Ground Water: Environment for UPSC
- Titbit: 22 March is celebrated as the world water day.
- General Assembly of the United Nations proclaimed the period 2005 – 2015 as the International Decade for action on “Water for life”
- The moisture in the soil indicates the presence of water underground.
- If we dig deeper and deeper, we would reach a level where all the space between particles of soil and gaps between rocks are filled with water. The upper limit of this layer is called the water table.
- The water table may be at a depth of less than a meter or maybe several meters below the ground. The water found below the water table is called groundwater.
- The process of seeping of water into the ground is called infiltration.
- At places, the groundwater is stored between layers of hard rock below the water table. This is known as an aquifer.
- The rainwater can be used to recharge the groundwater. This is referred to as water harvesting.
- Mahatma Gandhi said: “No one needs to wait for anyone else to adopt a humane and the enlightened course of action.”
Groundwater Contaminants and Their Effects
- Dissolved nitrates commonly contaminate groundwater.
- Excess nitrate in drinking water reacts with hemoglobin to form non-functional methemoglobin and impairs oxygen transport. This condition is called methemoglobinemia or blue baby syndrome.
- Methemoglobin is a form of the oxygen-carrying metalloprotein hemoglobin. Methemoglobin cannot bind oxygen, unlike oxyhemoglobin.
- High level of nitrates may form carcinogens and can accelerate eutrophication in surface waters.
Poor hygiene of wells may cause pathogenic contamination. Water seepage from solid waste dumps and municipal drains may also cause pathogenic contamination.
- Include a lead, mercury, cadmium, copper, chromium, and nickel. These metals can be toxic and carcinogenic.
- Seepage of industrial and mine discharges, fly ash ponds of thermal power plants can lead to metals in groundwater.
- In India and Bangladesh [Ganges Delta], millions of people are exposed to groundwater contaminated with high levels of arsenic, a highly toxic and dangerous pollutant.
- Chronic exposure to arsenic causes black foot disease. It also causes diarrhea, peripheral neuritis, hyperkeratosis and also lung and skin cancer.
- Seepage of agricultural runoff loaded with organic compounds like pesticides and may cause pesticide pollution of groundwater.
- Excess fluoride in drinking water causes neuromuscular disorders, gastro-intestinal problems, teeth deformity, hardening of bones and stiff and painful joints (skeletal fluorosis).
- Fluorosis is a common problem in several states of the country due to the intake of high fluoride content water.
- Fluorides cause dental fluorosis, stiffness of joints (particularly spinal cord) causing humped back.
- Pain in bones and joints and outward bending of legs from the knees is called KnockKnee syndrome.
- The high concentration of fluoride ions is present in drinking water in 13 states of India. The maximum level of fluoride, which the human body can tolerate is 1.5 parts per million (mg/L of water). Long term ingestion of fluoride ions causes fluorosis.
Major Water Issues Of India
- Due to the un-even distribution of rainfall in time and space and the ever-increasing demand of water for agricultural, industrial and domestic activities, the water resources are overexploited. This is resulting in shrinking or even drying up of many water bodies for
considerable periods in a year.
- Reducing demands by optimum use, minimization of wastage, efforts to reduce the percolation and evaporation losses, conservation efforts in domestic uses, groundwater recharging, rainwater harvesting, afforestation, recycling, and reuse are important to combat this problem.
- Water borne diseases are the most important water quality issues in India. This is mainly due to inadequate arrangements for the transport and treatment of wastewaters.
- Eutrophication [oxygen depletion due to algal blooms] is a common problem in most of the India lakes and rivers due to the discharge of untreated sewage and industrial effluents.
- There is a number of cases where salinity is increasing in both surface water and groundwater.
- The increase in groundwater salinity is mainly due to increased irrigation activities or seawater intrusion in coastal areas.
- Due to the discharge of toxic effluents from many industries and increased use of chemicals in agriculture and their subsequent contribution to the water bodies, many waters bodies in the country are polluted due to the presence of toxic substances.
- A large number of areas in our aquatic environment support rare species of aquatic and amphibious plants and animals and are, therefore, ecologically very sensitive. They need special protection.
Water Conservation and Management
- The primary source of water in India is south-west and north-east monsoons. Monsoon, however, is erratic and the amount of rainfall is highly variable in different parts of our country. Hence, surface runoff needs are conserved.
