Salinity in coastal groundwater is a widespread problem and may be caused by individual or combined effects of inherent salinity, tidal effect, irrigation by saltwater and by seawater intrusion due to extensive pumping.
A study had been conducted by the High Level Commission set up the Government of Gujarat in 1977 to assess salinity scenarios in the area owing to sea-water intrusion. A comparison of salinity scenario within the intervention and non-intervention sites has been carried out under the present study to understand the outcome of intervention as also to identify the likely causes of salinity. The study indicates the following -
- The tests on water samples from ninety wells in pre-monsoon period indicate that the salinity ingress profile in 2006 is within 7.5 km to 9.5 km inland on an average, while in 1977 it was observed within 5 km to 7.5 km. This indicates that the intervention is not very effective on a macro-scale but there is some influence of structure in micro-scale.
- Comparison of salinity ingress trend with respect to distance and intensity is also carried out for the sites. Considering the history of water resources of the area, it is found that in the 1960s, the withdrawal rate of groundwater became 10 to 25 times more than that of previous decades. This extensive pumping caused imbalance in recharge and withdrawal phenomenon leading to sea-water intrusion.
- Salinity ingress distance and rates are not uniform along the coast. The phenomenon is very much dependent on local altitude and geological features. The complex geological formation may be facilitating salinity ingress in Veraval area while compared to others.
- Spatial distribution of aquifer diversity, hydrological aspect, rainfall variability, geochemical property and structural efficiency should be understood and integrated in a normalized scale. Based on this understanding, the type, location and capacity of preventive measures should be accordingly designed.
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