Abstract:
This study was initiated to evaluate irrigation efficiency and water delivery performance of
the Guanta irrigation scheme using performance indicators such as conveyance efficiency,
application efficiency and water storage efficiency and water delivery performance
indicators such as adequacy, efficiency, dependability and equity as a tool and to recommend
appropriate measures to improve the scheme. Overall activities in primary data collected
included: field observation, discharge measurement in the canal, determination of moisture
contents of the soil before and after irrigation, determination of soil physical properties and
measurement of depth of water applied to the fields. For field evaluation of irrigation
efficiency of the scheme, using performance indicators three farmers’ fields was selected
from the head, middle and tail-end water users.
According to the results of the study, conveyance efficiency (EC), application efficiency (Ea),
storage efficiency (Es) and overall scheme efficiency (Eo) were determined and their mean
values of overall were found to be 73.56%, 37.56%, 88.04% and 27.63% respectively. The
conveyance loss at the main canal level was between 2.62% (0.0005m
3
/s/100m) to 32.09%
(0.004m
3
/s/100m). At the secondary canal level of the conveyance losses were between
26.59% (0.0011m
3
/s/100m) to 45.15% (0.0028m
3
/s/100m). The reason of this loss is the
sedimentation in the canal, seepage, inadequate management, by the domestic animals
during the time of water drinking, illegal uses of water of the farmer.
The water delivery performance of the irrigation system in the terms of adequacy (PA),
efficiency (PF), coefficient of variation (PD) and coefficient of variation (PE) was
determined and their average overall values were found to be 0.79, 0.78, 0.25 and 0.19
respectively. This shows that the adequacy and dependability of the system were poor and
fair for equity and efficiency. The poor performances of the system occurred due to
sedimentation of canals, illegal water abstraction, inadequate operation and maintenance
provisions and the weakness in water management.
