Aquifer Systems in Mahanadi Delta-Occurrence, Potential and Quality Characteristics

Mahanadi delta occurs on the east coast of India, in the state of Orissa. Groundwater is a major source of fresh water in the are., The permeable sand and gravel layers in the unconsolidated sediments form the potential aquifers, having a cumulative thickness of 15-65 m. Groundwater occurs under both confined and unconfined conditions. The depth to water table varies from less than 2 m to 4 m below ground level. The well yields vary from less than 35 m³/hr in the basin marginal areas in the west to more than 270m³/hr in the coastal plains in the east. K and S values of the deeper aquifers are in the range of 5-330 m/day and 1.75×10^-2-8.81×10^-6respectively. But the aquifers are beset with salinity hazards. The saline and fresh water profile is non-uniform with freshwater overlying/underlying or alternating with saline zones, or with saline water at all depths. However, the ground water quality is in general fresh (EC<1600 μS/cm) and suitable for all uses, except in areas having high salinity, and in localized pockets showing high concentration of iron, fluoride, nitrate and sulphate being injurious to health. The annual groundwater recharge is of the order of 35 1069 HAM, with gross draft of 39688 HAM. The paper presents the complex hydrogeological set-up in the delta and outlines groundwater development potentials.