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Flathead Lake Watershed Nutrient TMDLs

Page history last edited by Christina Staten 1 year ago Saved with comment

Flathead TMDL Project Overview

 Draft Document     Contacts     Project Outreach     Sediment & Temperature TMDLs


Page Contents:



Effects of Excess Nutrients on Streams & Lakes

Nutrients (nitrogen and phosphorus forms) are naturally occurring compounds that contribute to primary production and are necessary for biological productivity in streams. In excessive amounts however, nitrogen and phosphorus can impair a stream or lake by contributing to undesirable algal growth which may create aesthetically unpleasing conditions and also harm aquatic life. For example, if an algal bloom occurs, it will reduce the amount of dissolved oxygen in the water causing stress for fish and possibly killing them.



Nutrient TMDLs for Streams in the Flathead Lake Watershed 

Map 1:  Nutrient TMDLs Completed in the Flathead Lake Watershed in 2014

(Click on map to enlarge)

Nutrient TMDLs to be completed in 2014TMDLs Completed in 2014

(contained in the Flathead-Stillwater TMDL document)

After updated nutrient water quality assessments were performed in 2014 using recently collected data (additional details below), Ashley and Spring creeks were the only remaining waterbodies in the Flathead Lake watershed requiring nutrient TMDLs. Table 1 below provides a list of the nutrient TMDLs for Ashley Creek and Spring Creek that were completed in 2014. Map 1 shows the location of the two tributaries. 


Table 1: Nutrient TMDLs Completed in 2014

Waterbody & Location Description

(Click Waterbody Name to View Map)



Ashley Creek

Ashley Lake to Smith Lake

Total Nitrogen

Ashley Creek

Smith Lake to Kalispell Airport Road

Total Nitrogen,

Total Phosphorus

Ashley Creek

Kalispell Airport Road to mouth (Flathead River)

Total Nitrogen,

Total Phosphorus

Spring Creek

Headwaters to mouth (Ashley Creek)

Total Nitrogen,

Total Phosphorus


Flathead-Stillwater TMDL Document & Project History

The nutrient TMDLs for these two streams are contained in the "Flathead-Stillwater Planning Area Nutrient, Sediment, and Temperature TMDLs and Water Quality Improvement Plan" that was approved by the U.S. EPA in Denver on December 17, 2014. The document is available on DEQ's webpage under "TMDL Documents," and can also be found at the Big Fork, Columbia Falls, Kalispell, Missoula, Polson, and Whitefish public libraries. 


Supporting documents for the nutrient TMDLs are posted on the Flathead Draft TMDL Document page. The Flathead TMDL Project Outreach page contains the project status updates that were given and the announcements of advisory group meetings that were held during the development of these TMDLs, as well as those meeting presentations and handouts. 


Flathead Lake Nutrient TMDLs

(contained in the 2001 Flathead Lake TMDL document)

Total Nitrogen and total phosphorus TMDLs were written for Flathead Lake in 2001, and can be found in the "Nutrient Management Plan & Total Maximum Daily Load for Flathead Lake, Montana" document (found under "Flathead Lake" in the alphabetical list of TMDL documents). Refinement of the allocations for these TMDLs is considered "Phase II," which has not been completed. DEQ and EPA were under a court order to complete the TMDLs identified in Table 1 above before the end of calendar year 2014, as per an amended judgment to a TMDL lawsuit. Completing Phase II of the Flathead Lake nutrient TMDLs was not a requirement of the court order. To focus staff resources on those TMDLs that had to be completed by the end of 2014, DEQ and EPA decided to postpone completion of the nutrient TMDLs for Flathead Lake until after 2014.  


Flathead Lake Nutrient Standards Development

DEQ is currently in the process of developing numeric nutrient criteria for Flathead Lake. Additional information about this project is located on the Flathead Lake Nutrient Standards Development page. Contact Dr. Michael Suplee with questions pertaining to nutrient standards for the lake (MSuplee@mt.gov, 406-444-0831). 



