25 cfs at Central means the Rio Grande dries before it reaches the Albuquerque wastewater treatment plant.

Alert Inkstain reader Rolf asked in the comments of last weekend’s post for a version of the above graph – number of days of low flow at the Central Avenue Bridge – with a threshold above zero. I usually set the threshold at 25, because our experience in the last two drying episodes – 2022 and 2025 – that’s the point at which the river went dry before it could reach the wastewater treatment plant.

Previous years this dry or drier, with added decadal horizontal bars.

Here’s an updated version of total flow past Otowi to date, with previous years this dry or drier in red, and I added horizontal bars to show decadal averages. As alert reader Devin pointed out, the years after 1972 include imported San Juan-Chama flows. Rio Grande Compact accounting would subtract that out (“Otowi Index Flow”), but I’m interested in the hydrologic reality in the valley, not in using this as an accounting or climate measure. This helps us think about how much water we actually have entering the valley.

Total flow to date at Albuquerque gage.

Here’s the same approach as for Otowi above, but for Albuquerque. As measured by total flow to date, this is also the lowest since 1977.

And since it keeps showing up, here’s 1977. Worth noting (but hard to parse in too much detail because of some missing data) is that El Vado Reservoir began 1977 at near-normal levels, and even though it was a terrible snowpack year they were able to supplement flows by some 100,000 acre feet by draining El Vado between late April and early August of ’77 to supplement the Rio Grande’s flow:

1977: drier spring, wetter summer.