River runoff risks, bacteria ratings, and DOH advisories
📍 Hanalei, Kauaʻi — North Shore
Hanalei Bay has moderate bacteria risk driven primarily by the Hanalei River. After dry spells, the water can be stunning and low-risk. But Kauaʻi's North Shore receives over 450 inches of rain annually in the mountains above the valley — making brown water events frequent.
The river drains taro fields, wetlands, and steep mountain terrain. Agricultural runoff contributes elevated enterococci and sediment. DOH issues brown water advisories for Hanalei Bay more frequently than most Kauaʻi beaches.
Based on: DOH monitoring history, Hanalei River discharge frequency, North Shore rainfall patterns, agricultural runoff
The 72-hour post-rain rule is especially critical at Hanalei Bay. Hanalei Valley receives extraordinary rainfall that can cause the river to surge and turn the entire bay brown for 1-3 days. Even light North Shore showers can impact the bay. On days when you can see mountain waterfalls in the valley, assume the river is running high.
The far east end near the Hanalei Pavilion is furthest from the river mouth and recovers fastest after rain. Best choice for families.
The west end past Pine Trees also tends to have better water quality than the center of the bay near the pier.
The pier area near the river mouth is highest risk. Brown water from the river collects here first and lingers longest. Stay away for 72+ hours after any significant rain.
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⚠️ Important Disclaimer
Safe to Swim Hawaii is an independent project not affiliated with the Hawaii DOH. Ratings are estimates — not real-time measurements.
Verify with the Hawaii DOH Clean Water Branch before swimming.
When in doubt, don't go out. 🤙