Physico-chemical characteristics of water in water sources undergo changes due to

1. The physico-chemical characteristics of water include parameters like temperature, pH, dissolved oxygen, nutrient concentrations, turbidity, presence of pollutants, etc. 2. Aquatic macrophytes (large aquatic plants) and aquatic fungi can influence these characteristics, for example, through photosynthesis/respiration (affecting oxygen, pH) or decomposition. 3. Evapotranspiration is the loss of water to the atmosphere, which can concentrate dissolved substances but doesn't fundamentally alter the types of chemicals present in the way pollution does. 4. Effluents, which are discharges from industrial processes or sewage treatment plants, often contain a wide range of chemicals, nutrients, pathogens, and heat. These discharges can drastically and rapidly change the physico-chemical characteristics of the receiving water source, often leading to pollution. 5. Therefore, effluents are the most significant factor listed for causing changes in water characteristics.