Rain Water Harvesting : The need for a macro vision

We at SILVERON have been getting regular emails from people who have received notices from government departments because their properties lack proper Rain Water Harvesting (RWH) systems.

Since awareness & outreachabout water conservation is an important mission for SILVERON, we often guide people,free of cost and to the best of our capabilities, on ways in which they couldimplement simple and affordable RWH systems.

One such email that we receivedlately was from a retired person from Bhilai who on a subsequent telephonicconversation narrated a distressing tale of bureaucratic harassment that is notuncommon.

This gentleman has a small residential house and usual financial constraints of a pensioner. He has been struck with a financial penalty for not constructing a RWH system in his plot and has been threatened that this penalty amount will be increased each year if he does not construct a rainwater harvesting system.

The recommended contractor gavean estimate of Rs. 70,000. He doesn’t have that kind of money to spare and hasno knowledge about how to do RWH on his property.

Urban rain water harvesting
Rain Water Harvesting is for the public good

This is the sad reality where the whole burden of doing rainwater harvesting, water conservation and ground water recharge has fallen upon individual citizens with meager resources and no expertise in the field.

There is no doubt that the water crisiswith rapidly declining groundwater levels is a serious issue of our times. However,our government agencies and civic bodies either ignore this problem completelyor shrug it off on to individual citizens.

Consider a scenario where inresponse to an enemy attack on a country, the government instead of deploying trainedarmed forces, calls upon only untrained civilians to buy weapons with their savings,move to the battlefield and fight the enemy. The outcome will be complete chaosand defeat.

Consider for a moment, if anation’s economy faces recession & unemployment and the government insteadof taking appropriate fiscal and policy measures simply orders ordinary citizensto become entrepreneurs and provide employment to others while putting fines onthose who cannot take such risks. The outcome will be an irreparably broken nationaleconomy.

Like the above scenarios, when itcomes to environmental issues and the climate crisis our governments cannotsimply ignore their responsibility and pass the buck onto ordinary citizens. Itis also the government’s responsibility to protect our natural resources,provide clean air and water to the citizens.

Starting with the Ministry of Water Resources, central & state ground water authorities, local   municipalities and public health departments – all have the authority and resources to fulfill their prime responsibility of providing adequate quantity of high-quality water to every citizen.

The ground water table has notreached these precarious levels over night. It has declined every year. Regionafter region has gradually slipped from safe to critical to being marked as notified.

Authorities have looked the otherway when rampant over exploitation of water resources has been continued unabated.Even when this problem has reached crisis proportions, these agencies have beenunable to formulate an effective plan or put adequate rainwater harvesting infrastructurein place in order to arrest the decline of water table for decades.

However now the system suddenly wakesup and decides to make ordinary citizens, such as the gentlemen from Bhilai, dowhat the government machinery should have done for a long time.

Every expert in the realm of water conservation knows that rainwater harvesting is a site-specific effort and to do successful rainwater harvesting one needs various site-specific data-points such as the geophysical report, knowledge of topography, existing water table levels etc.

Hence, without providing anyrequired inputs, structural designs or financial support and simply pressurizinguntrained citizens to construct RWH structures on their properties is ameaningless & unscientific exercise.

Without hesitation one can compare this approach with the complete failure & ineffectiveness of the Chennai-model where people were forced construct rainwater harvesting structures that have had no positive impact of the groundwater table as the city remains critically water deficient during the dry season.

We have been trying to explain that rainwater harvesting is not simple and sooner than later water stands un-absorbed in most structures if these are built unscientifically. It is the job of experienced experts who know the science.

Ordinary tax paying citizens should be spared from the pressure of constructing rainwater harvesting infrastructure without any assessment, guidance, support and information from the concerned government agencies.

Their efforts may be pointless without large scale, scientifically built public infrastructure for doing Rain Water Harvesting. We need a macro vision.

Ensuring Water Supply for Future Generations

We often encounter experts with deep knowledge and foresight in various fields who in very few words are able to provide easy solutions to seemingly incurable problems for generations.

One such chance encounter was a lecture of a world renowned orthopedic surgeon who said – teach your children to stand, sit and walk tall and they will never encounter posture related problem in life. This straightforward advice if adopted can have lasting improvements for one’s quality of life and of our future generations.

Likewise, we need some plain-talk when it comes to solving the problem of water scarcity. We are deep in water-debt, we continue to live far beyond our means when it comes to sustainable water use. We have been borrowing blindly for our future generations and the problem has acquired frightening dimensions.

Save Water, Save our Future.

There are two distinct problems which call for immediate action as far as ground water is concerned. Firstly, the available quantity of ground water has already been drastically reduced by over exploitation and secondly, we are failing to protect remaining pockets of fresh water resources from contamination.

This inconsiderate exploitation to water resources by individuals, industries and even government agencies makes us continue to extract ground water without even thinking about replenishing the precious commodity back to the aquifer.

