CH Water Quality & Management 2 — Questions and Answers
Question 1: Which parameter is most commonly used to assess the oxygen-demanding organic load in a water body?
- Biochemical Oxygen Demand (BOD) (Correct answer)
- Total Dissolved Solids (TDS)
- Turbidity
- Alkalinity
Correct answer: Biochemical Oxygen Demand (BOD)
BOD measures the amount of oxygen consumed by microorganisms decomposing organic matter, directly indicating organic pollution levels.
Question 2: The Clean Water Act Section 303(d) requires states to identify waters that are:
- Impaired and do not meet water quality standards (Correct answer)
- Protected as Outstanding National Resource Waters
- Free of any pollutant discharge
- Designated for recreational use only
Correct answer: Impaired and do not meet water quality standards
Section 303(d) lists impaired waters that fail to meet water quality standards and requires development of Total Maximum Daily Loads (TMDLs).
Question 3: Eutrophication in lakes is primarily caused by excess loading of which nutrients?
- Nitrogen and Phosphorus (Correct answer)
- Iron and Manganese
- Calcium and Magnesium
- Sodium and Potassium
Correct answer: Nitrogen and Phosphorus
Excess nitrogen and phosphorus stimulate algal blooms that deplete oxygen and degrade aquatic habitat, causing eutrophication.
Question 4: What does a Secchi disk measurement indicate in water quality monitoring?
- Water clarity/transparency (Correct answer)
- Dissolved oxygen concentration
- pH level
- Specific conductance
Correct answer: Water clarity/transparency
A Secchi disk is lowered into water until it disappears from view; the depth at which it vanishes indicates water transparency.
Question 5: Which water quality standard category protects human health through drinking water consumption and fish ingestion?
- Human health criteria (Correct answer)
- Aquatic life criteria
- Wildlife criteria
- Agricultural use criteria
Correct answer: Human health criteria
Human health criteria establish maximum contaminant concentrations protective of people who drink water and consume fish from a water body.
Question 6: A hydrographer notes a sudden drop in dissolved oxygen below 2 mg/L in a river reach. This condition is described as:
- Hypoxic (Correct answer)
- Eutrophic
- Anoxic
- Oligotrophic
Correct answer: Hypoxic
Hypoxia refers to low dissolved oxygen conditions (typically below 2–3 mg/L) that stress or kill aquatic organisms.
Question 7: Conductivity measurements in streams primarily reflect the concentration of:
- Dissolved ions and salts (Correct answer)
- Suspended sediment
- Dissolved organic carbon
- Biological oxygen demand
Correct answer: Dissolved ions and salts
Electrical conductivity increases with dissolved ion concentration; high conductivity often signals elevated salinity or mineral content.
CH Water Quality & Management 2
Which parameter is most commonly used to assess the oxygen-demanding organic load in a water body?