\ Department of Geography, University of Victoria GEOGRAPHY 370: HYDROLOGY – Spring 2019 Instructor: Dr. Matthew Asplin Laboratory Assignment 3: Water Vapour, Energy, Evapotranspiration and Groundwater 71 marks Date Assigned: B01 (Feb 11 th ), B02 (Feb 14 th ) Due Date: B01 (Mar 4 th ), B02 (Mar 7 th ) In this lab you get a chance to work through some of the equations that we have encountered in this course so far pertaining to water vapour, energy budgets, evapotranspiration and groundwater. Use a spreadsheet, calculator or scripting for the calculations. In this lab assignment, you do not have to show all of your work, but you must provide enough sample calculations that we can follow your methodology and you can demonstrate that you know where your answers came from. Learning Outcomes: 1. Students will become familiar with equations in this course pertaining to water vapour transformations, energy budgets, and estimates of evapotranspiration 2. Allow students the opportunity to become comfortable with equations and calculations in excel or equivalent analysis software (if desired) Background Information and Some Equations Additional supporting and equation information can be found in your textbook and may be helpful as you work through this assignment. Pressure and Weight The mean pressure of the atmosphere at sea level is (1013.25 mbar or 101.325 kPa or 1013.25 hPa or 101,325 Pa or 101,325 N m -2 or 101,325 kg m -1 s -2 ). Pressure, P equals force acting over an area, A . The force of the atmosphere is due to the weight of air, mg ( m = mass, g 9.8 m s -2 = the acceleration of gravity). Hence the pressure of the atmosphere can be written as: Since we know P and g at sea level, the mass of a column of the atmosphere 1 m 2 in area is P / g = m / A 10 4 kg m 2 . It is useful to work with vertical columns of air (or water) since we often want to solve for “depth” of water, in cm or m. Density ( ) is mass ( m ) divided by volume, V and is usually expressed with the units of kg m -3 A mg = P / .