E-PG PATHSHALA IN EARTH SCIENCE 1. Details of Module and its Structure Module details Subject Name Earth Science Paper Name HYDROLOGY & WATER RESOURCES Module Name/Title The World’s Water Module Id ES09: 322 Pre-requisites Before learning this module, the users should be aware of The basics of atmosphere, lithosphere, biosphere and some basic information about the characteristics of water. Objectives Objectives: The aim of this lesson is to introduce the global concept of water, its importance and distribution. The objectives of learning this module are to highlight the following: a) Importance and properties of water b) Presence of water in all spheres of the earth. c) The cyclic movements of water d) The nature of water present in various reservoirs e) The concept of Water Balance Equation f) The quality aspects of water. After attending this module, the learner will be able to explain about the distribution of global water masses, inventory of the reservoirs of water and the importance of water balance concepts on the earth. Keywords Hydrology, hydrosphere, hydrologic cycle, water quality, world’s water, natural reservoirs, water balance, water shortage. 2. Structure of the Module: Table of Contents only ( topics covered with their sub-topics) 1.0 Introduction 2.0 Water is available every where 2.1 Water exists in all Segments of the Earth 3.0 Water is a unique substance 3.1 Inherent properties of water 3.2 Characteristics of water 3.2 Typical properties of water 4.0 The Hydrosphere 4.1 Distribution of water on Earth 4.2 Inventory of World’s Water 4.3 Residence time of water in major reservoirs 4.4 Country-wise water resources 5.0 Cyclic movement of water 5.1 Natural reservoirs and conduits 6.0 The Hydrologic Cycle 6.1Components of the Hydrologic Cycle 6.2 No beginning and No end 6.3 Factors controlling Hydrologic Cycle 6.4 Source of Energy 7.0 Distribution of Water in various reservoirs 7.1 Water in the World’s Oceans 7.2 Water vapour in the Atmosphere 1 7.3 Water in Rivers and Streams 7.4 Water as Ice and Snow 7.5 Water in Lakes 7.6 Water as Soil Moisture 7.7 Groundwater as a Source 7.8 Water in Living Organisms 8.0 Water Balance Equation 9.0 Human pressure on water resources 10.0 Shortage of water 11. Quality of water 12. Importance of World’s Water 13. Global Water Management Concepts 14. Conclusion 3.0 Development Team Role Name Affiliation National Co-ordinator Subject Co-ordinators Prof. A. Balasubramanian Centre for Advanced Studies (em: [email protected]) Prof. K. N. Prakash Narasimha Dept of Earth Science Prof. B. Suresh Kumar University of Mysore, Mysore-6 Paper Co-ordinator Prof. D. Nagaraj Centre for Advanced Studies Dept of Earth Science University of Mysore, Mysore-6 Content Writer/Author(CW) Prof. A. Balasubramaian Centre for Advanced Studies Dept of Earth Science University of Mysore, Mysore-6 Content Reviewer (CR) Dr. S. Govindaiah Centre for Advanced Studies Dept of Earth Science University of Mysore, Mysore-6 Language Editor(LE) 4.0 E-text ( as per table of contents) 2 1.0 Introduction: Water is the most precious gift of mother nature. Water is used for drinking, domestic purposes like cooking, washing, gardening and cleaning operations, industrial processes and agricultural activities. Today, water has become a valuable commodity to man-kind. Water has economic value. Without water, there can be no life. It is a basic substance occurring as solid, liquid and gaseous states. Earth is probably the only planet containing plenty of water on its surface. The growing concern of environment demands more insight into the world’s water resources. Water is one of the fundamental resources on the earth. Water is essential for all other life. It plays a major role in all aspects of human life. Hydrology is the scientific study of the origin, occurrence, properties, distribution, and effects of water on the Earth’s surface, in the soil and in the underlying rocks, and also in the atmosphere. The subject of hydrology is central to several concepts in physical, chemical and biological sciences and engineering applications. It is founded upon other sciences like meteorology, geology, agricultural physics and chemistry, and botany. Understanding of the world’s water masses as a part of the global segments is necessary for managing these resources. The World’s water masses are the major reservoirs involved in hundreds of natural processes happening on the earth. These masses are fully under a dynamic condition. What is seen in a day may not be there in the next day in that form or shape or condition. The World’s water is an interesting topic to learn. 