okay guys today we're going to talk about the hydrosphere the area of earth that contains our water resources we're going to talk about why it's important to us as a resource we're going to talk about kind of the major processes that occur in the hydrosphere and how human activity can kind of screw things up so first of all you know you know that we're surrounded by water water is such an important substance um you know basically over 70 of the earth's surface is covered with water so it seems like it's ubiquitous and we don't have to worry about it but realize that almost all of it is is contained salt and the problem with that is unless you have special adaptations like marine organisms most organisms are are not evolved to deal with salt the presence of salt and water pulls salt out of our cells so salty water is not really useful for most organisms so even though we're surrounded by water very little of it is fresh water meaning it it doesn't contain a lot of salt and even of that little bit of fresh water a lot of that is frozen which means it's not really available for use so we are surrounded by water but when you think about it not a lot of it is really that useful to organisms it's water is you know something that we don't think about as being that unique but it is chemically actually pretty unique it can hold on to temperature it does it's very stable in terms of temperature change um it it is the universal solvent so a lot of things dissolve in it which means that it can dilute waste and things like that and of course it serves as very very important habitat to a lot of different types of creatures most organisms are at least fifty percent water plants can be up to eighty percent water by weight even humans are more than fifty percent water so it plays a really really important role in even inside the bodies of living organisms water is one of those things that cycles in the natural environment i don't know if you realize this but the amount of water we have on earth is a finite amount we're not getting any new water on earth from anywhere what we have on earth is all that we're ever going to have so it's really important that water cycles and is continually somehow naturally cleaned and purified because the amount of water that we have on earth is a finite amount so the cycling of water in the natural environment is called the hydrologic cycle and the next few slides we're going to talk about how it cycles so let's start with water on the surface of the earth which we call surface water the first part of the cycle that surface water can enter the atmosphere as water vapor and there's two main ways it does that obviously through the process of evaporation which most of you probably know about where liquid water on the surface turns into water vapor now think about is that a free process or does that require energy to go from a liquid to a gas obviously requires energy right so what's the source of energy that enables water to evaporate it's the sun that comes from solar energy hopefully you realize that on a sunny day puddles and things like that will evaporate quicker than on a cloudy day because that process of water turning from a liquid to a gas takes energy and that comes from sunlight the other way that water from the surface goes into the atmosphere as a gas is through transpiration plants like i said are filled with water and they are constantly losing water actually plants basically are coated with wax on the outside of them and that's to keep water inside their bodies but that wax actually prevents plants from being able to take in gases think about what gas is a plant need to be taking in constantly on a sunny day and that would be carbon dioxide right because carbon plants use carbon dioxide to build sugars during the process of photosynthesis so in order to gain carbon dioxide that won't diffuse through the wax that's coating plants so plants have these holes all over the above ground parts and they they're kind of like pores in your skin and on a sunny day plants will open those pores to allow co2 to come in but when those pores are open water vapor will diffuse out of the plant because there's always more water inside of a plant than in the surrounding atmosphere and that process by which plants lose water vapor is called transpiration so that's another way that water goes from the surface of the earth into the atmosphere as a gas now sometimes people just take these two processes evaporation and transpiration and combine them into one term evapotranspiration that's the way that water goes from the surface into the atmosphere as a gas now one thing i want to think about during each of these steps in the hydrologic cycle some steps naturally purify water and some of these steps are steps in which water can become polluted mainly due to human activity so with evapotranspiration is this a step that ends up purifying water or is this a step that would end up polluting water so think about that for a second what do you think well the answer to that is this is a step that ends up purifying water in other words when the water leaves the surface and goes into the atmosphere it becomes purified and that's because anything that's dissolved in water when water evaporates it leaves behind those things that were dissolved in it that's why you could tell where a puddle was after it evaporated because sometimes you can see like you know sediment or salt that's been left on the pavement because anything that was dissolved or suspended in water is left behind when it evaporates so as this water vapor goes into the atmosphere it's naturally purified [Music] okay now it's up in the atmosphere what happens to it as it rises in the atmosphere it actually cools because as you go up in the troposphere the temperature decreases and as this water vapor cools the