Exploring connections between liquid/solid runoff fractions and water quality in large reservoirs´ catchments through Multivariate statistics

In river environments, the interaction between liquid and solid runoff fractions plays a crucial for understanding water flow. The magnitude of liquid runoff is directly influenced by of sediments levels, impacting water resource management and quality. Sediment mobilization by total runoff fundamentally shapes river morphology. The imperative need to comprehensively understand hydrological behavior leads us to examine the relationship between these variables and water chemical aspects. Understanding the intricate dynamics between liquid and solid runoff, influenced by sediment levels and chemical variables, is crucial for the effective sediment management of reservoirs. Multivariate statistics are commonly used to identify factors influencing sediment production during hydrological processes. The objective of this study is to apply Partial Least Squares Regression (PLSR) to identify and understand the relationship between chemical variables as predictors and hydrological processes (liquid and solid runoff), allowing a comprehensive assessment of their influence in river environments.  The case study was conducted in the Rules (Granada), Casasola, and La Viñuela reservoirs (Málaga). The results indicated a positive correlation between sediments (solid runoff) and variables such as pH, Clay (CY), Silt (ST), and Carbonates (CA). This means that as sediment levels increase, these variables also show an increasing tendency. Nevertheless, this study also revealed a negative association between sediments and Dissolved Oxygen (EG) and sand (SD) implying that as sediment levels rise, Dissolved Oxygen and sand content tend to decrease. In terms of liquid runoff, a direct relationship was primarily observed with electrical conductivity (CE), Organic Matter (MO), and Sand Content (SD). This suggests a positive connection between these variables, where higher liquid runoff is associated with higher values of electrical conductivity, organic matter, and sand content. Chemical parameters manifest in two distinct groups: one shows a strong positive relationship with sediments (pH, CY, ST, and CA), while the other (CE, MO, SD, and EG) is associated with liquid runoff. In conclusion, the study underscores the intricate dynamics between liquid runoff, sediments (solid runoff), and chemical variables in river systems, using PLSR to unveil relationships. In summary, this study underscores the crucial connection between total runoff (water and sediments), and chemical variables in river environments. These findings highlight the complexity of interactions in river systems, providing valuable insights for water management and understanding hydrological processes. Furthermore, the interaction between liquid and solid runoff fractions in river environments has direct applications for sediment management in reservoirs, enhancing decision-making knowledge for authorities.