Math needed for Hydrology, specifically surface water hydrology I wanted to know what math is needed for hydrology, in particular surface water hydrology.

In my research online, of Master's programs (either in Hydrology or Environmental Science with a concentration in Hydrology), the undergraduate math pre-requisites differ greatly from program to program: some just required a year of calculus, others wanted or strongly recommended Calculus I, II, and III and yet other programs it was Calculus I, II, III, Linear Algebra, and Differential equations. 

Does anyone have any suggestions or thoughts about how much math?!
Math is very important for hydrology. Especially for surface water problems, you require understanding of differential equations while open-water hydraulics like backwater calculations are complex. If you need a great deal of detail, these problems cannot be solved analytical, only numerical. 

So I recommend a good mathematical basis to study surface water hydrology and hydraulics.