Why do some Rain Water Harvesting systems fail?

When water is not absorbed by a Rain Water Harvesting (RWH) system and it stagnates around the structures or if the structure itself collapses, we consider it as a failure of the RWH system.

There are innumerable designs and ideas floated on the internet for Rain Water Harvesting. We evaluated several designs and have found that many of these have inherent shortcomings which can cause RWH systems to fail. We observed that these designs have not been properly tested in real-world scenarios over a period of several monsoons or their designers simply do not report failures.

Through our decades of experience designing & developing Rain Water Harvesting solutions, we recognize the multitude of factors which can lead to failures of Rain Water Harvesting structures.

The idea of this post is not to comment on the design of any individual person or entity but to select a few basic reasons which can defeat the entire RWH effort.

To illustrate these scenarios, we have randomly picked up two designs for Rain Water Harvesting structures commonly circulated on the internet, which in our experience are not successful in practical applications.

a. RWH systems using hollow cement rings with slots

This design proposes using hollow cement rings with holes to construct a Rain Water Harvesting bore up to a depth of 10 feet to 30 feet, with a diameter of about 3 feet approximately. The hollow cavity of the bore stacks cement rings of diameter 2.5 to 3 feet over each other from the base till the top. The top is covered with a slab as you see in the pictures below

Hollow cement rings with slots
Hollow cement rings with slots

Expectation:  The designers of such a system imagine that the rain water will fill the hollow space in the pit and the water will pass through the slots in the cement rings and when it comes in contact with the soil surrounding the cement rings, the water will be absorbed by the soil.

Reality:  In practice, while the rain water fills the empty space in the pitit thereafter moves out of the holes in the cement rings and forms a watercolumn outside the rings. Now as the soil which has come in contact with thewater dissolves in this water column, this mixture of mud and clay re-entersthe hollow space and tries to fill the hollow space with soil.

This processcontinues as and when the remaining empty space is filled with water. Thisprocess stops once the empty space in the rings is completely filled andcompacted by the adjoining soil.

Collapsed Hollow Cement Ring Based RWH Structure
Collapsed Hollow Cement Ring Based RWH Structure

At this stage,any chance of ground water recharge stops due to compaction of soil. The soilwhich has moved in through the holes in cement rings leaves a hollow space adjoiningthe structure causing it to eventually collapse around the structure as isvisible in the photo above.

This fundamentally flawed design increasesthe risk of soil shifting and structural damage to nearby constructions.

b. RWH Systems using percolation Bore-Pits

This design proposes creation of percolation bore-pits for of rain water absorption through creation of 15 to 30 feet deep bores where the top end is enclosed in a 2 x 3 feet deep bore-pit covered with a perforated RCC slab as shown in the image below.

Percolation Bore Pit Design
Standard Percolation Bore-Pit Design

Expectation: The designers here imagine that the flowingrain water over paved surfaces (such as streets or parking lots) will effortlesslyfall into the chamber through the perforated RCC cover slab and thereaftersettle around the bore-pit to eventually be absorbed by the bore.

Reality: Having observed a practical implementation of this design on one of our sites, we recognized that when water flows over a perforated slab it forms a film of water and thereafter most of the water flows and passes over. Some rain water laden with silt and clay enters the perforation and deposits in the pores in the shape of a cone further reducing the opening size of the hole on the inside of the slab and finally the hole gets completely blocked.

Clogged Percolation Covers With Silt
Perforated cover slab choked by silt

Further, below the cover in the bore-pit in the silt-removal chamber:

Expectation: It is imaginedthat the flowing rain water that reaches the silt removing chamber will gentlyfall on the coarse sand and all the silt and clay suspended in the rain waterwill be restricted by the coarse sand from moving further down. After this onlyclean water will pass through the pebbles and enter the recharge pit pushingthe air out through the air vent and letting the soil absorb the water.

Reality: During rainfallthere is massive turbulence in water leading to the water appearing muddy andalso there is no time for decantation – silt mixed with clay and small pebbles flowswith rain water and fill the chamber to the brim as intake speed of anyrecharge structure is relatively slow.

The turbulence in the chamber also disturbs and suspend the coarse sand inthe water. This water with suspended silt, clay, coarse sand and small pebbles formsa paste which tries to find a passage into the air vent chokes the air ventpipeshown below the perforated cover within the chamber.

