Trend Analysis of Temporal Changes of Discharge and Water Quality Parameters of Ajichay River in Four Recent Decades

Abstract

This study analyzes changes and trends in discharge—mostly because of climate changes—of Ajichay River at Vanyar station and its water quality. Ajichay basin is located in East Azerbayjan province, Northwest of Iran. Five water quality indicators, including sodium (Na), Chlorine (Cl), Sodium Absorption Ratio (SAR), Total Dissolved Solids (TDS), and Electrical Conductivity (EC) were selected to analyze change in water quality. Trend analysis performed in wet and dry seasons where October and June were indicators of wet and dry seasons in year, respectively. Trend analysis was conducted using the two methods, which are conventional MK (for series having insignificant autocorrelations) and modified MK (for series having significant autocorrelations). Results showed that with decreasing trend in discharge all selected water quality parameters had an increasing trend in both wet and dry seasons. Based on Estimations increasing trend of Na, Cl, EC, TDS, and SAR in dry seasons were more rapid than trends in wet seasons. In conformity with that, Decreasing trend of discharge in wet seasons were more rapid than trends in dry seasons equal to \(-\)0.25 and \(-\)0.02 (m\(^{3}\)/s/year), respectively for wet and dry seasons. Calculated Slopes indicated a considerable increasing trend in water quality parameters in four recent decades, especially in dry seasons.