The Reynolds Creek Experimental Watershed is defined by the Outlet Weir. About half way up Reynolds Creek from the Outlet Weir is the Tollgate weir which defines a sub-watershed that is much more influenced by snowmelt runoff. At the headwaters of Reynolds Creek the Reynolds Mountain East weir defines small first-order sub-watershed. Johnston Draw is a tributary to Dobson Creek which flows into Reynolds Creek above the Tollgate Weir.

Flats, Nancy's Gulch, Upper Sheep, and Lower Sheep are small sub-watersheds along ephemeral streams.

Murphy Creek, Macks Creek, Summit, and Reynolds Mountain West are sub-watersheds whose streamflow measurements were discontunued.