Lake Tahoe's water clarity is trending in a positive direction.

UC Davis scientists say the average clarity reading for last year was just over 70 feet.

Even though that's five feet less than 2012, it's much better than the low levels recorded through the '90s.

"Basically we go out in the middle of the day, and we lower this 10-inch white disk, and we have a trained observer, and what he records is the depth at which this white disk disappears," said Jeff Schladow with the UC Davis Tahoe Environmental Research Center. 

Schladow says storm water runoff is a major contributor to reduced clarity but regulations on construction and restoration projects are working.