Klamath Falls Water Hardness & Quality Report (2026)

Klamath Falls, Oregon, in Klamath County — the Klamath County seat on Upper Klamath Lake in the southern Oregon Cascade Range basin, Oregon's largest lake (by surface area), a geothermal city known for its unique underground hot water district heating system and the Crater Lake gateway corridor — receives its municipal water from the Klamath Falls Water Department (KFWD), which draws from the Upper Klamath Lake surface supply or the Link River (the short channel connecting Upper Klamath Lake to Lake Ewauna and the Klamath River). Upper Klamath Lake is the dominant water supply and ecological feature of the Klamath Basin.

The moderately hard 104 mg/L hardness and TDS of 273.7 mg/L reflect the Upper Klamath Lake watershed's Cascade volcanic plateau and High Lava Plains character. The Klamath Lake basin drains the Cascade Range and the High Lava Plains of southern Oregon — underlain by Miocene Columbia River Basalt Group flows, Pliocene rhyolite and andesite volcanic terrain, and the ancient Klamath Mountains crystalline basement (the Klamath Mountains include some of the most diverse and ancient geology in North America — Precambrian metamorphic and Paleozoic-Mesozoic accreted terrane). The volcanic terrain produces moderately hard water through dissolution of calcium and magnesium from basaltic volcanic rock and the lacustrine chemistry of shallow, productive Upper Klamath Lake.

At 104 mg/L, Klamath Falls' water is moderately hard — scale builds in kettles and appliances over months, the dishwasher benefits from rinse aid, and faucet aerators need periodic cleaning. Quarterly descaling of heating appliances is appropriate. The PFAS level of 2.7 ppt is excellent — among the lowest in the dataset — reflecting Klamath County's rural agricultural character, the remote southern Oregon location far from major military AFFF installations, and the pristine Cascade volcanic watershed's limited industrial PFAS inputs.