 Next speaker is Ryan Smith. Hi, I'm Ryan Smith from Missouri University of Science and Technology. I do a lot with looking at land subsidence with INSAR and also combining that with near-surface geophysical data. So I wanted to show you first here just a global map that compiles different studies of land subsidence. So, you know, subsidence is... that'll typically happen in confined aquifers under major use scenarios. So you have a lot of groundwater demand and they're pumping at least a significant portion out of confined aquifers. You can get some subsidence in unconfined aquifers as well, but because the amount of subsidence is proportional to the change in water level or head, you're typically getting much, much bigger drops in confined aquifers, so that's where you see most of the subsidence. So as you can see, this is something that's happening globally. We've seen already some stuff in the Central Valley and I'll show you a little more of that in a minute. We've got some in quite a bit in Mexico, in Iran, China, Indonesia, and many other areas. And this is by no means a comprehensive map either. There are many areas where there's significant subsidence going on and we haven't measured it or someone hasn't and it slips through the cracks. So I'm going to talk specifically about a high-use scenario in the Central Valley in California, and we've done a lot of research there. It's kind of a hot topic area, but I'd like to point out that what we're doing in the Central Valley, these approaches and a lot of these challenges are common to other areas, but as has been brought up several times, the availability of in-situ data is always going to be a challenge as you move to other areas that may have less data or data that are harder to obtain. Okay, so zooming into the Central Valley, and you've seen already a nice map of land subsidence in the Central Valley. So I'm showing that again here on the left and it's representing a loss of groundwater storage and Matt gave a nice overview of this as well. It's for the most part a permanent loss of groundwater storage and in the area that has the most subsidence, it's happening at a rate of around 25 centimeters per year. And this has happened from 2007 to 2010 in a recent drought and then again it resumed going from 2012 to 2016. I say resumed, but there's really residual subsidence that will continue even after the drought ends. So a little overview on the Central Valley, it has about 1% of the nation's farmland. It's a very intensive agricultural area so almost all the water demand is coming from the farmland. So on that 1%, they're producing about 8% of the nation's food by value. That's valued at around $44 billion per year. Almond groves, pistachios, a lot of these are high value crops that need to be irrigated in a drought year just as much and more. You can't just go without irrigating them or you lose a lot of money. So one of the things that we've been interested in is how can we understand and quantify why some areas are subsiding a lot more than others. This is a function of the geology as well as the groundwater pumping. And it turns out that in this region that you're seeing, the figure on the left, most of that area has similar groundwater demand and similar declines in head, but there's a dramatic increase in subsidence to go to the central and southern part of the valley. So one of the more promising approaches that we've used to try to quantify this, why these certain areas subside more than others, is by coupling inside derived estimates of subsidence with airborne electromagnetic estimates of groundwater properties and aquifer properties. That allows us to see how thick the clay deposits are and those tend to cause the most compaction. So we developed a coupled model and that estimated the aquifer properties as well as the textural properties. And you can see the results of that model over on the right showing it matches the historical subsides and subserved pretty nicely, but we're also able to use it to forecast future scenarios. So if we're able to recharge rapidly or if we have continued drawdown, what sort of scenarios are we looking at? And one other thing I want to mention about this, this is a good approach that has some potential for going to other areas where we have very limited groundwater data because you're able to get a good sense of the geology through AEM data and then INSAR is a good proxy for hydrologic changes. So one last thing I want to talk about with this high use scenario, so we heard about arsenic, Holly gave a great talk on that. And a lot of times, especially in Southeast Asia, you'll go deep to try to get clean water that's arsenic free. There's been two studies now, one we did in California and another from urban et al in Vietnam that showed that going deep and pumping deep for clean water was in those two cases, releasing arsenic from clays where it had previously been trapped and increasing that arsenic in the groundwater supply. So as Holly also mentioned, arsenic is very complex and there's a lot of things going on, but it's another thing to think about in these major use scenarios where you're pumping a lot from confined aquifers. You are potentially damaging your water quality as well as losing the quantity. And that's all. Thank you.