# Reservoir Ruin (DD-718)

> Lake Mead (behind Hoover Dam) and Lake Powell (behind Glen Canyon Dam) are the two largest reservoirs in the United States, and both are fed by the Colorado River. The 1922 Colorado River Compact divided the river's water based on early-20th-century flows that later proved unusually wet. After a long drought, the Bureau of Reclamation declared the first-ever Lower Basin shortage in 2021. The 2007 operating guidelines expired at the end of 2026, and in August 2026 Reclamation adopted a new 2027-2036 framework, though the basin states didn't reach consensus. As of October 16, 2026, gauge data put Mead at about 26% full (1,037.43 ft, a record low) and Powell at about 23% full. Deliveries to the Lower Basin states will be cut by 1.25 million acre-feet in 2027.

- Department: Nature (also Locations)
- First published: 2026-05-22
- Last updated: 2026-05-22
- Permalink: https://detailenjoyer.com/case/reservoir-ruin/
- Author: Marcus Easterling (DetailEnjoyer), The Detail Department

## Status as of Oct. 16, 2026

Lake Mead was at 1,037.43 ft (about 26% full) and Lake Powell at 3,520.02 ft (about 23% full), per Reclamation gauge data compiled by ReservoirBench. New 2027-2028 operating guidelines cut Lower Basin deliveries by 1.25 million acre-feet for 2027.
Out of date in the Reel: The Reel's 'historically low' levels have since fallen further, to new record lows in Sep-Oct 2026.

## On the timeline

- **1922**: Colorado River Compact divides the river
- **1935**: Hoover Dam completed, creating Lake Mead
- **1963**: Glen Canyon Dam completed, creating Lake Powell
- **Aug. 21, 2026**: Reclamation adopts the 2027-2036 Decision Framework
- **Oct. 16, 2026**: Lake Mead at a record low of 1,037.43 ft

Full timeline: https://detailenjoyer.com/timeline/?case=reservoir-ruin

## Quick facts

- **DD-718-F01**: Lake Mead fell to a record low of 1,037.43 ft on October 16, 2026, per Reclamation gauge data. _(Write-up · Exhibit E (Record lows))_
- **DD-718-F02**: The 1922 Colorado River Compact was based on unusually wet years. _(Write-up · Exhibit B (A wet-year deal))_

## Write-up

Lake Mead and Lake Powell and a shrinking Colorado River. Both reservoirs hit new record lows in fall 2026.

1. **Two buckets, one river**: Lake Powell, behind Glen Canyon Dam, stores Upper Basin runoff and releases it through the Grand Canyon to Lake Mead, behind Hoover Dam. Mead then supplies Arizona, Nevada, California and Mexico. They're the two largest U.S. reservoirs by capacity.
2. **A wet-year deal**: The 1922 Colorado River Compact split the river between the Upper and Lower Basins using flows from a period now known to be unusually wet. That's why allocations exceed what the river reliably carries.
3. **New rules**: The 2007 Interim Guidelines and the 2019 Drought Contingency Plans expired at the end of 2026. Reclamation issued a Record of Decision on August 21, 2026, adopting a 2027-2036 Decision Framework after the states failed to reach consensus on long-term operations.
4. **2027 cuts**: Under the 2027-2028 guidelines, Powell began the water year in its lowest 'infrastructure protection' range, aiming to stay at or above 3,510 ft. Deliveries from Mead to the Lower Basin states are cut by 1.25 million acre-feet for 2027.
5. **Record lows**: On October 16, 2026, Mead stood at 1,037.43 ft (about 26% full), its lowest on record in that dataset. Powell was at 3,520.02 ft (about 23% full) after a record low of 3,516.62 ft on September 15, 2026.

