[00:00:22] Bridget Scanlon: I would like to welcome Amir Aghakouchak to the podcast. Amir is a Professor of Hydrology and Water Resources at the University of California at Irvine. His research covers many different topics. And today, I think we are going to focus the discussion on hazards: drought, floods, snow droughts, fire, and things like that. Thank you so much, Amir, for joining me.
[00:00:47] Amir AghaKouchak: Thank you.
[00:00:50] Bridget Scanlon: So, Amir, I think in a lot of people's minds, the recent LA fires, which just occurred in January, are still fresh. You don't live too far away from them. These devastating fires affected maybe 16,000 properties. I saw an estimated $30 billion in damage on the web, in different regions like Palisades, Eaton, and Altadena.
I was out there recently for a NASA meeting, met people who had lost their homes, and drove through some of those areas. Really devastating. You discussed these types of things in your papers because we've seen them before. So maybe you could describe a little bit about them and what you felt was the lead-up to these events.
[00:01:30] Amir AghaKouchak: Sure, fires can have many different drivers, and maybe look at this specific event. Looking at October to December rainfall, we had very little rainfall, in fact, the lowest on our historical record during this period. So, we had a dry period, and at the same time, we had very strong Santa Ana winds. Santa Ana winds are very dry but strong winds that set the stage for fires. The year before, we had a lot of rain. Rain means vegetation growth, and vegetation growth means fuel for future fires.
So, we had many different potential contributing factors: fuel, dry conditions, and also Santa Ana winds altogether. And the winds were very strong. So, the case of LA fires was really a wind-driven, urban fire that was very hard to control, of course, and had significant impacts. It's hard to highlight one driver. Usually, there are many different drivers that interact with each other and lead to an extreme fire like that.
[00:02:37] Bridget Scanlon: Right, and so, I guess you've seen this before in different fires, like the Thomas Fire in Ventura and Santa Barbara that occurred in 2018. Maybe similar lead-up conditions. Maybe you can describe that a little bit, Amir.
[00:02:53] Amir AghaKouchak: Exactly. So, if you look at that specific event, we had a five-year drought that ended with a lot of rain in early 2017, during the rainy season. And again, a lot of rain means vegetation growth, but that summer of 2017 was very hot and dry, and we had multiple heat waves that year.
So, all this vegetation now dries up and is ready for the next ignition. And that year, 2017 in December, traditionally outside our typical fire season, there was this massive fire. The Thomas Fire at the time was the most extreme, the largest fire on record. We have broken that record six times since then, but at the time it was the largest fire on our record.
Just one month after the fire in December, in January 2018, near Santa Barbara, there was this rain over the burned area that caused a debris flow event, and unfortunately, 23 people died. So, there's an example of cascading hazards from drought to a lot of rain and local flooding to again, drought and heat, fire, and debris flow events all happening over maybe five or six years.
[00:04:16] Bridget Scanlon: So normally, when we think of droughts, floods, and these extreme climate hazards, we think of them in isolation, and we develop indices and look at different parameters like rainfall and temperature and that sort of thing. But what you are describing then is the sequence of events and cascading hazards that can amplify the impacts.
You mentioned the 2012 through 2016 drought, which was a very extreme drought. During that period, California developed the Sustainable Groundwater Management Act. But then at the end of that, you had a family of atmospheric rivers coming in January 2017. This led to a lot of vegetation growth, followed by drought again.
I don't really know much about the Santa Ana winds. Were the Santa Ana winds a contributor to the Thomas Fire? And do they occur every year?
[00:05:11] Amir AghaKouchak: Every year. The intensity varies, of course, and the timing also varies. Sometimes they happen earlier in the season, and if they happen when vegetation is wet, usually the impact is lower. But then if they happen later in the season when vegetation is primarily dry, they can potentially have more impact.
So, the timing varies. The severity, the wind speed varies, but again, they happen every year.