molecules slow down and they start to stick to each other and that's what we call condensation that forms little water droplets liquid water droplets in the atmosphere and that's where we get clouds from it's just water that has condensated the molecules start to stick together just because they're slowing down as they cool now as you know if these clouds become very saturated with water droplets the water will then fall back to the earth's surface as liquid or frozen precipitation depending on the temperature so think about this is this process of condensation and precipitation is that a process that ends up purifying water or is it are these processes ones that can potentially pollute water and the answer to that is these can be potentially polluting right and it depends on what air pollutants there are present if the air mass is polluted with particulates or even gases that can dissolve into those little water droplets in the in the clouds you guys know this because we talked about acid rain before and acid rain is formed when gases like sulfur dioxide and nitrogen oxides dissolve into water droplets in the clouds and become sulfuric acid and nitric acid so it can be gases that dissolve into the water droplets it can be particulates like ash and soot that actually just stick to the water droplets and they can come down then as polluted precipitation so these processes can be potentially polluting depending on the quality of the air mass now think about where what happens to the water when it hits the ground what's the potential fate of the precipitated water where can rain go when it hits the ground well one thing it can do is it can soak into the soil and that's called infiltration water will soak into the soil and plants can immediately uptake it or if it rains enough that water will soak all the way down through the soil and will meet the groundwater aquifer a groundwater aquifer it's pictured on the on the slide it kind of looks like it's an underground river but but it's not really that it's just a layer of really saturated soil it's underground and it's saturated enough that the water actually flows and think about where that water is flowing to water always flows to the lowest point in the landscape so the groundwater aquifer is flowing towards the oceans that's the lowest point in the landscape so one fate of rain or precipitation when it comes down is it can soak into the soil and that's called infiltration now is infiltration a purifying process naturally or is it one that pollutes the water further in general it's a purifying process and that's because the process of soaking through the soil cleans the water there are microorganisms in soil that can break down pollutants the soil itself acts like kind of like a carbon filter that you could buy you know for your water purifier in your home so infiltration in a natural system is one of the best ways that we have to naturally clean water which means that the groundwater aquifer is a super important resource to us because it really generally contains the cleanest water that we have that we didn't have to invest any energy into cleaning it naturally is clean now infiltration can be polluting if the soil itself is polluted for example if you pour a bunch of motor oil or dump a bunch of toxics in soil then of course it's not going to be it's not going to be purifying but in natural systems infiltration is a process that we use to clean water naturally another thing that can happen to water when it hits land it can either be absorbed by plants we said it can infiltrate through the soil and reach the groundwater aquifer like we said or if the soil gets really saturated the water will run off the surface and it is going to run down hill right so it's going to go to the lowest point in the landscape and the lowest point in the landscape is always another water body so runoff purifying or polluting well obviously this one tends to be polluting even in even in natural systems and that's because anything on the surface of the earth will go will be taken into the nearest water body through the processes of runoff so you know obviously if if we put pesticides and fertilizers or any sort of toxics or litter on the surface of the earth that is very polluting right because runoff is going to take it into a nearest stream or river but even things like pet waste even things like grass clippings or leaves these can all be sources of pollution if enough of that is taken into the nearest water body so runoff is one of our greatest sources of pollution in our local water bodies now what causes the water to run off more we'll talk about that in a second this is just a slide that basically goes through the entire hydrologic cycle what we just talked about it shows water on the surface can be transpired by plants it can evaporate and then it goes into the atmosphere as a gas as that gas cools it can condense in the atmosphere and if it condenses enough and the air mass gets saturated it comes down as precipitation oops um the fate of that precipitation is it can infiltrate reaching the water table or the groundwater aquifer the water table is actually um just a term that refers to the upper limit of the groundwater aquifer in other words if you were digging down from the surface of the soil trying to find groundwater the very upper limit of that groundwater is called the water table so water that precipitates out can either infiltrate we know that that can be purifying um and it can reach a groundwater and that groundwater of course is flowing towards the ocean or if the soil gets saturated it can run off into surface waters and we know that that can be polluting so there are certain ecosystems that play a really important role in the hydrologic cycle they can really affect how water flows through natural systems and those are