Once the air-vent pipe gets choked, the recharge process completely stopssince choking of the air vent pipe is like somebody closing a pipette with athumb to stop the water column from falling down.

Other factors like the shallow depth of pit, chances of choking of recharge bore pit by infiltrating coarse sand mixed with silt and clay entering with rain water into the bore hole as well through the pebbles, the unmentioned size of pebbles and unclear relevance of the diameter of the pit are likely to jeopardize the performance of this structure design.

The success of SILVERON rain water harvesting designs is a result of decades of untiring experimentation and experience in field work across diverse topographies.

At SILVERON, Learning & Innovation are the heart of what we do.

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Using roads as catchment for ground water recharge

Every monsoon we see familiar scenes of flooding in our towns and cities overwhelming our urban infrastructure, inundating our roads and highways with huge quantities of water for days. On the other hand, for remaining months of the year our cities have to fight a never-ending battle against water scarcity and depleting water tables.

This imbalance is a man-made crisis caused by concretization of surfaces, filling up of ponds and lakes for urban land-use, increasing density of building infrastructure and reduction of green spaces around our cities.

How can we address this imbalance?

A good starting point is to re-phrase the problem of flooding in our cities. Rather than consider it only as a storm-water drainage issue we should consider using our roads and highways as water catchment areas for ground water recharge.

The massiveness of the roads & highway infrastructure as rain water catchment area would be astonishing once we take into account the length and breadth of this catchment. While water scarcity is looming large in most parts of India we have comfortably preferred to ignore the hundreds of thousands of square kilometers of ready in-hand catchment.

Using our urban infrastructure to also help recharge our ground water reserves is a sustainable approach with many benefits however, it requires careful study to be designed and implemented correctly.

Some people are of the opinion that rain water falling on the roads should not be recharged since there are contaminants like rubber remnants from friction of tires and oil spillage on roads due to vehicular traffic.

Surface contaminants from vehicular traffic
Surface contaminants from vehicular traffic

Some engineers avoid rain water harvesting beside the road due to fear of road collapse due to shifting of soil.

A road cave-in during the monsoons
A road cave-in during the monsoons

Some people wonder if it is even possible to hold back, guide and recharge the rain water falling on roads and highways.

Typical water-logging during monsoon rains

To begin with, we at SILVERON firmly believe that every drop of rain water must be prevented from running off long distances on the road, must be prevented from evaporation and must be recharged into the ground close to where it falls.

There are surely some contaminants on the roads but most of them are not water soluble and also during the rains the dilution levels are extremely high hence we should not lose out on this opportunity.

Recharge of rain water along these highways also support the idea of recharging rain water where ever it falls thus benefiting the entire area at large.

It must be underscored that recharging rain water close to a road is a highly specialized work since there is a risk of shifting of soil from under the road into the rain water harvesting structure leading to development of hollow space below the road which may not be visible at the first instance but may cause caving over time creating risk for commuters.

We at SILVERON have years of experience in building rain water harvesting and ground water recharge structures that are designed to perform alongside roads. Through are experience, we have following suggestions to offer:

  • Highways should have a proper slope on both sides from the center for water to immediately flow towards the edge of the road. This will not only prevent the road from damage but will put the water into shallow storm water drain running along road’s edges.
  • Storm water drain should have baffle walls a regular intervals. and these drains may not be covered and instead filled with 40 mm gravel to prevent any paper trash, poly bag, cloth etc. from chocking the drain while allowing the water to easily enter it.
  • A SILVERON design recharge shaft should be constructed on the outside of the drain preferably between two baffle walls and connected to the drain .
  • The recharge shaft design has to be modified such that the water from the drain is released into the recharge shaft bore sufficiently below the ground level so that it can percolate deeper into the ground. This will not disturb the compaction of the road.
  • Restaurants, shops or petrol pumps abutting the highways should ensure that they put slabs to protect these drains from getting clogged with sand or trash.

SILVERON designed catchment systems collect rain water run off from the road into the storm water drains. The gravel in these drains filters the water and prevents trash like polythene bags, paper etc from chocking the drain. Rain water percolates into the drain and moves through the connecting pipes to be recharged by the recharge shaft.

