Abstract:
Gampaha district which has the second largest population in the country consists of
many industrial establishments and residential areas. Attanagalu Oya Basin which
almost entirely the Gampaha district is a major hydrologic feature in
determining the seasonal variations of groundwater characteristics in the region. In
this study, the groundwater characteristics in the Attanagalu Oya Basin
analyzed both quantitatively and qualitatively to identify variations in the pre and
post monsoon periods. The qualitative parameters such as pH, conductance,
turbidity, calcium, magnesium, nitrate, phosphorous, ferrous, and heavy metal
concentrations were analyzed for samples taken throughout the entire basin for the
two time periods: pre and post monsoons. The groundwater quantity variations
were observed through data loggers and field surveys of water wells. These
recorded values were used to model the groundwater resources in the region using
two numerical models, MODFLOW by USGS and a self-written Fortran code. The
qualitative and quantitative variations were then analyzed spatially and temporally
to correlate with the upstream to downstream flow and the monsoonal recharge.
The possible reasons for the observed trends and variations were also studied to
provide recommendations for the sustainable management of the groundwater
resources in the Attanagalu Oya Basin.
