Reservoirs in the Southwest are full and mountains are deep with snow, but businessmen and water supply officials have begun to see their water bonanza as a political curse that may put vital conservation and aqueduct projects years behind schedule.

"Recent weather conditions are going to aggravate the problem because nobody is going to worry about it," said C. John Ekman, senior vice president at Security-Pacific National Bank. "If a time bomb is ticking, and you wait before you move, it's just going to get worse."

In California, water officials in the southern part of the state still have not found a way to guarantee additional water supplies from the north when Colorado River water is diverted to Arizona by federal court order after 1985.

Even with its new Colorado River supplies, Arizona is expected to continue to drain off its own shrinking supply of ground water unless it persuades its citizens to comply with a stringent new conservation plan.

Arizona is using up its ground water at a rate of 2.5 million acre-feet a year. A family of five uses about one acre-foot of water--325,851.42 gallons--each year for all its needs, including growing its foods and cooling the machines that make the family cars.

Southern California officials note that even after a relatively dry winter last year they lost a bitter fight to pass a state ballot measure ensuring future water supplies from the north by the construction of a "peripheral canal" around the Sacramento River delta.

Jay Malinowski, spokesman for the Metropolitan Water District of Southern California, said the political climate may only get worse. "People are a little bit short-sighted," he said. "They see this kind of rain and say, 'Gee, no problem, we've got all the rain that we need.' "

Los Angeles alone has received more than 31 inches of rain so far this season, compared with about 11 inches up to this point last year and an average for the period of about 15 inches.