Water Security Notes Unit 4 PDF

# Unit 4: Water Quality ## Chapter 1: Water Purification and Sewage (Wastewater) Management ### Can you recall? * What are the simple and easy methods of water purification? * How is water purification process done for big cities/villages? * What is the exact difference between water purification...

# Unit 4: Water Quality ## Chapter 1: Water Purification and Sewage (Wastewater) Management ### Can you recall? * What are the simple and easy methods of water purification? * How is water purification process done for big cities/villages? * What is the exact difference between water purification and wastewater management? ### Turbidity of Water When water flows through a river, it contains soil as well as other soluble substances. Particles of such substances are in suspended state in water (In soluble as well as partially dissolved states). Therefore, the cleanliness, clarity, transparency i.e. quality of water is reduced. This is called 'Turbidity of water'. It is a misconception that turbid rainwater is waste. But after keeping this water stagnant for some time, its turbidity decreases, or by applying the right amount of alum in the water, reduces the turbidity of the water. Therefore, don't throw away the turbid water. The 'Secchi's disc' experiment is used to measure the turbidity of water. A circular disc is used in this experiment. As shown in the figure, Secchi's disc is painted in white and black color. #### Stages of the experiment 1. First go to the middle of a lake or river basin in a boat. 2. Secchi's disc is tied to a rope and dropped into the water. 3. Slowly lower down the Secchi disc until the white and black parts disappear. Then keep the rope stable. 4. When white and black parts disappear, then prick a pin to the rope on the water surface. It is 'A'. 5. Now the rope is slowly pulled up. Pulling is stopped as soon as the white part of the disc appears and prick a pin to the rope on the water surface. It is 'B'. 6. Measure the distance between 'A' and 'B' using a meter bar. 7. The average length is measured using the following equation: Average length = (A + B) / 2 ### Always remember: Turbidity of water is measured with the help of Nephelometer. The unit of turbidity of water is NTU. NTU means Nephelometric Turbidity Units. Water turbidity level is measured by this method. ### Different stages of water purification 1. Pumping of water from a water source 2. Air mixing in water 3. Coagulation 4. Flocculation 5. Sedimentation 6. Sandstone water filtration 7. Disease Disinfection #### 1. Pumping of water from a water source Water is blocked in certain areas of the river through dams. Big water pumps for pumping water are installed there. The water is pumped out and brought to the water purification plant through a pipeline. Wire mesh is installed to prevent fishes and small plants from coming out of the tap while pumping. If the distance between the water pumping site and the purification plant is large, the water pumping center is constructed in stages. In this way, the water coming from the pumping center comes to the water purification center. #### 2. Air mixing in water River water may have a specific odour. This is because it contains unwanted gases or substances. Air is added to the water to remove it all. The principle of gravity is used to mix air in water. In this method, water is released from a height through a large pipe. When water comes down, it achieves the thinnest layer and oxygen mixes in the water. For this, a large pipe is erected at a certain height. It has circular steps built around it. When water falls through a pipe, then it falls from the steps, forming the thinnest layer and mixing oxygen in the water. Also at this time, 0.2 to 0.5 ppm chlorine is mixed in the water. This is called 'Pre-chlorination'. #### 3. Coagulation The materials used to settle down the suspended coagulate particles from water at the bottom are called coagulant. Alum is mainly used as a coagulant. Also, ferric chloride, ferrous chlorite, ferrous sulphate are used to some extent. Poly aluminium is mixed with water. Mixers are used to mix coagulant in water in equal proportions. These mixers have small blades. With a specific chemical process, coagulant and coagulative substances from water come together. Such water is sent to the collection tank. #### 4. Flocculation Flocculation is done in a large tank. The tank used for this is called Flocculation tank. Low speed rotating blades are used in Flocculation tank. Due to this rotating blades, the fine particles come together and gradually become heavier. The water is kept in this tank for thirty minutes and that water goes to the sedimentation tank. #### 5. Sedimentation In this process, the water is kept still stable for some time. The insoluble substances in the water settle to the bottom. This process is called