Seasonal exploration of water quality and bioindicators of an agricultural irrigation and drinking water reservoir: Armağan Dam Lake, Kırklareli, Türkiye

This study aims to examine the water quality and dynamics of bioindicators (phytoplankton, zooplankton, and benthic macroinvertebrates) in the Armağan Dam Lake, a major freshwater reservoir that serves the drinking, domestic, irrigation, and industrial water needs of Turkey’s Thrace region. To achieve this, water and sediment samples were collected seasonally from three stations over 1 year. Results show that the water quality generally remains within acceptable limits, as defined by the World Health Organization (WHO) and the Surface Water Quality Management Regulation (SWQMR) standards for dam water. Regarding irrigation suitability, the sodium absorption rate (SAR) and magnesium rate (MgR) indices indicate that the lake is appropriate for irrigation. However, the Kelly index (KI) values are only marginally suitable, and the %Na Index suggests that it is unsuitable for irrigation. The Heavy Metal Pollution Index (HPI) indicates that the lake is free from heavy metal pollution (maximum of 98.72) and is safe for drinking. Based on the Metal Index (MI), Class II results were observed in autumn, while Class I results appeared in the other seasons. The Shannon– Wiener diversity index displayed low values (maximum H′ = 1.354) for the aquatic groups. Overall, the water quality parameters and biodiversity data suggest that the lake exhibits oligotrophic characteristics.