Where's My Dam*ed River? Oh, Excuse Me, Where's the River Dam?

There's supposed to be a river here. Right there flowing under the bridge where I was standing. And not a little river, it's supposed to be the Tuolumne River, the big watercourse that drains most of Yosemite National Park and provides much of the water used in the Bay Area and in Central Valley irrigation.

It's not really a mystery where the river is. If you've been following this blog, you'd know that a few weeks back I wrote about the removal of Dennett Dam, a dangerous eyesore that has bedeviled river planners for decades. The Tuolumne River Trust spearheaded the effort, raising more than a million dollars to accomplish this important task. And this week when I looked over the edge of the Ninth Street Bridge, the dam was pretty much gone. You can see the scene as it was on August 8 in the picture below...

The construction company that is performing the removal work needed to divert the river for the duration of the project, so they constructed a temporary levee on the north side of the river. The river is at an extremely low level due of course to the season, and the locking up of water in Don Pedro Reservoir many miles upstream.

The picture below shows the water returning to the normal channel.

There is an interesting phenomena visible at the moment for those who have ever had trouble visualizing the idea of a groundwater table. The river flows over unconsolidated sediments, so much of the river water is actually underground. Damming and diverting the visible flow of the river does not block the movement of groundwater, so as the construction company digs away at the foundations of the dam, groundwater is constantly seeping through to the surface and ponding in the excavation. The company of course knew this would happen so they installed pumps and hoses on the site to put the water back in the river.

The flow of the groundwater was rather robust, as can be seen below.

The dam removal should be complete in a few weeks (I'm sure I'll find time to do some kind of update), and the Tuolumne River will be changed, not just here, but for some thirty miles upstream. One of the most damaging aspects of the old dam (beside the fact that it killed a number of people) is that it constricted the flow of the river at a critical spot where young salmon were forced into a narrow channel where predators could pick them off easily. With the constriction gone, more salmon may survive, and that should lead to a cascade of positive environmental changes on the river.

Damned if You Do Dam, Damned if You...Well, Don't Dam: The Days of Dennett Dam are Done

One does not usually equate the city of Modesto with dams and reservoirs. It's true there is a Modesto Reservoir, but it is fifteen miles east of the city. But there is a dam in the city limits, and it has been a problem and an eyesore for decades. Back in 1933 someone had the bright idea of building a small dam on the Tuolumne River by the 9th Street bridge and constructing a nice park built around boating and swimming. Dennett Dam was built, and it lasted an entire seven years before being mostly destroyed by flooding. The park never materialized, and the remains of the dam lay abandoned. At some point, someone thought it would be a good idea to cut an opening in the dam to allow fish to surmount the structure and swim upstream (the Tuolumne is a salmon river).

The unintended consequences mounted. The opening set up unpredictable whirlpools in the river current, and at least three people have been trapped and drowned nearby. The structure impeded flows of the river and during low water, vast amounts of the invasive weed River Hyacinth would accumulate, blocking the migration of fish, and crowding out native vegetation. And the fish, which the opening was meant to help, were devastated by predators, especially introduced bass. The newly born fish were forced to utilize the narrow opening, and were easy marks for the predator fish waiting in the deep pools beyond.

Dennett Dam during a bad River Hyacinth year. Picture courtesy of Patrick Koepele of the Tuolumne River Trust

What was to be done? No one wanted to own the dam or be responsible for the problems it was causing. The city of Modesto set aside some funds around 2006, but unexpectedly high costs torpedoed the project. In 2010, the Tuolumne River Trust got involved and began to organizing fundraising efforts, both from individual contributions and grants from the State Lands Commission, California Department of Fish and Wildlife, California Department of Water Resources, USA Fish and Wildlife Service, and local agencies. Ultimately, $1.6 million was raised and work has begun. It's sort of a complicated process.

For one, they need to move the river out of the way, so the construction firm (Innovative Construction Solutions) has cut a temporary channel around the dam. It will be filled in when the dam is removed. The deep pools below the dam will need to be filled in.

When the project is completed, a major impediment to the migration of salmon will have been removed, and some 37 river miles will become more available for spawning. The land around the dam is slated for park improvement, although much or most of the "development" will consist of rebuilding the riparian habitat that had been disrupted by agricultural and industrial development. The river can become the treasure it has always had the potential to be.

If you want to see the progress over the next few weeks (or months?), it's easy to find. The dam is almost under the 9th Street Bridge in south Modesto. There is a pedestrian sidewalk on the bridge, so just park nearby and walk out.

