Notes on Water
Water resources are sources of water that are useful or potentially useful to humans. Water is essential for all forms of life, and this is no different for people. Many uses of water include agricultural, industrial, household, recreational and environmental activities. Virtually all of these human uses require fresh water. 88.7% of water on the Earth is salt water, and over two thirds of fresh water is frozen in glaciers and polar ice caps, leaving only 0.9% available for human use. Fresh water is a renewable resource, yet the world's supply of clean, fresh water is steadily decreasing. Water demand already exceeds supply in many parts of the world, and as world population continues to rise at an unprecedented and unsustainable rate, many more areas are expected to experience this imbalance in the near future. The framework for allocating water resources to water users (where such a framework exists) is known as water rights.
Surface water
Surface water is water in a river, lake or fresh water wetland. Surface water is naturally replenished by precipitation and naturally lost through discharge to the oceans, evaporation, and sub-surface seepage.
Although the only natural input to any surface water system is precipitation within its watershed, the total quantity of water in that system at any given time is also dependent on many other factors. These factors include storage capacity in lakes, wetlands and artificial reservoirs, the permeability of the soil beneath these storage bodies, the runoff characteristics of the land in the watershed, the timing of the precipitation and local evaporation rates. All of these factors also affect the proportions of water lost.
Human activities can have a large impact on these factors. Humans often increase storage capacity by constructing reservoirs and decrease it by draining wetlands. Humans often increase runoff quantities and velocities by paving areas and channelizing stream flow.
The total quantity of water available at any given time is an important consideration. Some human water users have an intermittent need for water. For example, many farms require large quantities of water in the spring, and no water at all in the winter. To supply such a farm with water, a surface water system may require a large storage capacity to collect water throughout the year and release it in a short period of time. Other users have a continuous need for water, such as a power plant that requires water for cooling. To supply such a power plant with water, a surface water system only needs enough storage capacity to fill in when average stream flow is below the power plant's need.
Nevertheless, over the long term the average rate of precipitation within a watershed is the upper bound for average consumption of natural surface water from that watershed.
Natural surface water can be augmented by importing surface water from another watershed through a canal or pipeline. It can also be artificially augmented from any of the other sources listed here, however in practice the quantities are negligible. Humans can also cause surface water to be "lost" (i.e. become unusable) through pollution.
Sub-surface water
Sub-Surface water, or groundwater, is fresh water located in the pore space of soil and rocks. It is also water that is flowing within aquifers below the water table. Sometimes it is useful to make a distinction between sub-surface water that is closely associated with surface water and deep sub-surface water in an aquifer (sometimes called "fossil water").
Sub-surface water can be thought of in the same terms as surface water: inputs, outputs and storage. The critical difference is that due to its slow rate of turnover, sub-surface water storage is generally much larger compared to inputs than it is for surface water. This difference makes it easy for humans to use sub-surface water unsustainably for a long time without severe consequences. Nevertheless, over the long term the average rate of seepage above a sub-surface water source is the upper bound for average consumption of water from that source.
The natural input to sub-surface water is seepage from surface water. The natural outputs from sub-surface water are springs and seepage to the oceans.
If the surface water source is also subject to substantial evaporation, a sub-surface water source may become saline. This situation can occur naturally under endorheic bodies of water, or artificially under irrigated farmland. In coastal areas, human use of a sub-surface water source may cause the direction of seepage to ocean to reverse which can also cause soil salinization. Humans can also cause sub-surface water to be "lost" (i.e. become unusable) through pollution. Humans can increase the input to a sub-surface water source by building reservoirs or detention ponds.
Water in the ground is in sections called aquifers. Rain rolls down and comes into these. Normally an aquifer is near to the equilibrium in its water content. The water content of an aquifier normally depends on the grain sizes. This means that the rate of extraction may be limited by poor permeability.
a)What are the sources of water pollution?
Some of the principal sources of water pollution are: Geology of aquifers from which groundwater is abstracted, Industrial discharge of chemical wastes and byproducts, Discharge of poorly-treated or untreated sewage, Surface runoff containing pesticides or fertilizers, Slash and burn farming practice, which is often an element within shifting cultivation agricultural systems, Surface runoff containing spilled petroleum products, Surface runoff from construction sites, farms, or paved and other impervious surfaces e.g. silt, Discharge of contaminated and/or heated water used for industrial processes.
Acid rain caused by industrial discharge of sulphur dioxide (by burning high-sulphur fossil fuels), Excess nutrients are added (eutrophication) by runoff containing detergents or fertilizers, Underground storage tank leakage, leading to soil contamination, and hence aquifer contamination, Inappropriate disposal of various solid wastes and, on a localized scale, littering, Oil spills.
There are many causes for water pollution but two general categories exist: direct and indirect contaminant sources.
Direct sources include effluent outfalls from factories, refineries, waste treatment plants etc.. that emit fluids of varying quality directly into urban water supplies. In the United States and other countries, these practices are regulated, although this doesn't mean that pollutants can't be found in these waters.
Indirect sources include contaminants that enter the water supply from soils/groundwater systems and from the atmosphere via rain water. Soils and groundwaters contain the residue of human agricultural practices (fertilizers, pesticides, etc..) and improperly disposed of industrial wastes. Atmospheric contaminants are also derived from human practices (such as gaseous emissions from automobiles, factories and even bakeries).
Contaminants can be broadly classified into organic, inorganic, radioactive and acid/base. Examples from each class and their potential sources are too numerous to discuss here.
b)What are the effects of water pollution?
The effects of water pollution are varied. They include poisonous drinking water, poisionous food animals (due to these organisms having bioaccumulated toxins from the environment over their life spans), unbalanced river and lake ecosystems that can no longer support full biological diversity, deforestation from acid rain, and many other effects. These effects are, of course, specific to the various contaminants.
Contaminants may include organic and inorganic substances.
Some organic water pollutants are: Insecticides and herbicides, a huge range of organohalide and other chemicals, Bacteria, often is from sewage or livestock operations, Food processing waste, including pathogens, Tree and brush debris from logging operations, VOCs (Volatile organic compounds), such as industrial solvents, from improper storage, Petroleum Hydrocarbons including fuels (gasoline, diesel, jet fuels, and fuel oils) and lubricants (motor oil) from oil field operations, refineries, pipelines, retail service station's underground storage tanks, and transfer operations. Note: VOCs include gasoline-range hydrocarbons.
Some inorganic water pollutants include: Heavy metals including acid mine drainage,
Acidity caused by industrial discharges (especially sulfur dioxide from power plants), Pre-production industrial raw resin pellets (an industrial pollutant), Chemical waste as industrial by products : Fertilizers, in runoff from agriculture including nitrates and phosphates. Silt in surface runoff from construction sites, logging, slash and burn practices or land clearing sites.
The sources of water pollution typically fall into one of two categories: point-source pollution and non-point-source pollution.
The term point-source pollution refers to pollutants discharged from one discrete location or point, such as an industry or municipal wastewater treatment plant. Pollutants discharged in this way might include, for example, fecal coliform bacteria and nutrients from sewage, and toxics such as heavy metals, or synthetic organic contaminants.
The term non-point-source pollution refers to pollutants that cannot be identified as coming from one discrete location or point. Examples are oil and grease that enter the water with runoff from urban streets, nitrogen from fertilizers and pesticides, and animal wastes that wash into surface waters from agricultural lands. Natural and unknown causes of pollutants also can impact water quality and may be related to human activities. For example, highway or housing construction may help precipitate the runoff of natural pollution sources, such as sediment.
Potability of Water – Water for drinking
Regular testing is important to identify existing problems, ensure water is suitable for the intended use, ensure safe drinking water, and determine the effectiveness of a treatment system. The quality of a water source may change over time, even suddenly. Changes can go unnoticed as the water may look, smell, and taste the same.
