The Hydrologic Cycle | Earth Science

<!DOCTYPE html> <html lang="en" dir="ltr"> <head>  <meta http-equiv="X-UA-Compatible" content="ie=edge"> <meta charset="utf-8"> <base href="https://www.visionlearning.com"> <title>The Hydrologic Cycle | Earth Science | Visionlearning</title> <link rel="canonical" href="https://www.visionlearning.com/en/library/earth-science/6/the-hydrologic-cycle/99"> <meta name="description" content="Powered by the sun, water constantly cycles through the Earth and its atmosphere. This module discusses the hydrologic cycle, including the various water reservoirs in the oceans, in the air, and on the land. The module addresses connections between the hydrologic cycle, climate, and the impacts humans have had on the cycle."> <meta name="keywords" content="science, education, STEM, math, biology, chemistry, physics, earth science, online learning"> <meta name="viewport" content="width=device-width, initial-scale=1.0, shrink-to-fit=no"> <meta name="msvalidate.01" content="D8E20F39AD48052260032E56DE409970"> <script type="application/ld+json"> { "@context": "http://schema.org/", "@type": "Article", "mainEntityOfPage": { "@type": "WebPage", "@id": "https://visionlearning.com/en/library/earth-science/6/the-hydrologic-cycle/99" }, "name": "The Hydrologic Cycle", "headline": "The Hydrologic Cycle: Reservoirs and fluxes of water on Earth", "author": { "@type": "Person", "name": "Anne E. Egger, Ph.D." }, "datePublished": "2003-08-26 10:49:29", "dateModified": "2017-02-12T08:30:00+05:00", "image": { "@type": "ImageObject", "url": "/img/library/moduleImages/featured_image_99-23061209065611.jpg", "width": 696, "height": 464 }, "publisher": { "@type": "Organization", "name": "Visionlearning, Inc.", "logo": { "@type": "ImageObject", "url": "http://visionlearning.com/images/logo.png", "width": 278, "height": 60 } }, "description": "Powered by the sun, water constantly cycles through the Earth and its atmosphere. This module discusses the hydrologic cycle, including the various water reservoirs in the oceans, in the air, and on the land. The module addresses connections between the hydrologic cycle, climate, and the impacts humans have had on the cycle.", "keywords": "science, education, STEM, math, biology, chemistry, physics, earth science, online learning", "inLanguage": { "@type": "Language", "name": "English", "alternateName": "en" }, "copyrightHolder": { "@type": "Organization", "name": "Visionlearning, Inc." }, "copyrightYear": "2003"} </script> <meta property="og:url" content="https://visionlearning.com/en/library/earth-science/6/the-hydrologic-cycle/99"> <meta property="og:title" content="The Hydrologic Cycle | Earth Science | Visionlearning" /> <meta property="og:type" content="website"> <meta property="og:site_name" content="Visionlearning"> <meta property="og:description" content="Powered by the sun, water constantly cycles through the Earth and its atmosphere. This module discusses the hydrologic cycle, including the various water reservoirs in the oceans, in the air, and on the land. 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href="/en/library/environmental-science/61/biodiversity-i/276">Biodiversity I</a></li> <li><a href="/en/library/environmental-science/61/biodiversity-ii/281">Biodiversity II</a></li> <li><a href="/en/library/environmental-science/61/ecosystem-services/279">Ecosystem Services</a></li> <li><a href="/en/library/environmental-science/61/population-biology/287">Population Biology</a></li> </ul> </div> <button class="accordion__button" id="acc-button-earth-cycles" data-accordion="button" aria-controls="acc-panel-earth-cycles" aria-expanded="false"> <span class="accordion__button__label"> Earth Cycles </span> </button> <div class="accordion__panel" id="acc-panel-earth-cycles" data-accordion="panel" aria-labelledby="acc-button-earth-cycles" role="region"> <ul class="nav text-color-link"> <li><a href="/en/library/environmental-science/61/the-nitrogen-cycle/98">The Nitrogen Cycle</a></li> <li><a href="/en/library/environmental-science/61/the-carbon-cycle/95">The Carbon Cycle</a></li> <li><a href="/en/library/environmental-science/61/the-phosphorus-cycle/197">The Phosphorus Cycle</a></li> </ul> </div> <button class="accordion__button" id="acc-button-scientific-research" data-accordion="button" aria-controls="acc-panel-scientific-research" aria-expanded="false"> <span class="accordion__button__label"> Scientific Research </span> </button> <div class="accordion__panel" id="acc-panel-scientific-research" data-accordion="panel" aria-labelledby="acc-button-scientific-research" role="region"> <ul class="nav text-color-link"> <li><a href="/en/library/environmental-science/61/collaborative-research-in-the-arctic-towards-understanding-climate-change/183">Collaborative Research in the Arctic Towards Understanding Climate Change</a></li> <li><a href="/en/library/environmental-science/61/atmospheric-chemistry-research-that-changed-global-policy/211">Atmospheric Chemistry Research that Changed Global Policy</a></li> </ul> </div> </div> </div> <button class="accordion__button" id="acc-button-general-science" data-accordion="button" aria-controls="acc-panel-general-science" aria-expanded="false"> <span class="accordion__button__label"> General Science </span> </button> <div class="accordion__panel" id="acc-panel-general-science" data-accordion="panel" aria-labelledby="acc-button-general-science" role="region"> <div class="accordion accordion--secondary"> <button class="accordion__button" id="acc-button-methods" data-accordion="button" aria-controls="acc-panel-methods" aria-expanded="false"> <span class="accordion__button__label"> Methods </span> </button> <div class="accordion__panel" id="acc-panel-methods" data-accordion="panel" aria-labelledby="acc-button-methods" role="region"> <ul class="nav text-color-link"> <li><a href="/en/library/general-science/3/the-scientific-method/45">The Scientific Method</a></li> </ul> </div> <button class="accordion__button" id="acc-button-measurement" data-accordion="button" aria-controls="acc-panel-measurement" aria-expanded="false"> <span class="accordion__button__label"> Measurement </span> </button> <div class="accordion__panel" id="acc-panel-measurement" data-accordion="panel" aria-labelledby="acc-button-measurement" role="region"> <ul class="nav text-color-link"> <li><a href="/en/library/general-science/3/the-metric-system/47">The Metric System</a></li> </ul> </div> <button class="accordion__button" id="acc-button-physical-properties" data-accordion="button" aria-controls="acc-panel-physical-properties" aria-expanded="false"> <span class="accordion__button__label"> Physical Properties </span> </button> <div class="accordion__panel" id="acc-panel-physical-properties" data-accordion="panel" aria-labelledby="acc-button-physical-properties" role="region"> <ul class="nav text-color-link"> <li><a href="/en/library/general-science/3/temperature/48">Temperature</a></li> <li><a href="/en/library/general-science/3/density-and-buoyancy/37">Density and Buoyancy</a></li> </ul> </div> </div> </div> <button class="accordion__button" id="acc-button-math-in-science" data-accordion="button" aria-controls="acc-panel-math-in-science" aria-expanded="false"> <span class="accordion__button__label"> Math in Science </span> </button> <div class="accordion__panel" id="acc-panel-math-in-science" data-accordion="panel" aria-labelledby="acc-button-math-in-science" role="region"> <div class="accordion accordion--secondary"> <button class="accordion__button" id="acc-button-equations" data-accordion="button" aria-controls="acc-panel-equations" aria-expanded="false"> <span class="accordion__button__label"> Equations </span> </button> <div