Water Quality Sampling Data & 2014 Nutrient Impairment Determinations


Updated Impairment Determinations for Streams in the Flathead Lake Watershed

In 2011, DEQ developed a new water quality assessment method for determining nutrient impairment in wadeable streams. In 2012, DEQ and EPA conducted nutrient water quality sampling on eight streams and rivers in the Flathead Lake watershed. The sampling and analysis plans and collected data can be found in Table 3 below. Following the new assessment method, DEQ conducted water quality assessments to determine nutrient impairment for the sampled streams, using the recently collected data along with historical data collected by DEQ and other entities. Table 2 below details previously identified nutrient impairments that were removed from Montana’s list of impaired waters, and nutrient impairments that were added. Click on the waterbody names in the table to view water quality summaries and to link to the full water quality assessment records and location maps. The full 2014 Water Quality Integrated Report containing the list of impaired waters can be viewed on our Clean Water Act Information Center.


Table 2: Results of Nutrient Water Quality Assessments for Waterbodies in the Flathead Lake Watershed


Planning Area1

Waterbody & Location Description

(Click Name to View Assessment Summary)

Nutrient Impairments

on the 2012 List of

Impaired Waters

Impairments on the 2014

List of Impaired Waters

(Updated Assessment Results)

Flathead Headwaters

Challenge Creek

Headwaters to mouth (Granite Creek)

Total Phosphorus


Flathead - Stillwater

Ashley Creek

Ashley Lake to Smith Lake

Total Nitrogen

Total Phosphorus

Total Nitrogen

Ashley Creek

Smith Lake to Kalispell Airport Road


Total Nitrogen

Total Phosphorus

Ashley Creek

Kalispell Airport Road to mouth (Flathead River)

Total Nitrogen

Total Phosphorus

Nitrate/Nitrite as N

Total Nitrogen

Total Phosphorus

Nitrate/Nitrite as N

Fish Creek

Headwaters to mouth (Ashley Lake)

Total Phosphorus


Haskill Creek

Headwaters to Haskill Basin Pond

None 2



Haskill Creek

Haskill Basin Pond to mouth (Whitefish River)

None 2



Sheppard Creek

Headwaters to mouth (Griffin Creek)

Total Phosphorus

Nitrate/Nitrite as N


Spring Creek

Headwaters to mouth (Ashley Creek)

Total Nitrogen

Total Phosphorus

Nitrate/Nitrite as N

Total Nitrogen

Total Phosphorus

Nitrate/Nitrite as N

Stillwater River

Logan Creek to mouth

Total Phosphorus



Whitefish River

Whitefish Lake to mouth (Stillwater River)

Total Nitrogen


1. A map and description of each planning area can be found on the Project Overview page.

2. Haskill Creek had not previously been assessed and therefore was not included on the 2012 list of impaired waters. Data was collected on Haskill during this project and the lower segment was determined not to be impaired for a nutrient. Additional data is needed to complete a nutrient assessment on the upper segment.


Nutrient Water Quality Data

Water quality samples for nutrients were collected in 2012 and 2013 and were used in the updated water quality assessments performed for the streams in Table 2, as discussed above. Table 3 below contains this data and the associated sampling plans that define the parameters collected, methods used, and sampling locations. Table 4 below contains the numeric nutrient water quality standards applicable to the streams in the Flathead Lake watershed. 


Ashley Creek Sampling

Additional sampling on Ashley Creek occurred in 2015, and further sampling is being planned for 2016, to better understand the sources of nutrients in the area around and upstream of Smith Lake. This data will be used to help refine estimates of Ashley Creek's nutrient load contribution to Flathead Lake within the LSPC watershed model that was developed as part of the TMDL project (see the "Flathead Lake Watershed Model" section below). The Ashley Creek sampling plans and a summary report of the 2015 sampling are contained in Table 3 below. 


Table 3: Water Quality Data & Sampling Plan Documents 


Document Description


Flathead-Stillwater TMDL Planning Area Sampling Project – 2012: Nutrients, Metals Sampling and Analysis Plan (SAP) (0.21 MB)

Metals and nutrients monitoring was conducted in 2012 to support TMDL development and water quality impairment determinations. This SAP aimed to meet requirements for the completion of source assessments and loading estimates for nutrients and metals listed streams in the planning area, and to have enough data to assess the streams based on DEQ's water quality assessment method for determining nutrient impairment in wadeable streams (2011 method), and DEQ's metals assessment method (2012 method). Note: updated assessment methods can be viewed on DEQ's website.


