Modelling water table depth variation in Southeast Asia forested peatlands using satellite rainfall data.

Carbon emissions from drained tropical peatlands are of global concern. Restoration relies on 'rewetting' to reduce water table depth (WTD), aiming to recreate natural ecosystem conditions. However, in Southeast Asia little is known about the actual WTD in undisturbed peatlands, to inform restoration targets. To fill this knowledge gap, we have modelled WTD in forested peatlands, yielding a 25-year record of indicative daily WTD, using IMERG satellite rainfall data. The model was calibrated with WTD records of undrained peat swamp forest (PSF) sites in four different regions. The resulting maps reveal a large geographic variation in natural peatland hydrology, with lowest 3-month minimum rainfall ranging from above 250 mm along northern coastlines to below 40 mm in southern parts. This causes a wide range in peatland WTD regimes, with mean annual minimum WTD varying from - 0.3 m to - 0.9 m. In wettest regions the WTD is never below - 0.5 m, which occurs frequently in other areas. We propose that these regional, seasonal and interannual variations patterns in rainfall and WTD should be reflected in peatland land- and water management targets and in interpretation of studies of hydrology, carbon cycle and fire risk in peatlands.