Innovative coupling of hydrological modelling for IWRM: linking catchment functioning with socio-economic conditions in the Olifants
Date
2011-05-12
Authors
Magombeyi, Manuel Simba
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Abstract
Computerised integrated models from science contribute to better informed and holistic exante
integrated assessments of multifaceted policies and technologies. This view has lead to
considerable effort being devoted to developing integrated models to support decisionmaking
under Integrated Water Resources Management (IWRM). Nevertheless, an appraisal
of previous and ongoing efforts to develop such decision support systems shows that attempts
to address the hydro-socio-economic effects on livelihoods have been deficient and
fragmented. To date, no universal standard integration method or framework is in use.
Existing integrated models application failures have pointed to the lack of stakeholder
participation. In an endeavour to close this gap, this thesis focuses on an integrated model
development with prediction capability, ICHSEA, developed in Avenues script language in
ArcView 3.3, to take advantage of the mapping capability of ArcView. This model couples
existing hydrology (SWAT), agronomy (PARCHED-THIRST) and socio-economic
(OLYMPE) models to link livelihoods of resource-constrained smallholder farmers to water
resources availability at catchment level in the semi-arid Olifants subbasin, South Africa.
These three models were calibrated and validated using observed data and local stakeholder
participation, prior to coupling in the integrated model. All the models performed well in
representing the study conditions, as indicated by the statistical performance. The integrated
model is generally applicable to any catchment. The study methodology was inspired by the
need to enhance rural livelihoods and to close the gap of stakeholder involvement in building
and applying integrated models to ensure acceptability and application in decision-making.
Over 20 years, the predicted impacts of untied ridges and planting basins versus conventional
rainfed tillage on surface runoff reduction were 14.3 % and 19.8 %, respectively, and about
41─46 % sediment yield reduction in the catchment. At 90 % confidence interval, family
savings improved from US$ 4─US$ 270 under conventional rainfed to US$ 233─US$ 1 140
under supplemental irrigation. These results underscore the economic and environmental benefits that could be achieved by adopting the new crop management practices. A
relationship between maize crop evapotranspiration and family savings under different crop
management strategies was also derived for five farm typologies in the catchment.
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Keywords
food security, Farming system, Hydrological, Integrated model, Environmental benefits