Fish and other aquatic animals require oxygen to breathe. Too little oxygen can result in large scale fish kills. Conversely, too much dissolved gas, for example at the spillway of a dam where water falls a great distance, can also be dangerous to aquatic life. Fish entering oversaturated waters may contract “gas bubble disease” whereby gas becomes entrapped in the blood vessels, which can rupture and damage internal organs or burst swim bladders.

An effective monitoring system provides real-time DO and/or total dissolved gas (TDG) measurement data with alarms for early warning when threshold values are approached or exceeded. Saturation levels are temperature-dependent, and external factors such as algal growth can also have a significant effect on gas concentrations.

For complete oversight at hydropower dams, sensors are typically placed at various sites upstream and downstream of the dam. Individual sensors for temperature, DO and TDG may be deployed, or these can be combined into multi-parameter instruments such as Eureka Manta+ water quality sondes, which can be expanded with many other sensor types such as pH, turbidity and algae.

Sensing instruments may be mounted on floating buoy platforms or directly to dam structures with perforated deployment pipes allowing flow through to the sensors and ease of access for maintenance and calibration. In either case, a NexSens X2 data logger wirelessly transmits real-time data via radio, cellular or satellite communications to the WQData LIVE web datacenter for data management and alarm configuration.

The X2 logger is compatible with most industry-standard DO and TDG sensors including those from YSI, Eureka, In-Situ, Pro-Oceanus, etc and includes multiple sensor ports to accommodate situations where sensors are at multiple depths or expansion with other sensor types such as weather stations.