Water Resources

The term 'water resource' refers to any of the entire range of natural waters that occur on the earth and are of potential use to living beings.

(i) There is a need to adopt different means of irrigation because of uncertainty of rainfall, uneven distribution of rainfall, crop requirements, nature of the soil, effective utilisation of river water and to maximise production.

(ii) There is a need for conserving water for the following reasons-

1. The over exploitation of ground water often results in the lowering of water table.
2. The loss of vegetation causes drought and reduction of rainfall and lowering of the water table.
3. Irrigation utilises more than 90% of the total freshwater.
4. The increase in population results in water scarcity.
5. Our water resources are polluted and their water can hardly be used without adequate treatment.

(iii) Man is responsible for water crisis in India because due to increase in population, irrigation and industrialisation, the demand for water has risen. This has led to a decline in groundwater levels in various parts of the country.

(i) Rainwater harvesting is the process of increasing the recharge of groundwater by capturing and storing rainwater locally in sub-surface water reservoirs.

(ii) The main objectives of rainwater harvesting are the following:

1. Meeting the ever increasing demand for water.
2. Reducing the run-off which chokes drains.
3. Avoiding the flooding of roads.
4. Augmenting the groundwater storage and raise the water table.
5. Reducing groundwater pollution.
6. Improving the quality of groundwater.
7. Reducing the soil erosion.
8. Supplementing domestic water requirement during summer and drought.

Irrigation refers to the process of watering of agricultural plants through artificial means from wells, tanks, tube wells, canals, etc.

Water scarcity is the lack of sufficient available water resources to meet the demands of water usage within a region.

Growing population, over-exploitation and unequal distribution of water among social groups are the main causes of water scarcity in India.

(i) Inundation canals are being converted to perennial canals because inundation canals get supply of water only when the rivers are in flood while perennial canals can draw water throughout the year and irrigate large areas.

(ii) Tank irrigation is preferred over other means of irrigation in Peninsular India because-

1. The rivers of Deccan are mainly dependent on the rainwater.
2. Many streams become torrential during the rainy season but dry up when the rain ceases.
3. The hard rocks in the area do not absorb waters, wells cannot be made there.
4. The terrain is uneven with many natural depressions where tanks can be easily built.

(iii) Groundwater reserves are depleting at a fast rate due to increase in population, irrigation and industrialisation, the demand for water has risen. This has led to a decline in groundwater level in various parts of the country.

(i) Traditional methods of irrigation means to supply water to the plant zone by pumped water from surface or subsurface sources like ponds, rivers, channels or groundwater through earthen channels or pipes with gravitational force.

(ii) Two conventional methods of irrigation are wells and tanks.

Two drawbacks of conventional methods of irrigation are-

1. A large quantity of water is not properly utilised.
2. The fields situated in low areas always get excess water causing prolonged water logging.

Two advantages of well irrigation are-

1. Wells can be dug at a very low cost which is well within the means of poor farmers.
2. By the use of pumps and tubewells, water can be lifted even from great depths.

Two disadvantages of well irrigation are-

1. Wells depend on underground water resources whose distribution varies from region to region.
2. The traditional wells dry up due to over withdrawal of the ground water and lowering of the water table.

(i) Well irrigation is confined mainly to the alluvial plains as owing to the soft nature of the soil, wells can be easily dug and the yield of crops from the land after irrigation is considerably high.

(ii) In Tamil Nadu, nearly one-third of the net irrigated area is under canal irrigation because Tamil Nadu receives rainfall during the winter season while summer season remains dry. Thus, irrigation is needed in summer to make up the lack of rainfall.

(iii) Drip irrigation reduces loss of water through evaporation as this system consists of perforated pipes that are placed between rows of crops or buried along their root lines and give water directly on to the crops.

(i) Two states where well irrigation is practised are Punjab and Uttar Pradesh.

(ii) One advantage of tubewell irrigation is that it brings up clean water.
One disadvantage of tubewell irrigation is that it is useless if the water is brackish.

Two types of canals are-

1. Inundation canals
2. Perennial canals

Two states where perennial canals are widely used are Uttar Pradesh and Madhya Pradesh.

Persian wheel method is a partly submerged vertical wheel with buckets attached to the rim. As the wheel is turned by draught animals rotating a geared horizontal wheel, the buckets are filled and emptied into a trough above, which carries the water to crop-sown fields.

(i) Canals make the soil infertile because in canal irrigation, where water table is a few feet below the ground, the alkaline salts come to the surface, mix with the soil and make it unproductive.

(ii) Tubewell irrigation is quite expensive as it requires continuous supply of electricity.

