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Geology 3266 –Hydrology

Homework 7

1. On a winter day, the automated weather station near Weston Mill Pond in New Brunswick recorded the following values: the average Air Temperature was 27 oF , the average Wind Speed was 5 mph, and the average Relative Humidity was 40%.

TODO: Estimate Evaporation using the Harbeck and Meyers (1970) formula.

Suggested steps:

a. Convert the air temperature to Celsius.

oC = 5/9 (F– 32)

b. Look up e sat , in mb, for the air temperature given. A lookup applet is here, just be sure to change the temperature units to Celsius:



e sat = _________ mb.

c. Calculate the vapor pressure e from esat and RH

d. Convert wind speed in miles per hour to SI units m/sec.

e. Plug in your values to estimate E in cm/day. E = _______cm/day

2. Using a Penman-Kohler Nomograph, find the daily evaporation from a small lake with the following characteristics:

Mean daily temperature = 25.6 o C

Daily solar radiation = 550 langleys= 550 calories/cm2

Mean daily dewpoint = 4.4 o C

Wind movement = 5.5 feet/sec

Hint: The chart has been constructed for temperature units of oF, solar radiation units of cal/cm2 , and wind speeds of miles/day, so the given measurements must be in those units before the chart can be used.

a. Convert the Mean daily temperature to degrees Fahrenheit.

oF = 9/5 oC + 32

b. Daily solar radiation is already in the correct units

c. Convert the Mean daily dew point temperature to degrees Fahrenheit.

d. Convert the wind movement to miles/day

e. Follow the procedure given in the example problem while using the chart.

f. E = _____ inches

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