水循环不是地质学,但土壤学是很重要的,这是一个地球科学。江南体育网页版Ag)水可以(通过_photosynthesis_)直接转换成简单的碳水化合物,我们吃;或转化为碳水化合物,然后用作结构或能量,使有机体生存和增长,但质量不是我们最后吃;或者用于构建更复杂的部分生物(脂肪、蛋白质),我们终于吃;或失去了大气层(大部分),因为这些生物过程都不漏;或失去了大气层或地下水,因为我们不让所有的水植物的根系什么时候可以使用它。如果我们吃肉,所有的损失使植物动物吃,然后在把植物变成动物,效率低下,能源成本的结构和动物生存和增长。列出的作物并不是简单碳水化合物,甚至自我加肥豆类。它需要很多的树杏仁或鳄梨。需要大量的水来种植的紫花苜蓿和谷物喂养奶牛。 There's also water in the processing, the cold chain, often in generating the power that makes N fertilizer or moves food from CA to the markets. CA's main ag land is dry and warm and often windy in the summer, so it can lose water really quickly (either through the plants or from flood or overhead irrigation, and even a little bit through mulched soil). I don't know about all of CA (it's a big place with a lot of different climates), but at least some -- the west side of the Central Valley -- is having soil trouble because they rarely get enough irrigation or rain to flush salts and excess fertilizer out of the root zone, so they at least aren't sending excess water to groundwater. One could check stream gauges to guess whether excess water is making it into *surface* water -- my guess, not.