Lesson 3_ Watersheds

7/11/2014 Lesson 3: Watersheds

http://water.me.vccs.edu/courses/ENV110/Lesson3_print.htm 1/11

Lesson 3:

Watersheds

Objective

In this lesson we will answer the following questions:

What is a watershed?

Why are watersheds important to water/wastewater treatment plant operators?How is contamination in water affected by the distance from the contamination source?

How do we find the boundaries of a watershed on a topographical map? What problems in a watershed should a plant operator be aware of?

Reading Assignment

There is no set reading assignment for this lesson. However, you should use your textbook to

clarify your understanding of watersheds.

Lecture

The Importance of Watersheds

What is a Watershed?



By definition, a watershed is an area where all rainfall collects into a common location. The

common location could be a stream, a pond, a river, etc.

Smaller watersheds flow into increasingly larger watersheds. For example, Mountain EmpireCommunity College contains three small watersheds. All three watersheds eventually flow into the

Powell River, so they are all part of the Powell River watershed, also known as the Powell Riverbasin. The water in the Powell River ends up in the Gulf of Mexico, so Mountain Empire

Community College is also in the Gulf of Mexico's watershed.

The headwaters of a river are made up of first order streams. The watershed of a first order stream

cannot be broken down into smaller watersheds because water feeding first order streams flowsdirectly into the streams. The water may originate as runoff from rainfall or as groundwater welling

up from below the earth's surface.

Each watershed has its own unique characteristics. Size, permeability of the soil, vegetation type,soil type, slope, microorganisms, pH, DO (Dissolved Oxygen), and temperature all affect the water

in a watershed. As you will see, each watershed also presents its own problems for the watertreatment technician.

Potable Water Treatment



There are many possible sources of contamination in a watershed. Septic tanks, airports,

automobiles, industrial facilities, mining operations, and agricultural lands all contribute to thecontamination. In addition, various other sources and processes contaminate the water supply.

We are not as concerned about the microbial contamination of the water supply in potable water

treatment as we are about other types of contamination. Bacteria are killed or removed during thewater treatment process as we flocculate, filter, and disinfect the water. But knowing the amount

and type of contamination in the treatment plant's watershed can influence how much chemicaltreatment (usually alum and lime) is necessary to produce floc from the water.

Every watershed has different characteristics - different colloids, different pH, and so forth. Theonly thing that is common in water treatment with respect to a watershed is that every watershed is

unique. So the reason we are interested in the front end of a watershed is to determine how best totreat the water.

Waste Water Treatment

Why are we interested in the sewage treatment end of a watershed? Communities must release

treated sewage into streams and rivers. In addition to meeting standards set by the EnvironmentalProtection Agency (EPA), waste water treatment facilities must also consider where the released

water is going.

There are often endangered species, such as mussels, and other organisms of concern in the

streams below waste water treatment facilities. We have to be sensitive to life downstream as werelease treated sewage water into our watershed. The wastewater treatment facility strives to

maintain the health of the downstream ecosystem.

Our watershed also becomes the watershed of another water treatment facility somewheredownstream. That facility will be concerned about what we're putting into their watershed for

treatment purposes just as we're concerned about the waste water treatment facilities upstream. Sowatershed is an important concept within both water treatment and sewage treatment.

Boundaries

Watershed Boundaries and Contamination



How do we know the boundaries of the watershed? Edges of a watershed are usually found in the

highest areas around. There, water falling as rain on one side of the mountain or hill runs down into

one watershed while water falling on the other side of the mountain or hill runs down into anotherwatershed.

As I mentioned previously, there are three watersheds on the property at Mountain Empire

Community College in Big Stone Gap, Virginia. All three watersheds eventually empty into thePowell River. If there is contamination in one watershed and none in the other two, contamination

still reaches the Powell River.



But the contamination in the Powell River will be more dilute than it was in the source stream. The

further we go from the source of contamination, the less concentrated the contamination will

become until it is an insignificant component of the water running into the Gulf of Mexico.