[00:05:41] Bridget Scanlon: And I think probably a lot of people are asking, insurance companies are asking cities and homeowners, what can they do to reduce, what can we do to manage these impacts, and to reduce the impacts and to become more resilient to fire and drought and things like that.
[00:06:02] Amir AghaKouchak: I'm not an expert on the insurance side, but we need to work on enhancing our resilience. And if you look at our data in historical events, we see this pattern of extreme rain events and then maybe a year or two after we see large, massive fires. This means that, when we see the signal of lots of rain, maybe one or two rainy seasons, we have to prepare, we have to step up our activities on removing brush and fuel from near urban areas, at least to reduce the amount of fuel available for future fires.
Yes, we don't have good models for fire prediction, models that predict fire are very uncertain. But again, when we see the signal, especially in places like California, that historically we know after a lot of rain, we will eventually have some large fires. That gives us good lead time for cleanup efforts at least, but we also have environmental regulations that make it a little difficult in some places. If you want to remove brush or do cleaning, you have to go through a process to get permits and that process is not straightforward. So, we deal with a little bit of overregulation, and of course, we all want to protect the environment.
We have environmental regulations for certain reasons, but my feeling is that we are probably overregulated, and it makes it very difficult to quickly respond to signals that we see. That's one potential issue. So, we need to really look back at all of our environmental rules and look at them holistically and see which one makes sense, which ones we need to update and adjust.
So, we have the flexibility to respond quickly to signals that we observe. And also, when you look at urban fires, it's pretty obvious that materials play a big role and looking at building codes, we have seen improvements over the years on fire resistant materials, but we need to do a lot of work in this space and working on materials that can improve fire resistance and create incentives. This could be insurance incentives or incent tax incentives to upgrade and improve local resilience, especially. This is really important in urban fires.
[00:08:44] Bridget Scanlon: And then also I guess the wildland urban interface, with the increasing urbanization and expansion outside of our typical urban areas, there's increased vulnerability associated with that and even somebody was saying to me, an emergency manager was saying, you shouldn't have a wooden deck.
And of course I do, we do at home and I'm sure it's not fire-resistant wood or anything. And then having a certain space between your house and the trees and as you see the difficulty of cleaning up, so you have millions of dead trees from previous fires or droughts or whatever.
And who's going to clean up these things, especially in these open spaces …who is responsible and it's expensive. And so, there are a lot of things that we might be reluctant to do or pay for whatever, but as we keep seeing these fires then maybe we will get better at taking heed of these things.
[00:09:39] Amir AghaKouchak: I hope so. I hope we learn from all these devastating events that we need to update and adjust and improve. And historically we have, if you look at flood risk management. If you look at drought risk management over the years, we have made significant advances. Fewer people are dying now from floods than 50 years ago, a hundred years ago.
We know that's data because of everything that we did. Fires at the scale that we see today are relatively new. Of course we have always had fires, right? I'm not saying we've never had fire, we had fires, but, in terms of impacts and frequency and severity of events that are happening, they're relatively new. And we need to work on solutions, just like what we did for floods and many other extreme events.
[00:10:30] Bridget Scanlon: And life is risk management, and you think about the hazards, which would be the drought, the floods or the fires, and then your exposure, and then your vulnerability, thinking of all those components of a typical risk management. And one of the things that you mentioned, when we chatted the other day, was that we really don't have the data together to address these compound or cascading events.
And so, what are your ideas about trying to pull those data together so that we can have them for operations or other things?
[00:11:05] Amir AghaKouchak: You mentioned here in our conversation that we usually look at these hazards separately, and that's correct. You look at individual hazards, there are even different agencies in charge of different extreme events or hazards like you have no one that mainly is in charge of atmospheric extremes.
And USDA, the main federal agency that works on fires, and also USGS, maintains our flood records. NOAA maintains our rainfall and temperature data and other atmospheric variables. Look from this perspective. And also, they have, like NOAA has, warning systems for drought and for storms or extreme storms.
