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Comment by jeffbee | Hacker News Reader

Flooding rice fields in Glenn County is essentially 100% efficient because all of the water returns to the Sacramento River or recharges aquifers. Watering orchards in west Fresno County returns all of the water to the atmosphere via transpiration. Even though superficially a rice field looks wasteful, they are on two opposite extremes.

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Doesn't a large percentage of the water flooding a rice field in Glenn County still evaporate, both before it enters the plants/aquifer, and later through transpiration?

I don't know the percentages (but would love to learn) but it's certainly not zero.

Sure, but the denominator for flooded irrigation is huge, so the efficiency is high. That's why flooding is a superficial and not substantial problem. The plant transpires water at a certain rate and a certain density per ground area. That rate isn't influenced by whether the field is flooded or drip-irrigated. By the way flooding also provides wildlife habitat.

Anyway I'm just tired of the meme about growing rice in a desert. California rice country isn't a desert, it exists in places that were annually flooded before flood control engineering, and should still get flooded for various reasons. It is not a waste of water.

Returning to the atmosphere is not really sustainable, is it? Sure, it enables a rainfall at some point, but not necessarily at the time and the place you need it next year.

No, it is not sustainable at all. They are pumping out fossil water in California and whatever portion of it falls as rain does so hundreds or thousands of miles to the east.

How does returning it to the river solve the problem of their isn't enough groundwater? That water goes back into the ocean where it's stuck if it never rains.

Yeah but that's not really what happens to Sacramento River water. It's all diverted downstream for other uses. The Tracy pumps that raise the water from the delta into the aqueduct are the largest energy consumer in the state.

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