Snowmelt is bringing the return of more flooding and even closure to Yosemite National Park

Snowmelt is bringing the return of more flooding and even closure to Yosemite National Park. 

Yosemite National Park

Sierra snowmelt underway that's going to result in flooding and Yosemite announcing their closure and we knew this was coming. This spring snow melts.

We're just hoping that it's slow going to meter down the hill. But unfortunately with these warming temperatures, we are going to see the risk of some elevated flood risks, especially in the Sierra, as we head into that flood water.

Pohono Bridge on the Merced River. This is where we're looking at the rises coming into that flood stage cresting on Sunday.

But somebody saying this could indeed last into June, they're going to be taking the look day by day as we start to charter through the snow melts coming down the hills. The good news is, that they are saying you're automatically canceled and the reservations are void at refunds are going to be iss.

The problem with Yosemite folks, for anybody that doesn't know, you have to book those places some one year in advance.

People wait in line until that moment when they can hit go to get to Yosemite. So, unfortunately, this year, just not panning out, it's not the only place that we're going to be watching those river rises.

We've got five areas of concern, most notably for California, it's going to be the Merced River but also, the Carson River that's going to be just to the South of Lake Ta, both on the California and Nevada side.

With those rises on the rivers, we're also going to see some creeks and streams and get close their banks and some low-water areas could find some water and that l makes it impassable for low-water areas, some roadways up in the high country.

So even though the snow is gone, unfortunately, the danger remains. Some of those water temperatures, think about it, and this snow melts coming down the hill is only about 50 to 60 degrees.

The farther away you get from the snowpack, say the San Joaquin River in Stockton, that's at 63 degrees. It's going to be warmer, but the closer we get to that immediate snow melt.

We're only about 35 to 50 degrees water temperature cools the body that cold water about 25 times faster than cold air.

People can get hypothermia very quickly, lose muscle control, and unfortunately this time we do have a lot of water rescues.

Some people don't make it to wear a life jacket. That's the most important thing. Life jackets save lives. Just to put this into perspective, those cold water temperatures for anybody that's been over to the Pacific in California.

And if you haven't, it's quite a shock to get in that water. Usually, people go in maybe to their toes.

Kids get in a little bit longer, but most adults will get out pretty quickly. San Francisco bar water temperature is at 55 degrees. So while rivers. Generally, the spa runs much colder than the Pacific.

We're at about 1:00 to 3:00 inches on average of melting. It is going to be dependent on a couple of factors.

Temperature isn't the number one factor for snow melt, it's access to sunlight and also the snow color. 

First, let's talk about the sun angle. We're past the vernal equinox z. At this point, the sun's rays are moving north of the equator, so by the summer solstice, the sun appears highest in the.

We have long periods of daylight and also more heat energy. Our sunlight looks different in just a matter of a month. With access to daylight today, we had 13 hours and 37 minutes of daylight in just a month.

We're going to increase that to almost exactly an extra hour. So again, more access to that sunlight. Now let's talk about dirty snow.

Compared to white snow, the albedo effect, dirty snow melts faster.

That's because it absorbs more sunlight. If you've ever had a dark shirt on in the middle of summer, you know you get pretty hot. You're advised to wear light clothing.

That's because sunlight gets reflected so. If you've got white snow, it reflects some of that sunlight and won't melt quite as fast.

At this point in the season, a lot of dirty snow melts and one thing is to look at how much wildfire activity we had over the summer.

Sometimes when we have a real fire season, even deep into the winter, we get some sloughing that remains on the trees.

Now last season we didn't have a huge fire season, but in years past. Is certainly present. And so we saw a rapid melting of snow up in the high country.

This is generally the path that we follow. We'll look at North America, well the North Middle and South American Rivers 3, and then also the Feather River.

This is just for reference, just to kind of show you okay, how does that snowmelt happen, move into our rivers and eventually make it out to sea or in the maf our canals and the aqueduct now the northern part of the state gets. 

Of the precipitation, the southern half of the state uses about 75% of the water, so it's a real balancing act for water managers. As far as the snow packet does head into again, we're just using this as a reference point for some of the rivers.

The American River has a lot of reservoirs throughout the state, though we have roughly about 1500 reservoirs.

So these are just a couple that we're looking at. 

Lake Oroville is going to be connected to the Feather River and then Folsom Lake, we hear a lot about that on the American River. Once releases start to happen water continues to head down. To the low-lying elevations. 

That is going to be the valley once it meets a connecting point.

This is the confluence of the American and the Sacramento River which s right around downtown Sacrament. You can see a lot of flooding during certain parts of the year.

That water then heads out to the delta and then sometimes heads out to. Other times this water will be connected to the canals and eventually the aqueduct. Many aqueducts are actually throughout the state and so water gets sent down South.

So it's really important to take a look at that water path. Now that particular area through the state is only at minor risk of flooding for the spring flood outlook.

However, when we get to the central and the southern part of the Sierra and particularly the San Joaquin Va, we've been talking a lot about the Tulare Basin that has a moderate risk of flooding.

Unfortunately, we've already been seeing floods throughout the winter season and it is possible.

The Northern Sierra was impressive, not necessarily the record-setter or the Central Sierra, but the Southern Sierra by all accounts has been the outlier here with just well above average as well above any.