But they don't provide the same kind of fire simulations, for example, or fire warnings only. From that perspective, ideally, I think we need to move toward integrated systems. So not just from the science perspective, but also operation agencies. It's maybe it's a hard thing to do, but eventually we need to converge on a unified system for all these different hazards because they are related.
Yes, they happen over different time scales, over different spatial scales, but they are one way or another related. And ideally, we want to look at them holistically, even at the warnings level. And then scientifically, you are right. When you look at research in this space, most papers, most studies focus on one hazard at the time.
Compound events are getting more and more attention. Now we know extreme events interact and we need to work on methods for risk assessment. A lot of our existing guidelines and methods are based on one hazard at the time, and there are even specific cases that we know. We know they are related, and we have even models that we can use to model compound events.
But when it comes to guidelines, we ignore those relationships. For example, when you look at USGS flood frequency curves. The way the flood frequency curves are calculated in coastal areas. They ignore the dynamics of ocean water level, like high tide versus low tide. But we have hydrodynamic models we can simulate numerically with physics-based models, the interaction between ocean and river, right?
We have the tools, but when it comes to guidelines like estimating a hundred-year coastal flood, we ignore this ocean dynamics, right? Now one of the studies we worked on, now it's part of a SC Primer for Practice, is a framework that allows you to bring ocean and river data together for multi hazard flood risk assessment in coastal areas.
So, both on research and operation spaces, we have this disconnect between different hazards and we need to work on both dimensions.
[00:14:17] Bridget Scanlon: And I think we're starting to do that. We're working on a project for the Department of Energy on hurricanes, and recognizing storm surge, and inland flooding, and fluvial flooding, and trying to put it together then to understand the overall risk. So, I think we are moving in that direction, but we have a lot more data now.
We've got detailed, you mentioned, debris flows and stuff like that. We've got detailed topographic data, lidar data. And remote sensing and airborne and drones and all sorts of things. And then we have tools to harmonize these. We have data-driven models or reduced order models to make it faster.
So, but we are still not there at all. We have a long way to go, but we are moving.
[00:15:06] Amir AghaKouchak: Exactly. Like compound flooding. That's a very good example. We know it's important. We have seen Hurricane Harvey multiple days of direct rainfall on top of an already flooded area, right? It's important, but when it comes to guidelines, again, we ignore it just for simplicity maybe. But now we know that we should change our perspective and maybe account for these seemingly little things here and there. But overall, this overall major event like Hurricane Harvey plays a big role.
[00:15:41] Bridget Scanlon: I think, we need to combine a lot of these data sets. And one of the things that you mentioned is lot of our hazard indices and everything, drought, floods, whatever, focus on the drivers. And we really don't have indices that consider the impacts. And I know that's going to be challenging, but maybe you can describe that a little bit, Amir.
[00:16:05] Amir AghaKouchak: So, if you look at, for example, current drought monitoring or assessment systems. They show, for example, rainfall deficit relative to long-term record or soil moisture deficit relative to some kind of baseline. So, they focus on variables or drivers mainly. And there is this disconnect with impacts.
For example, impact on crop yield, the agriculture sector broadly, or impact on water availability. Impact in terms of storage in our reservoir systems, water supply, and because of that, it's really hard to link what we see from our existing drought monitoring systems with decisions.
For decisions, you need to have an idea about impacts, and we call this perspective impact-based monitoring. So, we need to move toward impact-based monitoring of extreme events, including droughts, floods, and so forth. In other words, if this online monitoring system is showing deficit in a certain variable, let's say rainfall, this should be linked to impact on maybe food production or maybe jobs, unemployment or something that can translate the kind of climatological deficit into societal impacts, socioeconomic impact that allows us to make better decisions. If you have an idea about impact, it's not easy. It requires a lot of data. But now with data that we have, as you said, we have now a lot more data than 20 years ago, 50 years ago. I think there are opportunities to move in this direction.
