The influence of sugarcane crop development on rainfall interception losses

The expansion of sugarcane plantations in Brazil has raised concerns regarding its hydrological impacts. One of these impacts is related to rainfall interception, which can be expected to vary in response to substantial changes in canopy structure throughout the cropping cycle. We collected field measurements to determine interception losses and interpreted the observations using an adapted Gash model during different stages of a sugarcane ratoon cropping cycle. Cumulative gross rainfall (P_G), throughfall (TF) and stemflow (SF) were measured biweekly, along with vegetation structure measurements of leaf area index (LAI) and plant height. For the first 300 days after the first harvest, the cumulative P_G of 1095 mm was partitioned into 635 mm TF (58%) and 263 mm SF (24%). The inferred interception loss (I_L) was 263 mm (24%). There was a gradual and clear increase in I_L from 3% to 46% while partitioning between TF and SF also changed during ratoon regrowth. After model parameter optimisation, observed I_L was simulated satisfactorily. Model estimates suggested that evaporation from the saturated canopy is the main I_L pathway, followed by evaporation after storms. Plant architecture, LAI and meteorological conditions during the cropping cycle appeared the main factors determining I_L.