Basic Water Potability Test packages include tests for coliform bacteria, nitrates, pH, sodium, chloride, fluoride, sulphate, iron, manganese, total dissolved solids, and hardness.
• Coliform bacteria tests indicate the presence of microorganisms in the water that are potentially harmful to human health.
• Nitrate is a common contaminant found mainly in groundwater. High nitrate concentrations can be particularly dangerous for babies under six months, since nitrate interferes with the ability of blood to carry oxygen.
• Ions such as sodium, chloride, sulphate, iron, and manganese can impart objectionable taste or odour to water.
• Excessive amounts of sulfate can have a laxative effect or cause gastrointestinal irritation.
• Fluoride is an essential micro-nutrient, but excessive amounts can cause dental problems.
• Total dissolved solids represent the amount of inorganic substances (i.e. sodium, chloride, sulphate) that are dissolved in the water. High total dissolved solids (TDS) can reduce the palatability of water.
Other tests may be appropriate if a particular contaminant is suspected in the water. For instance, groundwater sources are sometimes tested for arsenic, selenium, and uranium. Both surface and groundwater sources may also be tested for pesticide contamination. Domestic water supplies should be tested a minimum of once per year. Drinking water supplies obtained from shallow wells and surface water sources should be tested more frequently (i.e. seasonally), as they are more susceptible to contamination.
The following terms are commonly used as test parameters:
pH - represents the intensity of the acid or alkaline condition of a solution. A pH of 7 indicates neutral conditions on a scale of 0 (acidic) to 14 (alkaline).
Conductivity - measures the ability of water to conduct an electrical current, and is directly related to the total dissolved salts (ions) in the water.
Coliforms (Total) - bacteria found in faeces, soil, and vegetation, which is used to indicate the bacteriological quality of water. Coliforms indicate the possible presence of pathogenic bacteria and viruses.
Nitrate (NO3) - the most completely oxidized state of nitrogen found in water. High nitrate levels can occur naturally, but may indicate biological wastes in the water, or run-off from heavily fertilized fields. High nitrate levels reduce the ability of blood to transport oxygen to body tissues.
Total Hardness - mainly caused by the presence of calcium and magnesium in water, and is expressed as the equivalent quantity of calcium carbonate. Scale formation and excessive soap consumption are the main problems associated with hardness.
Total Dissolved Solids (TDS) - the total dissolved substances (i.e. salts and minerals) in water remaining after evaporating the water and weighing the residue.
Turbidity - represents the clarity of water. It is measured by the degree to which light is blocked because the water is muddy or cloudy.
Following are common questions and answers regarding the basic concepts of the bacterial indicator system used to monitor drinking water.
Q. Are there bacteria in properly treated potable water?
A. Yes. Drinking water regulations require that potable waters, water for human consumption, be free from human-disease-causing bacteria and specific indicator bacteria that are indicative of the presence of these pathogens. This does not mean that drinking water should be sterile. Keep in mind that not all bacteria are harmful to humans.
Q. What bacteria are harmful to the consumer?
A. There are some bacteria that have a greater probability of causing disease in humans. These bacteria are classified as pathogens. Examples of bacterial pathogens and their related diseases are Salmonella typhi (typhoid fever), Shigella dysenteriae (dysentery), and Legionella pneumophilia (Legionnaire's Disease).
There are other bacteria that will cause disease in humans, but this usually occurs in situations where the individual has been immuno-compromised. An immuno-compromised person can be very young or elderly, under antibiotic or chemotherapy treatment, undernourished, and so forth. Bacteria that cause disease in these individuals are classified as opportunistic pathogens. These bacteria take advantage of the compromised condition of the individual as an opportunity to develop disease symptoms. However, under normal or healthy conditions, the individual's own body defenses would prevent the disease from developing.
Q. How are bacteria indicative of contamination in drinking water?
A. Originally, the bacterial species and bacterial groups that are of regulatory concern were considered to be strictly associated with feces. However, it is now known that some of these bacteria can be isolated not only from human feces but also from the environment where no human fecal contamination has occurred. There is no easy or inexpensive way to differentiate the source of these bacteria when isolated from a drinking water sample. Therefore, erring on the side of safety, the regulations are based on the concept that the presence of these specific bacteria, regardless of their source, is indicative of fecal contamination from human or natural sources such as septic seepage, soils, and warm-blooded animals. This may seem unfair to the water treatment plant operator, but if the plant is operated efficiently and the distribution system is maintained properly, the probability of introducing these bacteria into the distribution system drinking water is minimal.
Q. What is coliform?
A. By definition, the term coliform group includes those bacteria that are aerobic and facultatively anaerobic, gram-negative, nonsporeforming, rod-shaped bacteria capable of fermenting lactose with gas and acid production within 48 h ± 4 h at 35°C ± 0.5°C.
Q. How does the technical definition of coliform group (previous answer) relate to a water treatment plant operator whose responsibility is the processing of water samples and interpretation of the results?
A. Admittedly, there is more information given in the definition of coliform group than is required to understand the basic concepts of the coliform indicator system. However, the descriptive terms used in the definition are necessary for classification of coliforms in relation to other bacteria and go beyond the intention of this handbook. The characteristic used for diagnostic purposes that you should be familiar with is the fermentation or utilization of lactose that produces gas bubbles and acid in the media.
Specific examples on how to interpret diagnostic results when using different types of media follow in later chapters. Also, depending on the technique used to analyze the water sample, such as multiple tube fermentation (MTF), presence-absence (PA), or membrane filter (MF), the definition for a coliform must be modified appropriately. Therefore, it is not important to memorize this definition. However, to understand why the definition must be modified when evaluating test results from the MTF technique versus the MF technique, it will be helpful to refer to this definition.
Q. What are fecal coliforms?
A. Fecal coliforms are defined in the same way as total coliforms except that fecal coliforms can ferment lactose at an elevated temperature when using standard media (44.5°C ± 0.2°C). This increase in incubation temperature inhibits the growth and lactose fermentation of the other total coliforms, which ferment lactose optimally at 35°C ± 0.5°C.
Q. Does the previous definition of fecal coliform apply to E. coli since it is a fecal coliform?
A. Yes. The only difference is in the standard media used to isolate E. coli.
Q. Why is E. coli considered to be more specific for indicating potable water contamination than the other total and fecal coliforms?
A. E. coli is more often directly associated with fecal contamination and disease outbreaks in potable waters than any of the other total or fecal coliforms. Recent developments in the technology for isolating, recovering, and identifying E. coli have made a once difficult task relatively simple, affordable, and dependable. Having a test that identifies the presence of a bacterium that is known to indicate the likelihood of fecal contamination gives the bacteriologist another technique for ensuring bacteriologically safe drinking water to the consumer.
Eutrophication is a process whereby water bodies, such as lakes, estuaries, or slow-moving streams receive excess nutrients that stimulate excessive plant growth (algae, periphyton attached algae, and nuisance plants weeds). This enhanced plant growth, often called an algal bloom, reduces dissolved oxygen in the water when dead plant material decomposes and can cause other organisms to die. Nutrients can come from many sources, such as fertilizers applied to agricultural fields, golf courses, and suburban lawns; deposition of nitrogen from the atmosphere; erosion of soil containing nutrients; and sewage treatment plant discharges. Water with a low concentration of dissolved oxygen is called hypoxic.
Eutrophication is caused by the decrease of an ecosystem with chemical nutrients, typically compounds containing nitrogen or phosphorus. It may occur on land or in the water. Eutrophication is frequently a result of nutrient pollution such as the release of sewage effluent into natural waters (rivers or coasts) although it may occur naturally in situations where nutrients accumulate (e.g. depositional environments) or where they flow into systems on an ephemeral basis (e.g. intermittent upwelling in coastal systems).
