I agree with Maria and Hasan. ...

I agree with Maria and Hasan. It also depends on what kind of hydrogeological units you're working in. Is this karst? alluvial? volcanic?glacial? In each case you might have to consider different tests as well as different protocols for collection. In addition, are you testing water quality or groundwater-surface water interaction? I think it is wise to check with the local laboratories as someone else mentioned. I'm afraid I made plenty of mistakes not doing all these things first and ending up with a lot of information that was not as useful as I'd hoped. Best of luck!