(iii) Excessive accumulation of salts make the soils unsuitable for cultivation because when salt concentrations in the soil are high, the movement of water from the soil to the root is slowed down. When the salt concentrations in the soil are higher than inside the root cells, the soil will draw water from the root, and the plant will wilt and die. Hence, the soil becomes unsuitable for cultivation.

(i) The following conditions favour the development of canal irrigation in Punjab:

1. Presence of rivers (like Sutlej, Beas, and Ravi)
2. Gentle slope of land
3. Extensive farmlands
4. Low rainfall
5. Alluvial soil

(ii) Two disadvantages of Canal irrigation (perennial) are as follows:

1. In areas where perennial unlined canals flow at ground level and between raised high banks, the water table may rise excessively, leading to waterlogging and swamp formation, rendering the soil uncultivable.
2. Waterlogging reduces the soil's ability to absorb water, so even slight excess rainfall can flood the land, damaging crops, homes, and stored goods due to poor drainage.

The groundwater levels are dropping rapidly in India due to the following reasons:

1. The over-exploitation of groundwater is mainly responsible for the lowering of water table.
2. Excessive extraction for agriculture, especially through borewells, has led to a significant decline in the water table.
3. This issue is further worsened by a reduction in rainfall, which limits the natural recharge of groundwater.
4. Industrial use and the growing demand from a rising population also contribute to this rapid depletion.

Groundwater can be recharged by allowing rainwater to seep into the ground. One effective method is rainwater harvesting, where rainwater is collected and directed into the soil through pits, trenches, or wells, helping to refill underground water reserves.

(i) Many farmers in India still use wells because wells can be dug at a very low cost and the oxen which are kept for ploughing the land can be utilised for drawing water from the well.

(ii) There is very little recharge of groundwater because rapid urbanisation has reduced open spaces and natural surfaces, preventing rainwater from seeping into the ground and replenishing the water table.

(iii) Tubewells are important in Punjab because the state has fertile alluvial soil and a high demand for irrigation to support intensive farming, especially of wheat and rice. The presence of abundant groundwater makes tubewells a reliable source of irrigation.

(i) Watershed management refers to the efficient management and conservation of both the surface and groundwater resources. It includes the prevention of run-off as well as storage and recharge of groundwater by various methods like percolation pits, recharge wells, borewells, dugwells etc.

(ii) Watershed management is beneficial for farmers as it is aimed at conserving both soil and water. Since both soil and water are indispensible for the cultivation of crops, watershed management helps farmers to maximize their crop production and income.

Drip irrigation is the most advanced and efficient method of irrigation. This system consists of perforated pipes that are placed between rows of crops or buried along their root lines and give water directly on to the crops.

It is useful as it reduces evaporation drastically and irrigation water is conserved. It also allows the grower to customise an irrigation programme most beneficial to each crop.

We need to conserve water for the following reasons-

1. The over exploitation of ground water often results in the lowering of water table.
2. The loss of vegetation causes drought and reduction of rainfall and lowering of the water table.
3. Irrigation utilises more than 90% of the total freshwater.
4. The increase in population results in water scarcity.
5. Our water resources are polluted and their water can hardly be used without adequate treatment.

(i) Modern means of irrigation are gaining popularity because of the following reasons-

1. No loss of water due to seepage or evaporation
2. Conserve water
3. Prevent soil erosion
4. Suitable for areas where the rainfall is low
5. High efficiency

(ii) Sprinkler irrigation helps in conserving water as water is sprayed directly to the required plants so there is no loss of water through seepage or evaporation.

(iii) Spray irrigation is quite expensive because it requires complex machinery.

Furrow irrigation is a type of flood irrigation in which the water poured on the field is directed to flow through narrow channels dug between the rows of crops, instead of evenly distributing the water throughout the whole field. The furrows must have equal dimensions, in order to guarantee that the water is distributed evenly.

The advantage of furrow irrigation is lower initial investment of equipment and lower pumping costs per acre-inch of water pumped.

The advantages of Drip irrigation are as follows:

1. It is the most advanced and efficient method of irrigation.
2. This system consists of perforated pipes that are placed between rows of crops or buried along their root lines and give water directly on to the crops.
3. As a result, evaporation is drastically reduced and irrigation water is conserved.
4. Drip irrigation allows the grower to customise an irrigation programme most beneficial to each crop.

One of the traditional methods of irrigation include Well Irrigation.

A well is a small hole dug in the surface of the earth to obtain water from the water table for irrigation and other purposes. Wells are usually of two types: Lined wells (manmade), and Unlined wells (formed by different natural phenomena).

Well irrigation is a cheap, simple and dependable source of irrigation. It is practised in areas where plenty of groundwater is available and the depth of the water table does not exceed 15m.

(i) Loss of water due to evaporation is highest in tanks due to large area coverage and its shallow depth.

