In parched southern Texas, a yearslong drought has depleted Corpus Christi’s water reserves so gravely that the city is scrambling to prevent a shortage that could force painful cutbacks for residents and hobble the refineries and petrochemical plants in a major energy port. Experts said the city didn’t expect such a bad drought, and new sources of reliable water didn’t arrive as expected. Those problems arose as the city increased its water sales to big industrial customers. “We just have not