Rainwater Harvesting: The Key to Mitigating Flooding and Protecting Soil Health

In our previous blog, we delved into the swift cascading of water from upstream regions, unfortunately resulting in a rapid departure without replenishing groundwater aquifers.

Consequently, this water accumulates downstream, particularly in plains and farmlands, for an extended and undesirable duration. Besides the visible surface flow, there is an ongoing, invisible subsurface movement beneath the Earth’s surface.

When water falls on hills, it can infiltrate the ground, becoming subsurface water. Excess water accumulates in the subsurface if the soil is saturated or the terrain is poorly drained. It then flows downhill, potentially causing flooding through a process called emergence.

This type of flooding disrupts the delicate ecological balance in a given area, affecting the intricate relationship between soil and plants. Plants require a specific depth of aerated soil for optimal growth, with oxygen playing a vital role.

The Impact of Flooding on Soil

The aftermath of such flooding leads to waterlogged soil, nearing saturation and impeding aeration, creating anaerobic conditions. This depletion of oxygen in the root zone adversely impacts microorganisms crucial for supporting plant growth, restricting overall plant growth.

Water logging reduces soil temperature and increases dampness, disrupting biological activities within the soil. It also vastly affects operations related to soil enrichment and development, affecting irrigated agricultural lands.

Water logging often coincides with soil salinity, impeding the leaching of salts brought in by irrigation water. This exacerbates adverse effects, especially when salts from lower soil layers are transported upward by capillary action.

Rise in soil salinity disrupts nutrient absorption by plant roots, damaging plantations and altering the physical characteristics of the soil. The soil becomes less permeable to water and more prone to runoff, negatively impacting neighboring lands and vegetation. Even fodder grown in such soil may pose health risks to livestock.

Based on our three decades of experience, we have learned that flooding exerts a prolonged detrimental influence on soil. While immediate effects may not be readily apparent, long-term consequences involve a gradual degradation of soil quality, diminishing its water absorption capacity.

In reality, the water wreaks havoc both upstream and downstream, presenting a clear situation before us.

Case Study: Trial Bore in Flood-Prone Haryana

At SILVERON, we recognize the tangible and intangible losses incurred due to flooding in India, seeing it as an immeasurable national setback. We recognize the challenges of rapid infiltration posed by limited soil permeability or impermeable layers. We have proposed a strategic solution involving the implementation of drilling recharge shafts.

Our well-established design not only facilitates surface water infiltration but also intercepts subsurface flow, contributing to the replenishment of groundwater levels. The unlined bore design of our recharge shaft enhances its effectiveness in checking subsurface water.

Once water finds an easy path through the shaft, it establishes a regular route, attracting more water towards it. By enhancing the rate at which water permeates the ground, our solution holds the potential to significantly mitigate the impact of flooding.

We conducted a trial bore to test our shaft design in challenging flood management conditions, despite our confidence and experience.

As part of our social responsibility, we installed a Trial Recharge Shaft, at our own cost, in the flood-prone plains of Haryana. These plains experience annual inundation during monsoon as they sit below the mountains of Himachal Pradesh.

Our Endeavor

  1. We drilled the trial bore to appropriate depth to take advantage of soil strata having good absorption capacity and developed the recharge shaft following our standard basic design.
  • We deployed custom-designed Hume pipes, with a special 3 feet diameter and 8 feet length. These pipes featured holes of varying diameters (2, 4, and 6 inches) to facilitate water entry into the Recharge Shaft. Positioned at an 8 ft. length, 5 ft. of the pipe submerged into the ground, with 2-inch diameter holes positioned about 6 inches above the ground. Hole sizes are arranged in increasing order, considering the diminishing quantity of suspended silt as the water level rises.
  • A wire mesh barricade, standing at a height of 3 ft., was grouted around the Hume pipe, 3 feet away in all directions. We fill the space within the Hume pipe, between the pipe and the wire fencing with aggregate. This system prevents entry of suspended leaves, paper, polythene, and captures a portion of the suspended silt by reducing velocity. We then cover the top of the structure with wire mesh and aggregate.

