On March 8, the Inyo County Board of Supervisors proclaimed a local state of emergency as a result of the early 2023 atmospheric river events and projected spring runoff conditions.
The declaration stated, in part: “… 2023 storms and runoff conditions threaten the safety of property and persons in Inyo County by flooding private, Tribal, and public property; damaging or destroying infrastructure including roads, bridges, water conveyance and diversion structures, dust control apparatus, sanitary facilities, and campgrounds; creating conditions that propagate mosquitoes and other vectors that harbor disease and threaten public health; and, posing long-term environmental threats associated with the spread of invasive species …”
The County of Mono and the Town of Mammoth Lakes made similar declarations on March 8 due to the massive amount of snow burying homes and businesses. A Unified Command was immediately formed to organize and accelerate snow removal and runoff preparation efforts.
FREQUENTLY ASKED QUESTIONS
HOW MUCH SNOW DID THE SOUTHERN SIERRA RECEIVE DURING THE 2022-2023 WINTER AND HOW DOES THIS TRANSLATE TO RUNOFF?
The Southern Sierra Snowpack is a record 296 percent of normal, which translates into runoff that is 233 percent of normal. Snowmelt is anticipated to be 1 million acre-feet (one acre of land covered in one foot of water), or 326 billion gallons of water. This is equivalent to as much water as five Crowley Lakes spilling down from the Sierra. This excessive water will need to be managed throughout the Eastern Sierra to protect homes, businesses, and critical infrastructure such as roads, bridges, campgrounds, and the Los Angeles Aqueduct.
HOW DOES THIS COMPARE TO OTHER YEARS?
The Southern Sierra snowpack is the largest in recorded history (dating to 1946), eclipsing other severe winters and past record-holding seasons of 1982-1983 and 1969, which set a benchmark at approximately 270 percent of normal. The especially wet winter of 2017 produced a snowpack equal to 241 percent of normal with snowmelt estimated at 195% of normal.
While 1969 and 2017 can be looked to as examples of what to expect, the 2023 runoff year will be unprecedented – with runoff amounts anticipated to be more than twice what was seen during 2017 in some local waterways, including Tinnemaha Reservoir.
The City of Los Angeles spread approximately 215,000 acre-feet of excess runoff around the valley in 2017 and expects to spread 460,000 acre-feet this summer, with more than 150,000 acre-feet having to go to the Owens Lake Brine Pool.
ARE EXPECTATIONS AND STORM DAMAGE MITIGATION DIFFERENT FOR MONO COUNTY VERSUS INYO COUNTY?
In Inyo County, efforts started in late winter to prepare for the spring runoff and any associated flooding. In addition to allied agencies working individually to ensure their infrastructure is ready for fast and full waterways, proactive messaging is continued to be emphasized in the public.
Mono County, and the Town of Mammoth Lakes are working on disaster recovery (post-winter storms) with the Federal Emergency Management Agency to provide assistance and resources to those affected. The runoff will be a major concern upon the warming of local temperatures. The Mammoth Lakes Police Department has received no runoff-specific calls for service; however, camping in areas where folks shouldn’t be camping is an issue.
WHEN IS THE RUNOFF SEASON EXPECTED TO PEAK AND HOW LONG IS IT EXPECTED TO LAST?
A typical runoff season for the Owens Valley in Inyo County occurs between April and May or June. This year, with the record snowpack, runoff will be a major concern through at least July, with the peak expected around July.
HOW HAVE THE VARIOUS AGENCIES BEEN PREPARING FOR THE RUNOFF?
For months, crews with the County of Inyo, Los Angeles Department of Water and Power, and Caltrans have been busy reinforcing bypasses, clearing creeks and streams of debris, unblocking culverts, preparing areas for water spreading, and clearing ditches and other channels on the Owens Valley floor that haven’t seen water in decades. Agencies have also been staging large equipment such as excavators and backhoes at strategic areas throughout the Owens Valley to facilitate quick response to flooding. This is in addition to media campaigns warning about the dangers of local waterways and the need for homeowners to clear their irrigation ditches of any obstacles and debris.
Mono County is focused on winter storm disaster recovery. Disaster Resource Centers have been established in Mammoth Lakes and Bridgeport to support impacted individuals, families, and businesses navigate available assistance and support. Details can be accessed on the READY Mono portal: https://ready.mono.ca.gov/ .
WHAT AREAS ARE EXPECTED TO FLOOD?