There are studies already published and impact-based drought monitoring, flood monitoring. We need to put more effort I think in operationalizing this sort of impact-based systems. The other dimension of impact-based monitoring of extremes is this notion of trade system, trade networks, impacts can propagate across space.
So, a drought in the US will not result in food deficit or calorie deficit in the US. Impact will propagate to countries that import food from us just because we produce so much food. And most of it goes for export, right? So, this kind of propagation of impact is something that today we can model.
We have trade data, we have network models, so we can simulate how local droughts will propagate around the world. And we can potentially look into compounding effects of drought in different continents. What if there is a major drought in the US and at the same time there is a major drought in Australia?
Two major food producing countries. Again, these events may be climatologically independent, but they can have major compounding impact on each other when it comes to global food distribution or food trade network and cause significant deficits of calories in a certain, in another part of the world that has nothing to do with Australia and the US.
[00:19:30] Bridget Scanlon: I think I've seen some papers, like that, a few years ago, where they looked at climate teleconnections like El Nino and then drought here in one country, in another country. And then, which countries were totally reliant on those who had a diverse portfolio that they imported from.
And so, I think you also mentioned in some of your papers like translating shocks that the economists do and stuff like that. So, I think we can learn from those and start to do more of that and better understand our vulnerability then. Considering just direct vulnerability, but also, based on our trade and other aspects.
[00:20:09] Amir AghaKouchak: Absolutely in this space. What I am personally interested in is compounding effects of climatic and non-climatic events. For example, the war in Ukraine we know has caused a lot of problems for countries that imported food from Ukraine. Ukraine is also a major food producing country. For example, Egypt imports foods from multiple countries, including the US and Ukraine.
What if there is a major drought in the US and war in Ukraine, or different combinations of extreme events and non-extreme? Completely independent nonextreme events. The issue with independent events is that we cannot use traditional statistical models to bring them together.
Like, war and maybe drought in the US is completely independent from each other. But again, we have trade networks, net graph theory, and a lot of mathematical models that allow us to look at compounding effects from an impact perspective, not from a driver perspective, and those questions are really fascinating to me.
[00:21:21] Bridget Scanlon: And do you think, coming back to drought indices like the US drought monitor, they don't really consider impacts that much, do they? But after a drought, you'll see reports of the livestock loss, and the food loss and the billions of dollars of damage, but nothing ahead of time.
No, no sort of forecasting. And you also mentioned, it'd be good to do scenario analysis for these hazards, for these compound hazards and how to help emergency managers and evacuations and all of these different things. So that kind of combined data set and modeling and stuff would help these people also try to manage these events.
[00:22:02] Amir AghaKouchak: I agree. In fact, in most cases, if you are surprised from an event or a series of events, it's too late to do something really significant, right? You don't want to be surprised. And to avoid that kind of surprise of a series of events, compound or cascading events, we need to have a good understanding of all possible potential extremes and combination of events and one method that we have used in different fields. It's this kind of models of different kind of shocks to a system. Trying many different possibilities and looking at response of the system. Again, we have a lot of development in this space in economics, finance models that focus on, for example, the financial market and stock market.
They run scenarios of what if scenarios of oil prices going up and oil prices going up, and gold prices going down and, different, conflicts, even what if there is a major war? So, we need to do some of that also in our field. Looking at combination of different extremes that can potentially lead to massive societal impacts.
And to understand those events, we need to develop models that are reliable and then run many different scenarios of compound and cascading events and basically get an idea about what combination of events can potentially cause massive disruptions, and what's the likelihood of those events to happen together. And specifically, we need to look at, even non climatic independent events, problems that can happen in another continent event, but can potentially affect us through networks and trade networks. When it comes to evacuations, it's the same story right now. If you look at fire evacuations, they are based on location.
So, a fire is happening, emergency managers decide what area to evacuate. And in the recent LA fires, there were reports of people getting stuck in traffic, problems with evacuations. A few years ago, Oroville Dam was in danger and the spillway failed and authorities tried to evacuate 200,000 people from downstream.
