Understanding Earth & Soil

Experiencing nature gives us immense joy & pleasure. Be it in walking along a park trail lined by lush green trees, seeing vast green spaces or perhaps even seeing puddles and little streams after a rain shower. We love the sound of the humming birds, enjoy the weather and the fresh cool breeze. We love the sight of bright flowers all around and the squirrels crossing our path.

Does anyone spare a moment to think about the earth under their feet?

The world continues to move from the stone age to the space age because the principles of physics remain the same. It is only as we understand them better and experiment do we make advancements that benefit our lives.

We know more about the Sun, Moon and other planets in space but hardly know our Earth. Ever wondered how we can accurately predict solar and lunar eclipses but are caught off guard by disastrous flash floods, earth quakes, tsunamis and landslides?

The earth underneath us is so diverse and alive that the more one thinks about it, the more magical and mysterious it appears. It is the place where at each moment every law of physics is in action and which is holding within it the entire periodic table, innumerable organic and inorganic compounds and minerals and air and water and the living and the decomposing.

The core of the earth is about 6300 Km. from where we stand but humans have not been able to drill below 12 km (see ref). Most people do not even know that the ground well below our feet is may be hotter than the surface of the sun.

The layers of earth based on chemical variations from shallowest to deepest are:-

Layers of the Earth
  1. Crust: Earth’s crust is the outermost layer of earth and ranges from 5–70 kilometers in depth.
  2. Mantle: Mantle lies between Earth’s crust and dense super-heated inner core and is about 2,900 km. thick.
  3. Outer Core: Earth’s Outer Core is largely liquid iron layer of the earth that lies below the mantle. The outer core is about 2,300 km. thick.
  4. Inner Core: Earth’s inner core is the innermost geologic layer of the Earth. It is primarily a solid ball with a radius of about 1,220 km. The inner core is believed to be composed of an iron–nickel alloy with some other elements.

Our aim here is to give some insight to our readers that our earth is magical and that the earth’s resources are major components which impact the environmental factors which make planet earth habitable.

We do not wish to wade into a theoretical discussion about permeability or porosity of soil or about range of validity of Darcy’s law or velocity of flow of water. We would restrict our discussion to shallow depth of the earth’s crust since no man has ever explored the other layers in person – in fact at a maximum depth of 12kms, our civilization has barely scratched the surface.

The most common components with varying percent found in composition of the soil.

CapacitySandClaySilt
AerationGoodPoorMedium
Water-HoldingLowHighMedium
Compact-abilityLowHighMedium
DrainageHighSlowMedium
Leakage-preventionPoorGoodPoor
Result of tilling after rainfallGoodPoorMedium
Erosion by waterMediumLowHigh
Erosion by airMediumLowHigh
Capacity to hold plat nutrientsPoorHighMedium
Capacity to shrink or swellLowHighLow
Decomposition of organic matterFastSmallMedium
Soil components and capacity

Sand has pockets which hold air hence aeration is good and the voids are interconnected hence water holding capacity is low and drainage rate is high. This causes the compact-ability to be low and its use as a sealer to prevent leakage is not advisable.

This is the reason why it is beneficial to till the sandy land after rainfall. Planting of trees and bushes and construction of check dams are recommended to prevent soil erosion by air and water.

Some form of clay when added to sandy soil, enhances the cultivation output because it reduces soil erosion both by air and water and increases the compact-ability, water retention capacity & plant nutrient holding capacity of the soil.

If we explore the properties of soil we come across a list which is unending.

  • Soil not only serves as an anchor but also provides the required minerals and water to the plants. In fact this resource provides 99% of the food consumed by human beings.
  • Soil is a major raw material required for manufacture of many types of building materials. Soil is the foundation of construction projects.
  • Soil absorbs and cleans rainwater as it percolates through it and also holds it in the aquifers. This quality of soil not only serves as a source of ground water when needed but also protects us from floods and in time of droughts.

Interestingly, it has been observed that many animals deliberately ingest soil as it absorbs toxins, and facilitates digestion and checks diarrhea and it is also a source of rare minerals. The practice of eating soil is referred as Geophagy

Soil protection and conservation is very important since soil is the home for many organisms living in such interconnected harmonious diversity both inside and outside the soil like earthworms, snails, slugs, millipedes, centipedes, potworms, nematodes, bacteria, fungi and algae, to name a few. Aerobic processes of soil have a major role to play in waste management while handling effluent from septic tanks and elsewhere.

It is estimated that soil restoration will offset the effect of increases in greenhouse gas emissions and slow global warming. About 60% of the biotic content is carbon and this makes the Biological component of soil is very important. Even in desert crust, cyanobacteria which are microorganisms related to the bacteria but capable of photosynthesis, lichens and mosses capture and hold a good quantity of carbon by photosynthesis.

When we talk about water conservation, it is intricately tied to soil conservation as well. Preventing the erosion of soil through water conservation, rain water harvesting, green-belt development, responsible agricultural and industrial practices therefore has many inter-linked benefits – from improved soil quality to reducing the effects of global warming.

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.

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.

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…

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.