How to Read Reclamation's 24-Month Study — Lake Mead and Lake Powell Levels, Projections and Two October Release Scenarios

As of 13 November 2026, 00:58 KST (retrieved by this page at that time); latest listed on the agency page at retrieval: the October 2026 Most Probable 24-Month Study of the Bureau of Reclamation, posted in two versions on the Lower Colorado river operations page, one for a 6 maf and one for a 7 maf Lake Powell release in water year 2027 (22 pages each, dated October 15, 2026). Values for October 2026 onward are projections. Monthly studies between July and October 2026 exist (the October study cites the August 2026 24-Month Study) but were not compared here; the table below compares with the July 2026 study. Primary source: https://www.usbr.gov/lc/region/g4000/24mo_6.pdf^[1][2][4]

Comparison basis: elevations are end-of-month feet as printed to two decimals; volumes are thousand acre-feet (1000 Ac-Ft) as printed. Differences subtract displayed values and are not rounded further. The tables do not mark which rows are observed and which are projected; the October study was processed on 10/8/2026, and its rows through September 2026 are identical in the two scenarios. The July study's values for July to September 2026 were projections when it was processed on 7/7/2026.^[1][3]

In three lines

1. Lake Mead stood at 1037.80 feet at the end of September 2026 in the October study, 19.45 feet below September 2025.
2. Among the October 2026-September 2027 month-end projections, Lake Mead's lowest is 1007.73 feet (July 2027) in the 6 maf scenario and 1015.68 feet (May 2027) in the 7 maf scenario.
3. These are two October Most Probable release scenarios, each labelled official; the WY 2027 Powell release is expected between 6.00 and 7.00 maf but may fall outside that range after consultation.^[1][2]

A monthly operating projection. Each study tabulates inflow, releases, elevation and storage for each reservoir month by month over about two years, under Most Probable inflow. The study notes: "The operating year is defined as October 1st to September 30th for Lake Powell and January 1st to December 31st for Lake Mead."^[1][3]

Rules for 2027. The October study says Lake Powell's WY 2027 release is expected in the range between 6.00 and 7.00 maf under the 2027-2028 Operating Guidelines, and: "In accordance with the 2027-2028 Operating Guidelines, a shortage condition consistent with Section 5.3.A will govern the operation of Lake Mead for calendar year (CY) 2027." It adds: "The 2027 operational determinations for Lake Powell and Lake Mead will be documented in the 2027 Annual Operating Plan (AOP) which is currently in development."^[1]

Inflow behind the numbers. The July study said: "The WY 2026 unregulated inflow forecast for Lake Powell is 3.50 maf or 36% of average." The October study reports: "The preliminary observed WY 2026 unregulated inflow for Lake Powell is 3.72 maf or 39% of average." It also says: "The October 2026 Most Probable 24-Month Study reflects a 1.00 maf Drought Response Operations release."^[1][3]

Two official studies for October. The 6 maf version says the following official October 24-Month Study projects a 6.00 maf release, and the 7 maf version says the same with 7.00 maf. The documents do not say which release will be adopted, so the operative scenario is not established; readers should quote both.^[1][2]

Which study is current. The 24-Month Study archive page says the current month's study can be found here; at retrieval that entry opened the July 2026 study (dated July 15, 2026), while the river operations page lists the October scenarios as 24-Month Study Current (updated monthly). This page treats the October studies as the latest listed. Earlier monthly studies are offered only through a selector on the archive page, which this page did not use, so the August and September 2026 studies were not compared.^[4][5]

Total release against power release. In the 6 maf study, Lake Mead's total release equals Hoover's power release in every month of WY 2027 except April to July 2027; for April 2027 the first table shows 990 thousand acre-feet total and the power table 674, so the difference between the two columns is 316 (this page's subtraction); the study does not specify its components.^[1]

Past months differ between editions. For May and June 2026 Lake Mead's SNWP use reads 20 and 25 in the July study and 19 and 24 in the October study. The studies do not say why, and this page does not assume either is final.^[1][3]

July's projection against October's table. The July study projected Lake Mead at 1037.17 feet and Lake Powell at 3516.16 feet for the end of September 2026; the October study shows 1037.80 and 3518.08. The July study also projected Lake Powell at 3491.75 feet in April 2027, below the October scenarios' low of 3516.28 feet; the projections rest on different inflow forecasts and assumptions, so the gaps are not forecast errors measured against observations.^[1][3]

Dates kept apart. October studies: dated October 15, 2026, processed on 10/8/2026 (12:58:35 PM for 6 maf, 11:38:46 AM for 7 maf). July study: dated July 15, 2026, processed on 7/7/2026. Data rows: October 2025 to September 2028 in the October studies.^[1][2][3]

Next release. The river operations page describes the studies as updated monthly, but no date for the November 2026 study is given, so the next release date is not established.^[4][5]