1. Natural aging of a lake by nutrient enrichment of its water.
2. Bio magnification, also known as bio amplification or biological magnification, is any concentration of a toxin, such as pesticides, in the tissues of tolerant organisms at successively higher levels in a food chain.
3. The level of ground water is falling day by day due to high demand in urban areas as well as in agriculture. Due to over use of surface water, people rely on ground water for irrigation, drinking, and industrial use.
About 85% of rural water supply and more than 50% of urban and industrial supply is mined. This results in depletion of ground water. Ground water can be replenished by
1. Rain water harvesting
2. Reduction in consumption and waste.