摘要：This communication describes the application of a methodology designed to improve the representation of water surface profiles along drainage canals within the frame of regional groundwater modeling. It is an iterative procedure that combines the use of two public domain computational codes, MODFLOW and HEC-RAS. MODFLOW is a quasi-threedimensional finite difference model to simulate groundwater flow. The model possesses a modular structure, each module representing a feature of the hydrologic system such as return flow to drains, stream-aquifer interactions, recharge, etc. In spite of its versatility, modeling water surface profiles in drainage canals presents some limitations. The Drains Module available with MODFLOW simulates groundwater flow to drain canals as a linear function of the difference between the aquifer hydraulic head and the drain hydraulic head. The main disadvantage of this module is that considers a static representation of water surface profiles along drains. Therefore, the proposed methodology uses HEC-RAS, a 1-D code for surface water calculations, to iteratively estimate hydraulic profiles along drains in order to improve the aquifer/drain interaction process. The procedure was applied to the grounwater/surface water system of the Choele Choel Island, Río Negro, Argentina. Although more testing is needed, preliminary results show the feasibility of the approach. Smooth and realistic hydraulic profiles along drains were obtained while backwater effects were clearly represented.
