The Potomac Highlands Watershed School 

A Virtual Stream Sampler: About Watts Branch and Your Score

The Watts Branch watershed is a tributary to the Potomac River with a watershed area of about 22 square miles.  Approximately 6.5 square miles of the Watts Branch watershed is located within the City of Rockville, Maryland.  The mainstem of Watts Branch flows from north to south in the western portion of the City.  Learn more about Watts Branch.

Watts Branch is one of three streams that are monitored by volunteers trained by the City of Rockville Save Our Streams (SOS) Program.  Rockville SOS volunteers are the first line of defense for City watersheds.  They help Rockville by providing information to safeguard and improve the environmental habitat. Volunteers help expand the City’s capacity to study and protect Rockville's environment.

Volunteers attend classes in stream monitoring. They commit to monitoring a stream site twice a year – once in March or April and again in October. The City provides the supplies - collecting nets, field tables, collecting pans and microscopes. Volunteers provide their time and proper footwear.

Stream monitoring is how Rockville creates the Stream Report Card on the condition of its three watersheds – Cabin John, Rock Creek and Watts Branch.  Volunteers, working under the direction of the City's Environmental Division, determine the "grades" by monitoring designated areas of a stream for aquatic insects, chemical contaminants and physical appearance.  You have just virtually sampled on of those three locations. 

Learn more about the Rockville SOS program

 

If you used the other activities in the Benthic Macroinvertebrate Portal prior to using this activity, you should have a good understanding of everything you did in A Virtual Stream Sampler.  If you haven't used those activities, we suggest you run through the Introduction to Stream Sampling to get the basics.  Click here to see a summary of the BMIs you picked in Watts Branch and to see a picture of the BMI "take" that was collected in Watts Branch by CI staff. 

Photographs taken of Watts Branch on June 24, 2012 by CI staff.

Your Score

The benthic macroinvertebrate section is worth 50% of the total score, the other two sections are each worth 25% of final score. 

  • In the benthic macroinvertebrate section, if there are 15 organisms, then finding everything in the net is worth 15 points, and correctly identifying everything is worth 15 points, for a total of 30 points (100%).  You are penalized heavily if you guess at answers on the list and get them wrong.  Every wrong guess is a point off.  Since you have three chances to guess at the answer for each organism before you are forced to use the dichotomous key, with 15 organisms that would be 45 points off.  Yes, you can get a very negative score.  So, if you don't know what something is, don't guess - use the key.  Guessing in the key is not penalized.
  • The habitat section has a maximum score of 5.  Each wrong answer counts off one.  Each question you don't try to answer counts off two.  So you are better off guessing and being wrong than not answering at all.  If you don't guess on anything you can get a negative 100% score in this section.  Ouch!

  • The water quality section has a maximum score of 6.  Each wrong answer counts one off.  Each question you don't try to answer counts 2 off.  So you are better off guessing and being wrong than not answering at all.   If you don't guess on anything you can get a negative 100% score in this section.  Ouch!

  • Even though you can get negative scores in each section, the worst total score you can get is zero. 

The Stream Score

Aquatic organisms can be used as indicators of water quality. The advantage of using aquatic organisms over chemical indicators - such as the amount of a certain chemical in a water sample - is that animals are constantly "sampling" their environment.  The communities of organisms found in benthic samples are indicative of water quality conditions over time. Chemical measures, in contrast, provide a momentary snapshot of conditions in a constantly changing environment. 

Many years ago, the focus was on "indicator species."  An indicator species is one that, by its presence, absence, or abundance relative to other organisms, indicates environmental conditions. For example, the presence of numerous  non-biting midge (Chironomidae) larvae in a stream may indicate severe organic pollution.

Over the years, researchers generally moved away from the use of individual indicator species and toward "metrics" that look at groups of species. A typical metric might look at the total number of different species or the relative abundance of different species. For instance, if a researcher finds that species tolerant of degraded water quality outnumber kinds that are intolerant of pollution, it is more likely that degraded conditions exist  But the mere presence of pollution-tolerant organisms does not necessarily equate to water quality problems, because these organisms are often widely distributed.

A Virtual Stream Sampler scores the stream using two popular methods in use by volunteers in the Chesapeake Bay Watershed, the West Virginia Save Our Streams Stream Score Index, and Virginia Save Our Streams Stream Score.  Both of these scores are based on a suite (a group) of "metrics" that, when averaged together, are an effective way to tell a stream's story.  Two metrics are used by both West Virginia and Virginia:

  • percent tolerant organisms tells you what percentage of the organism in the sample are tolerant of pollution, and

  • Virginia's percent Mayflies, Stoneflies, and most Caddisflies is similar to West Virginia's % EPT score.  This score looks at what percentage of the sample consist of theswe three groups of insects that are mostly sensitive to pollution.  Virginia's score breaks out the pollution tolerant "common netspinner caddisfly."

The two tables below provide details on each system, and links for more information. 

