Irrigation and Water Engineering

Irrigation and Water Engineering

Simulation of Thermal Stratification and Dissolved Oxygen Dynamics in the Zayandeh-Rud Reservoir under Inflow Variation Scenarios Using the CE-QUAL-W2 Model

Articles in Press

Document Type : Original Article

Authors
Seyedeh Hadis Shahrokhi 1
Hassan Torabi podeh 2
Amir Hamzeh Haghiabi 3
Pooneh Saeidi 4
1 Candidate in Hydraulic Structures, Department of Water Engineering, Faculty of Agriculture, Lorestan University,
2 Ph.D. Student In Water Structure of Lorestan University, Khorramabad, Iran
3 Professor, Department of Water Engineering, Faculty of Agriculture, Lorestan University
4 . PhD. Environmental Science/Engineering Water Resources track, Tarbiat Modares University
10.22125/iwe.2026.584109.1925
Abstract
Dissolved oxygen and thermal stratification are among the most critical parameters controlling water quality and ecosystem stability in reservoir systems. In arid and semi-arid regions, these processes are intensified by drought, climate change, and particularly declining water levels and reduced inflows. In the present study, the thermal and oxygen responses of the Zayandeh-Rood Reservoir to inflow variations were investigated using the two-dimensional longitudinal-vertical numerical model CE-QUAL-W2. The primary objective of this study was to assess the impact of inflow reduction on reservoir water level, thermal stratification stability, the vertical distribution of dissolved oxygen (DO), and the identification of critical elevations associated with severe water quality deterioration. The model was calibrated and validated using observational data from the 2020–2021 water year.The results indicated that the water level simulation achieved high accuracy after correcting the reservoir bathymetry (stage-volume relationship) and optimizing parameters, yielding a Mean Absolute Error (MAE) of 2.7 cm" and a Root Mean Square Error (RMSE) of 3.3" cm" . Furthermore, the model demonstrated excellent agreement with observed values during thermal and dissolved oxygen calibration; for temperature, the MAE and RMSE reached 0.64^∘ C and 0.81^∘ C , respectively, while for dissolved oxygen, the MAE and RMSE values were 0.89mg/L and 1.12mg/L , respectively.
Keywords
Zayandeh-Rud Reservoir
:thermal stratification:Residence time: climate change
: CE-QUAL-W2
Subjects
Irrigation and Water Engineering

Articles in Press, Accepted Manuscript
Available Online from 18 August 2026