Outline & notes for water lecture #2Envir202b – Earth, Air, Water: the Human Context – Winter 2003 – F. StahrOutline & notes for water lecture #2“Earth, Air, Water, Fire” almost title of course – from Greeks ~500BC – all other materials fromthese 4 transmutable ones (changeable). Many properties of water (especially liquid water) arestill incompletely understood. But we know that it’s a main constituent of life as we know it onEarth, and critical to the rise of humans as primary species on planet. (See first lecture forproperites of water, distribution on planet, hydrologic cycle, and ocean circulation.)“Water, water everywhere, nor any drop to drink.” – Coleridge, Rime of the Ancient MarinerWritten on ocean, but also applies to not enough safe fresh to drink or raise crops with.1) Hypothesis: Without irrigation for agriculture, humans would not be dominant on planet.A. Evidence: all great ancient civ’s did it and some died for lack of sustainability: Summariansaround Tigris/Euphartes, Egyptians, Chinese, Greeks, Romans (as good for Rome as istoday), Mayans (demise still mystery, but leading theory is overstreched water supply systemand intense drought), Tihuanaco (altoplano –Peru/Bolivia, likewise extensive drought)B. history and current situation stacked against us:i. Sandra Postel, Pillar of Sand: Can the Irrigation Miracle Last?, “The overriding lessonfrom history is that most irrigation-based civilizations fail.”ii. most world food from cropland, rangeland, fisheries; latter suffering badly fromoverfishing, rangeland down 20% due to overgrazing, cropland critical (J. Leslie,Harper’s mag, 7/2000)iii. projections from Science articles – review at end.2) Supply side effectively fixed by hydrologic cycle and climate stateA. Lakes, rivers, glaciers, groundwater, ancient aquafers, (see lecture #1 data)B. Therefore people fight over it:i. Aral sea(lake) rivers (Amu Drya, Syr Drya) – <1960 55km3/yr, now <5km3 intolake, Afghanistan/Uzbekistan/Turkmenistan – to cotton growing in 60s – almostno sea left (1/3 size), 48000 tons/yr fishing gone, air-borne salt killing cotton,salinity up 3x, “will be salt pan size of Ireland”, changed regional climate, forestgone, ½ mammal species gone, ¾ bird species gone, all native fish species goneii. India v. Pakistan – Indus river agreement in 60’siii. Israel/Palestine v. Jordan - Jordan river: 40% to Israel/Palestine, of which 80% to130k Israelis, 20% to ~2M Palestiniansiv. Turkey v. Iraq v. Syria – Tigris/Euphrates – headwaters all in Turkey, takes most;Iraq just drained most of wetlands at lower end, now native marsh populations(both flora, fauna and people) homelessv. Maryland v. Virginia – US Supreme court- Mon NYTimesvi. Colorado, New Mexico, Arizona, California, Mexico (7 states + Mexico)– splitbased on very wet 18 years, so most often not enough in river…feedingLasVegas, Phoenix, LA, all cropsC. Deep groundwater supplies very threatened. Constitute ~60x what’s in lakes, etc.i. Ogallala Aquifer 225,000 sq mi, feeds 1/5 irrigated US, going down 3-10m/yrii. India, draining at 2x recharge rate,iii. Land sinking under – Beijing ~10cm/yr, Mexico City ~30cm/yr, iv. sea water invasion Florida, pollution invasionD. Dams – can’t live without, but now some can’t live with.i. great decades of it in 1950-90 (see EOS article), Hoover dam 1935, Aswan1971ii. serves ~ 1/5 power, and high % of irrigation wateriii. 3 gorges in China will be largest, largely political willpower, typical sed fillrate ~2.3%/yriv. stop most of largest rivers from reaching sea: Nile, Colorado, Yellow,Mississippi,3) UsesA. People use/consume ~26% of evapotranspiration and 54% of runoff accessibleB. Split of use was ~90% agriculture irrigation, 10% industry and muni, now ~65/25/10(McNeill tables as graphs, also Scientific American fig pg. 42)C. In last 200yrs, increased area irrigated 30x, population risen by 6x, however, still less than1/5 agricultural area irrigated, but produces 2/5 of world food, (see McNeill Table 6.2 asgraphic)D. Irrigation caused Green Revolution ~1960s, plus fertilizing and pesticides, see agriE. Translation of water to grain, ~1#:1000#, except in dry, eg. Saudia Arabia 1980s ~1:3000,grain imports are form of water import, grain-fed beef add factor of ~100F. Since 1996, land spoiled by salinization, etc. as fast as irrigated…no net gain.G. Many ways to save in municipal use – e.g. NYC toilets, replaced ~1.3 M, 29% reduction,saves 70-90 Mgal/day w/~$300M investment (cheaper by 1/3 than new pumping system),saved another ~11Mgal/day by fixing leaks.4) Health & ecology issuesA) water borne diseases up: malaria, typhoid, cholera, schistosomiasis (Egypt –Nile dams) (seealso http://www.worldwater.org/table22.htm and http://www.worldwater.org/table13.htm;cancer, hepititass and typhoid fever very high around remnant of Aral sea,B) access to clean water down (see http://www.worldwater.org/table7.htm,http://www.worldwater.org/table8.html)C) Cutting of Suez between Red Sea and Med was ok when salinity very different, but withNile dammed, now salinity of eastern Med much higher, Red Sea species can migratesuccessfully, changing east-Med marine eco-systemsD) Dead zone in Gulf of Mexico due to Mississippi nutrient loading ->high plankton ->highbacteria -> use all oxygen at depth -> no fish or other animals survive: seasonal, but growinglarger ~20,000 sq km.5) Future not greatA) population projected to rise by 50% (~ 9 billion by 2025), but can tap only another 10%runoff (Postel, Science), seeB) most rain-fed areas already in agricultural production, will need 10^9 hectares converted tomore agriculture (>size of US), will add ~2.5x nutrients & therefore eutrophication of waterecosystems (like GoM/Mississippi)C) drought situation not good, but human population will be bigger driver than climate change –see projections from Vorosmarty et al, Science 289, July