Surveyors will plunge poles into the Sierra Nevada snowpack near Lake Tahoe on Tuesday, taking the season’s first measurement by hand of the snow’s water content as California flirts with a sixth year of drought. What they find in the snowpack between now and April 1 will guide state water managers in the nation’s most populous state that also leads in production of farming. Electronic monitors in late December showed the snowpack’s water content at just 72 percent of normal despite heavy rain. That figure dipped even lower during the holiday weekend.