Note: I stole the pun that I used in the title. Years ago my dad was working on a paper that he ended up titling "Damned if you do Dam, Damned if you don't Dam". I've always appreciated it.

Liveblogging the Deluge: Following Up on the Dry Creek Flood

Dry Creek in Modesto flooded to the greatest extent in two decades yesterday, with peak flows exceeding 6,000 cubic feet per second. I was out documenting the flood surge, and I managed to get to the Dry Creek Trailhead ahead of the high water around 4:30 or so. The water was rising but as you can see in the picture above, it had not breached the small levee that kept the river in the channel. I know from other reports that the flood hit a short time after I left.

I was out early this morning, and though the peak of the flood had passed hours earlier, the flow was still high, about 4,000 cubic feet per second, and there was a lot of water covering the flood plain. It was an impressive sight.

Now that the flows in Dry Creek are receding, the dam operators at Don Pedro Reservoir will probably start ramping up their releases from the lake. The goal is to keep flows in Modesto to 9,000 cfs or less to prevent flood damage. The reservoir has been accumulating water with inflows around a high of almost 45,000 cfs to the current 26,000 cfs. The lake stands at 812 feet, or 1,805,600 acre-feet, and has risen 26 feet since the beginning of the storm sequence. Since the lake will fill at 830 feet (2,030,000 acre-feet), it is now at 89% of capacity, and more than 130% of average for this time of year. They will need to free up more space for additional storms and spring runoff

Liveblogging the Deluge: "Dry" Creek Takes Center Stage Today

Dry Creek in December of 2016 before the current storms

 What happens when a small insubstantial creek that is dry for much of the year...

...gets hit with a flash flood amounting to 6,100 cubic feet per second? Let's find out!

Dry Creek at about 1,000 cubic feet per second on January 9, 2017

Dry Creek (one of many such "Dry Creeks" in California and elsewhere) is a "minor" tributary to the Tuolumne River that has its headwaters in the lower parts of the Mother Lode northeast of Modesto Reservoir. It actually isn't dry as much as the name might suggest because irrigation overflow keeps some water in the channel during the dry season. But it has no dams or reservoirs to control flows, so it has a history of sudden flashfloods during intense storms. I've been here in Modesto for nearly thirty years, and I've seen several events that resulted in flows of 3,000 cubic feet or so, but only once have I seen flows that approached that which took place today. It was in 1997 during some of the worst flooding ever experienced in Northern California. The opening scene in the video that I posted the other day about the 1997 floods shows Dry Creek in Waterford at that time. Compare that scene with the picture below.

Oakdale-Waterford Highway at high water on January 11, around 6,000 cubic feet per second.

There is only one stream gage on Dry Creek, and it is located downstream in Modesto at the Claus Road Bridge. The peak flow was predicted for around 5 or 6 PM, which meant the surge in Waterford upstream would be several hours earlier. I took these first pictures at the Oakdale-Waterford Highway Bridge at about 2 PM, and the river was indeed very high. Compare to the flow on December 9 in the picture above. The entire floodplain was covered by several feet of water.

A few hours later I headed downstream to see if I could get ahead of the flood crest, and I found high water at the Church Street Bridge north of Empire. The view was astounding. In the picture above one can see how entire orchards are under water. And it wasn't standing water, either. The entire channel was flowing rapidly downstream.

I then went just a few miles west to the Claus Road Bridge, and found that the highest flows had not yet arrived! The Dry Creek Trail had been closed because some portions were already under water, and the creek was expected to rise another couple of feet. I walked down to the river edge and found a sheriff's deputy and a crew from the office of emergency services who were using a drone to take video of the coming flood. Modesto friends: let me know if you see the videos posted anywhere!

It started raining again, and it was getting darker, so I headed east again to check out some of the other bridges.

Wellsford Road bridge was the most interesting. The main channel was moving fast, and the muddy water reminded me of running the Colorado River through the Grand Canyon a few years back. Not because of any canyon walls, of course, but because of the surging muddy water with eddies and whirlpools. The flows weren't all that much different; Dry Creek was at 6,000 cfs, and most of the time the Colorado was running at about 15,000 cfs. The big difference is that the Colorado flows at that rate more or less the entire year, and Dry Creek does it once in a generation! I found a bit of information somewhere (source has been forgotten) that suggested that about once every 500 years a flood on Dry Creek could exceed 18,500 cubic feet per second. It would be something to see something like that happen, but such a flood would do incredible damage, and I wouldn't wish such a thing on anyone.

