Comparative Study of SWAT and DNDC Applied to N Leach and Export from Subtropical Watershed

Abstract

In this study, N export from Xiangxi River Basin in subtropical watershed was measured by long-term monitoring, N loss in the basin was simulated by DNDC and SWAT models in order to provide a scientific basis for the establishment of nitrogen circulation model in subtropical watershed. The results showed that N loss with runoff was well simulated by DNDC and SWAT. The key parameters of DNDC were precipitation, slope and amount of N fertilization, while the key parameters of SWAT were GW_DELAY, CANMX, ALPHA_BF and ESCO. The deviations between simulations and observations of runoff, TN and NO3--N simulated by DNDC were 5.19%, 8.10% and 71.70%, respectively. Whereas the deviations between the emission of TN, NO3--N and NH4+-N simulated by SWAT and observations were 2.04%, 14.29% and 8.89%. The results indicated that the precision of N export simulated by SWAT was higher than DNDC in Xiangxi River Basin, and N loss in this area was mainly controlled by precipitation and nitrogen cycle of terrestrial ecosystem. The temporal and spatial distribution of N loss in Xiangxi River Basin was analyzed by comparing simulation results, which further demonstrated that DNDC and SWAT had simulation ability for N loss in subtropical watershed.