The total amount of contamination in the water is about the same when it reaches the Gulf of

Mexico as it was when it left the source stream. But there is so much water in the Gulf of Mexico

that the contamination becomes very diluted. You can see the same effect if you put a few drops ofred dye in a small cup of water. The water is quite red. But if you pour the cup of water and dye

into a gallon container of water and mix it up, the water only shows a faint hint of red color.

Another example of the effect of distance and greater volume on dispersing contamination is a

sneeze. When you sneeze, germ and water particles are initially very concentrated just outside your

nose. But as they are blown further from your face, they disperse into the surrounding air and

become much less concentrated. There is so much air around you for the germ and water particlesto disperse in, that the contamination becomes insignificant.

We're interested in defining an area's watershed so that we can find potential sources of

contamination to our facilities. We also need to be sensitive to downstream life when releasingpollutants into the water. As we consider sources of contamination in the watershed, we have to

keep in mind the effect of distance on the concentration of the contaminant in the water.

Defining Watershed Boundaries on a Topographical Map



Let's define watershed on a topographical map (also known as a topo map). First, you need to

know how to read the map.

The scale is usually found at the bottom of a paper map, but on the website mentioned later, the

scale is found at the top of the map. A typical scale is 1:24,000 meaning that every inch on the map

is equivalent to 24,000 inches on the ground. An arrow at the bottom of the map points tomagnetic north.

A topographical map shows differences in elevation by a series of contour lines. You can think of a

contour line as a trail for a lazy hiker who never wants to climb up or down. Instead, he just walks

around the side of a hill at the same elevation.

On topo maps, contour lines usually show a difference in elevation of forty feet. So, the lazy hiker

on one contour line is forty feet higher or lower in elevation than the lazy hiker on the neighboring

contour line.

Hilltops are easy to find on topographic maps because they are shown as closed circles. The lazy

hiker can walk around and around the top of the hill on the same elevation. In contrast, streams are

usually shown as Vs with the point of the V being the upstream end.



When examining a topo map, you will need to orient yourself by finding known objects. Look for

peaks (which are often labelled by name), buildings (shown as small squares), churches,

graveyards, etc. Labelled roads can also help you get your bearings.

Once you are oriented, find the point you are interested in. Continuing with the sample map shown

above, I have highlighted Creek X. Now you can begin to define the area's watershed

boundaries.



Starting at the creek, go uphill in every direction (except directly downstream) until you reach thehighest points. Sometimes the highest point above the creek may be a peak, shown as a closed

circle. Other times, the highest point is a ridge, shown as an elongated U- shape. In any case, on

the other side of these highest points, a new watershed begins. Connect the highest points around

the creek with a line and you have drawn in the watershed boundary. This line also marks the

headwaters of the watershed.

Your Watershed

Try finding the boundaries of the watershed in which you live or work. If you do not already have a

topo map of your area, go to http://www.topozone.com/ and type in the nearest city and state in the

"Place Name Search" area.

If you are working from a map on topozone.com, you may want to change the scale so that you

can see the entire watershed region once you find the topo map of your area. Starting at the scale

of 1:200,000 or 1:100,000 will let you orient yourself and define the watershed boundaries if youare considering a large watershed. Then change the scale to 1:25,000 so that you can see regions

in the watershed which might affect the water quality. Which areas do you think are sources of

contamination? Which areas do you think release clean water into your stream, river, or lake?

Watershed Monitoring

Aquatic life in our lakes and rivers is a good indicator of how successful our efforts are at keepingthe water clean. Many organisms are unable to survive in contaminated water.

We can also monitor the cleanliness of water directly by testing the concentrations of various

pollutants in the water. The Department of Environmental Quality (DEQ) is the agency that

monitors watersheds. They analyze data at stations set up in different areas.

Responding to Contamination in Your Watershed

As a plant operator, you need to have an understanding of what potential sources of contamination

are contained within your watershed. Without this knowledge, you won't be able to respond

adequately to problems as they arise.

