If the width of a river doubles while depth and velocity stay the same, discharge will:

If the width of a river doubles while depth and velocity stay the same, discharge will:

• A. Double
• B. Quadruple
• C. Remain unchanged
• D. Halve

Answer: (A)

Discharge is the volume of water flowing past a point per unit time, and it equals flow velocity times cross-sectional area (Q = V × A). For a river cross-section, A is width × depth. If depth and velocity stay the same and the width doubles, the cross-sectional area doubles as well. With velocity unchanged, the discharge must therefore double. The other outcomes would require changes in velocity, depth, or cross-sectional area beyond simply widening the channel.

Discharge is the volume of water flowing past a point per unit time, and it equals flow velocity times cross-sectional area (Q = V × A). For a river cross-section, A is width × depth. If depth and velocity stay the same and the width doubles, the cross-sectional area doubles as well. With velocity unchanged, the discharge must therefore double. The other outcomes would require changes in velocity, depth, or cross-sectional area beyond simply widening the channel.