- Can you imagine the amount of water that one can save if one didn’t have to flush the toilet? Well, this is already a reality. Ecological sanitation is a sustainable system for handling human excreta, using dry composting toilets.
- This is a practical, hygienic, efficient and cost-effective solution to human waste disposal.
- With this composting method, human excreta can be recycled into a resource (as natural fertilizer), which reduces the need for chemical fertilizers. There are working ‘EcoSan’ toilets in many areas of Kerala and Sri Lanka.
- Designed by – Railways along with DRDO.
Why Bio Toilets in Rail?
- Direct discharge of human waste from the existing toilet system in trains causes corrosion of the tracks, costing crores to replace the rail tracks.
- The bio-toilets are fitted underneath the lavatories and the human waste discharged into them is acted upon by a particular kind of bacteria that converts it into noncorrosive neutral water.
Terms associated with Bio-Toilets
- Bio-digesters: The term biodigester is used for the shells made up of steel for the anaerobic digestion of human waste.
- Bio tank: The term bio tank is used for the tanks made up of concrete for the anaerobic digestion of human waste.
- Aerobic Bacteria: Aerobic bacteria are those which flourish in the presence of free dissolved oxygen in the wastewater and consume organic matter for their food, and thereby oxidizing it to stable end products.
- Anaerobic Bacteria: Anaerobic bacteria flourish in the absence of free dissolved oxygen, and survive by utilizing the bounded molecular oxygen in compounds like nitrates (NO3) and sulfates (SO4), etc. thereby reducing them to stable end products along with the evolution of foul-smelling gases likeH2S (hydrogen sulfide), CH4 (methane), etc.
- Facultative Bacteria: Facultative bacteria can operate either as aerobically or as anaerobically.
- Anaerobic Microbial inoculums: the mixture of different types of bacteria (hydrolytic, Acidogenic, acetogenic and methanogenic groups) responsible for the breakdown of complex polymers into simple sugars which are further broken down into the low chain
fatty acids and finally into biogas.
Anaerobic biodegradation system
- Anaerobic digestion is a collection of processes by which microorganisms break down biodegradable material in the absence of oxygen.
- The final waste is Methane and Carbon Dioxide.
Aerobic biodegradation Vs Anaerobic biodegradation
- Forced aeration is essential which is energy-intensive.
- Incomplete aeration (partial aerobic condition) leads to a foul smell.
- Less effective pathogen inactivation.
- Cannot tolerate detergents
- Generate a large amount of sludge.
- Repeated addition of bacteria/enzyme is required for the process.
- Maintenance & recurring cost is high.
- No aeration is required.
- Complete anaerobic conditions.
- More than 99% pathogen inactivation.
- Anaerobes can even degrade detergents/phenyl
- Sludge generation is very less.
- One-time bacterial inoculation is enough.
- Minimal maintenance and no recurring cost.
- Contour farming is an example of a harvesting technique involving water and moisture control at a very simple level.
- It often consists of rows of rocks placed along the contour of steps. Runoff captured by these barriers also allows for retention of soil, thereby serving as an erosion control measure on gentle slopes.
- This technique is especially suitable for areas having rainfall of considerable intensity, spread over large part i.e. in Himalayan area, northeast states and Andaman and The Nicobar Islands.
- In areas where rainfall is scanty and for a short duration, it is worth attempting these techniques, which will induce surface runoff, which can then be stored.
- Increasing the surface area for percolation, percolation tank construction, etc. are some artificial recharge methods.
Catchment area protection (CAP)
- It helps in withholding runoff water albeit temporarily by a check bund constructed across the streams in hilly terrains to delay the runoff so that greater time is available for water to seep underground.
- Such methods are in use in north-east states, in hilly areas of tribal belts. This technique also helps in soil conservation. Afforestation in the catchment area is also adopted for water and soil conservation.
Inter-basin transfer of water
- Western and peninsular regions have comparatively low water resources/cultivable land ratio. The northern and eastern region which are drained by Ganga and Brahmaputra have substantial water resources.
- Hence, the scheme of diverting water from the region with surplus water to water deficit the region can be adopted.
- Ganga-Cauvery link would enable the transfer of vast quantities of Ganga basin flood water running out to sea, to the west and southwest India.
- The transfer of the surplus Ganga water would make up for the periodical shortage in Son, Narmada, Godavari, Krishna, and Cauvery.
