SCE Practice of Engineering (PE) — Water Resources and Environmental Engineering (Saudi Arabia)

A rectangular concrete stormwater channel in Riyadh has a bottom width of 3.0 m, a uniform flow depth of 1.5 m, a bed slope of 0.0016, and a Manning roughness coefficient n = 0.015. What is the volumetric discharge rate of the channel under uniform flow conditions?

• A15.72 m³/s
• B12.00 m³/s
• C9.91 m³/s
• D7.43 m³/s

A 1,000 m long ductile iron transmission pipeline with an internal diameter of 400 mm conveys water at a flow rate of 0.20 m³/s. Assuming a Darcy-Weisbach friction factor f = 0.020 and acceleration due to gravity g = 9.81 m/s², what is the frictional head loss along the pipe?

• A12.91 m
• B6.45 m
• C25.82 m
• D1.61 m

A booster pump at a municipal water distribution station delivers 180 m³/h of water against a total dynamic head of 45 m. If the pump efficiency is 75%, water density is 1,000 kg/m³, and g = 9.81 m/s², what is the required pump brake (shaft) power?

• A22.1 kW
• B16.6 kW
• C39.2 kW
• D29.4 kW

In a pressurized water pipeline of uniform cross-section flowing under steady conditions, how is the Energy Grade Line (EGL) related to the Hydraulic Grade Line (HGL)?

• AThe EGL lies above the HGL by the velocity head V²/(2g), parallel to it
• BThe HGL is vertically above the EGL by a distance equal to the pressure head P/γ
• CThe EGL and HGL are coincident because the pipe has a constant diameter
• DThe EGL lies below the HGL by a distance equal to the elevation head z

A wide rectangular open channel conveys a flow with a unit discharge (discharge per unit width) q = 2.80 m²/(s·m). Taking g = 9.81 m/s², what is the critical depth of flow in this channel?

• A0.80 m
• B1.39 m
• C0.93 m
• D0.89 m

In open channel hydraulics, what flow regime is characterized by a Froude number less than 1.0 (Fr < 1)?

• ASupercritical flow, where gravity waves cannot propagate upstream against the current
• BCritical flow, where specific energy is at its maximum for a given discharge and the dept…
• CHydraulic jump flow, where rapid shallow flow abruptly becomes tranquil flow
• DSubcritical flow, where flow velocity is less than wave celerity and disturbances can tra…

A hydraulic jump occurs in a horizontal rectangular drainage channel. Immediately upstream of the jump, the initial flow depth y₁ = 0.50 m and the flow velocity V₁ = 6.0 m/s. Taking g = 9.81 m/s², what is the sequent (subsequent) flow depth y₂ immediately downstream of the jump?

• A0.94 m
• B1.68 m
• C2.18 m
• D3.36 m

Which set of operational conditions will significantly INCREASE the risk of cavitation in a centrifugal water supply pump?

• AOperating at elevated water temperature with excessive suction lift and a throttled sucti…
• BIncreasing the suction reservoir liquid elevation and operating with a short, oversized s…
• CDecreasing water temperature and installing an inducer on the pump suction impeller
• DMaintaining NPSHa at least 1.5 meters greater than NPSHr across all operating points

What is the primary theoretical limitation of using the Hazen-Williams formula for pipe friction head loss compared to the Darcy-Weisbach equation?

• AIt can only be applied to non-circular conduits and open ditches
• BIt assumes laminar flow throughout the entire Reynolds number range
• CIt requires iterative calculation of the friction factor from the Colebrook equation for…
• DIt is empirical, valid for water in turbulent flow at ordinary temperatures, and ignores…

Water flows at an initial velocity of 2.0 m/s through a long transmission pipeline with an acoustic pressure wave celerity a = 1,000 m/s and water density ρ = 1,000 kg/m³. If a downstream control valve closes instantaneously, what is the magnitude of the Joukowsky water hammer pressure surge ΔP?

• A0.2 MPa (approx. 20.4 m of head)
• B5.0 MPa (approx. 510 m of head)
• C2.0 MPa (approx. 204 m of head)
• D0.5 MPa (approx. 51 m of head)

A commercial development site in Dammam has a drainage catchment area of 12.0 hectares, a composite runoff coefficient C = 0.65, and a 25-year design rainfall intensity of 50 mm/h. Using the Rational Method, what is the estimated peak stormwater runoff rate Q?

