If you are thinking organic for a solution to your water hazard, Peat Moss is a great sponge and water retainer. My dad used to buy the stuff in bales. You'd cut the end of the bag off and the contents would explode out all over everything due to it being compressed as it was stuffed into the package. During the back fill on my new gas line a year or so back, I added an intermediate layer of Peat to the trench to act as a water barrier. Instead of just oozing its way down to the water table, the peat holds the water in suspension and gives the surrounding soil a better chance to absorb it instead of just shedding it. Stuff is great for flower and vegetable beds for the same reason. You can even "sweeten" it by adding cow or sheep sh*t to the mixture. There is a plant in Manitoba that processes and sells the stuff; minus the stench, of course. Or you could find a nearby farmer that has excess he wants to dispose of. My vegetable garden is on hiatus right now due to various reasons but it will be getting another injection of Peat 'n' Cow soon as the frost goes out and the snow quits for the season; maybe around Labor Day. (LOL)
Nick
Nick