Abstract:
Sand dams are very useful in arid and semi arid lands (ASALs) as facilities for water storage
and conservation. Soils in ASALs are mainly sandy and major water loss is by evaporation
and infiltration. This study investigated the effect of sand media characteristics, specifically
surface albedo, grain size and stratification on water table recession using experimental
model. Tanks of 220 litres capacity and 0.9 m depth were set as evaporation media at the
JKUAT weather station in Kenya. Experimental media investigated were; fine ballast, fine
sand, coarse sand, in situ sand and stratified combination. Surface albedo were varied by
painting top sand media with colours such as white, grey and natural brown sand colour as
a control. Albedo were indexed using luminance factor. The study concluded that
evaporation losses are inversely proportional to the albedo of the evaporating surface
measured in terms of luminance factor. The relation between water table recession in
porous medium and pan evaporation is an exponential decay curve. The study showed that
stratification of media have significant influence on water loss particularly, if the overlying
material is courser than the underlying layers.
