Chapter 7 Notes PDF

Chapter 7 notes Value of water: The UN estimates that approximately 3.5 million people die each year from contaminated water, and that one-fifth of the world’s population suffers from water scarcity. Droughts and shortages are projected( expected , ‫( توقع‬to become mor...

Chapter 7 notes Value of water: The UN estimates that approximately 3.5 million people die each year from contaminated water, and that one-fifth of the world’s population suffers from water scarcity. Droughts and shortages are projected( expected , ‫( توقع‬to become more frequent, which will make water scarcity more common. Unavailable freshwater is held in salt water, frozen glaciers, suspended in the air, and held in the bodies of living organisms. Daily water use includes water for drinking, cooking, bathing, and toilet flushing. Embedded water is a concept that accounts for the water that is used to produce goods we consume. Pollution from human activities and climate change contribute to the decline in freshwater biodiversity and water supply. Where is water found on earth?: Reservoirs : Places where water spends time Reservoirs make up the Earth's hydrosphere: a closed system that recycles water molecules again and again between reservoirs. Residence time: The amount of time a molecule spends in a particular reservoir The atmosphere holds about 0.001% of Earth's total water supply, with an average residence time of 10 days. The ocean holds about 97% of Earth's water supply, with an average residence time of 3,000 years. Almost 80% of Earth's fresh water is frozen. Groundwater :is the largest reservoir of liquid fresh water and feeds into the oceans, lakes, and rivers. Aquifer :When precipitation falls to the ground, some water drains down and accumulates in subsurface areas of rocks or sediments. The top of the groundwater reservoir is called the water table, which marks the boundary between the saturated and unsaturated zones  How Does Fresh Water Support Life?: Groundwater-dependent ecosystems: are communities of organisms that require groundwater to meet at least some of their water needs. Surface water : Freshwater sources, such as rivers, streams, lakes, and wetlands Lakes and ponds: form when water fills areas cut out by slowly retreating glaciers (masses of ice that flow over land surfaces), by volcanic eruptions Flowing water systems, such as rivers and streams, are lotic ecosystems: which have different habitats created by variations in their flow Wetlands: are areas where the ground is seasonally or permanently saturated with water 1. Forested wetlands are called swamps. 2. Wetlands dominated by grasses and cattails are called marshes. 3. Estuaries are wetlands where fresh water meets salt water and are among the most biologically rich areas on Earth due to abundant light and nutrient-rich sediments. How do humans impact fresh water ? : Humans impact freshwater systems in two broad ways: by withdrawing or diverting water, and by adding pollutants. Humans use more freshwater for crop irrigation than for any other purpose  Groundwater is considered a renewable resource, but the replacement, or recharge, time is over 10,000 years. Human use far exceeds resupply. Aquifers sealed off by surrounding rock can no longer recharge from precipitation and contain “fossil water” with a residence of millions of years. -These aquifers are non-renewable, so withdrawals from them are considered water mining. Groundwater depletion shrinks rivers and wetlands. Which can also lead to saltwater intrusion from the ocean, contaminating freshwater wells. Excessive groundwater withdrawals can also cause subsidence, a sinking or collapse of the ground surface. Which then permanently reduces the aquifers ability to store water Impervious surfaces, such as pavement and rooftops, divert water to storm drains and nearby waterways instead of to soil surfaces. Runoff increases the peak flows of rivers, causing flooding, erosion of the riverbanks, and the removal of fish eggs from streambeds. It also prevents water from draining into the soil, reducing groundwater recharge. Dams, reservoirs, canals, and pipelines divert water from where it naturally flows. 1. cause increased rates of freshwater evaporation, decreased water flow, and act as barriers to migrating fish. 2. also prevent nutrient-rich sediment from traveling downstream, forcing it to accumulate in the reservoir.  Around 2000 BCE, the Egyptians invented the first canal systems to use water from the Nile River for irrigation. Man-made canals and channels contribute to the loss of wetlands by preventing seasonal flooding and lowering the water table Diverting surface water upstream reduces the amount of available water downstream. Water pollution : A point source of freshwater pollution: is a clearly identifiable source of contamination, such as a drainpipe, channel, ditch, or well. A nonpoint source: is a broad or diffuse source of pollution that is less easily identified, such as agriculture, residential runoff, or airborne pollutants from industry. The most common type of water pollution is sediment pollution: when large amounts of loose soil are swept into waterways by erosion from agriculture, forestry, and urban development. Sediment pollution causes turbid (cloudy) waters, which reduces light penetration, restricts plant growth, and reduces nutrient levels. A common chemical pollutant is agricultural fertilizer, which causes eutrophication. -Fertilizers increase