Water PDF - St. John Paul II College of Davao

ST. JOHN PAUL II COLLEGE OF DAVAO EDUCATION DEPARTMENT Physically Detached Yet Academically Attached SCP-GENELECT 2 | 1  ST. JOHN PAUL II COLLEGE OF DAVAO EDUCATION DEPARTMENT Physically Detached Y...

ST. JOHN PAUL II COLLEGE OF DAVAO EDUCATION DEPARTMENT Physically Detached Yet Academically Attached SCP-GENELECT 2 | 1  ST. JOHN PAUL II COLLEGE OF DAVAO EDUCATION DEPARTMENT Physically Detached Yet Academically Attached Week 11 Lesson Title Water and Hydrologic Cycle Learning Determine the properties of water; Outcome(s) Identify water resources; Explain how water is cycled through the hydrologic cycle. LEARNING INTENT! Terms to Ponder Water is a renewable resource that circulates continually between the atmosphere and the Earth’s surface. Hydrologic Cycle. The constant recycling process of water. Essential Content Water Water in its liquid form is the material that makes life possible on Earth. All living organisms are composed of cells that contain at least 60 percent water. Furthermore, their metabolic activities take place in a water solution. Organisms can exist only where they have access to adequate supplies of water. Water is also unique because it has remarkable physical properties. Water molecules are polar; that is, one part of the molecule is slightly positive and the other is slightly negative. Because of this, the water molecules tend to stick together, and they also have a great ability to separate other molecules from each other. Water’s ability to act as a solvent and its capacity to store heat is a direct consequence of its polar nature. These abilities make water extremely valuable for societal and industrial activities. Water dissolves and carries substances ranging from nutrients to industrial and domestic wastes. A glance at any urban sewer will quickly point out the importance of water in dissolving and transporting wastes. Because water heats and cools more slowly than most substances, it is used SCP-GENELECT 2 | 1  ST. JOHN PAUL II COLLEGE OF DAVAO EDUCATION DEPARTMENT Physically Detached Yet Academically Attached in large quantities for cooling in electric power generation plants and in other industrial processes. Water’s ability to retain heat also modifies local climatic conditions in areas near large bodies of water. These areas do not have the wide temperature-change characteristic of other areas. For most human as well as some commercial and industrial uses, the quality of the water is as important as its quantity. Water must be substantially free of dissolved salts, plant, animal waste, and bacterial contamination to be suitable for human consumption. The oceans, which cover approximately 70 percent of the Earth’s surface, contain over 97 percent of its water. However, saltwater cannot be consumed by humans or used for many industrial processes. Freshwater is free of the salt found in ocean waters. Of the freshwater found on Earth, only a tiny fraction is available for use. Unpolluted freshwater that is suitable for drinking is known as potable water. The global water supply, by comparison, is finite. Whether it’s in the form of ice, vapor, steam, or liquid, the amount of water on Earth today is about the same as the water that slaked the planet’s thirst a million years ago. Only a very thin slice of that supply is the liquid freshwater that we depend upon for drinking, washing, irrigation, manufacturing, energy, and more. The world’s total water supply is estimated at about 1.38 billion cubic kilometers (333 million cubic miles). Of this, about 97.5 percent is saltwater and about 2.5 percent is freshwater. Most of the freshwater (78 percent) is locked up in glaciers and ice caps, about 21 percent is groundwater in deep sediments or soil, and less than 1 percent is surface water. About 87 percent of surface freshwater is in lakes, 11 percent in wetlands, and 2 percent in rivers. Some areas of the world have abundant freshwater resources, while others have few. In addition, demand is increasing for freshwater for industrial, agricultural, and personal needs. Shortages of potable freshwater throughout the world can also be directly attributed to human abuse in the form of pollution. Water pollution has negatively affected water supplies throughout the world. In many parts of the developing world, safe drinking water is scarce. The World Health Organization estimates that about 25 percent of the world’s people do not have access to safe drinking water. Even in the economically advanced regions of the world, water quality is a major issue. According to the United Nations Environment Programme, 5 million to 10 million deaths occur each year from water-related diseases. The illnesses include cholera, SCP-GENELECT 2 | 1  ST. JOHN PAUL II COLLEGE OF DAVAO EDUCATION DEPARTMENT Physically Detached Yet Academically Attached malaria, dengue fever, and dysentery. The United Nations also reports that these illnesses have been increasing over the past decade and that without large economic investments in safe drinking-water supplies, the rate of increase will continue. Water, used by households, agriculture, and industry, is clearly the most important good provided by freshwater systems. Increasing scarcity, competition, and arguments over water in the first quarter of the twenty-first century could dramatically change the way we value