Why the dry spots occur on the tees

Some of our recently constructed tees are showing signs that we are in a severe drought.  The brown spots are localized dry spots.  Everyone usually thinks well you have irrigation, what's the problem.  A lot of golf courses have irrigation heads that are improperly spaced, causing irregular or poor coverage.  We are trying to change runtimes, use soil surfactant chemistries, hand watering and irrigation nozzles to improve coverage.  The main problem is located just below the surface.  Look at the picture above.  There is a LOT of thatch in the tees.  We just purchased verticutting reels to aleviate this problem.  We will start this fall to remove the heavy thatch.  Thatch is one of the leading causes of dry spots.