(WBIR) - Every year on March 15, all of Tennessee's tributary reservoirs begin their annual refill, but the Tennessee Valley Authority cannot fill the lakes on their own - they need some help from Mother Nature. 

"Between now and June 1, the amount of rainfall that we get during that period really will tell us how full our lakes will be heading into the summer season," said James Everett, who manages operations inside TVA's Forecast Center. 

READ MORE | TVA lake levels

Everett said even with the rainfall over the last couple weeks, the runoff levels are far behind normal.

"Every time we get a little bit of rain we are going to conserve as much as we can," Everett added. 

Some East Tennessee reservoirs have a long way to go. Cherokee Lake needs to come up 24 feet, while Fontana needs to come up 48 feet.

In order for all the lake to be at their summer recreation levels by June 1, we need to receive an inch-and-a-half or rain or runoff every week from now to June. 

TVA manages a total of 29 dams that produce power. Many of those will start to see levels rise over the next several weeks as the refilling process begins.

"We are starting in a good spot. Although it was dry during the winter, a lot of these reservoirs are where they are supposed to be for this time of year," Everett said.

Read more at WBIR's website.