OF LAND USE CONVERSIONS ON WATER YIELD
E R N Gunawardena
University of Peradeniya
Trees use more water than shorter vegetation due to comparatively high
interception and evaporation losses. These losses also vary with the different
tree species and climatic conditions. In high elevations, trees could
offset the interception losses by capturing horizontally driven fog into
the catchment system. Therefore, it is important to study the hydrological
processes which would help to estimate water use of different land cover
types which in turn is required to find the effect of land use conservation
on water yield.
Only two studies with limited duration have been carried out to find the
effect of land cover on a few hydrological processes in 1977 and 1988.
Therefore, a long-term research project has been carried out since 1993
at two sites, namely at Dodangolla and Horton plains, to monitor the hydrological
processes in detail under different land use types. Home gardens, grass
and Acacia are being selected at the low elevation site, while montane
forests, grassland and Pinus are being selected for the high elevation
These two sites are instrumented with automatic weather stations which
monitor rainfall at 5 minutes intervals and other climatological parameters
at hourly intervals. Net rainfall gauges with tipping buckets are installed
to measure interception. Soil moisture is being monitored with access
tubes and neutron probes at the two sites. A fog collector is installed
at the Horton plain site to measure the horizontally driven fog at hourly
The results from this study will be used to calibrate a water use model
for different land use types. Once this is accomplished, the model can
be used to predict the effect of land use conservation on water yield.
Department of Forestry and Environmental Science,
of Sri Jayewardenepura,Sri Lanka. 1999. All rights reserved.