Saltwater Intrusion
What allows saltwater to creep upstream into the Mississippi River?
A) Heavy rainfall upstream
B) Low river discharge weakening the freshwater barrier
C) Increased boat traffic
D) Warming ocean temperatures only
What is B) Low river discharge weakening the freshwater barrier ✅
How is flash drought different from conventional drought?
A) It only occurs in coastal areas
B) It develops rapidly over days to weeks instead of gradually over months
C) It is caused only by heat, not lack of rain
D) It lasts longer than regular drought
What is B) It develops rapidly over days to weeks instead of gradually over months ✅
What does EDDI stand for?
A) Extreme Drought Detection Indicator
B) Evaporative Demand Drought Index
C) Environmental Dryness and Deficit Index
D) Estimated Daily Drought Intensity
What is
B) Evaporative Demand Drought Index ✅
Which agency built emergency sills to block saltwater from reaching New Orleans?
A) EPA
B) FEMA
C) US Army Corps of Engineers
D) USGS
What is C) US Army Corps of Engineers ✅
How quickly did Baton Rouge's EDDI percentile jump during the flash drought onset in June 2023?
A) From 10th to 50th percentile over 2 months
B) From 39th to 93rd percentile in just 10 days
C) From 50th to 75th percentile in 3 weeks
D) From 20th to 60th percentile over a month
What is B) From 39th to 93rd percentile in just 10 days ✅
What does EDDI specifically measure?
A) Total rainfall over a given period
B) Soil moisture at the surface level
C) The atmosphere's "thirst" for moisture / evaporative demand
D) River discharge at a downstream gauge
What is
C) The atmosphere's "thirst" for moisture / evaporative demand ✅
Before 2022 and 2023, how many times had emergency sills ever been needed on the Mississippi River?
A) Once
B) Twice
C) Three times
D) Five times
What is C) Three times ✅
The years were:
1988
1999
2012
When did engineers first predict that the saltwater wedge could overtop the emergency sill and threaten New Orleans’ drinking water supply?
A) Early September 2023
B) Late-September 2023
C) Early October 2023
D) Late October 2023
What is B) Late-September 2023 ✅
What conditions trigger Acute Marsh Dieback in Louisiana's coastal wetlands?
What is B) Prolonged marsh exposure to air causing hypersalinity and soil acidification ✅
According to the case study, why may saltwater intrusion events in the lower Mississippi River become more likely in the future?
A) Increased precipitation in the Mississippi River Basin will push saltwater upstream.
B) Rising sea levels combined with periods of low Mississippi River discharge will allow the saltwater wedge to move farther inland toward drinking water intakes.
C) Stronger hurricanes will permanently change the salinity of the Mississippi River.
D) Warmer ocean temperatures will directly increase salt concentrations in river water.
What is B) Rising sea levels combined with periods of low Mississippi River discharge will allow the saltwater wedge to move farther inland toward drinking water intakes. ✅
What two conditions must coincide to drive flash drought?
A) High winds and low humidity
B) Precipitation deficits AND high evaporative demand
C) Record heat AND flooding
D) Low soil moisture AND high rainfall
What is B) Precipitation deficits AND high evaporative demand ✅
What is a saltwater wedge?
A) A storm surge barrier built to protect cities
B) A dense layer of seawater that creeps upstream along the bottom of a river when freshwater flow drops too low
C) A type of coastal erosion caused by hurricanes
D) A chemical process that increases river salinity during drought
What is B) A dense layer of seawater that creeps upstream along the bottom of a river when freshwater flow drops too low ✅
Why is saltwater intrusion expected to get WORSE in future years even without more severe droughts?
A) The Mississippi River is getting narrower over time
B) Louisiana's relative sea level rise means saltwater is already closer to water intake pipes
C) New Orleans is removing its flood barriers
D) Gulf of Mexico salinity is decreasing
What is B) Louisiana's relative sea level rise means saltwater is already closer to water intake pipes ✅
Flash drought conditions in 2023 were not limited to Louisiana. Which of the following regions ALSO experienced flash drought as part of the broader Mississippi River Basin drying?
A) Florida and Georgia
B) South Dakota, Nebraska, Kansas, and Iowa
C) Tennessee and Alabama
D) Colorado and Utah
What is B) South Dakota, Nebraska, Kansas, and Iowa ✅
When marsh soils are exposed to air for long periods during drought, what chemical process occurs?
What is B) Sulfides oxidize to form sulfuric acid, lowering soil pH ✅