lake water providing more nutrients to the algal community and possibly increasing the likelihood of taste-andodor occurrences. 

 • Models were developed to estimate the nutrient and tasteand-odor compounds at Lake Olathe and Cedar Creek in 

real time (http://ks.water.usgs.gov/Kansas/rtqw) to help 

water-treatment managers adjust water treatment. Algal 

blooms are best explained by lake-residence time, turbidity, light penetration, and nutrient concentrations. 

 • Algal toxins and taste-and-odor compounds were detected 

at various concentrations in Lake Olathe, but none of the 

concentrations were large enough to adversely affect taste 

and odor of finished drinking water. 

 Currently (2005), USGS is monitoring lake water quality 

by periodically collecting samples from Cedar Creek and Lake 

Olathe and by continuously monitoring various water-quality characteristics, including dissolved oxygen (fig. 1), at both 

intake elevations in the lake. Dissolved-oxygen concentrations 

less than 1.0 milligram per liter indicate the increased possibility of elevated manganese concentrations. Water-quality profile 

measurements are available on the World Wide Web (http://

ks.water.usgs.gov/Kansas/rtqw/) for water-treatment managers to evaluate and determine which intake to use and how to 

optimize water treatment. 

 Further monitoring of the lake water quality will provide the 

city with information to evaluate the effectiveness of recommendations from the Lake Olathe Watershed Protection Citizen 

Advisory Board’s report (2004). Long-term monitoring of Lake 

Olathe will help assess watershed activities that affect the water 

quality of this important source of drinking water and recreation 

for Olathe residents. 

 References Cited 

 Juracek, K.E., 2004, Sedimentation and occurrence and trends of 

selected chemical constituents in bottom sediment of 10 small reservoirs, eastern Kansas: U.S. Geological Survey Scientific Investigations Report 2004–5228, 80 p. 

 Lake Olathe Watershed Protection Citizen Advisory Board, 2004, Lake 

Olathe watershed restoration and protection plan: Olathe, Kansas, 

City Council study session, 77 p. 

 Lee, G.F., and Sears, R.I., 1985, Kansas Clean Lakes Program, Lake 

Olathe: prepared for city of Olathe, Kansas, various pagination. 

 Mau, D.P., 2002, Sediment deposition selected water-quality characteristics in Cedar Lake and Lake Olathe, northeast Kansas, 2000: U.S. 

Geological Survey Water-Resources Investigations Report 02−4073, 

71 p. 

 Mau, D.P., 2004, Surface-water-quality conditions and 

relation to taste-and-odor occurrences in the Lake Olathe 

watershed, northeast Kansas, 2000−02: U.S. Geological 

Survey Scientific Investigations Report 2004−5047, 95 p. 

 U.S. Census Bureau, 2003, Estimated 2003 population 

for Olathe, Kansas: Population Division, information 

available on Web, accessed May 5, 2005, at http://www.

census.gov/popest/cities/tables/SUB-EST2003-04-20.xls 

 For additional information on the water-quality study of the 

Lake Olathe watershed, visit the USGS Web site 

 at 

 http://ks.water.usgs.gov/Kansas/qw/olathe/ 

 or contact 

 the Director of the USGS Kansas Water Scence Center 4821 

Quail Crest Place, Lawrence, Kansas 66049−3839 (785) 

842−9909 or E-mail: dc_ks@usgs.gov 

 Figure 2. Schematic diagram of 

intake structure in Lake Olathe.