class="accordion__panel" id="acc-panel-equations" data-accordion="panel" aria-labelledby="acc-button-equations" role="region"> <ul class="nav text-color-link"> <li><a href="/en/library/math-in-science/62/unit-conversion/144">Unit Conversion</a></li> <li><a href="/en/library/math-in-science/62/linear-equations/194">Linear Equations</a></li> <li><a href="/en/library/math-in-science/62/exponential-equations-i/206">Exponential Equations I</a></li> <li><a href="/en/library/math-in-science/62/exponential-equations-ii/210">Exponential Equations II</a></li> <li><a href="/en/library/math-in-science/62/scientific-notation/250">Scientific Notation</a></li> <li><a href="/en/library/math-in-science/62/measurement/257">Measurement</a></li> </ul> </div> <button class="accordion__button" id="acc-button-statistics" data-accordion="button" aria-controls="acc-panel-statistics" aria-expanded="false"> <span class="accordion__button__label"> Statistics </span> </button> <div class="accordion__panel" id="acc-panel-statistics" data-accordion="panel" aria-labelledby="acc-button-statistics" role="region"> <ul class="nav text-color-link"> <li><a href="/en/library/math-in-science/62/introduction-to-descriptive-statistics/218">Introduction to Descriptive Statistics</a></li> <li><a href="/en/library/math-in-science/62/introduction-to-inferential-statistics/224">Introduction to Inferential Statistics</a></li> <li><a href="/en/library/math-in-science/62/statistical-techniques/239">Statistical Techniques</a></li> </ul> </div> <button class="accordion__button" id="acc-button-trigonometric-functions" data-accordion="button" aria-controls="acc-panel-trigonometric-functions" aria-expanded="false"> <span class="accordion__button__label"> Trigonometric Functions </span> </button> <div class="accordion__panel" id="acc-panel-trigonometric-functions" data-accordion="panel" aria-labelledby="acc-button-trigonometric-functions" role="region"> <ul class="nav text-color-link"> <li><a href="/en/library/math-in-science/62/wave-mathematics/131">Wave Mathematics</a></li> </ul> </div> </div> </div> <button class="accordion__button" id="acc-button-physics" data-accordion="button" aria-controls="acc-panel-physics" aria-expanded="false"> <span class="accordion__button__label"> Physics </span> </button> <div class="accordion__panel" id="acc-panel-physics" data-accordion="panel" aria-labelledby="acc-button-physics" role="region"> <div class="accordion accordion--secondary"> <button class="accordion__button" id="acc-button-light-and-optics" data-accordion="button" aria-controls="acc-panel-light-and-optics" aria-expanded="false"> <span class="accordion__button__label"> Light and Optics </span> </button> <div class="accordion__panel" id="acc-panel-light-and-optics" data-accordion="panel" aria-labelledby="acc-button-light-and-optics" role="region"> <ul class="nav text-color-link"> <li><a href="/en/library/physics/24/the-nature-of-light/132">The Nature of Light</a></li> <li><a href="/en/library/physics/24/electromagnetism-and-light/138">Electromagnetism and Light</a></li> </ul> </div> <button class="accordion__button" id="acc-button-mechanics" data-accordion="button" aria-controls="acc-panel-mechanics" aria-expanded="false"> <span class="accordion__button__label"> Mechanics </span> </button> <div class="accordion__panel" id="acc-panel-mechanics" data-accordion="panel" aria-labelledby="acc-button-mechanics" role="region"> <ul class="nav text-color-link"> <li><a href="/en/library/physics/24/defining-energy/199">Defining Energy</a></li> <li><a href="/en/library/physics/24/waves-and-wave-motion/102">Waves and Wave Motion</a></li> <li><a href="/en/library/physics/24/gravity/118">Gravity</a></li> <li><a href="/en/library/physics/24/thermodynamics-i/200">Thermodynamics I</a></li> </ul> </div> </div> </div> <button class="accordion__button" id="acc-button-process-of-science" data-accordion="button" aria-controls="acc-panel-process-of-science" aria-expanded="false"> <span class="accordion__button__label"> Process of Science </span> </button> <div class="accordion__panel" id="acc-panel-process-of-science" data-accordion="panel" aria-labelledby="acc-button-process-of-science" role="region"> <div class="accordion accordion--secondary"> <button class="accordion__button" id="acc-button-introduction" data-accordion="button" aria-controls="acc-panel-introduction" aria-expanded="false"> <span class="accordion__button__label"> Introduction </span> </button> <div class="accordion__panel" id="acc-panel-introduction" data-accordion="panel" aria-labelledby="acc-button-introduction" role="region"> <ul class="nav text-color-link"> <li><a href="/en/library/process-of-science/49/the-process-of-science/176">The Process of Science</a></li> </ul> </div> <button class="accordion__button" id="acc-button-the-culture-of-science" data-accordion="button" aria-controls="acc-panel-the-culture-of-science" aria-expanded="false"> <span class="accordion__button__label"> The Culture of Science </span> </button> <div class="accordion__panel" id="acc-panel-the-culture-of-science" data-accordion="panel" aria-labelledby="acc-button-the-culture-of-science" role="region"> <ul class="nav text-color-link"> <li><a href="/en/library/process-of-science/49/the-nature-of-scientific-knowledge/185">The Nature of Scientific Knowledge</a></li> <li><a href="/en/library/process-of-science/49/scientists-and-the-scientific-community/172">Scientists and the Scientific Community</a></li> <li><a href="/en/library/process-of-science/49/scientific-ethics/161">Scientific Ethics</a></li> <li><a href="/en/library/process-of-science/49/scientific-institutions-and-societies/162">Scientific Institutions and Societies</a></li> </ul> </div> <button class="accordion__button" id="acc-button-ideas-in-science" data-accordion="button" aria-controls="acc-panel-ideas-in-science" aria-expanded="false"> <span class="accordion__button__label"> Ideas in Science </span> </button> <div class="accordion__panel" id="acc-panel-ideas-in-science" data-accordion="panel" aria-labelledby="acc-button-ideas-in-science" role="region"> <ul class="nav text-color-link"> <li><a href="/en/library/process-of-science/49/theories-hypotheses-and-laws/177">Theories, Hypotheses, and Laws</a></li> <li><a href="/en/library/process-of-science/49/scientific-controversy/181">Scientific Controversy</a></li> <li><a href="/en/library/process-of-science/49/creativity-in-science/182">Creativity in Science</a></li> </ul> </div> <button class="accordion__button" id="acc-button-research-methods" data-accordion="button" aria-controls="acc-panel-research-methods" aria-expanded="false"> <span class="accordion__button__label"> Research Methods </span> </button> <div class="accordion__panel" id="acc-panel-research-methods" data-accordion="panel" aria-labelledby="acc-button-research-methods" role="region"> <ul class="nav text-color-link"> <li><a href="/en/library/process-of-science/49/the-practice-of-science/148">The Practice of Science</a></li> <li><a href="/en/library/process-of-science/49/experimentation-in-scientific-research/150">Experimentation in Scientific Research</a></li> <li><a href="/en/library/process-of-science/49/description-in-scientific-research/151">Description in Scientific Research</a></li> <li><a href="/en/library/process-of-science/49/comparison-in-scientific-research/152">Comparison in Scientific Research</a></li> <li><a href="/en/library/process-of-science/49/modeling-in-scientific-research/153">Modeling in Scientific Research</a></li> </ul> </div> <button class="accordion__button" id="acc-button-data" data-accordion="button" aria-controls="acc-panel-data" aria-expanded="false"> <span class="accordion__button__label"> Data </span> </button> <div