Sea Water Ingress Study along the Guhagar Coast of Maharashtra with Reference to the Harmonious Water Resource Development

Konkan coast line in general and Guhagar coast line in particular is faulted in nature and endowed with a variety of coastal landforms and drainage patterns. Well inventory data reveals the presence of the beach rock-, mud-and basaltic aquifers. Out of these, the beach rock aquifer overlaps with spit-, the mud aquifer with flats- and basaltic aquifer with the uplifted abrasion platforms. The data also indicate that the groundwater level fluctuations for pre- and post-monsoon seasons range from 1.95 m to 3.10 m, 2.10 m to 2.90 m and 2.40 m to 5.75 m in the beach rock-, mud- and basaltic aquifers respectively. The average rise in groundwater levels due to sea water ingress under high tide condition is of the order of 0.59 m, 0.67 m, and 0.86 m respectively in the beach rock-, mud- and basaltic aquifers. Lowering of groundwater levels and pumping during pre-monsoon (summer) season are responsible for upconing of fresh- and sea water interface. It has been inferred that landward limit of the spit and abrasion platforms constitutes the ancient strand line whereas sandy beaches and mud flats the present strand line. The ancient strand line is the landward limit, and the fresh- and sea water interface is the vertical limit of subsurface sea water ingress. The regulations to be adopted for maintaining the delicate equilibrium of fresh- and sea water have been listed. The pros and cons of constructing engineering structures for preventing sea water ingress and strategy to enhance groundwater recharge for increasing fresh water column in the lower reaches of creeks, tidal inlets and their tributaries, without causing harm to the delicate ecosystem of mangroves, have been discussed.