Research and Development Office

Evaluating Future Agricultural Water Needs using Integrated Modeling Methods

Project ID: 1588
Principal Investigator: Jennifer Johnson
Research Topic: Agriculture Water Supplies
Priority Area Assignments: 2015 (Climate Change and Variability Research), 2016 (Climate Change and Variability Research)
Funded Fiscal Years: 2015, 2016 and 2017
Keywords: agriculture, water demands, land use, crop distribution

Research Question

The largest consumptive use of water in the Western United States is for the production of irrigated agriculture. Thus, predicting how the demand for agricultural water will be affected by climatic change is essential for understanding how the west's water resources can be sustainably managed in the future.
The scoping study 596, Scoping Methods for Evaluating and Computing Future Agricultural Water Needs, found that current methods for computing future agricultural water needs rely on methods that are primarily based on a system's reaction to physical changes, but ignores the water user decisions (such as crop choice and land use) that will significantly impact water demand. Agent-based models have been successfully used to simulate complex systems (land-use changes, population growth patterns, municipal water needs) and that they can be used to effectively test conceptual models that describe the relationships found in complex systems. However, there is not a model that exists that describes the specific features that are unique to a Reclamation project including the relationship between crop choice, water right priority dates, storage contracts, water availability, crop pricing.
The research question to be addressed by this proposal is: Can a conceptual model be developed from existing data that can be used to predict water user decisions related to crop choice and land use to more effectively determine future water demands? Can this model be verified and evaluated for uncertainty using an agent based modeling framework? Once a conceptual model is developed that can relate these factors and successfully project crop distribution and land use, future water needs can be quantified using the ET method recently developed by Reclamation and Desert Research Institute.

Need and Benefit

Reclamation is responsible for delivering water for irrigated agriculture in the western US. An important aspect of ensuring that water supplies remain viable into the future is understanding how the needs and demands of water users might change under possible future conditions. As mentioned in the Research Question section, current methods do not completely account for the impacts of potential changes to future demands such as land use changes or changes to crop distribution. This proposal addresses a need for more completely estimating future water needs so that Reclamation can more accurately plan for the future.
This project will incorporate data and methods from two previous efforts undertaken by Reclamation. (1) The West-Wide Risk Assessment (WWCRA) study used a sophisticated evapotranspiration (ET) calculator to quantify agricultural water needs for eight major river basins, but it was limited in that it used static, current land use and crop distribution. Once an appropriate model can be developed to predict land use and crop distribution changes, it will be paired with the ET calculator from the WWCRA study to calculate water demands. (2) Reclamation has been developing estimates of historical cropping patterns for all Reclamation projects for the Policy Office. This data will be used for the development of the conceptual model.

Contributing Partners

Contact the Principal Investigator for information about partners.

Research Products

Bureau of Reclamation Review

The following documents were reviewed by experts in fields relating to this project's study and findings. The results were determined to be achieved using valid means.

Evaluating Future Agricultural Water Needs using Integrated Modeling Methods (final, PDF, 4.2MB)
By Jennifer M. Johnson
Research Product completed on September 30, 2017

Evaluating Future Agricultural Water Needs using Integrated Modeling Methods (final, PDF, 4.2MB)
By Jennifer M. Johnson
Research Product completed on September 30, 2017

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