sedimentation. With the help of this process, the turbidity of the water reduces. In the process of flocculation, suspended particles in water become heavy. Such water is brought in a large tank to stabilize it. This tank is called 'Sedimentation tank'. In this tank, water enters from upward direction. This causes clean water at the top and sludge to settle at the bottom. #### 6. Filtration- Fine sand is used to filter the water. Water is allowed to pass through a layer of sand with a thickness of 90 cm. Sometimes there are three layers of sand, thick, medium and fine, and a layer of ballast of 10 centimeters thick as well. In this process, the sedimentary water is allowed to pass through a layer of fine sand, so that very fine coagulate particles in the water as well as germs get trapped in filter. After filtering water through this layer of sand, the turbidity of water decreases to less than 0.4 NTU. The sand and ballast in filter is frequently washed with a mixture of air and water. #### 7. Disinfection Although the water from the filtration process is clean, but it is not sterile. It is necessary to destroy the germs in it. Gas is especially used to kill germs. For example, Chlorine, Ozone, Bromine. It is convenient and safe to mix mainly chlorine gas in water. This gas is dissolved in water in liquid or gaseous form. When chlorine gas is mixed with water to form hypochlorus acid, it kills germs in the water. Too much chlorine can kill aquatic viruses as well as micro-organisms. Bromine and iodine are also used for this. Water is also disinfected using ozone gas, but Ozone gas has to be produced artificially and is expensive. Ozone gas mixes with water as little as 0.8 to 1.6 PPM. Ozone gas removes colour and odour of water. #### 8. Storage of water in tanks and distribution Purified and sterilized water is stored in a large tank. At high pressure, this water is discharged into a high water supply tank. From those tanks, this water is distributed to different parts of the city. ### Equipment used for domestic water purification The water supplied from the public water supply system is pure, but everyone feels that drinking water should be pure as there is a lot of awareness about water pollution. Today, various types of water purification equipments are available in the market. They are widely used for domestic purposes. Let us take a brief look at the functioning of available water purification equipment. #### 1. The use of ultraviolet radiation Water is filtered in three stages in a water purifier where UV rays are used. In the first stage, activated carbon is used to remove water dust, fine sand or waste material. Nano silver coated carbon filters are used to remove unwanted taste and odour from water. In the last stage, germs and viruses in the water are killed using 11 watt ultraviolet lamps. This process kills only bacteria and viruses in the water. There is no effect on the basic minerals in the water. In this method, the germs killed in the water are not removed from the water. They remain in the water, that germs are more likely to become reactivate. The efficiency of this device decreases if the water is very turbid. Also, this device cannot activate without electricity. ### Observe Observe the equipment shown in the picture below. You can see these devices in different places. Collect the information, how to purify water with the help of these devices and give presentation in your class on how is the water purification process carried out? ## Chapter 2: Environmental Life Style ### Can you recall? 1. What is water quality? 2. How is water quality measured? 3. How is water quality maintained? ### Concept of Earth Overshoot Day Every year, nature adds to our resources in various ways, and man uses those resources to deplete them. Over the years, our usage of resources was less than the natural resources being added. Therefore, there were abundant natural resources. This went on for many years. Then one day, we reached when we started using all that nature has added. That is, there was neither growth nor reduction. But gradually, the situation changed, and we started using more than what nature created throughout the year. Our balance in the bank of nature began to deplete. This is called 'Earth Overshoot Day'. Let's prepare a one-year audit. We finished everything before December, which is created by nature from January to December. Now this overshoot day is shifting down from December to November, November to October, October to September, that's how we're moving. Do you know what is the Overshoot Day for 2019? That is 27 July 2019. What a horrible concept is this! This means that what nature created in 2019, we finished it on 27 July 2019 only. Man is literally plundering nature, snatching it. So did you realize our journey? The question does not end here. While this is going on, humans have also started