Horizontal wells have screened sections that are positioned parallel to the horizontal direction. Great interests are generated in recent years to use these wells for hydrologic and environmental applications. Horizontal wells are traditionally treated as uniform-head or uniform-flux boundaries in order to provide closed-form analytical solutions. This paper will investigate the advantages and conditions of using these boundary conditions. We then propose a new conceptual and mathematical model to study flow to a horizontal well. This new model considers the head loss of flow inside a horizontal wellbore. It incorporates the Darcian flow in the porous medium and the pipe-flow inside the horizontal well into an integrated flow system by assigning an equivalent hydraulic conductivity that depends on the Reynolds number for the flow inside the horizontal well. Numerical calculations are necessary to obtain solutions for this new model. Laboratorial experiments are carried out and the results are compared with the theory. The result of this new model is compared with previous solutions obtained using either a uniform-head or uniform-flux assumptions.