3.2. Temporal trends in water quality index (Y) and normalized sum of total coliform excursions (X)
The temporal changes in water quality can be directly related to the trends in excursions of coliform from their objective (the objective = ≤4000 CFU/100 ml according to Egyptian law 4/1994). The regression analysis of WQI on excursions of coliform was statistically significant in each case except El Qalaa Drain (Table 4).