Eutrophication generally promotes excessive plant growth and decay, favors certain weedy species over others, and is likely to cause severe reductions in water quality. In aquatic environments, enhanced growth of choking aquatic vegetation or phytoplankton (that is, an algal bloom) disrupts normal functioning of the ecosystem, causing a variety of problems. Human society is impacted as well: eutrophication decreases the resource value of rivers, lakes, and estuaries such that recreation, fishing, hunting, and aesthetic enjoyment are hindered. Health-related problems can occur where eutrophic conditions interfere with drinking water treatment.
Although traditionally thought of as enrichment of aquatic systems by addition of fertilizers into lakes, bays, or other semi-enclosed waters (even slow-moving rivers), terrestrial ecosystems are subject to similarly adverse impacts. Increased content of nitrates in soil frequently leads to undesirable changes in vegetation composition and many plant species are endangered as a result of eutrophication in terrestric ecosystems, e.g. majority of orchid species in Europe. Ecosystems (like some meadows, forests and bogs that are characterized by low nutrient content and species-rich, slowly growing vegetation adapted to lower nutrient levels) are overgrown by faster growing and more competitive species-poor vegetation, like tall grasses, that can take advantage of unnaturally elevated nitrogen level and the area may be changed beyond recognition and vulnerable species may be lost. Eg. species-rich fens are overtaken by reed or reedgrass species, spectacular forest undergrowth affected by run-off from nearby fertilized field is turned into a thick nettle and bramble shrub.
Eutrophication was recognized as a pollution problem in European and North American lakes and reservoirs in the mid-20th century. Since then, it has become more widespread. Surveys showed that 54% of lakes in Asia are eutrophic; in Europe, 53%; in North America, 48%; in South America, 41%; and in Africa, 28%.
Concept of eutrophication
Eutrophication can be a natural process in lakes, as they fill in through geological time, though other lakes are known to demonstrate the reverse process, becoming less nutrient rich with time. Estuaries also tend to be naturally eutrophic because land-derived nutrients are concentrated where run-off enters the marine environment in a confined channel and mixing of relatively high nutrient fresh water with low nutrient marine water occurs.
Phosphorus is often regarded as the main culprit in cases of eutrophication in lakes subjected to point source pollution from sewage. The concentration of algae and the tropic state of lakes correspond well to phosphorus levels in water. Studies conducted in the Experimental Lakes Area in Ontario have shown a relationship between the addition of phosphorus and the rate of eutrophication. Humankind has increased the rate of phosphorus cycling on Earth by four times, mainly due to agricultural fertilizer production and application. Between 1950 and 1995, 600,000,000 tonnes of phosphorus were applied to Earth's surface, primarily on croplands. Control of point sources of phosphorus have resulted in rapid control of eutrophication, mainly due to policy changes.
Human activities can accelerate the rate at which nutrients enter ecosystems. Runoff
from agriculture and development, pollution from septic systems and sewers, and other human-related activities increase the flux of both inorganic nutrients and organic substances into terrestrial, aquatic, and coastal marine ecosystems (including coral reefs). Elevated atmospheric compounds of nitrogen can increase soil nitrogen availability.
Chemical forms of nitrogen are most often of concern with regard to eutrophication
because plants have high nitrogen requirements so that additions of nitrogen compounds stimulate plant growth (primary production). Nitrogen is not readily available in soil because N2, a gaseous form of nitrogen, is very stable and unavailable directly to higher plants. Terrestrial ecosystems rely on microbial nitrogen fixation to convert N2 into other physical forms (such as nitrates). However, there is a limit to how much nitrogen can be utilized. Ecosystems receiving more nitrogen than the plants require are called nitrogen-saturated. Saturated terrestrial ecosystems contribute both inorganic and organic nitrogen to freshwater, coastal, and marine eutrophication, where nitrogen is also typically a limiting nutrient. However, in marine environments, phosphorus may be limiting because it is leached from the soil at a much slower rate than nitrogen, which are highly insoluble.
Ecological effects
Adverse effects of eutrophication on lakes, reservoirs, rivers and coastal marine
waters
• Increased biomass of phytoplankton
• Toxic or inedible phytoplankton species
• Increases in blooms of gelatinous zooplankton
• Increased biomass of benthic and epiphytic algae
• Changes in macrophyte species composition and biomass
• Decreases in water transparency
• Taste, odor, and water treatment problems
• Dissolved oxygen depletion
• Increased incidences of fish kills
• Loss of desirable fish species
• Reductions in harvestable fish and shellfish
• Decreases in perceived aesthetic value of the water body
Many ecological effects can arise from stimulating primary production, but there are
three particularly troubling ecological impacts: decreased biodiversity, changes in species composition and dominance, and toxicity effects.
Decreased biodiversity
When an ecosystem experiences an increase in nutrients, primary producers reap the benefits first. In aquatic ecosystems, species such as algae experience a population increase (called an algal bloom). Algal blooms limit the sunlight available to bottom-dwelling organisms and cause wide swings in the amount of dissolved oxygen in the water.
Oxygen is required by all respiring plants and animals and it is replenished in daylight by photosynthesizing plants and algae. Under eutrophic conditions, dissolved oxygen greatly increases during the day, but is greatly reduced after dark by the respiring algae and by microorganisms that feed on the increasing mass of dead algae. When dissolved oxygen levels decline to hypoxic levels, fish and other marine animals suffocate. As a result, creatures such as fish, shrimp, and especially immobile bottom dwellers die off. In extreme cases, anaerobic conditions ensue, promoting growth of bacteria such as Clostridium botulinum that produces toxins deadly to birds and mammals. Zones where this occurs are known as dead zones.
Sources of high nutrient runoff
Characteristics of point and nonpoint sources of chemical inputs
Point sources
• Wastewater effluent (municipal and industrial)
• Runoff and leachate from waste disposal systems
• Runoff and infiltration from animal feedlots
• Runoff from mines, oil fields, unsewered industrial sites
• Overflows of combined storm and sanitary sewers
• Runoff from construction sites >20,000 m²
Nonpoint Sources
• Runoff from agriculture/irrigation
• Runoff from pasture and range
• Urban runoff from unsewered areas
• Septic tank leachate
• Runoff from construction sites <20,000 m²
• Runoff from abandoned mines
• Atmospheric deposition over a water surface
• Other land activities generating contaminants
Point sources are directly attributable to one influence. In point sources the nutrient waste travels directly from source to water. For example, factories that have waste discharge pipes directly leading into a water body would be classified as a point source. Point sources are relatively easy to regulate.
Nonpoint source pollution (also known as 'diffuse' or 'runoff' pollution) is that which comes from ill-defined and diffuse sources. Nonpoint sources are difficult to regulate and usually vary spatially and temporally (with season, precipitation, and other irregular events). It has been shown that nitrogen transport is correlated with various indices of human activity in watersheds, including the amount of development. Agriculture and development are activities that contribute most to nutrient loading.
There are three reasons that nonpoint sources are especially troublesome:
• Soil retention
• Runoff to surface water and leaching to groundwater
• Atmospheric deposition
Prevention and reversal
Eutrophication poses a problem not only to ecosystems, but to humans as well. Reducing eutrophication should be a key concern when considering future policy, and a sustainable solution for everyone, including farmers and ranchers, seems feasible. While eutrophication does pose problems, humans should be aware that natural runoff (which causes algal blooms in the wild) is common in ecosystems and should thus not reverse nutrient concentrations beyond normal levels.
Cleanup measures have been mostly, but not completely, successful. Finish phosphorus removal measures started in the mid-1970s and have targeted rivers and lakes polluted by industrial and municipal discharges. These efforts have had a 90% removal efficiency. Still, some targeted point sources did not show a decrease in runoff despite reduction efforts.
Impact of farming
Farming is what makes possible the production of food surpluses and settled living. It also brings about big changes in the relationships between living things and in their habitats. Farming - especially modern, intensive farming can damage the environment in many different ways.
