How much of the Tharavai is under salt pans?

We compared today's satellite imagery with the Tharavai belt as it was mapped around 1920. On the map below, the blue line is the 1920 belt and the red areas are salt pans as they are today.

Salt pans (red) on the 1920 Tharavai belt (blue), Periyasamipuram to Mookaiyoor. Imagery: Esri, Maxar, Earthstar Geographics.

Between Periyasamipuram and Mookaiyoor, about 450 hectares of the old belt, nearly a third, are now under salt pans. Including the stretch south of Periyasamipuram, the total is about 855 hectares. This is how it breaks down:

• Periyasamipuram: 274 of 288 hectares of the old belt (95%)

• Vembar (west side and river mouth): 171 of 421 hectares (41%)

• Kannirajapuram: no salt pans on the 335 hectares of the old belt

• Mookaiyoor: 8 of 494 hectares (2%), though large salt works sit right beside the old belt at the creek mouth

• South of Periyasamipuram, towards the coast: 402 of 498 hectares (81%)

The loss is worst at Periyasamipuram, where almost the whole old belt has become salt works. About 100 hectares of salt pans also sit at the Vembar river mouth, exactly where the river used to feed the Tharavai. Near Kannirajapuram, the belt is still wet ground and Prosopis, which makes restoration there very practical.

Close-up: Periyasamipuram to Vembar. Imagery: Esri, Maxar, Earthstar Geographics.

How we measured: we outlined the salt pans by eye on current satellite imagery and laid them over the 1920 survey map of the Tharavai, fitted to today's coordinates. The old map is accurate to within a few hundred metres, so these figures are estimates. During the first year of the restoration project, the Tharavai Rehabilitation Committee and PAD will check the edges with GPS and against revenue records.