Swales not draining in heavy clay

Hey ya'll

Need some suggestions for the site I am at. We dug some swales about a month back in a horse/cow paddock, the soil is heavy clay and is heavily saturated with water. We dug the swales to spread the effluent from the hotel's laundry water. The water is not draining completely, and this is attracting mosquitoes to start a breeding ground.


My ideas:
1. Plant trees on the swales to help suck up this water. We have cows and horses that will be grazing, so preferably something they find palatable, can stand in water and is hardy in zone 7.
2. Fill the swale with organic matter like woodchips so the chips act as a sponge and will not allow mosquitoes to breed.

Any suggestions will be appreciated!

I would start a compost heap in the swales that are not draining.  Compost is THE best thing for losing up clay soil and getting it to absorb water,  If there is a hotel there, maybe you can get the food scraps from the kitchen, add the wood chips and poo.  Cow and horse work just fine and if you are using their paddock they should be around somewhere.  

Also try to integrate organic material into the clay.

Compost isnt really an option as these swales are 100m long. We planted some cover crops on the berms and I a thinking to chop and drop them to add organic matter to the soil. Maybe even spraying it with some comfrey tea to speed up the decompostion process.

The woodchips do help, I did this once with greywater on a smaller scale and it removes all the smell. You could still plant some water loving trees there like american pawpaw or bananas depending on your climate.

Daikon radish has been the best initial cover crop for me in heavily compacted soil, allowing me to follow with more successful runs of fava beans, vetch, and clovers. Woodchips or straw on any bare soil has also been essential.

Gather natural wood, when when swale is dry dig the swale deeper, save dug up clay/soil on tarp or wheel barrow, drop wood into deeper dug trench, cover wood with all saved clay/soil.  You can do this hard work in steps/number of weeks or days..