Water shortages in arid and semi-arid areas necessitate effective methods to intake surface and subsurface river flows. Classical river intakes due to construction cost, and high sedimentation cannot be justified for ephemeral streams in arid zones. The underground dams and subsurface intakes are proposed for water harvesting in these areas. Lower construction cost and less downstream destructive effects cause the subsurface intakes to be superior to underground dams. In this type of intake a pipe drain system is installed in a very porous media under the river bed. Two types of these intakes have been constructed in a few ephemeral streams in Khorasan Razavi province without being the theoretical aspects paid attention effectively. In this study, the effective parameters, particularly the grain size of the porous media, on subsurface water diversion was experimentally investigated. The results showed that with increasing the water head above the drain pipes, the drains flow rate increased and reached a rather constant flow rate depending on drain flow rate capacity. The particle size of the porous medium had a significant effect on the drains flow rate. Decreased particle size and consequently hydraulic conductivity caused the diverted flow rate diminished significantly. In order to relate effective parameters and water diversion, some regression equations were also obtained.