Testing the ‘two water worlds’ hypothesis under variable preferential flow conditions

Widespread observations of ecohydrological separation are interpreted by suggesting that water flowing through highly conductive soil pores resists mixing with matrix storage over periods days to months (i.e., two ‘water worlds’ exist). These interpretations imply heterogeneous flow can produce in soils, yet little mechanistic evidence exists explain this phenomenon. We quantified the between mobile moving preferential paths versus less remaining after free-drainage identify amount necessary maintain a world's scenario. Soil columns varying macropore structure were subjected simulated rainfall increasing intensity (26 mm h?1, 60 and 110 h?1) whose stable isotope signatures oscillated around known baseline values. Prior rainfall, ?2H nearly matched value used initially wet pore space whereas ?18O deviated from up 3.4‰, soils may strongly fractionate 18O. All treatments had 100% rain under lowest medium (60 intensities. The highest (110 h?1), however, reduced for all produced significantly different estimates intact compared structure. Further, artificially limiting exchange bypass most intense rainfall. show (1) precipitation offset metrics such as lc-excess d-excess yield questionable when separation, (2) distinct domain require extreme intensities (3) is an important component flow.