Abstract: Disclosed is an in situ design for a runoff rain gauge 14 comprising an elevated storage pan 18 for storing precipitation above grade, a splitter pan 28 for partitioning the split of flow from storage to runoff and infiltration, a saturation cup 40 for measuring surface saturation of the infiltration resistance medium and a saturation cap 42 and splitter balance line 38 for communicating water levels in the saturation cup 40 to the splitter pan 28.

Abstract: Disclosed is a runoff rain gauge 100 which includes a collector tube 104, soil infiltration resistance medium 108, a runoff resistance flow element 113, a standard rain gauge 102, and runoff collection tube 114. Precipitation enters the collector tube 104 and is divided to flow into the infiltration medium 108 and runoff collection tube 114 via flow element 113. Total precipitation is read in standard rain gauge 102, runoff in tube 114, and soil infiltration in medium 108 is calculated by the difference between total precipitation and the runoff. Also disclosed are a runoff rain gauge 100 comprising: a seal leg 150 downstream from the runoff resistance flow element 113; a collector tube 104 mounted directly to the ground so that the bottom of the soil infiltration resistance medium 108 contacts the ground surface; and/or a horizontal capillary tube in the runoff resistance flow element 113 to insure self-sealing via capillary forces.