The Kansas River and its associated alluvial aquifer provide drinking water to more than 950,000 people in northeastern Kansas. Water suppliers that rely on the Kansas River as a water-supply source use physical and chemical processes to treat and remove contaminants before public distribution. An early-notification system of changing water-quality conditions allows water suppliers to proactively make decisions that affect water treatment. The U.S. Geological Survey (USGS), in cooperation with the Kansas Water Office (funded in part through the Kansas Water Plan), the Kansas Department of Health and Environment, The Nature Conservancy, the City of Lawrence, the City of Manhattan, the City of Olathe, the City of Topeka, WaterOne, and Evergy, began collecting water-quality data at the Kansas River above Topeka Weir at Topeka, Kansas (USGS site 06888990, hereafter referred to as the “Topeka site”), during November 2018 to develop linear regression models that relate continuous in situ water-quality sensor measurements to discretely sampled water-quality constituent concentrations or densities. The addition of the Topeka site expanded an existing water-quality monitoring network, which included the upstream Kansas River at Wamego, Kans., and downstream Kansas River at De Soto, Kans., sites. Linear regression analysis was used to develop models that compute real-time concentrations or densities for total dissolved solids, major ions, hardness as calcium carbonate, nutrients (nitrogen and phosphorus species), chlorophyll
U.S. Geological Survey, 2022, USGS water data for the Nation: U.S. Geological Survey National Water Information System database,
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The author thanks the Kansas Water Office, the Kansas Department of Health and Environment, The Nature Conservancy, the City of Lawrence, the City of Manhattan, the City of Olathe, the City of Topeka, WaterOne, and Evergy for a beneficial and lasting partnership in monitoring water-quality conditions in the Kansas River.
The author thanks U.S. Geological Survey technical reviewers Teresa Rasmussen (Lawrence, Kansas), Kyle Juracek (Lawrence, Kans.), Mandy Stone (Lawrence, Kans.), and Tim Hoffman (Troy, New York) for reviewing previous drafts of this report. The author also thanks U.S. Geological Survey geographer Diana Restrepo-Osorio for assistance in adjusting the study area map to fit the needs of this report. Lastly, this report would not have been possible without the hard work by past and present U.S. Geological Survey staff at the Kansas Water Science Center who assisted with data collection, analyses, and project and database management.
Multiply | By | To obtain |
Length | ||
---|---|---|
foot (ft) | 0.3048 | meter (m) |
mile (mi) | 1.609 | kilometer (km) |
Area | ||
square mile (mi2) | 259.0 | hectare (ha) |
square mile (mi2) | 2.590 | square kilometer (km2) |
Multiply | By | To obtain |
Volume | ||
---|---|---|
milliliter (mL) | 0.0338 | ounce, fluid (fl. oz) |
Temperature in degrees Celsius (°C) may be converted to degrees Fahrenheit (°F) as follows:
°F = (1.8 × °C) + 32.
Horizontal coordinate information is referenced to the North American Datum of 1983 (NAD 83).
Specific conductance is given in microsiemens per centimeter at 25 degrees Celsius (µS/cm at 25 °C).
Concentrations of chemical constituents in water are given in either milligrams per liter (mg/L) or micrograms per liter (µg/L).
Densities of
logarithm with base 10
minimum reporting limit
prediction error sum of squares
quality control
coefficient of determination
root mean square error
relative percentage difference
total Kjeldahl nitrogen
U.S. Geological Survey
Water suppliers use the Kansas River and its associated alluvial aquifer to supply drinking water to more than 950,000 people throughout northeastern Kansas (Josh Olson, Kansas Water Office, written commun., July 21, 2022). Other uses of the Kansas River include cultural and recreational, industrial, food procurement, aquatic-life support, groundwater recharge, irrigation, and livestock water use (
Concomitant continuous in situ water-quality monitoring and discrete water-quality sampling in the Kansas River began during July 1999 primarily to characterize water-quality conditions by developing regression models using a combination of continuous water-quality monitor data and discrete water-quality samples to compute continuous concentrations or densities of water-quality constituents that are not easily measured in real time (
Kansas River water-quality sampling resumed after upstream releases from Milford Lake (a reservoir that contributes streamflow to the Kansas River) during a toxic cyanobacterial event in August 2011 to primarily characterize transport of cyanobacteria, cyanotoxins, and associated taste-and-odor compounds from upstream reservoirs to the Kansas River (
