PE Water Resources Exam Flashcards

Q: What specification does this PE Water Resources flashcard set follow?

This set follows the NCEES PE Civil: Water Resources and Environmental CBT specification effective beginning April 2024 and currently listed for exams before the April 2027 specification change.

Q: What are the highest-yield PE Water Resources flashcard topics?

The heaviest review areas are hydrology, closed-conduit hydraulics, open-channel hydraulics, drinking water, wastewater, and project sitework. The set also includes planning, soils, materials, analysis, groundwater, and water quality because the exam blueprint is broad.

Q: Does the PE Water Resources exam allow personal references?

No. NCEES provides the electronic PE Civil Reference Handbook and the design standards listed in the exam specification. Personal notes, printed references, and outside PDFs are not used during the exam.

Q: How should I use flashcards for a calculation-heavy PE exam?

Use flashcards to recall setup decisions: which equation applies, what assumptions are hidden, what units must be consistent, and what result would be physically unreasonable. Then pair them with timed problem solving.

Q: Does NCEES publish a passing percentage for PE Water Resources?

No. NCEES reports pass or fail and does not publish a fixed raw percentage. Study should target broad competency across the published specification rather than a guessed cut score.

Question 1

How should unit-price and lump-sum items be combined in a takeoff?

Accepted Answer

Multiply unit-price quantities by their measured units, then add lump-sum allowances separately. Do not apply a linear-foot price to fittings, mobilization, or appurtenances unless the estimate explicitly includes them.

Question 2

What makes an activity part of the critical path?

Accepted Answer

An activity is critical when delaying it delays the project finish. Critical-path review is about dependency logic and float, not simply the activity with the largest duration.

Question 3

How do present-worth comparisons choose between equal-service alternatives?

Accepted Answer

For alternatives with the same service period and performance target, the lower present-worth cost is economically preferred. Present worth already accounts for the time value of money.

Question 4

What increases active lateral earth pressure?

Accepted Answer

Higher soil unit weight, greater retained height, surcharge, and water pressure all increase wall demand. Drainage matters because hydrostatic pressure can dominate an otherwise routine retaining problem.

Question 5

What does percent compaction compare?

Accepted Answer

It compares field dry density with the laboratory maximum dry density from a specified Proctor test. Moisture content matters because dry density, not wet density, controls acceptance.

Question 6

Bearing capacity vs settlement

Accepted Answer

Bearing capacity asks whether the soil can support the load without shear failure. Settlement asks how much deformation occurs under service loads. A foundation can satisfy one check and fail the other.

Question 7

What controls USCS soil classification?

Accepted Answer

USCS classification uses grain-size distribution and plasticity behavior. Coarse soils are mainly split by gradation and fines content; fine soils are mainly split by liquid limit and plasticity index.

Question 8

How should pipe material be selected conceptually?

Accepted Answer

Match the material to pressure, corrosion, loading, joints, constructability, and service environment. Gravity sewers, force mains, and potable water mains may need different priorities.

Question 9

What does construction site control protect?

Accepted Answer

Site control protects benchmarks, limits of work, utility locations, layout points, and adjacent facilities. Poor control can create drainage errors, encroachments, rework, or safety hazards.

Question 10

What is the mass-balance question always asking?

Accepted Answer

It asks whether accumulation equals inputs minus outputs plus generation minus consumption. At steady state, accumulation is zero, which often simplifies the setup.

Question 11

What is hydraulic loading rate?

Accepted Answer

Hydraulic loading rate is flow divided by surface area, commonly used for basins, filters, clarifiers, and infiltration systems. Unit consistency is the main trap.

Question 12

What is solids loading?

Accepted Answer

Solids loading is mass of solids applied per time, often normalized by area or volume. It combines concentration and flow, so both units must be converted before comparing to criteria.

Question 13

How is detention time interpreted?

Accepted Answer

Nominal detention time is volume divided by flow. It is a planning estimate; short-circuiting, dead zones, and mixing can make actual contact time lower than the simple ratio.

Question 14

What is the purpose of flow measurement structures?

Accepted Answer

Weirs, flumes, meters, and similar devices convert water level, velocity, or pressure signals into flow. The correct method depends on channel conditions, calibration, submergence, and expected flow range.