class="accordion__panel" id="acc-panel-data" data-accordion="panel" aria-labelledby="acc-button-data" role="region"> <ul class="nav text-color-link"> <li><a href="/en/library/process-of-science/49/data-analysis-and-interpretation/154">Data Analysis and Interpretation</a></li> <li><a href="/en/library/process-of-science/49/uncertainty-error-and-confidence/157">Uncertainty, Error, and Confidence</a></li> <li><a href="/en/library/process-of-science/49/statistics-in-science/155">Statistics in Science</a></li> <li><a href="/en/library/process-of-science/49/using-graphs-and-visual-data-in-science/156">Using Graphs and Visual Data in Science</a></li> </ul> </div> <button class="accordion__button" id="acc-button-scientific-communication" data-accordion="button" aria-controls="acc-panel-scientific-communication" aria-expanded="false"> <span class="accordion__button__label"> Scientific Communication </span> </button> <div class="accordion__panel" id="acc-panel-scientific-communication" data-accordion="panel" aria-labelledby="acc-button-scientific-communication" role="region"> <ul class="nav text-color-link"> <li><a href="/en/library/process-of-science/49/understanding-scientific-journals-and-articles/158">Understanding Scientific Journals and Articles</a></li> <li><a href="/en/library/process-of-science/49/utilizing-the-scientific-literature/173">Utilizing the Scientific Literature</a></li> <li><a href="/en/library/process-of-science/49/peer-review-in-scientific-publishing/159">Peer Review in Scientific Publishing</a></li> <li><a href="/en/library/process-of-science/49/the-how-and-why-of-scientific-meetings/186">The How and Why of Scientific Meetings</a></li> </ul> </div> </div> </div> <button class="accordion__button" id="acc-button-scientists-and-research" data-accordion="button" aria-controls="acc-panel-scientists-and-research" aria-expanded="false"> <span class="accordion__button__label"> Scientists and Research </span> </button> <div class="accordion__panel" id="acc-panel-scientists-and-research" data-accordion="panel" aria-labelledby="acc-button-scientists-and-research" role="region"> <div class="accordion accordion--secondary"> <button class="accordion__button" id="acc-button-scientific-research" data-accordion="button" aria-controls="acc-panel-scientific-research" aria-expanded="false"> <span class="accordion__button__label"> Scientific Research </span> </button> <div class="accordion__panel" id="acc-panel-scientific-research" data-accordion="panel" aria-labelledby="acc-button-scientific-research" role="region"> <ul class="nav text-color-link"> <li><a href="/en/library/scientists-and-research/58/collaborative-research-in-the-arctic-towards-understanding-climate-change/183">Collaborative Research in the Arctic Towards Understanding Climate Change</a></li> <li><a href="/en/library/scientists-and-research/58/from-stable-chromosomes-to-jumping-genes/184">From Stable Chromosomes to Jumping Genes</a></li> <li><a href="/en/library/scientists-and-research/58/an-elegant-experiment-to-test-the-process-of-dna-replication/187">An Elegant Experiment to Test the Process of DNA Replication</a></li> <li><a href="/en/library/scientists-and-research/58/the-founding-of-neuroscience/233">The Founding of Neuroscience</a></li> <li><a href="/en/library/scientists-and-research/58/tracking-endangered-jaguars-across-the-border/189">Tracking Endangered Jaguars across the Border</a></li> <li><a href="/en/library/scientists-and-research/58/atmospheric-chemistry-research-that-changed-global-policy/211">Atmospheric Chemistry Research that Changed Global Policy</a></li> <li><a href="/en/library/scientists-and-research/58/revolutionizing-medicine-with-monoclonal-antibodies/220">Revolutionizing Medicine with Monoclonal Antibodies</a></li> <li><a href="/en/library/scientists-and-research/58/uncovering-the-mysteries-of-chronic-mountain-sickness/238">Uncovering the Mysteries of Chronic Mountain Sickness</a></li> </ul> </div> <button class="accordion__button" id="acc-button-profiles-in-science" data-accordion="button" aria-controls="acc-panel-profiles-in-science" aria-expanded="false"> <span class="accordion__button__label"> Profiles in Science </span> </button> <div class="accordion__panel" id="acc-panel-profiles-in-science" data-accordion="panel" aria-labelledby="acc-button-profiles-in-science" role="region"> <ul class="nav text-color-link"> <li><a href="/en/library/scientists-and-research/58/luis-e.-miramontes/232">Luis E. Miramontes</a></li> <li><a href="/en/library/scientists-and-research/58/bernardo-houssay/237">Bernardo Houssay</a></li> <li><a href="/en/library/scientists-and-research/58/craig-lee/256">Craig Lee</a></li> <li><a href="/en/library/scientists-and-research/58/david-ho/241">David Ho</a></li> <li><a href="/en/library/scientists-and-research/58/louis-tompkins-wright/244">Louis Tompkins Wright</a></li> <li><a href="/en/library/scientists-and-research/58/carlos-j.-finlay/217">Carlos J. Finlay</a></li> <li><a href="/en/library/scientists-and-research/58/cecilia-payne/290">Cecilia Payne</a></li> <li><a href="/en/library/scientists-and-research/58/jazmin-scarlett/291">Jazmin Scarlett</a></li> <li><a href="/en/library/scientists-and-research/58/ramari-stewart/292">Ramari Stewart</a></li> <li><a href="/en/library/scientists-and-research/58/johnson-cerda/300">Johnson Cerda</a></li> <li><a href="/en/library/scientists-and-research/58/ellen-ochoa/201">Ellen Ochoa</a></li> <li><a href="/en/library/scientists-and-research/58/ruth-benerito/205">Ruth Benerito</a></li> <li><a href="/en/library/scientists-and-research/58/franklin-chang-díaz/219">Franklin Chang Díaz</a></li> <li><a href="/en/library/scientists-and-research/58/percy-lavon-julian/221">Percy Lavon Julian</a></li> <li><a href="/en/library/scientists-and-research/58/luis-walter-alvarez/229">Luis Walter Alvarez</a></li> <li><a href="/en/library/scientists-and-research/58/france-anne-dominic-córdova/230">France Anne-Dominic Córdova</a></li> </ul> </div> </div> </div> </div> </div> </li> <li>  <button class="button" data-toggle="dropdown">Earth Science </button> <div class="nav__dropdown box-shadow-1 padding-1"> <div class="accordion accordion--secondary font-size-sm"> <div class="accordion accordion--secondary"> <button class="accordion__button" id="acc-sub-button-plate-tectonics" data-accordion="button" aria-controls="acc-sub-panel-plate-tectonics" aria-expanded="false"> <span class="accordion__button__label"> Plate Tectonics </span> </button> <div class="accordion__panel" id="acc-sub-panel-plate-tectonics" data-accordion="panel" aria-labelledby="acc-sub-button-plate-tectonics" role="region"> <ul class="nav text-color-link"> <li><a href="/en/library/earth-science/6/origins-of-plate-tectonic-theory/65">Origins of Plate Tectonic Theory</a></li> <li><a href="/en/library/earth-science/6/plate-boundaries/66">Plate Boundaries</a></li> <li><a href="/en/library/earth-science/6/earth-structure/69">Earth Structure</a></li> </ul> </div> <button class="accordion__button" id="acc-sub-button-earth-cycles" data-accordion="button" aria-controls="acc-sub-panel-earth-cycles" aria-expanded="false"> <span class="accordion__button__label"> Earth Cycles </span> </button> <div class="accordion__panel" id="acc-sub-panel-earth-cycles" data-accordion="panel" aria-labelledby="acc-sub-button-earth-cycles" role="region"> <ul class="nav text-color-link"> <li><a href="/en/library/earth-science/6/the-rock-cycle/128">The Rock Cycle</a></li> <li class="current">The Hydrologic Cycle</li> <li><a href="/en/library/earth-science/6/the-carbon-cycle/95">The Carbon Cycle</a></li> <li><a href="/en/library/earth-science/6/the-nitrogen-cycle/98">The Nitrogen Cycle</a></li> <li><a href="/en/library/earth-science/6/the-phosphorus-cycle/197">The