The USGS, in cooperation with the Kansas Water Office (funded in part through the Kansas Water Plan), the Kansas Department of Health and Environment, The Nature Conservancy, the City of Lawrence, the City of Manhattan, the City of Olathe, the City of Topeka, WaterOne, and Evergy, established a new continuous and discrete water-quality monitoring site at the Kansas River above Topeka Weir at Topeka, Kans. (USGS site 06888990; hereafter referred to as the “Topeka site”), in November 2018 to expand the Kansas River water-quality monitoring network by adding an intermediate location between the Wamego (upstream) and De Soto (downstream) monitoring sites. The continuous and discrete water-quality data collected at the Topeka site during November 2018 through June 2021 were used to develop new linear regression models and expand the early-notification system of changing water-quality conditions that may affect water treatment. Real-time computations of water-quality constituent concentrations or densities using the models documented in this report are available at the USGS National Real-Time Water-Quality website (
The purpose of this report is to describe linear regression models that were developed to continuously compute water-quality constituent concentrations or densities at the Topeka site. Models were developed for total dissolved solids, major ions, hardness as calcium carbonate, nutrients (nitrogen and phosphorus species), chlorophyll
The Kansas River Basin covers 60,097 square miles (mi2) of northern Kansas and parts of Nebraska and Colorado (
Location of the Kansas River at Wamego, Kansas; Kansas River above Topeka Weir at Topeka, Kans.; and Kansas River at De Soto, Kans., streamgages and discrete water-quality sampling sites in the lower Kansas River Basin (U.S. Geological Survey stations 06887500, 06888990, and 06892350, respectively).
Figure 1. Map showing location of the Kansas River at Wamego, Kansas; Kansas River above Topeka Weir at Topeka, Kans.; and Kansas River at De Soto, Kans., streamgages and discrete water-quality sampling sites in the lower Kansas River Basin.
Linear regression models that continuously compute water-quality constituent concentrations or densities were developed for the Topeka site, which is intermediately between the Wamego (rural, upstream) and De Soto (urban, downstream) monitoring sites (
The USGS collected continuous and discrete water-quality data at the Topeka site over the range of observed streamflows during November 2018 through June 2021 (
Streamflow duration curve and discrete water-quality samples at the Kansas River above Topeka Weir at Topeka, Kansas, streamgage (U.S. Geological Survey station 06888990) during November 2018 through June 2021. Data from U.S. Geological Survey, 2022.
Figure 2. Graph showing streamflow duration curve and discrete water-quality samples at the Kansas River above Topeka Weir at Topeka, Kansas, streamgage during November 2018 through June 2021.
The USGS began collecting continuous (15-minute interval) streamflow data at the Topeka site during November 2015 (
The USGS began collecting continuous (15-minute interval) water-quality data at the Topeka site in November 2018. During November 2018 through June 2021, a YSI EXO2 water-quality monitor (
Continuous water-quality monitor deployment at the Kansas River above Topeka Weir at Topeka, Kansas, streamgage (U.S. Geological Survey station 06888990) during November 2018 through June 2021. Photograph by Joey Filby, City of Topeka.
Figure 3. Photograph showing continuous water-quality monitor deployment at the Kansas River above Topeka Weir at Topeka, Kansas, streamgage during November 2018 through June 2021.
Water-quality samples were collected at the Topeka site on a biweekly to monthly basis during November 2018 through June 2020, on a monthly to bimonthly basis during July 2020 through June 2021, and during selected reservoir release and runoff events. Using this fixed-schedule sampling approach, water-quality samples were collected over the range of study period streamflows (
Total dissolved solids, major ions, hardness as calcium carbonate, nutrients (nitrogen and phosphorus species), and total suspended solids were analyzed by the USGS National Water Quality Laboratory in Lakewood, Colorado, using the methods documented by
Phytoplankton community composition and abundance, microcystin (a cyanotoxin), and geosmin and 2-methylisoborneol (taste-and-odor compounds) samples also were collected during each water-quality sampling. However, additional data collected during cyanobacteria, microcystin, and taste-and-odor events are necessary to obtain representative model-calibration datasets for model development at the Topeka site. Water-quality sampling and analytical methodology for these constituents are described in greater detail by
