State Water Resources Research Institute Program

Project ID: 2011MT239B
Title: Methods for estimating wetland evapotranspiration through groundwater flow modeling of diurnal groundwater fluctuations
Project Type: Research
Start Date: 3/01/2011
End Date: 2/28/2013
Congressional District: At-large
Focus Categories: Wetlands, Models, Methods
Keywords: Wetlands; Evapotranspiration; Diurnal groundwater fluctuations; groundwater flow modeling
Principal Investigator: Chandler, Kevin (Montana Bureau of Mines and Geology)
Federal Funds: $ 14,900
Non-Federal Matching Funds: $ 29,800
Abstract: As the demand and competition for water resources increases more precise regional water budgets will be needed to better manage Montana's limited water resources. The amount of water lost by wetlands is likely the greatest unknown in any water budget and often ignored in regional groundwater flow models. This project aims to develop methods for defining the aquifer conditions affecting evapotranspiration (ET) from wetlands by coupling MODFLOW based groundwater flow modeling with analyses diurnal groundwater fluctuations. The wetlands at Gartside Reservoir near Sidney, MT were the site of a previous hydrologic study and provide important historical data on water-level changes and information about the local hydro-stratigraphy. This site also provides a diverse set of wetland conditions with part of the area being drained for agricultural uses. Shallow monitoring wells and weirs will be installed in the wetland areas to measure water-level and surface-water flow changes during two growing seasons. Water-levels will be recorded on 15 minute intervals and consistent diurnal water level fluctuations will be analyzed for ET calculations. Meteorological data will be collected to evaluate the factors effecting wetland ET. Well bore cuttings will be analyzed to determine shallow aquifer properties. These data will be used to construct a transient groundwater flow model to simulate ET. The calculated ET rates and measured aquifer properties will be used for initial boundary conditions. Then the groundwater flow model will be calibrated to selected segments of the measured diurnal water-level curves through refinement of the initial boundary conditions.

Progress/Completion Report, 2011, PDF

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