It was not very successful. A lot of people got stuck in traffic. It took longer than they expected. And, for major events, evacuation needs a lot of preparation. And I think for extreme events, again, we need to run many different scenarios in advance. And mathematically practice evacuation on paper again, if there is an event here, what areas should be evacuated first if it is in a different side?
And through that experiment develop event specific evacuation plans. So, for example, for Los Angeles National Park. On the eastern side, if the fire starts on this side, what areas should be evacuated first, and how and what if the same fire is on the western side and so forth. But again, it's not easy. Takes a lot of time, resources, and effort, but I think it's needed to have evacuation plans that are event specific.
[00:25:30] Bridget Scanlon: And I think Austin is, the city of Austin is ranked sixth after a number of California cities for fire vulnerability. And I think some suburban areas, they only have one way out, and stuff. And so, I think if they went through some of these types of analysis, and we're not talking about off the wall scenarios, we are talking about things that we've seen. Even that maybe make it more realistic to go through that first with them, and then expand because extreme events are generally low probability, but it can be a huge impact. And so, I think these exercises would be extremely valuable and putting them together and mathematically going through it and working with the emergency managers and all of these types of groups, and bringing the agencies together.
You mentioned USGS is responsible too for river flow and floods and stuff, and NOAA is responsible for rainfall and other things. But we even see the same thing in hydrology, one agency is responsible for groundwater, another agency responsible for surface water, but when they pump the groundwater, they reduce the surface water.
[00:26:37] Amir AghaKouchak: That's correct.
[00:26:37] Bridget Scanlon: So, all of these things are interconnected. And, because of these interconnections, then the risk may be amplified. And looking at them solo, just won't get at the true risk.
[00:26:50] Amir AghaKouchak: And you mentioned in many places we have only one way out. We have a project right now in Lake County, California, and there are areas that there is only one way out. What if that road is blocked? In fact, I looked into hazard mitigation plans from multiple cities. FEMA provides funding for cities and counties to develop their own hazard mitigation plans, and I went through a bunch of them to see if there is any information, if there's any map on places where they have only one kind of access. I did not find that in the maybe four or five hazard mitigation plans that I looked at, and that is concerning. If we don't know exactly where those places are, and if they are not in our hazard mitigation plans, we have a problem. It's a major issue, I think.
[00:27:39] Bridget Scanlon: And that's just one of the things to think about, but there's so many others. So, I think that scenario analysis sounds fantastic. And one of your studies emphasized anthropogenic drought, we're accustomed to thinking about, meteorological drought or agricultural hydrologic, but maybe you can describe what you mean by anthropogenic drought.
[00:28:02] Amir AghaKouchak: Sure. Absolutely. So, you're right. We usually look at deficit precipitation and soil moisture, but we sometimes ignore local water demand. In many places, our local water demand dominates everything. For example, in Southern California, even in a wet year, we still have to bring water from Northern California, from the Colorado River to survive, right?
So we are, in terms of net water availability without importing water, they are always negative. It doesn't matter if it's a wet year or dry year. So, this is an example of kind of anthropogenic drought we have created this situation, right? There are many other cities or areas that have more or less the same kind of condition.
In some places it's really bad. Lakes are drawing down, wetlands are disappearing, because again, there is a, basically deficit, like a constant deficit. Groundwater levels are dropping because again, human water use is dominating everything. That's one kind of dimension, putting emphasis on this human water use. Water withdrawal from groundwater systems, water transport from one basin into another.
The other dimension, of course, is the climatic part. We know that emissions in the atmosphere can potentially change your rainfall. So, there are two aspects, but what I am more interested in is local water management, what we do locally, because that's where we have control.
Yes. Emissions. We don't have it immediately, we cannot control it immediately. And even if we do, there are long-term impacts on the atmosphere we don't have much control on, but how much water we are extracting from our groundwater wells. We have control over how much water we are bringing from different basins.