destroying the environment. Today, land, forests, minerals, water, and even air are not safe. We are destroying biodiversity. If this continues, then we have to say that we are inviting our destruction. We have completely changed our lifestyle. When will we realize that it is harming the environment? Now, let us understand what we do from waking up in the morning up to sleeping at night and how we are destroying the environment while doing all this. ### Incidents that pollute the environment means mainly pollute water #### 1. Washing mouth in the morning The paste we use when brushing our teeth contains 2 to 5 grams of chemicals. It contains phosphate, carbonate, fragrance and multi-colour chemicals. When we wash our mouth, those chemicals are dissolved in the water, and we may not even realize that we are causing the water quality to deplete. As an environmentalist, use neem or acacia sticks, charcoal powder, salt, ash - won't it stop destruction? We are happy because we feel refreshed by using these chemicals but don't even think about what will happen to the environment. #### 2. Shaving in the morning Did you know that shaving and soap foam don't have much connection between them? While shaving, wet the face with hot water and wait a while to shave, then also, it will give clean and smooth shave. We are not aware about that. But we use soap or foam. Shaving cream or soap contains various chemicals. While doing this, we are consuming up to 2 to 5 grams of sulphate, carbonate, stearic acid, ethanol, amine, fragrance chemicals, and polluting the water. This must be stopped if the environment is to be protected. #### 3. To take a bath Two points should be considered while bathing. How much water is used for bathing? How much soap is used while bathing? The purpose of bathing is to keep the body clean. The bath can be done in a twenty-liter bucket, can be done under a shower using 50 to 100 liters of water, or can be done in a tub using 300-400 liters of water. Morally, do you agree to use too much water for bathing? In fact, many people are not getting enough water? We need to be aware that while bathing we are converting, good water into waste water. In daily life, the use of soap and shampoo has become a routine. While making soap, we use about 6 to 10 grams of edible oils, aromatic/fragrant chemicals, dye sulphates, carbonates, sodium, detergents. The body can also be cleaned by wiping the limbs with a simple wet cloth. Instead of soap, we should use Ritha, Cosmetics/Utane, Shikakai. For kids, we can use milk cream or gram flour. #### 4. Washing Clothes Different types of soap are used for washing clothes. These various soaps contain eight to ten grams of chemicals like phosphate. No one talks about the fact that it causes environmental degradation. We are not even not aware that certain chemicals shorten the life of washed clothes. The use of washing machines has become common, but we do not keep account of the amount of water we need. We don't realize that starting the machine even when the load is not full is a waste of water. How many people know that Ritha makes clothes clean? Put eight to ten pieces of Ritha in a cloth bag, and while washing clothes keep this ritha bag in the washing machine. The clothes will look clean. That bag can be reused next day. Since Ritha is environmental friendly. It also avoids environmental degradation. Shikakai, vinegar can be used in washing machines for washing clothes. #### 5. Washing utensils Earlier in Rajasthan, utensils were washed by fine sand. Water was not used for that. But now, in the new life style we invent dish washers for washing utensils. Not only this, we also started using various chemicals to clean it. This releases about 20 grams of chemicals into the water. Substances like phosphates, carbonates, silica are used for this. Coconut shells, cow dung ash, charcoal ash, or even clay can be used to clean utensils. #### 6. Toilet cleaning For this bleaching powder, acid, sulphate, chloride, phenols are widely used. It may clean the toilets, but do we take into account the environmental damage? Instead of this, make a paste by mixing vinegar and baking powder, and use it to clean toilets without any damage. Both of these things are environmental friendly. The same solution can be used to wipe the floor. #### 7. Use of cosmetics Various types of oils, face powders, nail paints, perfumes, kumkum, scented sprays, lipsticks are used as cosmetics. It contains about 18 different types of harmful chemicals. Their use causes water pollution. Therefore, five to ten grams of chemicals are added to the water every day. To prevent this, substances like mehendi, vala, ayurvedic oil, curd, turmeric, dal flour, papaya, cucumber, banana, honey, milk cream are helpful. #### 8. Rituals and Nirmalya For Pooja/Worship and other religious rituals, incense, flowers and other