Phosphorus Cycle</a></li> </ul> </div> <button class="accordion__button" id="acc-sub-button-rocks-and-minerals" data-accordion="button" aria-controls="acc-sub-panel-rocks-and-minerals" aria-expanded="false"> <span class="accordion__button__label"> Rocks and Minerals </span> </button> <div class="accordion__panel" id="acc-sub-panel-rocks-and-minerals" data-accordion="panel" aria-labelledby="acc-sub-button-rocks-and-minerals" role="region"> <ul class="nav text-color-link"> <li><a href="/en/library/earth-science/6/defining-minerals/119">Defining Minerals</a></li> <li><a href="/en/library/earth-science/6/identifying-minerals/130">Identifying Minerals</a></li> <li><a href="/en/library/earth-science/6/the-silicate-minerals/140">The Silicate Minerals</a></li> </ul> </div> <button class="accordion__button" id="acc-sub-button-atmosphere-and-oceans" data-accordion="button" aria-controls="acc-sub-panel-atmosphere-and-oceans" aria-expanded="false"> <span class="accordion__button__label"> Atmosphere and Oceans </span> </button> <div class="accordion__panel" id="acc-sub-panel-atmosphere-and-oceans" data-accordion="panel" aria-labelledby="acc-sub-button-atmosphere-and-oceans" role="region"> <ul class="nav text-color-link"> <li><a href="/en/library/earth-science/6/ocean-currents/282">Ocean Currents</a></li> <li><a href="/en/library/earth-science/6/water-in-the-atmosphere/289">Water in the Atmosphere</a></li> <li><a href="/en/library/earth-science/6/weather-fronts-and-forecasts/303">Weather, Fronts, and Forecasts</a></li> <li><a href="/en/library/earth-science/6/history-of-earths-atmosphere-i/202">History of Earth's Atmosphere I</a></li> <li><a href="/en/library/earth-science/6/history-of-earths-atmosphere-ii/203">History of Earth's Atmosphere II</a></li> <li><a href="/en/library/earth-science/6/earths-atmosphere/107">Earth's Atmosphere</a></li> <li><a href="/en/library/earth-science/6/factors-that-control-earths-temperature/234">Factors that Control Earth's Temperature</a></li> <li><a href="/en/library/earth-science/6/circulation-in-the-atmosphere/255">Circulation in the Atmosphere</a></li> </ul> </div> <button class="accordion__button" id="acc-sub-button-hazards" data-accordion="button" aria-controls="acc-sub-panel-hazards" aria-expanded="false"> <span class="accordion__button__label"> Hazards </span> </button> <div class="accordion__panel" id="acc-sub-panel-hazards" data-accordion="panel" aria-labelledby="acc-sub-button-hazards" role="region"> <ul class="nav text-color-link"> <li><a href="/en/library/earth-science/6/natural-hazards-and-risk/288">Natural Hazards and Risk</a></li> </ul> </div> <button class="accordion__button" id="acc-sub-button-earth-history" data-accordion="button" aria-controls="acc-sub-panel-earth-history" aria-expanded="false"> <span class="accordion__button__label"> Earth History </span> </button> <div class="accordion__panel" id="acc-sub-panel-earth-history" data-accordion="panel" aria-labelledby="acc-sub-button-earth-history" role="region"> <ul class="nav text-color-link"> <li><a href="/en/library/earth-science/6/extinction/295">Extinction</a></li> <li><a href="/en/library/earth-science/6/mass-extinctions/294">Mass Extinctions</a></li> </ul> </div> </div> </div> </div> </li> </ul> </nav>  <div id="theTop"></div> <main id="skip-header-content"> <div class="margin-bottom-5"> <article class="container wide module"> <header class="grid grid--sidebar-right module__header"> <div class="module__header__title"> <span class="subcategory"> <strong><em>Earth Cycles</em></strong> </span> <h1>The Hydrologic Cycle: <sub><em>Reservoirs and fluxes of water on Earth</em></sub></h1> <p class="byline">by Anne E. Egger, Ph.D.</p> <nav class="module__header__tabs"> <ul class="tabs-nav tabs-nav--horizontal library"> <li> <a href="/en/library/earth-science/6/the-hydrologic-cycle/99/reading" aria-current="page" >Reading</a> </li> <li> <a href="/en/library/earth-science/6/the-hydrologic-cycle/99/quiz">Quiz</a> </li> <li> <a href="/en/library/earth-science/6/the-hydrologic-cycle/99/resources">Teach with this</a> </li> </ul> </nav> </div> <script type="application/ld+json"> { "@context": "http://schema.org", "@type": "AudioObject", "contentUrl": "https://www.visionlearning.com/img/library/moduleAudio/module_99.mp3", "description": "Recording of The Hydrologic Cycle : Powered by the sun, water constantly cycles through the Earth and its atmosphere. This module discusses the hydrologic cycle, including the various water reservoirs in the oceans, in the air, and on the land. The module addresses connections between the hydrologic cycle, climate, and the impacts humans have had on the cycle.", "encodingFormat": "mp3", "name": "module_99.mp3" } </script> <div class="module_header_audio"> <div class="audio-player border border-radius"> <audio id="audio"> <source src="https://www.visionlearning.com/img/library/moduleAudio/module_99.mp3" type="audio/mpeg"> Your browser does not support the audio element. </audio> <div class="audio-player__title"> <p>Listen to this reading</p> <span class="audio-player__timestamp" id="timestamp"> 00:00 </span> </div> <div class="audio-player__controls" id="controls"> <button class="button button--icon-only" id="play-pause-button"> <span class="icon icon-play" aria-hidden="true"></span> </button> <div class="audio-player__progress" id="progress-bar" tabindex="0" aria-valuemin="0" aria-valuemax="100" aria-valuenow="0" aria-label="Use arrow keys to forward or rewind the audio" role="slider"> <div class="audio-player__progress__fill"> <span class="audio-player__thumb"></span> </div> </div> <div class="audio-player__volume-container"> <button id="mute-button"> <span class="icon icon-volume"></span> </button> <div class="audio-player__volume" tabindex="0" aria-valuemin="0" aria-valuemax="100" aria-valuenow="100" aria-label="Use arrow keys to adjust volume" role="slider"> <div class="audio-player__volume__fill"> <span class="audio-player__thumb"></span> </div> </div> </div> </div> </div> </div> </header> <hr class="divider"/>   <div class="grid grid--sidebar-right grid--divider"> <div class="order-2 order-1--lg module__main"> <div class="narrow margin-x-auto margin-y-5"> <div class="accordion margin-bottom-5">  <button class="accordion__button" id="acc-button-key-concepts" data-accordion="button" aria-controls="acc-panel-key-concepts" aria-expanded="true" tabindex="0"> Did you know? </button> <div class="accordion__panel shown show" id="acc-panel-key-concepts" data-accordion="panel" aria-labelledby="acc-button-key-concepts" role="region"> <div class="accordion__panel__content"> <p>Did you know that rising sea levels do not mean that the amount of water on Earth is increasing? Rather, the amount of water on Earth remains the same, but with global warming, glaciers diminish and sea levels rise. With warmer temperatures comes more evaporation, which causes an increase in precipitation and extreme weather across the planet.</p> </div> </div>  <button class="accordion__button" id="acc-button-table-of-contents" data-accordion="button" aria-controls="acc-panel-table-of-contents" aria-expanded="false" tabindex="0"> Key concepts </button> <div class="accordion__panel" id="acc-panel-table-of-contents" data-accordion="panel" aria-labelledby="acc-button-table-of-contents" role="region" aria-hidden="true"> <div class="accordion__panel__content"> <ul class="bulleted"><li><p>Though the amount of water on Earth remains constant, it is regularly cycling through the ecosystem through various processes.</p></li> <li><p>Earth's water supply is stored in a variety of ways, from ice sheets to oceans to underground reservoirs.