The new swale was holding back a lot of water when I checked it this morning after a 2-inch rain. It looks like it worked exactly as designed– it slowed down the water runoff, and let the water sit long enough to allow insoak. The fig trees I just planted on the high end will have access to huge amounts of water stored in the soil for weeks to come. The standing water should disappear in a few days, so the risk of mosquitoes laying viable eggs is small.