15 replies to this topic

[Lucky1]

Can anyone share some insight on what to expect in these two subjects? Per the NCEES outline, for Environmental there is small chance of only 1 or 2 problems in wastewater and water treatment. Hydrology covers a bigger area. Tips on more easily solving the tough hydrology problems - frequency, hydrographs, rainfall intensity would be great. With a background in construction had never seen hydrology problems until preparing for this exam.

[Illini86]

totally agree dude, im in structural and i royally blow at all this water stuff as NEVER really took any classes on it and never did it before reaching that chapter in the review book....i did the hydraulics in school but that was liek 4 years ago and i'm waaaay rusty...this water stuff in my opinion is the hardest stuff i hope its really dumbed down except for maybe 1/2 hard ones...

the hydropgraphs take a while to make too so i dont know if that would be on there but the chemisty stuff is hard and the 50 different processes for treatments and such....not a fan

[Lucky1]

There are several of us struggling on hydrology. Can anyone help us?

[VTEnviro]

Specifically, what are your questions?

I've been known to rock an IDF curve or two over the years.

[Road Guy]

[VTEnviro]

Following a few simple principles, you too can design a safe and reliable drainage system.

[DVINNY]

^^^ TRUE


remember to place your manhole properly

[DVINNY]

[DVINNY]

Don't park your Caddy over top of certain manholes

[VTEnviro]

What happens if yours starts surcharging uncontrollably?

[Lucky1]

One hangup is not knowing when to use the itensity (given or from the curve) as is or have to adjust it based on a unit hydrograph or rate. The hydrology questions with I are a brain teaser for those of us who have never seen it before opening the CERM manual.

[envirotex]

@Lucky1: Can you please post a problem from the CERM as an example? Sometimes it's easier to help out if someone can solve a specific problem for you...then you can go and practice, practice, practice...

[Lucky1]

NCEES Civil Sample Problems & Solutions (2008 edition)
Problem 119. The 1-hour unit hydrogrograph for a watershed is given in the figure below. A 2-hour storm of intensity of 0.5 in./hr in this watershed produces a total excess volume of water (acre-ft) of most nearly: A) 0.01, 37, C) 75, D) 450. Below the graph(discharge vs. time (which I haven't included but is not significant to solve the problem) is a table with values from the graph as follows:
Time (hours) 0 1 2 3 4 5 6
Discharge (cfs) 0 75 200 100 50 25 0

To solve, use the numbers from the table to create another table with Qu, Q1, Q2 and Qtotal. Sum the Q totals and convert from cfs to acre-ft.

Now, what is the significance of the 2 hour storm and 0,5 in.hr intensity. What is the key in these problems for knowing to use the numbers in the table as is or having to adjust for a Qu? I have seen a few problems (still going through old notes to find) where the tabular numbers given have to be adjust to the "unit" hydrograph of the storm. This problem as it stands would be simple. What throws me is knowing when to use what your are given versus when you have to convert for Qu. Thanks.

[Jayman_PE]

Go see the Texas A&M problems and see under Hydrology. http://engineeringre...loads/index.htm

[Lucky1]

<sub>It's been so long since I read that material I forgot about it. I'll check it out again.

I'm looking for what wording to look at in the problem that gives the hints on how to do these problems. The ones with the hydrographs are mind teasers.

If anyone else has any tips, please speak up. We are getting on the home stretch.

Thanks!</sub>

[sledgeconcrete]

Applied Hydrology by Chow, Maidment, and Mays

You have to adjust the unit hydrograph if the duration of the precipitation is longer than the unit hydrograph duration. 1 hour hydrograph, 2 hour storm. That is what you are doing with the Qu, Q1, and Q2 because you have the discharge information.