Performance evaluation of an indigenous irrigation system at towero village, western Uluguru mountains, Tanzania

Thesis

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.