Kansas Water Science Center
Quality and Hydrology of Streams and Lakes in Johnson County, Kansas
Johnson County is the most populated county in Kansas with 544,000 people in 2010, a 21 percent increase in population since 2000, according to the U.S. Census Bureau. Located in northeastern Kansas, about half of the county is suburban as part of the Kansas City metropolitan area, and the remainder is rural. Urban, industrial, and agricultural land uses affect the water quality of streams and lakes in the county. Water-quality impairments related to excessive nutrients, sediment, and bacteria have been identified by the Kansas Department of Health and Environment. Several past and ongoing studies related to hydrology and stream quality have been conducted by the USGS. Information obtained from the studies is being used to better understand streamflow characteristics such as flooding and urban hydrology and factors that affect water quality and ecosystem health. In addition, these studies identify current and changing conditions and help municipalities address regulatory requirements related to the Clean Water Act. A brief summary of stream and lake information related to streamflow, urbanization, stormwater, wastewater, biology, suspended sediment, nutrients, bacteria, and pesticides and organic compounds is provided below. Additional information can be obtained by following the links at the bottom of this page.
Active stream and lake data-collection sites in and near Johnson County, Kansas
Johnson County's first streamflow gage was established in 1963 in Overland Park (06893300). Currently real-time streamflow data are available at 9 sites in the county and continuous, real-time water-quality data are available at 2 sites (06893100,06893390) in the county.
The quality of rural streams in Johnson County was generally better than the quality of urban streams.
Discharges from wastewater treatment facilities affect all of the major streams in Johnson County. Generally, wastewater discharges have been found to be a primary source of nutrients, but not indicator bacteria, in county streams (Rasmussen and others, 2008). Concentrations of nutrients, some metals, and most organic wastewater compounds were largest in streambed sediment samples collected immediately downstream from wastewater discharges (Lee and others, 2005). At the Kansas River at DeSoto from 2000-03, about 11 percent of the total nitrogen load and 12 percent of the total phosphorus load originated from upstream wastewater treatment facilities (Rasmussen and others, 2005). Wastewater discharges in the upper Blue River in 2008 were determined to cause substantial changes in water quality and biology but not in ecosystem function (Graham and others, 2010). The lower Blue River in downstream Kansas City, Missouri, is also affected by wastewater discharges (Wilkison and others, 2002; Wilkison and others, 2009).
As impervious surface area increased, biological quality of streams generally decreased.
Excessive suspended sediment negatively affects water quality. During 2006-08, suspended sediment in the Mill Creek watershed was largest in streams downstream from construction sites (Lee and others, 2009). Indian Creek, the most urban stream in the county, transports the most stormflow and sediment of both small and large streams. Of the total suspended sediment load transported in 2005-06 in the 5 major watersheds of the county, 90 percent or more occurred during less than 2 percent of the time, generally during large storm runoff (Rasmussen and others, 2008).
Wastewater treatment facilities contribute to nutrient loads in some streams.
Indicator bacteria densities in urban Johnson County streams generally were larger than in rural streams (Lee and others, 2005). During 2005-07, less than 3 percent of the total fecal coliform bacteria load in Indian Creek and the Blue River originated from wastewater treatment facilities, indicating that 97 percent of bacteria originated from nonpoint sources during storm runoff (Rasmussen and others, 2005).
Areas of sediment deposition in Lake Olathe, 1956-2000.
Equipment used to measure and transmit real-time streamflow and water-quality data in Johnson County.
Urbanization has affected water and biological quality of streams and lakes in Johnson County. Sediment and nutrient concentrations and indicator bacteria densities generally are larger in urban watersheds (Lee and others, 2005; Rasmussen and others, 2008; Lee and others, 2009). In addition more organic compounds have been detected in urban streams compared to rural streams (Lee and others, 2005; Rasmussen and others, 2009). Biological stream quality, determined using aquatic insect data, generally decreased as urbanization increased (Poulton and others, 2007; Rasmussen and others, 2009). Stormwater runoff is a leading contributor to contaminants in streams and lakes of Johnson County (Rasmussen and Schmidt, 2009). The largest amounts of sediment, nutrients, and indicator bacteria occur during stormwater runoff indicating that nonpoint sources of contaminants are common throughout the county (Lee and others, 2005; Rasmussen and others, 2008).
Discharge of treated wastewater into the Blue River.
The biological condition of Johnson County streams indicates minimal impacts from human disturbance have occurred at some sites and high impacts at others (Poulton and others, 2007; Rasmussen and others, 2009). Generally, as impervious surface area (a general indication of urbanization) increases, biological stream quality decreases. Environmental factors that are strongly correlated to stream quality include amount of upstream urbanization, stream sinuosity, and riparian buffer condition (Rasmussen and others, 2009).
Indian Creek, the largest and most urbanized watershed in Johnson County, transported the most sediment.
Nutrients (nitrogen and phosphorus) in Johnson County streams and lakes originate primarily from stormwater runoff and wastewater treatment facilities (Lee and others, 2005; Rasmussen and others, 2008). In addition, phosphorus released from bottom sediments contributed to phosphorus concentrations in Lake Olathe during 2000-02 (Mau and others, 2004). Generally, the largest nutrient concentrations in streams occurred during storm runoff. During baseflow, the largest nutrient concentrations occurred downstream from wastewater treatment discharges (Lee and others, 2005). The Blue River in and downstream from Johnson County is affected by nutrients (Wilkison and others, 2006; Graham and others, 2010). During 2001-02 point sources to the Kansas River in and upstream from Johnson County were found to be the primary contributors of ammonia and other nutrients to the Kansas River during base-flow (Rasmussen and others, 2005).
Stormwater runoff was the largest source of indicator bacteria in streams.
Pesticides and organic compounds have been detected in most streams in the county (Lee and others, 2005; Poulton and others, 2007; Rasmussen and others, 2009). During baseflow, water samples from urban streams had the largest number of pesticide compounds detected, and water samples from rural sites had the largest total concentration of pesticides (Lee and others, 2005). The largest concentrations of organic wastewater compounds and pharmaceuticals occurred at stream sites at or immediately downstream from wastewater treatment facilities (Lee and others, 2005).
Lakes and reservoirs with watersheds in Johnson County have been studied to describe sediment deposition and water quality. Nutrients in Lake Olathe during 2000-02 originated from Cedar Creek and releases from bottom sediment (Mau and others, 2004). Phosphorus loads to Hillsdale Lake during 1981-1996 originating from point sources was about 7 percent and from nonpoint sources about 93 percent (Juracek and others, 1997). During 1994-95 Big Bull and Little Bull Creeks contributed the largest phosphorus loads to Hillsdale Lake (Putnam, 1997).