The concept of covering the CAP canal system with solar panels has been longstanding and arises frequently.

The basic idea is usually that a solar panel-covered CAP canal would prevent evaporation and generate renewable power supplies that could be used to move water through the system.

This opportunity has been studied a number of times during the past decades by the federal Bureau of Reclamation and CAP and the conclusions have been that building such a solar covering would be inefficient for several reasons.

Here are a few:

• Construction difficulties. It’s much more difficult to build a support structure that spans the canal than typical solar array systems that are built on the ground.
• Sun-tracking technology. Solar arrays built to span over the canal system can’t be readily created to track the movement of the sun (and so would lose efficiencies).
• Inefficient maintenance demands. We’d have to regularly remove the solar panels to inspect the concrete canal liner and other canal features for damage (this would be very costly and time consuming).
• Geographical challenges. The CAP canal system runs through many remote areas that do not have electrical transmission systems nearby and building one to move the power from the solar arrays to the main points of use (at the pumping plants) is also very costly.
• Prohibitive overall cost. The Bureau of Reclamation, which originally constructed CAP, has conducted studies of this possibility and also found the cost to be prohibitive. Covering the canal would have quadrupled the $4 billion the project originally cost.
• Evaporation. Some believe putting solar panels over the canal would reduce evaporation and thus save a lot of water. But evaporation from the canal is minimal, about 16,000 acre-feet of water per year. Even if all of the evaporation from the canal was eliminated, it would not justify the expense of solar panel construction and the resulting operational challenges. Read more.

CAP has found new, more cost-effective opportunities to tap into solar energy, utilizing solar sites rather than covering the canal. This includes entering into long-term power purchase agreements with solar facility operators to purchase the power developed by land-based solar facilities that are located near existing large power transmission lines.

We hope this helps answer this interesting and popular question.