Since mid-December, Don Pedro Reservoir has risen nearly 31 feet thanks to the El Nino rains that appear to have ended the four-year California drought. But it's still remains a far cry from where it normally is this time in the year.

The reservoir on the Tuolumne River stood at 692.38 feet above sea level on Jan. 19, up from 676.68 feet on Dec. 20. As of Monday, the lake stood at 707.6 feet.

For it to be filled to the brim at 830 feet, Don Pedro would have to rise another 122 feet and most weather experts say that's not going to happen in a single rain year.

The lowest the lake has been was in 1977 when it dropped to 598 feet.

The storage numbers give a better picture of just how much catching up the lake has to do. The lake's maximum storage level is 2,030,000 acre-feet. An acre foot is equivalent to a foot of water covering one acre. As of Thursday, the lake contained 834,020 acre-feet of water, which is about 41 percent of capacity.

Holding more promise in filling depleted lakes is the snowfall in the Sierra Nevadas.

California Department of Water Resources Director Mark Cowin said the heavy snowfall so far during the water year 2016 "has been a reasonable start, but another three or four months of surveys will indicate whether the snowpack's runoff will be sufficient to replenish California's reservoirs by this summer."

Each water year begins on Oct. 1 and ends on the following Sept. 30. DWR conducts five media-oriented snow surveys in the Sierra Nevada each winter - near the first of January, February, March, April and May - at the Phillips Station plot (elevation 6,800 feet) just off Highway 50 near Sierra-at-Tahoe Road 90 miles east of Sacramento. Frank Gehrke, chief of the California Cooperative Snow Surveys Program, said more than four years of drought have left a water deficit around the state that may be difficult to overcome in just one winter season.

"Clearly, this is much better that it was last year at this time, but we haven't had the full effect of the El Niño yet," said Gehrke. "If we believe the forecasts, then El Niño is supposed to kick in as we move through the rest of the winter. That will be critical when it comes to looking at reservoir storage."

The state's largest six reservoirs currently hold between 22 percent (New Melones) and 53 percent (Don Pedro) of their historical averages in late December. Storage in Lake Shasta, California's largest surface reservoir, is 51 percent of its Dec. 30 average. [The December 30th] manual survey found a snow depth of 54.7 inches - 16 inches more than the average depth measured there since 1965 - and 16.3 inches of water content, 136 percent of the January 1 average for that site.