Ключевые слова: background, beautiful, blue, canal, clean, country, countryside, dirty, ecology, environment, environmental protection, environmentally friendly, field, flow, forest, freshness, grass, green, industry, landscape, lawn, liquid, meadow, natural, nature, outdoor, park, plant, pollution, purification, recycling, reflection, river, road, scenic, sky, spring, storage, summer, system, tank, technology, top view, travel, tree, water, water purification, water storage, water treatment,