Adoption of drip sprinkler irrigation
- Surface irrigation methods lead to water loss due to evaporation and percolation.
- Drip irrigation is an efficient method of irrigation in which a limited area near the plant is irrigated by dripping water. This method is particularly useful in row crop.
- Similarly, the sprinkler method is also suitable for such water-scarce areas. About 80% of water consumption can be reduced by this method, whereas drip irrigation can reduce water consumption by 50 to 70 %.
Management of growing pattern of crops
- In water-scarce areas, the crop selection should be based on the efficiency of the crop to utilize the water. Some of the plants suitable for water-scarce areas are:
- plants with a shorter growth period;
- high yielding plants that require no
- increase in water supply;
- plants with deep and well trenched
- roots and
- plants which cannot tolerate surface
- plants with a shorter growth period;
Selection of crop varieties
- Crop performance and yield are the results of genotype expression as modulated by continuous interactions with the environment.
- Generally, the new varieties of crop do not require more water than the older ones. However, they require a timely supply of water because their productivity is high.
- Frequent light irrigation is more conductive than heavy irrigation at large intervals for obtaining high yields.
- Potassium plays a major role in stress conditions. It improves the tissue water potential by osmoregulation, ultimately increasing the water use efficiency.
- Experiments conducted at the Water Technology Centre, Coimbatore, indicated that foliar application of 0.5% potassium chloride can reduce the moisture stress in soybean, sorghum, and groundnut.
Role of antitranspirants
- Application of antitranspirants reduces transpiration maintaining thereby the tissue water potential. Plants then take up less water from the soil.
- Antitranspirants can prolong the irrigation intervals by slowing down soil water depletion. Application of Kaolin (3%) and lime wash (2%) was found to maintain the water balance of plant and resulted in a normal yield of sorghum under moisture stress
- Certain growth regulators reduce the plant’s susceptibility to water stress. Application ofcycoel, a growth retardant increases the ability to withstand drought.
- The cycoel application also reduces the production of gibberellic acid which leads to the closing of stomata. Transpiration loss of water gets reduced.
- Evapotranspiration losses can be reduced by reducing the evaporation from the soil surface and transpiration from the plants, in arid zones, a considerable amount of water is lost in evaporation from the soil surface.
- This can be prevented by placing watertight moisture barriers or watertight mulches on the soil surface. Nonporous materials like papers, asphalt, plastic foils or metal foils can also be used for preventing evaporation losses.
- Transpiration losses can be reduced by reducing air movement over a crop by putting windbreaks and evolving such types of crops which possess xerophytic adaptations.
Recycling of water
- The wastewater from industrial or domestic sources can be used after proper treatment, for irrigation, recharging groundwater, and even for industrial or municipal use. If agricultural lands are available close to cities, municipal waste water can be easily used for irrigation.
Reuse of wastewater
- Wastewater contains lots of nutrients. Its use for irrigation saves these nutrients. It improves the productivity of crops and soil fertility.
- Wastewater is a resource rather than a waste since it contains an appreciable amount of nitrogen, phosphorus, and potash.
- Stabilization ponds can be used for fish aquaculture. The effluent can also be used for cultivation of short-term and long term, ornamental, commercial and fodder crops.
- The potential applications of reusing of treated wastewater are in the following fields or areas:
- Agricultural use through irrigation of crops as well as for improving river amenity;
- Industrial cooling especially in large industrial enterprises;
- Reuse in municipal public areas such as watering lawns, parks, playgrounds, and trees;
- Flushing toilets in hotels and residential districts;
- Reuse of the treated wastewater for urban landscape purposes.
- Treated wastewater can also be used for groundwater recharging.
- Agricultural use through irrigation of crops as well as for improving river amenity;
- Greywater is defined as untreated household wastewater, which has not come into contact with toilet waste. It can originate from the shower, bath, bathroom, washing basin, clothes washing machine and laundry trough. Greywater can be used in agriculture and many industries.
Reduce the loss of water due to evaporation
- The methods that reduce evaporation from water bodies are – installing windbreaks, reducing the energy available for evaporation, constructing artificial aquifers, minimizing
exposed surface through reservoir regulation, reducing the ratio of area/volume of water bodies, locating reservoirs at higher altitudes and applying monomolecular firms.
