Assignment 4 Class X Geography Chapter 10 The Water Resources Note: The Study Material consists of 3 parts - ○ Part I - The important highlights of the chapter. ○ Part II - The activity based on the chapter. ○ Part III - The questions based on the study material that you need to answer in your respective notebook and submit when you are back to the school. PART I HIGHLIGHTS OF THE LESSON Approximately, 71 per cent of the earth's surface is covered with water but fresh water constitutes only about 3 percent of the total water. In fact, a very small proportion of fresh water is effectively available for human use. The availability of fresh water varies over space and time. In this chapter, we shall discuss water resources in India and methods of its conservation and ​ management. WATER RESOURCES OF INDIA India accounts for about 2.45 percent of the world's surface area, 4 percent of the world's ​ water resources and about 16 percent of world's population. The total water available from precipitation in the country in a year is about 4,000 cubic km. The availability from surface water and replenishable groundwater is 1,869 cubic km. Out of this only 60 per cent can be put to beneficial uses. Thus, the total utilisable water resources in the country is only 1,122 cubic km. ​ Surface Water Resources Water that is on the earth's surface such as streams, rivers, lakes or reservoirs, etc., is known as a surface water resource . Our major sources of surface water are rivers, lakes, ponds, and tanks. Groundwater Resources Water beneath the surface of earth which saturates the pores and fractures of sand, gravel and rock formation . The total replenishable groundwater resources in the country are about 432 cubic km. The Ganga and the Brahmaputra basins have about 46 per cent of the total replenishable groundwater resources. The level of groundwater utilisation is relatively high in the river basins lying in the north western region and parts of south India. Punjab, Haryana, Rajasthan, and Tamil Nadu However, there are states like Chhattisgarh, Odisha, Kerala, etc., which utilise only a small proportion of their groundwater potentials. States like Gujarat, Uttar Pradesh, Bihar, Tripura and Maharashtra are utilising their groundwater resources at a moderate rate. Agriculture accounts for most of the Surface and groundwater utilization, it accounts for 89 percent of the surface water and 92 per cent of the groundwater utilisation. DIFFERENCE BETWEEN SURFACE WATER AND GROUND WATER Surface water 1. Water found on the surface of the earth is known as surface water. 2. Streams, rivers, lakes etc.are major sources of surface water. 3. It can be directly used for Irrigation Ground water 1. Water located below the earth's surface is known as ground water. 2. It is stored in porous soil and rocks 3. Generally is needed to be pumped out IRRIGATION Water is an important input for successful agriculture, Water may be available to crops in the natural course by rainfall or it may be supplied to the agricultural fields artificially by human efforts. The process of supplying water to crops by artificial means such as canals, wells, tube-wells, tanks, etc. from the sources I water such as rivers, tanks, ponds or underground water is called irrigation. Importance of Irrigation 1. Water is the basic input for agriculture. Cultivation of crops depends on the availability of water. Water dissolves minerals and other nutrients in the ground. The roots of the plants draw this nutritious water from the soil. 2. Water is must for commercialisation of agriculture. 3. Irrigation played a major role in the success of the Green Revolution in India. 4. Many regions like Punjab, Haryana have become leading producers of rice because of irrigation. 5. Many crops are grown in Rajasthan and other arid regions of India because of irrigation. 6.Rajasthan and parts of Gujarat need water for drinking. NEED FOR IRRIGATION The need for irrigation in India arises from the following reasons : (1) Variability in Rainfall : Rainfall in India is very uncertain, which increases the element of risk and makes crop production rather difficult. Normal rainfall is marked by its wide fluctuations of different parts as also variation from season to season and year to year in its quantity, incidence and duration. This uncertainty compels irrigation facilities to be provided. (ii) Unequal Distribution of Rainfall : In most parts of the country, 80% of the annual rainfall is received from June to September from the south-west monsoon. Saurashtra-Kutch region of Gujarat, western half of Rajasthan and parts of Punjab and Haryana are in the arid zone, where there is a constant deficiency of water. Conditions very close to aridity prevail in the rain