An assessment of groundwater quality in Kottukal microwatershed in Thiruvananthapuram district, South Kerala

Abstract

The Kottukal microwatershed is an uplifted sedimentary watershed of recent origin formed due to large scale neo-tectonic activity. The groundwater from this watershed is largely abstracted for both irrigation and local public drinking water supply schemes. The present communication is an attempt to assess the detailed groundwater quality of the unconfined aquifers and the stream water system within the microwatershed. The Hill-Piper diagram indicates majority of groundwater samples are found to be Na-Cl followed by a mixed and Ca-HCO3 type. The Na-Cl characterization of groundwater in this elevated terrain is not due to primary salinity, but could be attributed to combined effects of irrigation salinity and improper sanitation facilities. The values of total dissolved solids and electrical conductivity in groundwater samples are low as compared to stream water samples, suggesting distinct imprints of hydro-geochemical behaviour. The Wilcox diagram indicates, 90% of water samples falls in the C1-S1 sector depicts its suitability for irrigation. The total coliform and faecal coliform count of > 1600 MPN is noted in 88% of water samples. The alkaline trend and high bacteriological contamination points to the prevalence of a non-sterile environment resulted from agronomic practices and poor environmental sanitation facilities within the watershed.