The scientists studied the water quality of Khirisan River in Iraq by analyzing different parameters like physical, chemical, and biological factors. They collected samples from areas with agriculture, businesses, and homes to see if the water was safe for drinking and irrigation. They found that the river's quality was mostly good for drinking, but had issues with calcium ions, hardness, and organic matter during rainy months. The water was okay for irrigation, but had some problems with salinity and sodium levels. The researchers recommend ongoing monitoring to improve the river's quality.