IWFM (Integrated Water Flow Model) / IDC (IWFM Demand Calculator)
Criterion | Explanation |
General Description | IWFM (Integrated Water Flow Model) is a model for water resources management and planning. It simulates surface and groundwater movements and uses due to agricultural and municipal/industrial sources. IDC (IWFM Demand Calculator) is a standalone module that can be used to calculate the water demand by itself. |
Model Domain | The model domain consists of a user-specified model area, including land surface, surface water streams, and unsaturated/saturated zones under the land surface. |
Developer | CA Department of Water Resources (DWR) |
Hardware computing requirements | None given |
Code language | FORTRAN |
Original application | Simulation of surface and groundwater flow, soil moisture, and consumptive water use |
Public/proprietary and cost | Distributed under the GNU General Public License v3.0; Free of charge |
Physically or empirically based | Physically based |
Mathematical methods used | Groundwater flow in the saturated zone is a numerical solution of the Richards' equation via the Galerkin finite element method. Surface flow routing to streams is pre-specified by the user with flow rates based on a Soil Conservation Service (SCS) curve number (CN) approach. Surface flow routing between stream nodes takes a mass balance approach with surface levels determined by a user-specified curve number. Evaporation for each land use type is user-specified as a time series input. |
Input data requirements | Input data consists of aquifer stratigraphy, land-use information, surface water flow boundary conditions, precipitation and ET boundary conditions. |
The ease of assembling this information depends on the specific model domain and application. | |||||||
Outputs | Spatial and temporal detail is model-dependent. Surface and groundwater budget data is saved in a proprietary binary format. The model includes post-processing programs to extract desired features into whitespace-separated text files. | ||||||
Pre-processing and post-processing tools | IDC is a standalone component for the water demands in IWFM. There is a IWFM mesh generator plugin for ArcMap to generate finite-element meshes. A plugin for Microsoft Excel is available to help import model output and format time series data. Soil builder tools, either with or without ArcMap integration, exist to process NRCS SSURGO soil database information about the root zone into IWFM's input file formats. IWFM PEST utilities aid automatic calibration of model parameters. A land use adjustment preprocessor is available to generate time series data for land uses. | ||||||
Representation of uncertainty | Not explicitly represented in output; could be implemented via multiple scenarios | ||||||
Prevalence | Best-known application is CA DWR's C2VSIM, a model of California's Central Valley surface and groundwater use. IWFM has also been used for modeling local domains by other agencies in California. | ||||||
Ease of use for public entities | Model documentation is detailed and understandable. Largest barrier to entry for a novel application would likely be quality data on aquifer stratigraphy and land-use. | ||||||
Ease of obtaining information and availability of technical support | There is an IWFM users group, and the model developers are able to respond to well-formulated questions. | ||||||
Source code availability | Yes, publicly available on the model website | ||||||
Status of model development | The model is mature but continues to receive new features and improvements (latest release April 2018). | ||||||
Challenges in integration | Because the model is open source, well documented, and has an active user and development community, challenges to integration are few.
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