how do you calcuclate water discharge??

Question

Hi i have a question and i was wondering how you solve it
river is 4m wide, 0.25 m deep and has a velocity of 1.0m/s. how do you calcualte the discharge in m3/s (that 3 means cubed)
i have no idea how to solve this and i would be grateful if someone could show me how??

Answer 1

Volume flow rate is described in most texts as Q

Q(discharge)=Area*Velocity

Area = 4m * 0.25m = 1 m^2

Velocity = 1 m/s

Q=1 m^2 * 1 m/s = 1 m^3/s

"Mdot" is mass flow rate in kg/s and is not appropriate for this problem.

Answer 2

Thermodynamics for 1-D flow
mass flow rate would equal

m_dot=rho*A*V (for 1-d flow)

where rho is the density, A is cross-sectional area, and V is the velocity normal to the area.

water's density is close to 1 so it is neglected from the equation
and you get the mass flow rate is equal to the area x velocity

m_dot= 4(m) * .25 (m) * 1.0 (m/s) = 1 (m^3/s)

Answer 3

took me forever, like 5 minutes +-, but isnt it also like 1/4- acre/ft per hour? never done this math before, couldnt find a conversion chart for cubic ft in an acre. my math may be screwy.