• Member
• April 16, 2024

EcoDredging And Flood Mitigation By Madhukar Swayambhu

Historically, tanks and lakes were an important source fulfilling Water demands of the population. Kautilya’s Arthashastra (4th century BC) gives explicit information regarding the construction of dams, canals, management of canal Water, including exemption from tax. Rules for the location of tanks were also outlined. According to the Smritis, persons who breached tanks were given the death penalty by drowning in the tank Water. – And this was a practice and norm documented 2,500 years back in our country. Even prior to that in our scriptures like Skand Puran, Matsya Puran and Padm Puran there are various hymns or Shloks dedicated towards the science of Waterbody maintenance.

Many citations can also be seen in the epics of Ramayan & Mahabharat. The entire episode of Yaksh & Yudhishthir conversation has many coded descriptions of lake salinity, lake contamination and eradication of the pollution, and it happen exactly on the bank of a lake, wherein all Pandavs go one by one in search of Water to quench their thirst and take Water to their brothers and Mother. The importance of Water and underground aquifer is again described in Mahabharat when Pitamaha Bheeshm fall down and seeks Water to drink.

Even in recent history of last 2000 thousand years, Earth dams as well as masonry dams were constructed in very large numbers, in tens of thousands, from the 2nd century to the 17th century. The dams were constructed across the same river, one below the other, as well as across its tributaries. One such series of tanks in Mysore had no fewer than 1,200 inter-dependent tanks. The total numbers of tanks in Mysore was 37,000, the largest of which had a surface of 40 sq.kms.

Thus understanding Water, its importance and maintenance of the Waterbodies have been intrinsic part of our cultural ethos and social value system since time immemorial. 

Coming to the post-independence era, as per a study, there were 43,000 tanks in Chennai which were functioning in the 19th century 10,000 tanks were in disrepair. The area irrigated from these tanks exceeded 1,415,000 hectares. While today after 75 years, we all know Chennai is almost on the verge of hitting ZERO day.

In Madhya Pradesh alone, there were 50,000 small private tanks which irrigated 262,600 hectares. According to the Survey and Settlement Records of the Government prepared in the early 1930s, there were 937 lakes, tanks and Waterbodies in Bangalore. The area of the tank-bed of these Waterbodies was 26,468 acres. But today the area lost in the tank beds is 2,500 acres, according to a preliminary survey by the Survey and Settlement and the Revenue Department. According to a report in The Times of India (5 July 2009), there were 264 lakes in 1970; now they are 84. In January 2000, the Bangalore Development Authority breached a 32-acre lake, Arakere Tank bund, to make a road. The Chikkamaranahalli tank, Malady tank, Miller tank all dried out. After the tanks dried out, their land was used for different constructions and other purposes.

Disappearing Lakes

The lake may be infilled with deposited sediment and gradually become a wetland such as a swamp or marsh. Large Water plants, typically Water weeds, accelerate this closing process significantly because they partially decompose to form peat soils that fill the shallows. Conversely, peat soils in a marsh can naturally burn and reverse this process to recreate a shallow lake resulting in a dynamic equilibrium between marsh and lake. This is significant since wildfire has been largely suppressed in the developed world over the past century. This has artificially converted many shallow lakes into emergent marshes. Turbid lakes and lakes with many plant-eating fish tend to disappear more slowly. A "disappearing" lake (barely noticeable on a human timescale) typically has extensive plant mats at the Water's edge. These become a new habitat for other plants, like peat moss when conditions are right, and animals, many of which are very rare. Gradually the lake closes and young peat may form, forming a fen. In lowland river valleys where a river can meander, the presence of peat is explained by the infilling of historical oxbow lakes. In the very last stages of succession, trees can grow in, eventually turning the wetland into a forest.

Some lakes can disappear seasonally. These are called intermittent lakes, ephemeral lakes, or seasonal lakes and can be found in karstic terrain. Karst topography is a landscape formed from the dissolution of soluble rocks such as limestone, dolomite, and gypsum. It is characterized by underground drainage systems with sinkholes and caves. It has also been documented for weathering-resistant rocks, such as quartzite, given the right conditions. Subterranean drainage may limit surface Water with few to no rivers or lakes

A prime example of an intermittent lake is Lake Cerknica in Slovenia or Lag Prau Pulte in Graubünden. Other intermittent lakes are only the result of above-average precipitation in a closed, or endorheic basin, usually filling dry lake beds. This can occur in some of the driest places on earth, like Death Valley. This occurred in the spring of 2005, after unusually heavy rains. The lake did not last into the summer, and was quickly evaporated. A more commonly filled lake of this type is Sevier Lake of west-central Utah.