</p></li> <li><p>Like other processes occurring on Earth, the hydrologic cycle is affected by global warming and, as a result, influences climate and weather patterns.</p></li></ul> </div> </div>  <button class="accordion__button" id="acc-button-terms-you-should-know" data-accordion="button" aria-controls="acc-panel-terms-you-should-know" aria-expanded="false" tabindex="0"> Terms you should know </button> <div class="accordion__panel" id="acc-panel-terms-you-should-know" data-accordion="panel" aria-labelledby="acc-button-terms-you-should-know" role="region" aria-hidden="true"> <div class="accordion__panel__content"> <dl> <dt><a href="/en/glossary/view/condensation">condensation </a></dt> <dd> the process of forming a liquid from a gas </dd> <dt><a href="/en/glossary/view/precipitation">precipitation </a></dt> <dd> water that falls from the atmosphere to the ground in any form, such as rain, snow, hail, or sleet </dd> <dt>soak </dt> <dd> to be absorbed; to immerse in a liquid until wet through and through </dd> <dt><a href="/en/glossary/view/soil">soil </a></dt> <dd> the loose top layer of Earth’s surface where plants grow, made up of particles of rocks, minerals, and organic material.</dd> </dl> </div> </div> </div> <hr class="border-color-dark" /> <section> <div class="container narrow"> <p>As recently as 12,000 years ago, you could walk from Alaska to Siberia without having to don a wetsuit. At that time, glaciers and ice sheets covered North America down to the Great Lakes and Cape Cod, though coastal areas generally remained ice-free. These extensive ice sheets occurred at a time when sea level was very low, exposing land where water now fills the Bering Strait. In fact, throughout Earth’s history, times of extensive glaciers correlate with low sea level and times when only minor ice sheets exist (like today) correlate with high sea levels. These <mark class="term" data-term="correlation" data-term-def="Correlation, as measured by the correlation coefficient, provides a measure of the strength and direction of a linear relationship between two&hellip;" data-term-url="/en/glossary/view/correlation/3912">correlations</mark> are due to the fact that the amount of water on Earth is constant, and is divided up between reservoirs in the oceans, in the air, and on the land. In addition, Earth’s water is constantly cycling through these reservoirs in a <mark class="term" data-term="process" data-term-def="Method, procedure; series of actions or steps." data-term-url="/en/glossary/view/process/8256">process</mark> called the <em>hydrologic cycle</em>. Both of these facts together lead us to the conclusion that more water stored in ice sheets means less water in the oceans.</p> <p>Earth is the only planet in our solar <mark class="term" data-term="system" data-term-def="A group of interacting, interrelated or interdependent components that form a complex whole. The size of the system is defined for&hellip;" data-term-url="/en/glossary/view/system/3904">system</mark> with extensive <mark class="term" data-term="liquid" data-term-def="The state of matter characterized by its condensed nature and ability to flow. Unlike gases, molecules within a liquid often experience&hellip;" data-term-url="/en/glossary/view/liquid/8727">liquid</mark> water – other planets are too hot or too cold, too big or too small. Though Mars appears to have had water on its <mark class="term" data-term="surface" data-term-def="The outside or external part; the topside face of something." data-term-url="/en/glossary/view/surface/8275">surface</mark> in the past and may still harbor liquid water deep below its surface, our oceans, rivers, and rain are unique as far as we know, and they are life-sustaining. Understanding the processes and reservoirs of the hydrologic cycle is fundamental to dealing with many issues, including pollution and global <mark class="term" data-term="climate" data-term-def="Climate describes the average and patterns of a particular area’s weather over time. Climate includes such elements as temperature, precipitation, humidity,&hellip;" data-term-url="/en/glossary/view/climate/9334">climate</mark> change.</p><p>As early as 800 <mark class="term" data-term="BCE" data-term-def="An abbreviation for Before the Common Era, which is a designation for the years prior to year 1 of the Gregorian&hellip;" data-term-url="/en/glossary/view/BCE/3720">BCE</mark>, Homer wrote in the <em>Iliad</em> of the ocean "from whose deeps every river and sea, every spring and well flows," suggesting the interconnectedness of all of Earth's water. It wasn't until the 17th century, however, that the poetic notion of a finite water cycle was demonstrated in the Seine River basin by two French physicists, Edmé Mariotte and Pierre Perrault, who independently determined that the snowpack in the river's headwaters was more than sufficient to account for the river's discharge. These two studies marked the beginning of hydrology, the science of water, and also the hydrologic cycle.</p> <p><section id="toc_1" class=""> <h2>Hydrologic cycle</h2></p> <p>The hydrologic cycle can be thought of as a series of reservoirs, or storage areas, and a set of processes that cause water to move between those reservoirs (see Figure 1). The largest reservoir by far is the oceans, which hold about 97% of Earth’s water. The remaining 3% is the freshwater so important to our survival, but about 78% of that is stored in ice in Antarctica and Greenland. About 21% of freshwater on Earth is <mark class="term" data-term="groundwater" data-term-def="Water that fills pore space in rocks and sediments and forms a subsurface aquifer. Groundwater is distinct from soil moisture, which&hellip;" data-term-url="/en/glossary/view/groundwater/2119">groundwater</mark>, stored in <mark class="term" data-term="sediment" data-term-def="Loose, unconsolidated material of the following compositions: <br> 1. rock fragments (also called clasts) transported by wind, moving water,&hellip;" data-term-url="/en/glossary/view/sediment/3310">sediments</mark> and rocks below the <mark class="term" data-term="surface" data-term-def="The outside or external part; the topside face of something." data-term-url="/en/glossary/view/surface/8275">surface</mark> of Earth. The freshwater that we see in rivers, streams, lakes, and rain is less than 1% of the freshwater on Earth and less than 0.1% of all the water on Earth.</p> <div class="figure"> <figure> <button class="lightbox-button lightbox-button--icon" data-lightbox="" data-lightbox-src="/img/library/large_images/image_12723.png"> <img src="/img/library/modules/mid99/Image/VLObject-12723-22102109100207.png" alt="Figure 1: A depiction of the hydrologic cycle showing reservoirs and their volumes in bold and fluxes between reservoirs and their rates in italics." /> </button> <figcaption> <p><strong>Figure 1:</strong> A depiction of the hydrologic cycle showing reservoirs and their volumes in bold and fluxes between reservoirs and their rates in italics.</p> </figcaption> </figure> </div> <div class="comprehension-checkpoint margin-y-4"> <h6 class="comprehension-checkpoint__header"> <span> <span class="icon icon-question"></span> </span> Comprehension Checkpoint </h6> <form class="" name="cc6483"> <div class="form-entry"> <div class="form-entry__field"> <span class="form-entry__field__label">More freshwater is stored in ice than is found in all other freshwater sources combined.</span> <div class="form-entry__option"> <div class="form-entry__option__radio" data-answer="correct"> <label> <input id="q1-6483-0-option-a" name="quiz-option-6483" type="radio" value="true" > <span class="option__label"> <span class="screen-reader-only">a.</span> true </span> </label> <span class="quiz__response" id="response-6483-0"> <strong>Correct!