I would love to see an estimate for 2021 from NPS. Based on my VERY nonacademic observations, I think this year might be a record year at the lake. Boat sales are through the roof (used and new), a quick search for available vrbo's in page this year show that many are booked through the summer already, houseboat rentals for the year have been sold out for months, etc. Covid has driven us outdoors, and with a lot of people with extra cash, are looking to use their new toys at the most epic watersports lake in the western US. Add in the low water and one main channel and I think it will feel like a zoo depending on where you go. Maybe this is the year to head uplake...I agree that in a general sense, low water levels are no impediment to having fun at the lake. In fact, in a lot ways, I like the low levels, because I think it makes some of the side canyons a lot more interesting to see on foot. I also think for every whale that emerges, another hazard becomes manageable. For every beach that goes high and dry, another one emerges. And so it goes...
But what I like most about low water levels is that they tend to scare off visitors. The NPS data pretty much confirms the correlation, with a little lag time after the peaks, and with a big asterisk in recent years because of publicity via things like Facebook and Instagram. Here's the arc of recent attendance history relative to lake levels:
1. From 1973-83, annual visitation hovered just below 2 million +/-, but after the lake hit that stretch after filling in 1980 (and especially after the huge peak in 1983), visitation climbed steadily, peaking at 3.5 million in 1988, and it stayed there until 1992.
2. By the early 90s the lake had been steadily dropping for a few years, sliding back from 1988-92. And once that downward trend became news by 1992, attendance began to fall, bottoming out in 1998 at 2.4 million.
3. In the late 90s, the lake was on a steady rise again, especially from 1995-99, and so attendance started rising again after that trend was clear. In 1999-2000 attendance was up to about 2.5-2.6 million.
4. Then came the big lake level drop of 2000-04. And so attendance dropped below 2 million in 2003 and stayed there until 2009. But with the lake again on the rise (and peaking in 2011), attendance shot up again, and after a slight lull in 2012-13, was up to 3 million in 2016.
5. Now, in very recent years (say since 2010), the other big influence on visitation I think is the online craziness through various promotions, plus Facebook and Instagram, and all kinds of things that draw visitors like gnats to the lantern. And so there was a visitation all-time high of 4.5 million in 2017. But since then, attendance is down a bit, and probably because of the unstable lake levels. It was 4.3 million in 2019. But I think the base visitation will continue to rise because of over-publicity through online platforms, so I'd expect a new peak explosion of visitors the year after an upward trend in the lake level is recognized ... just a hunch...