The morning will tell if there has been any serious damage downstream. The dangers of flooding are well-known today, but a number of very nice homes were built decades ago along the lower reaches of Dry Creek near the confluence with the Tuolumne. The dam operators at Don Pedro Reservior work very hard to modulate flows of the Tuolumne River to prevent the combined flows of the two rivers from exceeding 9,000 cubic feet per second. If flows go any higher, water backs up in Dry Creek, causing flooding in the neighborhoods there.

I head to work before sunrise, but I'll probably try to catch a few more photographs in the morning. It will take a day or so for flows to recede.

What is Lagtime, and Why Should You Care? Checking out Dry Creek

Dry Creek at 9AM this morning, just a few cubic feet per second

I wonder how many Dry Creeks there are in the country? I know of two of them within a thirty mile radius of my home, including this one just two miles to the north. The name itself imposes a sort of insignificance to the waterway. The Dry Creek of my town could not be mistaken for an important river. Instead of having headwaters in the high country of glaciers and granite like the nearby Tuolumne and Merced Rivers, it begins in the Sierra Nevada foothills in dry gullies west of Highway 49. It has no natural source of flow other than rainfall. It does run for much of the year due to of irrigation overflow from agricultural fields upstream. But it could never be mistaken for a major waterway.

Except during intense storms...

Dry Creek is one of the few waterways in the Sierra Nevada with no reservoirs or flood control measures. When big storms roll through, the water can rise quickly and overflow its banks. We had such a storm last night. Rain throughout California from Eureka to San Diego. I saw that some coastal areas received 7" or more. Less rain fell in the arid Central Valley, with about 0.70" in Modesto and 1.21" in the rain gauge in my backyard. But several inches fell upstream in the Dry Creek drainage, and I expected to see some high water today. I headed out this morning for a look and...nothing. I was briefly surprised, but then I remembered that I teach about this stuff. It's a perfect example of flood lagtime. Should you care? Yes, if you live anywhere near a river.

Dry Creek at 2,000 cubic feet per second this afternoon.

Rain doesn't fall into rivers, at least not much of it. If falls all over the landscape. In gently sloping landscapes like the Sierra Nevada foothills, it takes time for water to gather into rills and small channels so there is a delay in the rise of the river downstream. That's what lagtime is, the difference between the height of the storm and the height of the runoff measured at some point downstream. I checked on the NOAA website for the latest predictions and could see that the river was slated to begin rapidly rising in the late afternoon, peaking about 8PM at 4,000 cubic feet per second. Sure enough, when I left Modesto about 2:00PM, the river hadn't changed, but by the time I crossed it again 10 miles to the east, the channel was full and beginning to spill over into some of the surrounding fields. It was running at about 2,000 cubic feet per second.

Dry Creek at 4,000 cubic feet per second, as expected after nightfall tonight (March, 2011)

So, how can hydrographers predict floods with such accuracy? They have been monitoring all the major streams in the country for upwards of a century, so there is a huge database to draw from. They watch the pattern of the storm as it progresses, and compare it to those of the past. They can then forecast the onset of flooding, the height of the water, and the cessation of the flood for areas downstream. The greater the lagtime, the more time people downstream have to prepare for the deluge.

Source: http://www.cnrfc.noaa.gov/graphicalRVF.php?id=DCMC1

Accurate scientific data is fundamental to the health of our society. There is not a single place in our country (and indeed the world) that is free of geological hazards. Hydrologists analyze the storm data and report to government officials who then take action to protect the populace from flooding. Seismologists analyze fault activity in hopes of minimizing the damage from major earthquakes. Volcanologists monitor the dangers of active volcanoes. Climate scientists track the effects of global warming.

In a healthy society, the politicians and government officials accept the findings of those who know the dangers best, and act accordingly. I hope that the new administration will come to understand this. If they were to deny the existence of earthquakes or volcanoes (however strange that might seem; Bobby Jindal once famously complained about "volcano monitoring"), disaster would happen. And likewise, if those in government deny global warming, then it would be like a politician predicting that the rivers won't rise, despite the massive storm upstream.

A California "Snow" Storm: A Winter Miracle in the Great Valley

People don't usually hear a great many good reasons to visit Modesto and environs. Forbes and others often put our Great Valley towns on the "worst places to live", but I think they really miss something when they do this sort of "expose". We grow most of the nation's food supply for one thing, so folks could be a little more appreciative of what we do. But it's really something else that few people are aware of, even those of us who live here. It's the magic of the season, the fact that we are a winter wonderland. The "snow" has nothing to do with precipitation, though, it has to do with millions of refugees from the snowbound northlands. They are Snow Geese. And Ross's Geese. And White-fronted and Aleutian Cackling geese. And thousands of Sandhill Cranes as well. In winter, the Great Valley becomes an American version of Africa's Serengeti Plain.

