The Analysis of Vertical Hydraulic Conductivity of the Riverbed Over Time ‒ A Case Study of Downstream of Ziarat River, Northern Iran

Abstract

Vertical hydraulic conductivity (K v ) of riverbed is an important variable exerting impact on the exchange of water and salts between riverbeds and the surrounding underground water systems. However, there is little detailed information on the spatial variations of the riverbed K v , and there is hardly any information on its timing variations. Time changes in the amount of K v of the riverbed reveal the need for further studies as a potentially significant controlling factor in temporal variations in the amount and spatial patterns of water fluxes and solutes between groundwater and surface waters. With this in view, this study adopted a time series analysis approach to investigate the hydraulic conductivity measured over a year from January 2016 to January 2017 on a weekly basis for a downstream point of the Gorgan Ziarat River, Iran. The researchers first began to verify the hydraulic conductivity data, which was a downward trend during this period, from the particle size distribution of the riverbed for several times over the course of a year. Then, after identifying the existing data trends, autocorrelation and partial autocorrelation coefficients were determined. Finally, an ARMA model (1,1) was identified as the superior model. The mean squared error was used to evaluate the selected model. Moreover, Pert-Manto test was used to test the validity and reliability of the model.