- There are numerous methods to reduce losses due to evaporation and to improve soil moisture. Some of them are listed below:
- Mulching i.e. the application of organic or inorganic materials such as plant debris, compost, etc., slows down the surface run-off, improves soil moisture, reduces evaporation losses and improves soil fertility.
- Soil covered by crops, slow down run-off and minimize evaporation losses, hence, fields should not be left bare for long periods of time.
- Plowing helps to move the soil around. As a consequence, it retains more water thereby reducing evaporation.
- A shelter belt of trees and bushes along the edge of agricultural fields slow down the wind speed and reduce evaporation and erosion.
- Planting of trees, grass, and bushes breaks the force of rain and helps rainwater penetrate the soil.
- Fog and dew contain substantial amounts of water that can be used directly by adapted plant species. Artificial surfaces such as netting surface traps or polythene sheets can be exposed to fog and dew; the resulting water can be used for crops.
- Contour farming is adopted in hilly areas and in lowland areas for paddy fields. Farmers recognize the efficiently of contour-based systems for conserving soil and water.
- Salt-resistant varieties of crops have been also developed recently. Because these grow in saline areas, overall agricultural productivity is increased without making additional demands on freshwater sources. Thus, this is a good water conservation strategy.
- Desalination technologies such as distillation, electrodialysis, and reverse osmosis are available.
Water Treatment for Domestic Use
- Substances that are removed during the process of drinking water treatment include suspended solids, bacteria, algae, viruses, fungi, and minerals such as iron and manganese.
- The processes involved in removing the contaminants include physical processes such as settling and filtration, chemical processes such as disinfection and coagulation and biological processes such as slow sand filtration.
Coagulation / Flocculation
- Aluminum sulfate (alum) is the most common coagulant used for water purification. Other chemicals, such as ferric sulfate or sodium aluminate, may also be used.
- During coagulation, liquid aluminum sulfate (alum) is added to untreated water.
- This causes the tiny particles of dirt in the water to stick together or coagulate.
- Next, groups of dirt particles stick together to form larger particles called flocs.
- Flocs are easier to remove by settling or filtration.
- As the water and the floc particles progress through the treatment process, they move into sedimentation basins where the water moves slowly, causing the heavy floc particles to settle to the bottom.
- Floc which collects on the bottom of the basin is called sludge and is piped to drying lagoons.
- In Direct Filtration, the sedimentation step is not included, and the floc is removed by filtration only.
- Water flows through a filter designed to remove particles in the water. The filters are made of layers of sand and gravel, and in some cases, crushed anthracite.
- Filtration collects the suspended impurities in water and enhances the effectiveness of disinfection. The filters are routinely cleaned by backwashing.
- Water is disinfected before it enters the distribution system to ensure that any disease-causing bacteria, viruses, and parasites are destroyed.
- Chlorine is used because it is a very effective disinfectant and residual concentrations can be maintained to guard against possible biological contamination in the water distribution system.
- The addition of chlorine or chlorine compounds to drinking water is called chlorination.
- Chlorine can combine with certain naturally occurring organic compounds in water to produce chloroform and other potentially harmful byproducts.
- The risk of this is very small, however, when chlorine is applied after coagulation, sedimentation, and filtration.
- Ozone gas may also be used for disinfection of drinking water. However, since ozone is unstable, it cannot be stored and must be produced on-site, making the process more expensive than chlorination.
- Ozone has the advantage of not causing taste or odor problems. It also leaves no residue in the disinfected water.
- The lack of an ozone residue, however, makes it difficult to monitor its continued effectiveness as water flows through the distribution system.
- Solids that are collected and settled out of the water by sedimentation and filtration are removed to drying lagoons.
- Water fluoridation is the treatment of community water supplies for the purpose of adjusting the concentration of the free fluoride ion to the optimum level sufficient to reduce dental caries.
- Fluoride is generally present in all natural water. Its concentration up to a certain level is not harmful. Beyond that level, the bones start disintegrating. This disease is called fluorosis.
- We have fluoride problem in many parts of our country. Bureau of Indian Standards prescribes 1.0 mg/l as desirable and 1.5 mg/l as the maximum permissible limit for drinking
- Defluoridation at domestic level can be carried out by mixing water for treatment with an adequate amount of aluminum sulfate (alum) solution, lime or sodium carbonate and bleaching powder depending upon its alkalinity (concentration of bicarbonates and
carbonates in water) and fluoride contents.
