ORIGINAL ARTICLE Evaluation of integrated hydro geosphere hydrologic model in modeling of large basins subject to severe withdrawal Hossein Talebmorad, MSc1, Saeid Eslamian, PhD1, Jahangir Abedi-Koupai, PhD1, Sayed-Farhad Mousavi, PhD2, Samira Akhavan, PhD3, Kaveh Ostad-Ali-Askari, PhD4, Vijay P Singh, PhD5 Talebmorad H, Eslamian S, Abedi-Koupai J, et al. Evaluation of integrated calculation of actual evapotranspiration as a function of soil moisture in hydro geosphere hydrologic model in modeling of large basins subject to each unit of evaporation zone improves the simulation of interdependent severe withdrawal. J Environ Chem Toxicol. 2018;2(2):30-40. processes such as aquifer recharge and drainage, which is one of the difficult ABSTRACT: Simulation of large basins (over 1,000 km2) is needed for large- issues in modeling. To obtain initial conditions, the model was used in scale water resources planning and management. Due to increased volume steady state mode using 20-year average of rainfall data and withdrawal of calculations and increased heterogeneity, basin simulation is challenging. from the aquifer. Then, to apply the model in unsteady state and evaluate In areas with severe withdrawal of water resources, simulating and having its performance in daily stresses, the model was used for the period of 1992- the ability to predict future changes is important, while severe withdrawals 2005 and parameters were calibrated. Validation was done for the period complicate issues and simulation. The aim of this study is to evaluate the of 2006-2010 and results showed satisfactory hydrologic simulation of the ability of Hydro Geosphere, a fully integrated hydrologic model, to simulate study area. a large basin (Hamadan-Bahar Catchment, Iran) with an area of 2,456 km2 and severe groundwater withdrawals. In this study, fully-integrated surface/ Key Words: Hydro geosphere; Integrated hydrologic modeling; Surface water- subsurface flow modeling was done using the Hydro Geosphere model. groundwater interaction; Groundwater withdrawal; Hamadan-Bahar basin; Simultaneous solution of surface and groundwater flow equations and Evaporation ffective management of watersheds and ecosystems requires average monthly and average daily values, were assessed for the simulation Eunderstanding of hydrological processes. Increasing use of models has of average flow from the river to the aquifer and vice versa near the main enhanced the ability to assess and predict catchment behavior. In these drainage channel. They found that the model was not able to simulate the models, complex hydrologic conditions and transmission processes are maximum flow between river and aquifer with monthly or annual rainfall usually simplified. Due to the multiplicity of factors affecting the catchment time series (5). Jones et al. (6) evaluated the HGS model in the Grand River behavior is usually simulated using, numerical models. Many numerical basin (area of 75 km2 area) in southern Ontario and good agreement between models have been developed with varying degree of complexity. Numerical simulated and observed groundwater pattern, confirming the efficiency of models are based on numerical methods which are used for solving problems the Richards equation in the unsaturated zone (7). on computers by numerical calculations, often giving a table of numbers and/or graphical representations or figures. Numerical methods tend Cornelissen et al. (8) assessed the influence of spatial resolution on the simulation of spatio-temporal soil moisture variability using Hydro to emphasize the implementation of algorithms. The aim of numerical 2 methods is therefore to provide systematic methods for solving problems in a Geosphere in a forested catchment (area of 0.27 km ). Discharge and soil numerical form. The process of solving problems generally involves starting moisture simulations were in an agreement with measured water balance and from an initial condition, using high precision digital computers, following discharge dynamics. the steps in the algorithms, and finally obtaining the results (1). Numerical Cornelissen et al. (9) investigated the parameter sensitivity in HGS in the methods are becoming more and more important in mathematical and Erkensruhr catchment (area of 41.9 km2) and precipitation was reported as engineering applications not only because of the difficulties encountered most sensitive input data with respect to total runoff and peak flow rates, in finding exact analytical solutions, but also because of the ease with while simulated evapotranspiration patterns were reported as most sensitive which numerical techniques can be used in conjunction with modern to spatially distributed land use parameterization high-speed digital computers (2). In many situations, information about the physical phenomena like hydrologic cycle involved is always pervaded MATERIALS AND METHODS with uncertainty. The uncertainty can arise in more than one place such Description of the study area as experiment part, data collection, measurement process as well as when determining the initial