| dc.description.abstract | Irrigation plays a critical role in addressing food security as envisaged in one of the six key
pillars (agriculture) of the Kenyan government's economic model. The government's
strategy, among others, seeks to ensure that agricultural activities are anchored on
technology to improve productivity and profitability while minimising the cost of
production. However, Ahero Irrigation Scheme, established in 1969, experiences
challenges with canal conveyance efficiencies, due to years of operation under imprecise
maintenance practices. Moreover, the performance of any open channel irrigation system
is a function of its canal conveyance efficiency among other factors, requiring
determination of the same. To overcome challenges with irrigation water conveyance at
Ahero Irrigation Scheme, the current study aimed to simulate conveyance efficiencies for
the Ahero Irrigation Scheme canal network to inform effective maintenance practices. The
Hydrologic Engineering Centre River Analysis System (HEC-RAS) model was used to
simulate the canal conveyance characteristics at the tail-end section of the canal network,
covering a total length of 2.6 km to inform on improved maintenance practices. Geometry,
flow and velocity data gathered from the scheme network was used to simulate different
flow scenarios to determine the optimal flow scenario for the canal network. Calibration
was conducted before the application of the HEC-RAS software with the simulated against
actual depth data, yielding a significant R2 value of 0.857. The study also estimated the
crop water requirement for rice using the FAO-CROPWAT model to determine any flow
deficit at the tail-end section of the scheme. The measured canal capacity in its
unmaintained state revealed a discharge capacity of 0.228 m3/s, which was significantly
lower than the minimum crop water requirement estimation of about 0.38 m3/s (a 40%
water deficit within the canal network). A comparison with the original canal design flow
capacity (0.45m3/s) also suggested a 49% drop in the carrying capacity due to dilapidation
and degradation. Simulations of the network suggests that the concrete lined trapezoidal
cross-section of the canal had a safe carrying capacity throughout the studied canal
network. Consequently, this study recommends canal upgrade (levelling bed undulations,
dredging, and smooth concrete lining) to attain the optimal flow capacity at the tail end of
the network. | en_US |