Effect of fertilizers
Fertilisers containing plant nutrients are sprayed onto fields to make plants grow faster and boost crop yields. When it rains the nutrients may get washed down from the fields and into rivers and lakes (this is called run-off). The result is eutrophication – which can kill almost everything living in the aquatic environment. It works like this:
Effect of pesticides
Pesticides are chemicals used to kill insects, weeds and microorganisms that might damage crops. However, pesticides damage other organisms apart from those they are intended to kill - for example, depriving insect-eating birds of food. Pesticides can also enter local food chains. Organisms that ingest them cannot break them down, so they persist in their bodies. (Substances that cannot be broken down are called persistent substances: the pesticide DDT is an example.) The pesticides may then build up at ever-higher levels until they become toxic to much larger organisms.
Other impacts of farming
Agriculture can impact on the environment in many other ways. For example:
• farming takes up land, reducing habitats and wildlife
• monocultures (large amounts of one type of food) provide lots of food for
pests as well as humans
• irrigation (watering of crops) may take too much water from rivers, depriving
downstream habitats of water
• clearing land for farming may result in soil erosion, damaging ecosystems
and leaving land barren
• Intensive livestock farming produces huge amount of faeces, which may
pollute waterways
Rainwater Harvesting is the collection and storage of rain from roofs or from a surface catchment for future use. The water is generally stored in rainwater tanks or directed into mechanisms which recharge groundwater. This is appropriate in many parts of the world, such as western Britain, China, Brazil, Thailand, Sri Lanka, Germany, Australia and India, where there is enough rain for collection and conventional water resources either do not exist or are at risk of being over-used to supply a large population. Rainwater harvesting can provide lifeline water for human consumption, reduce water bills and the need to build reservoirs which may require the use of valuable land.
Traditionally, rainwater harvesting has been practised in arid and semi-arid areas, and has provided drinking water, domestic water, water for livestock, water for small irrigation and a way to replenish ground water levels. This method may have been used extensively by the Indus Valley Civilization.
Currently in China and Brazil, rooftop rainwater harvesting is being practised for use for all the above purposes. Gansu province in China and semi-arid north east Brazil have the largest rooftop rainwater harvesting projects ongoing.
Rainwater harvesting in urban areas can have manifold reasons. To provide supplemental water for the city's requirement, to increase soil moisture levels for urban greenery, to increase the ground water table through artificial recharge, to mitigate urban flooding and to improve the quality of groundwater are some of the reasons why rainwater harvesting can be adopted in cities. In urban areas of the developed world, at a household level, harvested rainwater can be used for flushing toilets and washing laundry. Indeed in hard water areas it is superior to mains water for this. It can also be used for showering or bathing. It may require treatment prior to use for drinking.
Two residences in the city of Toronto, Canada, use treated harvested rainwater for drinking water, and reuse water (i.e. treated wastewater) for all other household water applications including toilet flushing, bathing, showers, laundry, and garden irrigation (Toronto Healthy House).
In New Zealand, many houses away from the larger towns and cities routinely rely on rainwater collected from roofs as the only source of water for all household activities.
RAIN WATER HARVESTING AND ARTIFICIAL RECHARGE TO GROUND WATER
WHAT IS RAIN WATER HARVESTING :
It is the principle of collecting and using precipitation from a catchments surface. An old technology is gaining popularity in a new way. Rain water harvesting is enjoying a renaissance of sorts in the world, but it traces its history to biblical times. Extensive rain water harvesting apparatus existed 4000 years ago in the Palestine and Greece. In ancient Rome, residences were built with individual cisterns and paved courtyards to capture rain water to augment water from city's aqueducts. As early as the third millennium BC, farming communities in Baluchistan and Kutch impounded rain water and used it for irrigation dams.
ARTIFICAL RECHARGE TO GROUND WATER :
Artificial recharge to ground water is a process by which the ground water reservoir is augmented at a rate exceeding that obtaining under natural conditions or replenishment. Any man-made scheme or facility that adds water to an aquifer may be considered to be an artificial recharge system.
WHY RAIN WATER HARVESTING :
Rain water harvesting is essential because :-
Surface water is inadequate to meet our demand and we have to depend on ground water.
Due to rapid urbanization, infiltration of rain water into the sub-soil has decreased drastically and recharging of ground water has diminished.
As you read this guide, seriously consider conserving water by harvesting and managing this natural resource by artificially recharging the system. The examples covering several dozen installations successfully operating in India constructed and maintained by CGWB, provide an excellent snapshot of current systems.
RAIN WATER HARVESTING TECHNIQUES :
There are two main techniques of rain water harvestings. Storage of rainwater on surface for future use. Recharge to ground water.
The storage of rain water on surface is a traditional techniques and structures used were underground tanks, ponds, check dams, weirs etc. Recharge to ground water is a new concept of rain water harvesting and the structures generally used are:-
Pits :- Recharge pits are constructed for recharging the shallow aquifer. These are constructed 1 to 2 m, wide and to 3 m. deep which are back filled with boulders, gravels, coarse sand.
Trenches:- These are constructed when the permeable stram is available at shallow depth. Trench may be 0.5 to 1 m. wide, 1 to 1.5m. deep and 10 to 20 m. long depending up availability of water. These are back filled with filter. materials.
Dug wells:- Existing dug wells may be utilised as recharge structure and water should pass through filter media before putting into dug well.
Hand pumps :- The existing hand pumps may be used for recharging the shallow/deep aquifers, if the availability of water is limited. Water should pass through filter media before diverting it into hand pumps.
Recharge wells :- Recharge wells of 100 to 300 mm. diameter are generally constructed for recharging the deeper aquifers and water is passed through filter media to avoid choking of recharge wells.
Recharge Shafts :- For recharging the shallow aquifer which are located below clayey surface, recharge shafts of 0.5 to 3 m. diameter and 10 to 15 m. deep are constructed and back filled with boulders, gravels & coarse sand.
Lateral shafts with bore wells :- For recharging the upper as well as deeper aquifers lateral shafts of 1.5 to 2 m. wide & 10 to 30 m. long depending upon availability of water with one or two bore wells are constructed. The lateral shafts is back filled with boulders, gravels & coarse sand.
Spreading techniques :- When permeable strata starts from top then this technique is used. Spread the water in streams/Nalas by making check dams, nala bunds, cement plugs, gabion structures or a percolation pond may be constructed.
HARVESTING RAINWATER HARNESSING LIFE : A NOBLE GOAL - A COMMON RESPONSIBILITY
Ground water exploitation is inevitable is Urban areas. But the groundwater potential is getting reduced due to urbanisation resulting in over exploitation. Hence, a strategy to implement the groundwater recharge, in a major way need to be launched with concerted efforts by various Governmental and Non-Governmental Agencies and Public at large to build up the water table and make the groundwater resource, a reliable and sustainable source for supplementing water supply needs of the urban dwellers.
Recharge of groundwater through storm run off and roof top water collection, diversion and collection of run off into dry tanks, play grounds, parks and other vacant places are to be implemented by Special Village Panchayats/ Municipalities /Municipal Corporations and other Government Establishments with special efforts.
The Special Village Panchayats /Municipalities/Municipal Corporations will help the citizens and builders to adopt suitable recharge method in one's own house or building through demonstration and offering subsidies for materials and incentives, if possible.
ATTRIBUTES OF GROUNDWATER :
o There is more ground water than surface water
o Ground water is less expensive and economic resource.
o Ground water is sustainable and reliable source of water supply.
o Ground water is relatively less vulnerable to pollution
o Ground water is usually of high bacteriological purity.
o Ground water is free of pathogenic organisms.
o Ground water needs little treatment before use.
o Ground water has no turbidity and colour.
o Ground water has distinct health advantage as art alternative for lower sanitary quality surface water.
o Ground water is usually universally available.
o Ground water resource can be instantly developed and used.
o There is no conveyance losses in ground water based supplies.
o Ground water has low vulnerability to drought.
o Ground water is key to life in arid and semi-arid regions.
o Ground water is source of dry weather flow in rivers and streams.
