I’m hoping to build a pond on land just south of Athens TX. The site has 48 acres of runoff watershed (no springs). There is an existing 0.5 acre pond immediately upstream of where I’d like to build a 2 acre pond. However, I have concerns that level in a new 2 acre pond would be down by a few feet most of the time, even with some supplementation from a well.

Do you have any recommendations for individuals/firms who could perform a feasibility study? The NRCS has not been much help. I tried a local civil firm and Freese & Nichols, but the job is too small for them. I have soil data and precipitation/evaporation data back to the 1950s.

The NRCS Handbook 590 shows about 7 acres of watershed for each acre-ft of water to be impounded (for your estimated location).

However, after the pond initially fills, then evaporation should be the main variable, so "surface acres" should be the controlling factor.

In that case, 48 acres of watershed should support a 6.9 acre pond.

However, I have posted these numbers before in the forum and people with local knowledge usually say the estimate from the Handbook is too optimistic.

Further, you should also de-rate your watershed a little, since the upstream pond will preferentially capture run off - especially during drought conditions when it is very low and you need water the most.

There are other factors beside just the area of the watershed that determine how much surface water will make it to your pond.

Steeper slopes and rocky terrain will contribute more water. Flat, lush grasslands will intercept more of the rain.

Here is a link to the handbook, which should give you lots of good information while you are in the planning stages.

NRCS Pond Handbook 590

Another option might be to add a small forage pond upstream of your 2-acre pond. If the slope allows, you could gravity drain it into your main pond during a drought. If not, then you could pump this additional water storage as needed. Further, a forage or grow-out pond might have good value to you during normal years.

Good luck on your new pond project!

IMO the amount of water shed for a pond depends on how well the basin is properly compacted / sealed. If your bucket leaks it takes more water to keep it full. The tighter the soil in the basin the less water shed that is needed to keep it 'full'. For a smaller pond and long term benefit IMO it would be wise to prepare the basin during compaction with an insurance soil sealant such as Soil Floc. Doing good preparatory home work will make the final project more successful. Are there any good ideas how much it will cost to fix a leaky pond???? Lots of money!!

Thanks for the link to the handbook. If I'm reading it correctly, the 7 acres of watershed is per "acre-foot" which would support 1.1 surface acres (assuming 6' average depth).

Thanks for the reply. I just googled Soil Floc and it looks like a good product, though pricey for a 2 acre pond (~$20K).

Talk to teehjaeh57 here on the forum. He helps people all the time that have leaky ponds by using a polymer based sealing product. Send him a PM and he will respond. I will be meeting him tomorrow early afternoon and I'll mention this thread to him.

Yes, their estimate is per "acre-foot". That makes no sense to me, since the evaporative water losses will only be a function of surface acres. The depth of the pond (hydrostatic pressure) makes a very slight difference on seepage losses. However, I don't think that is enough to use the acre-foot term.

I have posted the question about their units in some Pond Boss threads, but no one has ever explained why their choice is correct. Most of the handbooks published by state agencies give rules of thumb for watershed area per surface acre of pond.

I believe (as a non-expert) that you probably have sufficient watershed for your planned 2 acre pond. Note that it is also a problem to have too much watershed for the size of a pond. If that is the case, then you will constantly fight flooding and a chance of water overtopping your dam during big rain events.

Finally, there is no substitute for empirical data. Is your area still in drought conditions? If so, then go observe the upstream 0.5-acre pond. How much is the water level there below normal full pool? Further, you could pull some satellite views for some nice ponds in your immediate area. Planimeter the area of the pond, and then estimate the contributing watershed from the topo maps. That should get you into a good range for your property.

Have fun on your project. A 2-acre pond in east-central Texas should be a valuable addition to your property!

I’m in Red River county just north of you. 48 acres of watershed for a 2 acre pond is more than enough for east Texas.

For my ponds I would guess my watershed to pond size is 10:1. Even in drought years my ponds are always full heading into summer.

I think there are several dependencies.
How dry is the runoff area and how “hard” was the rain. A slow soaker is called a farmers rain because it soaks in.
How is the terrain? Is it conducive to quick runoff?
First moisture on fresh dirt all soaks in.

Air temps?

Thanks!

Thanks for the tip. I'll send teehjaeh57 a PM

FYI...I am in deep east Texas and dug a 2 acre pond about 8 years ago now. I have ONLY about 15 acre watershed but my pond sits downhill. It has gone over my spillway maybe 4 times in 8 years. Most of the time it runs about 2 foot low. This year is record low at about 6 feet!! I have no spring and no well to assist in drought conditions. At full pool my deepest part is not quite 12 foot deep. My advice is when you plan your pond and add structure just remember...it will very seldom be at full pool!!

Thank you for the reply. Yours is probably the closest comparison to my situation. I have more watershed, but I suspect you have more rainfall. If you had to do it over again, would you build a smaller pond? I ask because I'm trying to decide on whether a smaller pond, that hopefully gets fill to full pool more often, would be better.

ET, based on my east Texas experience I'd say that depth is important. Normally we think of really deep, say > 12 feet, is wasted water that the fish don't use in summer due to anoxia. But my depth at full pool, around 21 feet, has been a lifesaver both during terrible winter blast a year ago, and drought this year.

I love the 2 acre size of my pond and would NOT want it any smaller. I DO WISH I would have given the dozer a few more days to make it deeper but other than this last horrible drought year I have been fine with mine. Make sure your "shallow" water even at 3-4 foot low will still have at LEAST a foot of water in it.

Great advice! Thanks

Thanks for the reply

esshup,

I connected with teehjaeh57 as you suggested and we had an excellent conversation. He shared a lot of great information on pond siting, construction/sealing, cost and resources. It's rare to have someone with his knowledge take time out of their day (1hr 15 minute call) to offer help with no compensation.

I know this post reads like a review, but I'm very appreciative of the guidance teehjaeh57 offered and wanted to recognize his efforts.

Thanks for the suggestion to reach out to him.

Velvin and Weeks Engineers there in Athens can run the numbers for you. They did our hydrology study.