- Lime is added to the filtered water to adjust the pH and stabilize the naturally soft water in order to minimize corrosion in the distribution system and within customers’ plumbing.
- Titbit: National Environmental Engineering Research Institute (NEERI) is at Nagpur.
Removal of iron
- In many parts of our country, we have a problem of excess iron in drinking water, especially in North-East regions. Iron causes bad taste and odor to the drinking water. Bureau of Indian Standards prescribes desirable limit for iron as 0.3 mg/l.
- A major part of iron is oxidized. Then the water is made to react with oxidizing media (limestone). By aeration and further oxidation, the dissolved iron is converted to insoluble ferric hydroxide. The insoluble iron can thus be easily removed through
Removal of arsenic
- Arsenic is found in groundwater in some parts of West Bengal. Arsenic is highly toxic in nature. It may cause a number of skin disorders or even cancer. Bureau of Indian Standards prescribes desirable limit for arsenic as 0.05 mg/l.
- Removal of arsenic is essential.
- Bleaching powder and alum are used for the removal of arsenic.
- Watershed is an area that contribute water to a stream or a water body through runoff or underground path.
- That is the region from which surface water draws into a river, a lake, wet land or other body of water is called its watershed or drainage basin.
- Watershed management is a technique for conservation of water and soil in a watershed.
- The presence of water in soil is essential for the growth of plants and vegetation. Forests and their associated soils and litter layers are excellent filters as well as sponges, and water that passes through this system is relatively pure.
- Various kinds of forest disturbances can speed up the movement of water from the system and in effect, reduce the filtering action.
- In mountainous terrain, the forests play a prominent role in the prevention of soil erosion.
- Erosion threat can be tackled by the maintenance of continual cover. Ideally, this is achieved by single stem harvesting; only one tree is felled at any one point and the small gap so created is soon sealed by the outward growth of its neighbors.
- Despite the uncertain balance of water gain and loss, forests offer the most desirable cover for water management strategies.
- In contrast to the rapid flows of short duration characteristics of sparsely vegetated land water yields are gradual, reliable and uniform in forests. Deforested land sheds water swiftly, causing sudden rises in the rivers below.
- Over a large river system, such as that of the Ganga and the Yamuna, forests are a definite advantage since they lessen the risk of floods. They also provide conditions more favorable to fishing and navigation than does un-forested land.
- All-natural streams contain varying amounts of dissolved and suspended matter, although streams contain varying amounts of dissolved and
- suspended matter, although streams issuing from undisturbed watershed are ordinarily of high quality.
- Waters from forested areas are not only low in foreign substances, but they also are relatively high in oxygen and low in unwanted chemicals.
- The belief that forests increase rainfall has not been substantiated by scientific inquiry. Local effects can, however, prove substantial, particularly in semiarid regions where every millimeter of rain counts.
- The air above a forest, as contrasted with grassland, remains relatively cool and humid on hot days, so that showers are more frequent.
- Many areas in India used to get significant rainfall when they were forested are now facing severe drought due to denudation (example Rajasthan desert).
Individual And Community Role
- Building check dams on seasonal rivers.
- Micro-watershed management project.
- Constructing percolation tanks in every residential and industrial complex.
- Rooftop rainwater collection for drinking purposes. [2/3rd of water is wasted in RO – reverse osmosis filtration]
Government’s efforts on water conservation
- National Water Policy 2002 strongly emphasize conservation of water.
- Construction of a large number of dams on various river systems.
- Interlinking of rivers (proposed).
- Promotion of bunds at the village level.
- Promotion of rainwater harvesting.
- Promotion of reuse and recycling of wastewater.
- Steps to protect water quality.
- Drought-proofing the future.
- Permanent conservation measures may include:
- Subsidizing use of water-efficient faucets, toilets, and showerheads
- Public education and voluntary use reduction.
- Billing practices that impose higher rates for higher amounts of water use
- Building codes that require water-efficient fixtures or appliances
- Leak detection surveys and meter testing, repair and replacement.
- Reduction in use and increase in recycling of industrial water
- Subsidizing use of water-efficient faucets, toilets, and showerheads
- Temporary cutbacks may include:
- Reduction of a system-wide operating pressure
- Water use bans, restrictions, and rationing
- Strengthening of local or municipal bodies could help to address the issue of water shortage and its management in cities.
- Reduction of a system-wide operating pressure