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Montana Prairie Wetlands and Intermittent/Ephemeral Streams: Hydrologic Needs Assessment for Healthy Watersheds
Jennifer Phelan, Phillip Jones, and Kimberly Matthews

ELOHA was applied to northeastern Montana wetlands, representing a new application for the framework and highlighting an approach to the task of establishing hydrology-ecology relationships that elucidate the connection between water regimes and the needs of healthy ecosystems. The primary goal of this work was to identify precautionary limits to hydrologic alteration at the level of hydrologic features and at the broad landscape scale.

In this study, hydrology-ecology hypotheses were developed using a standard form that mapped a hydrology regime change caused by an event or activity, such as climate change or prairie development, onto stresses induced in particular indicator organisms. From a group of twenty such hypotheses, one was selected as the basis for the proof-of-concept case study.

Hydrology-Ecology Hypothesis:
"Altered hydrology of wetland and intermittent/ephemeral stream systems negatively impacts amphibian populations and communities."

The case study was performed under challenging conditions of limited data using a modification of The Nature Conservancy's hydrology–ecology framework consisting of the following categories:
• Hydrology–Ecology Hypotheses
• Biological Indicator
• Biological Metric
• Hydrologic Feature Type
• Hydrologic Metric
• Timing of Biological Impact
• Impact
• Hydrologic Alteration
• Precautionary Limits of Hydrologic Alteration and Management Actions
• Supporting Literature
• Potential Supporting Data
Due to limitations on data availability, a variety of proxy datasets was used, including land use and cover, wetland inventory, groundwater information, and disturbance index data. The most significant relationship found was that as human development index (HDI) increases, amphibian diversity decreases. The quantification of this relationship could be used to set limits on human disturbance with the goal of protecting amphibian diversity and the level of ecological health that this diversity indicates.

Recommended next steps in the determination of healthy watersheds and ecological flows for Montana prairie wetlands are:
• Determine relationship between human disturbance and hydrologic alteration
• Update this study using grid-scale HDI values, which were not available at the time of the analysis
• Explore the relationship between HDI and other biological groups, including macroinvertebrates and fish
• Incorporate additional hydrologic datasets expected to become available for the study area, such as USGS’s Stream Stats
• Target biological sampling in regions where wetland change comparisons using National Wetlands Inventory (NWI) and Montana Wetland and Riparian Framework data may be justified.

For more information on this case study contact:


Jennifer Phelan

RTI International
3040 E. Cornwallis Road
Research Triangle Park, NC 27709