Surface water quality evaluation of the historic Esinmirin River of antiquity, Ile-Ife, Nigeria.

Esinmirin River is an important historic ancient river in Ile-Ife, the source of the Yoruba Kingdom that was associated with mystical power in stabilizing the ancient city during the period of war that would have destroyed it. The water resource needs investigation because of the recent anthropogenic and industrial activities that could affect the river. The study examines the river's physicochemical, heavy metals, and bacteriological parameters in the upstream, midstream, and downstream sections to comprehend the pollution levels of the Esinmirin River. Nine samples were collected in May 2023 by composite method at various sections using a systematic sampling technique. Twenty-one parameters including the physical, chemical, heavy metals, and bacteriological were examined. A significant departure from WHO, and SON permissible water standard limits in temperature, iron, and the various bacteria found in the research, brings to light the alarming pollution levels of the river. Though temperature (29.9 °C-30.9 °C) and iron (0.7 mg/L-1.3 mg/L) in the 3 sections were above the standard guidelines while lead, copper, and cadmium were absent, all other physicochemical parameters were within the limits. The pH values were highest in the upstream, EC and TDS in the midstream, and temperature in the downstream. At the same time, the chemical parameters and iron increase progressively from upstream to downstream. However, TBC, Escherichia Coliform, Klebsiella species, Staphylococcus Aureus species, and Enterobacter species in all the sections indicated a high level of contamination. The physical, chemical, heavy metal and bacteriological parameters were significantly related mostly at p > 0.01 and on a few occasions at p > 0.05. The study recommends awareness campaigns, routine monitoring, and water treatment before use, to protect public health.