</strong> </span> </div> <div class="form-entry__option__radio" data-answer="incorrect"> <label> <input id="q1-6483-1-option-b" name="quiz-option-6483" type="radio" value="false" > <span class="option__label"> <span class="screen-reader-only">b.</span> false </span> </label> <span class="quiz__response" id="response-6483-1"> <strong>Incorrect.</strong> </span> </div> </div> </div> </div> </form> </div> </section> <section id="toc_2"> <h2>The ocean and the atmosphere</h2><p>Water moves constantly between these reservoirs through the processes of evaporation, <mark class="term" data-term="condensation" data-term-def="The process of forming a liquid from a gas." data-term-url="/en/glossary/view/condensation/8561">condensation</mark> and <mark class="term" data-term="precipitation" data-term-def="Water that falls from the atmosphere to the ground in any form, such as rain, snow, hail, or sleet." data-term-url="/en/glossary/view/precipitation/8562">precipitation</mark>, <mark class="term" data-term="surface" data-term-def="The outside or external part; the topside face of something." data-term-url="/en/glossary/view/surface/8275">surface</mark> and underground flow, and others. The driving force for the hydrologic cycle is the sun, which provides the <mark class="term" data-term="energy" data-term-def="An abstract property defined as the capacity to do work. The basic forms of energy include chemical, electrical, mechanical, nuclear, and&hellip;" data-term-url="/en/glossary/view/energy/1497">energy</mark> needed for evaporation just as the flame of a <mark class="term" data-term="gas" data-term-def="The state of matter characterized by its non-condensed nature and ability to flow. Unlike liquids, molecules within a gas remain far&hellip;" data-term-url="/en/glossary/view/gas/8725">gas</mark> stove provides the energy necessary to boil water and create steam. Water changes from a <mark class="term" data-term="liquid" data-term-def="The state of matter characterized by its condensed nature and ability to flow. Unlike gases, molecules within a liquid often experience&hellip;" data-term-url="/en/glossary/view/liquid/8727">liquid</mark> state to a gaseous state as it evaporates from the oceans, lakes, streams, and <mark class="term" data-term="soil" data-term-def="The loose top layer of Earth’s surface where plants grow, made up of particles of rocks, minerals, and organic material." data-term-url="/en/glossary/view/soil/8563">soil</mark> (see our <a href="/library/module_viewer.php?mid=57">Water: Properties and Behavior</a> module for a further explanation). Because the oceans are the largest reservoir of liquid water, that is where most evaporation occurs. The amount of water vapor in the air varies widely over time and from place to place; we feel these variations as humidity.</p><p>The presence of water vapor in the <mark class="term" data-term="atmosphere" data-term-def="The collective mass of gases that surrounds the Earth or another planet." data-term-url="/en/glossary/view/atmosphere/8529">atmosphere</mark> is one of the things that makes Earth livable for us. In 1859, Irish naturalist <mark class="term" data-term="John Tyndall" data-term-def="Irish physicist born at Leighlin Bridge, County Carlow (1820-1893). Tyndall was one of the first scientists to recognize the natural greenhouse&hellip;" data-term-url="/en/glossary/view/Tyndall%2C+John/4856">John Tyndall</mark> began studying the <mark class="term" data-term="thermal" data-term-def="Relating to heat." data-term-url="/en/glossary/view/thermal/8682">thermal</mark> properties of the gases in Earth's atmosphere. He found that some gases, like carbon dioxide (CO<sub>2</sub>) and water vapor, trap <mark class="term" data-term="heat" data-term-def="A measure of the total internal energy of a substance that can be increased or decreased when objects with different temperatures&hellip;" data-term-url="/en/glossary/view/heat/1506">heat</mark> in the atmosphere (a <mark class="term" data-term="property" data-term-def="A characteristic or attribute." data-term-url="/en/glossary/view/property/8555">property</mark> commonly called the greenhouse effect), while other gases like nitrogen (N<sub>2</sub>) and argon (Ar) allow heat to escape to space. The presence of water vapor in the atmosphere helps keep <mark class="term" data-term="surface" data-term-def="The outside or external part; the topside face of something." data-term-url="/en/glossary/view/surface/8275">surface</mark> air temperatures on Earth in a range from about -40° C to 55° C. Temperatures on planets without water vapor in the atmosphere, like Mars, stay as low as -100° C.</p><p>Once water vapor is in the air, it circulates within the <mark class="term" data-term="atmosphere" data-term-def="The collective mass of gases that surrounds the Earth or another planet." data-term-url="/en/glossary/view/atmosphere/8529">atmosphere</mark>. When an air package rises and cools, the water vapor condenses back to <mark class="term" data-term="liquid" data-term-def="The state of matter characterized by its condensed nature and ability to flow. Unlike gases, molecules within a liquid often experience&hellip;" data-term-url="/en/glossary/view/liquid/8727">liquid</mark> water around particulates like dust, called <em>condensation nuclei</em>. Initially these <mark class="term" data-term="condensation" data-term-def="The process of forming a liquid from a gas." data-term-url="/en/glossary/view/condensation/8561">condensation</mark> droplets are much smaller than raindrops and are not heavy enough to fall as <mark class="term" data-term="precipitation" data-term-def="Water that falls from the atmosphere to the ground in any form, such as rain, snow, hail, or sleet." data-term-url="/en/glossary/view/precipitation/8562">precipitation</mark>. These tiny water droplets create clouds. As the droplets continue to circulate within the clouds, they collide and form larger droplets, which eventually become heavy enough to fall as rain, snow, or hail. Though the amount of precipitation varies widely over Earth's <mark class="term" data-term="surface" data-term-def="The outside or external part; the topside face of something." data-term-url="/en/glossary/view/surface/8275">surface</mark>, evaporation and precipitation are globally balanced. In other words, if evaporation increases, precipitation also increases; rising global temperature is one factor that can cause a worldwide increase in evaporation from the world’s oceans, leading to higher overall precipitation.</p><p>Since oceans cover around 70% of Earth’s <mark class="term" data-term="surface" data-term-def="The outside or external part; the topside face of something." data-term-url="/en/glossary/view/surface/8275">surface</mark>, most <mark class="term" data-term="precipitation" data-term-def="Water that falls from the atmosphere to the ground in any form, such as rain, snow, hail, or sleet." data-term-url="/en/glossary/view/precipitation/8562">precipitation</mark> falls right back into the ocean and the cycle begins again. A portion of precipitation falls on land, however, and it takes one of several paths through the hydrologic cycle. Some water is taken up by <mark class="term" data-term="soil" data-term-def="The loose top layer of Earth’s surface where plants grow, made up of particles of rocks, minerals, and organic material." data-term-url="/en/glossary/view/soil/8563">soil</mark> and plants, some runs off into streams and lakes, some percolates into the <mark class="term" data-term="groundwater" data-term-def="Water that fills pore space in rocks and sediments and forms a subsurface aquifer. Groundwater is distinct from soil moisture, which&hellip;" data-term-url="/en/glossary/view/groundwater/2119">groundwater</mark> reservoir, and some falls on glaciers and accumulates as glacial ice.