I posted earlier about my 2000 TDS well. The high level of brine from disposal wells is the culprit. I’ve since been brainstorming for options to utilize that expensive hole I had drilled. I’m curious if anyone has used a shallow marsh planted with halophyte grass like cordgrass to clean their irrigation water? I have a low area uphill from my pond that drains into it after heavy rains. I would dig out that area, let’s say 100’ x 50’ x 2’ deep and line the bottom with clay then soil and peat and topped with sand, no limestone. Any thoughts?

Dilution of the brine with fresh water is the only way I know of to reduce chlorides. Maybe a shallow water well can be used to dilute the chlorides. The shallower well will usually pick up less salts from the earth. But you will need shallower water sands.

You may want to read about the Sultan Sea...

The issue with salinity in a marsh is evaporation. The water evaporates, the salt doesn't. With a clay bottom and that much surface area, you might as well get a contract with, Mortons, you'll have a salt marsh in a decade.

Smooth cord grass is a halophyte. It actually removes salt from soil and stores it.

If you think it will work, go for it. Quite possibly, during summer, when evaporation rates are 0.25"/day on a 2' deep marsh, thus doubling the salinity every 96 days, those halophytes should have no problem keeping up. Not to mention they are the Ponce De Leon's of plants and never die and release the salt back into the marsh.

Just in case, I would grow some fine Indian pepper on the banks.

Something like this might work but maybe the situation isn't as dire as it may seem. Different fish tolerate different levels of salinity. Some do fine in brackish water even though salinity often limits reproduction. So I will offer you another alternative that may allow you to "roll with the punches" that your pond, well, and desert vortex are swinging.

Consider fish that can tolerate the pond conditions that you are facing. An interesting fish for this purpose are Hybrid Striped bass. The sunshine version, the one commonly available for pond stocking can tolerate salinity up to 41% seawater without losing any osmotic function. This is due in part to the fact that one of its parents tolerates full strength seawater. A fish like this doesn't even "have to have" prey, you could feed them everything they ate if you had to. So let's get a sense of the salinity of your well. Seawater has a TDS of 35000 and so your well at 2300 is 6.5% that of seawater and 16% of the TDS that the sunshine version can tolerate with no loss of osmotic function. Two references you can look at:

Salinity Tolerance 1

Salinity Tolerance II

If you read up on other species that you prefer, you may find they tolerate salinities higher than your well water and the window they can thrive provides a cushion that allow you to buy time while you top off your pond with the well. Though evaporation will increase salinity, any rain event that overflows the pond will dilute it. So you just need fish tolerant enough to get you to a rainy period that is bound to come sooner or later. I only mention tolerant species because these provide much greater windows of time because they could thrive in water more than 3 times greater than your well water.

Joey mentions the Salton Sea, but there are MOZ Tilapia there thriving in water more saline than seawater. Hey you could grow them and keep seed in your home to overwinter in aquaria. Red Shiner are also a good choice. A member here named Ken (handle Snipe) lives in Northwestern KS and cultures them for sale with his consulting/hatchery enterprise. This prey species will thrive in salinities more than two times your well water. So just some ideas that may help you to make lemonade and have some fun while you are doing it.

Could someone with better math skills than I convert that salt TDS to % mg/l? All fish do well in up to 0.9% salt solution - that is the salt solution of their blood.

esshup, I wasn't familiar with TDS units so I googled and found that it is usually expressed in mg/l (parts per million). Salinity is more often expressed in parts per 1000 (g/l) but it is easy enough to multiply by a thousand to convert to TDS, mg/l, or parts per million. I google the TDS of seawater and it is 35000 parts per million (mg/l)

Just to be clear, TDS is NOT Total Dissolved Salts, it IS, Total Dissolved Solids. Usually, TDS is comprised of calcium, sodium, potassium, phosphates, nitrates, chloride and a thousand other orgnanic and inorganic molecules. The OP mentioned "brine" so I ASSumed his main Dissolved Solid was sodium/chloride. There is no way to calculate salinity from a TDS reading. If I knew the electrical conductivity of the water and a few other parameters, I could guesstimate the salinity.

Desalination in large quantities is ridiculously difficult and energy consuming. When you have a closed system, like a pond, salinity will exponentially increase via evaporation. Do you know how the salt on your table is made? Evaporation of shallow, large surface area sea water ponds like the OP is proposing.