Monitoring the quality of rivers and lakes is becoming more and more important as enviornmental concerns increase. A good dissolved oxygen transmitter used properly is one of the important tools to use in this regard. You may want to look at http://www.ecy.wa.gov/programs/wq/plants/management/joysmanual/4oxygen.html for some useful techniques.
Water Quality Sensors
The following Water Quality Sensors are available that fit your specifications. Please click on a sensor model name below to read more about that water sensor.