shadow tract along the leeward side of the Western Ghats (from Karnataka to Andhra Pradesh). The inadequacy of rainfall in these areas has to be made good by irrigation. (iii) To Meet Crop Requirements and Soil Needs : Different crops require different quantities ​ of water supply. For example crops such as rice, sugarcane, jute, cotton chillies, etc., require more water and need even in areas of heavy rainfall. Sandy soils require frequent water supply than the alluvial or black soils. (iv) To Maximise Production : To get high yields and maximum production from land, and to facilitate double and triple cropping, irrigation is a must. (v) To get Efficient Use of Utilizable Flow :Many of the Indian rivers are not perennial and ​ ​ they carry insignificant flows during the rabi season. There is also a wide disparity in the water flow from year to year. The characteristic of central and southern rivers is that about 80 per cent to 90 percent of the annual runoff takes place during the 4 months of monsoon rains; the rivers are largely dry during the 8 months of the year. It is obvious, therefore, to make use of a sizable portion of the average. (vi) To Supplement Supply Even in Good Rainfall Areas : In good rainfall areas irrigation is ​ required mostly as a supplemental need to protect single crop agriculture against occasional drought. Means of Irrigation Different sources of irrigation are used in India depending upon the topography, soils, ​ rainfall, availability of surface or groundwater, nature of rivers,requirement of crops, etc. The main source of irrigation used in different parts of the country are : 1. Wells and tubewells 2. Canals 3. Tanks It is observed that the major source of irrigation is groundwater. Wells (considering all types of wells viz. dug well, shallow tube well, deep tube well) provided about 61% irrigation followed by canals with 26% at all-India level. Tanks and other sources have minor share in net irrigated areas in India. Also, there is increase in net irrigated area by wells, other sources, canals in India but there is fall in net irrigated area by tanks. Difference between Primitive and Modern methods of Irrigation PRIMITIVE METHOD 1. Primitive methods include wells, tanks and inundation canals. 2. They can be used to irrigate a small area. 3. They don't need modern machinery to build or operate. MODERN METHOD 1. These include canals, tubewells and drip irrigation. 2. They can be used to irrigate large areas. 3. They need modern machinery to build or operate. WELLS A well is a hole dug in the ground to obtain the subsoil water. Canals used to be the most important source of irrigation upto 1960's but now they have been replaced by tubewells which irrigate more than 50% of the total irrigated area of India. Wells are of three types: 1 unlined wells 2.lined wells 3. tubewells 1. Unlined wells : These are also known as Kuchha wells. These wells are dug by the farmers ​ near the field. These wells are constructed where the water table is high, i.e,15 m. These wells are not lined with bricks or stones; they are known as unlined or Kuchha wells. These types of wells are easier and cheaper to dig. SUITABLE CONDITIONS FOR WELL IRRIGATION 1. For lifting the water cheap power should be available. 2. The water table should be high. 3. The area must be in alluvial formation. 4. There should be sufficient quantities of groundwater. 2. Lined Wells A lined or pucca well is one which is lined with bricks or stones. Most of the lined and ​ unlined wells are driven by ox. Lined and unlined wells are suited to the poor Indian cultivators because of their cheapness, simplicity and their easy operation Advantages of Wells ​ ● They are the simplest and the cheapest source of irrigation ● They can be dug at any convenient place. ● They are an indispensable source of irrigation and can be used when the necessity arises. Drawbacks of wells ● They are not deep enough and may run dry. They can irrigate only a small area. ● They can be dug where the water table is high. Water contains a high percentage of minerals, which makes the water unsuitable for irrigation. ● They can water only a limited amount of land. 3. Tubewells : A tubewell is a deeper well (generally over 15 metres deep) from which water is lifted with the help of a pumping set operated by an electric motor or a diesel engine. Obviously, a ​ tubewell cannot be constructed everywhere and requires some geographical conditions favouring its installation. The main factors for installation of tubewells: (i) There should be sufficient quantity of ground water because a tube well generally irrigates 2 hectares per day against 0.2 hectares per day irrigated by an ordinary well. (ii) The water level should be nearly 15 metre.