Pond Boss Forums POND CONSTRUCTION Selecting a site Pond near ag land - concerns?

Chet:

There are three things I can think of to be concerned about with when you have a pond that has cropland for it's watershed: 1) fertilizer, 2) pesticides/herbicides, and 3) sediment.

As Trent pointed out, the condition of the existing 1 acre pond over the course of the (agricultural) year would probably be the best indication of how the runoff would affect it if you enlarge it. Anecdotal evidence would be better than none, pictures would be better (although even if they were digital pics with a firm date code, how do you know if they portray typical, good, or bad conditions?).

If the current pond does not have a problem with super-dense algal blooms from fertilzer (and hence possible eutrophication and resulting fishkill) or a big sediment input from runoff, you know that the existing buffer zone between the pond and the ag land has probably been sufficient to screen these two problem sources. Will your expansion of the pond reduce the width of the buffer zone? If this is the case, you could possibly improve the effectiveness of the buffer strip per unit width by changing it's composition. Tall, thick grass is a better buffer than short, over-manicured grass. Woodlands, which unfortunately take a long time to develop, are probably the best buffer strip of all. You might want to put in a sediment trapping pond or wetland upstream to catch as much of the three problem sources as possible before they can impact the main pond.

Pesticide and herbicide effects I am not very experienced with. Their presence in the pond would cause me to limit the amount of fish I ate from it. I think they tend to persist in the sediments on the pond's bottom; you could possibly have samples of the current pond's bottom muck analyzed for 'cide content. If the current pond has a healthy population of frogs, that is probably a good indication that there has been minimal 'cide application into the pond, as amphibians tend to be very susceptible to health and breeding problems due to these chemicals. OTOH, an absence of frogs could just mean the fish in the pond are eating them (bass especially). I think, but have no evidence to support, that a buffer strip or wetland that does a good job of screening sediment and fertilizer from the pond would be more effective at keeping chemicals out of it than a poor buffer would.

Another indication is what the ag land is being used for : past, present and planned future activity. Hayfields and pastures (which make up most of the watershed for my pond) have minimal impact - a fairly small amount of sediment washes off, they might get limed yearly at most (which would probably be a benefit to the pond), and they might get fertilized in one large chemical application per year or have manure applied round the calender. Manure (and, I think, fertilizer) during growing season will have very low impact on the pond, while manure in Winter, especially if spread over ice/snow, could have a big effect. Pesticide application is probably nonexistent or very low (I only have to worry about this a little during my wife's annual Roundup Rampage - she is very good about not spraying close to the pond).

Conventionally plowed and planted fields will send all three kinds of input (fertilizer, 'cides, and sediment) into the pond. This ag use has the potential for the largest sediment input. No-till fields will have a much lower sediment input, but probably the largest pesticide/herbicide application. I personally consider no-till the least desirable ag use to have upstream from a pond, and hayfields the most desirable.

Do the fields have drainage tile that empties into the pond? These provide a direct shortcut into the pond for the three types of problems, which I don't believe could be compensated for with an above ground buffer zone. Heavy sediment, 'cide, and/or fertilizer loads heading for the pond through drainage tile would in my mind pretty much necessitate an upper sediment pond or wetland.

I do not mean to completely scare you off from ag land in a pond watershed. A mature forest is probably the best watershed for any pond to have, but I would rather have ag land for my pond's watershed than a ritzy rural subdivision (with massive Chemlawn applications and septic system discharge) or a golf course (IIRC, the heaviest chemical applications per acre in America).