SCIENCE IN SHORT: Going Ultra-Local with Delta Data: Looking Back to See the Future 

For as long as humans have been upright, we’ve been digging, logging, and building along waterways. Over time, these alterations change the ways that water flows in and out of spaces. Our understanding of this movement is ever more imperative as sea levels rise and human development continues.

Computers have expanded our understanding of water management in an exponential sense. But we shouldn’t forget that before computers, people were putting in the time to do the work manually. Instead of digital data, there were notebooks filled with handwritten, daily entries. Stefan Talke, a civil and environmental engineering professor at Cal Poly in San Luis Obispo, is bringing together these two worlds of information for the Delta. His work, merging historical and digital data and computer modeling , will help inform local scientists and water managers about what to expect in their part of the Delta in the future.

Science-in-Short is a quarterly podcast introducing scientists working on emerging topics in the San Francisco Estuary watershed. The podcast is written and produced by Ashleigh Papp with editing support from Ariel Rubissow Okamoto and the Estuary News Group, and music created by Peter Rubissow. Science in Short is funded by the Delta Stewardship Council.

Click here for full transcript and photos.

Interviewer Ashleigh Papp: Over the last 50 years, computers have enabled us to do … a lot. With their help crunching numbers and running simulation models, computers have expanded our understanding of water management in an exponential sense. 

But we shouldn’t forget that before computers, people were putting in the time to do the work manually. Instead of digital data, there were notebooks filled with handwritten, daily entries filled with valuable data. 

And it turns out, the real jewels of today’s research involve bringing together these two worlds of information. 

Stefan Talke. Photo by Lynn Takata.

Professor Stefan Talke: My name is Stefan Talke, and I am a Professor of Civil and Environmental Engineering at California Polytechnic State University in San Luis Obispo, California.

Papp: Talke does some really cool work. He’s weaving together the past and the present. On paper, Talke is an engineer, but in reality, his day-to-day stretches way beyond just one title.

Talke: I do hardcore water resource engineering or coastal engineering. But I combine it with history so that we get a better understanding of how our coastlines and estuaries and rivers have changed. And that gives us clues into what might happen in the future with climate change.

Papp: As climate change intensifies, California’s water management and ecosystem restoration are quickly moving into the research spotlight. And while computer simulations are helpful to understand what’s in store for sea level rise, the data isn’t specific enough for us to understand what’s projected at a super local level. Instead, we have to adapt that information, or “downscale” the work, to make the models more relevant to a certain place. One way to do this is by incorporating historic data that was very much site specific. 

Talke: The projections so far are like, ‘Okay, this is what’s going to happen in San Francisco,’ and all the plans in San Francisco Bay are based off of this projection for San Francisco. But that’s not going to be good enough if you’re in a place that’s sinking quickly.

Papp: To understand Talke’s research today, we have to go back in time. After completing a PhD program in the states, he accepted a postdoc position in the Netherlands. Filled with intricate lattices of rivers and canals, dikes and windmills, the Netherlands has a history that’s tied to water. And Talke’s postdoc work in the Papenburg watershed helped him realize the importance of looking back to look forward. 

Historic records being tapped by Stefan Talke. Photo: Stefan Talke.

Talke: It was all about this estuary and river, which was really, really muddy. And it was so muddy that if you put your hand in the water you wouldn’t see it anymore. And talking to people, it turned out that 20 years previously, or 30 years previously, it was not nearly as muddy. And there were all these old names, like this or that sand bank, and it was more like a mud bank at that time.

And so I got interested in this idea of very fast environmental change. And it turned out that, in that case, what had happened is that the channel had been dredged really far inland, about 100 kilometers, so that they could float really large cruise ships out to sea. So they kept making it bigger and bigger and deeper. And that changed the physics of the system. It pushed it closer to a resonant condition. The tides got bigger, and it also created this better sediment trap.

And all of this was a real revelation to me, I always thought you go and you look at your tide table. And it’s the tide table, you can predict it into the future 100 years, you can look back 100 years, and you could say with certainty, you know what the high tide was on the day your grandparents were born. But it turns out that we actually, by the management, and changes we do to our estuaries like reclaiming land, or making a channel deeper, or other sorts of things like hardening the coastline, that we’re actually changing the way water flows within our systems. And by changing the way water flows, we are also sometimes changing the tides.

