Well then.

[jennlk]

So I seem to have solved the "leak" in the rill. Yesterday I was outside doing yardwork, part of which was pulling some of the weeds & grass that had grown up between the rocks. They pulled out very easily, from essentially mud. I thought that was weird, because the old leak is only about halfway up the rill, and there's no real way that the top of the rill should be soaked from that (water doesn't wick up dirt/sand piles that well, after all). I poked at the rill, and noticed that there was a small puddle behind the weir at the top of the hill. So I moved the flagstone that's over the weir, and realised that the water was splashing over the back of the weir because the bio-filter bag was so badly clogged. I pulled the filter bag out, weighed the fiber filter down with some fist sized rocks, and replaced the flagstone. That was over a day ago, and the water level has not dropped more than one would expect from evaporation.

I suspect that we'll still rebuild the rill, but it's not as critical.