Notes 11/17 Assignment 2: due Tuesday Nov 22

Transcription

1 Notes 11/17 Assignment 2: due Tuesday Nov 22 eature=related 1 Final Exam Comprehensive Question: Comprehensive integration (50 pts): Imagine yourself as a content advisor to Tucson's Rio Nuevo Project, which has the goal of educating citizens about environment-human issues of the Southwest. Choose a modern Southwest environment-human issue from Part 3 of our course that you think should be included in museum displays and exhibits. For this issue: Explain why it is important currently. Describe a historic or prehistoric example of the issue (from our Part 2). Describe the environmental background to the issue (from our Part 1). Answer this three times using different issues (lectures) each time. The Geos. 220 course lecture topics are below. Don't be redundant, i.e., don't use any lecture topic more than once Typed, single-spaced; ½-page for each answer Due 6, 2010 bring to last exam period. Today s topic: Water in the Southwest Water stats & cycling Groundwater Subsidence Colorado River Required Reading: General reading: Cadillac Desert (book o Day) 3 1

2 Water Information at UA Water Resources Research Center (WRRC) Campbell, just south of 6th Free Newsletters Arroyo Arizona Water Resource Xeriscaping 4 5 Water water everywhere, not a drop to drink 96% of Earth s water is salty 74% of Earth s fresh water is frozen 99% of Earth s fresh liquid water is underground 6 2

3 Water Cycle Units: 1000 km 3 /yr (0.26 mill-bill gallons/yr) Oceans: 85% evaporation, 79% precipitation Fresh water: surface, subsurface, or evap

4 Where do we get our Water? Groundwater Wells into aquifers Surface Water Reservoirs & streamflow Water harvesting Small scale homeowners (not for drinking) 10 What Is An Aquifer? water table aquifer bedrock Aquifer - sands with water filling the pore spaces between the grains 11 Basin Fill Depth can be several thousand feet Washed down throughout eons of erosion Filled in with water Pleistocene water Borrowing water from time. 12 4

5 Tucson Wells Annual Groundwater Budget Tucson Active Management Area Inflow +167,000 ac-ft Natural and Incidental Recharge, Groundwater Inflow Outflow - 330,000 ac-ft Municipal, Agricultural and Industrial Pumpage, Groundwater Outflow Balance (OVERDRAFT) -163,000 ac-ft Acre-foot: water 1 foot deep covering 1 acre (43,560 ft 2 ) = 325,851 gal. SRC Pool: ~2 acre-feet 14 Consequences Of Overdraft 15 5

6 Consequences Of Overdraft 1. Loss in well productivity 2. Increased pumping costs 3. Change in water quality 4. Land subsidence 5. Loss of surface flows 16 Subsidence From over pumping of groundwater Over 15 feet in ~40 years Everything sinks (even trees) Can be general, or with fissures. 17 Subsidence in Tucson 18 6

7 Subsidence Fissuring and Infrastructure Not the same as arroyo formation Roads damaged Canals crack, sewage flows backwards 19 Extent of Subsidence Areas with 1600 ft. of sediments (gray) Areas with serious subsidence (red) Agriculture areas Municipalities Conclusion: Best not to deplete groundwater

8 Depth To Water (ft.) How Much Water Left Under Tucson? 640 acres 500 sq. mi ft. deep 25% porosity 1sq. mi. 80,000,000 ac. ft. 80 maf 640 acres 500 sq. mi. 250 ft. deep 25% porosity 1sq. mi. 20,000,000 ac. ft. 20 maf So, ~60 maf left, 6 10 af 325,851gal. Tucsonanday Tucson 1year 60 maf 268 Tucsonyear 6 1maf 1af 200 gal. 10 Tucsonans 365 day Well Hydrograph Pima & Swan Consequences Of Overdraft 1. Loss in well productivity 2. Increased pumping costs 3. Change in water quality 4. Land subsidence 5. Loss of surface flows 24 8

9 Surface Water Colorado River Watershed Seems big, but actually not (m 3 /sec): Colorado: 168 Columbia: 6,650 (40x) Miss.: 17,545 (104x) Amazon: 180,000 (1000x) Source: 25 Lee s Ferry flow: 13.5 maf/yr How many people would that provide for? 13.5 maf 10 af 325,851gal. 1pers day yr 1maf af 160 gal. ~ 75millionpeople 6 1yr 365 day 26 Whither the Rainfall? 640 acres 246,000 sq. mi. 1ft. ppt. 157maf 1sq. mi. Assume avg ppt of 12 in./yr Assume half of CRB above Lee s ferry CRB receives over 5x more rainfall than it drains Where does 80% of rainfall go? 27 9

10 Colorado River Compact, 1922 AZ: W.S. Norviel (2 nd from left) 4 th from left? (hint: It s not Haury) 28 Colorado River Compact WY, CO, UT, NM Upper Basin AZ, NV, CA Lower Basin AZ: 45% of basin, 33% of water Who was left out? 7.5 maf for each basin per year 75 maf to Lower Basin per decade Extra 1 maf for Lower Basin, just to be nice. 29 Reality Check Flow was assumed to 16.4 maf per year Past 300 years: Average: 13.5 maf Range: maf How do we know this? 30 10

11 Navajo Tribe All within basin Other Parties Might claim > 5 maf Can t use it, but might sell it Mexico 1944 treaty: 1.5 maf No flow to delta: water, silt, nutrients 31 Colorado River to Tucson? Carl Hayden legacy Begun in 1960s 300+ miles of canals Uphill Havasu: 482 ft. Enormous pumps Magnificent project $3.6 billion 32 CAP Pump: ~25,000 gal./sec. ~200 ft up Hohokam would be so proud!! 33 11

12 Arizona and CAP Water Storage into existing aquifers Replace groundwater pumping Still not using entire allotment CAP water unpopular to drink Tasty, smelly, different Working better this time CAP expensive to farm Only 1 profitable crop? Maybe 2?? 34 Importing Salts to Southern Arizona CAP water has 580 mg/l salts 6 1maf 10 af 325,851gal. yr 1maf 1af 3.785l 1gal. 580mgsalts 1Mg (tonne) ~ 715,000 tonnes/ yr 9 1l 10 mg 715,000 tonnes yr 3 trucks / min(non stop) 1yr 2 half ton trucks 525,600min 1tonne Where goeth the salts? 35 Groundwater Pumping Increases through time Used mostly for irrigation 36 12

13 37 Statewide Use: It s agriculture Fix your faucets all you want People replace cotton and lettuce, water use 38 Water Summary Relatively little drinking water worldwide Absolutely enough for humanity, so far SW groundwater (like a miracle) Not infinite, unintended consequences SW big rivers Not much flow, engineering marvels Are we immune from having to abandon infrastructure? 39 13