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Drought watch. Lower Colorado states ok for now, Upper Colorado, not so much

The Colorado River supplies crucial amounts of water to seven states. The water comes primarily from precipitation in the Rockies. However, lower Colorado states (AZ, CA, NV) are in much better shape than upper Colorado states (CO, NM, UT, WY) because they have so much water banked in Lake Mead, Lake Powell, and elsewhere. So, paradoxically perhaps, Colorado farmers may get slammed this year because not enough water will flow down from mountains into their fields while Vegas, Phoenix and Los Angeles may not have cutbacks, at least for a while.

Let’s start with Las Vegas and the other water users of the Lower Colorado River Basin. In addition to Vegas, this includes Phoenix, Tucson, and Los Angeles/San Diego. More importantly (in terms of the volume of water used), it includes the Imperial Irrigation District and a lot of other farmers in the LoCo desert basins. For them, at least for this year, the dwindling snowpack means nothing. With two big upstream reservoirs as buffers, the water allocation rules call for full deliveries this year for all the Lower Basin water users. In the longer term, however, a shortfall upstream moves us closer to the point where Lake Mead drops so low that we could see a shortage declaration in the next few years. At that point, supplies available to Arizona and Nevada are reduced first. (What happens at that point is crazy complicated.)

The Imperial Irrigation District in California, due to water rights dating back to the 1890s, gets 20% of all water from the Colorado. Should a shortage declaration be called, it would be politically impossible for cities in Nevada and Arizona to have forced, mandatory rationing while the IID agriculture continued to get its full share. Some sort of deal would have to be brokered quickly else real live water wars would become a distinct possibility.

The Upper Basin is different. While Lower Basin folks are all in a lather about the possibility of shortages at some point in the future, in the Upper Basin, where you’re getting your water directly from the mountain snowpack, shortage is imposed by nature and happens all the time.

There, you have smaller irrigation districts near the headwaters, farmers pulling directly from depleted streams. You can see what happened to them during comparable bad times during the drought of the early ’00s. In wet years over the last decade, farmers in the state of Colorado used 1.5 million to 1.6 million acre feet. In drought years, they used 1.2maf or less. This is not operating rules imposing shortages because there is not enough water in a reservoir. This is hydrology – if there isn’t water flowing down the river, the field goes dry.

Crazy isn’t it? Not enough water upstream, yet still enough downstream.

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