Water resources are sources of water that are useful or potentially useful to humans. Water is essential for all forms of life, and this is no different for people. Many uses of water include agricultural, industrial, household, recreational and environmental activities. Virtually all of these human uses require fresh water. 88.7% of water on the Earth is salt water, and over two thirds of fresh water is frozen in glaciers and polar ice caps, leaving only 0.9% available for human use. Fresh water is a renewable resource, yet the world's supply of clean, fresh water is steadily decreasing. Water demand already exceeds supply in many parts of the world, and as world population continues to rise at an unprecedented and unsustainable rate, many more areas are expected to experience this imbalance in the near future. The framework for allocating water resources to water users (where such a framework exists) is known as water rights.
Surface water
Surface water is water in a river, lake or fresh water wetland. Surface water is naturally replenished by precipitation and naturally lost through discharge to the oceans, evaporation, and sub-surface seepage.
Although the only natural input to any surface water system is precipitation within its watershed, the total quantity of water in that system at any given time is also dependent on many other factors. These factors include storage capacity in lakes, wetlands and artificial reservoirs, the permeability of the soil beneath these storage bodies, the runoff characteristics of the land in the watershed, the timing of the precipitation and local evaporation rates. All of these factors also affect the proportions of water lost.
Human activities can have a large impact on these factors. Humans often increase storage capacity by constructing reservoirs and decrease it by draining wetlands. Humans often increase runoff quantities and velocities by paving areas and channelizing stream flow.
The total quantity of water available at any given time is an important consideration. Some human water users have an intermittent need for water. For example, many farms require large quantities of water in the spring, and no water at all in the winter. To supply such a farm with water, a surface water system may require a large storage capacity to collect water throughout the year and release it in a short period of time. Other users have a continuous need for water, such as a power plant that requires water for cooling. To supply such a power plant with water, a surface water system only needs enough storage capacity to fill in when average stream flow is below the power plant's need.
Nevertheless, over the long term the average rate of precipitation within a watershed is the upper bound for average consumption of natural surface water from that watershed.
Natural surface water can be augmented by importing surface water from another watershed through a canal or pipeline. It can also be artificially augmented from any of the other sources listed here, however in practice the quantities are negligible. Humans can also cause surface water to be "lost" (i.e. become unusable) through pollution.
Sub-surface water
Sub-Surface water, or groundwater, is fresh water located in the pore space of soil and rocks. It is also water that is flowing within aquifers below the water table. Sometimes it is useful to make a distinction between sub-surface water that is closely associated with surface water and deep sub-surface water in an aquifer (sometimes called "fossil water").
Sub-surface water can be thought of in the same terms as surface water: inputs, outputs and storage. The critical difference is that due to its slow rate of turnover, sub-surface water storage is generally much larger compared to inputs than it is for surface water. This difference makes it easy for humans to use sub-surface water unsustainably for a long time without severe consequences. Nevertheless, over the long term the average rate of seepage above a sub-surface water source is the upper bound for average consumption of water from that source.
The natural input to sub-surface water is seepage from surface water. The natural outputs from sub-surface water are springs and seepage to the oceans.
If the surface water source is also subject to substantial evaporation, a sub-surface water source may become saline. This situation can occur naturally under endorheic bodies of water, or artificially under irrigated farmland. In coastal areas, human use of a sub-surface water source may cause the direction of seepage to ocean to reverse which can also cause soil salinization. Humans can also cause sub-surface water to be "lost" (i.e. become unusable) through pollution. Humans can increase the input to a sub-surface water source by building reservoirs or detention ponds.
Water in the ground is in sections called aquifers. Rain rolls down and comes into these. Normally an aquifer is near to the equilibrium in its water content. The water content of an aquifier normally depends on the grain sizes. This means that the rate of extraction may be limited by poor permeability.
a)What are the sources of water pollution?
Some of the principal sources of water pollution are: Geology of aquifers from which groundwater is abstracted, Industrial discharge of chemical wastes and byproducts, Discharge of poorly-treated or untreated sewage, Surface runoff containing pesticides or fertilizers, Slash and burn farming practice, which is often an element within shifting cultivation agricultural systems, Surface runoff containing spilled petroleum products, Surface runoff from construction sites, farms, or paved and other impervious surfaces e.g. silt, Discharge of contaminated and/or heated water used for industrial processes.
Acid rain caused by industrial discharge of sulphur dioxide (by burning high-sulphur fossil fuels), Excess nutrients are added (eutrophication) by runoff containing detergents or fertilizers, Underground storage tank leakage, leading to soil contamination, and hence aquifer contamination, Inappropriate disposal of various solid wastes and, on a localized scale, littering, Oil spills.
There are many causes for water pollution but two general categories exist: direct and indirect contaminant sources.
Direct sources include effluent outfalls from factories, refineries, waste treatment plants etc.. that emit fluids of varying quality directly into urban water supplies. In the United States and other countries, these practices are regulated, although this doesn't mean that pollutants can't be found in these waters.
Indirect sources include contaminants that enter the water supply from soils/groundwater systems and from the atmosphere via rain water. Soils and groundwaters contain the residue of human agricultural practices (fertilizers, pesticides, etc..) and improperly disposed of industrial wastes. Atmospheric contaminants are also derived from human practices (such as gaseous emissions from automobiles, factories and even bakeries).
Contaminants can be broadly classified into organic, inorganic, radioactive and acid/base. Examples from each class and their potential sources are too numerous to discuss here.
b)What are the effects of water pollution?
The effects of water pollution are varied. They include poisonous drinking water, poisionous food animals (due to these organisms having bioaccumulated toxins from the environment over their life spans), unbalanced river and lake ecosystems that can no longer support full biological diversity, deforestation from acid rain, and many other effects. These effects are, of course, specific to the various contaminants.
Contaminants may include organic and inorganic substances.
Some organic water pollutants are: Insecticides and herbicides, a huge range of organohalide and other chemicals, Bacteria, often is from sewage or livestock operations, Food processing waste, including pathogens, Tree and brush debris from logging operations, VOCs (Volatile organic compounds), such as industrial solvents, from improper storage, Petroleum Hydrocarbons including fuels (gasoline, diesel, jet fuels, and fuel oils) and lubricants (motor oil) from oil field operations, refineries, pipelines, retail service station's underground storage tanks, and transfer operations. Note: VOCs include gasoline-range hydrocarbons.
Some inorganic water pollutants include: Heavy metals including acid mine drainage,
Acidity caused by industrial discharges (especially sulfur dioxide from power plants), Pre-production industrial raw resin pellets (an industrial pollutant), Chemical waste as industrial by products : Fertilizers, in runoff from agriculture including nitrates and phosphates. Silt in surface runoff from construction sites, logging, slash and burn practices or land clearing sites.
The sources of water pollution typically fall into one of two categories: point-source pollution and non-point-source pollution.
The term point-source pollution refers to pollutants discharged from one discrete location or point, such as an industry or municipal wastewater treatment plant. Pollutants discharged in this way might include, for example, fecal coliform bacteria and nutrients from sewage, and toxics such as heavy metals, or synthetic organic contaminants.
The term non-point-source pollution refers to pollutants that cannot be identified as coming from one discrete location or point. Examples are oil and grease that enter the water with runoff from urban streets, nitrogen from fertilizers and pesticides, and animal wastes that wash into surface waters from agricultural lands. Natural and unknown causes of pollutants also can impact water quality and may be related to human activities. For example, highway or housing construction may help precipitate the runoff of natural pollution sources, such as sediment.
Potability of Water – Water for drinking
Regular testing is important to identify existing problems, ensure water is suitable for the intended use, ensure safe drinking water, and determine the effectiveness of a treatment system. The quality of a water source may change over time, even suddenly. Changes can go unnoticed as the water may look, smell, and taste the same.
Basic Water Potability Test packages include tests for coliform bacteria, nitrates, pH, sodium, chloride, fluoride, sulphate, iron, manganese, total dissolved solids, and hardness.
