Experts,

In prob. 508, p.126, NCEES water PM, there is solution on page 207 and I got the following errata from web.

p. 207, Water Resources and Environmental Solution 508:
The following information clarifies the existing solution.
Rainfall 1 is from time = 0 hr to time = 1 hr at an intensity of 1.5 in./hr.
Rainfall 2 is from time = 1 hr to time = 2 hr at an intensity of 0.7 in./hr.
The discharge in the watershed during the second hour will consist of:
The second hour of Rainfall 1 (1.2 cfs/in. × 1.5 in./hr × 1 hr) plus the first hour of Rainfall 2
(0.5 cfs/in. × 0.7 in./hr × 1 hr), or 2.15 cfs.

I really dont get why they calculated rainfall like this:

I belive it should be like:

The second hour of Rainfall 1 (1.2 cfs/in. × 0.7 in./hr × 1 hr) plus the first hour of Rainfall 2
(0.5 cfs/in. × 1.2 in./hr × 1 hr), or 1.44 cfs.

Also for water prob 502, solution on p.202,

third line is:

hall= 285-80.4-(120+20x2.31)

why do they use factor 2.31. I belive it should be 0.43 to convert psi to feet.

Am I right?


Can you guys please give your valuable inputs!!!!

Thanks.

Have you searched here yet? If not, in the future take the thirty seconds or so it requires and save someone the time of repeating. If you did search, maybe you missed this: NCEES Sample exam WR&E #508. If you still have questions, you might want to post it to the original thread.

1 foot of water = 0.433 psi
1 psi = 2.31 ft of water

Without reading the problem, if you want to convert psi to feet, you need to multiply the value (in psi) by 2.31:

20 psi x (2.31 ft of water / 1 psi)

I am really sorry for the repeat.

but I am new member here. I tried to search here but didnt get anything.

so posted here.

I just tried to search for this question and I am not getting anything.

can you please advise how to do search.

I have also prob in water 6 min prob 3 on page1.

I tried for that too but didnt get anything.

Fair enough... that's why I asked. I remembered I participated in the discussion, so it was a little easier for me (I searched only posts by me). But a simple search of "rainfall" gives you a top-ten resulting post with "508" in the subject.

Did your two original questions get answered?