Project aims to better understand water demands from extreme heat

Gentle mist floating over orchards may not seem to amount to much water, but those fine droplets can add up to big trouble when extreme heat means a lot of misting-and potentially greater conflict over water use.

A project to better understand, and help balance, future water demands during high temperatures recently received a $650,000 grant from the U.S. Department of Agriculture. The project funds a Washington State University-led team to use Columbia River basin watersheds as case studies to model potential water demand for multiple uses. These are generally categorized as "out-of-stream withdrawals" for agricultural uses and "in-stream flow" needs for ecosystems, endangered fish species, and even hydroelectric power.

The hope is that science-backed information can help create constructive conversations now to prepare for a hotter climate in the future.

"We live in this area where there are limited water resources that we're trying to use efficiently across a whole range of uses, so we want to make sure that moving forward in a climate change scenario, we have sustainable water resources to meet all of the needs," said Kirti Rajagopalan, a WSU biological engineer and principal investigator on the project.

One part of the project is to better quantify the need for "evaporative cooling," such as the misting often necessary to save tree fruit like apples as well as grapes and other berries from getting burnt by the sun.

Many growers employ cloth netting to shade the fruit when it gets hot, but as an earlier WSU study has showed-that netting won't be enough when future climate conditions send temperatures higher for longer periods of time.

"Shade netting wasn't as effective in reducing fruit surface temperatures, requiring more reliance on evaporative cooling," said Rajagopalan. "We are potentially quite significantly underestimating the amount of additional water that's needed in the future for agriculture, and obviously we don't want to be in that situation."

The research team will be talking directly with growers and irrigation district officials to make sure the modeling reflects real world situations.

Better quantifying the problem is one aspect of the project. Another big part is to come up with potential solutions that can meet water needs across a broad range of in-stream and out-of-stream uses. For that, the team will be holding a lot of conversations not just with growers but also with agencies such as the state's Department of Ecology, and the Department of Fish and Wildlife as well as nonprofits like Trout Unlimited.

The WSU-led team will be looking for adaptations that will benefit all sides. On the agricultural side, that means potentially finding other cooling strategies that require no water or less water, and on the in-stream side, perhaps looking at specific practices and timing when keeping water levels high is most important to the ecosystem and for fish.

"Understanding where those opportunities might lie really depends on talking to folks who are involved with that aspect of the work," said Sonia Hall with the Center for Sustaining Agriculture and Natural Resources.

Hall and Rajagopalan are part of a collaborative team of WSU researchers including Lee Kalcsits, Mingliang Liu, Troy Peters Georgine Yorgey, and Matt Yourek. The interdisciplinary team will help integrate the scientific quantification of the problem with the on-the-ground experience of the various interest groups. While the project is currently localized to the Columbia River watershed, the findings could help inform approaches in irrigation areas across the West that face similar water use issues. "If we all share an understanding of what the problem is, its extent, and possible opportunities for solutions that help the whole system - then science can help set the stage for more productive conversations," said Hall.

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