Hi, my name is Philip Binning. I'm a professor here at the Department of Environmental Engineering, at the Technical University of Denmark. I'm going to be talking to you today about groundwater protection. What is groundwater? Where is it? And what can we do to ensure it for the future? Groundwater is an important resource. For example, in Bangladesh, there are more than a million groundwater wells, tapping the underground water resources. And 75% of irrigation in Bangladesh is getting it's water from groundwater. Where is the world's water? Well, if you look at it, fresh water is only 2.5% of the world's water. And of that 2.5% then 30% of that fresh water resource is groundwater. A large other portion of it is glaciers and a very small amount of it is rivers and lakes. So, of the easily obtainable fresh water resource, and groundwater is by far the biggest reserve that we have today. NASA and some colleagues in the United States have done some really nice work to try to figure out how much groundwater we've got. And they made this figure, it shows the groundwater depletion that's been recorded over the years 2003 to 2013. And they did this by using satellite information. There is a satellite orbiting the earth called the gray satellite, which can measure the earth's gravitational field and the more water there is on the surface of the earth, the greater the gravitational field. So they can actually measure how much water we have. And by doing that, they've quantified where the world's groundwater is, and this is the map of the world, and you can see the major groundwater basins in the world, and you can also see in the colors how much water there is being added or taken away from those groundwater reserves. If they're blue, we're doing great. That means more water and groundwater. But, if they're red, then the groundwater is being depleted from those reserves. And if we're looking at the colors, bright red, like this one in India, is indicating that the groundwater reserves are being depleted by more than 20 millimeters per year and that's a lot. So this can be expressed in another way and that's shown on this figure which shows the groundwater depletion in the Central Valley in California. Which is one of those groundwater basins that we were looking at before. So this is year on the bottom axis and we've got 1925 at the left and 1980 at the right. And what we can see is the groundwater level in wells in the Central Valley in California as a function of time. And what you see here if for example, this red well, you can see that back in 1925 the water level in feet was 350 feet above some reference. But, and that turns out to be quite near the land surface. But in the 75 or 60 odd years that go between 1925 and 1980, the groundwater at that location on the red line there, has been depleted by 300 foot, that's about 100 meters. That's a big issue, the groundwater is disappearing, so the reserve is disappearing. It's also from a practical point of view, a big problem because the deeper the groundwater is, the more expensive it is to get up. because you have to pump it out of the ground. So what's all this groundwater being used for? Well, if you look globally one of the biggest uses of groundwater is agriculture. For instance, here in India 89% of the groundwater reserves are being used to irrigate our crops. So there's a very strong link between groundwater and our food production. That can be summed up if you look at the water footprint and this gives you some indications of some of the things we can do to manage our use of water. Different crops use different amounts of water. So for instance, if we take rice which was in the previous picture, then to produce 1 ton of rice, we need to use 2,000 meters cubed of water to produce that ton of rice. That can be compared with coffee, which needs to use more than, almost ten times as much water or potatoes and yams, which need to use about a tenth as much water as rice. So you can see that by choosing a different crop type we can strongly manage the amount of water that we can use. There are also technological solutions to our water use. If we look at irrigation, which was the biggest user of groundwater, we can irrigate like this top picture, which is a traditional sprinkler type of irrigation. Or we can do it smarter and that need not be something that involves complicated technologies. For instance, these bottom two slides of pictures on the slide show drip irrigation systems which allow you to, in a very controlled way, put the water on the crops and minimize the evaporative losses, which are obviously very high in the top picture. The other side of a groundwater supply which is very important is water quality. And that's also linked to the agricultural issues that we presented before. One of the big issues that we observe around the world is land salinization. And land salinization is linked to groundwater and irrigation. All groundwater has salt in it. And if you irrigate with it, what you're doing is you're extracting the groundwater up from the sub-surface. You're irrigating it on your crops, so it's going through the crops and back down into the groundwater again. Each time you do that, then more water evaporates off, and the salt that you initially had in your water, becomes more and more concentrated. And one of the sad end points of that, is that many of our agricultural lands are getting poisoned by build up of salinity. This is a big issue. Another very important issue for our groundwork quality is contaminated sites. I'm from Denmark, and this is a map of contaminated sites in Denmark. And you can see, each stuff on this map, red ones and green ones, they are different types of contaminated sites, represents one contaminated site. There's about 30,000 of them in Denmark. That's to say about one-half of a contaminated site per square kilometer in Denmark. What's a contaminated site? It's something like a former dry cleaning workshop, or it could be a farmer's yard where if been using pesticides and have spilled pesticides on the ground while refilling their farm machinery that would make a contaminated site. And those contaminated sites leaked contaminants down into the sub-surface into the ground. And that's a problem if you want to use the water for drinking water, or for producing your crops. What can you do about that? Well, one thing you can do about it is you can institute groundwater protection. Where you carefully manage land use in your sensitive water catchments, so that's a management strategy. There are also technological solutions. For example, you can do innovative groundwater remediation strategies like the one illustrated on this slide which is all about a thing called enhanced reductive dechlorination. So this is a technology you would apply to a chlorinated solvent contaminated site. Chlorinated solvents come from places like dry cleaners or machine workshops. And if you want to clean those up, one thing you can do is you can encourage the bugs that are in the ground to degrade the contaminants, and how do you encourage that? Well, you can add some substrate which encourages the bugs to grow, and then the bugs will then degrade the contaminant at the same time. So, does groundwater clean up make sense? You can actually evaluate this. I know some very nice tools available from engineering to do this. One of those is life cycle analysis, which allows you to calculate the environmental impact of different technologies. And what we've done here at DTU is compare the environmental cost of cleaning up with some other strategies. For example, here on this slide, we've got the impact, and it's usually measured in person equivalents. And we can see the different impacts here. Long term monitoring, that's to say doing nothing but monitoring the site has a relatively low impact. Whereas, this strategy on the bottom which is to put in place treatment at the drinking water works where you are pulling the water out of the ground. Before you send it out to the consumers you treat the water. And if you're using activated carbon to remove your chlorinated soils you have a big impact. The middle two show the impact of two different remediation strategies. One of them was the one that I introduced on the previous slide. And the other one is a one called in situ chemical oxidization. And you can see that the in situ chemical oxidation has a very big impact. So we might rule out that strategy. But in fact, our enhanced reductive dechlorination is very attractive. It's got less environmental impact than doing nothing except monitoring and that's got substantially less than treating it at the water treatment works. So, what I've done today is I've introduced you to groundwater resources. And some of the challenges we face with that resource. I've shown you that it is a resource that is really stressed. That is to say that it is being depleted all over the world. And I have also shown you two of the main strategies that we can use to protect our groundwater for the future. One is a management strategy. We look, for example, at the water footprint and life cycle analysis, which are two different tools you can use in environmental management to help you find better strategies for managing your groundwater systems. The other solution that we looked at was technological solutions and I introduced several of these. One was the drip irrigation system that we looked at. Another was the enhanced reductive dechlorination strategy. I hope you've enjoyed your video today, and that it's helped you understand a little bit about the issues in groundwater. Thanks very much. Bye!
