In the northern San Joaquin Valley of California, orchards stretch toward the snow-capped Sierra Nevada mountains, and a narrow canal cuts through the farmland below. Rising above the water is an unexpected sight: a canopy of solar panels. In their shade, Project Nexus is testing a deceptively simple idea: What if the same infrastructure that moves water across California could be used to generate clean energy and conserve water?
That question is at the center of the California Solar Canal Initiative (CSCI), a broader research and planning effort led by USC Dornsife Public Exchange and Solar AquaGrid, in collaboration with private, public, and academic collaborators. As California faces rising demand for clean electricity, strained water supplies, and limited land for new renewable energy infrastructure, CSCI is exploring whether the state’s roughly 4,000 miles of canals could become an untapped climate solution.
Project Nexus is where that idea is being tested in real-world conditions. The pilot installed solar canopies over operating irrigation canals to study how much energy they generate, how they affect evaporation and water quality, and how they fit with the everyday needs of canal operators.
UC Merced researchers are using sensors and running tests under the solar arrays and in open canal sections to measure how shade changes evaporation, water quality, and aquatic weed growth. The early results are striking. After one full irrigation season, researchers measured a 50-70% reduction in evaporation under the solar canopy, along with an 85% reduction in aquatic weed growth.
For irrigation districts, that second finding is more than a biological detail. Less growth means fewer cleaning cycles, less maintenance, cleaner water, and potentially lower costs. Matt Kincannon, Equipment Operations and Pest Control Division Manager for Turlock Irrigation District (TID), shared, “We haven't had to do any kind of cleaning to remove algae under the solar panels during the entire irrigation season, where we normally have a two-to-three week rotation cleaning schedule.”
Project Nexus is also answering the practical questions that determine whether innovation can scale. The pilot includes both wide-span and narrow-span structures so partners can learn how designs perform across different canal types and maintenance needs. At both sites, the arrays are designed with enough clearance for crews to access and maintain the canal.
The lesson is clear: Scaling solar canals will require more than strong sun. It will require designs that work for the people who manage water every day.
That is why partnership is at the center of the project. No single institution could execute this project alone; it depends on utilities that understand operations, scientists who can measure benefits objectively, public agencies ready to invest in new models, and partners willing to imagine what existing infrastructure can become by applying a dual-use mindset.
Now the work is moving from pilot and proof of concept to pathways to scale. The partnership, led by USC Public Exchange and Solar AquaGrid, involves faculty from seven leading research universities with expertise in policy, law, economics, energy, hydrology, and environmental justice. Together, they are developing a decisionmaking framework and mapping tool to identify specific locations and community use cases across California that are ideally suited to solar over-canal systems. As Professor Roger Bales, from the UC Merced study, puts it, “Project Nexus demonstrates that canals can do more than move water. Now the goal is not to simply build more solar over canals, but to build the right solar over the right canals.”
The interest in this innovation already reaches beyond California. Project leaders have had inquiries from across the United States, as well as from Egypt, Central Asia, Jordan, and other places looking for ways to produce food, conserve water, and build renewable energy at the same time.
Project Nexus does not ask California to choose between saving water, conserving land, generating energy. It asks whether one well-designed intervention can advance all three. The canals will continue to do what they have always done: carry water to communities and farms. But with innovation, partnership, and the will to scale what works, they may also help power a more resilient future.
Discover how the California Solar Canal Initiative is transforming California's existing water infrastructure into a model of the clean energy transition here.