Effects of farmer-initiated modifications of water control structures on performance of irrigation system:a case study of Mkindo Scheme, Morogoro, Tanzania
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Date
2000
Authors
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Journal ISSN
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Publisher
Sokoine University of Agriculture
Abstract
A study to assess the effects of farmer-initiated modifications of water control structures
on the performance of the irrigation system in Tanzania was carried out at Mkindo
farmer managed irrigation scheme (FMIS) in Morogoro region. The scheme had two
phases. The changes made on the original water control structures were assessed, the
performance of the existing water distribution system, and the effect of the existing water
control structures on performance of the irrigation system was evaluated.
The result of the study shows that changes were made by farmers on the original design of
already constructed water control structures in the scheme as follows: some of the field
canals and the original centrally located field drains were removed by farmers in order
to increase irrigable area (bigger utilised land area). Therefore, some farmers were
doing field-to-field irrigation method; the main drainage for phase-I has been converted
to field irrigation canal by nearby farmers; dimension of existing paddy field earth
bunds and secondary canal banks were smaller than original ones; water harvesting
from main and secondary canal by farmers outside the scheme exists and no water
control gates (wooden stop-logs originally provided) exists at division box openings and
at turnout level for the scheme.
Applicable indicators for the performance of FMIS are quantified as follows:-Overall
irrigation efficiencies were 6% and 8.3% for phase-I and phase-II of the scheme
respectively: Average productivity dropped from 6.6 ton/ha in 1995/96 to 3.1 ton/ha in1998/99 season. The organisation of Mkindo FMIS was appropriate, however, the
scheme was weak in irrigation management as the essential operation and maintenance
activities were not carried out effectively. The scheme had canal maintenance problem.
There was a corresponding big error in waler adequacy of 72% and 68% for both phase-
I and phase-II of the scheme respectively arising from improper water control along the
main canal and at secondary canal offtake. Both phase-I and phase-II of the scheme
were not able to distribute water equitably, reliably as well as maintaining a correct
field water depth from tilling to flowering and grain formation stage. This was shown
by relatively high error of equity of 18% and 20% for both phases respectively. These
figures are far greater than zero, which is the indicator for highest performance.
Therefore, the FMIS in Tanzania may perform better, or be sustainable, if original
design of already constructed water control structures are maintained (i.e. not changed)
by farmers at operation stage. This emphasises farmer’s involvement and empowerment
at planning, design and construction stages of the scheme.
Description
Dissertation
Keywords
Mkindo Scheme, Irrigation system, Irrigation method, Climate