A Calibration and Dvaluation of IHACRES Model in Runoff Simulation the Lanbaran Sub-basin, Ahar Chay

Watersheds are open systems which, due to its complexity and in order to achieve the desired goals, are modeled. Through modeling, the cost of study for complex systems is reduced because large-scale field trials are very costly or impossible. Also, by analyzing the results of the model, we can manage the watersheds well. In this research, the performance of the IHACRES rainfall-runoff model was evaluated in the simulation of runoff in the Lanbarn basin.  The monthly data on rainfall and temperature of  Varzaghan station as input variables for flow simulation and observation data of runoff at Cassin hydrometric station were used to measure the accuracy of the IHACRES model. Based on available years, data from 2002-2000 were used for warming up the model and data from 2012- 2012 were used for calibration and data from 2016-2013 were used for validation purposes. To evaluate the ability of the IHACRES model in runoff simulation, the Nash-Sutcliff coefficient was used. The results showed that the coefficient was 0.71 and 0.74 for calibration and verification, respectively. Therefore, according to the results of the evaluation of the IHACRES model using different performance criteria and because of easy access, less inputs and a reduction in the time spent, it can be advised to use the model to simulate and predict runoff in a monthly scale in the Lanbarn watershed and to use it in order to study surface runoff and river flow in future periods.

In order to manage watersheds and prevent inconsistencies in measures taken at the catchment area, a model is needed which, according to the existing information and conditions, has the efficiency of simulating the outflow of the region (Yong et al., 2014:47). Integrated models require less information than distributed and semi-distributed models, and, on the other hand, they run faster than other models (Golshan et al., 2017:966). The IHACRES model is an integrated concept model that includes a nonlinear reduction model and a linear lattice model. Despite the relatively recent development of IHACRES, this model has been widely accepted among hydrological models (Sriwongsitanon & Taesombat, 2011). The number of parameters in this model is low, while simultaneously compared with distributed models, we have tried to provide more details of the internal processes (Croke & Jakeman, 2008, Golshan, et al., 2017:966).

To do this research, the monthly data on rainfall and temperature of Varzaghan station as input variables for flow simulation and observation data of runoff at Cassin hydrometric station were used to measure the accuracy of the IHACRES model. Based on available years, data from 2002-2000 were used for warming up the model and data from 2012- 2012 were used for calibration and data from 2016-2013 were used for validation purposes. The IHACRES model is an integrated metric conceptual model for rainfall-run simulation. This model was developed by Jackman in 1990. The model needs 5 to 7 variables for calibration and is suitable for implementation in large scale basins. In this study, version 2 of this software has been used, which is applicable for basins with continuous data of rainfall, temperature and runoff. This model consists of two nonlinear and linear interconnected segments that are
respectively defined for calculation of losses and effective rainfall conversion to runoff.

Based on the results, Nash-Sutcliff coefficient was 0.71 and 0.74 for calibration and verification, respectively. Therefore, it can be stated that the model of low discharge simulates well, but in simulating the maximum discharge, it has little ability and simulates lesser amounts of observational flow. In general, due to low model deviations and good simulation of minimum discharge values, it can be argued that the performance of the IHACRES model in the Lanbaran catchment area is satisfactory.

Given the diversity of rainfall-runoff models, selecting an appropriate model for watersheds is important for increasing the efficiency of planning and managing water resources. Hence, in this study, IHACRES model performance was evaluated in runoff simulation in the Lanbaran watershed. According to the results of the calibration and verification of the model in runoff simulation based on different performance criteria, the model was found to have a high accuracy in simulating runoff at the station under study. It also simulates the amount of monthly flow, which is consistent with the results of studies of Zarei et al. in the basin of Kasaliyan, Lotfirad et al. in the Nawarud basin and the studies of Croke and Jakkman. Therefore, according to the results of the evaluation of the IHACRES model using different performance criteria and because of easy access, less inputs and a reduction in the time spent, it can be advised to use the model to simulate and predict runoff in a monthly scale in the Lanbarn watershed and to use it in order to study surface runoff and river flow in future periods.