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Kirti Rajagopalan, left, and Dr. Muhammad Barik

Kirti Rajagopalan, left, and Dr. Muhammad Barik

Agriculture is a major player in the economy of the Columbia River Basin that spans several states in the Pacific Northwest and Canada, and the crop mix is diverse.

Any changes in climate can have significant impacts on agricultural production through changes in crop growth patterns and water availability.

Elevated atmospheric carbon dioxide levels, increased temperatures and changes in precipitation patterns are among the factors affecting future agricultural production, and they could result in positive or negative consequences.

For example, increased temperatures can lead to a negative effect through accelerated plant development, earlier crop maturity and resulting lower yields.

However, higher temperatures also increase the length of the available growing season and lead to a positive effect for some crops.

Elevated atmospheric carbon dioxide levels can result in increased crop productivity and water use efficiency for certain kinds of crops.

Earlier snowmelt, more precipitation falling as rain instead of snow, increased cold season precipitation and decreased summer season precipitation, all result in changes in irrigation demand as well as water availability, thereby impacting agricultural production.

The balance between these competing individual effects determines the overall net effect that is crop and region specific, and this net effect also has the potential to change over time.

A team of researchers led by Dr. Jennifer Adam, associate professor and associate director of the State of Washington Water Research Center (SWWRC) at Washington State University, examined the effects of climate change on future water supply as well as demand in the Columbia River Basin.

In the 2030s, we expect to see a small increase in water supply of the order of 5 percent on an annual scale for the basin.

However, there is an increase in cool-season water availability and a decrease in summer-season water availability, which is the season of highest agricultural water demands.

There are also differences by subregion. For example, the Yakima River Basin is an area that currently experiences water stress, and this stress is expected to be worse in the 2030s.

On the irrigation demand side, we also expect to see increases of about 5 percent on an annual scale, and there are differences by crop and region.

Pastures and crops such as hay and alfalfa that can make use of a longer available growing season will see larger increases in irrigation demands.

Perennials such as orchards will see small increases in irrigation demand.

Even though the perennial crops are harvested earlier under elevated temperatures, they need to be irrigated throughout the growing season.

Other annual crops will see decreases in irrigation demands because, under warmer temperatures, they can be planted earlier in the year when precipitation tends to be higher and they mature faster due to accelerated growth.

We should also note that in addition to these “average” effects, changes in the magnitude, frequency and timing of precipitation and temperature “extremes” also affect agriculture.

In 2015, the region faced a snow drought (enough overall precipitation, but not enough snow), which affected water availability and hence agricultural production across a variety of crops.

Based on climate projections, we expect to see these types of events occur more frequently and for longer durations in the future.

Changes in climate affect future agricultural production in multiple ways, and there are implications for water managers, agricultural producers and other decision makers in terms of developing long-term strategies for addressing those effects.

A team of people from Washington State University, the University of Utah and Aspect Consulting are currently working with the Washington State Department of Ecology to extend previous work and create a water supply and demand forecast for 2035.

The associated reports are expected to be available in November 2016, and outreach meetings will be held earlier in the year. We encourage everyone to engage in the process and provide feedback. •

– a research report by Kirti Rajagopalan and Dr. Muhammad Barik

Kirti Rajagopalan is a research associate with the Center for Sustaining Agriculture and Natural Resources at Washington State University. Muhammad Barik, Ph.D., is a research associate and postdoctoral fellow with the Department of Civil and Environmental Engineering at Washington State University.

Online

This work was funded by the Washington State Department of Ecology and the reports generated through this work can be accessed online at bit.ly/1ms1a6Y