The quality of this substance is often measured using its turbidity, which quantifies its cloudiness.
The HBV and WAFLEX models are used to mathematically simulate the effects of this material. This substance's "juvenile" form may come from extraterrestrial sources, such as asteroids. A circular apparatus that is divided into two black and two white quadrants called a Secchi  (SECK-ee)  disk is used to analyze this material. "Meteoric" sources of this substance enter the zone of saturation and join the phreatic or vadose zone of layers in the Earth. In general, the rate of (*)  transport of this substance through a porous medium is given by Darcy's law. The quality of this substance is often measured using its turbidity, which quantifies its cloudiness. For 10 points, name this substance, which undergoes evaporation, condensation, and precipitation as part of its namesake "cycle".
The HBV and WAFLEX models are used to mathematically simulate the effects of this material.
water  [or  H2O ] 