Question 15

What does continuity require in closed conduits?

Accepted Answer

For incompressible steady flow, Q = V A at each section. If pipe area decreases, velocity increases for the same flow; the water does not disappear.

Question 16

HGL vs EGL

Accepted Answer

The hydraulic grade line shows pressure head plus elevation head. The energy grade line adds velocity head. The EGL is above the HGL by V^2/(2g), except where velocity is negligible.

Question 17

Darcy-Weisbach vs Hazen-Williams

Accepted Answer

Darcy-Weisbach is broadly applicable when friction factor and units are handled correctly. Hazen-Williams is an empirical water-pipe equation and should not be used outside its assumptions.

Question 18

Major loss vs minor loss

Accepted Answer

Major loss is friction along pipe length. Minor losses come from fittings, entrances, exits, bends, valves, and expansions. In short systems, minor losses can be a major part of total headloss.

Question 19

What does the pump operating point represent?

Accepted Answer

It is where the pump curve intersects the system curve. Changing pipe size, static lift, valve position, or roughness changes the system curve and can move the actual flow away from the desired value.

Question 20

What causes pump cavitation risk?

Accepted Answer

Cavitation risk rises when pressure near the impeller falls below vapor pressure. In PE terms, check available NPSH against required NPSH and watch suction lift, temperature, losses, and low wet-well levels.

Question 21

What does Manning's equation solve in open channels?

Accepted Answer

Manning relates flow, roughness, hydraulic radius, area, and slope for uniform open-channel flow. The trap is using it where flow is rapidly varied, pressurized, or controlled by a structure.

Question 22

Subcritical vs supercritical flow

Accepted Answer

Subcritical flow is deep, slow, and downstream-controlled. Supercritical flow is shallow, fast, and upstream-controlled. Froude number below 1 is subcritical; above 1 is supercritical.

Question 23

What is critical depth?

Accepted Answer

Critical depth is the depth at minimum specific energy for a given flow. It separates subcritical and supercritical regimes and often appears near controls, transitions, and culvert behavior.

Question 24

What does a hydraulic jump accomplish?

Accepted Answer

A hydraulic jump converts supercritical flow to subcritical flow and dissipates energy through turbulence. It is useful downstream of spillways, culverts, and drops when erosion protection is needed.

Question 25

Inlet control vs outlet control for culverts

Accepted Answer

Inlet control means capacity is governed near the entrance. Outlet control means downstream water level, barrel roughness, length, and tailwater govern. The controlling condition determines the headwater calculation.

Question 26

What does the Rational Method estimate?

Accepted Answer

Q = C i A estimates peak runoff for small drainage areas when rainfall intensity matches the time of concentration. It estimates peak flow, not a full runoff hydrograph.

Question 27

Why does time of concentration matter?

Accepted Answer

Time of concentration is the travel time from the hydraulically most distant point to the outlet. A shorter Tc usually means higher design rainfall intensity and higher peak flow.

Question 28

What does an IDF curve connect?

Accepted Answer

An intensity-duration-frequency curve links rainfall intensity, storm duration, and return period. For the same return period, shorter durations usually have higher intensities.

Question 29

What does a higher NRCS curve number imply?

Accepted Answer

A higher curve number means less infiltration and more direct runoff for the same rainfall. Impervious cover, poor soil infiltration, and wet antecedent conditions push runoff higher.

Question 30

Peak flow vs runoff volume on a hydrograph

Accepted Answer

Peak flow is the maximum ordinate of the hydrograph. Runoff volume is the area under the hydrograph. Detention mainly reduces and delays the peak; infiltration or reuse can reduce volume.

Question 31

What is a stream rating curve?

Accepted Answer

A rating curve relates stage to discharge at a gauging location. It is site-specific and can shift after channel scour, sediment deposition, vegetation growth, or backwater effects.

Question 32

Detention vs retention BMPs

Accepted Answer

Detention temporarily stores runoff and releases it over time. Retention holds water for infiltration, evaporation, reuse, or permanent pool storage. Confusing them changes both flow and volume assumptions.

Question 33

What does Darcy's law describe in groundwater?

