The Dominguez Channel was built to drain an extensive swampland, originally known as “[the N-word] Slough” (now renamed *Lagunas de los Dominguez"), which was formed when Compton Creek and the LA River would overflow in wet years.
The Slough was a popular duck-hunting ground, but as far back as 1894 it was being denounced as a stinky public health nuisance in a lawsuit reported in the pages of the Los Angeles Herald:
…it is set forth that the lake and its tributaries, known as “Ni**er” slough, is a nuisance and a menace to the health and happiness of the public. It recites at length that there has never been any outlet to the so-called lake or slough.
That for a long time there has been an accumulation of stagnant water, foul-smelling and unhealthful.
That continuously and for a long time dead and decaying fish and decayed vegetable matter has polluted the lake and its tributaries.
That the atmosphere is so foul as to become injurious to the health and offensive to the senses of the entire surrounding neighborhood and the community thereabouts.
That for these and many other reasons the slough ia a public nuisance.
Eventually, the channel was constructed, the swamp drained, and a massive petroleum refinery and storage facility built.
But, yeah, its only water source these days is local runoff, and there hasn’t been much of that lately. 
