Ключевые слова: artificial, bulgaria, canal, concrete, control, dirty, drain, drainage, environment, environmental, fall, flood, floodwater, flow, flowing, forest, garden, industrial, liquid, nature, outdoors, outfall, overflowing, pipe, pollution, rain, rainwater, river, sanitary, sea, sewage, sewer, sewerage, stagnant, storm, stream, summer, system, urban, water, waterfall, wet,