How big of a well would be good for an 8 acrea pond 6-12 foot avg depth. Would be used to suppliment runoff. Thinking drought times in south east Texas near Houston Area.

Is all of the water loss from evaporation or transpiration? i.e. no water loss from leaks in the pond?

Somebody please check my math.

Thanks to Chris Steelman and FishinRod, here is the explanation behind the numbers.

If all water loss is from Evapotranspiration, then this is applicable for August (for an average year in Houston).
325,851 (gallons in an Ac/ft of water) ÷ 12 (inches) = 27,154 (gallons per inch) x 4 (inches per month Evapotranspiration Rate loss) = 108,617 (gallons per month per surface acre loss) x 8 (surface acres) = 868,936 ÷ 30 (average days per mnth) = 28,964 (gallons per day) ÷ 24 (hours in a day) = 1,206 (gallons per hour) ÷ 60 (minutes) = 20.1 gpm if run 24/7.

Only way to be sure about the water loss is to stick a yardstick in the BOW and measure vertical drop over a few months and compare it to the evaporation rates for that area.

Pond is not completed yet just thinking of putting in a Well in case of drought. Just wanted some experts to tell me the size of well and HP I might need. Water is about 200 foot down.

day,

Water flow rate testing should have been done when the well was initially drilled.

Pumping water from a pond is considered an "infinite" source so you just need to calculate your pumping and piping requirements based on the needs of your project.

Water wells DO NOT operate in the same manner. You can only pump what the aquifer will yield to you - with a large safety margin so that you do not pump the well down to the level of the perforations. (Several bad things can happen at that point.)

Not sure what all your numbers are. A 1/4" loss per day for one acre comes out to 6788.5 gallons. Multiply that by 8 acres comes out to 54308 gallons per day. Divide that by 1440 minutes per day comes out to a 37.7 GPM loss.

The well will have to be provide more that 37.7 gpm to maintain the water level. If you lose a 1/2" per day you would need to double it. I don't know if it is ok to run a well 24/7 so you might want to oversize the well and only run it partially throughout the day. Talk to your well driller about that.

I use a well for all 5 ponds in my area. The big ticket item, as esshup said, is knowing your evap rate from the closest station that records such data. In my case, the summer season ave is .38" a day, so in 1 acre.. so 10,182 gal a day, so 425 gal/hr, so 7-8 gal/min just to stay level considering no other loss such as leak, or terrestrial use. Mine pumps 36 gal/min but I allow a slight fluctuation of about 4-6". My well is also about 90' to water but I'm using 1.5hp in a 5" casing.
Highest efficiency is motor running solid, not a pressure system. To keep up with recovery I think you will need 40-60 gal/min to have the ability to play catch up, otherwise it will just be stable when running, you want to recover loss within a few days or you'll be spinning your wheels. Local well drillers can tell you about rates and HP for your depth.

day 18,

esshup's calculations look correct to me.

[esshup, did you use an August evaporation rate of 4"/month? You might edit your post to indicate that rate. Then someone in an area with a rate of 2"/month can easily adapt your calculations without performing every step themselves.]




Also consider that the evaporation losses (in gallons) will go down slightly during drought periods as the surface area of your pond gets smaller.

The necessary water productivity of a well (and the corresponding electricity bill) will be much higher to keep your pond full compared to maintaining it at some smaller base level just to make it through to the other side of a drought period.

Snipe,

The "well pumping" question gets asked quite often on the forum. I think your situation would be a good illustration to others.

Could you add a few more answers to fill out this thread?

How many pumping days (or hours) do you average per year?

What is your electricity bill for that time period?

What is the average run time between pump replacements?

What is typical cost to rebuild or replace your pump?

What are the installation costs for a pump change?

How would one find the evaporation rates for an area? All good questions. I

Someone told me the following, not sure if it is correct?

To raise the water level in an 8 acre pond just 1 inch, you will need to pump over 217,000 gallons. In dry heat, your pond can evaporate on the order of 1 inch per day, so to maintain 217,000 gallons pumping 24 hours/day, one must pump at least 150 gallons per minute/. Is that correct?