Prolonged and protracted spring flooding is expected throughout the region. All waterways are running near full capacity, and we are only at the beginning of the 2023 spring runoff. Any areas where there are waterways are at risk of flooding, including highways, roads, and recreational sites like campgrounds. Yards that have creeks or streams running through them are also at risk. Officials are doing their best to anticipate when and where the snowmelt will be coming down from the Sierra and where flooding might occur, but Mother Nature is ultimately in charge.
There will be downed trees, and debris flows with rocks and boulders, that may impact campgrounds and not only delay openings but could happen intermittently throughout the summer season. Please have a backup plan if your campground reservation does not work out or the area you’re looking to camp is not available.
HAS UNIFIED COMMAND IDENTIFIED COMMUNITIES THAT WILL LIKELY BE CUT OFF FROM POPULATION CENTERS THIS SUMMER?
Efforts are underway to catalog and map specific areas of concern and establish trigger points for issuing warnings and/or evacuation orders.
WHAT CAN RESIDENTS IN THOSE COMMUNITIES DO TO PREPARE FOR IMPENDING ISOLATION?
Given the high likelihood of some communities being cut off from population centers due to flooding, it is incumbent on residents to begin building their own safety nets now, including stocking up on food, supplies, and medications.
WHAT CAN RESIDENTS AND BUSINESS OWNERS IN GENERAL DO TO PREPARE FOR THE RUNOFF?
Specifically, property owners should:
- Clear ditches of all plants, rocks, and debris;
- Clear overhanging vegetation from waterways to ensure maximum flow;
- Open pond outflow channels, and remove decorative rocks; and
- Clean all water screens, gutters, and drains; consider draining ponds or lowering levels.
It is also recommended that property owners expand their irrigation ditches, making sure they are wide and deep enough to accommodate the coming deluge of snowmelt.
WHERE CAN I FIND SANDBAGS/SAND FOR MY BUSINESS OR HOME?
Limited, free, unfilled sandbags are available at the following locations:
INYO
Bishop and Aspendell
Bishop Fire Station, 209 W. Line St., Monday through Friday from 8 a.m.-noon and 1 p.m.-5 p.m.
Sand is available at Station 2 by Manor Market and Station 3 on U.S. 395 near Astorga’s.
Big Pine
Big Pine Fire Station, 181 N. Main St., Wednesdays from 7-8:30 p.m.
Sand is available at the same location.
Independence
Independence Fire Station, 202 S. Jackson St., Wednesdays from 6-7:30 p.m.
Sand is available north of Mazourka County Road Shop, 750 S. Clay St.
Lone Pine
Lone Pine Fire Station, 130 N. Jackson St., Tuesdays from 6:30-7 p.m.
Sand Is available at the Lone Pine Sand Trap off Tuttle Creek Road.
Olancha
Olancha Fire Station, Mondays from 6-7 p.m.
Sand is available at the same location.
MONO
Benton Road Shop, 25574 Hwy. 6
Bridgeport Road Shop, 207 Jack Sawyer Rd.
Chalfant Fire Station, 215 Valley Rd.
Long Valley Fire Department, 3605 Crowley Lake Dr.
June Lake Community Center, 90W. Granite Ave.
Lee Vining, 51596 Hwy 395
Walker Road Shop, 62 Shop Rd.
Town of Mammoth Lakes, 299 Commerce Dr.
HOW IS THE OWENS VALLEY MOSQUITO CONTROL PROGRAM PREPARING FOR POSSIBLE MOSQUITO POPULATION INCREASES?
The Owens Valley Mosquito Control Program (OVMAP) has been planning for months to mitigate the impacts that runoff can have on mosquito populations. These impacts are not only nuisance issues, but also vector-borne disease concerns. As the mosquito control program ramps up efforts this year, OVMAP asks that the public helps to ensure their safety from these diseases by doing these things:
- Keeping mosquitoes outside. Screen doors and windows where possible and check their condition occasionally.
- Use Insect repellents. Insect repellents reduce the chance of being bitten and will also generally repel ticks and other biting creatures. Use and follow the label of an EPA-registered insect repellent. • Wear long-sleeved shirts and long pants for additional protection.
- Avoid being outside when mosquito activity is highest. The Culex mosquitoes that can carry West Nile Virus are mostly active at dusk and dawn, so mosquito avoidance measures are particularly valuable at those times.
OVMAP is and will continue to work with other local agencies on water management strategies to control populations as well as aggressively monitoring and treating breeding locations as they occur. OVMAP will make fogging treatments to protect populated areas as needed, but the program does not have the resources to provide full control on the 1,600-plus square miles outside of our local towns. Populations may increase significantly along the river and other areas where water-spreading activities occur. Please be cognizant of this when recreating and protect yourself from bites.
