File:Water Release from Arizona Reservoirs (MODIS).jpg

English: Since December 2022, a series of moisture-laden winter storms have drenched the West Coast of the United States. In the state of Arizona, rain storms soaked low elevations while record-breaking snowfall buried the high country. From July 1, 2022, through March 1, 2023, the Flagstaff Pulliam Airport received just over 140 inches of snow, the second-highest total recorded between July 1 to March 1 since data collection began 101 years ago. At the same time, the weather service office in Bellemont reported 146.7 inches, smashing their previous record, which was 115.4 inches in 2009-1010.

Before the February and March storms struck, the National Weather Service had reported that, as of mid-January 2023, the snow water equivalent (SWE) in northern Arizona was already as much as 250 percent of normal. During spring melt, snowpack in the high elevations release water that is essential to moisten wildlands, agricultural lands, and for human use, so the high snowpack was good news. However, the ferocious winter rains had already helped fill reservoirs, including the large Theodore Roosevelt Lake along the Salt River and the Granite Reef and Bartlett Dams along the Verde.

Too much of a good thing is, well, something that has to be carefully managed.

Throughout the year, the Salt River Project (SRP) releases water from the dams on the Salt and Verde rivers into a series of canals to meet the water needs of the Valley below. In particularly wet winters when the reservoirs are nearing capacity, some releases outside of the canal system are required to make room for additional expected runoff. This year, for the first year since 2019, the “productive” storms and the subsequent runoff had filled the reservoirs to near capacity by early March, prompting water managers to release water from the dams. The managed release has allowed substantial water flow in the Salt River, and has caused flooding and road closures in some areas.

The Moderate Resolution Imaging Spectroradiometer (MODIS) on board NASA’s Terra satellite acquired two false-color images of rising waters along the Salt River below the Theodore Roosevelt Dam on two different days. The first is on March 1, 2023, prior to releases from the dam, but after a wet winter. The second was captured on March 27, 2023, when the river was full and in flood, especially below the Phoenix metro area. To allow a better comparison of the changes in the landscape, the images fade into each other, with the dates acquired showing in the upper left corner.

In this type of false-color image, vegetation appears bright green, water looks blue, snow appears electric blue, and open land is tan. Manmade structures, such as the cities in the Phoenix metro area, are tinted gray. Theodore Roosevelt Lake stretches from northwest to southeast in the right (east) section of the image, and the Salt River flows toward the southwest. Prior to release, the Salt River below Phoenix (lower left corner of the image) was tan and dry, but appears flooded by March 27.