Modeling Resources

Evapotranspiration and Consumptive Irrigation Water Requirements for Idaho – This University of Idaho website can be used to determine evapotranspiration (ET) and net irrigation requirements (NIR) for crops throughout the state of Idaho.

ESPA Modeling Tools

The ESPA Modeling Tools provide to the water management community a common way to analyze the hydrologic impacts of new water right applications, transfers, and Water Supply Bank rentals within the Eastern Snake Plain Aquifer (ESPA). These tools enable users to evaluate the potential for a proposed transfer within the ESPA to affect flows in the Snake River. In the event that the ESPA Modeling Tools show that the proposal could injure prior rights, the spreadsheets will reveal the extent of the mitigation necessary. The applicant can then draft a mitigation plan which minimizes injury to senior rights and create an application which complies with the ESPA moratorium order.

Quick Guide to the ESPA Modeling Tools

Changes to groundwater use in the ESPA can change the location of depletions in the river and in the tributary springs. An ESPA model analysis is necessary to quantify those depletions so injury to other water rights can be identified and avoided or, if possible, mitigated. This guide is a resource for completing groundwater modeling required for water right transfers in the ESPA.

Use of the ESPA Model Transfer Spreadsheet (ETRAN) & Mitigation Analysis Spreadsheet for Water Right Transfers in the Eastern Snake Plain Aquifer

UPDATE

The ESPA Modeling Tool ETRAN 3.3 was recently updated to ETRAN 3.4. The difference in user interface functionality between ETRAN 3.3 and the updated ETRAN 3.4 is negligible— the updated version executes ESPAM Version 2.2 MODFLOW files instead of ESPAM Version 2.1 files. ESPAM Version 2.2 superseded ESPAM Version 2.1 in May 2021. The calibration of ESPAM Version 2.2 incorporated groundwater flow modeling improvements to the representation of aquifer interaction with the Snake River in the Heise to Shelley, near Blackfoot to Neeley, and Neeley to Minidoka reaches, and the extension of the calibration period to include water years 2009 through 2018. ESPAM Version 2.2 is accepted as the best available science. Incorporating ESPAM Version 2.2 into the ETRAN 3.4 tool provides the water management community a common way to use the best available science to analyze the hydrologic impacts of new water right applications, transfers, and Water Supply Bank rentals within the ESPA. For a complete list of previous updates between versions, see the ESPAM22readme.txt file inside the zipped folder download.

IDWR will accept modeling completed in ETRAN 3.3 or ETRAN 3.4 until May 1^st, 2022. In an effort to direct users to the latest version, ETRAN 3.3 is no longer available on this website. IDWR no longer accepts modeling completed with ETRAN 3.2. If you have an extenuating need to obtain a copy of ETRAN 3.2 or ETRAN 3.3, please contact us.

How to use the ESPA Modeling Tools

Locate and identify your grid cells.
Use IDWR’s interactive map server to identify ESPA model grid cells for use in the next step.
- ESPA Model Grid Cells
Run the model.
The ESPA Model Transfer spreadsheet was designed for individuals with little experience using groundwater modeling software. Download the zipped folder, open the ETransfer spreadsheet, and then add your inputs to the Data Entry tab. Be sure to read the data entry notes in green before running the model. Once you run the model, copy the data at the bottom of the Calculated Effects tab and place the data into the Mitigation Analysis spreadsheet.
- ESPA Model Transfer (ETRAN_3.4)
Analyze the results.
The ESPA Mitigation Analysis spreadsheet is compatible with the ESPA Model Transfer spreadsheet. Use the ESPA Mitigation Analysis spreadsheet to analyze depletions to 11 reaches of the Snake River. Compare the model results of your proposal with IDWR’s mitigation threshold values to determine of mitigation will be necessary.
- ESPA Mitigation Analysis

Additional Information

ESPA Model Transfer User’s Manual
This manual describes how to use the ESPA Model Transfer spreadsheet to analyze the effects of proposed groundwater transfers on the flows of the Snake River. The manual was written for ETRAN 3.1, but it is equally applicable to ETRAN 3.4.
Discussion of the Use of the Transfer Tool and Performing Mitigation Analysis Associated with Various Water Right Processes
This document summarizes some of the basic capabilities of the ESPA Model Transfer spreadsheet as well as the analysis methods used by IDWR in the Mitigation Analysis spreadsheet.
IDWR will accept modeling completed in ETRAN 3.3 or ETRAN 3.4. In an effort to direct users to the latest version, ETRAN 3.3 is no longer available on this website. IDWR no longer accepts modeling completed with ETRAN 3.2. If you have an extenuating need to obtain a copy of ETRAN 3.2 or ETRAN 3.3, please contact us.