Identification of seawater intrusion signatures through geochemical evolution of groundwater: a case study based on coastal region of the Mahanadi delta, Bay of Bengal, India

摘要

The study dealt with seawater intrusion process in a coastal aquifer system in the Mahanadi river delta region in the east coast of India along the Bay of Bengal. The aquifers of Mahanadi delta are characterized as shallow aquifers ( 50 m) and deeper aquifers (> 50 m). Electrical conductivity (EC) of groundwater varied from a fresh of 146 mu S/cm (NW of the Mahanadi delta) to a saline of 33,900 mu S/cm (close to sea coast) with cation dominance in the order Na+ > Ca2+ > Mg2+ > K+ and anion dominance of Cl- > HCO3- 42 parts per thousand for delta H-2, implying the mixing of saline water and fresh groundwater in the coastal region of the Mahanadi delta. The proportion of seawater in groundwater was estimated to vary from 0% in the upper-delta formation to 72% in the lower-delta formation of the Mahanadi delta (close to seacoast), which was due to inland intrusion of seawater. In a first ever study on this coastal aquifer along the Bay of Bengal, where a large population is dependent on agriculture, seawater intrusion into the fresh groundwater has been quantified. The issue of seawater intrusion into the coastal aquifer in this region may become a serious disaster, if appropriate management strategies are not implemented in time.