We have very narrow canals and transportation for that water once it gets down the hill. So we take a look at the Tulare Basin 6th station index and one of the wettest years here. You can see we're running just slightly below that.

Unfortunately, we're going to continue to see the inflow of that snowmelt and we're going to have some problems continuing deep into not only this spring but very likely the early summer.

So you can see some of that snowpack up there and will head towards places like Fresno, Visalia, and through the Central Valley.

There we go into Tulare Basin. You can see it's just like this pocket that sits there primed to hold any water.

 I focused a lot on some of our bigger reservoirs.

In the northern part of the state, but I did want to take just a look at some of our central and southern reservoirs and we'll focus on the new Melonis right now, 61% of 61% full, I should say 98% of average Don Pedro doing well here, 104% of the historical average and then San Luis again 118% of the historical average.

Right now we're about 100% full. That has been seeing really dry years over the past three years.

Nice to see that come up. A lot lots of recreation and fishing over there. Millerton and Pine Flat.

Now we haven't mentioned these two a whole lot, but they are starting to come into a lot more focus now you can see considerably different Millerto.

Only 29% full right now, where is Pine? Flat, 45% full. It is a slightly bigger reservoir, but the proximity to the Central Valley is very close. And when I take a look Pat some of these graphs, look at this one from Millerton, we're getting out as much as we're getting in. 

The other reservoirs have such stark contrast up and down here, just trying to reduce it. The amount of water at Millerto, unfortunately, heads down the hill. So it's putting more water in as that quite frankly are just trying to deal with too much water at this point.

We've got some good news kind of coming down the pipeline here. And then we take a look at Pine Flat. This is a bigger reservoir, about a million-acre feet in, 10,000 cubic feet per second. Almost 13,000 cubic feet per second. Again, this is because we've got all snowpack yet up the hill and that is eventually going to melt.

Now when are we going to see Does the highest river Flow? Well, for the San Joaquin and the Kings, not until June. Those are going to be more of that central and southern part of the San Joaquin Valley.

So, unfortunately, we're still going to have to look at all of this continuing into our summer season. As far as our rainfall, there is a component of. That's not exactly just reliant on the snowpack and the snow melt.

It's also how much rain we have, How much was the ground saturated? And when you take a look at the totals compared to the averages were well above average.

So all places throughout Califo, minus Palm Springs, which was slightly below average everywhere coming out of the dough. And also I shouldn't say everywhere, but every place with average precipitation does a lot of drought reduction.

It's a unique situation. Usually, it follows the next, but in this case, throughout California, we are in all.

Phases happening right now. We're still preparing for all the snow to head down the hill and the possibility of more flooding happening.

So there is financial help we're getting both from the state and the feel government and not all of it is in place. So there are a lot of folks that still wondering how am I going to get recovery efforts going in the financial as well as the struct.

Now we have challenges and opportunities.

Certainly, the challenges are going to be tracking that rapid snow. But the opportunities are the groundwater recharge. What's happening in the Department of Water Resources is working with community partners, and local agencies to say, OK, let's just hold off on the permitting process.

It's the water underneath our feet, we have been over-pumping that and so the ground has been used because we reduced that layer. If you look at it kind of like a sponge, we reduced that moist layer, that water layer.

So the sponge is compacted once we're able to recharge that ground. Starts to come back up a little bit and we have more groundwater in the drought year use a kind of as our savings account.

So when we don't get the surface water from our reservoirs, we can pump that water to the surface.

Especially for many of our age partners that need that water, we can get that going. Some residents use that too for their drinking. The bathing of all water uses groundwater is a huge issue right now.

The Sustainable Groundwater Management Act is trying to bring in line. A sustainable plan for all water basins to get their groundwater because we have over-pumped for Deca, for almost a century now.

And so we've got huge issues with our groundwater and the lack thereof. This is going to be in the Central Valley that's the most problematic. And they're saying let's just get that groundwater going where we just pull back on some of the restrictions from the recharge efforts.

Now on the other side of things, this is going to be a temporary situation where we see unusually warm weather. We're likely going to be in a cooler scenario that's going to put less pressure on me, a lot of the heat melts the snow and access to the sunlight, and we have a likely wetter scenario.

As well, that'll be the first week of May. So we got to get through this week first and this will be an on-and-off situation that we're dealing with our overall pattern.

We start to see the precipitation dwindling, especially by the time we get to June, July, August, and even early September. We see nothing in California unless we get the monsoonal flow going that will bring up some of those showers into the higher elevations.

And our temperatures conversely are on their way up. So that's why we see this spring snow melt, so much of A concern. We're going to be near record.

In the Central Valley, parts of the Sacramento Valley l be right around record territory well as the northern San Joaquin Valley for Stockton and Modesto.

Highs will be right around the low 90s, with records in the mid-90s. There's the culprit, high-pressure Ridge thinking, warming air. And as we dig deeper into the weekend, we'll start tracking that load just off the coast. That's what will give us that shift in our weather pattern and you'll see it.

In our 10-day forecast, we'll have a slight chance of showers coming in for some areas next week. Highs will cool to near 70. We'll keep tracking the flood situation in California.