Man that is a lot of water.

Rod, I can add that info but variables are going to bring out the "It depends" statement here..
In 2021 I pumped 1,499,600 gal for .95 surface acres.
694 hours pumped at 7 cents per kwh, ave 788 per month = 55.16/month + service charge and taxes = 95$/month.
My well has been running since 2004, no well problems yet, but 2900$ to install well ready to run in 2004. Probably at least double that now.
Of the 694 hrs, it's random depending on if I need to do a draw down in a cell to seine.
Right now, for 2021, I averaged about 4-5 full days per month in the 7 months I will normally use water so about 250-280,000 gal per month.

217,000 is correct for 1" on 8 surface acres.
And 150gal/min to recover that 1" in 1 day is correct. That's why I said 40-60 GPM to be able to recover, It might take 3 days a week to 10 days to keep up just with evap.

Might look something like this...

July 2021
Weather data collected at the KSU Northwest Research-Extension Center, Colby, Kansas.
Air Temperature, F Soil Temperature, F Water Temperature, F Evap. Wind Solar Precip. Snow Depth Air Temp GDU HDU
Day Max Min 8:00 Wet-B Max Min Avg Max Min 8:00 in. mi/d Rad., ly in. in. in. Spread, F
1 82 65 66 66 75 71 73 82 68 68 0.30 48 361 1.16 0 0 17 23.5 -8.5
2 80 57 67 65 75 70 73 85 66 67 0.14 34 349 0.03 0 0 23 18.5 -3.5
3 84 61 71 68 77 70 74 90 66 68 0.32 53 596 0.00 0 0 23 22.5 -7.5
4 88 62 68 67 77 71 74 89 67 68 0.34 123 626 0.00 0 0 26 24.0 -10.0
5 92 61 70 68 80 72 76 97 68 70 0.25 57 638 0.00 0 0 31 23.5 -11.5
6 92 65 72 71 80 73 77 94 69 70 0.39 84 665 0.00 0 0 27 25.5 -13.5
7 87 64 64 64 77 72 75 84 68 68 0.38 68 302 0.94 0 0 23 25.0 -10.5
8 84 60 68 65 79 72 76 93 66 67 0.24 42 521 0.00 0 0 24 22.0 -7.0
9 95 60 69 66 78 73 76 90 66 66 0.51 157 665 0.00 0 0 35 23.0 -12.5
10 100 61 64 61 81 73 77 N/A N/A 67 0.41 67 632 0.00 0 0 39 23.5 -15.5
11 89 53 62 59 78 72 75 87 62 63 0.36 90 583 0.00 0 0 36 19.5 -6.0
12 81 62 62 59 77 71 74 89 62 62 0.34 55 650 0.00 0 0 19 21.5 -6.5
13 90 60 67 65 78 71 75 93 62 66 0.36 69 669 0.00 0 0 30 23.0 -10.0
14 98 66 71 66 78 73 76 93 66 67 0.45 117 588 0.00 0 0 32 26.0 -17.0
15 88 64 65 65 76 74 75 83 67 69 0.25 76 324 0.00 0 0 24 25.0 -11.0
16 82 62 64 64 77 74 76 89 68 70 0.23 47 415 T 0 0 20 22.0 -7.0
17 90 61 63 63 78 74 76 91 67 67 0.25 85 438 0.00 0 0 29 23.5 -10.5
18 92 62 69 69 79 73 76 94 67 70 0.40 80 617 0.00 0 0 30 24.0 -12.0
19 87 58 65 65 79 75 77 91 67 68 0.30 52 519 0.00 0 0 29 22.0 -7.5
20 88 60 63 61 79 74 77 93 65 65 0.41 64 581 0.00 0 0 28 23.0 -9.0
21 86 55 61 59 77 73 75 89 61 61 0.30 89 581 0.00 0 0 31 20.5 -5.5
22 88 61 69 64 76 72 74 89 61 65 0.40 166 591 0.00 0 0 27 23.5 -9.5
23 95 65 70 64 77 73 75 N/A N/A 67 0.54 156 639 0.00 0 0 30 25.5 -15.0
24 98 64 73 68 77 73 75 91 66 68 0.45 116 593 0.00 0 0 34 25.0 -16.0
25 95 69 69 69 78 74 76 96 68 75 0.38 61 588 0.00 0 0 26 27.5 -17.0
26 84 62 67 67 80 76 78 89 70 70 0.30 72 524 0.00 0 0 22 23.0 -8.0
27 94 62 68 66 79 75 77 95 70 70 0.40 53 608 0.00 0 0 32 24.0 -13.0
28 97 68 74 70 79 75 77 95 70 72 0.43 89 635 0.00 0 0 29 27.0 -17.5
29 101 68 74 69 79 76 78 94 70 77 0.55 120 640 0.00 0 0 33 27.0 -19.5
30 99 66 73 68 80 76 78 96 70 70 0.50 61 645 0.00 0 0 33 26.0 -17.5
31 99 68 69 67 82 76 79 93 70 70 0.45 109 575 0.00 0 0 31 27.0 -18.5
Totals 2805 1932 2097 2028 2422 2267 2350 2634 1933 2111 11.33 2560 17358 2.13 0 873 736.5 -353.5
Avg. 90 62 68 65 78 73 76 91 67 68 0.37 83 560 28 23.8 -11.4
Max 101 69 74 71 82 76 79 97 70 77 0.55 166 669 1.16 39 27.5 -3.5
Min 80 53 61 59 75 70 73 82 61 61 0.14 34 302 0.00 17 18.5