Monitoring locations, field methods, and data quality assurance requirements are included in the document. Note that some monitoring locations listed in the SAP changed due to difficulties obtaining land access.

May 2012

Final Version

Flathead - Stillwater TMDL Planning Area 2013 Nutrients Sampling & Analysis Plan (0.1 MB)

Additional nutrient sampling occurred on Fish & Sheppard creeks in July and August of 2013 in order to obtain enough samples to perform nutrient assessments. Samples were also collected at the Creston Fish Hatchery outfall.


Please note that the SAP also includes sampling locations for a separate TMDL project.

June 2013


2012 Metals & Nutrient Data:

Spreadsheet (1.19 MB)

PDF (0.4 MB)

The metals and nutrients data collected in 2012 according to the above sampling & analysis plan is available for review. The spreadsheet contains the data in both a condensed format, as well as with all the data attributes. The PDF only contains the condensed version.


Numeric nutrient water quality criteria are posted in Table 4 below.

Circular DEQ-7 (June 2019 version) contains Montana's numeric water quality standards for metals.

2012 Data

2013 Nutrient Data:

MS Excel Spreadsheet (66 kb)

PDF File (79 kb)

The nutrient data collected on Fish and Sheppard Creeks and at the Creston Fish Hatchery in July and August of 2013 is available for download. 2013 Data

Pre-2012 Metals & Nutrients Data:


All water quality sampling data collected by DEQ and EPA are housed in EPA's STORET database. You can download the data at the link to the left. Click on "Download Data" and choose "Option D" under Geographic Location to download the data by HUC (hydrologic unit code). You may limit the date range of your data under "Date" further down the page if desired, then scroll to the bottom of the page and click "Result Download" under Submit Query. The data will be returned to you as a text file that you will need to import into MS Excel or MS Access to view.


The applicable HUC codes are:

17010206 North Fork Flathead

17010207 Middle Fork Flathead

17010208 Flathead Lake

17010209 South Fork Flathead

17010210 Stillwater

(Note: the lower portion of the Stillwater River is contained in HUC 17010208)

17010211 Swan

17010212 Lower Flathead

If you are unsure what HUC your stream of interest falls within, search for the stream on DEQ's website (http://cwaic.mt.gov).

Info Posted Feb 2013
Ashley Creek Nutrient and Flow Sampling & Analysis Plan for 2015 and 2016 (0.9 MB)

Nutrient sampling was conducted in 2015 at multiple locations in the upper and middle portions of Ashley Creek  to gain further insight into the Smith Lake "wetland complex" source, and to further refine the estimate of nutrient loading from Ashley Creek to Flathead Lake within the LSPC model developed for the Flathead Lake watershed. Flows at the outlet of Ashley Lake were measured and staff gage readings recorded to begin development a stage-discharge relationship for flow out of Ashley Lake. Additional sampling is taking place in 2016. 

January 2016


Ashley Creek Nutrient & Flow Sampling Report for 2015 (1.4 MB) Summary report of the nutrient and flow data collected on Ashley, Idaho, and Truman creeks, and discharge data collected at the outlet of Ashley Lake. 

February 2016


Draft Ashley Creek Instream Lake Core Sampling & Analysis Plan (~0.8 MB) If funding and DEQ staff resources become available, sediment cores may be collected from the lakes within Ashley Creek, downstream of Ashley Lake, for the purpose of examining changes in the diatom species composition over the last 100 or more years. This monitoring would also be conducted to refine the Ashley Creek portion of the Flathead Lake LSPC watershed model. 

