Kelley Drechsler: Reducing Water Use in Almond Orchards

During droughts, California’s nut farmers are often criticized for their water use, though the crops they produce are a cornerstone of the state’s economy. Third-year Ph.D. student Kelley Drechsler is taking on this problem by working to help these farmers irrigate using less water without affecting their product.

She does this through two different projects. One focuses on efficiently irrigating almond orchards. Typical almond orchards contain 2-3 varieties of almond tree to facilitate cross-pollination as they grow. These different varieties produce almonds of different sizes, shapes and flavors for different applications, but they all grow according to different growth schedules, and each growth stage requires different amounts of water.

Her solution is a remote irrigation control system that waters each variety of tree according to its growth schedule. This will make sure farmers aren’t using water they don’t need to. She also looks at how resistant each variety is to regulated deficit irrigation, or replacing less than 100% of the water each tree loses each season through evaporation and transpiration, or evapotranspiration (ET).

“We don’t know if some varieties are more tolerant than others,” she said, “But if water availability is changing, regulated deficit irrigation might become a very practical tool for achieving production levels.”

Her other project involves studying young almond trees. Most studies of water use are done on mature trees, but many of the state’s orchards are still young and there isn’t good data on their water use. So, she is measuring the water use of young almond trees from ages 1-5 years as they mature to estimate evapotranspiration and crop coefficients.

“Farmers can schedule irrigation based on those ET estimates,” she explained. “If you know the ET, you can just replace whatever that amount of water is lost through ET through irrigation.”

Drechsler came to UC Davis as an undergraduate in biological systems engineering and has been part of the Department of Biological and Agricultural Engineering ever since.

While working on her senior design project, she met distinguished professor Shrinivasa Upadhyaya, who was impressed with her work and offered her a position in his lab after she graduated. She soon decided to pursue her M.S., which she completed in spring 2019. She then decided to stay at UC Davis to pursue her Ph.D. as part of Associate Professor Isaya Kisekka’s group.

In addition to research, Drechsler is an active teaching assistant who hopes to gain education experience in the field. She has TA’ed for multiple courses, including Irrigation Systems and Water Management (HYD 110) and Introduction to Geographic Information Systems (ABT/LDA 150). Her goal is to build a wide skillset of teaching, research and engineering that she can apply to multiple fields after she completes her degree.

“You can focus your Ph.D. research on something very specific, but still translate it to many different topics and fields of science,” she said. “By studying something in so much depth, you realize where it fits in the larger picture of science and engineering and learn what other things are out there.”