Course: Water Management in Horticultural Crops 2(1+1), 1st year, 2nd semester WATER RESOURCES IN INDIA Dr. Vikas Gupta, College of Horticulture, Rehli Importance Of Water In Plants And Soil: (1) All living things need water to stay alive and plants are also living things. (2) Plants need much more water than many other living things because plants use much more water to maintain their turgor, which is water pressure inside the cells that make up the plant's skeleton. (3) Water is used for transpiration carrier of nutrients from the soil to green plant tissues. (4) In photosynthesis process plant uses light, water and carbon dioxide to create energy and food. Plants can synthesis food through photosynthesis only in the presence of water in their system. (5) Without enough water in the cells, the plants droop, so water helps a plant stand. (6) Water carries the dissolved sugar and other nutrients throughout the plant and its cells. (7) Water saves the plant from dehydrating. It is also used to transport the nutrients. (8) Soil water is the medium from which all plant nutrients are assimilated by plants. (9) Water plays vital role in the different biological, physical and chemical reactions in the plants as well as soil. (10) Water is also essential for the life of macro and micro fauna of the soil. (11) All the anabolic and catabolic activities of plants only occur in the medium of water. (12) Agronomic activities like land preparation, ploughing, leveling, sowing, hoeing etc. conveniently possible only under sufficient soil moisture condition. So, it can be concluded that all type activities in plant and soil only possible in the presence of water. Main Water Resources In India: The average rainfall in India is about 4,000 billion cubic metres, but most of India's rainfall comes over a 4-month period – June through September. Furthermore, the rain across the very large nation is not uniform, the east and north gets most of the rain, while the west and south get less. India also sees years of excess monsoons and floods, followed by below average or late monsoons with droughts. This geographical and time variance in availability of natural water versus the year round demand for irrigation, drinking and industrial water creates a demand-supply gap, that has been worsening with India's rising population. In the country, there are about 10,360 rivers and their tributaries longer than 1.6 km each. The mean annual flow in all the river basins in India is estimated to be 1,869 cubic km. The rivers of India play an important role in the lives of the people. They provide potable water, cheap transportation, electricity, and the livelihood for many people nationwide. This easily explains why nearly all the major cities of India are located by the banks of rivers. Seven major rivers along with their numerous tributaries make up the river system of India. The largest basin system of the rivers pour their waters into the Bay of Bengal; however, some of the rivers whose courses take them through the western part of the country and towards the east of the state of Himachal Pradesh empty into the Arabian Sea. Parts of Ladakh, northern parts of the Aravalli range and the arid parts of the Thar Desert have inland drainage. Himalayan glaciers in the Indian subcontinent are broadly divided into the three river basins, namely the Indus, Ganga and Brahmaputra. The Indus basin has the largest number of glaciers (3500), whereas the Ganga and Brahmaputra basins contain about 1000 and 660 glaciers, respectively. Ganga is the largest river system in India. There are many sources of surface water like lakes, ponds, canals, tube wells, and tanks etc. The main source of irrigation in India is tube-wells which provide 46% of water for irrigation. Other sources include canals (24%), other wells (16%), tanks (3%) and other sources (11%). (I) Tubewells & Wells: Well and Tube Well irrigation is the most popular irrigation system in India. The first tube well was dug in 1930 in Uttar Pradesh. Today there are more than 50 lakh tube wells operating in different parts of India. It has contributed substantially for the success of Green Revolution in India. Tube wells are the wells from which we pump out the water through a handle present on it. Tube wells can trap water from deep strata. Dug wells are the wells from which we pull the water through a bucket or anything by which can hold the water. In dug well water is collected from water bearing strata. Uttar Pradesh has the largest area irrigated by tube wells followed by Punjab, Rajasthan and Bihar. (II)Canals: Irrigation canals are the main waterways that bring irrigation water from a water source to the areas to be irrigated. An open canal, channel, or ditch, is an open waterway whose purpose is to carry water from one place to another. Channels and canals refer to main waterways supplying water to one or more farms. Canal irrigation is one of the most important form of irrigation in India. This is because of presence of rivers which feed the canals with water. Most of the canals in India today are perennial. The net area under canal irrigation is about 15.8 million hectares. The main canal irrigated areas are in the northern plains of India where Uttar Pradesh, Punjab, Haryana, Rajasthan and Bihar account for about 60 per cent of the canal irrigated area of the country. (III) Lakes and Ponds: Lake is a large body of water that is entirely surrounded by land. Lake water can be fresh or more rarely salty or saline. Lakes plays important role in agriculture as well as in Indian economy. Lakes are of great value to human beings. It helps to regulate the flow of a river. During heavy rainfall, it prevents flooding and during the dry season, it helps to maintain an even flow of water. It also helps to replenish groundwater. Kolleru Lake is one of the largest freshwater lakes in India located in state of Andhra Pradesh and forms the largest shallow freshwater lake in Asia. Indian remote sensing satellite found that approximately 42% of the 245 km2 lake was occupied by aquaculture, while agriculture had encroached another 8.5%. The agricultural encroachments were mostly rice paddies. (IV) Tanks: Tanks are part of ancient harvesting and preserving rainwater for use in agriculture, drinking and sometimes for rituals and bathing. Its use is critical in southern parts where there is no perennial rain. Tank irrigation is popular in the peninsular plateau area where Andhra Pradesh and Tamil Nadu are the leading states. Andhra Pradesh is the largest state of tank irrigation where 727 thousand hectares are irrigated by tanks. Andhra Pradesh has about 28.8 per cent of tank irrigated area of India..