**Nomenclature**

*A* flow section area

*A _{c}* contracted area of flow

*A _{o}* orifice area

*a *area

*B* average width

*b _{c} *width

*C *Chezy factor, general coefficient, concentration of a tracer,
or constant

*C _{a} *gate angle correction factor

*C _{c} *contraction coefficient

*C _{d} *discharge coefficient

*C _{e} *effective discharge coefficient

*C _{v}* velocity of approach coefficient

*C _{va} *coefficient to account for exclusion of approach
velocity head

*C _{vf} *velocity coefficient caused by friction loss

*c* velocity of sound

*D* pipe diameter

*d _{v}* distance water will travel at a given velocity
in a pipe of constant diameter

*E *specific energy

*E _{%QCs} *error in percent comparison standard discharge

*E _{%QFS} *error in percent full-scale discharge

*e *a subscript denoting "effective"

*egl* energy grade line

*F *Froude number

*F _{b}* canal freeboard

*F _{c}* critical Froude number

*F _{p} *pressure force

*f* friction factor

*G _{o} *gate opening

*g *acceleration caused by gravity

*H *total energy head

*H _{c} *critical total energy head

*h* head or height

*h _{a}* measuring head

*h _{b}* submergence head

*h _{b}/h_{a} *submergence ratio

*h _{c}* critical head

*h _{cm} *critical hydraulic mean depth

*h _{e}* effective measurement head

*h _{f} *head loss

*h _{m}* hydraulic mean depth

*h _{v} *measured velocity head

*h _{1e}*

*h _{1} *head measure above a weir crest (upstream head)

*ªh* upstream head minus downstream head (differential head)

*h _{f(1-2) }*friction head loss between two stations

*hgl *hydraulic grade line

*K* constant

*k *boundary roughness size

*k _{b} *correction factor to obtain effective weir length

*k _{h}*

*L *length

*L _{b }*cross-sectional width

*L _{e}*

*N *sample number

*n *friction or roughness factor

*PH* pinion height

P_{w} wetted perimeter

*p* pressure or height of crest above approach invert

*Q* discharge

*Q _{a}*

*Q _{c} *critical discharge

*Q _{cs} *comparison standard discharge

*Q _{s }*suppressed orifice discharge

*Q _{eq} *discharge computed using measured heads and the
regression equation

*Q _{FS} *full scale or maximum discharge

*Q _{ind }*indicated discharge from device output

*Q _{max} *maximum discharge

*Q _{min }*minimum discharge

*Q _{t} *theoretical discharge through an orifice

*ªQ% *percent deviation of discharge

*q *unit or partial discharge

*Re *Reynolds number

*R _{h}* hydraulic radius

*r *ratio of suppressed portion of the perimeter of an orifice
to total perimeter

*r* radius of curvature

*S* slope or estimate of standard deviation

*S _{o} *invert or bottom slope

*S _{ws }*water surface slope

*s* estimate of standard deviation

*T* time

*T* top water surface width

*T _{c }*top water surface width at critical conditions

*t* time

*t _{d}*

*t _{u}* upstream travel time of the acoustic signal

*ªt* difference in times

*U* equation coefficient or exponent

*V *mean velocity

*V _{c}*

*V _{axial} *average axial velocity of water flow

*V _{0}* volume

*W* weight

*X _{avg}* mean of a set of values

*X _{ind} *each individual value from a set of values

*Z* potential energy head

ratio of orifice hole diameter to pipe diameter

unit weight of water

angle

kinematic viscosity

standard deviation