</p> <div class="comprehension-checkpoint margin-y-4"> <h6 class="comprehension-checkpoint__header"> <span> <span class="icon icon-question"></span> </span> Comprehension Checkpoint </h6> <form class="" name="cc6484"> <div class="form-entry"> <div class="form-entry__field"> <span class="form-entry__field__label">What drives the hydrologic cycle?</span> <div class="form-entry__option"> <div class="form-entry__option__radio" data-answer="incorrect"> <label> <input id="q1-6484-0-option-a" name="quiz-option-6484" type="radio" value="rain" > <span class="option__label"> <span class="screen-reader-only">a.</span> rain </span> </label> <span class="quiz__response" id="response-6484-0"> <strong>Incorrect.</strong> </span> </div> <div class="form-entry__option__radio" data-answer="correct"> <label> <input id="q1-6484-1-option-b" name="quiz-option-6484" type="radio" value="sun" > <span class="option__label"> <span class="screen-reader-only">b.</span> sun </span> </label> <span class="quiz__response" id="response-6484-1"> <strong>Correct!</strong> </span> </div> </div> </div> </div> </form> </div> </section> <section id="toc_3"> <h2>The hydrologic cycle on land</h2><p>The amount of <mark class="term" data-term="precipitation" data-term-def="Water that falls from the atmosphere to the ground in any form, such as rain, snow, hail, or sleet." data-term-url="/en/glossary/view/precipitation/8562">precipitation</mark> that soaks into the <mark class="term" data-term="soil" data-term-def="The loose top layer of Earth’s surface where plants grow, made up of particles of rocks, minerals, and organic material." data-term-url="/en/glossary/view/soil/8563">soil</mark> depends on several factors: the amount and intensity of the precipitation, the prior condition of the soil, the slope of the <mark class="term" data-term="landscape" data-term-def="The natural scenery of a region; a collection of landforms in an area." data-term-url="/en/glossary/view/landscape/8559">landscape</mark>, and the presence of vegetation. These factors can interact in sometimes surprising ways – a very intense rainfall onto very dry soil, typical of the desert southwest, often will not soak into the ground at all, creating flash-flood conditions. Water that does soak in becomes available to plants through soil moisture and <mark class="term" data-term="groundwater" data-term-def="Water that fills pore space in rocks and sediments and forms a subsurface aquifer. Groundwater is distinct from soil moisture, which&hellip;" data-term-url="/en/glossary/view/groundwater/2119">groundwater</mark> (see Figure 2). Plants take up water through their root <mark class="term" data-term="system" data-term-def="A group of interacting, interrelated or interdependent components that form a complex whole. The size of the system is defined for&hellip;" data-term-url="/en/glossary/view/system/3904">systems</mark>, which mostly draw water from soil moisture; the water is then pulled up through all parts of the plant and evaporates from the <mark class="term" data-term="surface" data-term-def="The outside or external part; the topside face of something." data-term-url="/en/glossary/view/surface/8275">surface</mark> of the leaves, a <mark class="term" data-term="process" data-term-def="Method, procedure; series of actions or steps." data-term-url="/en/glossary/view/process/8256">process</mark> called <em>transpiration</em>. Water that soaks into the soil can also continue to percolate down through the soil profile below the water table into groundwater reservoirs, called <em>aquifers</em>. <mark class="term" data-term="aquifer" data-term-def="A porous and permeable body of rock or sediment through which groundwater flows." data-term-url="/en/glossary/view/aquifer/2117">Aquifers</mark> are often mistakenly visualized as great underground lakes; in reality, groundwater saturates the pore spaces within <mark class="term" data-term="sediment" data-term-def="Loose, unconsolidated material of the following compositions: <br> 1. rock fragments (also called clasts) transported by wind, moving water,&hellip;" data-term-url="/en/glossary/view/sediment/3310">sediments</mark> or rocks (see Figure 2).</p> <div class="figure"> <figure> <button class="lightbox-button lightbox-button--icon" data-lightbox=""> <img src="/img/library/modules/mid99/Image/VLObject-2093-030817050807.gif" alt="Figure 2: Groundwater exists below the water table, which divides unsaturated soil, rock, and sediments from saturated." /> </button> <figcaption> <p><strong>Figure 2:</strong> Groundwater exists below the water table, which divides unsaturated soil, rock, and sediments from saturated.</p> </figcaption> </figure> </div> <p>Water that doesn’t soak into the <mark class="term" data-term="soil" data-term-def="The loose top layer of Earth’s surface where plants grow, made up of particles of rocks, minerals, and organic material." data-term-url="/en/glossary/view/soil/8563">soil</mark> collects and moves across the <mark class="term" data-term="surface" data-term-def="The outside or external part; the topside face of something." data-term-url="/en/glossary/view/surface/8275">surface</mark> as <em>runoff</em>, eventually flowing into streams and rivers to get back to the ocean. <mark class="term" data-term="precipitation" data-term-def="Water that falls from the atmosphere to the ground in any form, such as rain, snow, hail, or sleet." data-term-url="/en/glossary/view/precipitation/8562">Precipitation</mark> that falls as snow in glacial regions takes a somewhat different journey through the water cycle, accumulating at the head of glaciers and causing them to flow slowly down valleys.</p> <div class="comprehension-checkpoint margin-y-4"> <h6 class="comprehension-checkpoint__header"> <span> <span class="icon icon-question"></span> </span> Comprehension Checkpoint </h6> <form class="" name="cc6485"> <div class="form-entry"> <div class="form-entry__field"> <span class="form-entry__field__label">Flash-flooding can result from intense rainfall</span> <div class="form-entry__option"> <div class="form-entry__option__radio" data-answer="incorrect"> <label> <input id="q1-6485-0-option-a" name="quiz-option-6485" type="radio" value="into lakes that already have a high water level." > <span class="option__label"> <span class="screen-reader-only">a.</span> into lakes that already have a high water level. </span> </label> <span class="quiz__response" id="response-6485-0"> <strong>Incorrect.</strong> </span> </div> <div class="form-entry__option__radio" data-answer="correct"> <label> <input id="q1-6485-1-option-b" name="quiz-option-6485" type="radio" value="onto soil that is very dry." > <span class="option__label"> <span class="screen-reader-only">b.</span> onto soil that is very dry. </span> </label> <span class="quiz__response" id="response-6485-1"> <strong>Correct!</strong> </span> </div> </div> </div> </div> </form> </div> </section> <section id="toc_4"> <h2>Humans and the hydrologic cycle</h2><p>The properties of water and the hydrologic cycle are largely responsible for the <mark class="term" data-term="circulation" data-term-def="Generally, movement within a system. 