Learn More: pH

What does this mean?

pH is a scale of numbers from 1 through 14 that is used to indicate the acidity of a water resource. Water is said to be acidic if the pH is below 7, and basic when the pH is above 7. A pH value of 7 is considered neutral, which means it's neither acidic or basic. Waterbodies in the low end of the pH scale are of particular interest to scientists concerned about the effects of acid rain on aquatic plants, fish and wildlife.1

"pH" stands for "potential of hydrogen". A pH measurement has no units associated with it. The 0-14 pH scale is logarithmic and inversely indicates the concentration of hydrogen ions in a solution.

1(Definition taken from LAKEWATCH Circular #101: A Beginner's Guide to Water Management — The ABCs: Descriptions of Commonly Used Terms)

How are the data collected? (Methods)

pH can be measured in the laboratory or by continuous-monitoring sondes.

"Near-real-time" water quality sondes are typically mounted such that the bottom of the unit is located approximately 1 to 3 feet below the water surface. The instrument is either mounted to a fixed pole system or a fixed buoy that is moored within the lake or river. The units are under a maintenance schedule to ensure proper functioning of each sensor.


Caveats and Limitations

Because the near-real-time water quality data presented on the Water Atlas goes through a series of transfers before becoming available, there can sometimes be a time delay in presenting the data. Additionally, if the water quality stations or computers transferring the data are tampered with, this may cause problems in being able to present the data in 12 hour increments. In addition, the data do not undergo the same level of quality control as other data sets prior to being presented on the Atlas. A caveat of using near-real time data is the possibility of error. Near-real time has not undergone as many quality control procedures common to our other data sets. Therefore, occasionally due to equipment malfunction there may exist errors within the data. Every attempt is being made to mitigate these errors before they occur.

Additional Information