• A3.90 m³/s
• B1.08 m³/s
• C0.11 m³/s
• D10.84 m³/s

An arid watershed in western Saudi Arabia has an annual precipitation of 120 mm, surface runoff measured at the catchment outlet of 15 mm, and estimated annual evapotranspiration of 95 mm. Based on the fundamental hydrologic water budget equation (P = R + ET + ΔS), what is the annual net groundwater recharge (storage change ΔS)?

• A+10 mm
• B-10 mm
• C+40 mm
• D0 mm

A fully penetrating production well pumps water at a steady rate from a confined sandstone aquifer. Two observation piezometers located at radial distances r₁ = 20 m and r₂ = 100 m from the pumping well exhibit steady drawdowns of s₁ = 3.5 m and s₂ = 1.5 m, respectively. If the aquifer transmissivity T = 300 m²/day, what is the pumping discharge Q?

• A1,171 m³/day
• B4,099 m³/day
• C5,393 m³/day
• D2,342 m³/day

A regional unconfined aquifer has an isotropic hydraulic conductivity K = 15.0 m/day and an effective porosity n_e = 0.20. Piezometric monitoring indicates a hydraulic gradient i = 0.0040. What are the Darcy velocity (specific discharge v) and the average linear pore seepage velocity (v_s), respectively?

• Av = 0.300 m/day; v_s = 0.060 m/day
• Bv = 0.060 m/day; v_s = 0.012 m/day
• Cv = 0.060 m/day; v_s = 0.300 m/day
• Dv = 0.600 m/day; v_s = 3.000 m/day

A coastal monitoring well drilled near the Arabian Gulf reveals that the water table elevation in an unconfined coastal aquifer stands at 1.20 m above mean sea level. Assuming freshwater density ρ_f = 1,000 kg/m³ and seawater density ρ_s = 1,025 kg/m³, what is the estimated depth to the freshwater–saline water interface below sea level according to the Ghyben-Herzberg relationship?

• A49.2 m
• B48.0 m
• C24.0 m
• D0.03 m

In groundwater hydrogeology, how does the specific yield (S_y) of an unconfined aquifer relate to its total porosity (n) and specific retention (S_r)?

• AS_y = n × S_r, where specific yield represents the microscopic pore connectivity
• BS_r = S_y − n, where specific retention is the water released under high-pressure artesia…
• CS_y is identical to the storativity S of a confined aquifer, so it is independent of the…
• Dn = S_y + S_r, where specific yield is the volume of water drained by gravity per unit vo…

A 1-hour unit hydrograph (UH) represents 1.0 cm of direct runoff generated uniformly across a catchment. The ordinates of the 1-hour UH at consecutive 1-hour intervals starting at t = 0 are [0, 15, 35, 25, 10, 0] m³/s. A storm produces 2.0 cm of effective rainfall in the first hour and 1.0 cm in the second hour. What is the peak direct runoff discharge generated by this storm?

• A85 m³/s, at both t = 2 h and t = 3 h
• B70 m³/s, reached only at t = 2 h
• C95 m³/s, reached only at t = 3 h
• D105 m³/s, reached only at t = 2 h

An environmental engineer is designing a stormwater flood culvert in an industrial city in Saudi Arabia. If the culvert is designed for a 50-year return period flood (T = 50 years) and the project has an intended design life of 30 years, what is the probability (risk) that the design flood capacity will be equaled or exceeded at least once during the 30-year lifetime?

• A60.0%
• B2.0%
• C45.5%
• D54.5%

In the Muskingum hydrologic channel routing method, the storage S in a reach is expressed as S = K * [x * I + (1 - x) * Q]. What physical meaning is associated with the weighting factor x?

• Ax represents the wave travel time through the reach, expressed in hours
• Bx weights inflow vs outflow in storage, from 0 (reservoir) to 0.5 (pure translation)
• Cx is the Manning roughness coefficient adjusted for channel bedforms
• Dx is a storage attenuation ratio that always exceeds 1.0 during flash floods in steep wad…

In arid and hyper-arid regions such as Saudi Arabia, Managed Aquifer Recharge (MAR) projects are increasingly implemented in wadi systems. What is the primary operational objective of constructing permeable wadi recharge dams?

