29 June 2010

Intensive Rains Affecting Tern and Plover Season

The 2010 Least Tern and Piping Plover season in Nebraska is being dramatically impacted due to flooding from the extensive, recent rains. Nests have been lost due to flooding, and renesting is currently underway.

"Heavy rainfall on June 12-14 caused flooding on the Niobrara River, Ponca Creek and Choteau Creek, all of which drain into the Missouri River above Lewis and Clark Lake, the reservoir formed by Gavins Point Dam," according to Gregory Pavelka, program manager for the Tern and Plover program operated by the Army Corps of Engineers, Omaha District.

"The lake rose nearly four feet which partially inundated the sandbar complex constructed by the Corps of Engineers to provide nesting habitat for least terns and piping plovers. A survey on June 15 of the complex found that 21 plover and 18 tern nests were lost to flooding. However 52 plover and 86 tern nests survived the flooding. Surveys on the complex on June 22 and 23 found that 16 new plover and 33 new tern nests had been initiated since June 15."

There was additional high water levels associated with tributary rivers in the region of the Missouri National Recreation River.

"The same widespread rain event that caused Lewis and Clark Lake to rise also caused flooding on the tributaries below Gavins Point Dam," Pavelka said. "The James River flows into the Missouri increased from 4,400 cubic feet/second (cfs) to over 24,000 cfs. The Vermillion River rose from 380 cfs to 4,400 cfs.

"The Missouri just below the confluence with the James was running at more than 57,000 cfs and the river gage below the James River confluence at Gayville rose three feet," according to Corps' officials. "The Maskell gage near Vermillion, SD rose 3.5 ft. and the gage near Ponca, NE rose five ft. Flows at Ponca probably were in excess of 62,000 cfs.

"These high flows completely inundated the Corps' constructed sandbars at River Mile (RM) 795.5, 775.0 and 774.0 and partially inundated the constructed sandbars at RM 791.5, 781.5 and 777.7. A total of 59 piping plover and 50 least tern nests below Gavins Point were lost to flooding by the high flows.

There have been five successful Piping Plover nests thus far this season, and 12 active nests remain in this same section of the Missouri below Gavins Point Dam.

"Surveys completed by June 25 show that eight new piping plover and 37 new least tern nests have been initiated on the sandbars at RM 791.5, 781.5 and 777.7, since the flooding that occurred on June 14," according to the Corps.

Prior to the recent rains Gavins Point releases were varying between 26,500 and 28,000 cubic feet per second, said Michael Swenson, of the Water Management Division, of the Army Corps of Engineers. "Releases were cut to 22,000 cfs (June 12), to 15,000 cfs earlier the week of June 21, but are being increased again," he said. They were then increased to 33,000 cfs (June 14) as the Gavins Point pool increased after additional rain, and in order to bring the reservoir back down to its normal operating level."

"The increase to 33,000 cfs would probably have had little effect on tern and plover nesting in itself," Swenson said. "However, the widespread rain also increased flows on the James River from 6,000 cfs to 22,000 cfs, which did flood many nests on the river.

"The increased flows of up to 34,000 cfs, will likely not have much additional impact," on the terns and plover, Swenson said.

Survey crews are continuing to assess the impacts to the terns and plovers.

"The previous highest flows below Gavins Point Dam occurred in November 1997 when an average 70,000 cfs was released from the dam," according to Corps records. "Inflows from the downstream tributaries would have been negligible in November. The high releases out of Gavins Point were done to evacuate water out of the three upper reservoirs, Fort Peck Lake, MT Lake Sakakawea ND and Lake Oahe ND and SD."