Further our land, surface water bodies & rivers are being used to dump dyes, chemicals, industrial waste, colors, paints, metals, plastic etc., overlooking the fact that this is the same land from where we expect ONLY rain water to percolate and reach the ground water aquifer so that we can draw water to drink.

We must remember that sooner or later we shall be drinking contaminated water since the undesired waste we try to bury in the ground will also percolate and reach our aquifer on its own or mixed with rain water.

Consider the pitiful state of ponds and lakes in any urban center in India where we have over-polluted, contaminated or simply paved over natural water resources. In once lake-rich regions in a modern city like Bangalore or the banks of the holy Ganga in Varanasi one finds at regular intervals there are pipes, drains & nallahs of all possible sizes bringing and dumping the effluent and waste into our water bodies.

We cannot shrug off our responsibility towards ensuring sustainability of water resources for our future generation any longer. After all, it is from our children that we have taken these resources – the clean air and fresh water – as debt.

Campaigns on climate-change awareness, water conservation and ecological sustainability cannot be issues relegated as the responsibility of our school children. We must act decisively and put concrete steps in place at the individual, local and regional level to preserve the most important natural resource – Water.

Let us not forget, rain water falling as droplets or frozen snowflakes is the only source of all available fresh water on earth – be it as ice on mountains and glaciers or on the surface in rivers or lakes and beneath the surface as ground water.

The water we extract from the ground follows a simple principle of demand & supply. Over centuries, the excess rain water accumulated on the mountains and glaciers as ice cap and percolated in the ground to create ground water reserves because our water demand was far less than supply. With rapidly increasing population and water requirement, the ground water extraction has increased manifold and reached levels where the extraction quantity far exceeds the amount of water naturally replenished in the aquifers, leading to regular decline in ground water table.

Human activity is causing ecological imbalance and global warming leading to rapid melting of glaciers and enhancing the already existing problem of fresh water scarcity on earth.

The government can ensure and manage to keep our city clean but only we can ensure cleanliness inside our home. Public agencies like Pollution Control Boards, National Green Tribunal, Central Ground Water Authority etc. can make regulations to protect water and environment but it is actually for every individual & industry to ensure the success of these regulations. Water is our collective asset and we are all stakeholders in its successful conservation.

We need to identify and check actions that may contaminate or waste ground water in the same spirit with which we protect our loved ones. We must start to identify the runoff route of rain water or the area in our building premises or vicinity where rain water naturally collects and thereafter prevent the water from running off.

Collecting and recharging ground water through an appropriate structure designed and installed by experts is the only way to preserve this vital resource for our future.

Massive rain water harvesting efforts need to be put in place to artificially recharge the ground water aquifers in order to increase the quantity of available ground water.

The next generation also deserves to have their share of water.

We, at SILVERON are proud to offer end-to-end solutions for rainwater harvesting and artificial ground water recharge techniques.

Geophysical Survey : An essential tool for Rain Water Harvesting

The main reason for a rapid decline in the water table can be attributed to our ever-increasing exploitation of ground water resources for meeting the growing water demands of agriculture, domestic and industrial purposes. Increasing urbanization and industrialization have also resulted in ground water pollution causing adverse effects on the health, environment and imbalance in the ecosystem.

The basic purpose of artificial recharge of groundwater is to replenish water into aquifers that have been depleted due to excessive ground water extraction.

Artificial groundwater replenishment systems involve techniques that modify the natural movement of surface water and utilize suitable civil construction techniques in order to address issues such as:

  • Enhancement of the sustainable yield in areas where over-development has depleted the underground aquifers. Storage and conservation of excess surface water for evolving future requirements
  • Improvement in the quality of existing ground water through dilution.
  • Avoiding flooding of roads during storm showers by capturing the rainfall run-off which would otherwise overwhelm sewer or storm drains.
  • Help reduce soil erosion and flood hazard.
  • Provide an eco-friendly method of water resource conservation.

In this post we discuss the importance of performing a Geophysical Survey of an area targeted for ground water recharge or extraction. We have presented sample data from our records showing variations in soil formation with changes in location and how a Geophysical Survey can help in planning & designing structures for groundwater extraction and artificial ground water recharge.

GEOPHYSICAL SURVEY 

In order to know the ground water condition , thickness of alluvium, depth to rock, the extent and depth of aquifer and quality of ground water, Geophysical Vertical Electrical Soundings are conducted in the specific areas. The results of these investigations and their interpretation forms the basis of identification of sites for construction of rain water harvesting structures.

Objectives of a Geophysical Survey:

  • Determine the depth and thickness of saturated aquifer zones.
  • Quantify the expected alluvium thickness and depth to rock at the sites.
  • Determine the variation of quality of water with depth.
A Geophysical Survey In Progress
A Geophysical Survey In Progress

Investigation Methodology

The Geoelectrical resistivity technique uses an artificial current source whereby a low frequency (4HZ) current is used. Controlled amount of current is introduced into the ground through current electrodes and measurements are carried out with the help of potential electrodes.