• ATo store flood water in a deep surface reservoir for direct year-round irrigation releases
• BTo trap sediment so that the wadi bed downstream becomes impermeable and floods pass fast…
• CTo divert flood runoff away from the alluvium into lined channels that discharge to the s…
• DTo detain flash-flood runoff so it infiltrates the wadi alluvium and recharges shallow aq…

A sharp-crested rectangular suppressed weir (no end contractions) with a crest length b = 4.0 m is installed in an open channel. The measured upstream head above the weir crest is H = 0.64 m. Using the standard Francis weir formula Q = 1.84 * b * H^(3/2), what is the discharge over the weir?

• A3.77 m³/s
• B4.71 m³/s
• C2.41 m³/s
• D6.82 m³/s

Why is a 90° triangular (V-notch) weir often preferred over a rectangular weir for measuring small discharges, such as low flows at an environmental monitoring station?

• AThe V-notch weir produces zero head loss across the measurement structure
• BThe V-notch weir eliminates the need for any approach-velocity correction regardless of c…
• CDischarge varies with H^(5/2), so small flows still produce a large, easily measured head
• DThe V-notch weir is self-cleaning and immune to debris entrapment

A highway drainage culvert operating under INLET CONTROL is governed primarily by which group of hydraulic and geometric factors?

• ACulvert barrel length, barrel roughness (Manning n), barrel slope, and tailwater depth
• BHeadwater depth, inlet edge configuration, barrel shape, and cross-sectional area
• CTailwater elevation, sediment build-up in the downstream channel, and outlet velocity
• DDownstream channel backwater curve and outlet scour apron dimensions

During the hydraulic design of an Ogee (overflow) dam spillway crest, what critical physical phenomenon occurs if the actual operating head H_a significantly exceeds the original design head H_d (i.e., H_a > H_d)?

• AThe discharge coefficient C drops to zero, choking the spillway flow
• BThe flowing nappe separates and immediately transitions to a submerged hydraulic jump on…
• CPositive hydrostatic pressures increase linearly, increasing friction loss across the spi…
• DNegative (sub-atmospheric) pressures develop along the crest surface, creating a risk of…

In the design of USBR Type III hydraulic jump stilling basins located downstream of dam spillways, what is the specific engineering purpose of installing baffle piers and chute blocks?

• ATo break up the incoming jet, stabilize the jump and shorten the required basin length
• BTo force the hydraulic jump to form downstream of the basin end sill
• CTo raise the incoming Froude number so that a stronger jump forms
• DTo let the basin work without tailwater, so the tailwater rating curve need not be checked

A flow net is drawn to analyze steady seepage beneath an earthfill water storage dam resting on an isotropic pervious foundation. The flow net consists of 4 flow channels (N_f = 4) and 12 equipotential drops (N_d = 12). The total hydraulic head difference between upstream and downstream water levels is 18.0 m, the foundation soil hydraulic conductivity is k = 3.0 × 10⁻⁶ m/s, and the dam crest length is 200 m. What is the total seepage discharge rate beneath the dam?

• A10.80 L/s
• B32.40 L/s
• C3.60 L/s
• D0.018 L/s

In the hydraulic design of an embankment dam foundation, which expression gives Terzaghi's critical hydraulic gradient (i_c) for piping or heave, and how is it used in design?

• Ai_c = (1 + e)/(G_s − 1) ≈ 2.5; the exit gradient may approach this value with a factor of…
• Bi_c = G_s × e ≈ 0.5; the exit gradient must simply stay below 0.5
• Ci_c = (G_s + 1)/(1 − e) ≈ 3.0; a factor of safety of 2.0 is applied to the exit gradient
• Di_c = (G_s − 1)/(1 + e) ≈ 1.0 for typical sands; designs keep the exit gradient well belo…

What is the primary governing criterion when sizing riprap stone revetment on the upstream slope of an earthfill reservoir embankment in Saudi Arabia?

• AD₅₀ is sized only for the velocity of water entering the reservoir from upstream wadis
• BD₅₀ is sized to resist wave action generated by the design wind over the reservoir fetch
• CD₅₀ is set equal to the embankment fill D₅₀ so that no filter layer is needed
• DD₅₀ is chosen mainly for durability against sulfate attack, with size a secondary check

An environmental engineer designs a multi-stage outlet structure for a stormwater detention basin. What is the hydraulic purpose of incorporating a bottom low-flow orifice combined with an elevated top weir?

