Monitoring Methods for the Bighorn River near Fort Smith, Montana

Water samples are collected across the width of the river and pooled together before sending subsamples to the lab for chemical analysis.

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Water Chemistry

The Greater Yellowstone Inventory and Monitoring Network collects water samples quarterly generally following depth and width-integrated protocols outlined in the U.S. Geological Survey (USGS) National Field Manual for the Collection of Water-Quality Data.

We use a 1-L, hand-held DH-81 sampler affixed to a 1-m wading rod to collect depth and width-integrated water samples. At multiple locations along the river's cross-section, we collect water using vertically integrated sampling techniques. Samples from the 1-L bottle are mixed into an 8-L churn splitter to homogenize the sample and dispense a representative subsample into laboratory-provided bottles. These bottles are then shipped overnight or delivered to an EPA-certified commercial lab for processing.

Multi-parameter instrument measuring core water quality parameters on site.

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Core Water Quality Parameters

In addition to water samples, water quality parameters (temperature, specific conductance, dissolved oxygen, pH, and turbidity) are collected in situ using a handheld, multi-parameter instrument (e.g., YSI EXO 1 sonde) at four representative locations on the river cross-section. Collection of water sample core parameters and rationale for testing nutrients and suspended solids is described in the approved Greater Yellowstone Network Regulatory Water Quality Monitoring Protocol (O'Ney 2006).

River Discharge

Discharge (river flow estimates) and water temperature data from the Bighorn River sampling location are available online from the U.S. Geological Survey's National Water Information System and listed under station USGS 06287000. This station name is Bighorn River near St. Xavier, MT (actual location is near Fort Smith, Montana).

Greater Yellowstone Network Water Resources Protocols

Read the full protocols and standard operating procedures for water quality and discharge here.

Protocols and Standard Operating Procedures

Source: Data Store Collection 7853. To search for additional information, visit the Data Store.