2.0 Water is available every where Water is unevenly distributed in almost all parts of the world. Due to its uneven distribution and availability it is to be managed and properly used for a long-term sustenance of life on earth. The increase in population and human activities, demand for more use of water. Shortage of water is observed in some parts of the world. Water scarcity, water pollution, drought, desertification and famine, all are serious concerns of life on earth. The challenges of managing this resource require proper water education, training and public awareness on water resource management. As a mass, water is not restricted to any one part of the earth. 2.1 Water exists in all Segments of the Earth The origin of water on earth dates back to several million years. In the early history of the Earth’s formation, around the time that the Earth’s crust began to form, severe volcanic activity released lots of volatile gasses, including water, from the underlying mantle. These volatile gasses made up the early atmosphere and oceans. It is thought that almost all of the water that we find in the oceans, lakes, streams, atmosphere, and the subsurface today was outgassed at this time. This water mass has been cycling and recycling all through these centuries. The connate water (fossil water) occurring in deep sedimentary rocks and the magmatic water emanating from the deep mantle are the major evidences for such origins and evolutions. Now, water exists in all the environmental segments of the earth. It is available a) As water vapour in the atmosphere, a) as ice caps, b) as soil water and ground water in the lithosphere, c) as surface water in the hydrosphere and d) finally, in most of the components of the biosphere. Water is the most common substance on earth. Every living thing consists of some amount of water. Fruits, vegetables and poultry contain plenty of water in them. 3.0 Water is a unique substance Water has a large number of interesting properties. These make it an ideal medium to support life. Water is called as the universal solvent due to its extraordinary ability to dissolve a large number of naturally occurring and man-made substances. Water’s melting and boiling points make it possible for all three phases to exist on our Planet Earth. Water is also lighter when it freezes, so that it floats. If water sank, then 3 the bottom of our oceans would be solid. Under such circumstances, we would only have a thin layer on the surface that would be only liquid. There would be far less global ocean currents, and many of our nutrients would be locked up inside. Survival of global life would be much more difficult, if these properties are not possessed by water. The water molecule is also polar enabling it to dissolve and transport a wide variety of chemicals and mineral substances. Water has the ability to dissolve many organic and inorganic substances in more quantity than any other liquid on earth. It has the highest heat of evaporation than any other liquid. Huge amounts of heat energy are required to evaporate even small quantities of water. Due to this high heat capacity and the presence of water on all parts of the earth, extreme fluctuations in local temperature, is prevented. Global climate is controlled due to the properties of both water and air. 3.1 Inherent properties of water Water has the following inherent properties: a) Transformation from liquid to vapour due to evaporation. b) Transformation from vapour to liquid to solid through freezing. c) Ability to flow downwards due to the action of gravity. d) Ability to flow overland on any slope. e) Ability to move due to the action of wind, when it is in vapour form. 3.2 Characteristics of water Water can be a solid, liquid or a gas. Water has very typical physical and chemical characteristics. Water has the tendency to break down into hydrogen and hydroxyl ions. This process is known as dissociation. The ability of water to conduct electrical changes is yet another property. Similarly water has the ability to conduct heat. Water has a greater heat capacity than other substances, except ammonia. Water’s surface tension is also extremely high. The specific properties of water acting on these circulation are: 1. Specific heat and latent heat 2. Pressure, capillary forces and osmotic forces 3. Density (or) specific gravity 4. Unique melting point and boiling point 5. Compressibility and Viscosity. Pure water (H2O) is clear and colorless. It is tasteless. It has no smell. At 1 atmosphere, it has a melting point of 0°C and a boiling point of 100°C. pure water has a density at 4°C of 1.00 g/cc. Water is a polar molecule and highly cohesive.