Didn't work, sorry...
I'll find something that makes sense

Try this...
http://hgciatx.com/water-management/

For the Houston area, looks like 1/8" a day evap is about ave in net loss months.

If you had an 8 acrea pond what size well would you recommend?

If I had an 8ac pond that was 100% sealed with very little terrestrial growth near the pond, 50-60gpm would do if 1/8" is average evap and you still have a run off source. If you can't rely on any inflow then 100gpm would be needed or slightly higher. 5" domestic case won't carry that much and cost will be 5 fold.
We have a community lake here with 10 surface acres, with evap and a bit of leakage, 250-300gpm brings it back to full pool running about 1 week per month. No inflow other than actual rain.. we have a 14" annual rainfall and 7-15% humidity is common here.

Thank you to everyone that contributed all of the "data" to this thread.

I realize most data is site specific, but it is still a big help to know what is required in one area!

I will try to link to this thread when I see people asking this same question in the future.

day,

250-300 gpm wells are getting into the range of irrigation wells.

Is there any irrigated farm land around your property?

Your profile does not show your location. Most states have an agency for their water wells and the well information is in an online database available to the public. You should be able to search that and check out some of the nearby wells to your land.

If there are some big wells around you, then your project is possible. You then can get some bids from local contractors to drill and install the equipment sized up for your project.

Love this site. I am in northwest Houston. Used to have a lots of Rice about 20 minutes from me but most of that is now subdivisions. I am just trying to do some research for if and when I might possibly need a well. I think I have enough runoff to fill it but the drought 10 years ago still stands in my mind and thinking of all the investment in fish etc...it would be nice to have a back up plan if and when needed.

So I guess living in the Houston Area evaporation rates would not be as bad because of the high humidity. At least that is what I am reading.

Here is the link for the water well database in Texas.

Texas Water Well Database



They only started in 2001. The data after 2003 is pretty comprehensive.

Correct.

Dry and windy leads to the highest evaporation rates.

If you have some tall pines for a wind break, then that will also help a little. However, if the trees (or other terrestrial plants) are close enough to the pond, then they can also pull down your water level due to transpiration.

I lived in the Houston area for 60 years and usually too much ran was the main concern. If you live where there was rice fields then most will definitely hold water well. Wells are expensive and are not legal in some areas in Houston due to subsidence

So how big of a well are we talking? 6 inch or 8 inch? Hp Recommendation?

To get that kind of flow, you'll be talking 8-10" casing. The well will have a gear head and above ground electric motor or NG fueled Engine, like an in-line 6 cylinder. They are very cheap to run but setting all of this up is crazy expensive.

