I've seen this before and I do plan on trying something similar in the future. I don't have a tractor either or I would have dug some swales at this point. I dug a very small pond at the base of the natural swale on my property but it's only filled up twice in 6 years. I just keep trying stuff. I'm not allowed to utilize the aluvial water and the water table out there is around 380 feet so wells are quite expensive. 

 How’s the soil? Able to dig by hand? 

 To a point. Since it was a cropland when I got it there is a hardpan about a foot and a half down. I typically dig holes starting with a gas powered auger and once I hit hardpand I fill the hole with water and come back the next day. It takes 4-5 days to get a 3 ft hole. Good thing I'm not in a hurry. 

 Crazy! Yeah you need a big excavator for a day :). 

 Maybe a nice pit of biochar and manure could get a tree going.