• Coliform bacteria tests indicate the presence of microorganisms in the water that are potentially harmful to human health.
• Nitrate is a common contaminant found mainly in groundwater. High nitrate concentrations can be particularly dangerous for babies under six months, since nitrate interferes with the ability of blood to carry oxygen.
• Ions such as sodium, chloride, sulphate, iron, and manganese can impart objectionable taste or odour to water.
• Excessive amounts of sulfate can have a laxative effect or cause gastrointestinal irritation.
• Fluoride is an essential micro-nutrient, but excessive amounts can cause dental problems.
• Total dissolved solids represent the amount of inorganic substances (i.e. sodium, chloride, sulphate) that are dissolved in the water. High total dissolved solids (TDS) can reduce the palatability of water.
Other tests may be appropriate if a particular contaminant is suspected in the water. For instance, groundwater sources are sometimes tested for arsenic, selenium, and uranium. Both surface and groundwater sources may also be tested for pesticide contamination. Domestic water supplies should be tested a minimum of once per year. Drinking water supplies obtained from shallow wells and surface water sources should be tested more frequently (i.e. seasonally), as they are more susceptible to contamination.
The following terms are commonly used as test parameters:
pH - represents the intensity of the acid or alkaline condition of a solution. A pH of 7 indicates neutral conditions on a scale of 0 (acidic) to 14 (alkaline).
Conductivity - measures the ability of water to conduct an electrical current, and is directly related to the total dissolved salts (ions) in the water.
Coliforms (Total) - bacteria found in faeces, soil, and vegetation, which is used to indicate the bacteriological quality of water. Coliforms indicate the possible presence of pathogenic bacteria and viruses.
Nitrate (NO3) - the most completely oxidized state of nitrogen found in water. High nitrate levels can occur naturally, but may indicate biological wastes in the water, or run-off from heavily fertilized fields. High nitrate levels reduce the ability of blood to transport oxygen to body tissues.
Total Hardness - mainly caused by the presence of calcium and magnesium in water, and is expressed as the equivalent quantity of calcium carbonate. Scale formation and excessive soap consumption are the main problems associated with hardness.
Total Dissolved Solids (TDS) - the total dissolved substances (i.e. salts and minerals) in water remaining after evaporating the water and weighing the residue.
Turbidity - represents the clarity of water. It is measured by the degree to which light is blocked because the water is muddy or cloudy.
Following are common questions and answers regarding the basic concepts of the bacterial indicator system used to monitor drinking water.
Q. Are there bacteria in properly treated potable water?
A. Yes. Drinking water regulations require that potable waters, water for human consumption, be free from human-disease-causing bacteria and specific indicator bacteria that are indicative of the presence of these pathogens. This does not mean that drinking water should be sterile. Keep in mind that not all bacteria are harmful to humans.
Q. What bacteria are harmful to the consumer?
A. There are some bacteria that have a greater probability of causing disease in humans. These bacteria are classified as pathogens. Examples of bacterial pathogens and their related diseases are Salmonella typhi (typhoid fever), Shigella dysenteriae (dysentery), and Legionella pneumophilia (Legionnaire's Disease).
There are other bacteria that will cause disease in humans, but this usually occurs in situations where the individual has been immuno-compromised. An immuno-compromised person can be very young or elderly, under antibiotic or chemotherapy treatment, undernourished, and so forth. Bacteria that cause disease in these individuals are classified as opportunistic pathogens. These bacteria take advantage of the compromised condition of the individual as an opportunity to develop disease symptoms. However, under normal or healthy conditions, the individual's own body defenses would prevent the disease from developing.
Q. How are bacteria indicative of contamination in drinking water?
A. Originally, the bacterial species and bacterial groups that are of regulatory concern were considered to be strictly associated with feces. However, it is now known that some of these bacteria can be isolated not only from human feces but also from the environment where no human fecal contamination has occurred. There is no easy or inexpensive way to differentiate the source of these bacteria when isolated from a drinking water sample. Therefore, erring on the side of safety, the regulations are based on the concept that the presence of these specific bacteria, regardless of their source, is indicative of fecal contamination from human or natural sources such as septic seepage, soils, and warm-blooded animals. This may seem unfair to the water treatment plant operator, but if the plant is operated efficiently and the distribution system is maintained properly, the probability of introducing these bacteria into the distribution system drinking water is minimal.
Q. What is coliform?
A. By definition, the term coliform group includes those bacteria that are aerobic and facultatively anaerobic, gram-negative, nonsporeforming, rod-shaped bacteria capable of fermenting lactose with gas and acid production within 48 h ± 4 h at 35°C ± 0.5°C.
Q. How does the technical definition of coliform group (previous answer) relate to a water treatment plant operator whose responsibility is the processing of water samples and interpretation of the results?
A. Admittedly, there is more information given in the definition of coliform group than is required to understand the basic concepts of the coliform indicator system. However, the descriptive terms used in the definition are necessary for classification of coliforms in relation to other bacteria and go beyond the intention of this handbook. The characteristic used for diagnostic purposes that you should be familiar with is the fermentation or utilization of lactose that produces gas bubbles and acid in the media.
Specific examples on how to interpret diagnostic results when using different types of media follow in later chapters. Also, depending on the technique used to analyze the water sample, such as multiple tube fermentation (MTF), presence-absence (PA), or membrane filter (MF), the definition for a coliform must be modified appropriately. Therefore, it is not important to memorize this definition. However, to understand why the definition must be modified when evaluating test results from the MTF technique versus the MF technique, it will be helpful to refer to this definition.
Q. What are fecal coliforms?
A. Fecal coliforms are defined in the same way as total coliforms except that fecal coliforms can ferment lactose at an elevated temperature when using standard media (44.5°C ± 0.2°C). This increase in incubation temperature inhibits the growth and lactose fermentation of the other total coliforms, which ferment lactose optimally at 35°C ± 0.5°C.
Q. Does the previous definition of fecal coliform apply to E. coli since it is a fecal coliform?
A. Yes. The only difference is in the standard media used to isolate E. coli.
Q. Why is E. coli considered to be more specific for indicating potable water contamination than the other total and fecal coliforms?
A. E. coli is more often directly associated with fecal contamination and disease outbreaks in potable waters than any of the other total or fecal coliforms. Recent developments in the technology for isolating, recovering, and identifying E. coli have made a once difficult task relatively simple, affordable, and dependable. Having a test that identifies the presence of a bacterium that is known to indicate the likelihood of fecal contamination gives the bacteriologist another technique for ensuring bacteriologically safe drinking water to the consumer.
Eutrophication is a process whereby water bodies, such as lakes, estuaries, or slow-moving streams receive excess nutrients that stimulate excessive plant growth (algae, periphyton attached algae, and nuisance plants weeds). This enhanced plant growth, often called an algal bloom, reduces dissolved oxygen in the water when dead plant material decomposes and can cause other organisms to die. Nutrients can come from many sources, such as fertilizers applied to agricultural fields, golf courses, and suburban lawns; deposition of nitrogen from the atmosphere; erosion of soil containing nutrients; and sewage treatment plant discharges. Water with a low concentration of dissolved oxygen is called hypoxic.
Eutrophication is caused by the decrease of an ecosystem with chemical nutrients, typically compounds containing nitrogen or phosphorus. It may occur on land or in the water. Eutrophication is frequently a result of nutrient pollution such as the release of sewage effluent into natural waters (rivers or coasts) although it may occur naturally in situations where nutrients accumulate (e.g. depositional environments) or where they flow into systems on an ephemeral basis (e.g. intermittent upwelling in coastal systems).
