Victor Davis Hanson is a contributing editor of City Journal. He is the author of the forthcoming novel "The End of Sparta." Adapted from the summer issue of City Journal.

California's water wars aren't about scarcity. Even with 37 million people and the nation's most irrigation-intensive agriculture, the state usually has enough water for both people and crops, thanks to the brilliant hydrological engineering of past Californians. But now there is a new element in the century-old water calculus: a demand that the state's inland waters flow as pristinely as they supposedly did before the age of dams, reservoirs and canals. Only that way can California's rivers, descending from their mountain origins, reach the Sacramento-San Joaquin River Delta year-round. Only that way, environmentalists say, can a 3-inch delta fish be saved and salmon runs from the Pacific to the interior restored.

Such green dreams are not new to California politics. But their consequences, in this case, have been particularly dire: rich farmland idled, workers laid off and massive tax revenues forfeited.

You can learn an important fact about the water wars simply by driving the width of California's vast Central Valley, home to a large chunk of the state's $14-billion farm export business. What the drive teaches you is that there is no single Central Valley agriculture. Rather, the state is divided longitudinally, right down its middle, into two farming landscapes. These regions — the east and west sides of the Central Valley — differ not only in the crops they grow but also in the availability of water....