Water Quality at Nacimiento del Rio Frio and La Florida springs

Bar graphs of selected water quality parameters from a series of springs in the general vicinity of La Florida, Poza Azul and Nacimiento del Rio Frio, and from the cave from which blindcats and other troglobites were collected, indicate that the cave water is of different origin, though it is located very near the uppermost springs above Poza Azul.

Bars in the following graphs correspond respectively to data from a series of springs below the cave in order from left to right as follows: headsprings 1 - 11 (numbered in order of increasing distance from the cave as one proceeds downstream toward Poza Azul), Poza Azul, side spring (about 1/3 of the way from La Florida to Poza Azul alongside road), pump spring at river (La Florida), and (following a gap in the graphs) both shallow and deep waters of the stratified sump in the cave.

Water quality from springs and cave at Nacimiento del Rio Frio and La Florida. Bars on left represent springs, and the two bars separated to the right represent shallow and deep cave water samples, respectively. Click on any chart for a larger image.
Temperature
temperature bar chart		 Specific conductance
specific conductance bar chart
pH
pH bar chart		 Dissolved Oxygen
Dissolved Oxygen bar chart
Redox Potential
Redox Potential bar chart

Water quality profile from the cave above Nacimiento del Rio Frio. Click on any chart for a larger image.
Temperature
temperature bar chart		 Specific conductance
specific conductance bar chart
pH
pH bar chart		 Dissolved Oxygen
Dissolved Oxygen bar chart
Redox Potential
Redox Potential bar chart

We conclude:

  1. The water emerging from the springs is NOT from Rio Frio cave. This is especially evident in the temperature and specific conductance data.
  2. The water from the springs appears to come from significantly deeper depths than the cave. Both temperature and sp. cond. increase with depth in the cave water column, but still do not approach values from the spring water.
  3. The water from all the springs is generally similar suggesting a common source.
  4. The cave contains two distinctly different, but homogeneous water masses separated by a sharp (<70 cm wide) boundary layer. The upper layer extends from the surface to 39.8 m, while the lower layer begins at 41 m and continues to at least 45 m.
  5. Temperature, specific conductance, dissolved oxygen and redox increase from the upper to the lower layer, while pH decreases.
  6. The cave water is apparently a perched sump, completely isolated from the aquifer which discharges through the complex of springs located within 200 - 1500 m of the cave.
  7. Cave biota, especially the catfish, are more abundant in the deeper layer.