values (3). Therefore, it is necessary to consider the The Hamadan–Bahar basin with an area of 2456 km2 is situated between accuracy of input data and uncertainty in the results. longitudes of 48° 7’ E and 48° 52’ E and latitudes of 34°35’N and 35°12’N in western Iran (Figure 1). In this basin, most of the rivers originate from A proper model for basin simulation should be selected, depending on the southern heights (Alvand Mountains). The outlet of basin is Koshkabad purpose of modeling, conditions of the area, and the available data. The in the north-east. The mean elevation of the watershed is 2038 m above aim of this study was to assess the capability of a comprehensive hydrologic mean sea level. The average daily discharge at Koshkabad station was 2.5 model of Hydro Geosphere i(HGS) n simulating a large catchment m3 s−1 for the period of 1992–2008, with a minimum value of zero and a (Hamadan-Bahar) with an area of 2456 km2 that is being subjected to severe maximum value of 90.4 m3 s−1. The climate of the region is semiarid with groundwater withdrawal. Sudicky et al. (4) employed the model integrating mean annual precipitation of 324.5 mm and mean annual temperature of surface and subsurface flow in area of 17 km2 in southern Ontario, Canada. 11.3°C. In the Hamadan–Bahar basin, groundwater is the only available and The capability of the HGS model with integrated surface and subsurface widely used source of drinking water for rural and urban communities and flow and the effect of rainfall time series, which included the average annual, also for irrigation. Groundwater supplies approximately 88% of the water 1Department of Water Engineering, Isfahan University of Technology, Isfahan, Iran; 2Department of Water Engineering and Hydraulic Structures, Faculty of Civil Engineering; 3Water Engineering Department, College of Agriculture, Bu-Ali Sina University, Hamadan, Iran; 4Department of Civil Engineering, Isfahan (Khorasgan) Branch, Islamic Azad University, Isfahan, Iran; 5Department of Biological and Agricultural Engineering and Zachry Department of Civil Engineering, Texas A and M University, 321 Scoates Hall, 2117 TAMU, College Station, Texas, USA Correspondence: Kaveh Ostad-Ali-Askari, Department of Civil Engineering, Isfahan (Khorasgan) Branch, Islamic Azad University, Isfahan, Iran. Tell: +989126404309, Email: [email protected] Received: December 26, 2017, Accepted: January 01, 2018, Published: January 25, 2018 This open-access article is distributed under the terms of the Creative Commons Attribution Non-Commercial License (CC BY-NC) (http:// OPEN ACCESS creativecommons.org/licenses/by-nc/4.0/), which permits reuse, distribution and reproduction of the article, provided that the original work is properly cited and the reuse is restricted to noncommercial purposes. For commercial reuse, contact [email protected] J Environ Chem Toxicol Vol 2 No 2 March 2018 30 Talebmorad et al Figure 1) Study area of Hamadan-Bahar watershed in Hamadan province, Iran consumed in the Hamadan. The area of the main aquifer of the plain is 468 define the surface and bottom layers of the aquifer. The top and bottom km2 and geologically, Hamadan–Bahar aquifer is located in the Sanandaj- layers of nodes represent the soil surface and the bedrock, respectively. Sirjan metamorphic zone (Hamadan Regional Water Authority, HRWA). Elevations of the surface nodes are calculated using the basin DEM (Digital The alluvial aquifers consist mainly of gravel, sand, silt and clay (10). Elevation Model), whose pixels have dimensions equal to 20 20 m, and the bedrock node elevations are calculated using contour map provided in basin Model description geological report. Due to hardware limitations and the vastness of basin the Hydro Geosphere conceptualizes the hydrologic system comprising surface horizontal grid dimension equal to 1000 1000 m was chosen and then for and subsurface flow regimes with interactions (11). The model takes into increasing the accuracy of modeling the withdrawal wells were added to the account all key components of the hydrologic cycle. For each time step, the mesh as nodes. There were 825 withdrawal wells in the plain. Finally, the model solves surface and subsurface flow and mass transport equations surface layer was characterized with 3495 nodes and 6757 elements (Figure 2). simultaneously and provides complete water balance and solute budget. The On vertical grid, the region was divided into two upper (0-5-meter depth) surface water budget can be written as: and lower (more than 5-meter depth) parts. In order to increase the accuracy W in evapotranspiration calculation, the upper part was divided into six layers P=( QS21 − Q S) − Q GS + I + ETSSS + Q +∆ S/ ∆ t (1) with an interval of 1 meter and the lower part was divided at an interval of And the subsurface water budget as: P=( QSS21 −+ Q) ( Q GG 21 −+ Q) ( ET S + ET G) + 10 meters (14). Thus, the whole basin was divided into 14 layers. Due to WW the reduction in thickness, the distance between the layers was reduced in (QQSG+) +( ∆ S S +∆ S S) / ∆ t (2) the adjacent and non-aquifer areas.