forests and wetlands so forests play an important role think about this if a water droplet is falling from the sky a raindrop and it hits a forest think about the way that a forest can impact the fate of that raindrop when that raindrop is falling down through a forest the first place it's going to hit are those upper leaves and the tall trees right the canopy of the forest and when a raindrop hits those upper leaves it's going to break it apart into smaller drops basically reducing the erosive force or energy of those drops and as those tiny drops fall down through the forest they get they hit all these different layers of vegetation in the forest breaking them into smaller and smaller bits so by the time the water actually reaches the forest floor it's almost like mist it's like little tiny droplets and that really reduces the power and the force of those raindrops on the surface of the earth which can cause erosion so that's one way that forest can really play a role in the hydrologic cycle reducing the energy of the raindrops and reducing their ability to erode the surface of the earth now think about the raindrop when it actually reaches the forest floor um it can soak into the soil and there's so much vegetation that can that can then assimilate that or absorb it or if the soil gets saturated in a forest and the water starts to run off think of that raindrop running over the surface and all the things that it's going to encounter as it's going towards the normal the the nearest water body it's going to encounter all these different types of plants which will slow down its movement enabling it giving it a better chance to soak into the soil and we know that soaking into the soil is a way to purify water so forests really really reduce runoff they increase infiltration and that can help clean water the same with wetlands wetlands are basically nature's sponges the soil in wetlands is mainly clay-based soils they really hold on to water like a sponge wood and the plants the plant species that live in wetlands are specially adapted to be able to live in saturated conditions water and wetlands hangs around for a long time it just sits in the soil that's why wetlands are wet because they hold on to water think about all the infiltration and all the purifying of water that wetlands do because the water sits in them for so long just enabling it to slowly slowly infiltrate so wetlands and forests play really important roles in cleaning our water the other thing that wetlands do is they recharge the groundwater have you ever wondered you know we talked about how groundwater is such an important resource and that it's very clean and we don't have to spend any energy doing that nature does that itself where do we get more groundwater from we're constantly sucking it out using it in our wells using it for drinking water and irrigation and other things how come we don't run out what where is groundwater new groundwater entering the system well wetlands really play a role in that because of the fact that a lot of water can be stored in wetlands for a long period of time they are constantly adding more clean water to groundwater resources so that's called groundwater recharge and it's a really important role that wetlands play [Music] one thing that we've done so the next several slides is talking about how humans impact the hydrologic cycle and one thing we've done to kind of screw things up is cut down forests and fill in wetlands and that can really impact the hydrologic cycle this map a really old map but it's probably much worse now than it is pictured here but this is the most recent map i could find shows the percent of wetland loss in per state so the numbers you see on the map represent percent of wetland loss so you could see for example california over 90 of their wetlands have been lost and look at this area here all these states with all this wetland loss now what can what can the impact of that be what we see is i mean is that if you lose a lot of wetlands that can cause increased flooding so we fill in our wetlands and then there's a rainstorm and all of a sudden our rivers and streams are overflowing um so that's one of the things that can be caused by filling in wetlands another thing that humans have done to impact the hydrologic cycle is we're starting to pave over the surface of the earth well we're not starting to we've been doing it for many decades but the more we pave over the surface the more that we create these areas where water cannot infiltrate the more that we are impacting the hydrologic cycle so areas of the surface of the earth that do not allow water to soak in are called impervious surfaces it's mainly roads sidewalks rooftops things like that any surface that water cannot soak through is an impervious surface so every time we pave over the earth's surface we're removing an area where water used to soak through the soil and get naturally cleaned so increasing impervious surface is a major major way that we're impacting the hydrologic cycle and increasing polluted water in our water bodies [Music] what do impervious surfaces do well obviously they increase the amount of pollution going into our water bodies because think of all the pollutants that are on these impervious surfaces we've got sediment that builds up we've got you know even trash we've got motor oil drippings all of those things on the impervious surfaces get washed into water bodies when it rains [Music] the other thing that increasing impervious surfaces does that's really damaging is just increases the amount of runoff that goes straight into our local water bodies if you have a you know soil that's saturated when it rains it's going to increase runoff but some of it will get infiltrated so you will still see the levels of water in our streams and rivers rise when it rains but