Abstract:
Small reservoirs are mainly utilized for domestic purposes, livestock watering, fishing and
irrigation. In spite of their importance in water resource provision, planning and management,
recent studies have shown that the major factor militating against reservoir study is high
survey cost and lack of equipment especially in developing world. Two aspects of reservoir
dynamics were studied: shoreline changes and bathymetric map production as baseline data
for future studies. Landsat imageries covering the study area were acquired for the periods of
1986, and 2002 for the purpose of determining the extent of shoreline changes during these
periods. The Normalized Difference Water Index (NDWI) map of the reservoir was
generated in ArcGIS environment; then the shorelines of the reservoir for each of the periods
under consideration was extracted from the NDWI using slicing and reclass operations in
ArcGIS. Shoreline for each year was overlayed and shoreline change detection map of the
reservoir was subsequently produced. A simple, less costly method with good enough
accuracy was applied for rapid bathymetric survey and map generation (as developed by ITC,
Enschede, The Netherlands). Transect lines and points were generated from IKONOS
satellite imagery and uploaded on to handheld GPS for navigation, while observation was
carried out at each of the transect points generated using dual-frequency GPS. The location
coordinates as well as the depth at each of the transect points using handheld depth finder was
determined and recorded. Interpolation analysis operation was performed to produce
interpolated surface which was then used for modelling the reservoir bed. The outcome of the
research shows a decrease within the 16 years period of investigation (1986-2002) as
revealed, from 440,000m2 in 1986 to 410,000m2 in 2002. This shows a reduction of
30,000m2, with an annual decrease rate of 1,875m2. The bathymetric map generated revealed
a maximum depth of 4.12m and a minimum of 1.12m Also landuse/Landcover change were
observed which could be a factor to reservoir change especially on its shoreline.
