Pond Boss Forums GENERAL QUESTIONS Water chemistry Well Water?

I am a new subscriber to PB and new to the PB Message Board!

I have a new client with a 15 ac. lake that was used for irrigation by putting well water continuously (600 gal/min) into and then pumped out for almost five months. Approximately 18 months ago it was stocked heavily with bream and minnows and was assumed to be ready to stock with largemouth bass. This is why I was invited in, because the lake owner said very few fish are visible and no dead fish were ever obsereved, so the hatchery wanted me to shocked it. I found very few minows and even fewer bream. The pH is just above 10, Alkalinity was near 50 and hardness just above 100. No shoreline vegetation present, but some Southern Naiad is covering the bottom, but is only a foot or so off the bottom, not growing like I would anticipate, unless the well water is slowing its growth? The water is crystal clear. Most of the stocked fish have perished due to the amounts of well water applied to the lake. The DO is now around 6 at dawn. My question is - will the pH gradually come down on its own, or is there an application of something that should be applied to help it get back within a desirable range? I have dealt with many lakes needing the pH raised, but never one needing it lowered? The landowner has agreed to remove the lake from the farm irrigation system, so that too much well water will not be a problem in the future, but for now what are your suggestions?

Thank you in advanced for any assistance.