National Water Center, Eureka Springs, Arkansas
         

National Water Center, Eureka Springs, AR

Updated: April 2014 Contact: Contact: NWC

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Capturing Rainwater: A Dialogue on Karst Topography, Well Drilling and Rainwater Catchment in the Ozarks

by Jim Marple

Barbara Harmony: The Problem

The discussion on rainwater is of interest to me because I am trying to decide whether to drill a well after having used a cistern for 22 years.

I live in Northwest Arkansas, a karst geography. To drill a well would go about 900ft and cost about $10,000. It is possible to get a low interest FMHA loan to drill the well. It does not seem to be possible to get a low interest loan for improvements to the existing cisterns. There is one 1500 gallon cistern and one 5000 gallon cistern. The water from the roof of the house collects and goes through a fifty gallon drum before going to the 1500 gallon cistern.

I have screens and fabric stretched across the top of the drum. It does not screen out oak pollen which is present in the spring at a rainy time of year. The oak leaves and acorns also turn the water black in the fall. I am currently thinking of a sand filter down in the cistern, a new coat of cement to line both cisterns inside, a layer of cement for the top of the 5000 gallon cistern, a new shed roof to collect water to the 5000 gallon cistern, a filter at the pump and a new filter at the sink. I do not have an estimate for this but am guessing it might be $5000. I get drinking water from a neighbor's well but would like to be able to drink this water from the cistern.

I would appreciate advice and opinions from this group.

Jim Marple's Solution(s):

Surely, you jest. With at least a four-foot rainfall scattered through the year you can't seriously consider a 900' well. No responsible expert would have given this alternative more than passing mention.

You almost certainly have all the reservoir you need to store adequate water directly beneath your home site. Your local office of the USDA Natural Resources Conservation Service should have a district conservationist who will come to your site for a full evaluation of its potential to store rainwater. This specialist should have the expertise to show you how simple berms of soil or low rock-brick-board walls will retain most rainfall and let it soak into your soils and how to manage underground flows by siting percolation fields to 'mound' water so that your well gets a clean inflow while your septic field drains away underground. You probably won't need curtain drains or subsurface dams but these are a cheap option if your conditions are unusually contrary.

These public servants may not have direct experience in extracting water percolated to shallow aquifers but if you work with them, listen close - take lots of notes - offer coffee and chocolate cake; you will find what you need to know about soil depth and consistency and that is the key. These techs probably won't have much knowledge of extracting water as I suggest, it's not in their job description, but you can find what you need on the net and at your plumbing store - enough to formulate a sensible action plan.

Can merely grading your site produce enough clean water? Your roof will produce basic needs so if you guide underground all rain falling within 20 feet of the house you'll have enough to water your garden, wash your car and keep your swimming pool full. Unless you are on a really steep side hill over bedrock, storing this water is no great task and unless your soils are quite unusual they can filter inflows of rainwater adequately. You may want to do some planting to enhance percolation/filtration and should already have an RO unit on kitchen taps to catch the germs that may sneak into any system.

Here's what I've done!:

1)    I wanted water at a remote lot so hooked the hose from a portable pump (fed by a recirculating hundred-gallon pond I dug) to a 2" pipe and "jetted" a hole 20 feet deep within twenty minutes. Dropped in a pipe, fed a 1/2" hose down through it and attached to an ordinary sump pump. Bo coo water fed to a pressure tank. 

2)    For another site, I bought a $1,500 Deeprock rig and bored through boulders and clay to 45 feet. No run-dry problem because I graded these sites to retain and percolate all rainfall. On one lot I dug a 14' deep hole, threw in a $350 Sears submersible pump and a yard of gravel, and buried them. Lotsa wata.

3)    On several others I pounded drill points down twenty feet and was in business with a battery-powered mini-pump costing just $75.

While these installations were for irrigation water, the soils and terrain are such that the water would be potable should this become appropriate. I certainly see no reason to do as my neighbors have done, boring hundreds of feet down, sometimes coming up dry, other times reaching nasty-smelling water, always having to pay the high cost of pumping from deep down.

No, my methods don't work anywhere. You may only have a few feet of dirt overlying bedrock, have steeply-sloping rock strata or have 'tight' soils that don't store water well. If so, you will either need to be imaginative or pay someone who is. But if you can visualize the soil as your reservoir you will be able to figure out how to tap it most effectively.

Try this:

Do a diagram, a 3D sketch from estimates of the depth of topsoil and the slope of underground bedrock. Add up the square feet and multiply by the average soil depth. Guess at the capacity of that soil to hold water from the NRCS description, probably somewhere near 1-3 quarts per cubic foot and you will have a very rough estimate of your reservoir's capacity. You'll need a water-level-controlled switch on a shallow well that produces just 1/4 gallon per minute but it will provide all you need unless Arkansas days are a lot shorter than 24 hours. If conditions are really adverse, you'll need more than one shallow well but look at the good side, this cuts pump wear and tear in half.

Of course, water supply professionals will insist you must drill deeply. They need to make their rig's payments and be compensated well for boring work. And, civil engineers argue against such simple installations - low-tech isn't taught in their schools. If an engineer were to show a client how to become self sufficient in water supply by retaining runoff that would otherwise accumulate downstream as floodwater, that client might give away this knowledge free to neighbors. They might even get together to build simple systems that eliminate flooding and so eliminate the need for engineers! That engineer would be shunned by peers, castigated by his profession, forced to face life with only personal integrity as a companion.

Jim Marple