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Case study · Pump station hydraulics

Stormwater pump station sizing & verification — coastal outfall, Abu Dhabi

Independent sizing and hydraulic verification of a stormwater lifting station that discharges to a sea outfall. The check used the network model’s inflow hydrograph, the ADM stormwater design manual criteria and an extended-period simulation in EPANET.

Location
Coastal development, Abu Dhabi, UAE

Scope
Pump selection, wet-well sizing, discharge hydraulics

Tools
EPANET with Python (EPyT)

Criteria
ADM Stormwater Design Manual Vol. I

1,811 L/s

Peak inflow (average 498 L/s)

2 × 905 L/s

Duty pumps at 10 m head

407 m³

Active wet-well volume (10 × 6 × 9 m)

≤ 2.28 m/s

Discharge velocity at peak flow

The challenge

A peaky inflow and a short route to sea

The upstream network delivers a sharp storm peak, about 3.6 times the average flow. The station must pass this peak without flooding upstream. It also has to keep pump starts within limits (10 per hour) and keep velocities in the DN800/DN1000 discharge main within the recommended range, in line with ADM design-manual §6.2.2 (wet wells) and §6.3.4 (pump capacity).

Inflow hydrograph to the pump station
Inflow hydrograph from the network model: 1,811 L/s peak

Our approach

Sizing and verification

  1. Inflow hydrograph and wet-well levels taken from the network model design scenario
  2. Pump capacity set per ADM §6.3.4: two duty pumps share the 1,811 L/s peak (≈ 905 L/s each)
  3. Minimum active volume V = 0.25 · Q · T = 407 m³ for T = 1,800 s (max. 2 starts/stops per hour)
  4. Wet well 10 × 6 m in plan: 6.79 m active depth, operating range 0.60 m to 7.39 m
  5. Pump and system curves checked in EPANET for one-pump and two-pump operation
  6. Extended-period simulation of inflow, pumped outflow and wet-well level, with HGL and velocity checks along the discharge route
Pump curves versus system curve
Pump vs system curves: duty points inside the preferred operating range

Results

Hydraulic simulation results

Hydraulic grade line at maximum flow
HGL along the discharge route at maximum flow (2 pumps)
Velocity profile along discharge route
Velocity 1.78–2.28 m/s (2 pumps), within the 0.9–2.5 m/s band
Extended period simulation of inflow, outflow and wet-well level
Extended-period simulation: inflow vs pumped outflow and wet-well level

Outcome

  • Single-pump duty ≈ 901 L/s at 9.0 m; two pumps in parallel ≈ 1,750 L/s at 9.6 m, both within the preferred operating range
  • The proposed 10 × 6 × 9 m wet well complies with ADM §6.2.2
  • The selected 2-duty pump arrangement (≈ 905 L/s at 10 m) complies with ADM §6.3.4
  • Discharge velocities stay within the recommended range for both one-pump and two-pump operation

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