How Hydrology Works

Hydrology is the study of the flow ofwaterthrough the hydrologic cycle, and水文学家是people conducting the research. While most people don't think much about water, hydrologists examine every aspect of it -- where it comes from and in what quantities, where it goes, how it gets there and what happens to it in the process.

To do this, they use a lot of math and some really cool gadgets, and they even get a little wet sometimes. The results are astounding. Hydrologists help designers and engineers construct dams and levees to keep towns safe from flooding, track pollution and find new water sources -- they even help track water

in space.

Because water is everywhere and is so critical to nearly everything we do, hydrologists span almost every branch of science, from physics and geology to astronomy and ecology. There are so many ways to study theEarth'swaters; here are just a few.

Spatial hydrologyis the study of the movement of the waters of the Earth through the hydrologic cycle using a spatial database developed in a geographic information system (GIS). This means that they try to connect the varying space that is the land with the varying time and flow that is the water

[source:Purdue University].

Hydrogeology, orgroundwater hydrology, tracks the flow of water through the soil and into underground systems.Hydrogeologistshelp find underground sources of water (aquifers) that we can tap into for drinking water. They monitor these, as well as the flow of water into underground sites to determine how much is taken out. They also figure out how water flows through soil. This may sound boring, but if you're a farmer who needs the right amount of soil moisture to grow your crops, it's vital information. Hydrogeologists help with irrigation practices and monitor pollution that seeps down through the soil into our wells.

Vadose zone hydrology是水文地质学的一个子集,侧重于洛杉矶吗yer of earth directly above an aquifer, called the vadose zone. This zone is important because it acts as a final filter and aeration device before rain becomes groundwater, which is sometimes taken straight from the ground through wells and used without purification methods. If the vadose zone is unhealthy, so is much of our drinking water.

Hydraulicshas nothing to do with making your car do really cool tricks (well, it does, just not in this context). This is the study of the physical flow of water. Hydraulics professionals use mathematical modeling to track the flow of water from one source to another. The major purpose of this is to track not the water but contaminants in it. For example, if a factory is dumping industrial waste into a river, it will flow downstream and eventually get dispersed into the ocean. Who knows where it will end up? The people who study hydraulics do.

Hydrometeorology, also known ashydroclimatology, uses meteorological instruments to figure out how much rain will fall and in what specific areas. This is useful for many reasons -- not just so you know when to take your umbrella when leaving the house. Hydrometeorology can help determine how much water will reach one area in a given year. This helps with the building of flood-control devices and

irrigation systems.

In a form of science known asdendrohydrology,dendrohydrologists利用树木年轮来帮助确定historical rainfall and drought conditions, stream flow, runoff, and much more. Knowing this information can help regions without reliable historical records predict the hydrological future.

If the world's water supply contains the same amount of water today as it did in the beginning, then how is it possible to waste water? Won't it just come back? Why do people fight over water? Find out on the

next page.

While theEarthstill has the same amount ofwaterit has always had, the demand for water is greater than ever. The population keeps growing, and everyone needs to be fed and clothed with materials that have to be grown using water. The same people need to live in houses built with steel, lumber, or other various building materials -- again, these materials take a large amount of water to manufacture or grow. Of course, people also have to bathe and wash their clothes and go to the bathroom … all of this

takes water.

You want to know the real kicker? Water doesn't fall evenly over the entire Earth. One place may get too much rain, causing洪水and devastation, while another might get very little, causing a drought. Once the water goes down the drain, it takes a while for it to be processed back into something that can be used again. If there is not enough rainfall for your area and the population uses too much water, the reserve levels go down faster than they can be replenished.

水文学家are constantly looking for ways to find more water to keep up with current demands. Water treatment facilities take the water that has been used for waste and turn it back into fresh, local water that can be consumed again. Hydrologists not only look for ways to improve these facilities, they also try to find new underground wells of water and, perhaps even more importantly, figure out how to maintain these supplies with the ever-growing threat of pollution.

Pollution is industrial waste, emissions from cars, runoff of pesticides and animal wastes from farms, and extra nutrients in the soils that cause an imbalance. These can run into lakes, rivers and streams; seep into the groundwater; or collect in the air and fall back to the ground as acid rain. Mapping the course of these contaminants through environmental hydraulics is one way hydrologists help locate and clean

污染物。

Another way is through innovations like permeable pavement materials. When rain falls, it sometimes contains pollutants. In places with a lot of people, like most cities, there also tends to be a lot of concrete. This washes out all of the pollutants on the road and puts them into the nearest sewer, drain system or river, which overflows with water and has no place else to go. Concrete is impermeable -- it won't allow water to pass through it into the ground. This poses a problem, because filtering the pollutants out with rocks and sand is the first natural water filtration system for our groundwater.

