Ключевые слова: background, bad, canal, cement, clean, clear, concrete, day, dirty, drain, drainage, duct, dump, ecology, environment, environmental, flood, flow, flowing, gutter, industrial, industry, nature, outdoor, outlet, outside, pipe, pipeline, piping, pollute, pollution, pond, pouring, purified, rain, rainwater, river, round, runoff, sewage, sewer, sewerage, smell, stream, system, tube, tubing, waste, wastewater, water,