When conserving rain water, we just need to have the will that creates the way.

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Water Conservation : The Journey Continues

As more people join in, this journey is destined to become a movement one day

Water is the precious elixir for all life on our planet. It is the most dynamic force of nature that has the power to shape our geography, nurture our civilizations and sustain all human activity.

My name is Sunil Sharma and understanding water resources has been my life’s passion. As a child, I remember playing with water – drawing small canals in the sand. I was fascinated to see water flow through my creations as I poured a small pitcher of water into these canals and made it drain into a small pit at the end. As a kid, sitting next to the pit seeing the water get absorbed and leaving the pit empty seemed like magic to me.

For the last three decades, each year I spend a part of the profits generated from my other business ventures into experimenting on the soil and water relationship in order to understand, develop and implement new systems for artificial ground water recharge.

In 2001, I founded SILVERON – an organization dedicated to designing and developing rainwater harvesting solutions. I have been sharing my work and experiences with people through lectures, seminars and discussions at various forums including this blog.

Water Crisis

Over the past few decades, I have seen the emergence of a water crisis – an environmental catastrophe where the lack of clean water is putting an immense economic and social burden on our rapidly urbanizing communities.

As humans, we have a tendency to put our self-interest above everything else and take actions only for our direct benefit, be it social or economic. As a society we have become unconcerned, insensitive, casual, unimaginative and even unintelligent while soon approaching a day with ‘zero’ water.

Individuals and corporations cause immense harm to the environment when they are driven by only their financial motives. From illegal tubewells that siphon off precious groundwater through the water-tanker mafia, industries dumping toxic chemical waste into our rivers and water bodies, illegal logging and mining that destroy our forests and watersheds – the threats to our environment are far too many.

Need for Change

The water crisis is a ticking time bomb that threatens our society’s existence. The need of the hour is to create a movement where we take up the cause of water conservation en masse. However, this movement like other environmental struggles requires the involvement and participation of large sections of our society.

Part of the reason why water conservation is not high on our agenda is due to the government short-term approach of treating water as simply a utility service that it needs to provide. With this approach, the government undertakes costly infrastructure projects to fetch and haul water to population centers from reservoirs far and away whilst simultaneously overlooking people’s encroachment and over utilization of water resources available to them through illegal or overused tubewells, inefficient irrigation systems etc.

To address this impending mega water crisis, the government must revisit its strategy and appropriately incentivize water conservation efforts. It is time that the government realizes that appropriate direct financial benefits like proportionate relief in state or local taxes, discounts in utility bills and/or direct financial rewards are the only means that will motivate people to adopt water conservation and rain water harvesting efforts on a large scale.

For example, people install solar panels on top of their houses not just because they provide clean energy but because the energy thus generated is “free” and has financial value when sold back into the grid. Likewise, people also invest in windmills to earn money from selling the power generated.

While the deteriorating state of our water bodies and a rapidly declining water table are putting our society on suicidal path, as individuals people often ask a simple common question – “Why should I spend money in construction of a Rain Water Harvesting structure when the rain water recharged into the ground by me does not remain in my premises and not benefit my bore well exclusively”?

This says it all but this is not the end of it.

Conservation In Action

It is SILVERON‘s commitment to keep working towards designing and developing solutions for ground water recharge by the cheapest available alternatives at places where the rain water collects.

Ground Water Recharge Through Abandoned Tubewel

As an example of this, on April 26th 2019, in far off villages in the arid state of Gujarat we are attempting to develop scores of abandoned tubewells as ground water recharge structures. These tubewells were built in 1977 at different villages to extract ground water and have been abandoned thereafter as the water table in the region declined.

Rain Water Harvesting is a site specific work and the most appropriate site specific design needs to be developed in view of the available opportunities. There are millions of abandoned dry tubewells and open wells in the country. What if we are able to recharge ground water aquifers through each one of them!

This video demonstrate that we need to be positive and optimist to succeed. We can surely turn the table if more and more people join hands and work. There is always light at the end of the tunnel and together we can march forward singing the famous lines – “we shall overcome

We shall continue this journey, as more people join in it surely will become a movement one day…

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The Flood Drought Fire Cycle

A vicious cycle that must be stopped.