Virginia SOS Stream Score

Metric

Your Metric Score

Good (2)

OK (1)

Poor (0)

% Mayflies, Stoneflies, and Most Caddisflies

X%

> 32.2

16.1 to 32.2

< 16.1

% Common Netspinner

X%

< 19.7

19.7 to 34.5

> 34.5

% Lunged Snail

X%

< 0.3

0.3 to 1.5

> 1.5

% Beetle

X%

> 6.4

3.2 to 6.4

< 3.2

% Tolerant Organisms

X%

< 46.7

46.7 to 61.5

> 61.5

% Non-Insect Organisms

X%

< 5.4

5.4 to 20.8

> 20.8

Get details on how the Virginia Save Our Streams Score is calculated and learn much more about the Virginia program.   

Total # of 2s:

Total # of 1s:

Total # of 0s:

N2

N1

N0

Multiply by 2:

Multiply by 1:

Multiply by 0:

N2 x 2 = S2

N1 x 1 =S1

N0 x 0 = S0

Now add the 3 subtotals (S2 + S1 +  S0) to get the Save Our Streams Multimetric Index Score

_____ Acceptable Conditions (9 to 12)              

_____ Conditions cannot be Determined - Gray Area (8)               

_____ Unacceptable Conditions (0 to 7)                       

 

West Virginia SOS Stream Score

Metrics

What Values Mean

Best Standard Value (BSV)

Scores

1.  Total Taxa

Higher is better

22

Your Value/BSV x 100

2.  EPT Taxa

Higher is better

13

Your Value/BSV x 100

3.  Biotic Index

Lower is better

3

(10-Your Value)/7*100

4.  % EPT Abundance

Higher is better

90

Your Value/BSV x 100

5. % Tolerant

Lower is better

2

(100-Your Value)/(100-BSV)*100

6.  %Dominance

Lower is better

20

(100-Your Value)/(100-BSV)*100

Stream Score Index (SSI)

Average of the above scores

Reading the WV SOS Stream Score table: 

 > 85 = Optimal, 85-70 = Suboptimal, 69-50 =  Marginal, < 50 = Poor

 

The West Virginia Save Our Streams Program has three levels of stream sampling methods for volunteers to choose from.  All of them require training and volunteer certification by the state volunteer coordinator for their data to be accepted.  Level I requires the least technical expertise, Level III the most.   The Stream Score above is a hybrid of the Level II and Level III scoring (we wanted to add in percent Dominance), and similar to the professional level West Virginia Stream Condition Index.

  • "Total Taxa" = how many kinds of BMIs were found.  Higher values are better, 22 would be a very good stream.

  • "EPT Taxa" = how many kinds of Mayflies (Ephemeroptera), Stoneflies (Plecoptera), and Caddisflies (Trichoptera) were found.   Higher values are better, 13 would be a very good stream.

  • "Biotic Index" = the Hilsenhoff Biotic Index, that multiplies abundance of each organism by its sensitivity to pollution (ranked from 1-most sensitive  to 10 - least sensitive), and divides the sum by the total number of organisms caught.   Lower values are better, 3 would be a very good stream.

  • "% EPT Abundance" = how many Mayflies (Ephemeroptera), Stoneflies (Plecoptera), and Caddisflies (Trichoptera) were found.   Higher values are better, 90 (out of a total of 200 organisms) would be a very good stream.

  • "% Tolerant" = the percentage of the total number of organisms that were caught that are tolerant of pollution.   Lower values are better, 2 would be a very good stream.

  • "%Dominance" =  the percentage of the most abundant organism in the sample out of the total number of organisms caught.   Lower values are better, 20 would be a very good stream.

You can learn much more about the West Virginia SOS program, and even download spreadsheets for calculating your own stream scores.  

 

The BMIs of Watts Branch, Rockville, Maryland

Collected June 14, 2012 by N Gillies and B Alexandro (Cacapon Institute)

Sorted and identified 8/6/2012 by WNG; 1/8 of total sample

Caddisflies

 

Common Netspinner

88

Fingernet

54

Mayflies

 

Small Minnow

2

Beetles

 

Riffle, larva

111

Riffle, Adult

1

Crane Fly

7

Chironomidae

46

BlackFly

1

Asian Clam

6

Crayfish

2

Flatworm

3

Aquatic worms

11

 

You might like to try entering the above BMI data into the Virginia or West Virginia spreadsheets to calculate the BMI Index Score for yourself, or try it using other state's volunteer and professional scoring methods.  Do they all give the same answer?  If not, how do they differ?  

 

The picture below shows what the BMIs collected in Watts Branch look like sorted out in a petri dish.

 

 

The Potomac Highlands Watershed School 

A Virtual Stream Sampler

This web page is an informational component of the "A Virtual Stream Sampler" activity that simulates a volunteer stream assessment.  It is just one component of the Potomac Highlands Watershed School's watershed science and society curriculum, and is best used when accessed from within an eSchool classroom.  If you reached this page via a direct web-link, you might consider going to the Potomac Highlands Watershed School and visiting an eSchool classroom to use the Virtual Stream Sampler and other activities, review the literature in the bookshelf or, if you are a teacher, visit the "Teacher's" room and check out the lesson plans.