Math 408N: UT Part II: A Lake Travis Model Fall 2017 6. Evaporation. As previous
ID: 360537 • Letter: M
Question
Math 408N: UT Part II: A Lake Travis Model Fall 2017 6. Evaporation. As previously noted, evaporation plays a major role in water loss to a reservoir. In 2011, it was estimated that Lake Travis lost 60, 000 acre feet of water (An acre-foot is about 325, 800 gallons (1,613.33 yd), or enough water to satisfy the annual washing, watering and drinking needs of roughly three Austin households). Table 2 gives historical evaporation data for the Austin area. This table was con- structed using 27 years of data, collected by the National Weather Service at a location 3.2 miles northwest of central Austin. The first row gives daily average drop (in inches) that results from evaporation in a 4-ft diameter round pan; in the second column, you need to compute the corresponding Daily Average Evaporation in yd3 per square yard of surface area; the third column Daily Average Evaporation should be given in cubic yards; and Total Monthly Evaporation should be given in acre feet. Table 2: The drop in inches per day from evaporation in a 4-ft diameter round pan Jan-T-Feb.-T March-T-April 1-May-T- June 0.1 0.13 0.18 0.220.250.32 Month Average drop Daily Av. Evap. Conversion Factor-T-0.6 0.6 -0.6-- 0.6 -0 6 Daily Av. Evap Total Montly Evap. 0.6 Month (continued)| July-1-Aug-1-Sept-1-et.1 No-1-Dec. Average drop Daily Av. Evap Conversion Factor | 0.6 | 0.6-1-0.6-1-0.6-0.6 -0.6 Daily Av. Evap Total Montly Evap 0.35 0.34 0.26 6 0.20 0.14 0.1 (a) Convert the data in row 2 of Table 2 to find the average daily volumetric evap- oration rate (in cubic yards per square yard of surface water per day) and place your results in row 3 of the table. (b) Pan evaporation rates don't generally correspond directly to lake evaporation rates. A common conversion factor for many lakes is 0.6. That is, lake evaporation is approximately 60% of what the pan evaporation is. Use your results in part (a) to estimate the average daily volumetric evaporation (in cubic yards per square yard of surface water per day). Place your answer in row 5 of Table 2.Explanation / Answer
Formulae used:
Pan area Month Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Ft^2 12.56637061 Avg Drop inch 0.10 0.13 0.18 0.22 0.25 0.32 0.35 0.34 0.26 0.20 0.14 0.10 = Avg Drop yard 0.00278 0.00361 0.00500 0.00611 0.00694 0.00889 0.00972 0.00944 0.00722 0.00556 0.00389 0.00278 Yd^2 1.396263402 Daily Av Evap (Yd cub) 0.0028 0.0036 0.005 0.0061 0.0069 0.0089 0.0097 0.0094 0.0072 0.0056 0.0039 0.0028 Conv Fac 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6 Daily Av Evap 0.0017 0.0022 0.003 0.0037 0.0042 0.0053 0.0058 0.0057 0.0043 0.0033 0.0023 0.0017 Total Monthly Evap Data from question 5 missing (multiply the no of days and area * yard square)