WATER-QUALITY DATA: Publication of Water Temperatures 

                                      March 13, 1975


Subject: WATER-QUALITY DATA:  Publication of Water 

The question of publication of negative water temperatures in 
Geological Survey basic-data reports has recently been raised 
by some WRD District personnel. This memorandum is to provide 
guidance to Districts in deciding whether or not to publish 
negative temperatures.

Review of pages D-143 through D-182 in the 49th edition of 
CRC's Handbook of Chemistry and Physics provides a basis for 
evaluation of freezing point depression associated with 
increased concentrations of various chemical constituents. As 
an example, concentrations of potassium chloride (KCl) and 
sodium chloride (NaCl) are used to illustrate the freezing 
point depression. Solute concentrations of 10,000 milligrams 
anhydrous KCl or NaCl per 1,000 grams (approximately 1 litre) 
solution will result in a depression of the freezing point by 
0.46 or 0.59!C, respectively. The relation between solute 
concentration and freezing point depression is linear to 
concentrations of 30,000 milligrams/litre of KCl and NaCl.

Supercooled conditions can exist in streams characterized by 
turbulent flow conditions, but generally this condition alone 
will not result in temperatures colder than -0.1!C.

In summary, conditions may be found in which water 
temperatures of less than 0!C are measured. Negative values 
of water temperature in the range of 0!C to -1.0!C should be 
published in Survey basic data reports after they have 
received a thorough review and their accuracy verified. Any 
values less than -1.0!C are highly questionable and should be 
published only after a complete check of the calibration of 
equipment used and discussion with the respective Regional 
Water Quality Specialist.

                               R. J. Plckering

WRD Distribution: A, B, FO-L, PO