Papp: In the areas that Talke was studying, some of the tidal ranges had doubled compared to what they were 150 years ago. Other areas showed more or less no change. A few years later, he was working in Oregon and came across a publication that demonstrated a changing of tides in the Eastern Pacific, or as we know it, the West Coast. 

Historic records being tapped by Stefan Talke. Photo: Stefan Talke

Talke: The changes were particularly large along the Columbia River and in San Francisco Bay. And that piqued my interest like, is this another case of people going in and really making changes? I was interested in history, and I’d seen old pictures of San Francisco Bay and read accounts from before the Gold Rush. And it just was just completely different, right? Like, the South Bay was just filled with wetlands and teeming with wildlife and bears. And just so different than the Silicon Valley that we have today. And so that was the seed of a hypothesis, that maybe this is also happening in the US.

Papp: So Talke put on a historian’s hat and dug into the past, looking for signs of shifting landscapes and documented tidal changes.  

Talke: With the internet and with Google Books and just all the old books that have been scanned, it’s possible to find out what scientists and engineers were doing 150 years ago. And they were writing reports. And it turns out, they were also measuring water levels. They were measuring it in rivers, they were measuring it on the coast. And it was not just like a hobbyist, it was not like they went out there for a day or two, and they were measuring high tide once in a while. But in fact, it was this amazingly well-thought-out and executed program of measuring with automatic gauges that ran for years and years and years.

Papp: After looking through these historic data sets, Talke was shocked when he realized that none of this site specific, hyper-local information was included in modern databases. 

Talke: That was a eureka moment, you’re holding these old yellow papers, from an observer who’s 150 years dead, but had spent his whole life, decades of his life, measuring tides, and then also meteorological events like three times a day kind of thing. And that turned out to be the tip of the iceberg. And I’ve spent the time since then, figuring out how to think like a historian and find all these other old records.

Papp: Eventually, Talke’s historical project brought him to California’s Bay Area and the San Francisco Estuary. 

Historic records being tapped by Stefan Talke. Photo: Lynn Takata.

Talke: Right now we have a project, where we are looking at historical water level records in the Sacramento San Joaquin Delta. And that’s kind of this really, really important area for the State of California. It’s at the transition zone between rivers that are in the Central Valley and come from the Sierra Nevada and San Francisco Bay. And it’s a very unusual Delta. It’s an inverted delta where, usually, you think of a Delta like the Mississippi, where the river splits apart into a lot of different tendrils, and then goes into the ocean, the Sacramento Delta is different. It’s kind of a, it’s an inverted delta, where there’s a lot of rivers coming into it, and only one outlet. And the Delta itself is a very rich farming area. So there’s tons of farms there. Also, it’s really important for the California Water Project, because all the water that’s coming in from Northern California goes through the Delta and then gets pumped out of the southwest corner.

Papp: A lot of California depends on these waterways staying healthy, despite the changes in our most recent history. One big concern is that between sea level rise and the tides creeping further into the Delta, the water won’t remain fresh enough for human use.

Talke: If you get too much salt coming into this region, then it’s going to contaminate the water supply. And so there’s all these measurements that were made. But if you look, and it’s the same story as at the federal level, there are only records available starting in 1982, in digital format. And so there’s several lost generations of data that nobody has looked at that are actually really important if you want to understand natural variability.

Papp: Variability like major flooding events from the 1920s to the 1980s. And then of course, droughts. And don’t forget hugely impactful human activity like gold mining and dredging.

Talke: And all of that means that over decades, or long scales, there’s changes and shifts in what the system looks like. And one of the ways that we can see that is through looking at this data, and we can see whether the whole system works differently now than it used to.

Papp: To bring our current datasets up to speed, meaning incorporate the historical data, Talke and his team at Cal Poly crunched a lot of numbers.

Historic records being tapped by Stefan Talke. Photo: Stefan Talke.

Talke: The first step, when we have an old dataset is, we put it into an excel sheet or a spreadsheet. And then we have to go through a quality assurance and make sure that we did it right. And then you have data and you have to figure out what to do with it. And it’s actually the same problem that people have if they have other climate data, if you have temperature or air pressure or storm data, what do you do with it?

