The portion of liquid that enters a sewer system specifically due to rainfall (runoff entering inlets and conduits) is called:

Introduction / Context:
Understanding wastewater components is vital for selecting separate versus combined sewerage and for sizing conveyance and treatment units. During storms, an additional component beyond sanitary flow enters the system.

Given Data / Assumptions:

• Rainfall-runoff captured by drains and inlets.
• Terminology consistent with municipal engineering practice.

Concept / Approach:
Storm sewage (also called stormwater) is the runoff from rainfall or snowmelt conveyed by storm drains. In combined systems, it mixes with sanitary sewage; in separate systems, it is routed to storm drains and often discharged to water bodies after appropriate control.

Step-by-Step Solution:
Identify the source: precipitation-derived runoff.Match to standard term: storm sewage.Differentiate from sanitary sewage (domestic/industrial wastewaters).

Verification / Alternative check:
Definitions in textbooks consistently distinguish sanitary sewage (from households/industry) from storm sewage (from rainfall), with infiltration/inflow considered extraneous water.

Why Other Options Are Wrong:

• Industrial wastewater: Process discharges; not rainfall-derived.
• Sanitary sewage: Domestic wastewater independent of rainfall.
• Infiltration water: Groundwater entering through defects; not the same as storm runoff by definition.
• Leachate: Liquid from waste percolation; unrelated to storm drains.

Common Pitfalls:
Confusing storm sewage with infiltration/inflow; in practice all may co-occur but terminology stays distinct for planning and regulatory reporting.

Final Answer:
Storm sewage