when you have a lot of impervious surface all the water that lands on an impervious surface all of it goes into a local water body when it rains so i know you guys are familiar with the fact that any time it rains for more than about a half an hour in anne arundel county you get flash flood warnings and that's because all of that water is going directly into streams and local water bodies and raising their levels and that that is really bad for the local water body streams are not meant to have these really high flows it can erode their banks and cause all sorts of problems the term watershed refers to an area of land that drains to a particular water body so in this slide it shows the chesapeake bay watershed and you can see how big it is this basically light gray area this whole area here is the chesapeake bay watershed and it's over 65 000 square miles in size and it encompasses many different states new york pennsylvania maryland delaware virginia are all included in the chesapeake bay watershed so what this map shows basically is any water droplet that falls within this light gray area ends up in the chesapeake bay ultimately even water droplets even rain that falls way up here in new york state ultimately makes its way into the bay so this has real implications with trying to keep the bay clean it's not enough for us in maryland and virginia who live right next to the bay to prevent pollutants from getting into the bay it's important that people up in new york and pennsylvania you know make sure that pollutants don't get into the bay and that's a pretty daunting task because i can pretty much guarantee you if you go up to new york and tell people about the bay and try to ask farmers not to spread so much fertilizer they are not going to probably care about that situation they do not maybe even know where the chesapeake bay is so the concept of watershed is very important in protecting our water bodies now here's the thing with it if you think about it in terms of the bay and trying to keep the whole bay clean and having to go to all these states and convince them to not put pollution in the bay that seems pretty overwhelming and maybe impossible to do but the term watershed also applies to all these little tiny streams that lead into our rivers that go into the bay every little tiny stream has its own watershed and cleaning up the watershed around your local stream is not that difficult we can clean up and take care of the watershed that surrounds the stream that goes through our backyards or goes through our church properties or goes through our school properties that's not that difficult to do and looking at this map hopefully you will see that if everybody can clean up their tiny stream and the watershed and care about the watersheds that lead to our bigger water bodies that's a way to get the bigger water bodies clean [Music] okay another way that humans disturb the hydrologic cycle is by taking out and using a lot of surface and groundwater obviously we use water for a lot of different things and that can mess up the hydrologic cycle so let's first look about look at the um main ways that we use surface and ground waters the main way that we use surface waters is for thermoelectric power what does that refer to that refers to remember when we talked about making electricity the main way that we make electricity in the u.s is by heating water producing steam the steam turns a turbine and makes electricity well where do we get the water from we get it from local water bodies we draw out of the bay and local water bodies and that's our source of water to heat for these thermoelectric plants so that's the overwhelming way that we use a lot of surface water in the u.s look at the way that we use most of our groundwater in the u.s irrigation now does that disturb you at all that we use our groundwater for irrigation in the u.s it probably should a little bit and the reason why it's a little bit disturbing that we're using it for irrigation is remember that groundwater is our cleanest naturally clean source of water that we actually don't have to spend energy cleaning it's naturally cleaned by the soil and here we are pumping it out of ground and just spraying it on our crops and a lot of that of course goes as runoff now polluted into our local water bodies so the fact that we use a lot of our groundwater for irrigation is probably something that we may want to think about addressing um then the second largest source is for a public water supply which is drinking water [Music] okay so what can we do to address these problems one is finding alternatives to using water to heat it to produce steam to turn a turbine are there other ways that we can make electricity without doing that and we've already talked about many ways we can do that there's lots of alternatives to that we've talked about solar and wind power can be used to produce electricity we've talked about the hydroelectric use we can use dams to turn a turbine of course we can't we don't have any more rivers left to dam so we don't have any way to expand upon that technology but newer technologies with that involve putting turbines right into waves and having the the wave action turn the turbine so this prevents us from having to boil water removing it from surface waters another way is better irrigation methods now if you ever drive around on the eastern shore of maryland in the summer you'll see that a lot of farmers irrigate with these big sprinklers like this and that's because in maryland we don't really worry about water too much because we have a lot of it but this way of irrigation with these big sprinklers is an extremely inefficient way of irrigating because about on a sunny day about seventy percent seven zero percent of water in a big sprinkler like that evaporates before it even hits the