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UA / Environmental Science / ENSC 4023 / What is the river continuum concept?

What is the river continuum concept?

What is the river continuum concept?


School: University of Arkansas
Department: Environmental Science
Course: Water Quality
Professor: Brad austin
Term: Fall 2016
Tags: Pathogens, fisheries, TMDL, reservoirs, and diversity
Cost: 50
Name: Water Quality Exam 3 Study Guide
Description: This is the filled out study guide for Exam 3 with all the correct answers! This is everything that Dr. Austin said would be on the test.
Uploaded: 08/29/2016
11 Pages 123 Views 2 Unlocks

ENSC 4023

What is the river continuum concept?

Water Quality

Dr. Brad Austin

University of Arkansas

Exam 3 Study Guide 

River Continuum Concept: In a river, from headwaters to mouth, the physical variables in a stream  (width, depth, velocity, stream order) create a gradient of physical conditions, creating a continuum of  biological features in the river, such as energy input, organic matter transport, and macroinvertebrate  functional feeding groups.

Shredders: tear and eat coarse particulate organic matter (CPOM) for nutrition from microbial  colonizers.

∙ Example: Crayfish

∙ Analogy: “Peanut butter on a cracker”

o Peanut butter = microbial biofilms  

o Cracker = leaf

What is maximum sustainable yield? what are some problems with using msy to manage a fishery?

Don't forget about the age old question of How does the nervous system operate?

o The shredders get more of their nutrition from the microbial biofilm (PB) than from the  leaf (cracker)

Scrapers: “Grazers” of biofilms and benthic algae

Collectors: Filter fine particulate organic matter (FPOM) from water flowing by  ∙ Example: Simulidae (Black fly)

∙ Some collectors use nets, others use webs

∙ Collectors produce feces which is also FPOM, and is sometimes bigger than the FROM they  consume  

Predators: Eat other invertebrates

∙ Predators are common throughout almost every food web Don't forget about the age old question of What is an argumentative structure?

Shredders, scrapers, collectors, and predators all produce FROM in the form of feces! Richness: the total number of different species per area

What are the three components of a fishery?

Evenness: how well the total number of organisms are spread between the total number of species  (how equally represented)

Evenness = H′/lnS

It is ideal for both the species richness and species evenness to be high in an ecosystem.We also discuss several other topics like What is octet rule in chemistry?

Shannon-Weaver Diversity: a quantitative measure of diversity in a community which takes into account  richness and evenness of species. Theoretically, the diversity index can be used to compare diversity  between ecosystems

Alpha Diversity: within-habitat diversity (example: riffle in a stream)

Beta Diversity: between-habitat diversity (example: between 2 riffles)

Gamma Diversity: entire landscape diversity (whole stream)

A-D and E-H have the same overall diversity (gamma diversity).

E-H has greater alpha diversity (within ponds).

A-D has greater beta diversity (between ponds).

Playa: Round hollows in the ground created by wind scour that are filled with water (relatively small ) If you want to learn more check out What are 3 major components of the criminal justice system?

Maar: Low relief volcanic crater created by the explosion of groundwater when it comes in contact with  lava

If you want to learn more check out What is meant by production possibility frontier?

Graben: parallel faults which caused the displacement of a block of land downward. This can sometimes  form a lake (examples: Lake Tahoe and Lake George)

Oxbow: Occurs when a river cuts a channel and leaves behind a cut off meander

Reservoir: Mostly man-made impoundments of rivers  Don't forget about the age old question of How quickly an enzyme becomes saturated?

∙ Some are natural

∙ Quake Lake is a natural reservoir (formed by a land slide)

Biodiversity: total variety of organisms found within a defined area

∙ High diversity = good condition

∙ Low diversity = poor condition

Biological indicator: a species whose population can reveal the condition of the community ∙ Good Indicators: taxa with narrow and specific tolerances

∙ Poor Indicators: taxa with wide tolerances to disturbances

% EPT = % of Ephemeroptero (may flies), Plecoptera (stone flies), and Trichoptera (Caddisflies) which are  present out of the entire community sampled  

o E = Ephemeroptero (may flies)

o P = Plecoptera (stone flies)

o T = Trichoptera (Caddisflies)

These taxa are the most likely to be impacted by changes in water quality because these species are  sensitive to decreases in DO, fluctuating pH, and high temperature.  