All continuous and discrete water-quality data collected during November 2018 through June 2021 were reviewed and approved quarterly, following USGS guidance (
Quality-control (QC) samples were collected for about 10 percent of all discrete water-quality samples. Concurrent replicate QC samples were collected to characterize variability in sample results that could potentially be introduced by sample-collection methods, sample processing techniques, and analytical method (
Three field blank samples were collected from the Topeka site during November 2018 through June 2021 to characterize bias caused by sampling procedures and analytical methods (
Concomitant field and in situ water-quality monitor (YSI EXO2) physiochemical properties were measured during discrete sampling events to compare sample-collection methods (depth- and width-integrated [collection method used during November 18, 2018, through February 5, 2019] and depth-integrated [collection method used during February 19, 2019, through June 2021]). Cross-sectional profile water-quality physiochemical properties were measured about 1 foot below the water surface alongside the depth- and width-integrated discretely collected samples; these samples coincided with the 84th, 81st, and 52d percentiles of daily mean study period streamflows. Two sets of vertical-profile cross-sectional water-quality physiochemical properties were measured at several depths at each cross-section location; these two vertical-profile cross-sectional measurements coincided with the 19th and 69th percentiles of daily mean study period streamflows. The Topeka site’s stream conditions were arbitrarily considered to be well mixed if field-measured profile and in situ measurement statistics (water temperature, specific conductance, and dissolved oxygen means and pH medians) were within 5 percent. RPDs among concomitant cross-sectional and in situ continuous water-quality monitor statistics were calculated to determine if the initial depth- and width-integrated samples were comparable to the depth-integrated samples collected at the in situ continuous water-quality monitor location. RPDs among concomitant cross-sectional profile and in situ continuous water-quality monitor measurement statistics were less than 4 percent. RPDs among concomitant vertical-profile cross-sectional and in situ continuous water-quality monitor statistics were equal to or less than 3 percent. This information indicated that the Kansas River at the Topeka site likely was generally well mixed; therefore, all water-quality samples, regardless of sample-collection technique, were considered during model development.
Models that related continuous in situ water-quality sensor measurements, streamflow, and seasonal components to discrete sample water-quality constituent concentrations or densities using linear regression analysis and data collected during November 2018 through June 2021 were developed. All regression models were developed using R programming language, version 4.2.0 (
Table 1. Linear regression models and summary statistics for computations of continuous water-quality constituent concentrations or densities for the Kansas River above Topeka Weir at Topeka, Kansas, streamgage using data collected during November 2018 through June 2021.
[
Regression model | Regression estimation method | Model archival summary | Adjusted |
aPseudo- |
Estimated |
Mean |
Bias correction factor ( |
Discrete data used in model development dataset | ||||||
Percentage of censored data | Range of values in variable measurements | Mean | Median | |||||||||||
Total dissolved solids (TDS), mg/L | ||||||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
App. 1 | 0.974 | -- | 1,000 | 31.7 | 31.7 | 6.16 | -- | 34 | 0 | TDS: 202–839 | 514 | 502 | ||
SC: 188–1,420 | 814 | 778 | ||||||||||||
Calcium (Ca), dissolved, mg/L | ||||||||||||||
log( |
App. 2 | 0.938 | -- | 0.00159 | 0.0399 | 0.0399 | 9.21 | 1.00 | 34 | 0 | Ca: 31.7–120 | 81.7 | 85.3 | |
SC: 188–1,420 | 814 | 778 | ||||||||||||
Magnesium (Mg), dissolved, mg/L | ||||||||||||||
log( |
App. 3 | 0.954 | -- | 0.00169 | 0.0411 | 0.0411 | 9.48 | 1.00 | 34 | 0 | Mg: 4.96–27.7 | 17.6 | 19.0 | |
SC: 188–1,420 | 814 | 778 | ||||||||||||
Sodium (Na), dissolved, mg/L | ||||||||||||||
log( |
App. 4 | 0.981 | -- | 0.00229 | 0.0479 | 0.0479 | 11.1 | 1.01 | 34 | 0 | Na: 3.75–158 | 62.3 | 52.9 | |
SC: 188–1,420 | 814 | 778 | ||||||||||||
Sulfate (SO4), dissolved, mg/L | ||||||||||||||
log( |
App. 5 | 0.932 | -- | 0.00613 | 0.0783 | 0.0783 | 18.1 | 1.01 | 34 | 0 | SO4: 9.22–196 | 116 | 126 | |
SC: 188–1,420 | 814 | 778 | ||||||||||||
Chloride (Cl), dissolved, mg/L | ||||||||||||||