## Related case files

- [Water Table Troubles (DD-071)](https://detailenjoyer.com/case/water-table-troubles/): Another case about disappearing water
- [Canadian Wildfires (DD-730)](https://detailenjoyer.com/case/canadian-wildfires/): Another case about drought and heat
- [Carved by Ancient Rivers (DD-210)](https://detailenjoyer.com/case/carved-by-ancient-rivers/): I linked more about rivers and canyons
- [The Glades (DD-619)](https://detailenjoyer.com/case/the-glades/): Another case about US water management
- [Three Gorges (DD-643)](https://detailenjoyer.com/case/three-gorges/): Another giant reservoir behind a dam

## Reel vs. record

- **Current status**: the Reel's 'historically low' has deepened since it was posted. Both reservoirs hit new record lows in September and October 2026, with Mead about 26% full.
- **Missing context**: the old rules expired at the end of 2026. In August 2026, Reclamation adopted a 2027-2036 framework without basin-state consensus and cut 2027 Lower Basin deliveries by 1.25 million acre-feet.
- **Missing context**: the allocation problem dates to the 1922 Colorado River Compact, which divided the river using unusually wet early-20th-century flows.
- **Missing context**: Lake Mead and Lake Powell are the two largest U.S. reservoirs, behind Hoover Dam (1935) and Glen Canyon Dam (1963).
- **Missing context**: Powell is managed to stay above about 3,510 ft to protect Glen Canyon Dam's infrastructure, including its hydropower.

## Video: Reservoir Ruin: Lake Mead and Lake Powell and a Shrinking Colorado River

- Duration: 30.8 s · Published: 2026-05-22
- File: https://detailenjoyer.com/assets/videos/DYqosJytleC.mp4

### Transcript

DID YOU KNOW? Many of America's major water reservoirs have experienced significant depletion due to prolonged drought, overuse, rising temperatures, and growing demand from cities and agriculture. Lakes such as Lake Mead and Lake Powell, which depend on the Colorado River system, have fallen to historically low levels in recent years, exposing submerged land, reducing hydroelectric power generation, and threatening long-term water availability across the Southwest. Climate change has intensified evaporation, and reduced snowpack in the Rocky Mountains, while decades of water allocation agreements assumed wetter conditions than now exist. NOW YOU KNOW!

## Questions & answers

**Q: Which dam holds back Lake Mead?**  
A: Hoover Dam. _(Source: Write-up · Exhibit D (2027 cuts) · U.S. Bureau of Reclamation news release: 2027 operations under the new guidelines (Aug. 2026))_

**Q: In what year was the Colorado River Compact signed?**  
A: 1922. _(Source: Write-up · Exhibit B (A wet-year deal) · Wikipedia: Colorado River Compact)_

**Q: About how full was Lake Mead on October 16, 2026?**  
A: About 26%, a record low. _(Source: Write-up · Exhibit A (Two buckets, one river) · ReservoirBench: Lake Mead vs Lake Powell (daily, from Reclamation gauges; reading of Oct. 16, 2026))_

**Q: How much will 2027 Lower Basin deliveries be cut?**  
A: 1.25 million acre-feet. _(Source: Write-up · Exhibit C (New rules) · U.S. Bureau of Reclamation: Colorado River Post-2026 Operations)_

**Q: What's the largest U.S. reservoir by capacity?**  
A: Lake Mead, with Lake Powell second. _(Source: Write-up · Exhibit D (2027 cuts) · U.S. Bureau of Reclamation news release: 2027 operations under the new guidelines (Aug. 2026))_

## Sources

- [U.S. Bureau of Reclamation: Colorado River Post-2026 Operations](https://www.usbr.gov/ColoradoRiverBasin/post2026/index.html)
- [U.S. Bureau of Reclamation news release: 2027 operations under the new guidelines (Aug. 2026)](https://www.usbr.gov/newsroom/news-release/5392)
- [ReservoirBench: Lake Mead vs Lake Powell (daily, from Reclamation gauges; reading of Oct. 16, 2026)](https://reservoirbench.com/lake-mead-vs-lake-powell/)
- [Wikipedia: Colorado River Compact](https://en.wikipedia.org/wiki/Colorado_River_Compact)

## Cite this case file

Easterling, Marcus. "Reservoir Ruin." The Detail Department (DetailEnjoyer), case file DD-718, last updated May 22, 2026. https://detailenjoyer.com/case/reservoir-ruin/