Those alarmed by global warming call it “the other water problem” – not rising sea level, but diminishing snowfall over the western United States. Climate models indicate that snowfall levels could drop as much as 70% by the end of the 21^st century – a prediction that, if true, would require a seismic shift in the way the United States uses water for agriculture and human consumption.

Before you start drilling a 600’ well and building a million-gallon cistern, it should be noted that the climate models we’re talking about have, to put it politely, a sub-optimal record in their predictive accuracy. But even if the models are completely wrong and snowfall levels remain where they are, the west, and agriculture in general, still faces a long-term water problem. Doom mongers have, in recent decades, focused on oil, with “peak oil” being just the latest in a long series of imminent disasters that never seem to pan out. The reason for the failures of all those predictions is simple: oil is not a unique commodity. It can be conserved, it can be used in different ways, and it has any number of substitutes. If all the oil in the world disappeared tonight, there would be a huge economic dislocation – but it wouldn’t be a dislocation caused by there being no more fuel energy for humans to tap, it would be a dislocation caused by us having to undergo a massive shift to alternative sources like ethanol, coal, nuclear, and other renewable energy sources overnight.

Water is different. The quantity of water on our planet – 326 million trillion gallons – is stupendously large, but it is a fixed quantity. That’s all there is – and like land, they aren’t making any more of it. Only about 2% of the total global supply is fresh water – suitable for drinking or for use in the plant growth cycle. What’s more to the point (after all, oil is also a fixed quantity), there is no substitute for water. We can conserve, but humans have to drink water to survive, and the same goes for our livestock. You cannot irrigate a cornfield with anything other than fresh water. Renewable energy systems like solar or wind essentially convert wasted outside input to the planet’s energy system, in the form of sunlight and the heat which drives our wind cycle, and turn it into a replacement for oil – but there is no equivalent for water. What there is, is what we have – and there’s nothing else we can use instead.

Hardly anyone has worried about this in the past, because the quantity of water on the planet has been so enormous in proportion to the human population that water shortages were always a local problem caused by geography, weather, or politics. Six billion human beings later, that’s no longer the case. Water use is going to become one of the central issues that the agriculture industry has to deal with in the future. I’ll be writing further about this in the days to come, talking about how the systems we have for allocating water now are likely to change, and what that is going to mean for farmers and ranchers.