Presentation on theme: "Today’s Questions What is the water or hydrological cycle? What causes floods? Who cares about snow and ice? What is an impervious surface and what does."— Presentation transcript:
Today’s Questions What is the water or hydrological cycle? What causes floods? Who cares about snow and ice? What is an impervious surface and what does it do water? Are there alternatives to traditional ways of handling urban water?
Review Monday System definition, illustration Biogeochemical Cycles Carbon cycle - Farm tour (this Thursday and next Tuesday) –Decomposition (C - cycle, detritus part of food chains, foods webs) –Food security –Invasive plants –Farming practices: organic, sustainable –Urban agriculture - sustainable cities
Question: Photosynthesis is a flux or a pool? 1.Flux 2.Pool 3.Both
Biogeochemical Cycles - 2 1.1. Focus on the Water Cycle: 2.Issue of water supply: now, future 3.Understanding the behavior of water in streams (floods, power, salmon) 4.Three case studies a)Floods PNW Pakistan flood of 2010 and US floods 2011 b)Snow and ice (mountain glaciers) c)Urban Watersheds
Water security, supply or scarcity has become a major topic because (pick incorrect answer) 1.World’s population has increased 2.As wealth increases, consumption of meat decreases 3.Agriculture depends increasingly on irrigation. 4.Glaciers and snow coverage is decreasing.
Water Cycle Learning about stream flow Three cases –Floods Washington Pakistan –Role of snow & glaciers globally –Urban watershed http://ga.water.usgs.gov/edu/watercyclesummary.html
Quantities of Water Takehome Message: Lots of water! Not much fresh Not much clean fresh Water quantity is variable!!
Water Scarcity Article in the Economist (& the NAS YouTube Video) emphasized: –Importance of having enough, clean water at the right time Problems –Too much or not enough –Polluted (http://www.fic.nih.gov/News/Pages/2011- climate-change-diarrheal.aspx) –Conflicting uses Key: understand how water and watersheds behave
Stream Behavior & Floods (#1) (1) Floods in Washington State (2) Floods in Pakistan (2010) (3) Floods in US (2011) Anatomy of environmental events of 2010 - 2011 http://www.klimadiagramme.de/ http://www.klimadiagramme.de/ http://en.wikipedia.org/wiki/Pakistan
Understand the behavior of a watershed http://waterdata.usgs.gov/wa/nwis/rt
Behavior of Water in a Watershed Use of a hydrograph (stream gauge) Forest Urban 0 Time 12 hours DischargeRain 0 Lots 0 Peak Flow Base Flow % impervious surface
Floods on the Snoqualmie River Nov 24, 1990 Jan 9, 2009 78,800 cfs 61,100 cfs
Summary: River Behavior Low elevation, coastal mountains: September low Nov - Feb high Spikes with big rain events High elevation, Cascade mountains: September low Nov - Dec high Jan - Feb low May - June high Spikes: Rain on snow Interior mountains: September low May - July high
Floods: Reasons Changes in precipitation due to climate change –Average increases slightly (warmer air holds more water –Increased intensity Rain-on-snow –Role of clearcuts & young forests River system –Land use changes –% impervious surface –River channel itself Removal of beavers Removal of structure (coarse woody debris) Channelization
Case # 2: Glaciers and Snow Example of a positive feedback as snow and ice melts from warming, more radiation is absorbed (vs. reflected [albedo effect]): positive feedback. One of the most reliable indicators of climate change Have a major influence on water availability. North and South America, Europe, Asia
Glacier National ParkAustrian Alps 1913 2005 150 to 26 http://www.msnbc.msn.com/id/6903014
Last 1000 years Medieval Optimum Little Ice Age 1oC1oC
Glaciers - Water Security Water towers of the mountains Supply water directly or indirectly to billions of people Like aquifers, humans have been living on capital for the last 100 plus years. Demand for water –Population –Agriculture –Switch from eating cereals to things eating cereals.
Take-home messages for PNW Decreased snow packs Biggest decreases, lower elevations Big decreases in PNW Snow melts earlier in the spring Shifts in timing of runoff Impacts on summer water Increasing demands & uses of water Glaciers, permanent snow fields and snow pack are the ‘water towers’ of the mountains
In your view, which alternative seems the most viable 1.Using cisterns (tanks) to collect runoff 2.Requiring green roofs 3.Using the S.E.A.- Street model 4.All three
Major (Climate) Change Issues Quantity of water (+ in form of snow, ice) Loss of mountain snow and ice Seasonal and spatial distribution Rainfall intensities Loss of forests and vegetation Increases in impervious surfaces Demand for fresh, clean water Premise: Clean, fresh water is a rare resource
Summary: Water Cycle Water cycle: Quantity, Quality, Form, & Timing Watershed - definition, behavior Climate, weather and watershed properties Three cases –Floods –World-wide glaciers (Himalayas) –Urban Watersheds