University of Twente Student Theses


Use of satellite products to assess water harvesting potential in remote areas of Africa: a case study of Unguja Island Zanzibar

Munyao, John Ngila (2010) Use of satellite products to assess water harvesting potential in remote areas of Africa: a case study of Unguja Island Zanzibar.

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Abstract:This study presents a methodology that can be easily applied to identify Rain Water Harvesting (RWH) sites using freely available RS products and GIS for data scarce areas of Africa. The potential of data integration (use of historical and near real time RS data, GIS and hydrological modelling) to assess the potential of RWH in combination with analytic hierarchy process (AHP) using spatial multi-criteria evaluation (SMCE) model as the GIS platform is exploited. The Integrated Land and Water Information System (ILWIS), a GIS software package is used to derive all the key spatial layers that are used for various analysis. Input layers derived for use in this model include rainfall, slope, soil groups, land use/cover, CN and runoff index with a spatial resolution of 30 metres. RWH maps indicating spatial extents of suitable areas for roof catchment (RC), Micro and Macro Catchment are the key outputs. Soil Conservation Service (SCS) is used for runoff modelling at pixel scale. About 84% of the total runoff is generated within flat and undulating slope classes. Masika rains (March to June) contribute 64% while the Vuli rains (October to December) accounts for 20% of the total annual runoff. Based on the developed model, the RWH sites identified relative to runoff generating areas produced 10.18 km2 suitable areas for roof catchment, generating 4.6 Million Cubic Metres (MCM) which can meet 33% of the total annual water demand. 30% of the island is suitable for micro-catchment RWH and 23% suitable for macro-catchment RWH representing a total area of 44,000 and 35,000 hectares respectively. Validation for micro-catchment RWH (based on existing and expert knowledge) shows that 10 % of the sites identified as suitable are unsuitable, 10 % in marginally suitable areas and 80 % within suitable and highly suitable areas. For macro-catchment RWH, 12% of the sites are in unsuitable areas, 20 % in marginally suitable and 68 % within suitable and highly suitable areas. The capabilities of using RS, GIS and field data for identifying potential sites for RWH technologies for decision making on development and management of RWH programmes is well demonstrated. The main constraint to the adoption of RWH could be associated with lack of knowledge among the decision makers and the community on existing potential for RWH for the island. RWH suitability maps developed in this study that give a clear indication of the spatial extents and the existing potential can be a starting point for creating awareness among stakeholder at the local and national scale.
Item Type:Essay (Master)
Faculty:ITC: Faculty of Geo-information Science and Earth Observation
Programme:Geoinformation Science and Earth Observation MSc (75014)
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