Since 2007, California, Arizona, Nevada, and Mexico have voluntarily reduced their legally entitled Colorado River water use by 4.4 million acre-feet, with 3.6 million acre-feet of conserved water presently remaining in Lake Mead. These efforts kept Lake Mead storage above critical elevations through the recent 20-year (and ongoing) dry period. The voluntary water conservation program operates on the assumption that annual physically available water (reservoir inflow minus evaporation) exceeds total legal entitlements of 9.0 million acre-feet per year. This assumption is challenged as the Colorado River Basin becomes more arid. Additionally, as reservoir storage declines towards catastrophic elevations, users face difficulty accessing and withdrawing their conserved water. We suggest two novel improvements that tie accounting of reductions to the annual physically available water, rather than historical entitlements: 1) Proportionally reduce credits for conserved water, and 2) Create a new protection account to be managed by the U.S. Bureau of USBR (USBR), with separate water accounts for each user. Through these structures, the USBR takes a first share of the physically available water that is equal to reservoir evaporation to sustain the protected volume. Then, water users divide the remaining inflow and consume, conserve, and/or trade within their account balances. Both suggestions have potential benefits to stabilize and recover Lake Mead storage while giving users more adaptability and autonomy to manage their differing and, sometimes, conflicting risks of declining flows. These strategies can serve as examples for other water systems that face aridity, declining reservoir storage, and user conflicts.

Contents:
README.md - Main readme file. Contains explanations of and directions to use the contents.
LakeMeadWaterConservationProgramSuccessChallengesSuggestions_v4.docx - Microsoft Word file with the manuscript.
Python-Fig6to7 - Python code to generate Figures 6 and 7 in the manuscript.
R-Fig1to5 - R code to generate Figures 1 to 5 in the manuscript.