A master’s degree is recommended for a research and hydrologist position. A Ph.D. can lead to high level research and academic careers. A hydrologist must also be proficient in statistics, geology, physics, chemistry, and biology. Knowledge of public finance, environmental law, and government policy will also help in effectively communicating the effects of business practices on hydrology.
The American Institute of Hydrology is a nationwide organization that certifies the competence and ethical conduct of hydrology professionals. The AIH site provides information on certification, news and events, as well as education and career options. Such certification requirements vary.
http://water.usgs.gov/edu/hydrology.html
http://www.aihydrology.org/