The current and potential electrodes are placed in various configurations, but the most extensively used electrode configuration for subsurface investigation is the Schlumberger Configuration. In this configuration the four electrodes are placed symmetrically along a straight line, the current electrodes are on the outside and the potential electrodes on the inside along the array.

With this configuration, to change the depth range of the measurements, the current electrodes are displaced outward. When the ratio of the distance between the current electrodes to that between the potential electrodes becomes too large i.e. more than 5 times, the potential electrodes must also be displaced outward, otherwise the potential difference becomes too small to be measured with sufficient accuracy.

In the Schlumberger Configuration, the apparent resistivity (Pa) is calculated by the formula.

Where, Pa is apparent resistivity.
L is half of the distance between current electrodes.
l is the half of the distance between potential electrodes.
π is constant,
∆v is potential difference and
I is amount of current.
K is a constant known as Geo-electric factor and based on the type of electrodes configuration.

Geophysical measurements are based on the assumption that the subsurface consist of a sequence of distinct layers of finite thickness, each of these layers is assumed to be electrically homogeneous and isotropic and the boundary planes between subsequent layers are assumed to be horizontal.

The resistivity data are interpreted using the Schlumberger Sounding Data Processing and Interpretation Programme.

For ascertaining ground water levels, the resistivity response depends primarily on the amount of impregnating water, the conductivity and quality of water and manner in which water is distributed. The first two factors have a nearly linear relation with the resistivity while the influence of the third factor is more complicated and depends on the nature of aquifer material.

In summary, it can be stated that a dry soil formations, whether porous or non porous are practically poor conductors and hence the resistivity will vary with amount of pores and quality of water. The chemical quality of ground water corresponds with aquifer resistivity.

 LIMITATIONS:

There are certain inherent limitations in estimating water withdrawal levels and lithology, which are being mentioned as under:-

1.  Scientific and human error possibilities tothe extent of 15% cannot be ruled out both in quantitative and qualitativeassessment of ground water.

 2.Increased ground water development activity in and around the area investigatedmay also effect rate of subsurface flow of water in the area in the years tocome.

Thus, any recommendations for construction of structures (Tube- well/ Dug cum bore well) for ground water development are based on indirect science of Geophysical investigations.

Presented below are data from 3 different sites to show different soil formations calling for appropriate modifications in rain water harvesting designs.

Artificial Ground Water Recharge: A Challenging Endeavor

Science is the pursuit of understanding the principles of Nature through a systematic study and observation of the processes, reactions and systems that constitute the physical and natural world.

Our enhanced understanding of natural principles and phenomenon has been instrumental in helping scientists and innovators bring about rapid scientific advancements and technological breakthroughs across many fields.

While our understanding of the geophysical and natural processes happening below the Earth’s surface has been steadily increasing in the past few decades, some crucial technological breakthroughs in Rain Water Harvesting have still not been achieved.

The process of Rain Water Harvesting involves critical interplay of numerous natural factors like the multiple unique properties of water, force of gravity, atmospheric pressure etc. along with various soluble and insoluble elements and compounds naturally present in the soil of the target location.

Due to the limited understanding of the natural processes taking place beneath the surface along with inadequate investigative tools developing artificial ground water recharge techniques still remains a challenging and complex exercise.

We have been emphasizing the fact that rain water harvesting is certainly not just about digging a hole in the ground and releasing water into it, as some people think it to be. The key to success of any rain water harvesting structure is the understanding and experience of the harvester. There is no margin for miscalculation that may disturb the critical natural balance and lead to stagnation of water on the surface or cause risk of damage to buildings and structures nearby.

We often see construction of impractical designs that are not in line with the principles of artificial ground water recharge. It should come as no surprise that the number of dead & defunct rain water harvesting structures far exceeds the number of the alive & operational systems, not just in India but the world over.

We are battling an almost constant water scarcity prevailing in most parts of India and people start coming under water stress within a couple of months after the monsoon. The time has come to address our water crisis at top priority.

We at SILVERON keep motivating people to value the rain and harvest the water before it runs off. Very often the rain water is even diverted into external storm water drains and sewerage lines without remorse. It is not in our hands to control rainfall but it is surely in our hand to prepare to receive, manage and harvest the rain water whenever it falls- wherever it falls – in whatever quantity it falls.

Drying lake bed. Native American Proverb.
We do not inherit the Earth from our ancestors, we borrow it from our children

While we had an excellent monsoon with above average rainfall in 2019, lot of urban areas lost the surplus water through runoff or floods. When it comes to the environment, we cannot gamble with the future of our next generation. Planning and implementation of rain water harvesting and water conservation requires a sustained effort which we must act upon on a priority basis.

At SILVERON, with decades of field experience in experimenting, designing and installing thousands of effective Rain Water Harvesting structures across India, we also recognize the multitude of factors that make artificial ground water recharge challenging.

Our attention to detail, understanding site-specific conditions and vast experience developing solutions across various topographies are just some of the reasons that make SILVERON the premier rain water harvesting solution provider in India and reflects in the flawless performance of SILVERON recharge structures.

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.