Ключевые слова: background, canal, chemical, clean, concrete, conduit, construction, contrast, corrosion, dam, danger, dirty, drainage, dump, earth, ecology, environment, environmentalist, factory, flowing, fluid, garbage, industrial, industry, irrigation, liquid, mud, natural, nature, old, park, pipe, pipeline, pollution, pump, refinery, river, rock, sewage, sewer, stream, toxic, treatment, tube, urban, waste, water, waterfall,