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Bay-Delta Office
Department of Water Resources

1416 9th Street,
Sacramento, Ca 95814

Mailing Address:
P. O. Box 942836,
Sacramento, Ca 94236-0001

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 IWFM: Integrated Water Flow Model

(Web Site Last Updated: October 16, 2017)

IWFM (Integrated Water Flow Model) is a water resources management and planning model that simulates groundwater, surface water, stream-groundwater interaction, and other components of the hydrologic system. IWFM models groundwater flow as a three-dimensional system and solves the governing flow equation using the Galerkin finite element method. A unique feature of IWFM is the land use based approach of calculating water demand. IWFM simulates stream flow, soil moisture accounting in the root zone, flow in the vadose zone, groundwater flow, and stream-aquifer interaction. Agricultural and urban water demands can be pre-specified, or calculated internally based on different land use types. Water re-use is also modeled as well as tile drains and lakes or open water areas. Another notable feature of IWFM is a “zone budget” type of post-processor that includes subsurface flow computations across element faces. IWFM was developed by staff in the Modeling Support Branch of the Bay-Delta Office who is responsible for its technical support.

There are two main documents for IWFM: "IWFM Theoretical Documentation" and "IWFM User's Manual". The documentation, executables, source code, and sample problems for the current and past versions of IWFM can be downloaded through the following links.

Current IWFM Versions

Archived IWFM Versions
IWFM Version 4.0
IWFM Version 3.02


IWFM is copyrighted by the State of California Department of Water Resources. It is licensed under the GNU General Public License. This means it can be copied, distributed, and modified freely, but you may not restrict others in their ability to copy, distribute, and modify it. See GNU General Public License for more details.

Support Tools

IWFM Demand Calculator (IDC)

Related Publications
For the reports discussing the comparison of IWFM and MODFLOW-Farm Process, click here.

Users Group
The IWFM users group is part of CWEMF, hosted by both DWR and USBR in an effort to encourage development and understanding of the model. Information pertaining to the upcoming quarterly meetings, as well as information regarding the previous meetings will be accessible through the CWEMF website or through here. If you're new to the users group please send Can Dogrul your contact information so we can update you on the next meeting.

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