For several years in the mid-1970s, Carlos worked as a consulting hydrologist in Arizona and New Mexico. He established monitoring groundwater and surface water programs for municipalities, mines and agricultural entities—in fact, he was among the first to outline monitoring strategies for complying with the Surface Mining Control and Reclamation Act of 1977 for a large strip mine in northern New Mexico.

Carlos also worked on stream adjudications in New Mexico and consulted for parties involved in disputes over the withdrawal of groundwater in both Arizona and New Mexico. Those disputes often involved computer modeling of groundwater flow conditions, measurement of stream flows and water quality, and analysis of long-term aquifer productivity.

In 1978, Carlos was a year away from becoming a registered civil engineer when he decided to go to law school at the University of Arizona.

Over the past 30 years that he has practiced law, Carlos often has relied on his hydrology experience when resolving disputes over the diversion, withdrawal or use of surface water or groundwater.