The word "hydrologic" refers to anything related to water or the study of water. It is often used to describe things like water systems, cycles, or patterns. Full definition
Energetic constraints and response of hydrologic cycle to climate change. (climate-dynamics.org)
Markus leads the effort at PCIC to quantify the direct and indirect effects of climate change and variability upon the various components of hydrologic cycle at the local and regional scale. (pacificclimate.org)
I worked with climate data in hydrologic model development and calibration at a NOAA National Weather Service (NWS) River Forecast Center (RFC) from 1976 - 2005. (realclimate.org)