TITLE:
Modeling Surface Water Availability for Irrigation Development in Mbarali River Sub-Catchment Mbeya, Tanzania
AUTHORS:
Moses Mazengo, Gislar E. Kifanyi, Edmund Mutayoba, Nyemo Chilagane
KEYWORDS:
Irrigation, Mbarali River Sub-Catchment, Surface Water Availability, SWAT
JOURNAL NAME:
Journal of Geoscience and Environment Protection,
Vol.10 No.4,
April
8,
2022
ABSTRACT: Although Tanzania has a large land suitable for irrigation development,
only 4.2% of the arable land which is potential for irrigation has been
developed. Mbarali District is characterized by commercial and small-scale
irrigation activities for paddy production. Currently, surface water
availability for irrigation in Mbarali District is dwindling due to high water
demands. Inadequate studies that estimate water availability for irrigation is
one of the underlying factors to the lack of irrigation development in many
parts of Tanzania including in Mbarali
District. This study, therefore, aimed to model surface water availability for irrigation development in Mbarali
River sub-catchment Mbeya, Tanzania. The Soil and Water Analysis Tool
(SWAT) model and field observations were used to accomplish the study. The
model estimates that Mbarali River sub-catchment receives about 631 mm of total
mean precipitation annually. About 53% of received precipitation is lost
through evapotranspiration, 12% recharged to deep aquifer and the remaining 35%
discharged to the stream flow through surface runoff, lateral flow and return
flow from unconfined aquifer. Discharge to the steam flow contributes to the
total annual means of river discharge ranging from 0 - 10 cubic meters per
second at upper catchment to 120 - 140 cubic meters per second at lower
catchment. The study recommends that the lower reach of the Mbarali River sub-catchment
is potential for irrigation than the upper reach as it has potential river flow
that can support irrigation activities. The study also notes the urgent need for
water reallocation plan to meet competing water needs in the lower reach of
Mbarali River sub-catchment. Moreover, the study addresses the potentiality of
irrigation in upper catchment under sustainable water management practices
including excavation of small ponds to capture and store surface runoff for dry
season use or to supplement irrigation as the rainfall declines.