**2.2 Definite sources pollution**

Industrial and domestic flows result in high concentrations of pollutants that find their way into natural waters, and they are among the primary factors that lead to the deterioration of water quality. As it is known, one of the reasons for the occurrence of nutritional enrichment is the influx of these pollutants containing high concentrations of nutrients estimated at more than (four times) than what is present in natural waters. Therefore, reducing or limiting these sources of pollution is the first successful and important step for water quality management. It is easy to control the known sources of pollution using treatment methods, the most important and most effective of which is the establishment of wet areas (Wetlands) (**Figure 2**).

## **2.3 Non-definite sources pollution**

Sources that cause problems that are difficult to control and unknown sources of pollution prepare more nutrients resulting from the modification that humans make

**Figure 1.** *Fish damage through the spread of toxin-producing algae.*

#### **Figure 2.** *Nutritional enrichment in the waters of the Iraqi marshes.*

in nature such as deforestation, agriculture, industrial and urban development. These sources supply fresh water with low concentrations of nutrients, but it is difficult to control because they are transferred to water bodies from the vast surrounding lands. The preparation of these sources increases in the heavy rainy season, which leads to erosion in the surface of the soil and then filtering of these nutrients from the soil to the aquatic organisms. Man directly and indirectly affects the occurrence of the phenomenon of food enrichment from several aspects, in addition to the industrial, household and agricultural waste it raises. There are many sources of pollutants affecting the Tigris River, including human pollutants, industrial pollutants, agricultural pollutants, and pollutants resulting from groundwater, and thus affected the physical, chemical and biological characteristics, which can be broadly classified into:

