Johnson still swims in the lake sometimes â but nowadays heâs an exception. After the breached canal that created the lake was mended, it was mostly sustained by runoff water from nearby farms - water that was full of pesticides and nitrates, which blended with salt deposits in the lake bed to create an increasingly salty sea. By the 1990s, the sea had started getting even smaller, and saltier, killing off masses of fish and birthing noxious algal blooms. Over the past few decades, tens of thousands of migratory birds around the lake have died of either starvation or poisoning.