Groundwater conditions in the multi-aquifer system in the delta, were studied through an integrated approach using hydrochemical, hydrogeological and isotopic techniques. This study was taken up because of the reported seawater intrusion into the groundwater system of this agriculturally rich region.
The study indicates that the recharge of groundwater by the canal system can be expedited by developing the canal network in the area as it has high potential for groundwater recharge. This will result in further reduction of salinity in the Krishna delta region. Further, Cl–/Br– ratio and stable isotopes (δ 18O and δ D) have been used to study the aquifer-aquifer interconnectivity and to identify perched aquifers within the study area.
The study of groundwater condition in the multi-aquifer system of the delta reveals the following -
- There is no present day seawater intrusion in any of the aquifer systems in the study area. The existing salinity that ranges from slight to moderate brackish quality in shallower and intermediate depths and highly brackish to saline quality in deeper depths in certain locations, is due to palaeo-geographic conditions, when the sea coast was more inland than at present.
- If a TDS value of 1.0 g/l is considered as salinity front, then at depths greater than 60 m bgl, the front is at present about 50 km away from the present day sea coast. The front is about 30–35 km from the coast at intermediate depths (30–60 m bgl) and is about 25–30 km at shallower depths (less than 30 m bgl).
- The major recharge areas lie in the northern part of the study area near the Prakasam Barrage and the area near Kaza where the canal network systems are intensively used for irrigation.
- The increased canal water irrigation has led to freshening of the groundwater that was saline earlier due to the presence of sea. The canal water irrigation must be intensified and extended to the southernmost part of the study area characterized by isolated aquifers.
The paper can be downloaded below -