Global warming and changing climate is having a major impact as many parts of the world face prolonged droughts or uncontrollable wild fires or damaging floods along both coastal and inland regions. It is a vicious cycle affecting the natural system and unfortunately the area of impact keeps increasing at an alarming pace.

Flooding is a result of excessive flow or accumulation of water in a particular area due to rain or other reasons. Flooding creates an ecological imbalance by adversely affecting the soil & plant relationship, since all plants require air especially oxygen to a greater or lesser depth in the soil for growth.

The waterlogged soil resulting from flooding is nearly saturated with water such that the aeration is restricted and anaerobic conditions prevail. With this depletion of oxygen in the root zone, the micro organisms which support plant growth are affected adversely and in turn the plant growth is restricted.

Water-logging also reduces the temperature of the soil and increases dampness which disturbs the biological activity in the soil. Water logging restricts all operations related to soil enrichment and soil development. In irrigated agricultural land, water logging is often accompanied by soil salinity as waterlogged soils prevent leaching of the salts imported by the irrigation water and the adverse effects are accelerated by the salts brought from lower parts of soil by the capillary water.

This increase in salinity not only interferes with the absorption of nutrients by the plant roots, thereby damaging the plantation but also spoils the physical state of the soil by making it less permeable for water and more suited for runoff which in turn hurts the adjoining land and vegetation.

Even fodder grown in such soil may cause diseases in livestock.  In our observations and experience over 30 years, we have seen that flooding has a prolonged negative impact on the soil. This may not be apparently visible in the initial years but in the long run flooding has a tendency to degrade the soil quality by consequently reducing the water absorption capacity of the soil.

Drought is a result of little or no supply of water in a particular area due to poor rainfall or other reasons. A drought removes water from the root zone in the soil and in prevailing natural drought conditions or man-made conditions requiring extraction of large quantity of ground water causes a sustained lowering of the water table and takes away the soil moisture farther away from the roots.

A drought leads to wide spread drying of the entire forests or grasslands, turning once lush-green forest covers teeming with wildlife into desolate wastelands. This makes huge quantities of dry wood fodder available for fire and we have seen massive forest fires raging for months together.

Fire requires favorable conditions like open air and availability of fuel. Wildfires often start from a lighting strike or can be caused (accidentally or deliberately) through human activity. Once a wildfire picks up enough momentum, thousands of acres of land can be engulfed in its path. Wildfires cause massive ecological damage to the flora and fauna, livestock and humans inhabiting the region.

Once the thick forest cover at the base of a hill is consumed by a wildfire and barren land is visible – all natural barriers creating hindrance to the downward flow of wind or water from the hill disappear. Now free flowing wind & water take the rich top-soil along with it and this water can flood downstream areas. This has a dual effect – with every removal of top soil, the revival of plantation becomes more and more difficult and the chances of the forest going back to its old form are reduced drastically. The water flooding downstream area has its own negatives as discussed above.

We at SILVERON have developed a unique rain water harvesting design which has the potential to obstruct this vicious cycle and to even break it if our design is implemented at a large scale.

What is special about SILVERON design?

  1. The SILVERON recharge shaft does not require flooding of ground with water. In fact where ever there is flooding , our design provides passage for that water to get into   the soil.
  2. The SILVERON recharge shaft does not dictate the recharge location or depth to the percolating water. The water can be absorbed by every favorable soil formation throughout the depth of the recharge shaft, starting from the root zone itself. This naturally supports plantation and vegetation in the area around the recharge shaft. 
  3. The SILVERON recharge shaft provides easy passage for rain water to filter through and percolate down wards while simultaneously also being absorbed through the walls of the shaft.

Because of the uniqueness of the SILVERON recharge shaft design, the rain water which falls on the ground at a distance from the shaft, while naturally struggling to percolate in the soil can detect the soil made soft and wet by the water absorbed from the shaft and form underground capillaries to reach the recharge shaft and supply its water to the recharge shaft, even when it is not observable from the surface.

Impact of SILVERON recharge shaft on the ground:

A very apparent impact of the shaft design is visible at Hero MotoCorp plant at Gurgaon, Haryana where the soil surface of the front lawn used to frequently waterlogged with rains and caused flooding in the garden. This resulted in the grass becoming black and unhealthy.

