Application of GIS-based spatially distributed hydrologic model in integrated watershed management: a case study of Nzoia basin, Kenya
Abstract
Application of GIS-based hydrologic models in management of watersheds in developing
countries has lagged behind due to unavailability of adequate spatial datasets. However,
use of spatial datasets from different sources, even if the datasets exhibit mismatch in
scales may still go a long way in helping understand basin hydrologic processes for the
purpose guiding broad policies in watershed management in developing countries. The
overall objective of this study was to use Famine Early Warning System Flood Model to
study effect of land use / land cover change on River Nzoia flows. The results are
considered an important input in policy documents for integrated watershed management
for the basin. Land use / land cover grid data were processed for the years 1986 and 2000
in IDRISI Kilimanjaro environment while other grid datasets were processed in case of
rainfall from point observations in Arc View. Soil parameters were clipped from USGS
continental scale datasets. Famine Early Warning System Flood Model runs as an
extension in Arc View environment.
The study revealed that the direction of land use / land cover change for the analyzed
years was from forest and shrub land to farmland. Model calibration indicated reasonable
correlation between observed and simulated flow during low flows and poor correlation
for high flows, an anomaly which was attributed to poor rainfall data network, resulting
in non-uniform sampling rainfall grid data. Analysis of change of land use / land cover
between 1986 and 2000 on river flow revealed that change in land use / land cover
resulted in increased hydro graph peaks which increases the chance of flooding.
Publisher
Department of Geography and Environmental studies