Building a WSN in Haiti

I am part of a team building a wireless sensor network consisting of 8 end points at 8 water fountains and a central command module in a village in the Central Plateau in Haiti. Our purpose is to monitor the water quality in the water system at points closest as possible to direct access. We have decided to use the Xbee modules as our communication device but need help regarding the hardware setup with the sensors. We are measuring pH, chlorine, turbidity, and TDS. Does anyone have suggestions for the best sensors to use and the best way to hook them up? Any help is greatly appreciated.