A Reservoir is subject to large evaporation rates resulting from the availabilit

Question

A Reservoir is subject to large evaporation rates resulting from the availability of water and high net radiation. A weather station in the vicinity measured the following during a summer day: Air Temperature at 2 m height (Ta) 17.9 oC Lake Temperature (T, ) = 13.4 °C Relative Humidity at 2 m height (Wa 0.32 Wind Speed at 2 m height (v, ) = 2.1 m/s Use Brutsaert's estimates of Zm = 2 m, zd = 0 m, and zo = 2.3x10-4 m over a water body to estimate KE (velocity dependent mass transfer coefficient).

Explanation / Answer

by the mass transfer expression-

E= KE va (e*s - ea )

where E = evaporation rate

va = wind speed

e*s = vapor pressure at lake surface

ea = vapor pressure at air

lake temperature = 13.4 c = 56.1 F

air temperature = 17.6 c = 64.2 F

relative humidity = 0.32 or 32 %

wind speed = 2.1 m/sec

so evaporation rate E by the formula is = 0.84 kg/m2/h

vapor pressure at lake surface = 6.11 * 10 ( 7.5 * T / 237.3 +T ) = 6.11 * 101.4

vapor pressure at air= 6.11 * 10 ( 7.5 * T / 237.3 +T ) = 6.11 * 10 1.6

vapor pressure at lake surface - vapor pressure at air = 6.11 approximate

mass transfer coefficient KE = 0.84 / 2.1 * 6.11 = 0.06

Related Questions

Navigate

• Browse (All)
• Browse A
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.