Here are some resources regarding soil water capacity that may be of help.
http://www.nrcs.usda.gov/Internet/FSE_DOCUMENTS/nrcs142p2_051279.pdf
http://www.nrcs.usda.gov/Internet/FSE_DOCUMENTS/nrcs143_019175.pdf
Here is a resource explaining how to test the quality of your soil
http://www.nrcs.usda.gov/Internet/FSE_DOCUMENTS/nrcs143_019175.pdf
Most of these are geared toward agriculture, but still apply to turf.