The greater the percentage the better the quality of water; the %EPT is used to compare impacted sites  versus un-impacted sites

Example: Calculate the %EPT for this community


# of individuals within each family















Total: 403

25 + 50 + 15 = 90

(90/403) = 22.3%

Invasive Species: plants, animals, or pathogens that are non-native to the ecosystem and whose  introduction to the ecosystem causes or is likely to cause harm

Stock: the abundance of a species of fish

Yield: the total amount of fish captured

Maximum Sustainable Yield: the largest yield, or catch, which can be taken from a species stock over an  indefinite period. In most fisheries this is around 30% of the population size. However, this approach  ignores the size, age, and reproductive status of the fish which are taken, which has led to the collapse  of many fisheries

Functional Bio-indicators: consists of a systems capacity to process organic matter or cycle nutrients ∙ Decomposition rates

∙ Primary production and respiration (whole-stream/lake metabolism)

∙ Nutrient cycling

∙ Nutrient spiraling (a stream or reservoir concept): the water is moving downstream and taking  nutrients with it

o Uptake and turnover velocities  

Structural Bio-indicators: consists of identity and enumerating organisms in a system ∙ Macroinvertebrate community composition

∙ Algal community composition

∙ Fish

∙ Individual organisms  

o E. Coli

o Cyanobacteria

Pathogen: infectious agents that can cause disease

Total Maximum Daily Load: load of a contaminant that can enter a waterbody and the waterbody still  meet WQ standards to protect designated uses


1. What is the River Continuum Concept? Be able to describe concisely the changes that occur in a  river network as you move from headwater (low order streams) to large river (high order streams)  with respect to abiotic conditions, basal food resources and macroinvertebrate communities. 

River Continuum Concept: In a river, from headwaters to mouth, the physical variables in a stream  (width, depth, velocity, stream order) create a gradient of physical conditions, creating a continuum  of biological features in the river, such as energy input, organic matter transport, and use by  macroinvertebrate functional feeding groups.

As the river network moves from lower order streams to higher order streams, the stream channel  becomes wider and deeper, and the canopy cover decreases.

In first through third order streams there is high amounts of allochthonous organic matter (organic  matter from outside the stream order), and shredders and collectors dominate while there are few  predators and grazers.

In fourth through sixth stream orders, there is greater amounts of autochthonous organic matter  (organic matter from inside the system – generally algal biomass), and grazers and collectors  dominate while there are few shredders and predators.

In seventh order streams and larger, there is both autochthonous and allochthonous organic matter,  and collectors dominate with few predators.

2. Be able to calculate alpha diversity using the Shannon-Weaver equation for a data set. 

Pi = Number of a particular species/ total number of organisms (10/33=0.303)




ln (Pi)































H′ = 1.157

3. Compare and contrast the Riverine zone, Transitional zone and lacustrine zones for reservoirs. Be  able to compare how water clarity, basal food resources, sediment type, and flushing rates change  between zones. 

Narrow, channelized basin

Broader and deeper than  the riverine zone

Broad and deep (lake-like)  basin

Relatively high flow and  flushing rate

Decreasing flow and  

flushing rate

Little flow and low flushing  rate

High suspended sediments:

Decreased suspended  

solids and turbidity

Low suspended solids (clear)

low light availability at depth

light availability at depth

high light availability at depth

High nutrients (nutrient supply  by advection)

Advective nutrient supply  is decreasing

Diffusive nutrient supply  (nutrient supply is from  

internal cycling); low nutrients

Low macrozooplankton  

growth < flushing rate  

light limited primary  


Relatively high  

phytoplankton primary  production

High Macrozooplankton  

growth > flushing rate  

(nutrient-limited primary  productivity)

Higher DO over sediments  (cell losses primarily by  


Cell losses by grazing and  sedimentation

Fine benthic organic sediments  (cell losses primarily by  


Primary organic matter source  is allochthonous

Organic matter comprised  of both autochthonous and  allochthonous matter

Primary organic matter source  is autochthonous

Stratification does not occur in  this zone

Stratification occurs in this  zone

Stratification occurs in this  zone

More eutrophic


More oligotrophic

Allochthonous Organic Matter: from the watershed

Autochthonous Organic Matter: from within the lake or river

4. Briefly describe the different stages in the life and death of a reservoir. 

1. Impound a river and the valley fills with water

2. Influx of inorganic sediments, and this begins to fill the lake. Nutrient loading from the  watershed results in an upsurge period

a. Increased primary productivity

b. Increased primary consumers (zooplankton)

3. As a result, there is:

a. Increased planktivorous fish

b. Decreased zooplankton

c. Decreased DO due to greater biomass (greater swings between day and night  DO)

d. Culminated in a stable period

4. Lake Decline

a. High biomass and low DO (results in decreased decomposition and benthos  filling up with organic matter)

5. River valley continues to fill with inorganic and organic sediments and the lake  transitions into a bog

6. Eventually the lake will fill completely with sediments.

5. Be able to calculate and determine stream impairment based on Coliforms and E. coli. 


GM (cfu/100 ml)

STV (cfu/100 ml)




E. Coli



STV = Statistical Threshold Value (based on 36/1,000 probability of sickness)

Recommendation 36/1000 will become sick if exposed to GM concentrations

GM = Geometric mean (the nth root of a product of numbers). The geometric mean normalizes the range  of data so that extreme values do not dominate the average


 Can be calculated as (x1, x2, x3… xn)1/n 

The GM should not be above the standard for a 30-day period.

