Low oxygen levels, high temperatures and high turpidity levels in the Lower Owens River proved fatal for several hundred fish. Photo courtesy Lone Pine Paiute Shoshone Environmental Department
Dead fish in the Lower Owens River are being chalked up to heavy runoff from seasonal rain storms in the Eastern Sierra, which went charging down the natural river channel from the Alabama Gates spillway.
The result was low dissolved oxygen and high turbidity levels in the Lower Owens, both proving lethal to the warm-water fishery.
From July 21-27, water was diverted into the Owens River while repairs were being done to the Aqueduct south of the Alabama Gates. According to Los Angeles Department of Water and Power Public Information Officer Chris Plakos, the flow to the Aqueduct was cranked down at the intake below the Tinnemah Reservoir. âA little bitâ of flow continued into the Aqueduct and was diverted at the spillway.
Then the rains came.
During the isolated, heavy downpours that started Sunday, July 21 and continued through Monday, the runoff from the Eastern Sierra ended up in the river, roiling up organic matter from the river bed.
April Zrelak, air quality coordinator for the Lone Pine Paiute Shoshone Environmental Department, said the water was the color of chocolate on Thursday, July 25. The following day, she ânoticed an intense hydrogen sulfide smell and higher water levels.â Dead and distressed fish and crayfish were seen that day when Zrelak and Water Quality Coordinator Matt Hays went out to do water quality testing.
Monday, July 29, Hays and Larry Freilich with the Inyo County Water Department counted 366 dead fish on the eastern shore of the pond above the river pumpback station. The following day, a total of 740 dead fish was counted.
Tests taken at the Lone Pine Narrow Gauge Road on Friday, July 26 showed a dissolved oxygen level of 0.39 (.39 milligrams of oxygen to 1 liter of water). According to Freilich, a reading of 1.5 is considered low, but âfish can survive at those levels.â
The levels varied over the next few days, rising to 0.78 at the Narrow Gauge bridge on July 29.
Oxygen levels above the spillway were low, but not lethal, said Freilich. At the Manzanar/Reward Road bridge, a reading of 1.27 was recorded on Monday with 1.46 recorded that same day at the Reinhackle measuring station.
According to Freilich, the heavy flows stirred up sediment off the river bed. âThose microorganisms use up the oxygen in the water,â he said, a situation that was exacerbated by hot summer temperatures.
According to Freilich, fish in the river channel itself could find refuge from the poor conditions while those in the ponds could not. The die-off was predominantly adult bluegill, bass and carp, he said. Catfish and juvenile fish fared better.
By this past Monday, Aug. 5, Freilich said, the oxygen level was rising and the water, recovering.
DWP Manager of Watershed Resources Brian Tillemans responded to concerns expressed at Tuesdayâs Inyo County Board of Supervisors meeting. He said DWPâs priority was to keep the flows low enough during the repair work to, first, not damage the channel and, second, to keep workers safe. The flow was supposed to be no more than 5 cubic feet per second, he said.
DWP conducts seasonal flushing flows down the river channel in the spring to simulate natural runoff. Those increased flows, according to Tillemans, are much cooler and less harmful to the fish.
Bob Harrington, county Water Department head, told the Supervisors that 470 acre-feet of water were released into the river channel by DWP as a result of the extra runoff created by the storms. âA lot more than 470 acre-feet came downâ from the hills, Harrington said, âand DWP did its best to distribute that water,â including giving extra water to lessees where it could.
Supervisor Rick Pucci and Ag Commissioner Nate Reade, who noted increased mosquito activity in Lone Pine, both noted that advanced warning from DWP would have been appropriate. âA courtesy notification would allow staff to be better prepared and even be able to answer questions from the public,â Pucci said.
âThere are lessons to be learned here,â said Supervisor Linda Arcularius, âbut it sounds like Mother Nature had a role here that all the planning in the world might not have anticipated.â
In a phone interview earlier this week, Freilich indicated that seasonally high temperatures and the prevalence of summer storms and flash flooding in the Eastern Sierra during summer months created a âperfect stormâ â which could have been anticipated.