One of the things that struck me as odd when reading the descriptions of the elements, was that Water was described almost exclusively as having to do with entropy and decay. This is not really something that water is classically associated with. The fact that the whole of the Element is characterized this way seems wrong to me, especially since Air and Fire, as described in the novels, fit their traditional associations perfectly. I think this might be due to a misunderstanding.
For example, air is one of the Elements where the novels' description matches its classical description. As a classical element, air is associated with two major properties: "Moistness" and "Warmth" (think breath, not wind). Moistness represents formlessness; the ability to adapt and conform due to lack of strict shape and rigid structure. Warmth is the power of separation, which breaks apart mixed things and causes them to attract others of their kind, so that they become sorted by type (as with an alembic or an
oil distillation tower). When you combine the two, you get that air is the element of formless intangible things, and has the ability to sort them into their component parts...or in other words, air is the element of analysis. Breaking intangible ideas and concepts down to understand them. Hence why Bob is described interchangeably as a spirit of air and a spirit of intellect.
Fire is also described typically in the novels. As a classical element, fire is associated with Warmth and Dryness. Warmth is the power to separate mixed things into their parts as described with air. Warmth is also associated with choice and discrimination, because you separate your choice from other options. Dryness is form, the ability to have structure, inflexibility, identity, and physicality. Combined, fire is the ability to purify something into separate substances, while imposing form and structure on it, as with a smithy or a kitchen. Or in psychological terms, it's will, passion. A choice that is rigid and inflexible. An act of separating what you believe from what you do not, which you cannot be swayed from. A choice which imposes its own form on things. Hence why Dresden, with his implacable will, prefers Fire magic.
Water as a classical element is associated with Coolness, and Moistness. Coolness, associated with love, or aphrodite, is the force which brings different things together, combining them into one. Moistness is the lack of form or identity. Moistness adapts and conforms to circumstance without resistance. Hence you combine the two properties and you get traditionally feminine character traits: empathy and compassion to bring people together; obedience and conformity to adapt to circumstance. You get Water's ability to dissolve things. Water brings things together and combines them with itself. While dissolved, their form is gone, and they become malleable, but they're never destroyed. Eventually they separate and take a new form when spring comes and the Coolness leaves. In this way, water is associated with growth, rebirth, and metamorphosis.
I think that water's ability to dissolve is what Ramirez uses when he uses his Water shield. This is backed up by Jim B.'s comment on the matter:
Ramirez's gauntlet works with entropy-magic (a sub specialty of water magic--all things flowing, constantly changing and shifting, but never gone).
"Constantly changing and shifting, but never gone" are the key words. Water dissolves shape, but never destroys utterly. The substance is still there waiting to be reformed. Hence "entropy" is only one small part of water magic. You might argue that "entropy" in this context is more accurately characterized as half of a transformation. It's an aspect of Water's ability to make things malleable so that their shape can be changed.
I think this suggests a far wider spectrum of uses for Water magic.
TL;DR: "Entropy" as associated with water, has more to do with water's ability to dissolve things and make them malleable, than an inherent association of water with decay.