STV cannot be exceeded in more than 10% of observations over a 30-day period

Example: Calculate the GM and STV values for this stream to determine if it is impaired.  


E. Coli (cfu/100 ml)














12,060 (>410)













Statistical Threshold Value 

STV cannot be exceeded in more than 10% of observations over a 30-day period STV Maximum= 410 cfu/100 ml

1 observation exceeds the STV out of 13 observations

1/13 = 7.69%  

This is less than 10% of all observations, so the stream is NOT impaired for STV

Geometric Mean 

The GM should not be above the standard for a 30-day period

GM Maximum= 126 cfu/100 ml

(50 x 31 x 36 x 154 x 44 x 321 x 12,060 x 106 x 96 x 264 x 31 x 78 x 105)1/13 = 119.3  19.3 cfu/100 ml is less than 126 cfu/100 ml so the stream is NOT impaired for G

6. Be able to determine lake impairment based on chlorophyll and secchi measurements (In class  assignment). 


AA Secchi (m)

GM CHLA (ug/L)



















Secchi disk depth must be greater than or equal to 1.1 meters

Growing season geometric CHLA concentrations must be less than or equal to 8 µg

The secchi disk depth and geometric mean for CHLA shall not exceed the standard in more than  1 out of 5 years (or 20% if there are more than 5 years of data)

7. Define relative weight. A higher value means what? 

Relative weight indicates the body condition of the fish. Relative weight is based on the  relationship between the length and the weight of the fish (the “fatter” the fish, the higher the  relative weight). Relative weight is calculated by dividing the weight of the fish by the expected  weight of what is considered a healthy fish based on that length.  

8. Which of the following structures can be used to age a fish? 

∙ Scales

∙ Otoliths

∙ Spines

9. What is maximum sustainable yield? What are some problems with using MSY to manage a fishery? 

Maximum Sustainable Yield is the largest yield, or catch, which can be taken from a species stock  over an indefinite period. In most fisheries this is around 30% of the population size.  However, this approach ignores the size, age, and reproductive status of the fish which are taken,  which has led to the collapse of many fisheries

10. What are the three components of a fishery? 

1. People

2. Fish

3. Habitat

11. Be able to calculate TMDL from a hypothetical scenario (Homework #6) 

lnSD = 2.04 – 0.68lnChla

SD = Secchi depth (m)

Chla = Chlorophyll-a (ug/L)

Log10Chla = 1.583log10TP – 1.134

Chla = Chlorophyll-a (ug/L)

TP = Total phosphorus (ug/L = mg/m3)

TP = L / (z(ρ + σ))

L = average annual TP (ug/L)

Z = average depth of the lake (m)

ρ = flushing rate (y—1)

σ = sedimentation rate (y—1)


TMDL = Total Maximum Daily Load

WLA = Waste Load Allocation  

LA = Load Allocation

MOS = Margin of Safety

Example: Assuming that Lake Fayetteville, an Ozark Highland lake, has average depth of 5 m, flushing  rate of 0.5 year-1, and a sedimentation rate of 0.5 year-1, and a surface area of 600,000 m2, what is the  maximum annual P loading rate (kg P year-1) that can enter the lake so that the average annual secchi  depth does not fall below 1.5 m?

Convert the maximum annual P loading rate from the previous question into a Total Maximum Daily  Load. Assuming that there is no waste load (WLA) to Lake Fayetteville, that the Margin of Safety  (MOS) is 20% of the TMDL, and that the background load from the watershed is 120 g/day, how  much load allocation (LA) can be assigned to human non-point P sources?

Steps to Solving the Problem 

1. Plug SD into first equation and solve for Chla (answer is in ug/L)

2. Plug Chla into second equation and solve for TP (answer is in mg/m3)

3. Plug TP into the third equation to solve for L (answer is in mg m2y—1)

4. Convert L to KgP y—1 by multiplying by the area of the watershed and dividing by 106 5. Convert the L (KgP y—1) to gPday—1 by multiplying by 1,000 and diving by 365 6. Plug the TMDL into the fourth equation to calculate LA (answer is in gday—1)

ln(1.5) = 2.04 – 0.68Chla

0.405 = 2.04 – 0.68lnChla

-1.63 = - 0.68lnChla

2.4 = lnChla

Chla = 11.06 ug/L

Log10(11.06) = 1.583Log10TP – 1.134

1.04 = 1.583Log10TP – 1.134

2.178 = 1.583Log10TP

1.3757 = Log10TP

TP = 23.75 mg/m3 

23.75 = L/(5(0.5+0.5)

L = 118.75 mg m2y—1  

L = 118.75 mg m2y—1(600,000) / (106)

L = 71.25 KgPy—1 

L = 71.25 KgPy—1 

71.25 KgPy—1/365 = 0.195 KgPday—1  

0.195 KgPday—1 (1,000 mg/Kg) = 195 gPday—1 

MOS = 195 gPday—1(0.2) = 39


195 = LA + 39 +120

LA = 36 gday—1

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