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N

 U.S. Department of the Interior

 U.S. Geological Survey 

 Fact Sheet 2004–3011

 March 2004 Printed on recycled paper

 Monitoring Surface-Water Quality in the Tongue River Watershed 

 While past and ongoing efforts have added substantially to our knowledge, sufficient data are not available 

for full understanding of water resources and water quality in the Tongue River watershed. 

 Coal-bed methane (CBM) development is in the initial stages of exploration and production in the Tongue River 

watershed of southeastern Montana and 

northeastern Wyoming (fig. 1). In recent 

years, many State, Federal, and Tribal 

agencies and other entities have worked 

together to share information, communicate concerns, and coordinate datacollection activities for areas of potential CBM development. While past and 

ongoing efforts have added substantially 

to our scientific understanding, sufficient 

monitoring data are not available for full 

documentation of water resources and 

water quality in the watershed. As CBM 

development proceeds over the next 10 

to 20 years, long-term monitoring will be 

needed to provide information to evaluate 

any changes or trends in surface-water

quality and support informed decisions 

about resource management. For fiscal year 2004, Congress appropriated 

funding for the U.S. Geological Survey 

to initiate a comprehensive surfacewater-quality monitoring program in the 

Tongue River watershed. The goal of the 

program is to collect and disseminate 

water-quality data to stakeholders and 

the general public as well as to State and 

Federal agencies tasked with managing 

and regulating CBM development.

 Figure 1. Water-quality sampling sites in the Tongue River watershed. All sites will have 

continuous streamflow gages and specific-conductance monitors. 

 Monitoring for the future

 The objectives of this monitoring 

program are to:

 • collect data to document the current 

surface-water quality of the Tongue 

River and its major tributaries and 

detect changes, if any, over time, 

and 

 • provide real-time surface-waterquality information for parameters 

of greatest concern—particularly 

specific conductance and sodium 

adsorption ratio (SAR).

 Approach

 Establish monitoring network. A 

monitoring network consisting of eleven 

stations will be established during 2004 

(fig. 1). Six mainstem monitoring stations 

will be on the Tongue River to identify 

downstream changes in water quality. 

Five stations will be on major tributaries 

to the Tongue River to document water 

quality in these smaller watersheds. Continuous streamflow and specificconductance data will be collected at 

each station.

 Collect water-quality data. The 

mainstem Tongue River stations will be 

sampled approximately twice-monthly 

during the irrigation season (MarchOctober) and once-monthly for the rest 

of the year. The tributary stations will be 

sampled approximately 12 times per year, 

with more frequent sampling during the 

irrigation season. Water samples will be 

analyzed for major ions, nutrients, trace 

elements, and suspended sediment. Constituents of primary concern for analysis 

are those typically contained in CBM 

product water at relatively high concentrations. Examples of these constituents 

include sodium (a major ion), ammonia 

(a nutrient), and nitrate (another nutrient 

that forms when ammonia is exposed to 

oxygen). Trace elements, such as arsenic, 
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 Tongue River at State Line, Montana (site 2, fig. 1). 

 Figure 2. The sodium adsorption ratio (SAR) commonly can be estimated from 

specific conductance (SC). This figure provides an example of how this estimation could be accomplished. The estimation process starts with SC and SAR data 

for water samples collected at a site. For example, the upper graph shows the 

relation between SC and SAR for water samples collected during 1999-2002 at 

Tongue River at State Line (site 2, fig. 1). In the middle graph, continuous SC data 

collected at this site are shown for April-September 2002. The relation between 

SC and SAR determined in the upper graph can be applied to the continuous SC 

data (middle graph) to produce the continuous estimated SAR values shown in 

the lower graph.

 To demonstrate the reliability of the estimation process, SAR values for individual water samples also are shown (solid circles) in the lower graph. Data for 

samples collected during April-June plot close to the estimated SAR line indicating that SAR might be reliably estimated from SC at this site during this period. 

However, the SAR values for the water samples collected in July-September 

are higher than the estimated values by as much as 30 percent. This difference 

between the calculated and estimated SAR values indicates that the relation 

developed in the upper graph is not as good at estimating SAR at this site for the 

summer as for the spring. Further research might lead to improvements in the 

ability to predict SAR from SC. 

iron, manganese, and nickel, are of lesser concern 

because their concentrations generally are relatively 

low (Rice and Nuccio, 2000).

 Develop real-time SAR estimates and measurement techniques. Providing real-time SAR information will be addressed in two ways. First, statistical 

relations between specific conductance and SAR will 

be examined for each station (fig. 2). If these relations 

are statistically meaningful, real-time estimates of 

SAR will be generated from continuous specificconductance data for each station. Second, recent 

technological advances have made possible the 

development of experimental instrumentation that can 

be placed in the field and provide automated measurements of the constituents (calcium, magnesium, 

and sodium) which are used to calculate SAR. One 

analyzer will be built, deployed, and tested during 

2004. If that is successful, a second instrument will 

be deployed in 2005.

 Provide information to the public. All data 

collected at each station in the network will be made 

available on a dedicated web site developed just for 

this network:

(http://TongueRiverMonitoring.cr.usgs.gov/).

Streamflow and specific-conductance data will be 

provided in real time from satellite transmissions. 

Estimates of SAR at stations with sufficient data and 

reliable statistical relations also will be provided on 

the dedicated web site. Should the experimental SAR 

instrumentation prove successful, then SAR values 

calculated from direct field measurements of calcium, 

magnesium, and sodium will also be provided.

 Reference Cited

 Rice, C.A., and Nuccio, Vito, 2000, Water produced with 

coal-bed methane: U.S. Geological Survey Fact Sheet 

FS-156-00, 2 p.

 By David A. Nimick

 For more information,

contact:

 District Chief

U.S. Geological Survey

3162 Bozeman Avenue

Helena, MT 59601

406-457-5900

or

1-888-ASK-USGS

 Please visit the USGS on the Internet:

 The USGS Montana District homepage is:

http://mt.water.usgs.gov/

 The USGS Tongue River monitoring program homepage is: http://TongueRiverMonitoring.cr.usgs.gov/

 The National USGS homepage is:

http://www.usgs.gov/

 Sodium adsorption ratio (SAR) is a measure of 

the suitability of irrigation water for sustained 

soil and crop health. Water with a higher ratio is 

less suitable for irrigation. SAR values greater 

than 5-10 can indicate medium to high sodium 

hazard.