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The Water Cycle… from clouds to sea.. from sea to clouds… The hydrologic cycle: Water cycle as an active model • Active processes – Precipitation events: rain, fog, mist, snow – Infiltration and ground and surface water flow events – eventual discharge into creeks and rivers – root adsorption – Water enters back into the atmosphere in the form of water vapor – Vapors condense, form clouds, and result in another precipitation event Animation from: http://www.nps.gov/olym/hand/process/wcycle.gif The Water Cycle on the Coast…. from sea to land …….. is a microcosm of the global cycle http://www.hko.gov.hk/education/edu01met/wxphe/ele_fog_fig2e.png The Water Cycle Globally Outline: 1. Reservoirs 2. Movement among reservoirs 3. Storage and “Residence time” in a reservoir 4. Water and climate change Outline: 1. Reservoirs 2. Movement among reservoirs 3. Storage and “Residence time” in a reservoir A Simple overview of the hydrologic cycle Ocean Storage What percent of Earth’s water is stored in the oceans? Does the volume of the world’s oceans ever change? 20,000 years ago: LOWER Sea level ~400 ft lower ) than today 120,000 years ago: HIGHER Sea level 18 ft higher than today 3M years B.P.: HIGHER Sea level 165 ft higher ICE AND SNOW: glaciers, ice fields, and snowfields How much of all freshwater? • Glacial ice covers 11% of all land • Represents a large % of all freshwater • Mountain snowfields are “reservoirs” for many water-supply systems – 75% in Western States How much ground water? • Ground water occurs only close to the surface Surface Water: Lakes & Swamps & Rivers • Lakes swamps account for less than 0.3% of all fresswater: - 20% is in the Great Lakes - 20% is in Lake Baikal in Siberia Storage in the atmosphere: • 0.001% • Water vapor • Clouds, condensed water vapor http://www.cs.cmu.edu/afs/andrew/scs/cs/15463/f07/proj2/www/aaiordac/images/clouds.jpg Distribution of Earth’s Water Outline: 1. Reservoirs 2. Movement among reservoirs 3. Storage in a reservoir 4. Water and climate change 5. Environmental frameworks The hydrologic cycle: Active model •http://www.in.gov/idem/water/kids/waterpix/watercycleimage2.gif Processes moving water through the cycle… key Atmosphere Transport What percent of the water in the atmosphere comes from evaporation? •Evaporation 90% •Transpiration 10% Subsurface Water movement Outline: 1. Reservoirs 2. Movement among reservoirs 3. Storage in a reservoir 4. Water and climate change 5. Environmental frameworks Mass Balance: Storage, a consequence of movements Generally: Inflow (I) – Outflow (O) = Net balance Globally, we turn this around:: Outflow (O) – Inflow (I) = Net balance Evaporation (E) - Precipitation (P) E – P = Net Balance (Also called the continuity equation, conservation of mass.) GLOBAL NET WATER BALANCE mm/day Tropics: Subtropics: Convergence Divergence Evaporation Precipitation Evap-Precip Latitude High Latitude: Convergence Mass Balance: Storage, a consequence of movements When thinking on a local scale of land use: Inflow (I) – Outflow (O) = ± Change in storage (S) I - O = ± ∆S (Also called the continuity equation, Lake Mead: May, 2000 26 26 Source: NASA Earth Observatory Lake Mead: May, 2003 27 27 Source: NASA Earth Observatory Outline: 1. Reservoirs 2. Movement among reservoirs 3. Storage in a reservoir 4. Limitations: Water and climate Climate Change: Increases Water Vapor in the atmosphere 8 Vapor Pressure (kPa) 7 6 5 4 3 Atmosphere can hold more water 2 1 0 -20 -10 0 10 20 30 40 o Temperature ( C) 29 29 Source: Chow et al., 1988 Climate Change: water balance • Evaporation (E) Evaporation – generally increases across the Earth • Precipitation (P) – more locations specific, increases and decreases • Runoff/recharge (P-E) Runoff CRB Model predictions of change in runoff Precipitation for double CO2 concentrations. 30 Source: Held and Soden, 2006 Climate Change – Runoff • Precipitation trends controlled by wind circulation • Trends intensify due to climate change: – dry areas become drier – wet areas become wetter 31 Source: Maidment CE 394K.2 class notes, 2008 Climate Change: Modeled runoff Annual average of change in runoff compared to the global modeling average. Source: Milly et al., 2008 Climate Change: Water Vapor • The atmosphere can “hold more water vapor” at higher temperatures • This produces more clouds, which can act to both warming • Therefore, increased water vapor in the atmosphere will further act to increase surface temperature and evaporation • This will further increase atmospheric water vapor concentrations • BUT, same amount of water, redistributed in reservoirs 33 Outline: 1. Reservoirs 2. Movement among reservoirs 3. Storage in a reservoir 4. Water and climate change 5. Environmental framework A framework for thinking about water issues quantity direct human health environment quality The example of Grazing Public supply, 11% Domestic, >1% Agriculture, 36% Industrial, 5% Mining, >1% Thermoelectric, 48% from USGS, 2000 A breakdown of water use in the US, consumptive + returned US water withdrawals and consumptive use, 1960-95 Consumptive use vs. renewable water supply 1995 USGS Irrigation in the US Total withdrawals, 2000 USGS Water use in Illinois 1950-1998, excluding power generation Illinois State Water Survey Regional changes in storage 1996-7 The Ogallala, the largest freshwater aquifer in the world. Saturated thickness 1980-1997 Teleconnections in the hydrologic cycle 4 before after 2 Jan Jul Precip, mm/yr Regional to global effects on precipitation: model results from deforesting Amazonia 0 Dec Forests Grasslands 8 before after 4 Jan Jul Precip, mm/yr Croplands 0 Dec Avissar and Werth (2004), Journal of Hydrometeorology Hydrological Cycle http://watercycle.gsfc.nasa.gov/