When we last left our intrepid pondbuilder in west Texas, he was attempting to determine why all the aquatic plants in a customer’s pond were dying and/or failing to thrive. See WGI Online 4.4. Many WGI/VA members generously weighed in online with their expertise in order to try and help Michael solve this perplexing problem.

In between the publication of the last WGI Journal and this one, Michael reports that the pond fish are now starting to die off too, so the problem is starting to worsen considerably.

The final water test results are in and show increased levels of both salts and minerals.

The first sampling was taken in October of 2008, and provided the basis for the initial online discussion with the Victoria Adventure group, and the second water sampling was taken in October 2009. The third column below shows the allowable maximum limits for drinking water as determined by the Texas Department of Health. Results shown as milligrams per liter [ppm].

In what could be construed as understatement, the technician from the independent lab which performed the second test wrote under the comment section; “This water shows salt and mineral levels which could be detrimental to freshwater fish and plants”.

I called Jim Purcell at Oregon Aquatics again with these results since he has experience with hard water and aquatic plants. He mentioned that water hyacinth and lotus are particularly sensitive to hardness, and start showing signs of severe distress at levels as low as 1200 ppm. The pond above tested for hardness at a whopping 3750 ppm which handily explains the rapid expiration of the hyacinths when first introduced.

Since the pond in question is a closed system, the salt and mineral levels will continue to rise as these recent results seem to suggest, and the fish are already starting to die off this year, presumably as a result of the increased toxicity. The annual rainfall in this part of Texas is only 15 inches (38 centimeters) per year, so the possibility of a partially mitigating freshwater infusion, or even a rainwater harvesting system doesn’t seem too practical.

What caused this saltwater intrusion into the groundwater? There doesn’t appear to be sufficient data at this point to be certain, but geologist and Victoria Adventure list subscriber Aaron Hicks in an earlier statement had this to say about a possible cause ... since this problematic pond is situated in the heart of Texas oil and gas country;

“I hail from natural gas country in western Pennsylvania; with the natural gas frequently comes "brine," a salty solution that must be captured and disposed of properly ... These salts are left behind from the oceanic deposits which form the shale layers, which then undergo post-depositional changes that produce the hydrocarbons we value so highly, i.e.: natural gas and oil. These products are pumped together (hydrocarbons + brine), the brine set side for reinjection into other wells that are usually dead for many years, and the natural gas and oil then go on to make valuable products like shiny plastic junk.

"With this in mind, a repeat water test -- along with a panel for heavy metals -- is recommended. Either the well has tapped into marginally saline waters, or there is some oil/gas drilling contamination or drainage or somesuch.

"I would suggest the reason why the terrestrial plants are doing OK is that the exchange capacity of the soils is, for the time being, accommodating these element problems. If the area is desert dust-to-lawn, the surface soils are probably reasonably accepting of these ions, but their capacity will likely be met at some point. From there, they too may succumb. The pond plants, with a very low soil:water ratio, have met their match already”

Michael followed all of the VA group’s earlier collective recommendations* except the heavy metals test which might have confirmed Aaron’s theory. He didn’t taste the water either, and after seeing the test results, perhaps it’s better that he didn’t? The comments from the testing lab tech appeared to obviate the need for an extension agent to independently evaluate this situation.

* A) Repeat the water tests and include salinity, heavy metals, & copper
B) Taste the water ... hey ... you're a CAC!
C) Forward the test results, assuming the new ones are consistent with the previous ones -- to the local extension agent and have him come out there if he will. This is a free resource so why not?

I really don’t know what can be done at this point to “salvage” this pond as salt and mineral levels are likely to keep increasing, making even saltwater tolerant plants a questionable proposition at some point if not already ...

If anyone has any ideas that would help Michael at this juncture, please write WGI or share them on the Victoria Adventure email list.