<p>Hydrology could be a specific major, but generally it is a specialization within geology.</p>
<p>Because of this, you can definitely be a hydrologist with a geology degree. However, it would be better, of course, if you got a degree from a school that would allow you to specialize in hydrology with the degree.</p>
<p>Geology would be a better degree anyway, because if the whole hydrology thing doesn’t work out you can go work in the oilfield industry.</p>
<p>Most hydrologists can be found in geology departments and they (professors) usually hold PhDs from geology/earth science departments. </p>
<p>But sometimes, some hydrologists can also be found in the geography department.</p>
<p>At least in one school, the University of Texas at Austin, they offer specialized geology degrees as in your major isn’t just geology, it’ll be something like general geology, geophysics, hydrogeology & environmental geology, etc. The last being the closest to a full hydrology degree.</p>