Irrigation in the Pacific Northwest

Irrigation Scheduling Aids and Tools

There are a variety of practical and useful tools referenced here depending on what works best for your particular skills, operation, habits, and preferred methods of doing business.  Be warned that many of these products are unsupported.


Paper and Pencil

For those that like to keep things simple and don’t spend much time on a computer.  These tools require that you fill in an evapotranspiration (crop water use) estimate, rainfall, and any irrigation amounts.

Based on Historical Long-Time Averages

Long term historical water use estimates are good for getting estimates of when and how much to water.  However as we all know, no year is average and there are large variations in weather that causes crop water demand to change quite a bit over a season.  The below two methods are inflexible in this regard can therefore be expected to be less accurate.

Irrigation Scheduling Checkbook Method

Review:  This is a checkbook method of managing the soil water “bank account” that is simple to use and easy to understand.  It was developed by Jerry Wright at the University of Minnesota.  The water use tables necessary to populate these have not been put together for the Pacific Northwest states, but should be available soon.

Missouri Irrigation

Review: This website contains great tools that are based on historical average ET.  The charts need to be custom created for a particular location and crop using historical average ET, but once that is done copies of the same chart can be used over and over again year after year.  This is an intuitive way to monitor irrigations and can give “ballpark” estimates of when and how much to irrigate.  Currently these charts cannot be created for Pacific Northwest states, but should be available soon.

Requires regular updating with ET estimates

Irrigage-Crop Coefficients and a Recordbook

NRCS Irrigation Scheduling Recordbook

Review: This is a handy book that can fit in your pocket or above the visor in a pickup.  This was developed by Peter Robinson with the USDA National Resource Conservation Service.



Spreadsheet irrigation schedulers are for those who like MS Excel, and like to let the computer do all of the math.  These tools require that you fill in a daily evapotranspiration (crop water use) estimate, rainfall, and any irrigation amounts.  One of the advantages of spreadsheet programs is that they can be flexible and give people a look into the guts of how they work if they are so inclined.  However, many spreadsheets are protected so that they cannot be modified thereby over-riding this advantage.

Checkbook Irrigation Scheduler and Turfgrass Irrigation Management

Review: These are MS Excel workbooks (spreadsheets) pointed mostly towards turfgrass.  I found them to be a little overly simplistic and inflexible.  There is a turfgrass irrigation management (TIM) and a checkbook irrigation scheduling (CIS) workbook.  Both of these were developed by the Northern Colorado Water Conservancy District.

Basic Irrigation Scheduler (BIS)

Developed in California by Richard Snyder et. al.  This spreadsheet requires monthly average solar radiation, maximum and minimum temperatures, windspeed, dewpoint temperature, precipitation, and the number of rainy days per month.  This type of data may be difficult to obtain for the novice.  The spreadsheet is complete and accurately done, but the average user will probably find it difficult to use and hard to understand.  There is an online manual to help through many of these issues.


Review: Kansched was developed in Kansas (obviously) by Gary Clark, Danny Rogers, Mahbub Alam, and others from Kansas State.  They have a more recent compiled version of Kansched, Kansched2, which I think is easier to use.  Despite this, Kansched.xls is one of the most intuitive spreadsheet irrigation schedulers around.  It must be populated daily with reference evapotranspiration estimates for another source.  It also must be populated with crop coefficients, root depths, and season dates.

Compiled Programs

These are programs that you download and operate directly on your computer.  There is no need for other software (like Excel) and the know-how to use them.  These programs tend to be a little bit easier to use than the spreadsheet versions and are often more intuitive.  These tools require that you fill in a daily evapotranspiration (crop water use) estimate, rainfall, and any irrigation amounts.


This was developed by Gary Clark, Danny Rogers, Mahbub Alam, and others from Kansas State University.  This is one of the best developed and supported software packages for irrigation scheduling in my opinion.  It was obviously developed for use in Kansas, but will work fine in the Pacific Northwest states.  It requires the user to provide the evapotranspiration and irrigation amount data.  This data is available for the Pacific Northwest states from Agrimet, or from the Washington AgWeatherNet.  It only has crop coefficients for a few crops that are common in Kansas, but it has the flexibility of including custom crops and crop coefficients. 


Online Programs

These are integrated with existing online sources of evapotranspiration data.  They can be used from any computer that has internet access.  The advantage of these online programs is that they can connect to existing online data sources and can update themselves automatically with rainfall and evapotranspiration estimates from weather station networks.


Review:  IWM-Online was developed by Marshall English and Charles Hillyer at Oregon State University.  This is the Cadillac of all irrigation scheduling programs.  It has water supply optimization algorithms for the most productive use of water among different fields.  It really is ideal for larger operations with dedicated irrigation managers and that have difficulty deciding how to allocate limited water resources, especially during times of water shortages.  Because it is so capable, it is also kind of complex for those who are new at irrigation scheduling.

NDSU Irrigation Scheduling Online

This was developed by Thomas Scherer at North Dakota State University.  Although it currently only works for North Dakota, a similar version for Washington state is being worked on and will reside within AgWeatherNet.


WSU Prosser - IAREC, 24106 N Bunn Rd, Prosser WA 99350-8694, 509-786-2226,