Water quality of Piner Creek is characterized by pH levels that are mildly basic, with upper reach pH levels about 8.5, declining to lower reach levels at 7.8 just above the discharge to Santa Rosa Creek. The headwaters soils are typically of pH about 6.9. Water quality of Piner Creek is generally low in turbidity, except for highest flow periods resulting from heavy rains; the water is free from odor. Springtime water temperatures are typically in the range of 60 to 65 degrees Fahrenheit (16 to 18 degrees Celsius).