Water Quality & Management Flashcards

Which numeric water quality criterion type sets a concentration that should not be exceeded at any time to protect aquatic life?

Answer: Acute criterion (criterion maximum concentration)

The criterion maximum concentration (CMC) is the short-term acute standard not to be exceeded at any time, protecting against immediate toxicity.

Nonpoint source (NPS) pollution is best controlled through which management approach?

Answer: Best Management Practices (BMPs) applied at the source

BMPs—such as buffer strips, sediment ponds, and cover crops—reduce NPS pollution at or near where it originates before it reaches water bodies.

The oxygen sag curve downstream of a wastewater discharge describes the relationship between:

Answer: Dissolved oxygen recovery and organic oxygen demand over distance

The Streeter-Phelps oxygen sag curve models the balance between BOD deoxygenation and natural reaeration as stream water travels downstream.

A riparian buffer strip is most effective at reducing which water quality stressor from adjacent agricultural fields?

Answer: Sediment and nutrient runoff

Vegetated riparian buffers trap eroded soil particles and filter dissolved nutrients in shallow overland flow before it enters streams.

Which analytical method is the standard US EPA approach for measuring total phosphorus in water samples?

Answer: Persulfate digestion followed by colorimetric analysis (EPA Method 365.3)

EPA Method 365.3 uses persulfate oxidation to convert all phosphorus forms to orthophosphate, then quantifies it colorimetrically.

In watershed-scale water quality management, a load duration curve (LDC) is used to:

Answer: Compare measured pollutant loads to allowable loads across a range of stream flows

An LDC plots allowable and observed pollutant loads versus flow exceedance probability, showing when and how often standards are exceeded.

Elevated concentrations of which metal in mining-affected streams often drive pH well below 4, creating a condition known as acid mine drainage?

Answer: Iron (Fe) and sulfate from pyrite oxidation

Pyrite oxidation produces ferrous iron and sulfuric acid, dramatically lowering pH and releasing toxic metals in acid mine drainage.