Improving kinematic wave routing scheme in Community Land Model

Version 3.5 of Community Land Model (CLM) has incorporated a river routing module, called the River Transport Model (RTM), to simulate the runoff routing process over a hydrologic basin. RTM treats river routing as a linear reservoir process propagated through a gridded domain. Because the flow velocity at each grid is set as a constant, RTM cannot simulate river routing well. In this paper, we developed a large scale catchment-based kinematic wave routing (KWR) model to be coupled with CLM, which simulates the movement of water through floodplains and river channels. An advantage of KWR over RTM is that the flow velocity is calculated by the Manning equation, which considers the difference in friction slope and hydraulic radius in each sub-basin (or grid) and time step. A second advantage is that the KWR velocity parameterization accounts for spatial–temporal variability. Using the daily runoff simulations in continental China over the time period 1995–2004 from CLM3.5 as inputs to both RTM and KWR, we found that the simulated discharge of KWR is closer to observed discharge than that of RTM. Our study has shown that KWR may be a valid alternative to RTM in CLM.