Guest Blogger: Michael Vorhis, author of ARCHANGEL suspense thriller, OPEN DISTANCE adventure thriller & more to come

For anyone planning a trip to Yosemite Valley in springtime, as I wrote sometime back the place is truly heaven on earth. There’s no flow regulation (no dams) in or above Yosemite streams, for one thing—it’s all natural runoff and snow melt. It’s a joy to need to be connected to Nature’s seasons in that way, but at the same time it takes some savvy, and a little prior data, to fish there. There are numerous fly fishing water options, including the Merced running through the valley, and Tenaya Creek, and Yosemite Creek, and Crane Creek down in the Foresta basin…and none of that even considers the high country (which won’t be accessible in the spring anyway).

Fishing season begins the fourth Saturday of April each year; do your best to delay those family Spring Break trips until you can legally cast a line. That’s what I did this year; I got out at 5am on the second day of the season and had the Merced to myself…for all the good it did me.

I found it rough going. I’d been monitoring snow melt rates and stream flows, but really had little means of reconciling CFM numbers to any idea whether I could safely get in the water. A person really needs a visual. So this article is a mostly-photographic data point that might help you identify what a given flow rate looks like. Hey, a one-weekend data point is better than none at all.

When I was there, the Merced was running in the 3200-4000 CFS range. Note that the snow pack is huge this year (2017), so try to think in flow rates rather than dates on a calendar page, because these conditions in other years will happen, but perhaps not in late April. For the flow rates I saw, I have photos and a bit of observational lore for the Valley stretch of the Merced, for Tenaya Creek, and for Yosemite Creek. A guide I spoke with was bringing a class of beginners down along Crane Creek, but I think it’s because that stream is so narrow it’s all bank fishing.

In the Valley, all streams feed into the Merced, so a Merced gauge will also give hints as to what the creeks are likely to resemble. The below useful link gives both CFS and height at the Pohono Bridge:

When I was there most recently, the gauge reading showed this:

Notice that the flow rate goes DOWN in the afternoon. This is counter-intuitive, since in most snow-fed streams the late afternoon is when the day’s peak melt finally arrives in the stream. In Yosemite it seems to take so long for melt on the peaks to hit the streams that it arrives next morning. That was a source of disappointment for me since I’d scouted my chosen wade-in point the afternoon before, only to find it much too deep to cross at 5am. The difference was easily 6-8 inches. As a result I was stuck with flicking my line out between trees and letting it drift right past my boots. Not a very classic experience…but ya live and learn.

And late April isn’t the worst of it. A week later the Merced flow had doubled to 7000 in the mornings (dropping to 6400 in afternoons). Depending on the Hig Sierra snowpack, the flow can rise and remain high into June. And the high country streams and lakes don’t open until Memorial Day or later.

The simplified take-away is that Yosemite National Park may be best thought of as a mid-summer-and-later set of fisheries. Of course savvy locals and guides always have their secret stretches, and there’s downstream water outside the park that’s generally fishable in spring, but in the park itself the bulk of water easily accessible as part of a family trip can be a challenge, especially if wading is the goal.

NOTE FROM J STOCKARD: Over the next week or so, we’ll publish parts II, III and IV of this post from Mike Vorhis.


    1. Glad you liked the imagery Alfred. Yosemite Valley quite literally takes a person’s breath away. I was married there, I’ve jumped off Glacier Point in a hang glider more times than I can count, and I love every breath I take in that valley. I often tell visitors: “California is blessed with easy access to incredible places. The three best things about living in California are Yosemite, Hawaii, and Yosemite.”

      I agree that the High Country is a whole other, equally amazing, world. I’ll try to do justice to it in a future article.

      The next three installments of this four-part “Valley watersheds” article each have more images I hope you like. Do let me know which are your favorites!

      – Mike

  1. Mike,

    Nice pics. Re: “In Yosemite it seems to take so long for melt on the peaks to hit the streams that it arrives next morning…”. The cyclic nature of flow rates in a river can be especially perplexing, especially in the Spring runoff periods. Even streams more impacted by storm water rather that snowpack can be difficult to decipher. Although I don’t think there’s any precise mathematically way to describe what happens, there are really three variables (for snowpack melt) that come into play. First is the upper most elevations that are reached by melting temperatures and how long those temperatures persist on any given day. Second is the distance from that melt point to the points on the stream you are observing. The third is the average gradient of the watershed from the melt point to the point on the stream you are observing. When the impact is from storm water, the volume of precipitation and distance come into play as well.

    Every watershed is somewhat different. In the Paradise Valley, the Yellowstone is impacted by snowmelt (and heavy precipitation) in the Lamar Valley. When the Lamar rises, it takes about 24 hours to that water to reach the middle of the Paradise Valley. One of the major tributaries of the Yellowstone, the Gardner, has a relatively short watershed, but very steep gradient. Increased flows at the head waters take less than 4 hours to reach the mouth. By contrast, the Firehole has one of the more predictable (from snowmelt) flow regimes. It has a relatively low gradient over its entire length and although the total watershed is large, there is no major points of elevation that would hold a lot of snowpack. When snowmelt peaks during daytime high temps, low temps at night stop it. The melt reaches the main parts of the river about dawn and by the end of the day, the river flows reach the low point in the cycle. Absent any significant rainfall, it is probably one of the most regular cycles I have ever seen.

    This is one area where local knowledge and experience pays off. Knowing how a river typically behaves during runoff or storm cycles is an important part of angling.

    Mike Cline
    Bozeman, Montana

    1. I bet myself a nickel that you’d weigh in on the snow-melt arrival topic Mike, and I’m glad you did. It pretty much has to be different for each watershed. The three elements that dictate water migration that you listed are the ones that matter. I guess in addition to average gradient there’s also absorption properties of higher valleys that are traversed…you could break it down in a number of ways but it all translates to: (1) How much water is launched up high, (2) when it’s launched and/or over what duration, and (3) how long it takes to make its run to the river or stream we’re fishing.

      In June, when the natural runoff starts to subside, the Carson River in northeastern California (which has no dams on it) sees higher flows in mid-afternoon…which means about a 24-hour delay. Kayakers leverage that CFM bump when rapids get “bony” and they need the water to get through the more technical drops. (Rafters track it even more carefully, since kayaks don’t ‘pop’ but rubber buses do.) Timing one’s descent in that gorge is thus a little like what an Acapulco diver must do when leaping off the famous cliff–arrange to enter the water as a wave is passing through.

      Having never felt the need to observe and track it, and considering the steepness of the gradient of the feeder streams, I expected Merced water in Yosemite Valley to behave similarly to the Carson. But the delay appears to be much longer. I think the parameter I misunderstood was which slopes are melting and feeding the watershed, and (gradient notwithstanding) how much the torturous path from high country to the Valley must impede water flow rate. There are probably storage features (Tenaya Lake up high, for example) that slow down the water. Instead of about 24 hours it looks to be more like 38 hours…and it might also be different in June than in April.

      In future I’ll dispense with assumptions and go with my past observations, and with current gauge trends. More accurate! 🙂

      Thanks again for your thoughts on this Mike. It can be a lost art, since it’s getting harder and harder to find rivers whose flow is not ‘artificialized’ by upstream dams. Almost everything is a tailwater anymore, for most of us. We need to work hard to hang onto the the old skills, the understanding, of Nature cycles.

      – Mike

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