Snow Goose at the San Joaquin River National Wildlife Refuge

Hundreds of years ago, before the European invasion, the valley was home to tens of millions of migratory birds, but with settlement and development, 95% of their original grassland and river flood plain home disappeared. The birds could have been wiped out entirely, but a few visionary people worked to preserve a bit of the original valley habitat in an effort to save as many birds as possible. The result was a string of federal, state and non-profit run wildlife refuges that form a pathway down the 400 mile length of the valley. The birds will take refuge from October to March, when they begin making their way back north for breeding in the Arctic.

Aleutian Cackllng Goose (Branta hutchinsii) at the San Joaquin River National Wildlife Refuge. Several decades ago, there were only 600 of them left. Today there are around 200,000 because of conservation efforts in both Alaska and at the San Joaquin refuge (their primary winter home)

A great many people right here in the Modesto area are unaware of the Christmastime miracle that takes place each year. It's not hard to see incredible things just a short drive out of town. Only eight miles west of the biggest shopping mall in the region, on Beckwith Road, the San Joaquin River National Wildlife Refuge offers a viewing platform where one can see tens of thousands of migratory geese all at once. The best times are early in the morning and in the afternoon close to sundown. I took the video below at about 4:15 this afternoon during a short break from final exams at the college. Even with the YouTube compression, you can see tens of thousands of geese taking wing. You can hear the cacophony, but there is nothing like seeing and hearing it in person. The ground literally vibrates as the birds take to the air.


The spectacle is amazing, If you live here and you've never seen it, check it out right now! If you are from the Bay Area and are rushing to the Sierras for a ski day, take a short detour. It's worth your time. And if you are a birder, we are a winter paradise. More than 300 bird species have been documented in our area, and many of them can be seen during the winter season when the pickings are poor in other places (a lot of those disappearing birds come here!).

Want to Work at a Great Museum? The Great Valley Museum May Have a Place For You

I work in a great facility at Modesto Junior College. The recently opened Science Community Center on our west campus combines the labs and classrooms for the physical and biological sciences, a fully functional observatory, and most importantly for our community outreach, the Great Valley Museum.

The GVM has been open for a number of months now, and hundreds of children are paying visits each week on school field trips. The William Luebke Planetarium has been filling to capacity.  It's been wonderful to see the community support the museum has been getting.

There are big changes coming, too. The preparation lab and storage facility, a separate unit of the museum was recently completed, and the final jewel in the crown, the Outdoor Education Lab, has been approved, and construction will be starting soon.

Does it sound like it might be a great place to work? I think it is, and if you have the right skills, you could be the one working here. There is an opening, possible more than one, for a position as a museum office technician. This is a full time, 12 month position.

If you are interested, information about the position can be found at  https://yosemite.peopleadmin.com/postings/1685. The closing date for applications is September 1, 2015.

A Different Canada Goose, the Cackling Kind: Evolution on the Continent

Isolation brings about evolutionary change, and the Canada Goose clan has been doing some changing over the last few thousand years, especially in Hawaii, but also here in California. Today's blog is cross-posted from my new birding blog, Geotripper's California Birds.

If you've ever been accosted by a Canada Goose at the local park, pictures like these might give you the shivers. If one of them can deliver a nasty bite, just imagine what a few thousand of them can do. But take heart, these scenes are no nightmare. They aren't even Canada Geese. The birds occupying this field in the San Joaquin National Wildlife Refuge west of Modesto are Aleutian Cackling Geese (Branta hutchinsii). It's true, though, that before 2005 they were Canada Geese. Allow me to explain.

The Canada Goose lives in many environments, and in some cases particular flocks broke away and colonized different islands or territories (see yesterday's post for an extreme example). The presence or lack of food sources or differences in the nature of predators favored certain traits (size and behavior, for instance) in the young. The geese who summered on the Aleutian Islands were long recognized as a smaller subspecies of the Canada Goose, but recent DNA analysis has led researchers to consider these birds an entirely different species. And so these birds are not Canada Geese, they are the much smaller Aleutian Cackling Geese, which are genetically distinct from the Canada Goose.

