Determination of Ammonia Concentrations in the Kansas River during Stable, Low-Flow Conditions

Point-source pollution

The Kansas River drains about 60,000 square miles in Colorado, Nebraska, and Kansas. The downstream part of the drainage basin in northern Kansas supports a growing population of more than 700,000 people and a wide range of urban and agricultural activities. Along the Kansas River between Wamego and Kansas City, Kansas, there are 16 permitted wastewater discharging sites (see map) with 22 others located on tributary streams. Rapid population growth and urban development are a particular concern along the Kansas River between Topeka and Kansas City. High concentrations of ammonia and bacteria have been detected in this reach of the Kansas River because of the close proximity of communities that discharge to the river and the additive effect of their wastewater treatment facilities. There are also several proposed wastewater treatment facilities that will discharge to the Kansas River. Before these proposed facilities can be allowed to discharge into the Kansas River, the assimilation capacity for ammonia and bacteria decay rates in the river need to be determined so that water-quality standards are not exceeded.

Objectives

The purpose of this study was to develop a water-quality model to estimate ammonia concentrations in the Kansas River between Topeka and the confluence of the Kansas River with the Missouri River at Kansas City. The study was from April 2001 to January 2005. The specific objectives of the report are to

1. characterize ambient hydrologic and water-quality conditions during the study period from November 2001 to August 2002,
2. document calibration of the CE.QUAL.W2 water-quality model, and
3. present the results of model simulations for selected hypothetical situations describing the effects of an additional WWTF and changes in WWTF effluent discharges on water quality of the Kansas River during low streamflow conditions.

The water-quality model will assist the Kansas Department of Health and Environment in estimating the probable effects of increased wastewater discharge to the Kansas River. In the future, this information can be used with additional data collection and numerical modeling during high-flow conditions to further define Total Maximum Daily Loads (TMDLs) in the Kansas River for ammonia.

A total of 146 samples were collected over three synoptic surveys. These synoptic surveys occurred at low flow during November and February when water temperatures were at annual lows and in July when water temperatures were at annual maximums. Sample collection sites are shown on the map below.