WHAT STEPS IS SOUTHERN CALIFORNIA EDISON (SCE) TAKING TO MANAGE THE RELEASE OF WATER?
SCE is anticipating increased water flows into and out of its hydro-electric reservoirs during peak runoff and does not believe these flows to pose significant dam safety risks. SCE inspects all dams regularly per state and federal guidelines, operates with restrictions on reservoir levels to meet safety and seismic requirements and has completed improvements to manage the release of excess water and reduce potential downstream impacts.
SCE has reduced water levels to effectively manage capacity and the flow of projected natural snowmelt runoff by draining excess water through its powerhouses, large pipes, and relief valves, and has reviewed and amended its Emergency Action Plan (EAP) in consultation with local emergency managers. SCE will provide updates regarding the timing of any needed water releases to notify downstream entities and appropriate emergency management officials if/when these EAPs are activated. SCE encourages customers to prepare emergency plans for their homes and businesses and to consult existing County notification systems in the event of a local emergency.
HOW WILL THE EXCESSIVE SNOWPACK AND SNOWMELT IMPACT RECREATION – BOTH AT LOWER ELEVATIONS AND IN THE MOUNTAINS?
The public is strongly encouraged to avoid waterways this summer with the exception of Diaz Lake, Millpond, and Buckley Ponds. Swift, high-flowing water could lead to potentially hazardous conditions, especially near the Owens River where sections of the bank are severely undercut and eroding quickly. LADWP has closed access to the river between East Line Street and Warm Springs Road, isolating the popular swimming hole known as “The Ropes and High Banks.”
Chalk Bluff Road is currently closed but the LADWP is allowing foot traffic on its land to access the Sad/Happy boulders.
Many high-elevation lakes are still inaccessible. Avalanche danger is moderate; with the warming temperatures, wet loose slides are a concern. Be cautious around rocky outcroppings and when alpine temperatures don’t allow for refreezing at night.
The recreating public is strongly encouraged to obey all road and other closures, which have been implemented for public safety. Emergency response resources are limited and will need to be focused on the potential hazards anticipated this spring and summer.
Users are reminded that recreating downstream of a dam presents certain hazards. Although the increased flows are not believed to pose significant dam safety risks, this year’s snowpack is expected to bring increased high flows of cold water. Water levels can change without notice and create treacherous currents. Be aware of rising, swift and cold water.
HOW WILL THE RECORD SNOWPACK AFFECT THE LOS ANGELES DEPARTMENT OF WATER AND POWER’S DELIVERY OF WATER TO LOS ANGELES?
Currently, approximately 130 billion gallons of water is expected to make its way to Los Angeles this spring and summer via the Los Angeles Aqueduct – potentially enough to meet up to 80% of the city’s water demand for a year or more, or enough to supply water to more than 1 million households. To put things into perspective, in an average year, the Los Angeles Aqueduct typically provides about half of the city’s total water supply.
LADWP crews have lowered reservoir levels throughout its aqueduct system in order to make room for the runoff when the snow begins to melt. LADWP is also maximizing the benefits of the water by replenishing the groundwater table in the Owens Valley watershed as much as possible by spreading and supplying water to environmental projects in Owens Valley.
WHY NOT JUST REFILL OWENS LAKE AND KEEP IT FULL?
Excess runoff water that naturally flows to Owens Lake in extreme snow years eventually evaporates. LADWP’s priority is protecting the environment in Owens Valley while also providing a reliable source of water for the City of Los Angeles.
HOW LONG WILL IT TAKE THE EXCESS RUNOFF WATER, THAT MAKES IT TO OWENS LAKE, TO EVAPORATE?
Water is expected to evaporate from the Owens Lakebed between 12 and 18 months after the high level of flow ceases. It is important that LADWP manages the increased flow so as to not disturb the ecosystem restoration and dust mitigation measures to the greatest extent possible.
HOW CAN I FIND MORE INFORMATION, SUCH AS ROAD CLOSURES OR CAMPGROUND STATUS?
Inyo County: https://ready.inyocounty.us
Inyo County Sheriff’s Office: https://www.facebook.com/InyoCountySheriffsOffice
Los Angeles Department of Water and Power: https://ladwpeasternsierra.com/runoff2023
Mono County: https://ready.mono.ca.gov/
Caltrans: https://quickmap.dot.ca.gov/
Inyo National Forest: https://www.fs.usda.gov/inyo
Bishop BLM Field Office: https://www.blm.gov/office/bishop-field-office
Campgrounds: https://www.recreation.gov
Mosquito Abatement: https://www.inyocounty.us/services/agriculture/mosquito-abatement
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(From Eastern Sierra Unified Command)
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