Preliminary study on geochemical classification of groundwater: A case study from water supply wells

Abstract

Regional classification of groundwater has useful applications in agriculture, ecology and human health investigations. It is important for the development of civilization and to establish database for planning future water resources development strategies. The hydro chemical study reveals quality of water that is suitable for drinking, agriculture. Presence of excessive quantities of sodium and chloride in groundwater are one of the major constrains in agriculture. Groundwater prospecting techniques and investigations are directed mainly at locating groundwater resources and also at understanding the formations of ground water systems with respect to the environment in which it occurs. The aim of the study was to present the detailed chemical facies of groundwater of water supply wells. The chemical quality of groundwater is related to the geology of the area. Major cations; Na", Ca, Mg",K", and Fe" and major anions; CSO, HCO, CO,, and NO were determined for nine water supply wells from October 2008 to January 2009 based on the Sri Lankan standard. The results of these analyses were plotted on piper diagram. Water samples were grouped into two major types, namely Ca and Na types. The results revealed that Chunnakam, Nilawari and Allappiddi water samples fall into Ca - HCO, type which is due to the influence of calcium carbonate rock. The water supply well at Valveddithurai, Puttur, and Velanai fall into Ca-Cl type and the Karavedddy, Arali and Vaddukkodai water samples fall into Na - CI type water. Sodium and Calcium are the major cations in groundwater. The groundwater from central part of Jaffna peninsula; Chunnakam and Nilawarai shows high bicarbonate water. Wells near the shore-lines areas, Valveddithurai, Arali, Velanai and Allappiddi, the quality changes to the chloride type due to sea water intrusion. However, some supply wells at Karaveddy, Vaddukoddai, and Puttur also shows higher chloride contents which could be due to mixture of recharging water and salt water up corning.