The field shafts constructed by SILVERON diverted all the collected water into the ground thus preventing flooding. This design also enriched the root zone with water which supported plantation and resulted in the development of the beautiful healthy green lawns as is evident in the photographs.

The dry grass and trees are fire hazards - the green grass and trees are the savior.
Dry grass and trees are fire hazards – the green grass and trees are the savior. (Source: Friday Gurgaon)

Thus, the unique potential of the SILVERON rain water harvesting system allows for enriching the ground water aquifers and provides a strategy to obstruct and break the vicious cycle of Flood-Drought-Fire-Flood by implementation on a large scale.   


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Tanka System – A Basic Rainwater Harvesting Technique

Rainfall is the main source of water for augmenting ground water levels, soil moisture and surface water. Water is essential for agricultural activity, for growing fodder to feed livestock and to fulfill domestic requirement of all humans.

Rainwater harvesting has been a natural tendency in all ancient Indian and other civilizations in different parts of the world and has been practiced for more than 4000
years because even in those times the people recognized the fact that without water no form of life is possible on earth.

The Indus Valley Civilization settled on the banks of the Indus River and other parts of western and northern India about 4500 years ago had one of the most sophisticated
water supply and sewage systems in the world

The people of the Thar Desert in Rajasthan designed, developed and constructed many different structures for Rain Water Harvesting and among them; the most Common Rainwater collection technique has been through the ‘Tanka’ system

Tanka is a paved underground tank of differing shapes from square, rectangular to usually cylindrical, having holding capacity ranging from 1000 liters to 1,000,000 liters

The traditional construction material also varies from simple mud plaster to lime mortar or cement mortar. On top of the tank there is a roof cover with mild slope towards the center where there are inlet points to let the rain water falling on this catchment surface flows into the Tank (Tanka). There is also a covered opening from where the water is drawn using a rope and bucket as and when water is required.

Apart from the roof surface of Tanka which acts as catchment for rain water, even rainwater from house rooftop, courtyard or artificially prepared catchments flows are diverted towards the Tanka

The water collected in a Tanka is highly valued commodity for every member of the family and is used carefully so as to ensure that it lasts for many months – sometimes even till the subsequent monsoon…

A Tanka and the water it brings to households in an arid zone provides water security and saves family members (specially the rural womenfolk) from the burden of traveling long distances to get water for every day requirements.

SILVERON, in the year 2003-04 built two Tankas funded by Coca Cola India at Kaladera village and these were inaugurated by Hon’ble Justice B.N. Kirpal, former
Chief Justice of India.

Rainwater Harvesting Tanka constructed by Silveron at Girl’s School (Storage Capacity of 100,000 liters water).
Rainwater Harvesting Tanka constructed by Silveron at Girl’s School
(Storage Capacity of 100,000 liters water).

SILVERON did not build small prototype models but instead constructed big practical structures which are still operational. The rain water falling on the roof of the school/college building also finds its way into the tanks.

Apart from collecting rain water in the Tanka – Team Silveron also made provision of taking the over flow of the water from the Tanka (in the event of heavy rainfall) by a PVC pipe to a Ground Water Recharge Shaft near the school hand pump.

These two Tankas were built in educational institutions so that the students could see and understand all aspects of rain water harvesting from roof top catchment – channelizing the runoff – storage on surface – recharge into the ground.

Such old time water harvesting systems can still be seen along Naneghat in the Western Ghats. Every fort in the area had its own rain water harvesting and storage system that are still in use today. Forts like Raigad in Maharashtra and Jaigarh at Jaipur near Amber have tanks built in their courtyards that collected and provided water.

Seeing the Tanka from the Thar Desert of Rajasthan, India to the Tanka at El Morro Fort, old San Juan, Puerto Rico we must salute the spirit of our ancestors and attribute the Tanka as a rainwater harvesting technique ingenious to the men who desired to survive in the toughest conditions.

The rainwater storage system in the Castillo San Felipe del Morro Fort explained
The rainwater storage system in the Castillo San Felipe del Morro Fort explained

Rainwater can be a reliable source of water if collected from runoff areas such as roofs
and other surfaces and stored appropriately. If the catchment area is big, this system can provide huge quantity of good quality fresh potable water.

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