(ii) Many cities in India have banned the construction of tubewells because excessive extraction of groundwater lowers the water table, leading to water scarcity. It can also cause the ground to sink which can damage buildings and infrastructure.

(iii) Rabi crops are grown in areas with irrigation facilities because they are sown in winter when rainfall is low. These crops, like wheat and barley, need a regular water supply, which is provided through irrigation.

If given a choice, I would use the drip irrigation method to irrigate my farm. This is due to the following reasons:

1. It is one of the most advanced and efficient method of irrigation.
2. The system uses perforated pipes placed between crop rows or along root lines, delivering water directly to the plant roots.
3. This reduces evaporation significantly and helps conserve irrigation water.
4. Drip irrigation allows farmers to customise irrigation programme according to the specific needs of each crop, improving yield and resource efficiency.

An underground stream saturated with water that is transmitted readily on to the surface.

Using bottled drinking water only

Both A and R are true and R is the correct explanation of A.

Explanation — Increase in population means an increase in the demand for water. This in turn leads to decline in groundwater levels in many states.

All of the above.

Overhead irrigation

the Deccan Plateau

Both A and R are true and R is the correct explanation of A.

Explanation — Rainfall in India occurs in short spells of high intensity due to which most of the rain falling on the surface tends to flow away rapidly, leaving very little for the recharge of groundwater. This in turn causes Cherrapunji to suffer from acute shortage of drinking water.

Furrow irrigation

(i), (ii), (iii), (iv)

Both A and R are true and R is the correct explanation of A.

Explanation — Paved surfaces are relatively free of bacteriological contamination due to lack of direct contact with soil and organic matter, limited microbial activity, and less exposure to pollutants.

Perennial canals

Mizoram

Both A and R are true but R does not explain A.

Explanation — Farmers make use of irrigation canals and tanks, as well as rely on rainfall. However, they are two separate facts.

Sprinkler irrigation

India is known to be a land of rivers with 12 major rivers and 46 medium rivers. Many of these rivers are perennial and some of them are seasonal. The annual rainfall in India is 1,170 mm which is higher as compared to the world average of 800 mm. Despite this, acute shortage of water in some states is due to the following reasons:

1. Uneven distribution — Water resources are not distributed evenly across the country. The monsoons rains are also spread unevenly. The result is that some states are devastated with floods while others face severe drought at the same time.
2. Population growth — India has one of the world's largest populations, and the demand for water is increasing due to rapid urbanization, industrialization, and agricultural growth. India constitutes around 17% of the world's population but has only 4% of the world's freshwater resources.
3. Poor water management — Inefficient management of water resources, lack of proper infrastructure, and poor governance are also contributing to the water shortage in some states.
4. Pollution — Pollution of water bodies, such as rivers, lakes, and groundwater, is reducing the availability of clean water for domestic, agricultural, and industrial use.

To check this scarcity of water, we need to take quick steps to make proper policies and laws and adopt effective measures for water conservation. This can be done by using rainwater harvesting. It is the process of increasing the recharge of groundwater by capturing and storing rainwater locally in sub-surface water reservoirs.

Various kinds of recharge structures are possible which can ensure that rainwater percolates in the ground instead of draining away from the surface Some of these are:

1. Borewells and Dugwells — They are used to raise the underground water table.
2. Recharge Pit — They are excavated into the ground lined with a brick or stone wall with openings at regular intervals.
3. Percolation Pits — It is a bored hole of up to 30 cm diameter drilled in the ground to a depth of 3 to 10 m.
4. Recharge Trenches — They are excavated on the ground and refilled with porous media like pebbles, boulder or brick bats to harvest the surface runoff.
5. Permeable Surfaces — For example, a patch of grass is used to retain a large proportion of the rainwater falling on it, yielding only 10-15 per cent as runoff.
6. Porous tiles — They can be used on pavements and footpaths.

The most suitable traditional water conservation system for my city would be Ahar Pynes.

My city is located on the Indo-Gangetic plains in North India, a region known for its fertile soil and agriculture-based economy. This area receives seasonal rainfall and has several rivers and natural drainage channels. The Ahar Pynes system is ideal here because it helps in managing excess rainwater during the monsoon by diverting it through pynes (channels) into ahars (reservoirs), preventing flooding and soil erosion. It also ensures water is stored for irrigation during dry periods, supporting sustainable farming and groundwater recharge.

Yes, I have observed Chand Baori in Rajasthan. It is a stunning architectural marvel and one of India's deepest and largest stepwells. It features a square shape with multiple tiers of steps arranged in a precise geometrical pattern. It has 3,500 narrow steps leading down to a depth of about 20 meters (65 feet). The steps are constructed without mortar or iron clips, relying on a precise design for stability. It is strategically positioned to capture and store rainwater, ensuring a reliable water supply for the surrounding community, especially during dry periods.