Continuous Real-Time Water-Quality Monitoring for TMDLs in the Lower Kansas River Basin

Water-quality information is available from 1999 to 2005. Funding to maintain the continuous water-quality monitors on the Kansas River ended on September 30, 2005.

Kansas River near DeSoto.

BACKGROUND

The Kansas River is an important source of drinking water for hundreds of thousands of people in northeast Kansas. Rapid population growth has resulted in an increasing interest in issues related to water quality in the river. Most water-quality impairments in the lower Kansas River Basin, cited by the U.S. Environmental Protection Agency and the Kansas Department of Health and Environment, are caused by excessive concentrations of nutrients, sulfate, bacteria, and sediment.

OBJECTIVES

The objectives of this study are to:

Maintain a continuous, real-time, water-quality network on the lower Kansas River.
Develop statistical relations between commonly measured water-quality characteristics and constituents of concern.
Estimate loads and variability for nutrients, suspended sediment, dissolved solids, bacteria, and major ions in the lower Kansas River under different seasonal, temporal, and flow conditions.
Develop the relation between E. coli and fecal coliform bacteria.

(Figure 1.) Location of real-time water-quality monitors on Kansas River.

Table 2. Estimated
mean annual net phosphorus yield for several reservoirs in Kansas.

(Figure 2.) Water-quality monitor used to measure specific conductance, pH, water temperature, dissolved oxygen, and turbidity in the Kansas River.

APPROACH

Continuous real-time water-quality monitors were installed at three locations along the Kansas River from July 1999 through September 2005 (fig. 1) to provide continuous measurement of specific conductance, pH, water temperature, dissolved oxygen, and turbidity (fig. 2). Water-quality samples were collected from those locations and analyzed for nutrients, bacteria, suspended sediment, and other constituents. Regression equations were developed relating the continuous data to the sampled data. Using this method, it is possible to estimate chemicals of concern, such as bacteria, nitrogen, phosphorus, sulfate, chloride, and others, in real time and make the estimates available on the USGS Web site. Estimates of concentration also were used to estimate constituent loads and yields from the watershed under various seasonal, temporal, and flow conditions.

RESULTS

Water quality in the Kansas River is affected primarily by nonpoint sources during storm runoff.

Sediment, nutrients, and bacteria were substantially larger during periods of increased streamflow.
On average, 63 percent of the annual suspended sediment load, 40 percent of the annual nutrient load, and 83 percent of the annual bacteria load at DeSoto during 2000-03 occurred during 10 percent of the time, generally during storms.

Dissolved oxygen concentrations in the Kansas River met the minimum water-quality criterion of 5 mg/L at the 3 monitoring sites (Wamego, Topeka, DeSoto) 99 percent of the time.

pH in the Kansas River remained well above the lower criterion of 6.5 at all sites and exceeded the upper criterion of 8.5 between 2 percent (Wamego in 2001) and 65 percent (DeSoto in 2003) of the time. Larger pH values generally coincided with warmer temperatures and lower streamflow conditions.

Turbidity can vary by two orders of magnitude in less than an hour. Turbidity is an important water-quality characteristic because it is closely related to suspended sediment, nitrogen, phosphorus, and bacteria.

About 11 percent of the total nitrogen load and 12 percent of the total phosphorus load at DeSoto from 2000-03 originated from wastewater-treatment facilities.

Most of the time, the largest E.Coli bacteria densities occurred at Topeka.

Similar nutrient yields at the 3 monitoring sites indicate that nutrient sources were evenly distributed throughout the basin.

About 17 percent of the sand removed from the Kansas River in 2003 by commercial dredging operations was replenished by transport of suspended sediment in the water column. The quantity of sand transported in the bedload is unknown.

BENEFITS

A system for continuously monitoring water-quality constituents in real time has numerous advantages over traditional water-quality studies relying on sampling alone. It provides continuous data so that daily, seasonal, and event-driven fluctuations are not missed. It makes it possible to immediately recognize changes in water-quality conditions. It allows the timing of sample collection to be optimized to keep costs associated with water-quality monitoring at a minimum. Finally, it provides a framework for estimating concentrations of important water-quality constituents, with statistically defined uncertainty, as they are occurring in the river. These benefits are shared by water-management officials, water-treatment-plant managers, boaters and fishermen, the general public, and water scientists.