Assessment of Lower Zab river water quality using both Canadian Water Quality Index Method and NSF Water Quality Index Method

Water is well known as the main constituent of Earth’s streams, lakes, and oceans, and the fl uids of most of earth organisms. It is essential for all known forms of life. During the last decades of the 20th century polluted water has started to become a universal grave issue and surface water quality is becoming a real global concern (Witek & Jarosiewicz, 2009). Human existence, development and well-being have always been linked to water (Eulisse, 2010; Reza & Singh, 2010). Over two thirds of Earth’s surface are covered by water, which represent about 71% of the Earth’s surface, and more than 96% of this water is saline. Over 68% of freshwater is in ice and glaciers and 30% is confi ned in the ground. The rest (about 1.2%) represent the fresh surface-water sources, such as rivers and lakes (Shiklomanov, 1993). Rivers are considered the most important sources of surface water on Earth. They are play a signifi cant role in all human activities, like agriculture, drinking, irrigation, industry, and domestic work. Many industries rely in their processes on water, and about 40% of food supply around the world is grown under irrigation (BCAS, 2000). However, all these activities have posed a major threat to the quality of the river’s water in many countries around the world particularly in developing countries and some drinkScientifi c Review – Engineering and Environmental Sciences (2020), 29 (2), 155–171 Sci. Rev. Eng. Env. Sci. (2020), 29 (2) Przegląd Naukowy – Inżynieria i Kształtowanie Środowiska (2020), 29 (2), 155–171 Prz. Nauk. Inż. Kszt. Środ. (2020), 29 (2) http://iks.pn.sggw.pl DOI 10.22630/PNIKS.2020.29.2.14