So, with that concept, we wanted to put local water management, water demand, and decisions into perspective of the overall water balance. So, we call that anthropogenic drought. And, if we believe that if this kind of condition continues for a long time and this deficit increases, it can lead to water bankruptcy in a place where it's really hard to recover from that situation.
[00:30:33] Bridget Scanlon: I think a little bit of what you're describing is what we're seeing in the High Plains aquifer in the central and southern High Plains, over abstracting groundwater to support irrigation. And, the recharge is, it hasn't been recharged for thousands of years.
So, I recall a colleague doing a study on climate change impacts there, and they said, this is dominated by pumpage.
[00:30:56] Amir AghaKouchak: Absolutely.
[00:30:57] Bridget Scanlon: It’s not controlled by climate.
[00:30:58] Amir AghaKouchak: I totally agree. In several study areas when we looked at climate change and variability and human water use, the human part dominates significantly.
[00:31:10] Bridget Scanlon: I think maybe Charlie Vorosmarty had a paper in Science in about 2000 where he was looking at population impacts versus climate impacts, and emphasizing the importance of populations. And I think that puts more control in people and how they want to adapt and how they want to handle the situation.
Transitioning from irrigated to dryland agriculture, changing crops or doing different things to adapt rather than just, saying it's something that's outside my control and I can't do anything. I think it's maybe they can manage it. Or they understand what they're doing, and this is what they want to do, but it's maybe not sustainable.
[00:31:49] Amir AghaKouchak: And in some countries at least, politicians use climate change as an excuse. Sometimes they say, oh, there is this drought, and this lake is disappearing, and groundwater is dropping. But it is because of climate change. We are not responsible. We didn't do anything wrong. And if you look into a lot of politicians, they just use it as an excuse.
[00:32:10] Bridget Scanlon: And California is moving more towards Sustainable Groundwater Management Act that passed in the middle of the extreme drought that you were describing 2012 through 2016. So the act passes in 2014, and now they're developing, putting plans to bottom up then with all these agencies, sustainable groundwater agencies, I think. And then developing the plans and then putting it all together and having the state as a backup if the local groups cannot manage to do this.
So that's moving in the right direction. I think it's improving the data availability, groundwater levels, reporting of wells going dry and all of these things, which is very important to understand.
[00:32:54] Amir AghaKouchak: That's right. I think it's going in the right direction. An extreme drought brought us together for this to happen. So that was the positive side of a major drought. And usually, after a major extreme event, we come together, and we try to come up with solutions to improve our resilience.
And this is a good example. And as far as I know, it hasn't been a very smooth process. So still some farmers don't like the way things are being managed. And there are all kinds of complaints and lawsuits here and there, but overall, I think it's moving toward a good direction. We needed to do this.
And you know this better than I, it is a long-term plan, like they started this slowly. And I think that was very smart. They didn't try to change everything overnight. That was very smart of the managers. I think they slowly expanded the scope, and the rollout was over a a 10-year process and then the next 10 years and so forth.
And I think overall it's going toward the right direction.
[00:34:06] Bridget Scanlon: And I think in some of your studies you described how we can try to manage water resources more sustainably. Oftentimes we focus on the supply side, increased supplies, desalinate sea water, reusing wastewater I think is great. And inter basin transfers, different things like that, but then reducing the demand, I think the urban areas are doing that and incentivizing it with technology and other things.
And then storing, the Army Corps of Engineers doing a nice job with the Forecast Informed Reservoir Operations and linking surface reservoirs with managed aquifer recharge. In LA linking Prado Dam and managed aquifer recharge. That's really nice. So, a lot of things are making one hopeful that with all of this different demand we need to do, we need to move everything in the right direction.
[00:34:57] Amir AghaKouchak: I agree. Demand management is really important, and we really need to start with demand management. And traditionally, you are right. We focus on supply, bringing more water through water transfer or desalination. But I think demand management should be prioritized and then looking at supplies and how you can improve your supplies in major cities.
