Water Quality Index variations in a Mediterranean reservoir: a multivariate statistical analysis relating it to different variables over 8 years

Evaluating the status of the water quality of freshwater bodies is crucial for safe use. In this work, the water quality of an understudied Mediterranean reservoir was investigated, using Water Quality Index (WQI) and principle component analysis (PCA) during an 8-year study period, between 2009 and 2016. The WQI was analyzed based on weighted sum aggregation function, considering the following variables: temperature, salinity, pH, conductivity, dissolved oxygen, nitrate, nitrite, ammonia, phosphate, sulfate, and total dissolved solids. After describing the evolution of these variables, WQI was evaluated. It was mostly moderate and showed a deteriorating trend between 2009 and 2016. This deterioration was due to the previously weakened water infrastructure that was furthermore impacted by the sudden increase in the habitants of the basin following Syrian refugees influx after 2011 Syrian crisis. In a new approach, WQI results were also compared to river inflow, reservoir water depth and precipitation. WQI increased with the increased water depth and water volume of the reservoir showing better water quality. Monthly precipitation above 250 mm showed better water quality and increased WQI. No clear relation was found between the WQI and the river flow. PCA analysis indicated that water quality in the reservoir was affected by erosion and fertilizers. WQI results agreed with Carlson Trophic State Index previously applied to the reservoir. These innovative results linking WQI to hydrological variables, urbanization, and trophic index together with the incorporation of PCA with WQI provide a multidimensional nature of water quality evaluation concept.

Automated summary

This study investigated the water quality of a Mediterranean reservoir using Water Quality Index (WQI) and principle component analysis (PCA) during the years 2009-2016. The findings showed a deteriorating trend in WQI during this period, attributed to weakened water infrastructure and influx of Syrian refugees following the 2011 crisis. Additionally, relationships were observed between WQI and reservoir water depth, precipitation, and PCA results, highlighting the multidimensional nature of water quality evaluation.