Kirk people involved in the disciplines would argue otherwise.... http://en.wikipedia.org/wiki/Hydrography, http://en.wikipedia.org/wiki/Hydrology as one could see from generic content. Being a Geographer, I can assure you that it is quite different than Geology and I would prefer not to open a debate on the similarities, but would not that some Geographers are interested in Post-Modernism and Globalisation whereby I would venture that Geologists are not :)
In soviet/russian geoscience tradition there is a huge difference between these terms.
Hydrology is a
- group of sciences studying the processes that take place in the water bodies on the Earth's surface (land hydrology, hydrochemistry, sedimentology, hydrobiology, river channel science, glaciology, estuarine hydrology, soil hydrology); these are meeting each other in a common subject of study (surface waters);
while Hydrography is considered as a
- description (e.g. size, order, discharge, flow rate, morphometric or regime characteristics etc) of the water bodies that are situated in some region;
- knowlege and technology domain related to the methods of measurements and researches of the water bodies;
In brief, Hydrology studies the hydrological processes at the "low level" while Hydrography descripts the spatiotemporal distribution of the water bodies and its features. However, in the scope of this site there is no urgent need to maintain both tags. From my point of view this is just overkill for the GIS-users.