The control
July stays almost flat
Peak-tourism July influent stayed inside 1.73–1.96 MGD across nine summers (mean 1.851 MGD, CV 4.7%). If spring spikes were mostly people, July should move. It does not.
Working paper · September 2026 · Big Bear, California
Smart as Shit
Finding Data in Unexpected Places
Poster PDF · tap to openResearch poster. Same argument as the paper, compressed for a cold LinkedIn read.
In spring the sewer was not counting tourists. It was counting the thaw. In July it was counting people.
The weather year
March tracks winter water
March influent ranged from 1.87 MGD in dry 2018 to 5.13 MGD in 2023. October–March precipitation versus March flow: Pearson r = 0.94 (n = 9). The relationship survives removing 2019 or 2023.
The system check
The spike is network-wide
Member shares stayed broadly stable in the monster years: about 53–62% Big Bear Lake, 35–44% CSD, 3–5% Fawnskin. That is a hydraulic story, not a single tourism corridor.
The rule
A proxy has operating conditions
Wastewater can estimate transient population only after hydrologic infiltration and inflow are separated from sanitary load. The sensor is not broken. The measurement model is incomplete.
Abstract
Tourism-dependent communities often need population estimates at timescales that census counts cannot provide. This case study reconstructs an applied measurement approach developed in Big Bear, California, where conventional visitor-counting methods were unreliable. Wastewater influent was treated as an unavoidable physical trace of human presence, then tested against weather to determine when flow represented people and when it represented hydrology.
Monthly Big Bear Area Regional Wastewater Agency influent from January 2018 through August 2026 was merged with NOAA GHCN-Daily observations for Big Bear Lake. July remained a comparatively stable sanitary/tourism control. March did not. The central result is methodological: wastewater can function as a population proxy only when the mechanisms that also move wastewater are explicitly modeled.
This is a working paper, not a peer-reviewed journal article. The shoulder-season tourism-marketing question is left open on purpose: the data support a hypothesis, not a causal claim. Full methods, robustness checks, limitations, and references are in the PDF.