1. [Atmospheric] the movement of air masses within the troposphere, driven by the redistribution of energy&hellip;" data-term-url="/en/glossary/view/circulation/10355">circulation</mark> patterns we see in the <mark class="term" data-term="atmosphere" data-term-def="The collective mass of gases that surrounds the Earth or another planet." data-term-url="/en/glossary/view/atmosphere/8529">atmosphere</mark> and the oceans on Earth. Atmospheric and oceanic circulation are two of the major factors that determine the distribution of climatic zones over the Earth. Changes in the cycle or circulation can result in major climatic shifts. For example, if <mark class="term" data-term="average" data-term-def="In statistics, average commonly refers to the arithmetic mean, also called simply "mean," which is one measure of the mid-point of&hellip;" data-term-url="/en/glossary/view/average/8542">average</mark> global temperatures continue to increase as they have in recent decades, water that is currently trapped as ice in the <mark class="term" data-term="polar" data-term-def="Carrying an electrical charge." data-term-url="/en/glossary/view/polar/8730">polar</mark> ice sheets will melt, causing a rise in sea level. Water also expands as it gets warmer, further exacerbating sea level rise. Many heavily populated coastal areas like New Orleans, Miami, and Bangladesh will be inundated by a mere 1.5 meter increase in sea level (see Figure 3). Additionally, the <mark class="term" data-term="acceleration" data-term-def="The change in an object's velocity over time, measured in distance per unit time per unit time (for example meters per&hellip;" data-term-url="/en/glossary/view/acceleration/5595">acceleration</mark> of the hydrologic cycle (higher temperatures mean more evaporation and thus more precipitation) may result in more severe weather and extreme conditions. Some scientists believe that the increased frequency and severity of <mark class="term" data-term="El Niño-Southern Oscillation" data-term-url="/en/glossary/view/El+Ni%C3%B1o~Southern+Oscillation" data-term-def="A 2- to 7-year climatic cycle in the Tropical Pacific. In El Niño years, the trade winds die down, leading to&hellip;">El Niño</mark> events in recent decades is due to the acceleration of the hydrologic cycle induced by global warming.</p> <div class="figure"> <figure> <button class="lightbox-button lightbox-button--icon" data-lightbox=""> <img src="/img/library/modules/mid99/Image/VLObject-2639-031218011230.gif" alt="Figure 3: Areas in red would be flooded with a 1.5 m rise in sea level; areas in blue would be flooded by a 3.5 m rise in sea level. Image has been modified from the original from the US Environmental Protection Agency (EPA)." /> </button> <figcaption> <p><strong>Figure 3:</strong> Areas in red would be flooded with a 1.5 m rise in sea level; areas in blue would be flooded by a 3.5 m rise in sea level. Image has been modified from the original from the US Environmental Protection Agency (EPA).</p> </figcaption> </figure> </div> <p>Even more immediately, the finitude of Earth’s freshwater resources is becoming more and more apparent. <mark class="term" data-term="groundwater" data-term-def="Water that fills pore space in rocks and sediments and forms a subsurface aquifer. Groundwater is distinct from soil moisture, which&hellip;" data-term-url="/en/glossary/view/groundwater/2119">Groundwater</mark> can take thousands or millions of years to recharge naturally, and we are using these resources far faster than they are being replenished. The water table in the Ogallala <mark class="term" data-term="aquifer" data-term-def="A porous and permeable body of rock or sediment through which groundwater flows." data-term-url="/en/glossary/view/aquifer/2117">Aquifer</mark>, which underlies 175,000 square miles of the US from Texas to South Dakota, is dropping at a rate of 10-60 cm per year due to extraction for irrigation. <mark class="term" data-term="surface" data-term-def="The outside or external part; the topside face of something." data-term-url="/en/glossary/view/surface/8275">Surface</mark> waters around the world are largely contaminated by human and animal waste, most noticeably in countries like India and China, where untreated rivers provide the drinking and washing water for nearly 2 billion people. Although legislation like the Clean Water Act in the United States and water <mark class="term" data-term="conservation" data-term-def="Careful use of natural resources to minimize waste or damage to the natural world and to maintain natural resources for long-term&hellip;" data-term-url="/en/glossary/view/conservation/5592">conservation</mark> practices such as the use of low-flow toilets and showerheads in parts of the world has begun to address these issues, the problems will only grow as world population increases. Every spring and well, every river and sea does indeed flow from the same source, and changes affect not just one river or lake, but the whole hydrologic cycle.</p> </div> </section> <hr class="border-color-dark" /> <footer class="module__footer"> <p class="citation"> <em> Anne E. Egger, Ph.D. “The Hydrologic Cycle” Visionlearning Vol. EAS-2 (2), 2003. </em> </p>  <div class="title-list" name="further"> <p class="h6 title-list__title"> Further Reading </p> <ul class="grid grid--column-2--md grid--column-3--md gap-1"> <li> <a class="no-hover-focus height-100" href="/en/library/Chemistry/1/Water/267"> <article class="flex-row align-items-center flex-column--md align-items-start--md height-100 theme-light padding-2 gap-2"> <div class="width-30 width-auto--md"> <img class="border-radius box-shadow-1" src="/img/library/moduleImages/featured_image_267-23061209064844.jpg" alt="Water"> </div> <div class="flex-grow-shrink"> <h2 class="h6 font-weight-normal"> Water: <em>Properties and behavior</em> </h2> </div> </article> </a> </li> </ul> </div> </footer> </div>   </div>  <div class="order-1 order-2--lg module__tools"> <div class="narrow margin-x-auto position-sticky-top font-size-md"> <div class="padding-2 border-radius box-shadow-1--lg"> <div class="tabs" role="tablist"> <nav> <button class="button button--icon-label" id="tab-button-in-this-module" aria-label="Table of Contents" aria-controls="tab-panel-module__tools" aria-selected="true" role="tab"> <span class="icon icon-list" aria-hidden="true"></span> <span class="button__text">Contents</span> </button> <button class="button button--icon-label" id="tab-button-toggle-terms" aria-controls="tab-panel-toggle-terms" aria-selected="false" role="tab"> <span class="icon icon-glossary-highlight"></span> <span class="button__text">Glossary Terms</span> </button> </nav> <hr class="divider" /> <div class="tabs__panel shown" id="tab-panel-module__tools" aria-labelledby="tab-button-module__tools" role="tabpanel"> <p class="font-weight-bold margin-bottom-1"> Table of Contents </p> <div class="table-of-contents" id="module-toc"> <ul> <li><a href="/en/library/earth-science/6/the-hydrologic-cycle/99#toc_1">Hydrologic cycle</a> </li> <li><a href="/en/library/earth-science/6/the-hydrologic-cycle/99#toc_2">The ocean and the atmosphere</a> </li> <li><a href="/en/library/earth-science/6/the-hydrologic-cycle/99#toc_3">The hydrologic cycle on land</a> </li> <li><a href="/en/library/earth-science/6/the-hydrologic-cycle/99#toc_4">Humans and the hydrologic cycle</a> </li> </ul> </div> </div>   <div class="tabs__panel" id="tab-panel-toggle-terms" aria-labelledby="tab-button-toggle-terms" role="tabpanel"> <div class="reading-toggle"> <div class="reading-toggle__switch"> <div class="form-entry__option__switch"> <label> <input type="checkbox" name="termsToggleSwitch" id="terms-toggle-switch" /> <span class="switch__slider"></span> <span class="option__label text-decoration-none font-size-md"> Highlight Glossary Terms </span> </label> </div> </div> <div class="reading-toggle__help"> <p> <em> Activate glossary term highlighting to easily identify key terms within the module. 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The Hydrologic Cycle | Earth Science | Visionlearning