Pond Boss Forums POND CONSTRUCTION Selecting a site Watershed for 2.4 acre pond

This is a view of the area surrounding my proposed pond site. It looks to me like a total of 460 acres of watershed, but land is relatively flat. Contours shown are only 1 meter apart. The pond water level will be around 15 meters below the high point in the region, which is about .7 miles from the pond.

This is in a county with average rainfall of 24.1 inches/year. 38 days/year of more than .1 inch.

What do you think?

Randy Cooper
Cactus Blum Ranch

Hard to tell in any place in West Texas. 24 inches isn't that much and you can easily go through the hotter parts of the year with dang near none. My place is just South of Bowie and I heard that we were having the 7th wettest year on record. I'm a little over 4 ft low and most in the area are. We seem to from lots of rain to dang near none.

I would ask your local NRCS folks. Is a well for supplemental water an option? With only 2 inches of rain per month I would want to get all the professional advice I can get before investing.

Not a pro....just my 1 cent

The county NRCS person has been out to the site but did not seem to know that much about ponds. She was very concerned about the soil and lack of good clay. There are two field engineers coming back next week to do a survey to determine what type of dam construction would be required. The field engineer who I spoke to said he thought it would work as far as the watershed, but I'm worried that only a small fraction of the overall rainfall will come in concentrated enough amounts to reach the pond.

We had one rain back in July that I believe would have filled it completely over a 2 day period based on the level of trash stacked against the trees and yucca at the main input end of the pond site, and the pile up against the fence where the dry creek runs off the property. Unfortunately I was not there to see it. I've only seen water in the low areas one other time, and that was after 1 inch of rain over a 4 hour period.

I do not have a well that would support it right now, but have considered drilling a well 1st just to see if I can get enough water out of the ground to make up for some of the evaporation. The only well on the property right now is shallow and will produce about 20 gal an hour max. It is not near the pond site.

We are already planning for a liner due to the anticipated soil conditions, and the need to keep every drop of water we can get into the pond.

IMHO drilling a well first is a smart move. Once it is done and you know its capacity, you can approach the pond project with a lot more confidence, especially if you are looking at the very substantial expense of a 2 acre plus liner. I would size the pond based on the well capacity but I'm a very conservative guy.

Good luck and please keep us informed as you move forward.

Bill D.

I suggest you contact a local water well drilling co. Just because you drill a hole in the ground does not mean you will get a well. in my business I have seen several wells not produce water when needed and I am in E Texas where we get around 42" of rain.

I've done that, plus pulled well logs for all the wells that had logs on file right around me. Even relatively close by, they vary from 8 gpm to 30 gpm.

The most experienced well guys in the area will not make any promises on capacity or even hitting water. The well on my property, 1/4 mile from the pond site produces less than 1 gpm, but is in a pretty high water zone.

I really need 50 GPM to even put a dent in the expected evaparation loss.

I re-checked my math, and the lake evaporation data for my quadrant near Eden tx...

Unless I botched the calculations again, it looks like if I can produce 5gpm average, 24hrs/day it will make up for the difference between precip and evaporation... So it should be feasible to use a 10-20 gpm well in the dry season to keep the level fairly constant.

Have you got on Google Earth and searched the surrounding area for existing ponds? That might give you some idea if other ponds have been successful (or not).

I was looking around my area with Google Earth and was surprised to see a rather large pond (stip pit) in town that I did not know existed yet it had been there all my life and I have drove by it a thousand times. It was hidden by trees.

So you might find some BOW's around you that you did not know existed.

I have looked all around me on Google Earth, and there is next to nothing around me pond-wise. I did find one about 3 miles from me, but it was almost empty. I do believe I can succeed at my site due to fairly large watershed (even though very little slope), and the fact that I am starting out assuming I will need a liner to hold the water. The ground is very porous and rocky in this area.

The main reason I am looking at doing a well for supplemental water is so the level will not fluctuate wildly between the occasional hard rain.

Sounds like you are going about this logically to me.

In your overflow, make sure you provide for some huge water flow for the once in ten year rains. Even though you are in a dry low rainfall area, with that size watershed if you got a 6" rain in 24 hours you could be dealing with huge volumes of water.

A more than adequate sized overflow with an emergency overflow vastly over sized would be good. Then double that.

NRCS ran some numbers for my site, and they say in a 50 year storm event, my watershed is around 600 acres, not 460. We are continuing to look at our options for the site. It looks like we will need a relatively big auxiliary spillway to protect the DAM in one of these big events.

NRCS is also going to share the data they've come up with that shows projected flow through the area in several different scenarios, which are normally occurring multiple times per year.

We dug test holes, and it is going to be fairly expensive excavating due to soil only 1'-3' thick on top of 5'-10' of caliche (calcium carbonate deposits of varying densities for those not from around here). To get some deeper holes, we will probably need to punch some holes through the underlying bedrock in a few areas. The dam will only add about 4' of water depth in the areas that are the lowest natural areas near the dam location.

I have not decided what to do about drilling a well. That is still on the plate as a precursor to starting excavation.

I think in your situation, the logical way to go about it is to use a liner to minimize any seepage through a clay liner. Water evaporation is going to be high, and it sounds like a 4" well will be all you need. In any case, I'd double screen the well, both to expose more area to the aquifer, and to lengthen the longevity of the well. If you can, use a stainless, not plastic screen. They perform better.

I agree with the NRCS in making sure you have a large enough emergency spillway. You don't want a 500-1,000 year rain event to blow out the dam and require repair of both the dam and the liner.

I would dig it as deep as your pocketbook allows. You will have to cover the caliche with some sort of padding to help prevent it puncturing the liner. Also deeper means more water in the "bank" so to speak during times of drought.

Look at Bend Tarp and Liner. They have a woven fabric liner that looks to be pretty good. I've never used it, but the sample that they sent me was tougher than urethane liners.