The Underground River Runs Out
Deep-well turbine pumps let the valley drink from its confined aquifers, drew the water table below sea level, and let the Pacific creep inland. The episode credits the engineers: two dams to soak the riverbed, recycled water for coastal fields, and an inflatable dam near Marina. It separates Pure Water Monterey, which feeds a different basin, from the valley's own aquifers, then weighs the ledger. The salt front sits roughly seven miles inland.
Where it happens
- Salinas Valley, California+7 more episodesValley whose confined aquifers are intruded by seawater
- Nacimiento Dam, California1957 reservoir releasing summer water to soak the riverbed
- San Antonio Dam, CaliforniaMid-1960s reservoir serving the same recharge purpose
- Castroville, California+2 more episodesCoastal acres irrigated with recycled water since 1998
- Seaside Groundwater Basin, CaliforniaSeparate basin receiving Pure Water Monterey injection
- Pajaro, California+1 more episodeLevee failed on 10-March 11, 2023
Timeline
- 1930sSeawater intrusion into the coastal aquifers is first observed.
- 1946The state publishes Bulletin 52, documenting the intrusion and proposing remedies.
- 1957Nacimiento Dam is completed; San Antonio Dam follows in 1965-67.
- April 1998The Castroville Seawater Intrusion Project begins delivering recycled water to fields.
- 2014California's Sustainable Groundwater Management Act makes critical overdraft a legal status.
- March 2023The Pajaro levee fails near the river mouth.
Still debated
Intrusion was observed in the 1930s but formally published in 1946, and both dates are correct. Estimates of how far inland the salt front sits range from over five to about eight miles, and overdraft figures vary by area and period. Critics dispute whether the local plan's targets and timelines are adequate.