pooja materials are used. On the second day of worship, it becomes nirmalya. It is released into the water. This mainly leads to water pollution. Large water-insoluble idols of gods and goddesses, the artificial colours used to make those idols, and other substances (plaster of Paris) are mixed with water at the time of immersion. At the same time, hundreds of tons of Nirmalya and other hazardous substances are immersed in water. Municipalities and related organizations have to work hard for days to clean them up. Festivals and celebrations should be celebrated, but it is important to take care that the environment is not harmed while celebrating them. Now let us take an example and check how this affects on water. For this, we will take the example of Pune city. The population of Pune city is around 50 lakhs. Every day each person mixes about 50 grams of chemicals in water. This means that every day, we mix 50 lakh times 50 grams, means 2,50,000 kilo of chemicals in water. If we calculate for the year, we will realize how big a mistake we are making. No technology is effective to decompose these chemicals. If we do not want this to happen, we need to change our lifestyle. For that, here are some solutions as follow: * What's the problem of changing our lifestyle? #### 1. Separate wet and dry waste Is there a connection between waste and the water? Yes. When water falls on open waste, it rots, decomposes, spreads its stench, increases the germs and diseases. This leads to many health problems. Most of the time, people throw all the garbage in an old well in the neighbourhood to block it. Rainwater falls on it and it decomposes. Often this waste is dumped in river, streams and it flows and accumulates in lakes. This degrades the quality of the lake water. Contaminated water seeps into the soil and groundwater begins to become polluted. Contaminated surface water can be easily purified but contaminated groundwater is extremely difficult to purify. Wouldn't you be surprised if garbage was called wealth? There are some countries in the world like Sweden that buy garbage/waste from other countries. In our country, however, garbage/waste has become a problem. If this problem can be solved, it will be a big preventive measure against water pollution. #### 2. Sewage treatment and reuse of that water Today, water is viewed differently. Rainwater is known as green water. The water in the river, lake, well is called as blue water. The water that flows after bathing is called grey water and the water that comes out of the toilet is called black water. If we purify this grey water and black water, it is possible to reuse that water. The amount of wastewater generated after use is more than 75% to 80% of the amount of used water. In that case, if we purify this 80% water, then we will have that much water available. We can succeed in increasing 80% of the water supply. In many countries around the world, wastewater is treated, and reused in this way. In India, saving water in this way needs to be seriously considered. * **Example 1:** A housing society has a hundred flats. An average of five people lives in each flat. Each person uses twenty liters of water for bathing. This means that the total water requirement for this work will be (100x5x20) = 10,000 liters. Build a tank on the ground floor to collect the bathroom water of all these flats. Similarly, build a tank on the terrace. Fetch the water from the lower tank to upper tank daily with the help of a water pump. Make design in such a way that, this water will be available for cleaning all the toilets. That means the society will save 10,000 liters of water per day. To this, if we multiply by 365 days, then it needs 36,50,000 liters of water per year will be reduced. * **Example 2:** A factory needs water for production process, canteen, toilets and garden. Most of the water required for production is evaporated. The rest of the water, canteen sewage and toilet sewage can be collected and purified. It can be used for gardening. This can lead to huge water savings. * **Example 3:** 500 students live in a college hostel. These students need 10,000 liters of water per day for bathing. All the water coming out of the bathroom is collected and stored in a tank. If this water is released to the garden through a pipe from there, then many plants in the garden will be able to get water throughout the year. If orchards are planted, the organization will get a lot of income from it. * **Example 4:** The sugar factory needs a lot of water. In the factory, the juice is extracted from the cane for crushing. This juice contains 90% of water. This juice is heated to make the sugar. During this process, the water evaporates. If we cool these vapors then we can get water which will complete the need of sugar factory. This experiment has been done at 'Natural Sugar', a sugar factory in Kalamb taluka of Dharashiv district. Today the water requirement of this sugar factory is zero. * **Example 5:** In a city there are 4 to 5 wastewater treatment plants. It takes 15 liters of water every time to flush all the toilet waste to this project. If one sewage treatment plant is set up in each colony, then it will take very little water to get sewage there. Doing so will save millions of liters of water per day.. Water is mainly used for domestic, agricultural and industrial purposes. Let us now see with an example that how it can be reused for each of these tasks. ### Always remember: 1. We need to consider whether any technique we use does not endanger our resources. 