These structures effectively mitigate the impact of running or collected rainwater, preventing serious damage to field soil or crops.

It’s noteworthy that each recharge shaft maintains a consistent intake speed, with observed likely intake flow around 200 cubic meters per day.

               Triumph is attainable solely through proactive endeavors.  

Ranthambore Tiger Reserve – An Ecological Climax

The Ranthambore National Park is situated at the confluence of Aravali and Vindhya mountain ranges i.e. the Great Boundary Fault in Northwestern India. It is a unique and highly bio-productive terrestrial ecosystem that enables all levels to optimally sustain life. In this ecological wonderland, The Royal Bengal Tiger  flourishes in its best form.

Tiger near water at Ranthambore National Park
A Royal Bengal Tiger spotted during a Silveron site visit at Ranthambore National Park.

The Ranthambore Tiger Reserve situated within the park is the western-most habitat of the majestic Tiger in the Indian subcontinent. The park is spread over 1700 km2 spanning Sawai Madhopur, Karauli, Tonk & Bundi districts of the Indian state of Rajasthan.

The park is bounded by the Chambal river in the west, which is one of the least polluted perennial rivers in the world. The seasonal rain-fed Banas river bisects the park. With the passage of geological time the Aravalis, one of the oldest mountain systems of the world, have weathered to yield more soils. On the other hand the comparatively younger Vindhyas have withered much less and support the growth of unique flora in the region.

This rich landscape is a major hub of biodiversity. It is home to viable populations of six species of predator cats (Tiger, Leopard, Desert Cat, Jungle Cat and Fishing Cat). Large populations of Jackal, Wolf, Hyena, wild dogs and marsh-crocodiles also rule over a food-chain with over 40 mammal species, including spotted deers & rare antelopes (such as Black-Buck, Chinkara and Blue bulls), 320 bird species, 40 species of reptiles and 402 species of plants.

Not so long ago, there existed many such forests along the foothills of Aravali and Vindhya mountain ranges. Unfortunately, owing to human population pressure and interference many such habitats have been lost.

It is worth noting that because of positive human intervention, the plateau of Ranthambore forest remains as the only big expanse of dry deciduous Anogeissus Pendula forest in India.

Large Anogeissus Pendula forest at Ranthambore

Modern conservation adopts the approach that natural forests should be left alone since it is a self-sustaining ecosystem. However, by artificially limiting the area for natural expansion and growth of forest cover, human activities continue to hamper nature reserves.

This can be observed by the ever increasing number of villages and settlements not just along the boundaries of forest reserves but also squeezing into forest areas for fodder and space.

In this era of nature conservancy, humans are still forcing increasing animal populations to get confined in smaller areas where they may become vulnerable and extinct due to natural infections, diseases and even greater competition for food and water.

Tiger Conservation at Ranthambore

Ranthambore is known for its large population of the endangered Royal Bengal Tiger. During the past few years, there has been a steady increase in the Tiger population in Ranthambore where the present tally is around 55. 

This has been possible due to the multi-fold, dedicated efforts of the forest administration, use of modern surveillance technologies across the reserve, and continuous manual monitoring including fortnightly stock taking of wild animals.  

The sincerity, commitment, passion and emotional attachment of the forest officials to this noble endeavor can be seen from top officials to the frontline forest guards posted round the clock at various check posts (Nakas) deep in the forest reserve.

The growing tiger density in Ranthambore forest has already paved the way for relocating some tigers to strengthen tiger populations in other reserves such as Sariska & Mukundra in Alwar & Kota districts of Rajasthan.

Ranthambore’s Climate, Topography and Water Crisis

The Park has a dry climate with three well defined seasons – summer, winter and monsoon. The hot & dry summer months last from March to June with maximum temperatures around 45℃, negligible relative humidity and hot dry winds. Winter generally lasts from late October till February with the temperature often ranging below 10 ℃ to 20℃. The monsoons with average annual rainfall of 800mm and about 35 rainy days per year, last from July to September.

