ABSTRACT:Soil water potentials, slope throughflow, runoff chemistry, and isotopic composition were monitored in a 97 m2zero‐order basin within the Maimai 8 watershed on the South Island of New Zealand, for a natural rain storm and two artificial water applications. Contrary to results previously reported for other portions of the Maimai catchment, much of the runoff occurred as a shallow subsurface organic layer flow. For the 47 mm natural rain event, pre‐storm soil matric potential ranged from −60 to −150 cm H2O. No saturation was produced within the profile, and the majority of storm runoff emanated from flow within the organic horizon perched on the mineral soil surface. Hillslope applications corroborated this interpretation by showing>90 percent new water flushing with negligible mineral soil moisture response. Although the mechanisms cited in the text are not representative of the entire catchment, the study demonstrates: (1) the value of a combined physical‐chemical‐isotopic approach in quantifying slope processes, and (2) the heterogeneous nature and diversity of slope runoff pathways in a relatively homogeneou
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