Calculating the Storage Volume in a Pond?

[GreeneSWCD]

I'd like to figure the storage volume of a pond at different waterline elevations.  I can do this easily by hand on paper, but I'm sure there is a better way to do it with C3D.  Basically, I have a levy I've drawn across a valley and a pool area that is cut out in front of it.  The levy and pool areas are different surfaces. 

I think I want to build a flat surface at each proposed waterline elevation and then compare the bottom of the pool area and the inside toe of the levy slope surfaces to these proposed waterline surfaces.  How do I go about that?

[Citadel2012]

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@GreeneSWCD wrote:

I'd like to figure the storage volume of a pond at different waterline elevations.  I can do this easily by hand on paper, but I'm sure there is a better way to do it with C3D.  Basically, I have a levy I've drawn across a valley and a pool area that is cut out in front of it.  The levy and pool areas are different surfaces. 

I think I want to build a flat surface at each proposed waterline elevation and then compare the bottom of the pool area and the inside toe of the levy slope surfaces to these proposed waterline surfaces.  How do I go about that?

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Firstly, have you modeled the pool and levy as C3D surfaces? If the answer is yes, then you could create a new site and draw a feature line in that site representing the proposed waterline elevation you are working with. Creating a new surface with only that new feature line as the definition and using the surface volume panorama tool would give you proposed storage volume. Using the feature line raise/lower feature and regenerating the volume tool makes it easy enough to find the storage volume at different depths, so making several surfaces for each depth is not necessary.

I would be careful of the geometry of the new feature line and corresponding surface, as to not pick up extra cut/fill from extraneous triangles. 

[owenmull]

So basically, you have a pond and you want to know how much water it contains at a certain elevation.

Im assuming you have an 'Existing Ground' surface. There are a couple of ways to do this, but here is a short video demonstrating how to extract user contours from a surface.

http://www.screencast.com/t/w5NlAuKnrY

Basically, what I would do, is on your 'Existing Ground' surface, create and extract all the contours (your various water surface elevations), then create a surface from each extracted polyline, and use the Volumes Dashboard (shown in video) to calculate your volumes for each (Base = EG, Comparison = WSE).

Another way you could do this is to extract the contours the same way, and create a 'Bounded Volume' within your 'Existing Ground' surface using each extracted contour as the bounding element (also briefly shown in video). This only calculates volumes between surfaces within the border you specify (your WSE polyline).

HTH

[GreeneSWCD]

I forgot to mention that I'm using C3D 2012, if that affects replies?

Ok guys, both of you have offered great advice in how to tackle this. I'll be sure to watch that video too.

To clear some stuff up, yes, the fill and the pool area are both C3D surfaces. There is a third surface in my drawing, existing ground, but there isn't any of that surface left in my area of interest, only pool and levy. I'll try to figure out which way posted would be best for me, and I'll check back in today. THanks!!!!

[Citadel2012]

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@owenmull wrote:

So basically, you have a pond and you want to know how much water it contains at a certain elevation.

Im assuming you have an 'Existing Ground' surface. There are a couple of ways to do this, but here is a short video demonstrating how to extract user contours from a surface.

http://www.screencast.com/t/w5NlAuKnrY

Basically, what I would do, is on your 'Existing Ground' surface, create and extract all the contours (your various water surface elevations), then create a surface from each extracted polyline, and use the Volumes Dashboard (shown in video) to calculate your volumes for each (Base = EG, Comparison = WSE).

Another way you could do this is to extract the contours the same way, and create a 'Bounded Volume' within your 'Existing Ground' surface using each extracted contour as the bounding element (also briefly shown in video). This only calculates volumes between surfaces within the border you specify (your WSE polyline).

HTH

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This method would work best. Creating user contours at specific depths in the proposed pool surface, extracting the contours and creating their own surfaces would guarantee that the geometry did not mess up the volume calc. With that being said, a good sanity check would be to make sure there is no cut showing in the calculation. I'm not familiar with bonded volumes but it looks to be the same concept.

[GreeneSWCD]

I think I left out one important bit of information. The waterline elevation compared to the bottom changes, but the waterline itself stays the same with only the elevation of the bottom changing. My design goal is to store just enough water in the pond with the least amount of cut. So, I'll be lowering my pond bottom until I hit a storage goal.

And, won't I have to blend the two surfaces (levy and pool area) into one surface first for either methond to work? Or, if I use the bounded surface (just watched the video, looks cool) can i bound three surfaces?

[Citadel2012]

Sounds complicated. If the pool shape remains constant regardless of its depth, you could raise/lower the pool surface until you achieved the correct volume from the proposed water line, then work to connect the pool surface to the levy. You would have to regenerate, re-extract, and recreate the water line surface each time you changed the pool surface elevation, because the contour geometry would change.

[GreeneSWCD]

 It is fairly complicated, I guess.  We, the USDA, used to have a dos based program that would do this for us, but that program won't run on Win7.  So, all of us engineers are looking for a better way to do a WASCOB (Water and Sediment Control Basin). 

[owenmull]

Ok. So, here is a simplistic sketch of what I gather you are trying to do.

So, assuming you don't care what the Side Slopes are, you can create your Water Elevation surface as described using contours earlier, and then, what you can do is draw a polyline (or if it is a definite elevation use the user contours again) to define the boundary of what you are calling the 'Bottom' of your pond, as shown above. If it is a polyline, you can copy your pond surface (the surface shown above in Green, whatever youve named it) and re-name that copied surface 'Bottom' or something similar, and then trim it to your polyline. This can be accomplished by Prospector-->Surface-->'Bottom'-->Definition-->Boundaries (right click)-->Add and select Type-->Outer and select said polyline. 

Now, you can compare your Water Elevation surface to this 'Bottom' surface. To adjust, go under the Definiton of the surface (explained earlier) and Edits (right click)-->Raise/Lower*. Here you can change the 'Bottom' and re-run the volume calc until you get what you want. 

*NOTE: This Raise/Lower is relative to the current surface elevation, NOT the original, so you will either have to delete the previous edit (listed in the box below the prospector under Edits) or account for it.

An earlier poster suggested creating a Feature Line out of the polyline used to cut your 'Bottom' surface, but this would assume that the bottom of your pond is a flat, uniform surface. If the bottom of your pond is to be flat, you could create a Feature Line from the earlier referenced polyline, and make that into your 'Bottom' surface. From there, it's a matter of using the Elevation Editor to raise/lower said Feature Line to achieve the volume you desire, as described above.

My method retains the 'natural' contours of the bottom, more or les, if that's what you're after.

HTH

[owenmull]

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And, won't I have to blend the two surfaces (levy and pool area) into one surface first for either methond to work? Or, if I use the bounded surface (just watched the video, looks cool) can i bound three surfaces?

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No, you cannot bound between 3 surface. You would have to create a merged surface for your levy and pool, and compare to that if that's what you want.

Whether you compare your MERGED-LEVY-POOL surface to BOTTOM surface, or your POOL surface to BOTTOM surface, results should be the exact same. In this case, what's outside the limits of your Water Elevation surface isn't accounted for in the volume calculations, so merging wouldnt affect it.

[GreeneSWCD]

Man, you guys are good. I'll check into this right after lunch.

And, Mr. Mull, how do you like that 32 GB of RAM? Was it worth the investment?

[owenmull]

It handles C3D very, very nicely. 🙂