Abstract:
The characteristics of surface and underground water are dependent on natural factors
in the drainage basin and vary with seasonal differences in runoff volumes, weather
conditions and water levels. Human interventions also have significant effects on water
quality. This study examined the spatial distribution of hydro-geochemical
characteristics of groundwater under different types of land use in Belihuloya minicatchment area. To investigate spatial variations of hydro-geochemical parameters the
water samples were collected during North Eastern Monsoon (NEM) and First Intermonsoon (FIM) seasons in 2014. 20 water samples were selected containing 10 from
springs and 10 from the selected wells. Spatial variation of pH and Ca in sample wells
and spring water showed different patterns when comparing of NO3, SO4, K and Na in
the area. According to the WHO guidelines lower levels of pH (4.5-5.5) were observed
of wells located in the western part of the middle catchment area and pH levels of all
spring water were within in the recommended level (6.4 to 7.4). Ca concentrations of
wells (Ca; 14.4-19.1 mg/L) located in the eastern part of the middle catchment area and
of springs (16,2-20.1 mg/L) located in down catchment area were higher than those in
the study area. However, all parameters of water samples were less than the WHO
recommended limits. The spatial variation of NO3, SO4, K and Na in the area showed
similar variations with the land use pattern in the area. Higher concentrations of NO3
(2.2-2.9 mg/L), SO4, (1.0-1.9 mg/L), K (4.7-9.3 mg/L) and Na (7.3- 9.3 mg/L) were
detected in well water along the Eastern part of the middle catchment area associated
with paddy, home garden and built-up area. Higher levels of NO3 (1.6-1.9 mg/L), SO4,
(1.6-1.9 mg/L), K (3.3-3.9 mg/L) and Na (4.4-5.3 mg/L) were detected in spring water
along western part of the upper catchment, eastern part of the middle catchment and
lower catchment area associated with paddy, home garden, pines, tea, built-up and
scrublands in the area. This study attempted to examine the spatial distribution of
hydro-geochemical characteristics of groundwater under different types of land use in
the Belihuloya mini-catchment area. However, the spatial variation of NO3, SO4, K and
Na in the area showed similar variations with the land use pattern in the area. Higher
concentrations of nutrients due to fertilization were noted along the paddy lands, home
gardens, tea and built-up areas, particularly in the middle catchment area where the
earliest land use type as forests was found. Lower levels of nutrients in groundwater
were observed along forested, scrubland and grasslands. The use of high yielding
varieties, intensive agricultural practices and changing the economic mode of
production since 1956 have considerably change the water quality. Hence continuous
monitoring of ground and surface water quality in the study area is necessary to avoid
the potential impacts to the water resources.