2. There is a need to use environmental friendly techniques. 3. Our country needs to find the new techniques to save water. ### Collect information: Find out, if there is an innovative project for water conservation being implemented in your area, and tell everyone in the class. ### Focus on development and use of new techniques #### 1. The municipality can make money by selling wastewater. Koradi Super Thermal Power Station is located near Nagpur city for power generation. Here, it takes a lot of water to keep the machines cool. For that, there is no need of pure water. Recently, Nagpur Municipal Corporation has entered into an agreement to purify the sewage accumulated in the village and sell it to this power station. Nagpur Municipal Corporation gets compensation of around Rs 100 crore for this. As a result, there is no need to use pure river water for this purpose. This was a good reuse of water. The sewage water that used to be discharged into the river has now been stopped and this could have an impact on improving the health of the people of Nagpur. Municipalities need funding for development. #### 2. Experiments in Chhatrapati Sambhajinagar's Waluj Industrial colonies/Chhatrapati Estate Chhatrapati Sambhajinagar has a large industrial colony/Estate at Waluj. There are hundreds of factories here. In all these factories wastewater is formed. Maharashtra Industrial Development Corporation has come up with a new idea to dispose of this wastewater. All this wastewater is collected in one place in the colony. There the water is purified, and that water is made available for use in all gardens in factory or for other minor work. Not all factories can afford to set up wastewater treatment plants. This is a very good facility for them. Many cities in Maharashtra have industrial colonies/estates. If such projects are set up in every colony, the wastewater can be recycled better.. #### • Sewage management Rainwater is available for maximum of 100 days. Once this water supply is exhausted, then we have two options. The first is to use the stored rainwater and the second is to reuse once used water. Water storage is facing limitation day by day, because there is no space left to build the dam. Considering Maharashtra, underground rock structures are not suitable for water storage. So we have to use stored water as long as it can be used. But 'what is next' is the real question. In such a situation, we have to learn proper wastewater management. It is important to think about how many times we can use the same water again and again. As often as possible, the more time we have, the more we will succeed in preventing water scarcity. ### Where does the sewage come from? It is also important to look, at from where the wastewater is generated. It can be domestic or generated from factory. If it is made from domestic origin, the pollutants in it are very mild. The domestic sewage comes out from bathroom, kitchen sinks, toilets, wash basin. Drainage dirts, rotten food, vegetables, soap foam has negligible contents of chemicals or metal. If the sewage is coming out from the factory, then it may have various chemicals, metal particles, generated by lathes, griding and cutting machines, machine oils, lubricants used during manufacturing process. It has more contents of chemicals. Since the components of the above two sewages are different. The treatment processes required for them is different. ## Chapter 3: Planning of Underground Saline Water ### Can you recall? 1. How is the distribution of water on earth? 2. How is the distribution of groundwater? ### Let's think: Can saline water be made usable? ### Desalination of the saline water of the sea We are all experiencing that the groundwater level in India is going down day by day. Water quality is also changing due to increase in pumping of groundwater. In addition, the water crisis is getting worse due to change in the monsoon period. 12 states and union territories of our country have long seashore. If the sea water is purified and desalinated at various places, the water crisis can be overcome to a great extent. Desalinating seawater is very expensive, but with the advancement of technology, the cost has come down a lot. The water available due to the process of desalinating of seawater is suitable for drinking, agricultural and industrial use. Using seawater by desalinating it, is now becoming an option to address the world's water crisis. 