Sometimes a lake will disappear quickly. On 3 June 2005, in Nizhny Novgorod Oblast, Russia, a lake called Lake Beloye vanished in a matter of minutes. News sources reported that government officials theorized that this strange phenomenon may have been caused by a shift in the soil underneath the lake that allowed its Water to drain through channels leading to the Oka River.

The presence of ground permafrost is important to the persistence of some lakes. According to research published in the journal Science ("Disappearing Arctic Lakes", June 2005), thawing permafrost may explain the shrinking or disappearance of hundreds of large Arctic lakes across western Siberia. The idea here is that rising air and soil temperatures thaw permafrost, allowing the lakes to drain away into the ground.

Effects of disappearing lakes

Increased diversion for irrigated agriculture, the building of dams and reduced rainfall over the lake’s surface, are also named as contributing factors. These include a changing local climate – hitting agriculture, livelihoods and heath, increasing the salinity of the Water, destroying ecosystems and wetland habitats and increasing the chances of windblown ‘salt storms’.

According to the World Preservation Foundation one third of the world’s major rivers and lakes are drying up, and the groundWater wells for 3 billion people are being affected. The loss of rivers, lakes and underground Water reserves are impacting the livelihoods of millions of people, hitting animals, farming and electricity production, as well as threatening to exacerbate climate change further through the release of CO2 and methane. While climate change is playing a role, the building of dams, over extraction and mismanagement of Water and over-fishing are all playing a part in the disappearing of the world’s lakes and rivers.

The main cause for the drying up of the lake is believed to be drought caused by climate change impacting the inflow to the lake – resulting in a 65% reduction in Water levels. But that’s just a half knowledge. In reality, drought & floods are both two sides of the same coin. When the natural link between surface Waterbody and underground aquifer, via soil capillaries is compromised due to deposition of sludge, the after math in peak of summers is drought and the ripple effect of the same during monsoon is flood.

Life Cycle of Waterbody

Seeing the urban lakes, and doing an extensive study on the same, makes it clear that a Water body cannot disappear or die without the human intervention. A Water body has a complete ecology within, that keeps it alive, and the ecology is meant to go on and on.

The nature has planned a natural remediation of every Water body within itself, it’s cyclic and complete. Single-celled microbes do photosynthesis to release oxygen, these microbes are eaten by multi-celled planktons, which in turn are food for fishes, lobsters, shrimps and prawns, and their excreta is again ammonia, which is neutralized by single celled microbes. So the Water keeps renewing itself with this cycle and prohibits Eutrophication, Naturally.

But we humans, keep adding pollution to the Water. Starting from washing the dishes, to clothes, to animal bathing to human bathing everything happens on banks of the Water body. This pollution, gets to the bottom of the lake as sludge. The sludge does many harms to the Water body – namely, chocking of the soil capillaries, restricting the minerals cycles and the vertical movement of Water, reduction in DO (dissolved Oxygen) level by increase in the COD (chemical Oxygen demand), increasing the Water viscosity & making the color darker, and bringing up the Water level. Rising Water level and reduction of the depth of the Water body makes the Water vulnerable to vaporization, due to sun’s heat during the day.

Reduction of the DO level on the other hand starts the process of death of the Water body. It gives the right environment for the growth of disease causing anaerobic bacteria, which decomposes the contents of the Water body to release hydrogen sulphide (H₂S) that causes the bad smell. So if you find any smelly Water body, understand that the death process has started.

This gives the right environment for the blue green algae (BGA) to flourish and cover the Water surface, which reduces the amount of sunlight to reach inside Water. This is the second stage of the death of the Water body. And finally, Water weeds like hyacinth grow over the surface, confirming the death of the Water body. With Water weeds on the top layer, the whole aquatic ecosystem dies.

This rapidly increases the sludge deposition process further, as the self-sustaining ecosystem is no more, thus natural remediation doesn’t happen and all dead organic material deposits in the bottom of the Water body as sludge. Thus the depth reduces and Water evaporates. Eventually, it converts to a swamp marsh land and further drying gives the low land surface, which gets acquired immediately, as it is in the center of a developed urban society. Either people make houses or roads or railway track or any other urban settlement.