Eutrophication generally promotes excessive plant growth and decay, favors certain weedy species over others, and is likely to cause severe reductions in water quality. In aquatic environments, enhanced growth of choking aquatic vegetation or phytoplankton (that is, an algal bloom) disrupts normal functioning of the ecosystem, causing a variety of problems. Human society is impacted as well: eutrophication decreases the resource value of rivers, lakes, and estuaries such that recreation, fishing, hunting, and aesthetic enjoyment are hindered. Health-related problems can occur where eutrophic conditions interfere with drinking water treatment.
Although traditionally thought of as enrichment of aquatic systems by addition of fertilizers into lakes, bays, or other semi-enclosed waters (even slow-moving rivers), terrestrial ecosystems are subject to similarly adverse impacts. Increased content of nitrates in soil frequently leads to undesirable changes in vegetation composition and many plant species are endangered as a result of eutrophication in terrestric ecosystems, e.g. majority of orchid species in Europe. Ecosystems (like some meadows, forests and bogs that are characterized by low nutrient content and species-rich, slowly growing vegetation adapted to lower nutrient levels) are overgrown by faster growing and more competitive species-poor vegetation, like tall grasses, that can take advantage of unnaturally elevated nitrogen level and the area may be changed beyond recognition and vulnerable species may be lost. Eg. species-rich fens are overtaken by reed or reedgrass species, spectacular forest undergrowth affected by run-off from nearby fertilized field is turned into a thick nettle and bramble shrub.
Eutrophication was recognized as a pollution problem in European and North American lakes and reservoirs in the mid-20th century. Since then, it has become more widespread. Surveys showed that 54% of lakes in Asia are eutrophic; in Europe, 53%; in North America, 48%; in South America, 41%; and in Africa, 28%.
Concept of eutrophication
Eutrophication can be a natural process in lakes, as they fill in through geological time, though other lakes are known to demonstrate the reverse process, becoming less nutrient rich with time. Estuaries also tend to be naturally eutrophic because land-derived nutrients are concentrated where run-off enters the marine environment in a confined channel and mixing of relatively high nutrient fresh water with low nutrient marine water occurs.
Phosphorus is often regarded as the main culprit in cases of eutrophication in lakes subjected to point source pollution from sewage. The concentration of algae and the tropic state of lakes correspond well to phosphorus levels in water. Studies conducted in the Experimental Lakes Area in Ontario have shown a relationship between the addition of phosphorus and the rate of eutrophication. Humankind has increased the rate of phosphorus cycling on Earth by four times, mainly due to agricultural fertilizer production and application. Between 1950 and 1995, 600,000,000 tonnes of phosphorus were applied to Earth's surface, primarily on croplands. Control of point sources of phosphorus have resulted in rapid control of eutrophication, mainly due to policy changes.
Human activities can accelerate the rate at which nutrients enter ecosystems. Runoff
from agriculture and development, pollution from septic systems and sewers, and other human-related activities increase the flux of both inorganic nutrients and organic substances into terrestrial, aquatic, and coastal marine ecosystems (including coral reefs). Elevated atmospheric compounds of nitrogen can increase soil nitrogen availability.
Chemical forms of nitrogen are most often of concern with regard to eutrophication
because plants have high nitrogen requirements so that additions of nitrogen compounds stimulate plant growth (primary production). Nitrogen is not readily available in soil because N2, a gaseous form of nitrogen, is very stable and unavailable directly to higher plants. Terrestrial ecosystems rely on microbial nitrogen fixation to convert N2 into other physical forms (such as nitrates). However, there is a limit to how much nitrogen can be utilized. Ecosystems receiving more nitrogen than the plants require are called nitrogen-saturated. Saturated terrestrial ecosystems contribute both inorganic and organic nitrogen to freshwater, coastal, and marine eutrophication, where nitrogen is also typically a limiting nutrient. However, in marine environments, phosphorus may be limiting because it is leached from the soil at a much slower rate than nitrogen, which are highly insoluble.
Ecological effects
Adverse effects of eutrophication on lakes, reservoirs, rivers and coastal marine
waters
• Increased biomass of phytoplankton
• Toxic or inedible phytoplankton species
• Increases in blooms of gelatinous zooplankton
• Increased biomass of benthic and epiphytic algae
• Changes in macrophyte species composition and biomass
• Decreases in water transparency
• Taste, odor, and water treatment problems
• Dissolved oxygen depletion
• Increased incidences of fish kills
• Loss of desirable fish species
• Reductions in harvestable fish and shellfish
• Decreases in perceived aesthetic value of the water body
Many ecological effects can arise from stimulating primary production, but there are
three particularly troubling ecological impacts: decreased biodiversity, changes in species composition and dominance, and toxicity effects.
Decreased biodiversity
When an ecosystem experiences an increase in nutrients, primary producers reap the benefits first. In aquatic ecosystems, species such as algae experience a population increase (called an algal bloom). Algal blooms limit the sunlight available to bottom-dwelling organisms and cause wide swings in the amount of dissolved oxygen in the water.
Oxygen is required by all respiring plants and animals and it is replenished in daylight by photosynthesizing plants and algae. Under eutrophic conditions, dissolved oxygen greatly increases during the day, but is greatly reduced after dark by the respiring algae and by microorganisms that feed on the increasing mass of dead algae. When dissolved oxygen levels decline to hypoxic levels, fish and other marine animals suffocate. As a result, creatures such as fish, shrimp, and especially immobile bottom dwellers die off. In extreme cases, anaerobic conditions ensue, promoting growth of bacteria such as Clostridium botulinum that produces toxins deadly to birds and mammals. Zones where this occurs are known as dead zones.
Sources of high nutrient runoff
Characteristics of point and nonpoint sources of chemical inputs
Point sources
• Wastewater effluent (municipal and industrial)
• Runoff and leachate from waste disposal systems
• Runoff and infiltration from animal feedlots
• Runoff from mines, oil fields, unsewered industrial sites
• Overflows of combined storm and sanitary sewers
• Runoff from construction sites >20,000 m²
Nonpoint Sources
• Runoff from agriculture/irrigation
• Runoff from pasture and range
• Urban runoff from unsewered areas
• Septic tank leachate
• Runoff from construction sites <20,000 m²
• Runoff from abandoned mines
• Atmospheric deposition over a water surface
• Other land activities generating contaminants
Point sources are directly attributable to one influence. In point sources the nutrient waste travels directly from source to water. For example, factories that have waste discharge pipes directly leading into a water body would be classified as a point source. Point sources are relatively easy to regulate.
Nonpoint source pollution (also known as 'diffuse' or 'runoff' pollution) is that which comes from ill-defined and diffuse sources. Nonpoint sources are difficult to regulate and usually vary spatially and temporally (with season, precipitation, and other irregular events). It has been shown that nitrogen transport is correlated with various indices of human activity in watersheds, including the amount of development. Agriculture and development are activities that contribute most to nutrient loading.
There are three reasons that nonpoint sources are especially troublesome:
• Soil retention
• Runoff to surface water and leaching to groundwater
• Atmospheric deposition
Prevention and reversal
Eutrophication poses a problem not only to ecosystems, but to humans as well. Reducing eutrophication should be a key concern when considering future policy, and a sustainable solution for everyone, including farmers and ranchers, seems feasible. While eutrophication does pose problems, humans should be aware that natural runoff (which causes algal blooms in the wild) is common in ecosystems and should thus not reverse nutrient concentrations beyond normal levels.
Cleanup measures have been mostly, but not completely, successful. Finish phosphorus removal measures started in the mid-1970s and have targeted rivers and lakes polluted by industrial and municipal discharges. These efforts have had a 90% removal efficiency. Still, some targeted point sources did not show a decrease in runoff despite reduction efforts.
Impact of farming
Farming is what makes possible the production of food surpluses and settled living. It also brings about big changes in the relationships between living things and in their habitats. Farming - especially modern, intensive farming can damage the environment in many different ways.
