In this article (And video above), I solve a problem related to the surface water system hydrologic budget that falls under the environmental engineering & water resources section of the FE exam, similar to what you may encounter during the exam.
Question:
A 7-acre surface area pond is located within a 520-acre watershed. Assume that the infiltration and the seepage are negligible. There is no plant biota around the pond. The watershed received 3.20 in of rainfall for the last 30-day month. The pond elevation at the beginning of the month is 520.5 ft with respect to mean sea level (MSL). By the end of the 30-day month, the pond had risen to 522.2 ft, MSL. Average stream flows into and out the pond during the month are 0.522 cfs and 0.22 cfs respectively. The amount of evaporation (in) of water that take place from the surface of the pond during the month is most nearly:
- 7.10
- 16.2
- 13.6
- 1.44
Solution:
Use the Hydrologic Mass Balance (Budget) Equation:
Since the seepage, infiltration and transpiration are negligible, the above mass balance reduces to:
Dividing 
by the surface area of the pond, A and converting to inches yields and increase in water level in a month to be:
Solving for the surface evaporation 
from the Hydrologic Mass Balance:
Answer: C
NOTE: The negative sign indicates a loss from the hydrologic cycle.
Reference: NCEES FE Reference Handbook, v. 10.0.1, p.294 of 498.
This question was supplied by Geder L. Mena Jimenez, E.I.T, an environmental engineer II at GZA GeoEnvironmental Inc. Mr. Mena received a Bachelor of Engineering in Earth Systems Science and Environmental Engineering from The City College of New York (CUNY) – Grove School of Engineering, 2017. Mr. Mena’s experience includes a variety of environmental site investigation and remedial activities: Environmental Site Investigation (ESI), Subsurface Remediation, Community Air Monitoring Programs (CAMP), Soil/Groundwater/Vapor sampling, Site Inspection, Data Analysis, Groundwater Modeling, GIS, Hydrology and Hydraulics Analysis, Underground Storage Tank (UST) Management and Closure, and Characterization of Soil and Groundwater for disposal. You can connect with Geder here.
I hope you found this week’s environmental engineering & water resources question helpful. In upcoming articles, I will answer more FE Exam questions and run through more practice problems. We publish videos bi-weekly on our Pass the FE Exam YouTube Channel. Be sure to visit our page here and click the subscribe button as you’ll get expert tips and tricks – to ensure your best success – that you can’t get anywhere else. Believe me, you won’t want to miss a single video.
Lastly, I encourage you to ask questions in the comments of the videos or here on this page and I’ll read and respond to them in future videos. So, if there’s a specific topic you want me to cover or answer, we have you covered.
I’ll see you next week.
Anthony Fasano, P.E.
Engineering Management Institute
Author of Engineer Your Own Success
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