The park landscape varies dramatically from the vertical slopes (cliffs & knolls) to the sharp and pointed hills as the geography changes from Vindhyas to Aravali ranges.

The park has an approximate elevation ranging between 300-500 meters above mean sea level with mostly rugged and hilly terrain. The Aravalis have ridges on one side and gentle slopes on the other with few small plateaus and valleys. Gazella Peak, the highest peak of the Vindhyas, has an elevation of 507 m. 

The top tableland, locally called Daang & valleys called Kho are prominent geo-features dotted with springs & geysers. These valleys are the richest wildlife areas of the reserve making them favorite spots for the tigers.

Most of the narrow, seasonal monsoon-fed water streams are very short lived. The streams flowing in the northern tract drain into the Banas river and ones on the southern tract drain directly into the Chambal river.

The deep, long and narrow gorges created due to erosion caused by these short-lived streams has created ravines that are prominent features valuable in enhancing the flora and fauna of the region.

Water scarcity for wildlife in long dry-spells and peak summer months is a cause of serious concern for forest officials. This is especially critical for territorial predators such as Tigers and animal groups that cannot migrate large distances in search of water.

Solving the Water Crisis with SILVERON 

On the official invitation of Sh. Arbind Kumar Jha, Asst. Conservator of Forests at the Ranthambore National Park, our CEO Sh. Sunil Sharma visited the Tiger Reserve on Oct. 24-25th, 2020. The purpose of this visit was to understand the landscape and explore possibilities for water conservation to combat scarcity of water for wildlife especially during peak summer months.

The early morning session gave a general feel of the forest and as luck would have it the day began with these lovely welcome sights. 

Royal Bengal Tiger spotted after a hunt
Royal Bengal Tigers dominating the Ranthambore landscape
A majestic Royal Bengal Tiger spotted up close

The afternoon was spent touring interiors of the deep forest to gather insights on the scale of water scarcity and possible remedies.

The forest area calls for proper water management to ensure enhanced quantity of available water. This includes hydro-geological studies, stage-wise implementation of solutions and evaluation extending over multiple monsoons. It is also important that only minimal intervention is made and that too only in support of the existing natural systems.   

At SILVERON we firmly believe that rainwater is an invaluable local resource and every effort must be made to manage, recharge and effectively use the water where it falls. Since fresh water becomes scarce, the logical approach would be to effectively control and utilize rainwater as far as possible before it is lost to runoff.  

Based on observations from the site visit, here are recommendations we are working on developing:

  1. Developing Bunds: The park is situated in a low-rainfall region with thin alluvium. The hilly terrain and steep to mild slopes facilitate rapid rainwater runoff. It is important to identify sites and make intermittent hurdles in the flow path using available stones and bush across small gullies and streams. 
Bund for water conservation
Bund constructed with locally-available rocks

The spacing between these bunds will be decided by soil permeability and angle of slope at each site. The bunds must be closer on steeper slopes where permeability is less. This will prevent flowing water from attaining erosive velocity thereby conserving soil moisture.

The accumulation of small quantities of water behind the bund also facilitates percolation wherever possible. This technique allows harnessing rainwater locally and reduces erosion through runoff. 

  1. Recharging through abandoned bore wells: The park has a number of bore wells that were abandoned due to non-availability of water. These boreholes can be re-developed into groundwater recharge structures. Small streams flowing nearby can be guided towards such boreholes. 

Rainwater percolating through these structures would find fractures at various depths and develop flow paths to enrich groundwater levels.

  1. Rejuvenating Shallow Dug Wells: A number of shallow dug wells are scattered throughout the forest. These wells get their water through percolation from rock fractures and water levels in them keep declining in the post monsoon months.

These dug wells, some even managing to retain water throughout the year, are an important lifeline for wildlife. Each such well should be numbered and monitored on a monthly basis to ensure effective use of waterstock.

Dilapidated shallow wells should be restored, de-silted and cleaned to increase their holding volumes and prevent collapse. Further, repaired dug wells should be covered using secure frames and strong wire mesh to prevent these wells from becoming safety hazards for thirsty animals.