One answer to this problem may be permeable concrete. This surface allows water to pass through it, sort of like soil. It takes the pressure off of the sewage systems in urban areas where all of the water and waste have to drain during a big rain. It also helps with flood control as well as pollution control. The costs, however, are sometimes prohibitively high. Digging up streets and replacing the concrete is no small task. The best way to begin the process of permeable planning is to start during the planning phase of a project.

This is just one of the many ways hydrologists work to keep our ground water safe. Other hydrologists research pollution levels in snow, soil and even glaciers.

On the next page, find out how hydrologists can predict, and sometimes even prevent, floods.

Anyone who has ever experienced aflood或known someone who has understands that floods are serious business. They can take out entire communities and level hundreds of years of history in just seconds.

Some floods can arrive suddenly -- these are calledflash floods或critical floods. Sometimes it doesn't even have to be raining anywhere nearby for a flash flood to occur. Flash floods can happen when a heavy rain occurs upstream and thewaterflows downstream, gathering more momentum as it passes. Another type of critical flooding happens when some sort of flood-retention device, like a dam orlevee, breaks and water rushes out.

Non-critical floodsare floods that happen slowly, over a relatively long period of time. These occur when heavy rains fall for days on end, and rivers, lakes and streams swell past their normal boundaries. Don't let the name fool you -- non-critical floods can be just as devastating as flash floods if they're not prepared for, and they can lead to critical flooding as well.

水文学家work constantly to prevent and lessen the severity of floods.Hydroclimatologistsuse rainfall data and meteorological technology to help determine the maximum rainfall for an area. They then try to determine when floods might occur and how much rain it would take to flood an area.

With this information, hydrologists work with organizations, like the United States Federal Emergency Management Agency (FEMA), to help plan city development and emergency response. This is based on the idea that a major flood happens once every one hundred years. A hydrologist's goal is to figure out what the worst flooding possibilities are for a span of one hundred years and design around that possibility to minimize the harm and the cost of rebuilding. Sometimes, if the cost to build a flood device to one-hundred-year flood strength is much more than the cost of rebuilding, engineers will build for the possibility of a 25- or 30-year flood -- the worst possible flood that might happen every 25 to 30 years. This usually happens in remote areas, like parks or forests, where there are not a lot of people who might

be affected.

The work of the hydrologists determines where and how to build not just flood devices like levees, dams and culverts, but also where to put entire cities and neighborhoods. Safety is what's most important. Successful flood control is not always apparent, but unsuccessful attempts are far too obvious.

Some hydrologists go to the ends of theEarthto study the water system -- some go even farther. Find out how far some are willing to go on the next page.

水is everywhere, but it's not always reachable. Hydrologists use models, maps and figures to help them distinguish where the water is -- underground aquifers and remoteglaciersare no match for a well-informed hydrologist.

Spatial hydrologistsuse GIS (global interface systems) andGPS(global positioning systems) to help them map streamflow, pollution and various environmental problems. These can look like anything from a line graph to a full-scale 3-dimensional model of a river or underground water system. These high-tech systems make use of coordinates, measurements and data to generate detailed pictures of the area.

水文学家will go pretty far to get information on the movement of water. Remote sensing satellites orbit theEarth, taking pictures of the oceans and what's happening in them. Thesatellitesproduce topographical maps of the ocean, which help hydrologists study the oceans and their movements as a whole. There's even acoral-reefremote sensing tool. Reefs are a great ecological resource, helping to produce oxygen and keep an environmental balance for the entire planet. Knowing where these reefs are and how to study them is very important.

Parametric hydrologyis a more theoretical branch of hydrology. It uses computer modeling to come up with relationships between events in the hydrological cycle. It then uses these relationships to generate possible new events.

Overall, hydrologists are a large and diverse group. They are dedicated to the preservation of the Earth's water by any means necessary. Hydrologists help maintain the livelihood of mankind by helping to regulate floods, pollution and sewage. Not only that, they get to make some really fascinating models. Hydrology is a branch of science that will always be in demand, especially as our population continues to grow and the demand for fresh water increases.

To learn more about the water that's all around us, follow the links on the next page. They'll provide you with more information.