Wf

Efae is the field application efficiency Wsrz is the water stored at root zone Wf,: is the water received at field inlet

The field canal efficiency is the efficiency of water conveyance in the canals within a sector, block or sub-unit inside the oasis. The unit may be the tertiary unit, but may also be the quarternary unit or even the subquarternary unit. The exact definition of the "field" unit depends on the definition of the scheme as wall as on irrigation organizational aspects (farmers groups, irrigation groups). The canals at this level are usually unlined and seepage losses along them are high. Field canal efficiency is defined as:

E WfL

Efce W

Efce is the field canal efficiency

Wrf, is the water received at field inlet

Wrb, is the water received at block inlet

The conveyance efficiency is the efficiency of water conveyance in the main canal system, which transports and conveys water from the scheme head works to the various sectors, blocks or sub-units. The scheme head works may be the intake at the river of the storage reservoir, but it may also be the head of a tertiary unit in case the tertiary unit is considered as the scheme. Depending on the length of the canals and the porosity of the bed (lined, unlined, soil type) seapage and evaporation can be high. Conveyance efficiency is defined as:

Wrbl

Wr rhw

Ecoe is the Conveyance efficiency Wrb, is water received at the block inlet Wrhw is the water received at the head works

The distribution efficiency (Ede) is the efficiency of water conveyance and distribution between the head (inlet) of the scheme and the farm or field off take (turn-out/inlet). Covers all the losses inherent to the transport of the water and is a function of lay-out of the system, water transport type (canals, pipes), nature of the canal bed, soil type, maintenance, irrigation method and scheme management. The distribution efficiency is independent of crop type and crop stage it is expressed as follows:

Ede Ecoe Efce

Ede is the distribution efficiency

The overall, scheme or project efficiency now can be defined as:

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