Hydrology & Watershed Management Flashcards
7 cards from real CSM practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Hydrology & Watershed Management flashcards as text
In continuous hydrologic simulation modeling, which process must be modeled to properly account for soil moisture between storm events?
Answer: Evapotranspiration and soil moisture depletion
Between storms, ET depletes soil moisture which must be tracked continuously so that the model correctly simulates the antecedent conditions and available storage for each subsequent storm.
Which watershed characteristic most strongly controls the lag time between the centroid of effective rainfall and the peak of the runoff hydrograph?
Answer: Watershed slope and channel hydraulic roughness
Steeper slopes and smoother channels (lower roughness) accelerate flow velocities, shortening the lag time between rainfall and peak discharge.
Which of the following describes the hydrologic condition 'poor' as used in the SCS curve number tables for pasture or range land?
Answer: Heavily grazed, less than 50% ground cover
Poor hydrologic condition for pasture/range indicates heavily grazed land with sparse ground cover (less than 50%), resulting in compacted soil and high runoff potential.
The Muskingum method is a hydrologic technique used for:
Answer: Routing flood hydrographs through river channels
The Muskingum method uses storage-discharge relationships parameterized by K (travel time) and X (weighting factor) to translate and attenuate flood waves through channel reaches.
A watershed manager notices that baseflow in a stream has declined significantly over 20 years despite similar rainfall patterns. The most likely cause is:
Answer: Reduction in groundwater recharge due to expanded impervious cover
Impervious surfaces prevent infiltration and groundwater recharge; over time, declining aquifer levels reduce the groundwater contribution that sustains baseflow between storms.
Which design storm concept is commonly used for sizing water quality treatment BMPs in stormwater management?
Answer: A small, frequently occurring storm such as the 90th percentile storm event
Water quality BMPs are typically designed to treat the most frequently occurring runoff events, often the 90th percentile storm, which collectively carry the majority of the annual pollutant load.
In NRCS TR-55 methodology, which of the following contributes to the 'sheet flow' portion of time of concentration calculation?
Answer: Overland flow on unpaved or paved surfaces for distances up to 300 feet
Sheet flow is the initial overland flow phase, occurring over plane surfaces (grass, pavement, bare soil) for distances up to 300 feet before concentrating into shallow concentrated flow or channels.