Hydrochemistry, water quality and health risk assessment of streams in Bismil plain, an important agricultural area in southeast Türkiye.

In this study, the water quality of Ambar, Kuruçay, Pamuk and Salat streams, which are the important tributaries of the Tigris River in the Bismil Plain (Diyarbakır, Türkiye) was assessed using 19 physicochemical parameters. Except for a few exceptions, all parameters in the water samples taken from the streams were below the drinking water limit values. Kuruçay Stream had significantly higher TOC, Na, NO, NO, Cl and SO levels and lower DO levels than other streams (p < 0.05) due to sewage water discharges, animal manure storage areas near the stream and irrigation return flows. In all streams, Ca-HCO was dominant water type. Gibbs diagram indicated that rock weathering is the major factor controlling the hydrochemistry of the streams. According to the results of water quality index (WQI), all sampling stations of Ambar, Pamuk and Salat streams and K1 station of Kuruçay Stream had "good" quality water for drinking purposes, while K2 station of Kuruçay Stream had "poor" quality water. Irrigation indices (permeability index, sodium percentage, magnesium hazard, residual sodium carbonate, Kelley's ratio, sodium adsorption ratio and potential salinity) revealed that all water samples taken from the streams were suitable for irrigation. The water samples from Ambar, Pamuk and Salat streams were in the C2S1 (medium salinity and low alkalinity) category, while the samples from Kuruçay Stream were in the C2S1 and C3S1 (high salinity and low alkalinity) categories. Both hazard quotient and hazard index values of NO-N, NO-N and F for children and adults were found below 1, indicating that adverse health effects are not expected from exposure to these contaminants via water ingestion and dermal contact. The findings of this study showed that the water quality status of Kuruçay Stream is worse as it receives large amounts of irrigation return flows compared to other streams.