I am looking to buy a reel sprinkler but I do not know anything about them.  I will be using this to water my arena.  I am hoping someone here can educate me.  Any and all info would be appreciated.

works great as long as you have the volume and pressure to run it correctly. 

most need power or generator to power the reel or pump to increase preasure.

I have always used a regular rain bird type sprinkler head with a tri-pod setup attached to a garden hose.  Only downfall is you do have to watch and move it around or get the inevitable soggy spot.  I did a quick search and found a company in Oklahoma that has a roll up watering system....Micro Rain on Facebook.