Water recycling, recycling wastewater is definitely a great opportunity here in Southern California. Locally, I think they recycle 200,000 gallons per day and all the greenery in southern California, in our area at least, it's all with this recycled water and it has improved our systems here, if you compare in our region in Orange County, even during the latest drought, water levels in any our aquifer systems were healthy just because of all this recycling.
It can have really long-term positive impacts. But yeah, this demand management is really important in many other countries. You look at, you see what's happening to lakes and reservoirs, and the main problem is, again, the demand is way more than what's available. And without demand management, we'll see significant environmental impacts.
[00:36:19] Bridget Scanlon: And you have had water markets to a limited extent, in California. And that helps. And you also mentioned trying to go to higher value uses, and I oftentimes think, we'll just all be drinking wine and we won't be eating at all because the vineyards maybe, or whatever would be the higher value.
And almonds. Yeah. A gallon an almond.
But, the water markets, I guess during drought, you can buy, not use your water or things like that. Or maybe in the past you would fallow the land, but now more perennial almond trees and other things. So, it's much more difficult to fallow land. In the past you would fallow land and in near San Antonio and Texas, the city purchases water from the agricultural sector if they know there's going to be a drought and then they won't use it for irrigation. So, these sorts of things, and even in Phoenix in the Lower Colorado River Basin temporary buyouts of water rights but all of those were temporary measures. They weren't permanent buyouts from agriculture, but I think long term we'll just see water moving from agriculture because it's the elephant in the room, to other sectors.
[00:37:34] Amir AghaKouchak: Yes. And historically, if you look back, we have seen these transitions from mining sector to agriculture sector and in many places from agriculture to services or agriculture to tourism. And even in California, things are changing, and agriculture is a very small fraction of GDP in California.
Even our most extreme drought will not have that much of an impact on the total GDP. But it varies significantly in some other countries or some other states, not the case. Agriculture is really a big part of the economy, the shift is happening, especially in California and many other places, especially in the developing world.
And because of that, so yes, there’s a shift in balance of water and the value of water as well. And that markets, it's good to have the market at least. It gives you some flexibility to move water between industries, farms and sectors to make the most of available resources,
[00:38:40] Bridget Scanlon: I think one of the things that you mentioned in your anthropogenic drought is employment. We know agriculture is not a huge part of your GDP, but it employs lots of people, and so from that perspective, I think it's very important.
[00:38:55] Amir AghaKouchak: Absolutely important. In fact, that's why in California there's a lot of investment in this space. It's mainly because of jobs and employment. And we know that unemployment leads to higher crimes and all kinds of long-term health impacts if people lose their health insurance. And that's the main issue.
Employment and jobs, even in California, even though agriculture is a small fraction of GDP. There is a lot of focus on it just because they want to have people who have jobs and opportunities, and livelihood.
[00:39:27] Bridget Scanlon: So, in California, and going to the source of the water and to the mountains and the snow, you often see in the news, April 1. What has the snow looked like? And what has the snow season been? And that's a good predictor of your water availability for the summer. So, you've done quite a bit of work on snow droughts and things like that.
Maybe you can describe that for California first, and then maybe discuss briefly your global analysis.
[00:39:54] Amir AghaKouchak: Sure, we rely on snow in Sierra Nevada mountains. And snow is like a natural reservoir, and we have looked into response of snow to different levels of warming. And we noticed that, for a fixed time of the year, let's say April 1st, which is a kind of indicator of a good kind of indicator for snow availability for the rest of the season, it's toward the end, right toward the end of the snow season.
Even one degree temperature change, average temperature change leads to about 20% change in snow water equivalent at that time of the year, which is very significant. So, it shows that even one degree temperature change can have significant impacts on snow water equivalent if snow melts faster than normal.
