Activate/deactivate Ultrasonic sensors with ArduinoUno/Xbee S1 modules

So what I’m trying to do is to measure the water level at six different points in a canal, the canal is approximately 6 ft long, 5 inch wide, 10 inch tall…

For each sensor I’m using HC-SR04 Ultrasonic modules connected to Arduino UNO and I’m sending data to my laptop with Xbee series 1.

The laptop has an USB Xbee explorer and is configured as coordinator, Arduinos have their own respective shields and Xbees are configured as end devices.

I’ve made successful tests with just one sensor (accurate measures), but when I try to connect more sensors I start getting wrong readings, I suspect the ultrasonic sensors interfere with other’s signals.

Is there any way to “ask” for each one’s data while the others go to sleep or get momentarily deactivated? For example first ask for sensor1 data, that means that all other five are sleep or deactivated, then ask for sensor2 (1,3,4,5,6 deactivated).. sensor3 (1,2,4,5,6 deactivated)… and so on.

Any suggestions on how to achieve this?