Modeling suspended sediment discharge from the Waipaoa River system, New Zealand: The last 3000 years

HydroTrend, a hydrologic‐transport model, is used to simulate the water and suspended sediment discharge of the Waipaoa River system over the last 3 Kyr, a time period in which a well‐documented sequence of natural events and anthropogenic activities that profoundly impacted drainage basin processes occurred. Comparisons between observed and simulated data show that the model output replicates the frequency and distribution of flow events and the suspended sediment concentration‐discharge relationship, and the long‐term trends in suspended sediment discharge are consistent with the sediment record preserved on the middle shelf. Water discharge tracks precipitation, and average annual discharge may have been up to 20% higher and 6% lower at different times in the past. Suspended sediment discharge changed from 2.3 ± 4.5 to 14.9 ± 8.7 Mt yr −1 during the Anthropocene, increasing by 140% after Polynesian arrival, by 350% after European colonization, and by 660% after the catchment headwaters were deforested.