Basically, flood risk increases early in the season in the spring. But we cannot control this water, we have so much reservoir capacity, so we have to let it go to the ocean. Faster snow melts not only increase flood risk, but it also increases drought risk even within the same water here. It's a major issue, especially with warming temperatures and snow dynamics.
This notion of snow drought becomes really important. So, a few years ago we published like a global data set of snow drought to study how they change. We have a record of places where we had above average rain, but dry conditions. And then you look at those events specifically, you see the deficit was in snow. Maybe the rain was above average or near average, but because of below average snow, eventually you end up with drought situation.
[00:41:38] Bridget Scanlon: So, the total precipitation was the same, but the snow fraction was lower, and then that made them more drought vulnerable.
[00:41:46] Amir AghaKouchak: Yes, in warmer than usual years, sometimes this ratio of rain relative to snow changes so you get more rain, less snow, and again, yes, your average total precipitation, maybe more or less the same, maybe above average. But if it comes in the form of rain, it goes out of your system relatively quickly.
So ideally, we want it as snow. So, it remains in the system longer.
[00:42:17] Bridget Scanlon: It's just like another reservoir, right? Yeah. And so that shift in the seasonal water availability, so more in the spring, and then you have less buffer then at the end of the summer. And so, you're more vulnerable to drought at the end of the summer if the snow is low. And so, you study then Northern California, Northern Sierras were more vulnerable to this temperature increase than the Southern Sierras because I guess, the snow is at a higher elevation in the South, about a kilometer higher. So, in the north is about two and a half kilometers.
[00:42:52] Amir AghaKouchak: So, in Northern California we get more snow relative to south and also the snow level is lower. Yes, that's correct.
[00:42:59] Bridget Scanlon: And so, with this temperature increase, then you see the snow at a higher elevation. It just moves up.
[00:43:05] Amir AghaKouchak: The center of mass basically goes up and in those papers, we quantify to what extent the center of mass of snow goes to higher elevation because of warming temperatures.
[00:43:18] Bridget Scanlon: And when you look at that, globally, these high mountain snow areas, they're really the water towers for a lot of irrigation and food production and stuff. With climate change, maybe initially, our glacier melting and things like that, you'll have a higher flow, for a certain period of time, but then long term it would be lower.
[00:43:41] Amir AghaKouchak: That's correct. That's consistent with projections.
[00:43:43] Bridget Scanlon: A lot of things to think about. So, you can't, I can't, we can't retire yet. Or I can't anyway.
[00:43:51] Amir AghaKouchak: Lots of opportunities and exciting topics.
[00:43:53] Bridget Scanlon: Yes. And a lot of data and a lot of tools and a big need then.
Are you pretty optimistic that we will be able to adapt? And as you mentioned earlier, we have advanced a lot in the flood space, in managing flood risk and things like that. And maybe we will get there, eventually and keep learning. And I think this compounding and cascading of events, I think, the insurance industry is really grappling with that too.
And basically, cities and all different groups trying to understand how to deal with it, but I like your approach to try to make ourselves more resilient, to manage the vegetation better after these wet periods and so that we are not so vulnerable during the next drought.
[00:44:39] Amir AghaKouchak: Yeah, I'm an optimist and I believe we have historically learned from past mistakes, past extreme events, past political problems, and over the years we have improved our resilience. And I think that there are opportunities to enhance our resilience, and we will probably adapt and hopefully survive.
[00:45:03] Bridget Scanlon: And I like your approach to much more comprehensive hazard indices that include the human aspects that you mentioned, the socioeconomic factors, the employment and all of these different things. And the impacts on crop production and I guess even from the economists and stuff, looking at trade networks and shocks and all that, how they transmit. So, we make countries and other regions more resilient when they better understand these risks.
Thank you so much Amir, for your time. Our guest today is Amir AghaKouchak and he's a Professor at the Department of Hydrology and Water Resources, University of California Irvine.
[00:45:44] Amir AghaKouchak: Thank you again, Bridget. It was a pleasure.