Accepted Answer

Darcy's law relates groundwater flow to hydraulic conductivity, hydraulic gradient, and flow area. It is a flow law, so gradients and units must match the direction and scale of the problem.

Question 34

Confined vs unconfined aquifer

Accepted Answer

A confined aquifer is under pressure beneath a confining layer. An unconfined aquifer has a water table open to atmospheric pressure. The storage behavior and drawdown response differ.

Question 35

What happens when pumping wells interfere?

Accepted Answer

Their cones of depression overlap, increasing drawdown compared with a single isolated well. Interference can reduce available yield or increase pumping lift.

Question 36

How are BOD and dissolved oxygen related?

Accepted Answer

Biochemical oxygen demand consumes dissolved oxygen as organics degrade. High BOD loading can depress stream DO and harm aquatic life, especially when reaeration is limited.

Question 37

What is a TMDL?

Accepted Answer

A total maximum daily load is the pollutant amount a water body can receive and still meet water-quality standards. It is allocated among point sources, nonpoint sources, and a margin of safety.

Question 38

Why do nutrients drive eutrophication?

Accepted Answer

Excess nitrogen or phosphorus can stimulate algal growth. When algae decay, oxygen demand rises and dissolved oxygen can fall, creating ecological stress or fish kills.

Question 39

What slows contaminant movement in groundwater?

Accepted Answer

Sorption, dispersion, biodegradation, decay, and lower hydraulic gradients can slow or spread a plume. Advection moves contaminants with groundwater flow; retardation makes some chemicals lag behind the water.

Question 40

Average day vs maximum day vs peak hour demand

Accepted Answer

Average day is long-term typical use. Maximum day is the largest daily demand used for supply and storage checks. Peak hour is the short-duration high demand that stresses distribution hydraulics.

Question 41

What is the conventional surface-water treatment sequence?

Accepted Answer

Coagulation destabilizes particles, flocculation grows settleable floc, sedimentation removes much of it, filtration polishes the water, and disinfection inactivates pathogens.

Question 42

What do disinfectant residual and contact time protect?

Accepted Answer

Contact time supports pathogen inactivation, while residual helps protect water in the distribution system. Too little risks microbial safety; too much can worsen taste, odor, or byproduct concerns.

Question 43

How is hardness commonly treated?

Accepted Answer

Hardness from calcium and magnesium can be reduced by lime softening, ion exchange, membranes, or blending. The right method depends on water chemistry, residuals, cost, and finished-water goals.

Question 44

Infiltration vs inflow in wastewater collection

Accepted Answer

Infiltration is groundwater entering through defects such as cracked pipes and leaky joints. Inflow is stormwater entering through direct connections such as roof drains, cross-connections, or open manholes.

Question 45

Primary vs secondary wastewater treatment

Accepted Answer

Primary treatment removes settleable and floatable solids by physical separation. Secondary treatment uses biological processes to remove dissolved and colloidal biodegradable organics.

Question 46

What do F/M ratio and SRT indicate in activated sludge?

Accepted Answer

F/M compares food load to microorganism mass. SRT estimates how long solids stay in the biological system. Together they affect treatment stability, sludge age, oxygen demand, and nitrification potential.

Question 47

Nitrification vs denitrification

Accepted Answer

Nitrification converts ammonia to nitrate under aerobic conditions. Denitrification converts nitrate to nitrogen gas under anoxic conditions with a carbon source. The oxygen condition is the key distinction.

Question 48

Why are wastewater solids thickened or dewatered?

Accepted Answer

Thickening and dewatering reduce water content before hauling, disposal, or further treatment. Lower volume reduces handling cost, but stabilization may still be needed for odor, pathogens, and vector attraction.

Question 49

What is the first sitework priority for erosion control?

Accepted Answer

Stabilize and control runoff before exposed soil leaves the site. Perimeter controls, inlet protection, construction entrances, sequencing, and prompt stabilization prevent sediment from becoming a downstream water-quality problem.

Question 50

What does good grading accomplish?

Accepted Answer

Good grading balances cut and fill where practical, directs runoff safely, protects adjacent facilities, avoids unintended ponding, and supports constructability. A visually smooth surface is not enough if drainage fails.

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