State regulators launched Thursday into a year of pivotal decisions on Gov. Jerry Brown’s quest to build two giant tunnels to ferry water from Northern California for Central and Southern California, a $17-billion project that would be one of the largest in decades in the state.

Brown’s administration and the water agencies are slated — but not yet formally committed — to pay for the two, 35-mile-long tunnels from the delta of the Sacramento and San Joaquin rivers, and the 2016 calendar is full of federal and state hearings and reviews that are required to start digging.