log( |
App. 6 | 0.967 | -- | 0.00498 | 0.0706 | 0.0706 | 16.3 | 1.01 | 34 | 0 | Cl: 3.01–228 | 79.0 | 62.8 | |
SC: 188–1,420 | 814 | 778 | ||||||||||||
Hardness (CaCO3), mg/L | ||||||||||||||
log( |
App. 7 | 0.947 | -- | 0.00145 | 0.0381 | 0.0381 | 8.78 | 1.00 | 34 | 0 | CaCO3: 99.8–412 | 276 | 289 | |
SC: 188–1,420 | 814 | 778 | ||||||||||||
Total nitrogen (TN), total particulate nitrogen plus dissolved nitrogen, mg/L | ||||||||||||||
log( |
App. 8 | 0.743 | -- | 0.0182 | 0.135 | 0.135 | 31.7 | 1.05 | 34 | 0 | TN: 0.788–8.03 | 2.62 | 1.94 | |
TBY: 8.23–1,240 | 230 | 60.6 | ||||||||||||
Total Kjeldahl nitrogen (TKN), mg/L; total ammonia plus organic nitrogen, mg/L | ||||||||||||||
log( |
App. 9 | 0.922 | -- | 0.00837 | 0.0915 | 0.0915 | 21.2 | 1.02 | 34 | 0 | TKN: 0.440–5.80 | 1.65 | 0.875 | |
TBY: 8.23–1,240 | 230 | 60.6 | ||||||||||||
Total phosphorus (TP), mg/L | ||||||||||||||
log( |
App. 10 | 0.914 | -- | 0.0117 | 0.108 | 0.108 | 25.2 | 1.03 | 34 | 0 | TP: 0.140–2.45 | 0.668 | 0.390 | |
TBY: 8.23–1,240 | 230 | 60.6 | ||||||||||||
Chlorophyll |
||||||||||||||
log( |
App. 11 | 0.809 | -- | 0.0392 | 0.198 | 0.198 | 47.1 | 1.1 | 34 | 0 | Chla: 1.40–59.9 | 19.2 | 13.8 | |
fCHL: 0.697–7.96 | 2.78 | 1.75 | ||||||||||||
Total suspended solids, (TSS), mg/L | ||||||||||||||
log( |
App. 12 | -- | 0.943 | -- | -- | 0.165 | -- | 1.06 | 34 | 5.90 | TSS: <15.0–3,480 | 526 | 136 | |
TBY: 8.23–1,240 | 230 | 60.6 | ||||||||||||
Suspended-sediment concentration (SSC), mg/L | ||||||||||||||
log( |
App. 13 | 0.989 | -- | 0.0051 | 0.0712 | 0.0712 | 16.5 | 1.01 | 33 | 0 | SSC: 18–3,710 | 735 | 161 | |
TBY: 8.23–1,240 | 236 | 61.0 | ||||||||||||
log( |
App. 14 | 0.791 | -- | 0.289 | 0.538 | 0.538 | 158 | 1.85 | 34 | 0 | ECB: 6.00–41,000 | 4,510 | 64.0 | |
TBY: 8.23–1,240 | 230 | 60.6 |
Pseudo-
Chlorophyll
Potential explanatory variables that were considered during linear regression model development were continuous streamflow, water temperature, specific conductance, dissolved oxygen, turbidity, chlorophyll and phycocyanin fluorescence, and seasonal components (sine and cosine variables). Potential explanatory variables were evaluated individually and in combination and were interpolated by discrete water-quality sample time within the 15-minute continuous record. Explanatory variable data were not interpolated by sample time if the sample time coincided with a gap in the continuous record (because of excessive fouling, equipment malfunction, or equipment removal) that exceeded 2 hours (
Preliminary linear regression models were evaluated based on range and distribution of continuous and discrete model-calibration data, patterns in residual plots, and the following model diagnostic statistics: adjusted coefficient of determination (
Logarithmic transformations (logarithm with base 10 [log] transformations) of the response and explanatory variables were used during model development if heteroscedasticity was apparent in plots of response variable residuals compared to model computed values (shown in appendixes 1–14). If log transformations were used in the final selected model, a bias correction factor was computed and used for the retransformation of log-transformed computations back into their original units (
Multiple explanatory variables for a given linear regression model were considered if the additional variable increased the variance (as indicated by adjusted
Potential outliers initially were identified by viewing bivariate plots of the model-calibration data for each set of response and explanatory variables (
Linear regression models that compute continuous water-quality constituent concentrations or densities of total dissolved solids, calcium, magnesium, sodium, sulfate, chloride, hardness as calcium carbonate, total nitrogen (particulate plus dissolved nitrogen), TKN, total phosphorus, chlorophyll
Specific conductance was the single explanatory variable used to model for total dissolved solids, calcium, magnesium, sodium, sulfate, chloride, and hardness as calcium carbonate at the Topeka site (
Turbidity was the single explanatory variable used to model for total nitrogen, TKN, and total phosphorus at the Topeka site (
Chlorophyll fluorescence was the single explanatory variable used to model for chlorophyll
Turbidity was the single explanatory variable used to model for total suspended solids and suspended sediment at the Topeka site (
Turbidity was the single explanatory variable used to model for
