It’s too salty without coastal dunes

I was in Rameswaram looking through my route for the next part of the journey with a friend. About 100 km along the coast there were these series of ponds and water bodies that he spotted on the map. It was something neither of us had seen before. Take a look at the picture.

Hundreds of lakes and ponds. I was excited at the sight of so many of them. Immediately, I thought of the many times I could be cooling off during the day when it gets too hot from cycling. But it wasn’t many of them I could take a dip in. Because these terrain maps are far from the polluted reality.

Many villages are dependent on these for bathing, washing clothes, vessels etc. It was alright that they are using it and thus have a direct relationship with a natural source of water. But it is the lack of hygiene that would bother an outsider. Some ponds are managed strictly well, especially if it is associated with some religious stories. But mostly, you wouldn’t want to touch the water. It’s probably because they use a pond for all reasons throughout the year. The water has to take in body soap, washing soap, and that of cooking vessels. It would be a little different if it was a flowing water body. They just need to find a better way to use this good source.

Just as I’d cycled past this region, my brother spoke to me from another part of the world. He had checked out my route called me about it. He said, the water bodies in abundance suggest the presence of coastal dunes in that area. He’s had some serious lessons in Geography recently. Naturally, his point of view would have to be ‘significant.’ This got me curious and I did some investigating as I cycled up.

This georgraphical feature has been created over a 1000 years or so to cause hundreds of lakes and ponds around the region of Thondy and Manamelkudi. From a few sources, including Singaravelu and C Rajasekaran, I learnt that this particular phenomenon may have occured when the ocean receded outwards, away from land, over centuries. Apparently, “the ocean continues to recede on the eastern side of India, while coming inland on the western coast.

During this process of recession, water is captured in the form of these lakes and ponds where the terrain is uneven. This was the beginning of the waterbodies that can be seen in the map. Historically speaking, there has been enough salt water that has seeped into the ground around this coastal region. In some regions, especially a little north around the Kaveri river delta, the river flowing upstream brings saltwater from the sea. (During my journey up here, we caught some sardines at the Ambuli river– a typical saltwater fish. I didn’t know until then that a river would flow upstream in a different time of the year.)

Coastal dunes also occur when the ocean recedes back into the sea. The onshore winds help in carrying loose sand over to the little heaps (uneven terrain). The sea is shallow here in this region and it is receding. Over the last 30 years itself, the sea would have gone back by some 40 – 50 meters, says C Rajasekaran. When there is a low tide, there is a lot of dry land left and as the wind blows onshore, it carries the soil.

You should know that carrying loose soil over to a place by wind is not enough to capture and create coastal dunes. The most important part of the phenomenon lies in the coastal vegetation. In several places along the Tamil Nadu coast, you will find the following species: kandan kathiri, ipomoea pes-caprae [kuthirai kuzhambu], uppu aragu, spinifex littoreus [ravanin meesai], and casuarina. These coastal floral species have properties that help in binding the soil together, each through its own quality in a unique way. Except casuarina, the rest are pil vagai which creep on the ground. (After having learnt about this, I kept getting off my cycle to check coasts for these species. Everywhere I saw any of these species, there were dunes formed.)

There have been government-funded projects before where people tried to create coastal dunes by trapping soil caused by wind erosion using walls and clumps of rocks together, says C Rajasekaran. He scoffs at such people that turn up to make such a joke out of themselves and is quite i­­­­­rritated when funding gets wasted into such absurd projects. Without natural coastal vegetation it is impossible to create dunes, he says.

One of the projects that was being implemented by the state forest department funded by the World Bank, was to protect the coast line by planting coastal vegetation that would help in building dunes. It seemed alright until the implementation began. The forest department around this region (southern part of Nagapattinam district), began planting too close to the high tide line. Not just that, the forest department was only planting casuarina.

[A line of casuarina was planted by the forest department too close to the high tide zone. The dune is now grown like a wall nearly 10 feet tall. Turtles obviously cannot cross this boundary for nesting.]

