Macro-catchment rainwater harvesting systems: Challenges and opportunities to access runoff
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Date
2010
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Abstract
Rainwater harvesting (RWH) is the process of interception and concentration of runoff and
its subsequent storage either in soil for direct use by plants or in reservoirs for later
application when needed to mitigate dry spells. RWH varies from macro to micro to in-situ
systems based on the size of the catchments and runoff transfer distances. Macro RWH
systems with or without storage has shown to be more applicable among communities as
compared to micro catchments RWH systems. The study aimed at looking on the
complexity of biophysical and social economic factors affecting potentiality of the use of
runoff harvested from macro catchment. The results of the study identified two broad
categories of constraints which are hydro-climatic and management of harvested runoff at
the farm level scale. The hydro-climatic challenges are more related to climate while
management looks on the transaction cost reflected on the maintenance of the systems,
equitable access to runoff and related resources. Results indicated that during the short rain
season, the seasonal rainfall amount received does not meet maize water requirements,
hence requires supplementary irrigation water to mitigate dry spells. Other biophysical
challenge is the change of the runoff conveyance channels due to erosion and deposition.
The results showed that fields in close proximity to runoff sources can receive from 70
m3/ha to 300 m3/ha of runoff and the crop yields on these fields that received extra water
from external catchments (macro RWH), increased by more than 120% as compared to
fields that received rainfall only. The result also showed that the amount received in the field
is not the only factor that can contribute to the water use efficiency but also depends on infield
management. The study therefore, recommends that the modeling of macro
catchments RWH models should not only deal with hydro-climatic challenges but also
looks on the social economic for efficient and equitable distributions of resources runoff
from macro-catchment.
Description
Journal of Animal & Plant Sciences, 2010. Vol. 7(2): 789- 800.
Keywords
Rainwater harvesting system, Macro catchments, Risk of flooding, Simulation models, Rainfall, Runoff, Rainfall