You have probably choosen some bad parameters for the blendmapgeneration. The file can be generated for as many water planes you want. Look at OS_HeatHaze, not PP_HeatHaze. I will give an example tomorrow.

Lite-C Tut. 1 Lite-C Tut. 2 Lite-C Tut. 3 (en)
Shader Tutorial (ger)

http://www.slindev.com