Thus if you look at it, a Waterbody starts to dry from the bottom, not from the top.

The key to keep the Waterbody perennial, mitigate the threat of flood and drought, recharge the aquifer and keep the underground Water table healthy, eradicate air pollution, gain carbon credits through the blue carbon sinks, solve the sewage puzzle and make drinking & irrigation Water available – all lie in just one focused and uncompromised approach of keeping the native ecology of the wetlands in a healthy and “Alive” condition.

Consumption of the sludge deposits is therefore key step towards restoration and rejuvenation of the aqua-ecology.

Sludge & Silt

It is very important at this point to understand the difference between silt & sludge because often people use them a replaceable terms, especially in Government tenders, wherein the specifically mention the term “de-siltation”.

Sludge – is the settled deposits in the bottom of the Waterbody, of the Suspended (TSS) & Dissolved Solids (TDS) in Water, that come in with sewage or effluent discharge. The key chemical contaminants of the Water, that settles down to chock the soil capillaries and disconnect the vertical link between the surface Waterbody and the underground aquifer, disabling the natural rain Water harvesting and aquifer recharge.

Silt – on the other hand is a result of a natural phenomenon of grinding of soil in to its nano-particles format. When the soil is beneath Water, movement of Water molecules (which is always spiral, due to the bipolar structure) grinds the soil and silt gets created. This silt is required to create the soil capillaries, which is the link between surface Water and the aquifer. Therefore, SILT is a natural sediment component of soil that is there in every Waterbody, naturally building the weathered top soil suiting the aquatic ecosystem and establishing a link with the aquifer

For dredging of the Waterbody for restoration of the lake ecology, sludge has to be eradicated, not the silt. And the eradication process has to be consumption, not physical removal.

So what we need is to DE-SLUDGE the Waterbody, and NOT De-silt it. But no chemical or earthmoving equipment can differentiate between the two. Removing the weathered top soil of the Waterbody de-links it from the aqua-ecology thus it isn’t restoration, but a re-start.

Thus the mechanical or chemical approach is WRONG. The RIGHT approach is ECOLOGICAL. In nature nothing goes waste, therefore even the sludge is to be consumed, NOT removed.

The stopgap remedy

The generic solution adopted by most of the conservation bodies is mechanical dredging. Now this has its own limitations, since we are trying to solve a biological problem, mechanically.

‒      It removes not just the organic sludge, but also digs the soil bed below. The soil surface below the Waterbody is cultured for ages to support the aquatic ecosystem, when it is mechanically removed, the soil surface below the top soil emerges as the new surface. Now this will take its own sweet time to get accustomed to the aquatic environment, that’ll elongate the time for the aqua ecosystem to stabilize.

‒      Secondly, this is a tedious process to the dredger inside the Water body.

‒      Thirdly, an expensive process.

‒      The sludge mechanically removed itself becomes a problem. How and where to dispose it? Largely is used in the landfills that means there’s a big transportation cost as well.

‒      Moreover, mechanical dredging disrupts the aqua-ecosystem, instead of helping it.

‒      It is an energy intensive process that uses a lot of hydrocarbon / fossil fuel, therefore creates air pollution and is non eco-friendly.

The Vaidic Science Approach

Ecological solution called “EcoDredging” is the MOST sustainable solution in this regard, which is an effect of “Resurrection of the native ecology of the Wetland”.

We conduct a careful study of the Waterbody for all the problems taking all aspects in to consideration like agroclimatic zone, amount of pollution coming in on regular basis, type of contamination, Water quality parameters, Waterbody features like surface area, depth, dimensions, vegetation on embankment and so on. Then the medicine is made, diluted in the fresh Water from the same agro-climatic zone and poured in the Waterbody.

This medicine gets synthesized in Water in presence of Sunlight and the resurrection of the aqua-ecology starts happening. The changes happen rapidly in the physical, chemical and biological layers through the natural process. Photosynthesis starts happening naturally and the oxygen generated within the Water is pure & natural. Moreover it is released from the bottom, thus gets dissolved completely there by increasing the DO levels multiple times. This creates the right environment for Aerobic bacteria to dwell and therefore the aerobic digestion starts to happen, eradicating the foul smell in the vicinity of the Waterbody. In the aerobic environment, the anaerobic organisms can’t survive and this keeps the Water safe from disease causing pathogens resulting into natural disinfection of the Waterbody.

Bottom line is – we enable sustainable resolution of Waterbody contamination through EcoDredging.