| Abstract Submission No. | ABS-2.3-0234 |
| Title of Abstract | Coastal groundwater salinity and submarine groundwater discharge dynamics under the land use change and sea level rise in the case of Central Godavari delta |
| Authors | L.Surinaidu*, P. Rajendra Prasad |
| Organisation | Groundwater Hydrology Division, NIH |
| Address | NIH Roorkee, uttarakhand, India Pincode: 247667 E-mail: suryangri@gmail.com |
| Country | India |
| Presentation | Oral |
| Abstract | Central Godavari Delta in East Godavari District, Andhra Pradesh, a fertile region with intensive irrigated agriculture and expanding aquaculture. Utilizing an integrated approach combining geophysical surveys, hydrogeochemical analysis, multivariate statistics, and density-driven SEAWAT modeling the study investigates the origin, transport of salinity and submarine groundwater discharge in the alluvial aquifer system. The region supports three annual cropping cycles, predominantly paddy and aquaculture, with consistent canal irrigation. Although surface water is abundant, limited groundwater use has intensified near the Ravva onshore terminal, where continuous pumping since 1991 (600 m³/hr per well) has led to saline upconing. Groundwater levels are generally shallow (1¿12 m bgl), with minimal seasonal fluctuation. ERT surveys delineate thick marine clays (0.5¿1.0 ohm-m) underlying sandy clays, indicating in situ salinity, especially around Ravva. Water quality data (2006¿2016) reveals increasing Na-Cl and Na-Mg-Cl water types, indicating seawater mixing and evaporite dissolution. Stable isotopes (δ¹⁸O) and bromide tracers support mixing processes. Multivariate analysis shows that geology more than agriculture is a key driver of groundwater chemistry. However, expanding aquaculture (noted from 2006¿2024 land use data) contributes significantly to surface infiltration of saline water, intensifying shallow groundwater salinity. The SEAWAT model simulates regional groundwater flow and salinity transport, showing flow toward the Bay of Bengal without seawater intrusion but with local upconing at Ravva. Estimated groundwater inputs include 13.4 MCM/yr of recharge and 1.9 MCM/yr lateral inflow, with 5.1 MCM/yr extraction and 5.0 MCM/yr submarine discharge. Overall, this study provides critical insights into recharge mechanisms, aquifer salinization due to both natural and anthropogenic factors, submarine groundwater discharge and the need for sustainable groundwater management. The integrated methodology offers a robust framework for assessing coastal aquifer vulnerability to salinity and guiding future land and water use planning. |
| Keywords | Godavari Delta, groundwater flow, salinity transport |