Water suppliers rely on the Kansas River and its alluvial aquifer to supply drinking water to more than 950,000 people throughout northeastern Kansas. They use numerous physiochemical processes to treat and remove contaminants from source water before public distribution. An early-notification system of changing water-quality conditions near water-supply intakes allows water suppliers to proactively make decisions that affect water treatment. The U.S. Geological Survey (USGS), in cooperation with the Kansas Water Office (funded in part through the Kansas Water Plan), the Kansas Department of Health and Environment, The Nature Conservancy, the City of Lawrence, the City of Manhattan, the City of Olathe, the City of Topeka, WaterOne, and Evergy, established a new continuous and discrete water-quality monitoring site at the Kansas River above Topeka Weir at Topeka, Kansas (USGS site 06888990; hereafter referred to as the “Topeka site”), in November 2018 to expand the Kansas River water-quality monitoring network by adding an intermediate location between the existing monitoring sites at Wamego (upstream) and De Soto (downstream), Kans. The continuous and discrete water-quality data were collected by the USGS at the Topeka site over the range of observed streamflow conditions during November 2018 through June 2021 and were used to develop new linear regression models and expand the early-notification system of changing water-quality conditions that may affect water treatment. Continuous water-quality data collected at the site were water temperature, specific conductance, pH, dissolved oxygen, turbidity, and chlorophyll and phycocyanin fluorescence. All discrete water-quality samples were analyzed for total dissolved solids, major ions, hardness as calcium carbonate, nutrients (nitrogen and phosphorus species), chlorophyll
The models documented in this report provide real-time computations of water-quality constituent concentrations or densities that are not easily measured in real time. Model computations are useful to the public for cultural and recreational purposes and can be used to characterize water-quality conditions that may affect drinking-water treatment at the Topeka site, compare to previously published model-computed concentrations or densities at the Wamego and De Soto sites, compare conditions with Federal and State water-quality criteria, and evaluate changes in water-quality conditions in the Kansas River through time.
The model archival summaries for this report, provided in appendixes 1–14, are available for download at
Appendix 1. Model Archival Summary for Total Dissolved Solids Concentration at U.S. Geological Survey Site 06888990, Kansas River above Topeka Weir at Topeka, Kansas, during November 2018 through June 2021
Appendix 2. Model Archival Summary for Calcium Concentration at U.S. Geological Survey Site 06888990, Kansas River above Topeka Weir at Topeka, Kansas, during November 2018 through June 2021
Appendix 3. Model Archival Summary for Magnesium Concentration at U.S. Geological Survey Site 06888990, Kansas River above Topeka Weir at Topeka, Kansas, during November 2018 through June 2021
Appendix 4. Model Archival Summary for Sodium Concentration at U.S. Geological Survey Site 06888990, Kansas River above Topeka Weir at Topeka, Kansas, during November 2018 through June 2021
Appendix 5. Model Archival Summary for Sulfate Concentration at U.S. Geological Survey Site 06888990, Kansas River above Topeka Weir at Topeka, Kansas, during November 2018 through June 2021
Appendix 6. Model Archival Summary for Chloride Concentration at U.S. Geological Survey Site 06888990, Kansas River above Topeka Weir at Topeka, Kansas, during November 2018 through June 2021
Appendix 7. Model Archival Summary for Hardness Concentration at U.S. Geological Survey Site 06888990, Kansas River above Topeka Weir at Topeka, Kansas, during November 2018 through June 2021
Appendix 8. Model Archival Summary for Total Nitrogen Concentration at U.S. Geological Survey Site 06888990, Kansas River above Topeka Weir at Topeka, Kansas, during November 2018 through June 2021
Appendix 9. Model Archival Summary for Total Kjeldahl Nitrogen Concentration at U.S. Geological Survey Site 06888990, Kansas River above Topeka Weir at Topeka, Kansas, during November 2018 through June 2021
Appendix 10. Model Archival Summary for Total Phosphorus Concentration at U.S. Geological Survey Site 06888990, Kansas River above Topeka Weir at Topeka, Kansas, during November 2018 through June 2021
Appendix 11. Model Archival Summary for Chlorophyll
Appendix 12. Model Archival Summary for Total Suspended Solids Concentration at U.S. Geological Survey Site 06888990, Kansas River above Topeka Weir at Topeka, Kansas, during November 2018 through June 2021
Appendix 13. Model Archival Summary for Suspended-Sediment Concentration at U.S. Geological Survey Site 06888990, Kansas River above Topeka Weir at Topeka, Kansas, during December 2018 through June 2021
Appendix 14. Model Archival Summary for
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