New well locations can be identified on the downstream side to collect and preserve more rainwater before run-off.

  1. Rainwater Collection and Transportation: During monsoons, surface water is plentiful in small or large ponds and depression areas specially on the down stream side. This water can be effectively transported and used in times of need.

The forest does not have tall trees and the major fire risk is from dry grass on the ground. This threat is especially severe seasonally during the long dry-spells. 

Water tankers can be placed at designated Nakas to transport water to locations running short of water.  These tankers can be especially useful to extinguish bushfires or other emergency uses. 

Tanker for transporting water

This technique improves availability of emergency water supply and reduces stress on natural reservoirs especially during the dry season.

  1. Adopting solar water pumps: Replacing diesel pumps at wells with solar water pumps would also go a long way in reducing pollution, noise and wastage of water. With set levels, solar pumps can be programmed to extract only limited quantities of water each day. 

The extra generated power can be leveraged to deliver water via pipelines to other areas or to higher locations for storage or pumping.

In the first phase, SILVERON offers to provide Ranthambore National Park services of their experts, material and manpower at no-cost to design & demonstrate methods of recharging abandoned boreholes and rejuvenate & equip existing wells with solar pumps. 

This effort is a reflection of our commitment to conserving India’s natural biodiversity and the majestic Royal Bengal Tiger.

The SILVERON Recharge Shaft

The ever-increasing population, urbanization, industrialization and rise in agricultural activity are major reasons for growing water demand. Rapid decline in the water table can be attributed to over exploitation of ground water resources for meeting these demands.

The basic purpose of artificial recharge of groundwater is to replenish water into aquifers that have depleted due to excessive groundwater extraction. Artificial groundwater replenishment systems involve techniques that modify the natural movement of surface water and use civil construction methods to enhance the sustainable yield of groundwater in areas where over extraction has depleted underground aquifers.

SILVERON’s dedicated team led by Sunil Sharma started experimentation to determine the various factors affecting groundwater conditions such as thickness of alluvium, depth to rock, the extent and depth of aquifer and quality of ground water. The team conducted several Geophysical Vertical Electrical Soundings  in the targeted areas.                                          

In our earlier blog Geophysical Survey: An essential tool for Rainwater Harvesting, we discussed the importance of variations in soil formation and presented sample data from our records showing major variations in ground strata.

Explains Ground Resistivity Tests for Rainwater HArvesting
Clockwise from top left: (a) Soil-Layers cross-sec view (b) Team SILVERON performs Ground Resistivity Test (c) snapshot of Soil Resistivity Testing and (d) Imaginary Ground Profile Illustration

Geophysical measurements are based on the fact that subsurface consists of a sequence of distinct layers of finite thickness. Each layer is assumed to be electrically homogeneous and isotropic and the boundary planes between layers are assumed to be horizontal.

Lessons from Field Experiments

Based on the Geophysical Survey and analysis of soil samples obtained from various depths while drilling trial bores using a Rotary drilling machine, it was observed that the changing compositions of soil components are very diverse. The soil strata keeps changing as we drill deeper into the earth and we are likely to encounter some layers that absorb more water, some which absorb less and some which absorb no water.

Since it is impossible to modify this naturally occurring soil strata, hence the research team came to the conclusion that for rain harvesting, Diameter of the recharge bore has less meaning while its depth is more important.

Team SILVERON also studied existing rainwater harvesting designs and observed that most structures had worked well in the initial months but gradually their efficiency reduced, and water started stagnating in the structures. This happened as most existing structure designs were not in line with natural laws but rather attempted forcing water absorption against natural processes.

The conclusion drawn was that for rain harvesting, supporting natural process is a sure path to success while going against nature is a recipe for failure.  

In view of the above valuable lessons, Sunil Sharma and his team started experimenting with multiple design ideas to be able to develop an Eco-friendly shaft design which would recharge the ground water in a sustainable way closest to the natural recharge process.

