March storms have left Southern Oregon's mountains loaded with snow heading into April, but federal flood-control managers are poised to capture spring runoff and avoid any flooding by leaving room in the region's two main reservoirs.

March storms have left Southern Oregon's mountains loaded with snow heading into April, but federal flood-control managers are poised to capture spring runoff and avoid any flooding by leaving room in the region's two main reservoirs.

The Rogue and Umpqua river basins boast a snowpack listed today at 138 percent of average, fed largely by a burst of spring storms that has left the region gray and wet for most of thepast month and swelled Rogue flows. That's more than twice the snowpack at this time last year.

The Rogue Valley does not have a history of catastrophic spring flooding like events that have hit the region on occasional Decembers, and the U.S. Army Corps of Engineers is not particularly worried about 2011 being a blip in that record.

But Corps hydrologists now have their main weapon against Rogue Basin flooding — Lost Creek Lake near Trail — at the low end of its normal spring filling schedule, with almost 6 more feet of space now than in Aprils past. Agency leaders plan to delay filling the 34-year-old reservoir by at least two weeks or even more beyond the traditional May 1 date to ensure enough space to capture extra runoff.

"Right now, we're considering delaying until mid-May," says Jim Buck, the Corps project manager at Lost Creek Lake. "We'll adapt the plans depending upon the conditions."

At Applegate Lake, however, the filling plan is on schedule to hit May 1, Buck says.

If the Corps were to fill the reservoirs just before a spring rain melts snow, the lakes would not have available space to control that freshet, Buck says. That would mean releasing the same amount of water that flowed into the projects, causing spikes in flows that in the past have harmed infant wild salmon by stranding them along banks or in side channels cut off from the river, Buck says.

Lower elevation snowpacks are lower in water content but still well above average heading into April, according to Natural Resources Conservation Service Sno-Tel sites throughout the region.

At King Mountain in Jackson County's northwest corner, Thursday's snow surveys found snow depths equal to 13.2 inches of water — 471 percent of average — at the 4,340-foot elevation.

At Bigelow Camp, 5,130 feet above sea level, the snow contains 26 inches of water, which is 224 percent of normal.

And at Big Red Mountain southeast of Ashland, the snowpack contains a hair under 40 inches of water, 142 percent of average. At 6,050 feet above sea level, that site is the highest among the dozen surveyed by the NRCS in the Rogue and Umpqua basins.

The Mt. Ashland Ski Area had a solid snowpack a year ago, with 109 inches recorded on March 30, 2010. One year later, the ski area reports in with 181 inches of snow, a 66 percent increase.

Area irrigation districts are primed to operate this spring and summer with full reservoirs to fill their ditches.

Agate Lake already is full, while Fish Lake remains 59 percent full beneath the ice.

Emigrant Lake is 91 percent full and Hyatt Lake is 95 percent full. Howard Prairie remains a hair over three-fourths full, but Talent Irrigation District Manager Jim Pendleton expects it, too, will fill.

Emigrant Lake provides a modicum of flood control in the Bear Creek basin, and Pendleton has slowed the lake's spring filling schedule enough to allow the lake to capture some heavy spring runoff.

Pendleton says altering out-flows at Emigrant Lake already has shaved Bear Creek flows several times during the recent spate of storms.

All that snow has proven to be way too much of a good thing at Diamond Lake in eastern Douglas County, where the snowpack is listed today at 173 percent of average.

Diamond Lake Resort events manager Rick Rockholt says 105 inches of snow fell there in March alone — less than two months after the lake looked primed to melt early.

"Back in January, I would have told you the lake will thaw in the middle of April," Rockholt says. "Now I'm praying for Memorial Day."

Like other high Cascade lakes, Diamond Lake is set to open for spring trout fishing April 23, but Rockholt expects that day to come and go without seeing the lake's watery surface.

"On the other hand," he says, "we can try ice fishing this year."

Reach reporter Mark Freeman at 541-776-4470 or email at mfreeman@mailtribune.com.