This slide shows paired satellite images before and after the Dec 26, 2004 earthquake. The area shown is a portion of Banda Aceh at the northern end of Sumatra. The important point is that the land surface in this area (and along a very large area of the upper plate of this subduction zone) dropped by several meters during the earthquake. This is called “coseismic subsidence”. This coseismic subsidence also occurred during the great Cascadia earthquake of 1700 when forests close to the shore subsided into the intertidal zone killing the trees and producing “ghost forests”.
Oregon’s Place in Water World Bob Butler Environmental Sciences University of Portland
H 2 O molecular structure Two hydrogen (H) and one oxygen (O) atoms bonded by sharing electrons. Both H atoms on same side of O atom. A polar molecule: O side has - charge H 2 side has + charge Water Is Weird and Wonderful
Water Is a Strong Solvent Good news: Can carry nutrients in solution. Bad news: Carries pollutants in solution.
<ul><li>Fresh water is only 2.5% of Earth’s water. </li></ul><ul><li>Fresh water = 2/3 ice + ~1/3 groundwater </li></ul><ul><li>Only 0.3 % of freshwater in lakes and rivers! </li></ul>Where Is the Water?
Pleistocene Ice Sheets 20,000 years ago, Canada was under a mile of ice. Pacific Northwest was at the southern edge of the ice sheet.
20,000 years ago, sea level was at ice-age coastline. If all ice melts, Memphis has beachfront properties. Glacial and Interglacial Coastlines
Glacial-Interglacial Changes in Sea Level Sea level rose 20 cm during the last century. AT LEAST another 30 cm sea level rise by 2100 from warming ocean. The wild card is melting of ice sheets. (e.g. Melting all Greenland ice would raise sea level about 7 meters.) It would be wise to plan for 2 meters of sea level rise by 2100. Effects: (1) Rising sea level increases coastal erosion. (2) Lower Columbia and Willamette Rivers will also rise with sea level.
The Coastal Environment <ul><li>A beach is a river of sand. </li></ul><ul><li>You don’t own the sand on your beach. You just rent it. </li></ul>Input of sediment from rivers and coastal erosion. Output to deep ocean through submarine canyons. Dam building has diminished input of sediment by rivers resulting in increased coastal erosion. Input Input Output
Jump-Off Joe at Nye Beach, Newport 1880 1915 1978
Sea Level in Normal & El Ni ño Years Yearly sea level oscillation is equivalent to rise in sea level over the past century. Rise in sea level during El Ni ño years is equivalent to one-half of sea level rise over the coming century. Average normal year 1982 - 83 El Ni ño
Ocean Shores, WA, west of Gray’s Harbor October, 1997 April, 1998 Cape Shoalwater, WA, north of Willapa Bay
Siletz Spit, South of Lincoln City Never buy a house built on sand. Sand spits are vulnerable to erosion by sea and by river.
Wave Energy in Pacific Ocean <ul><li>Explanation </li></ul>Increasing wave energy
Before After Some areas dropped 2 – 3 meters during the M9.2 Sumatra – Andaman Islands earthquake of December 26, 2004. This also happened along the Washington - Oregon coast during the 1700 AD great Cascadia earthquake. Will the next Cascadia great earthquake be the Hurricane Katrina for the Pacific Northwest? Banda Aceh, Sumatra Satellite Images Indicate Land Subsidence
Glacial Lake Missoula Floods Humongous floods (12,000 to 16,000 years ago) imported rich glacial sediment to the Willamette Valley and Portland Basin.
Video: Oregon Field Guide Glacial Lake Missoula (Humongous) Floods Thanks to Jon Kin, OPB
Missoula Floods Sediments <ul><li>High porosity and permeability = Very good aquifer. </li></ul>From Jim O’Connor, USGS
<ul><li>Portland Basin Glacial and Fluvial Sediment </li></ul>Missoula Floods Sediment Troutdale Gravels From Dave Morgan, USGS
Pacific Northwest Regional Floods February 5-9, 1996: Above average Cascade snowpack. Subtropical humid air mass brought record rainfalls (28” at Laurel Mountain in Coast Range). High freezing level caused massive snow melt. Formula for Pacific Northwest regional flood: SNOW + PINEAPPLE = FLOOD. record record record record record
1996 Flooding Along Willamette River The Willamette Flowing over Highway 34 east of Corvallis. Widespread flooding in Willamette Valley. OMSI building (on Water Avenue!) on waterfront flooded. Downtown Portland narrowly escaped flooding.
“ Local” Floods From Brief But Intense Storms e.g. November 2006 & December 2007 Hwy 35 Mt Hood to Hood River
December 2007 Hydrographs Normal = 200 cfs Peak = 13,000 cfs 65 times normal flow!! Normal = 30,000 cfs Peak = 110,000 cfs 3.7 times normal flow. December 2007 Hydrographs Vernonia Newberg
Chehalis River December 2007 I-5 closed for several days.
Water Resources <ul><li>Abundant precipitation in Pacific Northwest. </li></ul>
Variations in Precipitation <ul><li>Monthly precipitation varies by factor of 8. </li></ul>
Variations in Demand Demand varies by factor of two and is out of phase with precipitation. Watershed management is critical. M G D Jan Feb Mar Apr May June July Aug Sept Oct Nov Dec
Watershed Inputs and Outputs <ul><li>Surface water and groundwater are one resource. </li></ul>
Portland’s Water System <ul><li>Explanation </li></ul>Careful planning in late 1800s. Impressive engineering (gravity-fed system). Columbia South Shore Well Field: Groundwater backup and summer supplement.
Groundwater – Surface Water <ul><li>CSSWF can pull water out of the Columbia River. </li></ul>
Regional Water Supply Challenges <ul><li>Longer and warmer dry periods. </li></ul>Temperature change 1920 - 2000
Decreasing Snowpack April 1 snow water equivalent (1950 – 2000)
Observations on Water and Justice Many cultures struggling with water resource issues. Peace Corps workers involved in construction of village water supply systems (Bolivia, Nepal, Ethiopia). Bob’s field locations.
Afar of Ethiopia <ul><li>Explanation </li></ul>Observations on Water and Justice. Tribal war over dwindling water supply .
<ul><li>“ We are water – the oceans flow through our veins, and our cells are inflated by water, our metabolic reactions mediated in aqueous solutions …… As air is a sacred gas, so is water a sacred liquid that links us to all the oceans of the world and ties us back in time to the very birthplace of all life … It is the tide of life itself, the sacred source.” David Suzuki in The Sacred Balance </li></ul>Confluences: Water and Justice