Performance evaluation of an indigenous irrigation system at towero village, western Uluguru mountains, Tanzania
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Date
2000
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Sokoine University of Agriculture
Abstract
Indigenous irrigation methods in mountainous areas are a result of people’s efforts to
survive on limited land resource bases. The adoption of an irrigation method depends
on whether it does not affect the soil. While surface methods are common in the
Uluguru Mountains, drag hose sprinkling is receiving wide use at Towero. Drag
hose sprinkler irrigation refers to the local use of sprinklers where water pressure is
obtained by gravity flow.
Effects of indigenous irrigation systems’ practices on soil erosion were evaluated
using field data and aerial photographs. Field data were obtained from six slopes,
ranging from 6 to 84%. Two versions of aerial photographs were used to produce
land-use maps for 1964 and 1992, respectively. Traversing produced the land-use
map of 1999.
Land-use analysis revealed that between 1964 and 1999, the area under indigenous
irrigation increased by 0.81 ha/ycar. Between 1964 and 1999 the settlement area
increased by 0.83 ha/year. Deforestation rate was 6.48 ha/year.
Mean crop yields for leeks ranged between 9.65 — 13.53 tonne/ha. Mean specific
yields ranged between 0.65 - 1.09 kg/m3. Mean water conveyance, application and
storage efficiencies were 83.72%, 86.20% and 99.64%, respectively. All fields wereii
over-irrigated based on soil moisture data which were taken daily. Over-irrigation
caused inequitable water distribution.
Daily sediment load transport in canals A, B and C were 22.2 kg, 187.6 kg and 54.7
kg, respectively. Total sediment loss was 264.6 kg per day. Net downslope splash
loss at 84, 70, 65, 24 and 15% slope was 28.9, 19.1, 12.0, 6.0, and 1.0 kg/ha,
respectively.
The effects of indigenous irrigation systems’ practices at Towero were: soil loss in
the form of splash erosion and sediment load transport, and acceleration of
deforestation in pursuit for more agricultural land. Hence, efforts to promote soil
conservation practices at Towero are essential.
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Keywords
Indigenous irrigation system, Uluguru mountains, Performance evaluation