Can you define crazy expensive? Just looking at ball park? I found a well in that data not far from me that Is at the 400 foot depth that is getting 130 gpm.

Dia. (in.)
165
210
250
290
350
400
6 N PVC CASING 0 400 40
4 N PVC LINER 395 400 40
4 N PVC SCREEN 400 460

Now is the time to contact a local well driller and get some estimates.

You need site-specific information. The costs for drilling and casing a water well depend to some degree on the local geology. The Covid supply chain disruptions may have also raised costs.

I have some equipment that is shut in - due to the lack of a gasket!

Sorry, yesterday was a busy day.

Yes, I calculated the water requirements on an Evapotranspiration Rate for August for that location (Houston). day18, what you need and what you get could be two different things. All areas of the country cannot produce the same amount of water from a well, only a well driller in your area will know for sure.

For instance, Dave Davidson, one of the moderators here can only get (I believe) 1 gpm or 1/10 gpm from his well. So, even for his house he has to pump continually into an above ground storage tank just to have enough water for the house. No way could he use a well to fill the pond. Here where I am at in Northern Indiana, we have a very good aquafier here only 100 feet down. If I care to pay for the electricity, I can pump 2,000 gpm if I dig a big enough well.

I just went over last months utility bill. Our electric costs (Kwh rate, delivery charge, taxes, etc) cost us now $0.239/Kwh. The next county over, that electric rate is $0.209/Kwh. (different utility company)

As for what pump size, that is a big "that depends" question. Even if you wanted to pump 25 gpm, all well pumps are not the same. You have high efficiency pumps and not high efficiency pumps. In other words you could possibly pump the same amount of water with a 2hp pump or a 5 hp pump.

Chris: Here's what the numbers are that I calculated:
If all water loss is from Evapotranspiration, then this is applicable for August (for an average year in Houston).
325,851 (gallons in an Ac/ft of water) ÷ 12 (inches) = 27,154 (gallons per inch) x 4 (inches per month Evapotranspiration Rate loss) = 108,617 (gallons per month per surface acre loss) x 8 (surface acres) = 868,936 ÷ 30 (average days per month) = 28,964 (gallons per day) ÷ 24 (hours in a day) = 1,206 (gallons per hour) ÷ 60 (minutes) = 20.1 gpm if run 24/7.

Data acquired from http://hgciatx.com/water-management/

I have heard that you cannot get more than 100 gpm from a 4" well casing. You will have to talk to your local well driller to get the generalities for a well in your area, and even at that they cannot guarantee how many GPM your well will produce, they can only give you a very educated guess before the actual well is drilled.

To help increase the life of the well, I would recommend putting a double screen on it, AND use stainless steel screen vs. plastic if possible. A double screen will give you twice the amount of screen to pull water through, so that gives you twice the surface area to resist plugging up. A stainless screen can be made with more open area to allow more water to flow through it, so that also increases the efficiency of the well. YES, the stainless screen costs more, but when you look at what the cost of the well is, and what it will cost to replace the screen if it gets plugged, I believe that the stainless screen is cheap in comparison.

Man great information. Thank you for taking the time!! I really really appreciate it. I will call some well companies to get their thoughts.

Spoke to a few people in the area. A 4inch pipe with 5 HP will get you about 90 GPM. I think that would be sufficient for what I need. I really appreciate all the help.

Yep, my well, when drilled, produced 1/10 gpm. But, it does it 24 hours per day. And, I pump it into a 2,500 gallon (I think) above ground container. Then, on to the house 100 yds away. We hit water at 40 ft but drilled down another 50 ft.

I once asked Lusk how long it took for rain water to get down that far from the surface. I THINK he said a couple of days.

I have drilled several wells that fed various ponds. Currently my 2 acre pond has a well that was around 300 feet with strong water. My well guy put in a 3.5 horse pump that does around 35 GPM and it keeps my pond level during the summer when our spring is not running.

I would rely on your well guy - as a side note when my well is pumping 24/7 the electric bill takes a noticeable jump.

Good luck

Thanks y’all will keep you updated on progress.