organisms because of habitat destruction, changes in water quantity, and water quality degradation and the introduction of foreign species looms large (Dudgeon et al., 2006). The risk of future extinction of freshwater biota is projected to be five times higher than that of terrestrial biota and two times higher than that of coastal mammals (Ricciardi and Rasmussen, 1999). At the core of these challenges is hydrologic science.


Hydrologic science or hydrology is, at its most basic level, the “science of water” that embraces topics from research on fundamental processes through operations associated with flood protection, drinking water supply, irrigation, and water contamination. The National Research Council (NRC) report Opportunities in the Hydrologic Sciences, known as the “Blue Book,” defined hydrologic science as a distinct geoscience—“a geoscience interactive on a wide range of space and time scales with the ocean, atmospheric, and solid earth sciences as well as with plant and animal sciences.” However, hydrologic science is also firmly anchored by phenomena that have direct and important relationships with the well-being of humans and natural systems. In fact, as noted by Thomas Dunne, hydrologic science:

will remain vital only if (1) it discovers new phenomena, processes, or relationships governing the behavior of water and its constituents and (2) it focuses on real hydrologic phenomena, such as floods, droughts, drainage basins, material storages and fluxes, and even large-scale engineering effects such as streamflow modification, soil conservation, or channel modifications (NRC, 1998).

Hydrologic scientists are driven in their research by curiosity about how the natural environment functions. How water shapes landscapes is intimately interrelated with life on land as well as in water bodies and is a primary ingredient in the planet’s climate engine. Some of the curiosity, however, arises directly from a desire to solve problems associated with a variety of hydrologic phenomena, as suggested by Dunne. This blend of “curiosity-driven” and “problem-driven” research in hydrologic science is one of the aspects that makes the field so vibrant and exciting and represents a defining feature of the future challenges and opportunities for the field.

“[Water is the] elixir of life, the climatic thermostat and the global heat exchanger.”

Opportunities in the Hydrologic Sciences, NRC, 1991

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