The Vision

SILVERON’s dream was to create a Rainwater Harvesting System that recharges ground water aquifers and simultaneously enriches the root zone with moisture supporting trees, shrubs and foliage. The vegetation generated by this enriched root zone forms a network of roots, binding the soil together to check soil erosion and provide fodder for animals.

Increased moisture content in the top soil and vegetation raises the humidity in the air that in turn helps in the survival of diverse interdependent friendly organisms like bacteria and earthworm etc living both over and below the soil surface.                                   

The conceived design would allow water to flow down an unlined borehole in direct contact with soil starting from the root zone. This matches the natural process where the rainwater is not flowing through artificial ducts such as a failure-prone slotted pipe system .

An Ingenious Design

We had determined that the soil profile is not uniform and there are layers of varying composition, porosity & permeability. It is conceivable that in the natural process, rain water on the surface would runoff since it was the easiest path and droplets which percolated into the ground due to gravity encounter other obstacles in the flow that may delay movement and point of contact with groundwater.

Slow Natural Ground Water Recharge

To facilitate both vertical and horizontal flow of water across the varying permeability of soil strata, SILVERON shaft depth was planned in a way that pierces through all layers and provides easy passage for the flow of water. The shaft’s bore hole is filled with material of high permeability providing an automatic connection between all layers in the ground.

Natural Ground Water Recharge supported by Rainwater Harvesting Shaft

It was observed that the recharge shaft had its own absorption (or intake) speed and any excess quantity of water reaching it would tend to runoff on the ground surface.

Encouraged by the success of recharge due to the vertical inter-connectivity that the shaft provided through natural formations inside the ground, it was decided to interconnect the adjoining recharge shafts by PVC pipe at the top so that the excess water entering the shaft could reach an adjoining recharge shaft without evaporation losses. This would help in avoiding flood hazard during storm showers by capturing the rainfall run-off which would otherwise overwhelm sewer or storm drains and also results in soil erosion.

Shaft Inter-connectivity boosts Rainwater Harvesting
Shaft Inter-connectivity boosts Rainwater Harvesting

The team while examining choked recharge structures observed that most rain water harvesters focused entirely on silt removal before the water was allowed to enter the recharge structure.  SILVERON recognizes that silt is the finest particles of soil, suspension of silt in flowing rain water is natural and since the turbulence is high during monsoon season, silt does not get time to settle making the water appear murky. 

The challenge is not only to ensure unhindered recharge performance in condition of normal silt naturally flowing into the structure but also to incorporate design features that would make silt removal and cleaning an easy & cost effective process.

Natural performance of the SILVERON Recharge Shaft in a village pond

SILVERON designed recharge shafts such that the silt which enters the shaft in the previous monsoon is removed easily by back wash arrangement before onset of next monsoon, at almost negligible cost and as simple process.

Removing silt through backwash

SILVERON shaft was designed conceived that rain water transported from roof tops, paved surfaces or low-lying areas to the recharge shaft would percolate and make the soil wet all around the entire depth of the borehole.

This in turn would attract naturally percolating rainwater coming from any direction, any distance and at any depth – since the shaft column is available to provide easy downward flow passage. The main design principle was to let nature develop an inter-connected network of streams below ground howsoever minute, since once created these channels would remain available as a path for water to flow when it rains.

Naturally Percolating Streams Find Recharge Shafts
Naturally Percolating Streams Find Recharge Shafts


We at SILVERON, understand the importance of considering all natural factors when designing a rainwater harvesting structure. These variations make the scope of work differ from location to location. Site specific work of such magnitude calls for years of experience and understanding on the part of the harvester.

Ingenuity, untiring efforts, trials, determination to succeed and decades of experience stand behind the performance of SILVERON Rainwater Harvesting Systems.

The wide acceptance and appreciation of the performance of SILVERON recharge shafts makes SILVERON the first choice in the field of water conservation.

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.

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.


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.


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

1.  Scientific and human error possibilities to the extent of 15% cannot be ruled out both in quantitative and qualitative assessment of ground water.

 2. Increased ground water development activity in and around the area investigated may also effect rate of subsurface flow of water in the area in the years to come.

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.