Investigating Roles of Baseflow on Water Level in Lake Urmia, Iran

Lake Urmia has experienced a decline in water level by about 40 cm per year in recent decades. Investigating the relationship between baseflow and water level in the lake is essential for better understanding of changes in water level. This study aims to estimate baseflow in the Urmia basin for analyzing the interaction between changes in baseflow and water level in the lake. The Eckhardt filter and mass balance filter (MBF) were considered for baseflow separation at nine stations in the Urmia basin with observation data from 2010 to 2018. It should be noted that each result for baseflow separation was compared in terms of catchment characteristics and climate parameters. Here, the constant filter α and BFImax (the maximum value of the baseflow index (BFI)) were estimated for the Eckhardt filter. Also, electrical conductivity (EC) was used to determine baseflow from the MBF. The relationship between groundwater, baseflow, and water level in the lake was determined by Kendall-Tau coefficients. The result shows that the value of 0.978 for α has the best performance in baseflow estimation from the Eckhardt filter and MBF. The relationship between groundwater, baseflow, and water level in the lake was statistically significant with respect to Kendall-Tau correlations (p ≤ 0.05). The BFI shows that 70% of the runoff at Lake Urmia comes from streamflow, and indicates potential risks of changes in groundwater levels.

 

Keywords: Baseflow Separation, Water Level, Eckhardt Filter, Mass Balance Filter, Baseflow Index, Lake Urmia