nutrient availability, causing rapid phytoplankton and algae growth, death and decomposition Can we improve the access to fresh water : A sustainable development goal of the United Nations is water security, defined as reliable access to safe and affordable water. A water shortage occurs where a large percentage of available water has been withdrawn for human use A drought is a period of low precipitation and high evaporation rates, which can lead to water shortages. Megadroughts can last decades Droughts can occur in temperate climates as well as arid, desert environments. Conservation is the first way to manage a water shortage :  o Conservation within cities includes landscaping measures, such as not watering lawns and planting drought-tolerant plants. o Conservation methods around agriculture include infrastructure improvements, such as repairing pipes and conduits to reduce water waste. o New irrigation technology and smart systems release water in small targeted amounts only when needed. o Farmers can also switch to crops that require less water. o Another effective conservation measure is water recycling, which takes residential water, treats it, then uses it for agriculture, industry, or landscape irrigation. Water scarcity : Dams are often built to provide a constant water source, but 25% of the world’s population experiences decreases in water availability because of dams Privatizing water, where a private company owns and manages the water supply, can lead to high prices and declining water quality. -Water privatization has also led to additional water scarcity in regions already suffering severe water shortages. Harvesting rainwater and desalination, removing salt from seawater to create fresh water, are possible solutions to water scarcity. Many countries in the Middle East use large-scale desalination plants to meet their water needs. Desalination plants use heat to evaporate water (leaving the salt behind) or pumps to run water through membranes that filter out the salt. Both technologies are costly and energy-intensive. The extracted salt must also be disposed of in a way that does not damage the environment. New smaller-scale technologies using solar panels and more efficient filters are making desalination more accessible and affordable How do we keep fresh water clean: Globally, 2.5 billion people lack access to sanitary wastewater systems and 1.8 billion people use a source of drinking water that is contaminated with sewage.  Most developed nations use septic tanks or sewage treatment plants to filter and treat wastes and produce clean water. Small-scale water purification technologies include ceramic filters and the solar Water cone, which uses the heat of the sun to kill pathogens, remove particulates, and desalinate seawater. Green roofs can reduce runoff, improving infiltration and uptake by plants. Regulations are also important for clean water. Nonpoint sources of water pollution are difficult to regulate, but actions can still be taken. Farmers can limit the amount of fertilizers and pesticides they use, and leave vegetated buffer zones around crops to slow surface runoff. Public awareness campaigns about pollution are another important tool. Why is frozen water important : If all of Greenland’s ice melted, sea-levels would raise by about 6 meters. If all of Antarctica’s ice melted, sea-levels would raise by about 60 meters. A large input of fresh glacial meltwater will disrupt ocean currents, which are a major influence on global climate.  Sea ice is defined as frozen water that covers about 15% of the ocean for at least part of the year. Most sea ice is seasonal. Sea ice impacts global climate through its reflectivity or albedo: by deflecting the Sun’s rays, sea ice has a cooling effect on the ocean water below it. When sea ice melts, the temperature of the ocean increases, but it does not contribute to sea-level rise. The cryosphere also includes permafrost, which is water perpetually frozen in soil or rock. Permafrost can extend as deep as several thousand feet belowground and remain frozen for hundreds of thousands of years. 1. Melting permafrost contributes to sea-level rise. 2. Melting permafrost also releases methane, a greenhouse gas that contributes to the increasing rate of global warming. How does the ocean support life ? : Oceans contain many different ecosystems that receive varying levels of sunlight. Unique organisms live in the intertidal zone and are adapted to both high and low tide conditions, including star fish, sea anemones, barnacles, burrowing crabs, and species of seaweeds. Just beyond the intertidal zone, the shallow water area just above the continental shelf is called the neritic zone. The neritic zone has plentiful sunlight leading to an abundance of phytoplankton (algae), which provides food for shrimp, jellyfish, snails, and small fish. Tropical coral reefs grow in the neritic zone and support diverse ecosystems by providing protection and structure for algae. Algae growing on coral provide oxygen, nutrients, and waste removal How can humans impact the oceans : Human food and energy production and waste disposal impact the ocean. Terrestrial food production also affects oceans with fertilizer run-off creating dead zones. The use of fossil fuels affects the ocean with oil spills and the burning greenhouse gases can lead to ocean acidification. Plastic waste can entangle sea life and also breaks down into very small pieces ingested by marine organisms.