SO262 Physical Geography

Watering the Desert Cities

Salon, an online publication, just had a story on "Five Crazy Schemes for More Water" (http://www.salon.com/2012/09/20/five_crazy_schemes_for_more_water/), which were:

  1. Water for Las Vegas from eastern Nevada, near Great Basin National Park.
  2. Water for St George, Utah, from Lake Powell (which has similar problems to Lake Mead and the rest of the entire Colorado River we discussed)
  3. Water for the western US from Russia shipped in giant new aluminum tankers
  4. Towing icebergs
  5. Tap Canada, either Alaska and Northern British Columbia, or Hudson's Bay and Canada, and reverse the north-flowing rivers and ship the water south.

Download this spreadsheet: http://www.usna.edu/Users/oceano/pguth/downloads/CLIMATE_TEMPLATE.xls

Download this KMZ file: watering_las_vegas.kmz and open it in Google Earth.  It has a series of points across California and Nevada to Las Vegas.  There are also two points near Great Basin National Park, which is the proposed source for more water for Las Vegas.  For each point there is a link to the web site of the FAO (Food and Agricultural Organization of the UN), which provides a climate model for the point.  This model is generalized, and in particular does not accurately capture the peaks and valleys of the Great Basin, but provides a rough picture that is qualitatively acceptable.

The FAO says about this data: "The data available in the data-set refer to mean circumstances that are obtained by interpolating data from different climate stations. The data give an indication of climatic conditions but can never replace data obtained through stations. For more accurate assessments, it is therefore advisable to use as much as possible locally measured climate data."

Fill out the following table for the stations (this will probably be most easy in Excel, into which you can paste the table).  On the left, fill in values from the tables you get from FAO.  In the center, compute the lapse rates between pairs of stations as you move east.  Also compute the water budget for the year, Precip - Eto

Location Elevation July Mean T Ann Precip Annual Eto   dz dt lapse   Water budget
Great Valley           xxxx xxxx xxxx    
Peak Sierras                    
Owens Valley                    
Panamints                    
Death Valley                    
Spring Mountains                    
Las Vegas                    
                     
Spring Valley           xxxx xxxx xxxx    
Snake Range                    

You can get graphs of the climate by cutting the data from the FAO website, and pasting it into the spreadsheet you downloaded.  There are directions in the spreadsheet; it is a two step process.  If you use the spreadsheet, all the graphs will look the same, and you can easily compare them.

 

Answer the following questions, in a Word Document or PPT presentation turned in by the end of class.  You will work in three groups of 4-6 each, and divide up the work.

  1. While the numbers for the lapse rate are a little off from what we have discussed, the patterns are reasonable.  What pair(s) of stations has the closest thing to a moist lapse rate, and why does this make sense?
  2. What stations have the most balanced water budgets?  What factors do you think help account for this?
  3. Compare the ET0 curves for two adjacent stations at different elevations.  What patterns do you see?
  4. Compare the temperature range curves for two adjacent stations as different elevations.  What patterns do you see?
  5. What do you think of the prospects for Las Vegas getting water from the vicinity of Spring Valley or the Snake Range?