Assessment of possibility of saltwater intrusion in the central Godavari delta region, Southern India

Oil exploration and development have taken place extensively in the near-shore waters of the Bay of Bengal for over two decades, with onshore coastal aquifers serving as a primary source of water injected into near-shore production wells for enhanced oil recovery. Field and modeling studies were initiated to assess the effects of potential seawater intrusion into the coastal aquifers and to improve strategies for groundwater development and management. Groundwater levels were measured at 42 locations in the central Godavari delta (295 km(2)) over a period of 2 years (2006-2007). These data indicated that the predominant groundwater flow direction consistently points toward the coast with no significant change in groundwater table elevations during the study period. Groundwater samples analyzed for major ions revealed the groundwater to be brackish in nature with an average salinity of similar to 5,000 mg L-1. A numerical model of variable density, groundwater flow, and solute transport (SEAWAT) was developed for the study region. After calibrating against observed hydraulic head data for the year 2006 at steady state, the model was used to predict the extent of seawater intrusion in the study area over the next 50 years. The estimated regional groundwater budget indicates a significant amount of groundwater outfall to the Bay of Bengal. The model predicts that the area will not be affected by seawater intrusion at the present rate of groundwater exploitation near the coast.