Noticing this, he immediately met with the relevant forest officer and explained to him the danger in doing such a project as that would inhibit olive-ridley turtles from nesting if dunes formed too close to the sea. Turtle conservationists from Chennai had noted the unscientific execution of this project in Kancheepuram district and blew the whistle on the poor implementation. The project was quickly brought to an end. But the initial implementation had already happened in the areas in front of the village where C Rajasekaran resides. Since the time of Tsunami, where these casuarina trees have grown, you can see huge wall-like dunes since the trees were planted in a line close to the sea. There is casuarina plantation further inland that were planted through this project. He says, a good mix of all the different species are essential to build natural dunes rather than the current wall-like structures that exist.

Ground water salinity and the state of this belt today

There are several natural factors that will increase the ground water salinity in a coastal region: receding ocean, impermeable clayey soil too close to the top layer of soil, rivers flowing upstream. To naturally combat these and still provide freshwater from the ground, coastal dunes will play the role of natural rain water harvesting systems. For instance, the dunes formed may be at a height above sea level and only contain loose permeable soil. Thus, rainwater can be easily captured and stored where there are dunes. They help in keeping the ground water table healthy, both in terms of salinity and water level. Where there are dunes, there is bound to be fresh water underground even if it is close to the sea. Around here, fresh water can be found just 15 ft below the soil. Below that is clayey soil, which doesn’t help in percolation. Below the clayey soil is salty water.

There was a Tsunami in June/July 1943 that caused the water to gush in along the coast of Tamil Nadu. The salty sea water quickly seeped underground covering an area of about 15 acres near Vettaikaran Iruppu. At that point the water table was quite low, as it was just after the summer season. The sea water easily found its way to mix with ground water and thereby, increasing slainity, according to C Rajasekaran. In 2004, the Tsunami hit much harder at tremendously larger scale in December after the rainy season when the water table was much higher. So the effects could have been far worse had it happened in summer with a lower water table when you look at groundwater salinity after the Tsunami.

Over the last few decades, the coastal belt has been taken over mindlessly by salt corporations, prawn farmers, and several residential construction over dunes by towns, and villages. When dunes are being cleared, and built upon, rainwater cannot recharge ground water sources.

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Shrimp farmers harvesting a catch

On the other hand, several acres of salt pans by the shore have also been adding salinity to the underground water table due to their high salt content. These salt pans, prawn cultures also consume freshwater which are again sourced from nearby villages/towns.

Not all salt pans consume sea water for salt crystallization. The smaller pans a little inland, who don’t have afford access to the sea water use bore-wells. Bore-wells are used to dig suck up water below the clayey soil which contains saltwater. Bore-wells cause a low pressure area under water, and end up mixing saline sea water into the drinking water zones, according to V Marimuthu a resident of Kadinalvayal – President, Parent Teacher’s Association. However, salt water percolation through clayey soil needs to be scientifically studied here, as there are contradicting theories on this issue among different people. The bores go 80 to 100 ft depth.

Local communities and the salt corporation compete for this precious ground water source. “Today, it is hard to get fresh water from underground sources. They are starting to mix with salt water, and the water table has also gone lower by 4-6 feet after competetive consumption and altering of the dunes. The water has also become hard,” according to Mr.G Singaravelu, who is also a project advisor for WWF. “Lakes provided some comfort and help in balancing the salt levels underwater; rain water harvesting is essential and it will help in mixing with ground water therefore very essential,” says V Marimuthu.

Today, the only relief having lost the natural ground water source, is to deplete the more inland sources for fresh drinking water. The government has introduced the kollidam koottu kudineer thittam, 10 years ago, which ensures free supply of drinking water for villages, and with a small upfront fee for townships, transported from neighbouring sources.

The following shows a rainwater harvesting unit that runs 40 ft deep. The rainwater is collected and sent deep underground to recharge and desalinise groundwater. If every household does this in several villages, these folks believe that the salinity could be reduced and groundwater can once again be drawn for domestic purposes.

The abundance of karuval plant is adding to the deadly situation as it sucks up way too much water while making it difficult to survive for any other species. Although they are supposed to be uprooted under a government plan, there hasn’t been much work progressing on this front.

Retrospectively speaking, resources have been artificially depleted where it could have been conserved if the geography was understood at the right time. There is also an increasing awareness on mangrove cultivation for the very same reason in this region. Like C Rajasekaran mentioned that dunes cannot be created artificially, it is imperative to understand that healing can happen only through natural elements.

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