Assessing surface water uses by water quality index: application of Qalyubia Governorate, Southeast Nile Delta, Egypt

In this study, water quality index (WQI) was applied at one of the most crowded Nile reaches surroundings in Egypt to investigate its impacts on different water uses. Twelve sites are selected for monitoring (S1–S12) within the irrigation system network of the Qalyubia Governorate, and water samples from these locations in 2021 were collected, analyzed, assessed, and compared to analyze water quality data collected in 2014 in light of the Egyptian permissible water quality limits regarding the drinking and irrigation uses. These two main sets of data were chosen to emphasize the change in WQI within this period, denoting the time before the epidemic COVID19 and after the lockdown of the epidemic in 2021 in the study area. Fifteen physicochemical water parameters were measured. The results show that the WQI for the surface water monitoring sites is classified as good quality except for S8, which showed a poor water quality type. In addition, S2 has recorded a BOD concentration of 6.4 mg/L, which is slightly above the Egyptian limit (6 mg/L). Also, S8 recorded a slight increase in Fe, Mn, and F compared to permissible concentrations. TDS varies between 258.08, 318, and (249 ± 18.2) mg/L for minimum, maximum, and average ± standard deviation, respectively, indicating suitable irrigation water. The study suggests that surface water can be used to irrigate crops, but it should be purified before being used for drinking purposes. A comparison of the water quality parameters for the years 2014 and 2021 for the sites S1, S4, S5, S7, S9, and S10 reveals an increase in water quality from poor (2014) to good (2021). Therefore, the poor water quality in 2014 can be referred the effect of inadequate sewage treatment, industrial wastewater flows, and urban runoff discharge, which had been decreased with the decrease in different activities during the epidemic period and lockdown.