With little water storage to speak of in the Imperial Valley, the flow of the All-American Canal west from Imperial Dam integrates, in close to real time, the collective decisions of a thousand farmers growing crops on half a million acres.

A “hydrograph” is a commonly used tool for looking at the flow of water past a measurement gauge over time. You put time on the “x” axis and flow on the “y” axis, to help visualize its ups and downs. There aren’t many natural hydrographs left to look at in the western United States, but I’m fascinated with human-intermediated ones.

I’ve written before about the “institutional hydrograph” on my Rio Grande, where we have an annual bump in flow as water is moved to meet end-of-year compact delivery obligations. On the All-American Canal, you can see – what – an “agronomic hydrograph”?

I spent my holiday afternoon cleaning up some data visualization code I use to help me think about USGS gauge data. (On github here.) One of the gauges I tried it out on was the flow down the All-American Canal from Imperial Dam. The double peak is fascinating – heaviest water use in April, then a drop, then another peak in late July and early August.

It’s an agronomic hydrograph, driven in part by cropping patterns (the Imperial Irrigation District publishes wonderful data here summing up the collective behavior of the valley’s farmers) and partly the weather. August, I’m told, is really hot down there.