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U4735x Environmental Science for Decision Makers

Problem Set #3: Water Withdrawals, Population, Desalination and Irrigation.

9/18/13, due 9/25/03 at class time.

The purpose of this exercise is to explore data on water withdrawals, population, desalination and irrigation. Another goal is use spread sheets to organize and examine water information, including making simple graphs. The second question requests calculation of annual percentage increases. You can do these either with spreadsheet operations or with a calculator. Some of the data you need to answer questions should be in Tables 19 and 2 in the Gleick text book (2002-2003) and some from web sites [www.worldwater.org] [www.icid.org]. You are encouraged to consult other sources as well.

  1. Water withdrawals increased substantially in the USA during the 20th century.

    1. Using data from Table 19 in the Gleick text, make a spreadsheet including year (column 1), population [millions] (column 2) and water withdrawals [km3/yr] (column 3).

    2. Calculate per capita water withdrawals [m3/yr] (column 4) and per capita water withdrawals [m3/day] (column 5).

    3. Make time-series plots of the data in columns 2, 3 and 5 vs year. Either separate or combined plots vs year can be generated, whichever you find more convenient.

    4. Describe in words the time trends observed in the USA for population, total water withdrawals (km3/yr) and per capita water withdrawals (m3/day).

    5. How do you think that relative proportions of major categories of water withdrawal (domestic, industrial, irrigation) may have changed in the USA during the 20th century (consult Table 2)?

    6. How would you explain the time trends for per capita daily water withdrawals during the last three decades of the 20th century?

    7. How does the total water withdrawal for the USA in 1995 reported in Table 19 compare with the same parameter reported in Table 2? If they are different, how might you account for the discrepancy. Do you think it is significant?

  2. Return to the spreadsheet generated in the first question. Using data in columns 1 and 2, calculate annual percentage increases in population for each pair of rows down the table (column 6), annual percentage increase in total water withdrawal (column 7) and annual percentage increase in per capita water withdrawal (column 8).

    The calculations requested in question 2 can be done with a calculator, or with spreadsheet operations. If you use the same arrangement of columns as outlined above, the cell entry for population increase from 1900-1910 (entered in the row for 1910, which is assumed here to be row 9) would be: =100*LN(b9/b8)/(a9-a8)

    LN indicates the natural logarithm; b9 indicates the contents of cell b9, etc

    The function from which you could derive the above operations is listed below:

    Pop(1910) = Pop(1900)*ert

    where t = years (10) and r = fractional annual increase (ie 0.01 of percentage annual increase).

  3. From the above percentage increase calculations,

    1. which three time intervals had the highest annual percentage increases in population?

    2. Which time intervals had the highest annual percentage increases in per capita water withdrawals?

    3. What factors might have been contributed to large percentage increases in per capita water use in those periods.

  4. Desalination is now used in a large number of countries. Consult the data table on desalination at www.worldwater.org, a website of the Pacific Institute for Studies in Development, Environment and Security. The appropriate file is Table 16 from the Gleick book for 1998-1999.

    1. Print this table and generate a new spreadsheet on desalination, listed in decreasing order of desalination capacity, for the following 18 countries: Saudi Arabia, USA, UAE, Kuwait, Libya, Japan, Qatar, Spain, Italy, Iran, Iraq, Singapore, India, Egypt, Israel, Australia, Jordan, Pakistan.

    2. List these country names in column A, population in column B, Desalination capacity [m3/day] in column C and Fresh water withdrawals [km3/yr] in column D.

    3. Calculate the per capita Desalination Capacity [liters/day] in column E, per capita Fresh water withdrawals [liters/day] in column F and the percentage of Fresh water withdrawals represented by Desalination capacity in column G.

    4. Which five countries have the highest percentage of fresh water which could be provided by desalination? Why do these countries have such a large investment in desalination?

    5. How do the percentages of fresh water available from desalination in the following countries compare with the five countries with highest percentage desalination: USA, Japan, Spain, Italy, Australia? Why do they differ so much from the highest group?

    6. Comment on the percentage of fresh water available from desalination for Israel and Jordan compared to other countries in the Middle East.

  5. Irrigated crop lands supply about 40% of global food, but represent only about 18% of total crop area (270 million ha of 1500 million ha). Information on country and continental areas of irrigated croplands are compiled on a web site maintained by the International Commission on Irrigation and Drainage. You may have to explore the site for awhile to locate the appropriate table.

    1. Consult this table, or another source, and list the three countries on each continent (North & Central America, South America, Africa, Asia, Europe, Oceania (two countries only) which have the highest total area of irrigation.

    2. What percentage of arable and permanent crop area (APC) are irrigated in each of these 17 countries?

    3. Rank the major continent groups in order of highest percentage of irrigated crop lands (Americas, Asia, Europe, Africa, Oceania).

    4. How would you guess this rank order of percentage of irrigated croplands might compare with the number of large dams (>15 meters in height) in these continents, relative to their total populations?