ground so it's a very inefficient way to water our fields and then of course if the soil gets saturated it causes polluted runoff so that's not the best way to irrigate the best and most efficient way is what we call drip irrigation which you can see over here and with drip irrigation they they lay these little tubes they're basically hoses that have a hole in them and where they have holes they have a hole right next to at the base of each individual plant that's where the water comes out so it basically goes right into where the root zone is of the plant very efficient doesn't evaporate really good now the problem with drip irrigation of course is it's much more costly because you have to lay all that tubing but it's a very efficient way of irrigating so it's not just about water use and not using a lot of water so like i said in maryland we don't worry about it too much because we have so much water it's not an arid climate but also think about how much polluted water we're producing so yes we don't have to worry about running out of water but we're just increasing the levels of pollution by irrigating the way we do [Music] responsible landscaping is something that is especially important for the western states where it's arid there's no reason and in fact there's a lot of local laws about kind of landscaping in yards out there there's no reason to have green grass and things like that that's not the natural ecosystems out there they require a lot of water to support if you go out to las vegas it's really dramatic flying over in the plane because basically you'll see just brown landscape for miles and miles and then all of a sudden these bright green spots and those are the huge golf courses that are surrounding las vegas a really irresponsible use of water out there because it requires so much water to support that landscape in that area and this is a way a modern way of recycling water in households that we'll probably see become more common in the next few decades which is reusing gray water so think about in your own home obviously there's a lot of water that we use that becomes polluted during the day right anything that goes into the toilet obviously you flush the toilet that's polluted water that needs to be treated that needs to go to a sewage treatment plant but think about kind of the the water like think about the water after you wash your hands that goes down the sink or after you do the dishes that goes down the sink or after you wash your clothes in the in the clothes washer that water also gets sent to the sewage treatment plant and we haven't talked about sewage treatment plants yet we'll talk about that next time but that requires a lot of energy we're spending a lot of energy cleaning that water and obviously for sewage we it's worth it it's worth the energy investment to do that but for for the water that we just washed our hands with or we rinsed out the sink with that's what we call gray water it's not that polluted and we could actually water our plants with that you could put that on your garden outside um there's no need to it's not polluted enough that we should really be spending the energy sending it to a sewage treatment plant so modern technologies involve having tanks where that recycle that gray water so the water that that comes out of your sink or your dishwasher would go into a special tank you could see it on the slide here and that would be the water that if you want to wash your car it would come out of the gray water tank if you want to water your plants outside or your house plants it will come out of the gray water tank so it solves two problems it's not sending that lightly polluted water to a sewage treatment plant and it you know requiring us to spend so much energy to clean it again and it's also um not using our clean water that we spend a lot of energy cleaning you know the water that comes out of our tap on applications that we don't really need that clean of water for like washing our car or watering our plants so this is a great efficient way to use water [Music] and the last slide the way we can really address a water problem is just try not to use so much clean water you know you can use low flow fixtures and the low flow fixtures now are pretty modern and you know you almost can't even tell that less water is coming out of that fixture compared to one that's not low flow so a low flow fixture means less water is coming out when you turn on the tank they basically aerate the water add some air to it and that means that you know you're basically losing using less water every time you you turn on that particular fixture so you know think about the reason for this again in maryland we don't have to worry about running out of water so it's not really about saving water for the purposes of not using water it's really about how much money do we want to spend cleaning again this water that's going down our sinks and down our toilets it's amount of energy that we're spending to clean it because what happens is it comes out of our taps clean we spent a lot of money cleaning that water it then goes down our sinks and down our toilets to a sewage treatment plant we spend a money a lot of money to clean it there that water from the sewage treatment plant goes back into the bay or back into our local water body and then it goes to a water treatment plant where we suck it out of the bay again spend a lot of money to clean it and it goes back to our tap so it's not really for us here in maryland trying not to use water because we might run out of water it's how much money do we want to spend constantly cleaning this water that is just getting recycled and polluted and recycled and polluted so that's why when you're brushing your teeth turn off the tap while you're brushing and only turn it on to rinse talk to you again soon guys