Analysis of Low Flows in Semi-Arid Watersheds: Söğütözü and Terme Creek Cases

This study aims to analyze the physical, chemical, and hydrological characteristics of low flows in the Söğütözü and Terme Creek Watersheds of Çankırı province during the dry season, and to ascertain the relationship between water quality and flow in these watersheds. The goal of the study is to clarify the causes and effects of low river flows by examining watershed characteristics, assessing water quality, and analyzing trends. Low river flows during the dry season are vital for resource utilization and ecosystem health. To achieve this, initial low flow calculations were performed using daily average flow data collected over a 43-year period, from 1967 to 2010, in both watersheds. Water sampling was conducted weekly on the same day and at the same time during the period from April to December, coinciding with the recorded low flows in these watersheds. Furthermore, an analysis was conducted to determine if a trend existed in the annual low flow index values. During the study period, 35 water samples were analyzed both physically and chemically for 18 parameters to ascertain correlation between low streamflow and water quality. Consequently, it was determined that a significant correlation existed between streamflow and phenolphthalein alkalinity, total hardness, calcium hardness, organic matter, ammonium, turbidity, pH, electrical conductivity, and salt in the Söğütözü Creek watershed; as well as between streamflow and methylorange alkalinity, total hardness, magnesium hardness, chloride, sodium, turbidity, electrical conductivity, and salt in the Terme Creek watershed. A notable trend was observed solely for the Q95 Flow Index among the five indices utilized in low flow calculations (Q95, Q90, Q75, Q50, and 7Q1).