55% of Israel's domestic water is currently sourced from saline water. In the countries like Australia, North Africa, Caribbean Islands, South Africa and the United States, the projects for the desalination of the Sea Water are going on. There are other 150 countries where almost 17000 projects are already under execution for the desalination of Sea water. The World Desalination Organization claims that this desalination project is supplying 21 billion galances of sweet water every day. Desalination projects are executing, in Tamil Nadu, Andhra Pradesh and Pondicherry in India. A similar project to supply 100 million liters of fresh water to the city of Chennai has been executed. According to Desalination Organization in India, there are over 1000 desalination projects in which their capacity of sweetening the water from 20 cubic meters to 10000 cubic meters everyday. ### Collect information Collect information about the function and process of desalination of the saline water of the sea. ### Is it financially affordable? The average cost of converting seawater into sweet water is only 10 paise per liter. This cost can be further reduced if unconventional energy sources are used. In the last few years due to public participation, the cost of desalination is decreasing. The 'Sorek Project' in Israel is the largest desalination project in the World. In this project, the cost of desalination of water is just 58 cents i.e. it takes approx. Rs. 40 to Rs.50 per 1000 liter to make the fresh water. The Ministry of Urban Development of the Government of India will build 100 smart cities in which it would be more appropriate to use sea water near the beach by desalinating it. Today, the cost of desalination is just 1/3 of the cost in the year 1990. Only the cost of desalination projects should be borne by the Central Government, State Governments, Local Self Government Institutions and Private NGOs. The projects based on pumping of ground water should not be encouraged, in 'Sagarmala' projects implemented in coastal states. ### Underground saline water Saline water may not be just in the ocean, it may be underground. It is saline. There are two main reasons for this. The first reason is that salt water from the sea and creeks seep into the shoreline. This type is found in the Konkan belt of Maharashtra. Excessive pumping of fresh water from the land on the coast creates cavities there. The saline water of the sea began to percolate to fill it. Once this process is started, it becomes difficult to use the fresh salt water for drinking and farming. This is because of the large amount of pumping of water by humans. This saline water and the fresh water do not get mixed. This is because the density of these two waters is different. They have different layers. The lower water is saline water and fresh water is found in the upper layers of groundwater due to recharge. Therefore, sweet water is pumped out first and then saline water is pumped out. In such a situation, it is possible to estimate after how much pumping the saline water will appear. The second reason for this is that the natural condition of that area. Naturally in some underground places, there are saline water reserves. ### Saline water belt in Maharashtra: There are two major Sedimentary regions in Maharashtra. The sedimentary region of Tapi river in Dhule, Jalgaon and Nandurbar District, and other sedimentary region of Purna river in Akola, Amravati and Buldhana District. The total area of this region is 6200 square kilometer. The fresh water is available in the belt having the length of 120 kilometer from Bavanbir to Chandur Bazaar, with an area of 1608 square kilometer in Buldhana District. But in the rest of the 4692 square kilometers, there is a problem of saline water. The saline belt is about 10% of the entire Purna river basin. It is on both banks of the Purna river. Pedhi, Chandrabhaga, Shahanur, Wan, Katepurna, Nalganga, Dhyanaganga, Morna and Mun are the major tributaries of the Purna river. The groundwater in this saline water belt is so salty that in historical times, salt was made from this water. Purna river originating in Betul district of Madhya Pradesh, flows from north to south in Maharashtra, and flows from east to west from Amla village in Amravati district. The electrical conductivity of the groundwater in this saline belt of this valley is above 2000 micro ohms\cm. Due to the salinity of ground water, the villages in this belt have to be supplied drinking water through pipelines outside the saline belt. Due to various reasons, schemes there are difficulties in getting water from these expensive