Water Conveyance Loss and Designing Conveyance System - Practices of Irrigation and On-farm Water Management - page 7

that the heads on the areas within and outside the cup are equal. The seepage rate is
computed from the weight (and then converted to volume) of water lost in a known
period of time and the area covered by the meter, i.e.,

S = V /( t × A ) (1.4)

where

seepage rate (m 3 /m 2 /h)

=

S

volume of water lost (m 3 )

V =

t = time period (h)

area covered by the meter (m 2 ) A =

1.1.5 Estimation of Average Conveyance Loss
in a Command Area

Conveyance loss here means the percent of the water lost reaching the field plot on
the basis of water diverted and can be calculated as

C AL = ( Q d − Q p ) × 100 / Q d

(1.5)

= ( C L × L av ) / Q d

where

C AL

is the average conveyance loss in percent

is the pump discharge or inflow in m 3 /s Q d

is the measured discharge at field plot in m 3 /s

Q p

is the average steady state conveyance loss (m 3 /s) per 100 m

C L

L av is the average channel length of the field plots (m)

To obtain the average channel length, the command area may be divided into n
unit areas considering the distance from the pump. A representative diversion point
for each unit area may be identified and the length of the channel section from the
pump to the diversion point be measured. The average channel length can then be
calculated as

L i n

L av = (1.6)

where n is the number of the section.
Discharge measurement may be done by a cutthroat flume or other available
technique.