Sahuarita Lake, 18 miles south of Tucson, is popular with anglers, boaters and those who walk or run along its lakeside path. But some visitors might wonder what causes the lake’s water to be so dazzlingly blue or aquamarine, depending on the light.

Short answer: highly concentrated lake dye added to the water two or three times a year.

While the dye imparts a pleasing hue to the 10-acre lake, its main purpose is to control weed and algae growth in the water, said Brian De Breceny, parks and facilities manager for the community of Sahuarita.

“We take a natural approach in maintaining the lake,” De Breceny said. “Rather than use harsh chemicals, we try to control weed and algae growth in as natural a way as possible. The highly concentrated lake dye filters the sunlight and slows photosynthesis.

“It’s absolutely nontoxic,” De Breceny said. “It’s added to the lake as needed. It could be two times a year or three times a year.

“It’s a liquid applied by our aquatic biologist. One 2ƒ-gallon jug will treat the entire lake.”

AQUATIC ATTRACTIONS

The lake, which was created in 2000 and opened for use in 2001, attracts visitors for reasons beyond its eye-catching blue waters.

“It’s a very popular spot,” De Breceny said. “The most popular uses are boating and fishing and, of course, walking and running” on the mile-long trail around the lake.

Anglers catch fish including rainbow trout and catfish from the lake depending on the season, and the fish can be eaten. An Arizona general fishing license, community fishing license or combination hunting and fishing license is required.

Boats must be powered by an electric motor or be human propelled, De Breceny said. “No gas motors are allowed on the lake.”

He said a boat concession operates at the lake on weekends — renting paddle boats and kayaks.

Facilities around the lake include restrooms, fitness stations and an amphitheater for special events.

The lake is at 15466 S. Rancho Sahuarita Blvd., in Sahuarita. Admission is free.

Contact reporter Doug Kreutz at dkreutz@tucson.com or at 573-4192. On Twitter: @DouglasKreutz