• AThe orifice slowly releases small, frequent storms for water quality; the higher weir con…
• BThe bottom orifice handles the largest design storms, while the upper weir controls only…
• CThe bottom orifice keeps a permanent wet pool for evaporation, while the weir discharges…
• DThe two openings are sized for the same storm so that one duplicates the other if it beco…

When designing an open-water coastal intake structure for an industrial desalination or cooling facility, why is the maximum through-screen approach velocity typically limited to 0.15 m/s (0.5 ft/s)?

• ATo prevent cavitation erosion of the intake pipe and its concrete lining
• BTo keep laminar flow conditions throughout the seawater conveyance canal
• CTo let motile fish sense the current and swim away, reducing impingement
• DTo maximize sediment scouring at the intake mouth so that it stays clear

Under Saudi Arabia's National Water Strategy 2030, what is the main policy direction for deep non-renewable (fossil) aquifers such as the Saq, Wajid and Wasia-Biyadh formations?

• AExpand abstraction so groundwater can replace coastal desalination for inland cities
• BUse the aquifers mainly for agriculture, since desalinated water is reserved for industry
• CTreat the aquifers as renewable, because occasional flash floods are assumed to recharge…
• DCut non-renewable abstraction, especially for thirsty crops, and keep the aquifers as a s…

According to the standard International Water Association (IWA) water balance methodology, Non-Revenue Water (NRW) in a municipal distribution network is defined as the sum of which two primary loss components plus unbilled authorized consumption?

• AEvaporation losses from service reservoirs and condensation in pipes
• BReal (physical) losses and apparent (commercial) losses
• CTreated sewage effluent and agricultural drainage return flows
• DDesalination brine reject and filter backwash water

What is the primary operational methodology used when establishing District Metered Areas (DMAs) to locate and reduce background leakage in municipal water distribution networks?

• AClosing boundary valves to form a metered zone and tracking its minimum night flow
• BEmptying sections of the network periodically for visual inspection of the pipe interiors
• CRaising zone pressure at night so that leaks become audible to acoustic loggers
• DComparing each customer's monthly bill with the previous year's bill to find leaks

In a municipal water distribution network, leakage flow q is related to operating pressure P by q = C × P^(N1), where N1 is the leakage exponent. An engineer installs a Pressure Reducing Valve (PRV) that lowers the average zone pressure from 50.0 m to 35.0 m of head. If the network has a leakage exponent N1 = 1.0 (a common assumption for large systems with mixed pipe materials), what is the percentage reduction in real leakage losses?

• A15.0%
• B16.3%
• C30.0%
• D42.9%

The Dublin Principles, adopted in 1992 and central to Integrated Water Resources Management (IWRM), establish four core tenets. Which of the following statements correctly summarizes Dublin Principle 4 regarding water valuation?

• AFresh water is a finite and vulnerable resource, essential to sustain life, development a…
• BWater development and management should be based on a participatory approach involving us…
• CWomen play a central part in the provision, management and safeguarding of water
• DWater has an economic value in all its competing uses and should be recognized as an econ…

When evaluating competing water supply schemes (e.g., expanding seawater reverse osmosis vs. developing managed aquifer recharge vs. piping deep groundwater) using Multi-Criteria Decision Analysis (MCDA), what is the function of the Analytic Hierarchy Process (AHP)?

• ATo weight criteria and rank alternatives by pairwise comparisons on a 1–9 scale, checked…
• BTo discount each alternative's future costs and benefits to a single present value
• CTo estimate the probability distribution of outcomes by repeated random sampling of each…
• DTo trace the material and energy flows of each alternative from cradle to grave

How do modern Supervisory Control and Data Acquisition (SCADA) systems integrated with Advanced Metering Infrastructure (AMI) assist water authorities in managing non-revenue water in real time?

• ABy pinpointing every leak to within a metre directly from the control room, without needi…
• BBy logging flow, pressure and meter data continuously so that bursts and rising night flo…
• CBy removing apparent losses entirely, because smart meters can never under-register
• DBy raising network pressure automatically at night so that service reservoirs stay full

A Seawater Reverse Osmosis (SWRO) desalination facility on the Red Sea coast processes a raw seawater feed flow rate Q_f = 10,000 m³/day at an overall plant recovery rate Y = 42.0%. What is the volumetric discharge rate of the concentrate (brine reject) stream Q_b?

• A4,200 m³/day
• B13,810 m³/day
• C5,800 m³/day
• D17,241 m³/day

A seawater reverse osmosis membrane element operates with an incoming feed water Total Dissolved Solids (TDS) concentration C_f = 42,000 mg/L (typical Arabian Gulf seawater). If the membrane element has an observed salt rejection rate R = 99.40%, what is the TDS concentration of the permeate product water (C_p)?

