The proposed dam site lies at river mile 274 on the San Joaquin, west of the small community of Auberry in the Sierra Nevada foothills. The Bureau of Reclamation originally evaluated three potential locations along the river - at river miles 274, 279, and 286 - before narrowing the field to the lowest site. The choice was not simple. The RM 274 and RM 279 sites sit in the upper reaches of Millerton Lake, Friant Dam's existing reservoir, meaning a new dam there would partly replace existing storage rather than adding fresh capacity. At RM 274, Temperance Flat would actually reduce Millerton Lake's capacity by 75,000 acre-feet - a volume greater than what 150 of California's current reservoirs hold. The Bureau presented four alternatives for the specifics, but each one involved flooding scenic river canyons and inundating existing hydroelectric powerhouses that would need to be replaced.

The environmental stakes extend well beyond scenery. Local Native American tribes have identified thirty sensitive sites within the Temperance Flat study area, one of which the Native American Heritage Commission designated as sacred. The proposed reservoir footprint is home to bald eagles, several special-status bat species, ringtails, American badgers, and San Joaquin pocket mice. Western pond turtles, a California Species of Special Concern, occur regularly at multiple sites along the proposed flooded corridor. The federally listed California tiger salamander has designated critical habitat nearby. Even the project's potential benefit to fish is uncertain: the Bureau's own models estimate that spring-run chinook salmon abundance would increase by only 0.65 to 2.7 percent on average, and a full quarter of the modeled scenarios actually decreased long-term salmon populations. For a dam billed as a solution to California's water crisis, the ecological math cuts sharply in the other direction.

In February 2014, Representative Jim Costa introduced legislation to authorize construction. The Bureau released a draft environmental impact statement that September. Voters passed a $7.5 billion water bond in November 2014, earmarking roughly $1.25 billion for Temperance Flat as one of three major storage projects. The money was real, the political will appeared genuine, and for a moment the dam seemed inevitable. Then the accountants got involved. The Bureau's cost estimate of $2.5 to $2.6 billion was the optimistic version; other analyses pushed the figure past $3.3 billion. Environmental groups like Friends of the River called the project "an expensive and ineffective solution to the state's water needs." By July 2020, a cost-benefit analysis showed the numbers simply didn't work for the water users who would ultimately foot the bill. Construction was shelved indefinitely - not killed, but placed in the particular limbo that California reserves for infrastructure projects too costly to build and too politically useful to officially cancel.

Temperance Flat sits in a broader context that makes the debate personal for millions of Californians. The San Joaquin Valley is one of the most productive agricultural regions on Earth, and its farms depend on managed water storage. Friant Dam, completed in 1942, already transformed the river from a free-flowing waterway into a controlled resource - and Temperance Flat would extend that transformation deeper into the Sierra foothills. The tension between storing more water for farms and cities, preserving free-flowing rivers and their ecosystems, and respecting indigenous heritage sites has no clean resolution. California's population continues to grow, its droughts grow more severe under climate change, and its rivers continue to host species that have survived for millennia by relying on the seasonal flood patterns that dams erase. Temperance Flat may yet be built, or it may join the archive of dams that existed only on paper. Either outcome will say something about what California values more: the water in the canyon, or the canyon itself.