The Pajaro Valley Water Management Agency covers southern Santa Cruz County.

The Pajaro Valley’s unusual system — essentially a tax on water — was born of a berry-growing disaster some 40 years ago that forced farmers to act. Today, as the nation faces a spreading crisis of dwindling groundwater, stemming from a combination of climate change, agricultural overpumping and other issues, some experts say the Pajaro Valley is a case study in how to save the vital resource.