WRDB can add computed values of DO saturation, DO deficit, and percent saturation to a Working table. DO saturation, expressed in mg/L, depends on water temperature and salinity. WRDB uses the 1985 APHA formula assuming fresh water and mean sea level. The formula is:
TK = Temp + 273.15
DOSat = EXP(-139.34411 + 1.575701x105/TK - 6.642308x107/TK2 + 1.243800x1010/TK3 - 8.621949x1011/TK4
DO deficit is simply the difference between the observed DO and computed DO saturation concentration. Percent saturation is the ratio of observed DO to DO saturation value, expressed as a percent.
To compute these values, you must first compile a set of simultaneous observations of DO (mg/L) and water temperature (ºC) using one of the methods described in Output Data Overview. You may compile the data from several sources and place them in a Working table using the Save to Table function. PCodes in that table other than DO and temperature will be ignored. Prior to computing the values, open the Working table where the input data have been compiled and computed values will be placed. Select Edit | Calculate | DO Saturation to start the step-by-step process of performing the calculations:
Use this screen to specify the PCodes that correspond to the input data (DO and temperature) and the PCodes for values to be computed. The drop-down lists contain all current valid PCodes in your Project’s PCode Support table. If you don’t already have PCodes defined for the calculated parameters, click Cancel and add them to the Support table. You may choose "None" to suppress calculation of one or more parameters. Finally, select the desired CCode to be assigned to each computed value from the list taken from your CCode Support table. Click Next to continue and see the next screen:
This screen shows you a list of simultaneous DO and temperature values found in the Working table that will be processed. Click Finish to see the final confirmation screen:
To avoid duplicating data, all data in the selected Working table having the specified DO saturation PCodes will be deleted before the newly computed values are added.