LADWP maps underground topography of Owens Lake
Last weekend, Los Angeles Department of Water and Power (LADWP) hydrologists used airborne electromagnetic surveying in a pilot study to map the underground topography of Owens Lake. The intent of the study is to better understand the groundwater in the aquifer beneath the lakebed, some of which the LADWP may extract to use for dust mitigation purposes.
“We want to be able to maintain the habitat value at Owens Lake, conserve water, and determine the potential for using groundwater under Owens Lake to supply water [to mitigation],” explained Eastern Sierra Hydrologist and Project Manager Dr. Saeed Jorat.
Dr. Jorat said the study would “help us learn more about the aquifer under the ground; how much we can pump safely without affecting the wetlands, vegetation, and non-LADWP water users.”
In the past, said LADWP Spokesperson Amanda Parsons, the LADWP drilled a series of test holes up to 1,500 feet deep and up to several miles apart, taking samples from the holes and testing them to infer what lies beneath the surface of Owens Lake.
Parsons said this year’s study instead employed measuring equipment “resembling a webbed oval dangling 100 feet below a helicopter,” which sent radio signals 900 feet into the ground every nine feet, then measured the returned signal to determine the geological materials below.
The study will allow the LADWP to map bedrock, fault lines, and groundwater, the latter of which hydrologists can deduce depending on the composition of the ground. Water more easily penetrates sand or gravel than clay or rock, for instance; the measuring equipment maps these different materials.
“The main advantage of this new study is going to be the speed of data collection,” Dr. Jorat said. “This way, it took us two days, Saturday and Sunday … The traditional method took months.”
Dr. Jorat also noted that using a helicopter to send radio signals into the ground was much less disruptive to the Owens Lake habitat than drilling test holes.
Inyo County Water Department Director Dr. Bob Harrington noted that LADWP’s proposal to use groundwater in its dust mitigation effort is not without controversy. That’s because the LADWP contends that groundwater, if used for dust mitigation, should be exempt from the requirements of the LA/Inyo Long-Term Water Agreement. Inyo County disagrees.
This is further complicated by the fact that land under Owens Lake is owned by the State Lands Commission (SLC), not the LADWP. LADWP would have to acquire leases from the SLC before pumping any groundwater. Should it acquire those leases, LADWP’s groundwater extraction might also soon be subject to California’s 2014 Sustainable Groundwater Management Act.
But Dr. Harrington said that through the OLMP planning process, “we seem to be moving toward a sustainable groundwater management plan,” and that Inyo County feels that with that management plan in place, “we could dispose of the disagreement over whether the Long-Term Water Agreement applies to groundwater under Owens Lake.”
In other Owens Lake news, on July 22 the Great Basin Unified Air Pollution Control District (Great Basin) Hearing Board granted the LADWP a variance to initiate a late ramp-up of shallow flooding at Owens Lake.
The variance will allow the LADWP to push back the timeline for shallow flooding on 1.12 square miles from October 16 to December 1, and on 13.67 square miles from October 16 to January 16.
These square miles were selected because they typically don’t become emissive until spring.
“Both Great Basin and the LADWP staff agreed that they could delay some shallow flooding in these areas, and that it was unlikely it would result in an air quality violation,” said Dr. Harrington.
The LADWP’s variance request was unusual, said Great Basin Air Pollution Control Officer Phill Kiddoo. Typically Great Basin receives variance requests when equipment breaks, resulting in dust emissions. Variances are granted because those circumstances are “beyond [a variant applicant’s] reasonable control.”
Kiddoo said that the LADWP argued the drought was beyond its reasonable control, therefore it too should be granted a variance.
“I came back and told them that the drought was not enough of a reason for a variance, because they still exported 42,000 acre-feet from the Owens Valley to Los Angeles,” he said. “They can’t do that and say the effect of the drought on dust mitigation at Owens Lake was beyond their reasonable control.”
According to Kiddoo, the late ramp-up will save a maximum of about 7,400 acre feet of water, although “at this point the LADWP doesn’t know how much water they’ll have to put out [on the Lake] for habitat.” Some water will go to deeper ponds during the fall bird migration, he said.
