On October 18, 2026, the San Luis Obispo County live gauge at Lopez Dam showed the reservoir at 78.2% of capacity. That is 38,693.8 acre-feet, with the water surface at an elevation of 510.04 feet. The county lists the reservoir's full capacity at 49,476 acre-feet.
Meanwhile, the summer anchor up the road has closed for the season. Mustang Waterpark says it is closed until May 2027, and its next season runs May 29 through September 6, 2027. So the slides are closed, but the lake itself goes into winter close to where it stood a year ago. That makes the off-season at Lopez worth planning for. You just need to know which of this year's rules apply to you.
The Gauge Reading, Set Against Recent Years
On its own, a percentage doesn't tell you much. Here is how this October compares with recent highs and lows, using the county's records and local news reports.
| Point in time | Lopez Reservoir storage | Source |
|---|---|---|
| May 2022 | 13,579 acre-feet, 27.6% | County Zone 3 operations report |
| 2022 drought low | Around 10,000 acre-feet | KSBY |
| March 23, 2023 | 100%, spilling for the first time since 1998 | KEYT |
| April to June 16, 2024 | Spill totaling 2,693.66 acre-feet | County Zone 3 packet |
| October 2025 | 39,968 acre-feet, 81% | County Zone 3 operations report |
| October 18, 2026 | 38,693.8 acre-feet, 78.2% | County live gauge |
The year-over-year change is small. Between the October 2025 operations report and the October 18, 2026 gauge reading, the reservoir dropped about 1,274 acre-feet, or roughly three percentage points of capacity. Compare that with 2022. In a July 2022 county packet, Zone 3 staff projected the reservoir would hit its 10,000-acre-foot low-reservoir trigger by October 7 of that year. In KSBY's March 2023 report, the station put that drought low at "around 10,000-acre feet." Since then, the lake has spilled twice: in March 2023, as KEYT reported, and again in spring 2024. In each of the last two Octobers, it has held roughly four times the water it held at the 2022 low.
The live gauge is automated, and the county's water resources site states that its sensor data are provisional and have not been verified for accuracy. Check the gauge page on the day you go rather than relying on a number from last week.
What a Lake This Full Is Good For in November
A high lake in the off-season mostly means fishing. SLO County Parks describes fishing at Lopez as year-round. The list of species includes crappie, redear sunfish, and largemouth and smallmouth bass, which bite best in the warmer months. It also includes catfish that can top 25 pounds and can be caught at dawn and dusk all year.
The more seasonal draw is trout. The California Department of Fish and Wildlife's 2026 provisional stocking plan lists catchable rainbow trout for Lopez Lake in November and December, and again from January through May. The plan states that intended plants are not guaranteed. CDFW keeps a live fish planting schedule where actual dates are posted and can change. If you're timing a trip around fresh trout, that page is the one to check. The provisional plan only tells you which months to watch.
On land, the county's Lopez Lake page lists the Duna Vista Trail as a moderate four-mile hike to the remote Encinal campsite. It describes the recreation area as a year-round place for hiking, birdwatching, fishing and boating.
What the Off-Season Costs, as Posted
The county's fee schedule separates the off-season, October through March, from the rest of the year. The posted Lopez figures are:
- Vehicle entry: $12
- Motorized boat launch: $15
- Non-motorized boat launch: $5
- Wind, sail or foil board: $3 each
- Full-hookup camping, October to March: $56 daily, $59 weekend, $65 holiday
These are the posted rates. Confirm them when you book through the county's reservation system, since fee pages aren't always updated the moment a price changes.
The Boat Rule That Changed in January
This is the change most likely to catch someone off guard this winter, especially anyone who hasn't launched at Lopez since last year. Effective January 1, 2026, Lopez Lake and Santa Margarita Lake require a 30-day quarantine for boats with internal ballasts or ballast bags, such as wakeboard and ski boats. Bleach decontamination is no longer accepted. The county's notice names quagga, zebra and golden mussels as the invasive species the inspections are meant to keep out.
For a ballast boat, the county describes the process like this:
- Arrive clean, drained and dry, and pass an initial inspection to receive a quarantine tag.
- Keep the boat out of the water for 30 days.
- Launch after the quarantine period with a valid tag.
- Before leaving the lake, stop at the Ranger Station for a clear tag, which lets you skip future quarantines.
The timing matters for winter plans. If you want to wakeboard on a quiet lake over the holidays and your boat hasn't been tagged at Lopez, the 30-day clock has to start well before the trip.
The notice also applies to smaller craft. All vessels, kayaks included, are barred from Lopez and Santa Margarita if they have been in an infected lake within the previous 30 days. A vessel under an active quarantine from another facility also can't launch. According to the county's alerts page, an older change still applies: since November 1, 2024, Lopez and Santa Margarita have not accepted each other's clear tags or clear tags from other lakes. A tag from one lake does not carry over to the other. Rangers can answer specific questions at 805-788-2386.
A Campground Notice for Overnight Trips
A full lake and lower off-season rates make a winter night at Lopez appealing, and the county has posted one alert for campers. Its current conditions page, updated as of 09/24/26, reports increased bear activity in campground areas. The county asks campers to:
- Store all food, trash and scented items properly
- Never leave food unattended
- Never approach or feed wildlife
- Report problem bear activity to park staff
The Lopez Lake page adds that visitors should never place themselves between a mother bear and her cubs, and it links to the county's bear safety tips. In practice, that means packing a cooler with storage in mind, since leaving it on the picnic table overnight goes against the county's guidance.
Rentals and Supplies at the Marina
If you don't own a boat, the quarantine rules don't affect you. Lopez Lake Marina rents boats, pontoons and water toys, and it serves food from a full bar. The marina's posted store hours are 7 a.m. to 6 p.m. on Sunday, 8 a.m. to 6 p.m. Monday through Thursday, 8 a.m. to 7 p.m. on Friday and 7 a.m. to 7 p.m. on Saturday. The marina notes that hours can change without notice. Call ahead at 805-489-1006 on a cold weekday before driving out for a rental.
From now until Mustang Waterpark reopens on May 29, 2027, Lopez Lake is a deep reservoir with year-round fishing, a trout window on the state's calendar, off-season camping rates and a marina that stays open.
Living near Lopez Lake is part of what Arroyo Grande homeowners get, and buyers looking at this side of the Five Cities ask about it. If you're wondering what your home is worth with the lake down the road, Campa Real Estate Group would be glad to walk you through it. Request a Free Home Valuation, and we'll put together a clear, local picture of where your home stands this season.
