Variability effect of hydrological regime on river quality pattern and its uncertainties: case study of Zarjoob River in Iran

Saman Ebrahimi,Mahdis Khorram

doi:10.2166/hydro.2021.027

Abstract

Abstract River water quality assessment, affected by pollution load, and river regime changes in various climate conditions, is an implementation that simplifies water resources management, and justifies terms for increases or decreases in human activities. The current paper aims to offer a water quality model of a river considering parametric, hydrologic, and pollution load uncertainty by using uncertainty indexes like Plevel, ARIL, and NUE. These indexes were used to analyze the influences of the model's parameters and the river's regime alternations on the results. A Qual2K model, calibrated with PSO algorithm, is presented and connected to GLUE algorithm to assess the model's uncertainties like effective input parameters on the modeled variations, headwater flow, and input pollutions. Zarjoob River, in the north of Iran, was chosen as the case study. The results illustrate that the interaction among parameters, hydrologic and pollutant discharge data should be considered in river water quality simulation. The presented methodology can analyze the influences of parametric uncertainty, parametric and hydrologic uncertainty, and pollution input load uncertainty according to any quantity of observations and the modeled results of any river.

Highlights

Most of the rivers in the world have been threatened seriously by discharging pollution, mostly wastewater, caused by human interventions
The Plevel index values are usually equal to or less than 80% for all five variables, which implies the importance of considering hydrological uncertainty
The results were more valuable in the second half of the year, and this reflects the specific circumstances of the case study

Summary

Introduction

Most of the rivers in the world have been threatened seriously by discharging pollution, mostly wastewater, caused by human interventions. Many water quality models have been developed to simulate river water quality. One of the wellknown models, Qual2K, which is the last version of the Qual series presented by EPA (the United States Environmental Protection Agency), can simulate river water quality equations in both steady and quasi-dynamic conditions, and analyze its uncertainties (Kim & Je 2006; Rode et al 2007). Quality modeling almost comes with slight gaps among observations and modeled results leading to the uncertainty of a model. The existence of these differences gives a realistic perspective on river water quality modeling

Methods

Results

Conclusion