May 2015



Table 4: Numeric Nutrient Standards & Other Documents


Document Description


Circular DEQ-12A, Montana Base Numeric Nutrient Standards


Circular DEQ-12B, Nutrient Standards Variances

Contains numeric nutrient water quality standards, including concentration limits, where they apply, and their period of application. Also contains information about variances from the base numeric nutrient standards, including effluent treatment requirements associated with the general nutrient standards variances, and effluent treatment requirements for individual nutrient standards variances, and to whom these apply.


Additional information on the development of Montana's numeric nutrient criteria can be found on DEQ's Numeric Nutrient Criteria webpage

July 2014


Flathead Regional Wastewater Management Group (FRWMG) report on sewage treatment in the Flathead Basin can be found on the FRWMG website (the report is 9.32 MB). 

This report analyzes the conveyance and treatment capacities of existing major wastewater facilities in the basin, and compares to the existing and projected flows from these service areas to determine if sufficient excess capacity is available to serve additional areas outside of the current service areas. The report also identifies unsewered areas outside of the current established service areas that could be served by public wastewater systems. Estimates of general costs of collection system improvements into currently unsewered areas are also included in the report.




Flathead Lake Watershed Model & Nutrient Technical Reports


A water quality model has been developed for the entire Flathead Lake watershed, which provides a better understanding of the current amounts of nutrients entering the streams and lakes in the watershed. The model allows for potential land management scenarios to be simulated to determine how changing land use practices effect the amount of nutrients entering waterways. The results were used to evaluate the sources of nutrients to Ashley and Spring creeks and to aid the completion of the sediment TMDLs in the Flathead-Stillwater TMDL document. The draft model report is available in Table 5 below for stakeholder review and comment through January 31, 2015 (until 12 a.m. February 1). Technical reports related to the modeling effort can be found in Table 6 below.


Table 5: Draft Model Report



How To Submit Comments

Flathead Lake Watershed Modeling Report (5.91 MB)


Appendix A (3.06 MB)

Appendix B (~0.4 MB)

Appendix C (~0.7 MB)

Appendix D (7.19 MB)

Appendix E (6.33 MB)

Appendix F (3.28 MB)

Appendix G (2.15 MB)

Appendix H (9.63 MB)


Report containing calibration and scenario results for the LSPC model developed for the Flathead Lake watershed (note that Flathead Lake itself was not modeled)

The comment period closed on February 1, 2015


Contact Eric Regensburger with questions:


(406) 444-6714



Nutrient Technical Reports

A series of brief technical reports were prepared by EPA in support of setting up the water quality simulation model for the Flathead Lake watershed. When combined, these reports are intended to define a preliminary conceptual understanding of the current water quality conditions relative to nutrients, sources of nutrients, and the ways in which water and nutrients are transported in the watershed. The information presented in these reports was used to inform the modeling and TMDL processes. Specific details on model setup are included in the modeling quality assurance project plan (QAPP) posted at the bottom of the table. Note that the data and information presented in these reports reflects what was available at the time the reports were developed.


Table 6: Nutrient Technical Reports 

Zip File of All Nutrient Technical Reports (27.5 MB)

Contains all nutrient technical reports and their appendices posted as of 11-17-11. File size is large, but eliminates the need for downloading each report separately.


The only change from version 2 is the 2007-2008 monitoring report was replaced with a corrected version (see below). This zip file does Not contain the model QAPP.


Version 3





Urban Stormwater (4.1 MB)

Provides a summary of the extent and type of stormwater sources and systems in the Flathead Basin. The focus is on stormwater originating from urban point and nonpoint sources, and specifically on the regulated sources (i.e., MPDES permitted sources.




High Resolution (8.5 MB)

Compressed (1.4 MB)

Provides a summary of the extent and type of roads located in the Flathead Basin and their impacts to hydrology and water quality.



Groundwater Quality & Hydrology (1.36 MB)

Summarizes known groundwater characteristics within the Flathead Lake watershed, with a focus on how those characteristics affect surface water flows and water quality. The report also serves as an inventory of the available previous studies and data.

September, 2011


Point Source Discharges (3.39 MB)

Provides a summary of the extent and type of point sources located in the Flathead Basin, specifically focusing on MPDES permitted point sources, including individual, general, and groundwater discharge permits.