• A252 mg/L
• B2,520 mg/L
• C25.2 mg/L
• D420 mg/L

The theoretical osmotic pressure (Π) of a dilute electrolyte solution can be estimated with the van 't Hoff equation Π = i C R T. For a seawater sample with an NaCl-equivalent molar concentration C = 0.60 mol/L, a van 't Hoff factor i = 2.0 (complete NaCl dissociation), R = 0.08206 L·atm/(mol·K) and T = 298 K (25°C), what is the estimated osmotic pressure Π?

• A14.7 atm (approx. 14.9 bar or 1.49 MPa)
• B58.7 atm (approx. 59.5 bar or 5.95 MPa)
• C2.5 atm (approx. 2.5 bar or 0.25 MPa)
• D29.3 atm (approx. 29.7 bar or 2.97 MPa)

What is the primary thermodynamic and environmental distinction between Seawater Reverse Osmosis (SWRO) and thermal desalination processes such as Multi-Stage Flash (MSF) and Multi-Effect Distillation (MED)?

• ASWRO separates water by evaporation and condensation, while MSF and MED force seawater th…
• BSWRO is a pressure-driven membrane process powered mainly by electricity, while MSF and M…
• CSWRO needs steam from a co-located power plant, while MSF and MED run only on electricity…
• DMSF and MED product water still carries several hundred mg/L of dissolved solids, while e…

How do isobaric (pressure-exchanger) Energy Recovery Devices (ERDs) achieve energy efficiencies exceeding 95% in modern seawater reverse osmosis plants?

• ABy driving a Pelton turbine coupled to the high-pressure pump shaft to cut motor power
• BBy running a centrifugal pump in reverse as a turbine on the brine line to assist the hig…
• CBy passing pressure directly from the brine to incoming seawater inside rotor ducts, with…
• DBy throttling the brine through a control valve so that its energy heats the feed water

During seasonal red tide (Harmful Algal Bloom - HAB) events in the Red Sea and Arabian Gulf, SWRO desalination plants face acute membrane fouling risks. What advanced pre-treatment train provides the most reliable protection to maintain a Silt Density Index SDI₁₅ < 3.0?

• ACoagulation followed by dissolved air flotation (DAF) and ultrafiltration (UF)
• BCoarse bar screens followed by gravity sedimentation without coagulant
• CSingle-stage dual-media gravity filtration without coagulant
• DGranular activated carbon beds fed directly with raw seawater

Why are offshore multi-port diffusers for seawater desalination brine discharge designed with discharge nozzles oriented upwards at an inclination angle of 45° to 60° above the horizontal?

• ABecause brine is lighter than seawater, and an upward jet keeps it at the surface where w…
• BTo lower the jet velocity and avoid seabed scour, accepting lower dilution
• CBecause a horizontal or downward jet would give a longer mixing trajectory, so the 45°–60…
• DBecause the dense jet rises, then falls back along a long curved path, maximizing entrain…

What is the primary technological configuration utilized in a Zero Liquid Discharge (ZLD) desalination wastewater facility?

• AConventional SWRO with the brine returned to the sea through a multiport diffuser
• BHigh-recovery membranes, then a thermal brine concentrator and crystallizer leaving only…
• CHigh-recovery RO with the concentrated brine disposed of by deep-well injection
• DBlending the brine with treated sewage effluent and discharging it to the municipal sewer

Why is a velocity cap intake structure installed at the seaward end of an offshore desalination seawater intake pipeline?

• AIt turns the intake flow horizontal, which fish can sense and swim away from, reducing en…
• BIt acts as a chlorination chamber that disinfects incoming seawater before pumping
• CIt streamlines the pipe entrance, mainly to reduce head loss and pumping energy in the lo…
• DIt removes the need for onshore screens and cartridge filters

In coastal engineering, Hudson's formula is widely used to determine the required armor unit weight W for rubblemound breakwaters protecting coastal desalination intakes: W = (γ_r * H³) / [K_D * (S_r - 1)³ * cot(θ)]. How does the required armor stone weight scale with design wave height H?

• AArmor weight scales linearly with wave height: W ∝ H
• BArmor weight scales with the square root of wave height: W ∝ H^(1/2)
• CArmor weight scales with the cube of wave height: W ∝ H³
• DArmor weight scales with the square of wave height: W ∝ H²