regional, so in summer, the situation is very bad. There are a total of 894 villages in the saline belt. The details, are as follows: This region is known as the saline belt in Vidarbha. This region is not small enough in size to be ignored, it is spread over about 4693 square kilometers. The region is four times bigger than the size of Singapore country. The people of the region have been facing a saline water crisis from many years. The major problems, facing by them can be mentioned as follows: * This saline water is unsuitable for drinking. The taste of this water is so salty that it can not be held in the mouth. The salts in it are harmful to health. * The people have to bring drinking water from outside the saline belt by pipe line. This is very expensive. * This water is not suitable for irrigation. The use of this water for irrigation makes a difference in the physical and chemical properties of the soil. Therefore, even though the land is fertile, it cannot be harvested. * Rainwater is consumed as much as can be produced. So there are a lot of limitations to the cropping pattern. Double farming season is not possible. * Due to the persistent salt water crisis, a large number of people are migrating from this area. ### How the water in this belt became salty? Some experts studied why the water in this belt became so salty and given their opinion about it. According to them, about 1 lakh years ago, due to changes in the geological structure, the land in this belt was eroded by 300 to 500 meters. There the sea water penetrated in it and since there was no way to move, it settled down there. Later, soil and sand accumulated here. Alternate layers of yellow soil and sand formed and this salt water was trapped in this layer of soil and sand. Saline water is deeper at a distance of 20 to 30 meters from the surface of the soil. In the part of the saline belt of Amravati, Akola and Buldhana district, in some parts of the Purna river basin, up to 12 meters above the surface of the land, impermeable yellow soil is there. Below there is a layer of sand of about 5 meters. Again, yellow impermeable soil is there. This yellow soil does not allow water to go down. If this region is to be developed, the problem of saline water must be solved as soon as possible. ### What is a solution? According to experts, the problem of saline water can be solved as soon as possible by using the impermeable and mercury layers (apary and pary layer) found in the Purna river basin in Amravati, Akola and Buldhana districts in the saline water belt. This problem can be solved permanently without touching the rivers, if the flows of water and streams in this section are deepened up to 20 meters and widened up to 30 meters, to a length of 1000 meters and a cement dam is constructed. After the monsoon, when the dam is full, 6 lakh cubic meters of fresh water will be available in it, and excavated areas. This problem of saline water will be solved permanently. This stagnant fresh water will not mix with the saline water below, as there is again impermeable yellow soil just twenty meters on the ground. Even if mixed, this fresh water will float on salt water, due to different densities. This fresh water will be available for drinking, and agriculture. Therefore, more income can be obtained from agriculture. In this way, the development of backward saline, belt will give a boost to the dependent industries in this area and will reduce the migration from this area. ### Do you know? #### Innovative experiment of use of water in saline belt / Konkan belt: Pagoli well Saline water is found in the sea and bay areas. Therefore, wells are not dug in this area. Shallow depth farm ponds are built. But, it cannot be used for drinking water. Therefore, Pagoli well is constructed for rain water harvesting. This is a kind of tank. After the initial rainy days, the roof water is stored in these tanks and is used for drinking during rest of the days. These tanks are made of ferrocement. Jalvardhini institute has developed this technique. Ferrocement tanks have been constructed through public participation. #### Experiment in Sri Lanka Sri Lanka was hit by a tsunami in 2004. This caused the saline water of the sea to enter into the coastal villages. Sources of drinking water, land became saline. Crop growth affected. Attempts were made to improve land quality through various green manures. The best effect was the remnants of the tamarind leaf and nachani crop. The saline land was acid free. Adding acidic tamarind leaves made a good change. These two measures significantly improved soil fertility in four to six months. ### Exercise * Why is it said that saline sea water is also important? * How groundwater would have become saline in the saline water belt? * What efforts will have to be made to ensure that groundwater in the saline belt does not become saline?