and use water and the way we mobilize and manage water resources. Furthermore, changes in the amount of rain from year to year result in periodic droughts for some areas and devastating floods for others. However, rainfall is needed to regenerate freshwater and, therefore, is an important link in the cycling of water. SCP-GENELECT 2 | 1  ST. JOHN PAUL II COLLEGE OF DAVAO EDUCATION DEPARTMENT Physically Detached Yet Academically Attached The Hydrologic Cycle All water is locked into a constant recycling process called the hydrologic cycle. Two important processes involved in the cycle are the evaporation and condensation of water. Evaporation involves adding energy to molecules of a liquid so that it becomes a gas in which the molecules are farther apart. Condensation is the reverse process in which molecules of gas give up energy, get closer together, and become a liquid. Solar energy provides the energy that causes water to evaporate from the ocean surface, the soil, bodies of fresh water, and the surfaces of plants. The water evaporated from plants comes from two different sources. Some is water that has fallen on plants as rain, dew, or snow. In addition, plants take up water from the soil and transport it to the leaves, where it evaporates. This process is known as evapotranspiration SCP-GENELECT 2 | 1  ST. JOHN PAUL II COLLEGE OF DAVAO EDUCATION DEPARTMENT Physically Detached Yet Academically Attached The water vapor in the air moves across the surface of the Earth as the atmosphere circulates. As warm, moist air cools, water droplets form and fall to the land as precipitation. Although some precipitation may simply stay on the surface until it evaporates, most will either sink into the soil or flow downhill or enter streams and rivers, which eventually return the water to the ocean. Surface water that moves across the surface of the land and enters streams and rivers is known as runoff. Water that enters the soil and is not picked up by plant roots moves slowly downward through the spaces in the soil and subsurface material until it reaches an impervious layer of rock. The water that fills the spaces in the substrate is called groundwater. It may be stored for long periods in underground reservoirs. The porous layer that becomes saturated with water is called an aquifer. An aquifer is an underground layer of gravel, sand, or permeable rock that holds groundwater that can be extracted by wells. There are three basic kinds of aquifers: unconfined, semi- confined, and confined. An unconfined aquifer usually occurs near the land’s surface where water enters the aquifer from the land above it. The top of the layer saturated with water is called the water table. The lower boundary of the aquifer is an impervious layer of clay or rock that does not allow water to pass through it. Unconfined aquifers are replenished (recharged) primarily by rain that falls on the ground directly above the aquifer and infiltrates the layers below. The water in such aquifers is at atmospheric pressure and flows in the direction of the water table’s slope, which may or may not be similar to the surface of the land above it. Above the water table and below the land surface is a layer known as the vadose zone (also known as the unsaturated zone or zone of aeration) that is not saturated with water. A confined aquifer is bounded on both the top and bottom by layers that are impervious to water and is saturated with water under greater-than-atmospheric pressure. An impervious confining layer is called an aquiclude. If water can pass in and out of the confining layer, the layer is called an aquitard and the aquifer is known as a semiconfined aquifer. Both confined and semi-confined aquifers are primarily replenished by rain and surface water from a recharge zone (the area where water is added to the aquifer) that may be many kilometers from where the aquifer is tapped for use. SCP-GENELECT 2 | 1  ST. JOHN PAUL II COLLEGE OF DAVAO EDUCATION DEPARTMENT Physically Detached Yet Academically Attached If the recharge area is at a higher elevation than the place where an aquifer is tapped, water will flow up the pipe until it reaches the same elevation as the recharge area. Such wells are called artesian wells. If the recharge zone is above the elevation of the top of the well pipe, it is called a flowing artesian well because water will flow from the pipe. The nature of the substrate in the aquifer influences the amount of water the aquifer can hold and the rate at which water moves through it. Porosity is a measure of the size and number of the spaces in the substrate. The greater the porosity, the more water it can contain. The rate at which water moves through an aquifer is determined by the size of the pores, the degree to which they are connected, and any cracks or channels present in the substrate. The rate at which the water moves through the aquifer determines how rapidly water can be pumped from a well per minute. SCP-GENELECT 2 | 1  ST. JOHN PAUL II COLLEGE OF DAVAO EDUCATION DEPARTMENT Physically Detached Yet Academically Attached Content References/Search Indicator: Enger, E., & Smith, B. (2016). Environmental science: A study of interrelationships, 14th Ed. McGraw-Hill Education. SCP-GENELECT 2 | 1  ST. JOHN PAUL II COLLEGE OF DAVAO EDUCATION DEPARTMENT Physically Detached Yet Academically Attached SCP-GENELECT 2 | 1