The watershed that feeds Greenville, Tennessee, goes through an industrial area that had an acid

spill. A hose carrying sulfuric acid burst and emptied the contents of the tank car into the river.

http://www.topozone.com/



The water operator that was on duty noticed that the pH of the water coming into the plant was

dropping.

The first thing the operator did was to shut the plant down. He was able to guess that the acid

came from a spill in the industrial area even though no one at the company there had noticed the

problem. So the operator called the other water treatment plants downstream of the spill area to let

them know about the contamination.

You never know when a tank car will overturn and spill a contaminant into your watershed.

Usually the amount of time that you will have to respond to such a situation is not what you would

like it to be. What's a reasonable amount of time to be able to respond to a problem? Time

enough to prevent irreversible damage or expensive correction. The people who are responsible

for water treatment facilities want an operator who is on his toes to catch problems as they come

down the stream, an operator who will take appropriate action or shut the plant down, if

necessary. This prevents cleanup cost and problems with treated water.

Knowing your watershed can also help you prevent problems before they occur. What would do if

you found many diseased or dead animals in your watershed? You wouldn't want dead animals in

the water that you were treating for consumption. Without knowing the boundaries of your

watershed, you would unable to stay on top of these problems.

Other Watershed Problems

You may wonder, What's the likelihood of anything in the watershed ever creating a problem

anyway? Don't we floc, filter, and chlorinate the input water, thus eliminating almost any problems

in the output water?

Despite all of that filtration, certain organisms are able to pass through a filter. Cryptosporidium is

one example. Cryptosporidium is a parasite often found in the intestines of livestock. The parasitecontaminates water when the feces from the animal interact with a water source. In a healthy

population, human infection results in acute diarrhea, which lasts for 2-3 weeks. But the parasite

can be life threatening for people who suffer from suppressed immune systems such as AIDS

patients, children, and the elderly.



Cryptosporidium

Since filtration and chlorine are ineffective in treating water contaminated with Cryptosporidium, the

Environmental Protection Agency (EPA) requires that all public water supply systems serving more

than 100,000 connections must monitor for Cryptosporidium. Although we are unlikely to have

Cryptosporidium in our watershed, some of the larger cities with larger watersheds might. Plant

operators have to test the water flowing into their plants to determine which contaminants might be

a problem.

When monitoring a watershed, we take into account the accessibility of the area. People can enter

the watershed at Appalachia along only one road, so sources of contamination there are relatively

easy to monitor. In contrast, the Big Stone Gap watershed is accessible by two roads and fishing is

allowed in the reservoir by permit only. So monitoring the Big Stone Gap watershed is a little bit

more complicated. The more public access a watershed has, the more potential there is for

hazard.

One last concern of watershed maintenance is diversion of the water for other uses. As water gets

diverted from a watershed, there is less water for contamination to be diluted in. There is also less

water available to be used by the communities downstream.

Review

Watershed is a very important concept for water and wastewater technicians. The watershed in

which a plant is located determines the purity of the water flowing into a plant. Plant workers must

also be aware of the downstream ecology and human communities which are influenced by the

water they release.



The technician needs to know the watershed's boundaries in order to determine potential sources of

contamination. He should also know how contamination flows through a watershed, influencing all

downstream watersheds but becoming more dilute as the distance from the contamination source

grows.

The technician who understands his watershed will be able to respond to problems quickly and

efficiently. He will know when to shut the plant down, when to warn other treatment plants, and

when to merely adjust the operation of his plant.

Assignment

Send the following assignment to the instructor:

1. View the following topo map section and print it out.

2. Mark the boundary of the watershed directly on the map. (There is one definite watershed,

but find the other one on the map for 5 bonus points)

3. Mark the body of water into which the water from your watershed flows - a reservoir, river,

creek, pond, etc.

Quiz

Answer the questions in the Lesson 3 quiz . When you have gotten all the answers correct, print

the page and either mail or fax it to the instructor.

http://water.me.vccs.edu/courses/ENV110/assignment3.htm

http://water.me.vccs.edu/courses/ENV110/quiz3.htm

Lesson 3_ Watersheds

Documents

Transcript of Lesson 3_ Watersheds