September, 2011


Agriculture / Irrigation (58.9 kb)

Appendices A and B (8.37 MB)

This report focuses on agricultural areas above, or north of, Flathead Lake, and summarizes approximations of: the types and locations of agricultural lands that exist in the Flathead Basin, the amount of irrigated land and irrigation practices in place, locations of known irrigation withdrawals and returns, types and magnitudes of applied fertilizer, and determinations of trends in agricultural practices in the basin. This report is intended to provide a snapshot of agricultural conditions during the summer of 2009.

April, 2011


Timber Harvest (819 kb)

Characterizes the extent and type of timber harvests located in the Flathead Basin and their effects on hydrology and water quality.

September, 2011


Forest Fires (812 kb)

Provides a summary of the extent of historic fires in the Flathead Basin and their impacts to hydrology and water quality.

July, 2011


Lakes & Reservoirs (3.82 MB)

Appendices A through F (1.94 MB)

Presents an inventory and analysis of available data for lakes and reservoirs in the Flathead Lake watershed. Specific objects of the report are to answer:

  • What lakes and reservoirs in the watershed are of concern for watershed-scale nutrient loading?
  • What data are available to characterize nutrients in each of these lakes and reservoirs?
  • Is there sufficient information to determine if these lakes and reservoirs are sinks or sources of nutrients to downstream waterbodies?
  • What are the most appropriate modeling approaches for the lakes and reservoirs in the watershed?

September, 2011


Results of 2007 and 2008 Nutrient Monitoring (1.32 MB)

Detailed monitoring efforts were completed by DEQ in the Flathead Lake watershed during 2007 and 2008 to characterize the spatial attributes of streamflow and water quality, seasonal and annual loading rates of nitrogen and phosphorus to the lake, and to support watershed model development for the TMDLs. Consequential changes brought about by upstream lakes and reservoirs were also evaluated.

Sampling was completed at over 20 sites including the North, Middle, and South forks of the Flathead River; the Swan River; Stillwater River; Whitefish River; and Ashley Creek. Data was also collected on Hungry Horse Reservoir, Swan Lake, and Whitefish Lake. Sample location descriptions and map are included in the report.

August, 2011



Note: It was discovered that an equation was missing on page 10 of the report and a corrected version was posted 11/17/11.

Summary of Available Nutrient Data (1.32 MB)

Appendices A through D (2.38 MB)

Provides a summary of available nutrient water quality data for each of the nutrient impaired streams in the Flathead Lake watershed. The purpose is to specifically answer:

  • Where have nutrient water quality data been collected in relation to the impaired segments?
  • What is the period of record for the nutrient water quality data in the impaired segments?
  • What is the magnitude of the nutrient concentrations observed in the impaired segments?
  • How do the nutrient water quality data in the impaired segments compare to the current and proposed nutrient standards?

The data presented in this report are current through 2007.

September, 2011


Flathead Lake Watershed LSPC Modeling Approach & Quality Assurance Project Plan 

(3.51 MB)

Describes the approach for developing and using a watershed model to help develop TMDLs for Flathead Lake and impaired waterbodies in the Flathead Lake watershed. This report also serves as the quality assurance project plan (QAPP) for the modeling process. The QAPP provides a general description of the data quality objectives and quality control procedures. 

September 4, 2012




Project Contacts






Christina Staten

Project Coordinator


(406) 444-2836

Dean Yashan

Contact for the sediment and temperature TMDLs


(406) 444-5317

Jason Gildea

Project Manager for Ashley Creek and Spring Creek nutrient TMDLs


(406) 457-5028

Eric Regensburger

Project Modeler

Eric is the DEQ contact for the Flathead Lake watershed model


(406) 444-6714

Michael Suplee Contact for Flathead Lake nutrient water quality standards MSuplee@mt.gov (406) 444-0831


For a complete list of contacts, see the Flathead TMDL Project Contacts page.


If you need to download the free Adobe Acrobat software to view the PDF documents on this page, click on the Adobe Reader icon below.


Page Released: October 13, 2011 

Last Updated: broken web links repaired on October 21, 2019 (page content was last updated in 2016)