Effect of fertilizers
Fertilisers containing plant nutrients are sprayed onto fields to make plants grow faster and boost crop yields. When it rains the nutrients may get washed down from the fields and into rivers and lakes (this is called run-off). The result is eutrophication – which can kill almost everything living in the aquatic environment. It works like this:
Effect of pesticides
Pesticides are chemicals used to kill insects, weeds and microorganisms that might damage crops. However, pesticides damage other organisms apart from those they are intended to kill - for example, depriving insect-eating birds of food. Pesticides can also enter local food chains. Organisms that ingest them cannot break them down, so they persist in their bodies. (Substances that cannot be broken down are called persistent substances: the pesticide DDT is an example.) The pesticides may then build up at ever-higher levels until they become toxic to much larger organisms.
Other impacts of farming
Agriculture can impact on the environment in many other ways. For example:
• farming takes up land, reducing habitats and wildlife
• monocultures (large amounts of one type of food) provide lots of food for
pests as well as humans
• irrigation (watering of crops) may take too much water from rivers, depriving
downstream habitats of water
• clearing land for farming may result in soil erosion, damaging ecosystems
and leaving land barren
• Intensive livestock farming produces huge amount of faeces, which may
pollute waterways
Rainwater Harvesting is the collection and storage of rain from roofs or from a surface catchment for future use. The water is generally stored in rainwater tanks or directed into mechanisms which recharge groundwater. This is appropriate in many parts of the world, such as western Britain, China, Brazil, Thailand, Sri Lanka, Germany, Australia and India, where there is enough rain for collection and conventional water resources either do not exist or are at risk of being over-used to supply a large population. Rainwater harvesting can provide lifeline water for human consumption, reduce water bills and the need to build reservoirs which may require the use of valuable land.
Traditionally, rainwater harvesting has been practised in arid and semi-arid areas, and has provided drinking water, domestic water, water for livestock, water for small irrigation and a way to replenish ground water levels. This method may have been used extensively by the Indus Valley Civilization.
Currently in China and Brazil, rooftop rainwater harvesting is being practised for use for all the above purposes. Gansu province in China and semi-arid north east Brazil have the largest rooftop rainwater harvesting projects ongoing.
Rainwater harvesting in urban areas can have manifold reasons. To provide supplemental water for the city's requirement, to increase soil moisture levels for urban greenery, to increase the ground water table through artificial recharge, to mitigate urban flooding and to improve the quality of groundwater are some of the reasons why rainwater harvesting can be adopted in cities. In urban areas of the developed world, at a household level, harvested rainwater can be used for flushing toilets and washing laundry. Indeed in hard water areas it is superior to mains water for this. It can also be used for showering or bathing. It may require treatment prior to use for drinking.
Two residences in the city of Toronto, Canada, use treated harvested rainwater for drinking water, and reuse water (i.e. treated wastewater) for all other household water applications including toilet flushing, bathing, showers, laundry, and garden irrigation (Toronto Healthy House).
In New Zealand, many houses away from the larger towns and cities routinely rely on rainwater collected from roofs as the only source of water for all household activities.
RAIN WATER HARVESTING AND ARTIFICIAL RECHARGE TO GROUND WATER
WHAT IS RAIN WATER HARVESTING :
It is the principle of collecting and using precipitation from a catchments surface. An old technology is gaining popularity in a new way. Rain water harvesting is enjoying a renaissance of sorts in the world, but it traces its history to biblical times. Extensive rain water harvesting apparatus existed 4000 years ago in the Palestine and Greece. In ancient Rome, residences were built with individual cisterns and paved courtyards to capture rain water to augment water from city's aqueducts. As early as the third millennium BC, farming communities in Baluchistan and Kutch impounded rain water and used it for irrigation dams.
ARTIFICAL RECHARGE TO GROUND WATER :
Artificial recharge to ground water is a process by which the ground water reservoir is augmented at a rate exceeding that obtaining under natural conditions or replenishment. Any man-made scheme or facility that adds water to an aquifer may be considered to be an artificial recharge system.
WHY RAIN WATER HARVESTING :
Rain water harvesting is essential because :-
Surface water is inadequate to meet our demand and we have to depend on ground water.
Due to rapid urbanization, infiltration of rain water into the sub-soil has decreased drastically and recharging of ground water has diminished.
As you read this guide, seriously consider conserving water by harvesting and managing this natural resource by artificially recharging the system. The examples covering several dozen installations successfully operating in India constructed and maintained by CGWB, provide an excellent snapshot of current systems.
RAIN WATER HARVESTING TECHNIQUES :
There are two main techniques of rain water harvestings. Storage of rainwater on surface for future use. Recharge to ground water.
The storage of rain water on surface is a traditional techniques and structures used were underground tanks, ponds, check dams, weirs etc. Recharge to ground water is a new concept of rain water harvesting and the structures generally used are:-
Pits :- Recharge pits are constructed for recharging the shallow aquifer. These are constructed 1 to 2 m, wide and to 3 m. deep which are back filled with boulders, gravels, coarse sand.
Trenches:- These are constructed when the permeable stram is available at shallow depth. Trench may be 0.5 to 1 m. wide, 1 to 1.5m. deep and 10 to 20 m. long depending up availability of water. These are back filled with filter. materials.
Dug wells:- Existing dug wells may be utilised as recharge structure and water should pass through filter media before putting into dug well.
Hand pumps :- The existing hand pumps may be used for recharging the shallow/deep aquifers, if the availability of water is limited. Water should pass through filter media before diverting it into hand pumps.
Recharge wells :- Recharge wells of 100 to 300 mm. diameter are generally constructed for recharging the deeper aquifers and water is passed through filter media to avoid choking of recharge wells.
Recharge Shafts :- For recharging the shallow aquifer which are located below clayey surface, recharge shafts of 0.5 to 3 m. diameter and 10 to 15 m. deep are constructed and back filled with boulders, gravels & coarse sand.
Lateral shafts with bore wells :- For recharging the upper as well as deeper aquifers lateral shafts of 1.5 to 2 m. wide & 10 to 30 m. long depending upon availability of water with one or two bore wells are constructed. The lateral shafts is back filled with boulders, gravels & coarse sand.
Spreading techniques :- When permeable strata starts from top then this technique is used. Spread the water in streams/Nalas by making check dams, nala bunds, cement plugs, gabion structures or a percolation pond may be constructed.
HARVESTING RAINWATER HARNESSING LIFE : A NOBLE GOAL - A COMMON RESPONSIBILITY
Ground water exploitation is inevitable is Urban areas. But the groundwater potential is getting reduced due to urbanisation resulting in over exploitation. Hence, a strategy to implement the groundwater recharge, in a major way need to be launched with concerted efforts by various Governmental and Non-Governmental Agencies and Public at large to build up the water table and make the groundwater resource, a reliable and sustainable source for supplementing water supply needs of the urban dwellers.
Recharge of groundwater through storm run off and roof top water collection, diversion and collection of run off into dry tanks, play grounds, parks and other vacant places are to be implemented by Special Village Panchayats/ Municipalities /Municipal Corporations and other Government Establishments with special efforts.
The Special Village Panchayats /Municipalities/Municipal Corporations will help the citizens and builders to adopt suitable recharge method in one's own house or building through demonstration and offering subsidies for materials and incentives, if possible.
ATTRIBUTES OF GROUNDWATER :
o There is more ground water than surface water
o Ground water is less expensive and economic resource.
o Ground water is sustainable and reliable source of water supply.
o Ground water is relatively less vulnerable to pollution
o Ground water is usually of high bacteriological purity.
o Ground water is free of pathogenic organisms.
o Ground water needs little treatment before use.
o Ground water has no turbidity and colour.
o Ground water has distinct health advantage as art alternative for lower sanitary quality surface water.
o Ground water is usually universally available.
o Ground water resource can be instantly developed and used.
o There is no conveyance losses in ground water based supplies.
o Ground water has low vulnerability to drought.
o Ground water is key to life in arid and semi-arid regions.
o Ground water is source of dry weather flow in rivers and streams.
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