The Cackling Geese winter by the tens of thousands in the wildlife refuge a few miles west of my home. It is a stunning sight to see so many of the birds in one place. From the observation deck on Beckwith Road, one can see and hear thousands of birds taking off and landing, and in general making a racket (cackling, as it were). They have been encouraged to stay here instead of nearby agricultural fields through the planting of corn and other food plants. In April they will pick up and leave, headed north to breed in the Arctic.

The refuge is also home to thousands of lesser Sandhill Cranes. We could just make out a flock of them in the far distance. Snow Geese also winter in the area. There were five of them among the thousands of Cackling Geese yesterday, looking mildly confused. They usually arrive in large numbers in late November or early December.

"George, are you SURE this is the right place? Shouldn't you have asked directions in Oregon?"

As we were standing and watching the flocks there was a tremendous BOOM, and thousands of the geese immediately took flight. A huge dust plume over to the west revealed where the explosion had come from. And why.

It was a huge net. Several dozen of the birds had been trapped and for the next few minutes we could see Fish and Wildlife employees tagging them.

As usual, the picture quality from YouTube sucks (the compression process I suppose), but you can get a sense of the cacophony of sound from the flying geese from the short video below.

A Scary Story for Halloween: Rainfall Totals in My Neck of the Woods

It's Halloween night, and a lot of children are no doubt disappointed that it is raining outside. We've had four kids in one group so far. Waiting for trick-or-treaters this evening has been a little like waiting for rainstorms in California over the last three years.

I love numbers and statistics. I've lived in the same location for the last 23 years and the first year I was there I got a nice rain gauge for Christmas. I've been using it to keep track of precipitation in my Great Valley town about 13 miles east of Modesto. We are roughly at the middle of the valley (the center of the Central Valley!), about 200 miles north of Bakersfield, and about the same distance south of Redding. The valley climate ranges from Mediterranean in the north to desert in the south (Redding averages about 34 inches of rain per year while Bakersfield averages just over 6 inches). Modesto's 108 year average is 12.15 inches. The highest recorded rainfall was 26.01 inches in 1983 with the lowest at 4.3 inches in 1913.

I now have nearly a quarter of a century of rainfall records from my backyard, so I thought I would make some comparisons with our nearby city. The average yearly rainfall in nearby Modesto since  1991 has been 13.04 inches per year, an inch higher than the long-term average. In my little town the average from 1991 to 2011 was 14.55 inches, with a high of 26.42 inches in 1998. Waterford has had higher rainfall than Modesto in 20 of the 23 years that I've measured. I am guessing this is because we are slightly higher in elevation (by a grand total of 70 feet or so), closer to the Sierra Nevada foothills, and farther from the rain shadow of the Coast Ranges.

The most rainfall I recorded in a single day was 2.32 inches on January 2, 2006, and the wettest single month was February of 1998 with 8.64 inches. Some of you in wetter climates may find these numbers amusing (I note a day in 2010 when Big Sur got 22 inches of rain...in 24 hours!). But as I've said, we live in an arid climate.  Irrigation is all that keeps most parts of it green.

The scary part of the story is that of the last decade. There were a few wet years, but six of the last eight years have been well below average, only about 75% of what was once normal. Last year was the driest I've recorded. Our reservoirs are functionally empty and there has been little or no snowpack. We actually drove over Tioga Pass in January of 2012, and it was t-shirt weather. Tioga is usually closed from November to May because of snow, but not these days.

Here's hoping that tonight's storm, as disappointing as it is for the Halloween trick-or-treaters, is a harbinger of wetter times to come. It's a frightening situation all around.

Partial Solar Eclipse from California (and What a Sunspot!)

Wow. Just wow. Yes there was a partial solar eclipse today that was visible across much of the country, and yes, it was pretty spectacular. But what caught my attention was the huge sunspot. It is the first time I've ever seen a sunspot with the naked eye, and it was incredible in the zoom lens. I'm told that it is more than 90,000 miles across, the width of 12 Earths. Sunspots are essentially gigantic solar storms. They look dark, but they are simply a bit less bright than the rest of the Sun's surface.

It was so big that even my camera was able to catch some detail. I had my camera on a tripod, and held a solar telescope filter over the end to catch these shots. The zoom was about 60x.

There was a lot of interest on campus, and so our astronomers and Astronomy Club had a number of scopes set out on the roof of the new Science Community Center. I wish I could have photographed one of the views through the most powerful scope. We could see the granules of the Sun's surface, and solar prominences, the arcing jets of plasma shooting out from the surface.

A great day!