When people asked me how long I’ve lived here, it’s an easy answer. My benchmark is the flood of 1997. I moved here in fall of 1996, ready for the ski season and -unbeknownst to me- just in time for the 1997 flood.
Let’s back up. That year, there was much anticipation for El Niño, the weather pattern that is often associated with much snow. (Anyway that’s what I recall from working in the ski industry at that time.) By late December 1996, winter storms had delivered a lot of snowpack – more than 180% of normal. Great, right? Not if it rains on top of all that snow. In that case, it can be a massive melt and flood event.
In early January 1997, a “Pineapple Express” brought three days’ worth of rain to the area. Having nothing to do with the fruit, a Pineapple Express is an example of an atmospheric river event. During these events, winds cross over bands of warm tropical water vapor to form a “river,” which then travels across the Pacific from the tropics to northern latitudes like in our area. Pineapple Express events usually bring warm temperatures. The 1997 event was so warm that 20% of the high altitude snowpack melted (above 10,000 feet). Below 7,000 feet, 80% of the snowpack melted. Much of this melted into the Truckee River and headed for low-lying areas around Reno and Sparks. If you google “1997 flood Reno,” you’ll come across many unbelievable images like the one below.
The last blog discussed the USGS streamflow gauge in downtown Reno, current year’s flow, and median versus average flow. Some of the highest flow measurements ever recorded at the downtown gauge took place during the flood of 1997. There’s more info from the USGS here.
The chart below shows measurements taken between December 1996 and April 1997. Notice the peak in early January just below 20,000 cubic feet per second (cfs), which resembles average flow rates for rivers like the Connecticut and Allegheny (Ohio). By comparison, the Truckee River flows about 800 cfs. Including the extremely high values from the 1997 flood event to calculate an average on the Truckee would not give an accurate representation of “average” conditions. Those are better shown by the median, which is the dotted black line.
The Pineapple Express was not an isolated event in 1997. They happened before, since then, and will happen in the future. The most recent occurred in our area in 2017 and brought record snowpack to the Sierra. Our ability to forecast these events has greatly improved and, with that, the ability to manage the movement of water to and from reservoirs to lessen and even eliminate the probability of flood damage.
The National Oceanic and Atmospheric Administration (NOAA) has more information and a really neat animation on the Pineapple Express. Check it out here. And check back for updates on Truckee River flow rates in the coming weeks.