Papp: In Talke’s world, there are two different ways to turn a spreadsheet full of numbers into tangible outputs and information that’s useful to other scientists and water managers.

Talke: One is you could do a numerical model. They use the physics that we know, they’re all programmed into this. And then they make simulations of what might have happened given certain geometry of your bay or estuary, and some boundary conditions. Which means basically you’ve got river flow, and you’ve got tides at the ocean, which we know. And we run the model and we see how that system worked. And we validate it with our historical measurements. And that allows us to infill all the spatial gaps.

So that’s one way that we do things. The other way is, there’s various statistical techniques that get us to evaluate things like tides and storm surge, and river flow effects. And we also use these statistical methodologies to gain insights into long term changes.

And then there’s even more work in terms of processing it and writing the paper and making the nice graphs and proving your point without a shadow of a doubt. It’s not enough to say, ‘hey, we found this really cool data.’ You really have to go and prove to your peers, the people that are reviewing your manuscripts. So not only do you have a signal, like, say the tides have shifted by one meter, but you also have a mechanism, you can explain why it happened.

Papp: It’s a lot of work and Talke and the team are figuring things out as they go. 

Talke: It’s definitely 1% inspiration and 99% perspiration. When I started out 10 years ago, we didn’t really know what was causing the tides to shift so much. And, you’re just kind of poking around in the dark a little bit, and you have some idea, and then you try to figure out how to prove it. I kind of approached it like an engineer, which was okay, let’s just use whatever tool we can to try to understand this, right? Like, you know, a mathematician might just use math, or, someone who just does numerical models might do that approach. But I’ve kind of just done a hybrid approach.I just kept working really, really hard to try to make progress on this.

Papp: Right now, Talke is focused on getting ahold of Delta data from the last 20 years … And of course, figuring out how to bring it altogether, normalize the numbers, and ultimately, make some sense of it. 

Historic records being tapped by Stefan Talke. Photo: Lynn Takata.

Talke: One of the really interesting things that comes out of our analysis so far, is that sea level rise in San Francisco Bay, and especially the Delta is very location dependent. And that’s because the sea level rise that matters – when you’re in a town or when you’re at, say, a power plant or a treatment plant — is not only what is the ocean doing, but also what is the ground doing? And it turns out that there’s many places in this part of California where the ground is sinking. And some of the sinking is due to the response to the last Ice Age, that’s a small component. Some of it is due to plate tectonics and earthquake faults. So some land is rising and some land is falling. But a lot of it has to do with water management, and local human actions.

Papp: Take some parts of the South Bay and the Delta, for example. Groundwater pumping, or diking and draining for farming purposes, and even natural gas removal have  led to noticeable land subsidence. 

Talke: So basically you can go like 10 miles and one place will have sea level rise rates of 10 millimeters a year. That’s a lot if you extrapolate that forward 100 years, you’re talking about a meter of sea level rise even if you don’t have any acceleration in what’s going on in the ocean. In other places that are only 10 miles away, might have something like three millimeters a year, which is about what’s happening in the ocean right now. And what it means is that we really need this data, and more data, so that we can have ultra local or hyper local predictions of what sea level rise effects will be.

This is my hope, that once we actually show the science, and other people have shown something similar by other means, we can actually start to interact with local managers and people on the ground and get them to consider, ‘Okay, what does this mean in terms of prioritizing resources?’ Since the sea level rise effects are going to be so varied, it also means that different places have different interests, right? Like, some need to adapt really fast, and some don’t. The first step is to point out the issue before sea level rise effects become too bad. And then to educate people on what we’ve found, and get other people to also look into this in other parts of the world, is all part of a longer term effort to figure out how to adapt to this thing that we have caused.

Papp: Beyond the tactical outputs of his work, Talke sees his contributions to this field as two-fold.

Talke: Coastal engineering as a profession hit its peak probably 50 years ago. And a lot of the still practicing coastal engineers are older.  Yet now we’ve got this problem with climate change and sea level rise where I see this tsunami of work that probably needs to be done in the next 20-30 years. And in order to be able to do this well, we need to have well trained students. I see my role in those two ways. One is let’s get a little bit of knowledge about the science … Things that have maybe been neglected a little bit. And then also, let’s get some students inspired and working on these problems so we can make a better future.

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