With a 187 km coastline, Nagapattinam is spread across an area of 2716 sq km. Rice takes a big share of the area under cultivation, followed by black gram, green gram, sugarcane and groundnuts. 14 out of 17 river systems in Tamil Nadu flow through the plains of Nagpattinam and drain into the Bay of Bengal. Nagapattinam receives 60% of its rainfall during the north east monsoon and 40% during the south west monsoon.

Although the river systems are divided into irrigation canals supporting agriculture, for the past few years, this system has not been adequate for the three seasons of agriculture normally practiced in Nagapattinam. Totally dependant on the Mettur dam for their base flow of water, these canals have water only from July to early February, when the shutters of the dam are opened to provide water for irrigation.

Thus the patterns of cultivation have changed to adapt to the period when water is available, either in the canals or during the monsoons. Agricultural activity has reduced from three seasons of cultivation to just one season which is mainly during the north-east monsoon, generally after  September.

The local level adaptations to suit the decrease in water availability, range from cutting down the number of seasons of cultivation, moving from long duration variety of paddy to short season varieties, reducing land under paddy cultivation, and even shifting from paddy to plantation crops like casuarinas.

However, during the monsoons, the rivers are full, bearing all the excess water from the adjoining districts to Nagapattinam. Given the flat terrain, indicative of a delta, Nagapattinam has a very poor gradient, which is not conducive to a smooth draining away of the excess waters unless the canals are in good condition. Any blockage due to siltation, overgrown weeds, broken shutters or encroachments, can lead to an overflowing of water, thereby flooding the adjoining fields.

During the rest of the year, when there is no base flow of water, this flat terrain and the criss-crossing canals again work against the interest of the farmers as they become conduits for the backflow of the sea water during high tides, accelerating the ingress of salinity further and further inland. This ingress has badly affected the productivity of the land and farmers have had to abandon cultivation in such areas which have become too saline for agriculture.

Efforts are being taken to promote reclamation of such salinity affected areas, cultivation of alternate crops that are saline tolerant and shifting into horticulture for spreading the risks..