This might be a bit gruesome, but why not shoot the snakes the on site? That seems way easier and faster than physically wrestling dangerous snakes sometimes bigger than yourself, throwing them in your truck, and shooting them in your garage. Is it just the solemnity? The chance of missing and it escaping and the difficulty of wrestling with a gun?
I imagine you'd end up with lots of leaded bullets in the water, over time. Naturally lead + water = bad. Note: I know about this because there's a gun range near where I live by the lake, and the lake is now permanently off limits for swimming due to lead pollution.
In a recent conversation over breakfast I brought up lead poisoning and my dad was adamant (in his conspiratorial way) about how all of that lead exposure via handling lead and inhaling lead fumes didn't result in any significant health problems for us. I'm assuming he meant that we all weren't dead yet. He's 80 and a wreck. He's had all sorts of health issues include recent cancer remission. I'm 55 and I've had nerve issues since my teenage years which manifests itself as a noticeable tremor in my right hand that has got worse over time. I developed adult onset asthma in my late teens. I have a host of other health conditions as well. Who knows how much of that is tied back to lead exposure.