Reply to comments of referee #1

I find the scope of the study is not clear. From an hydrological point of view, a distinction/categorization of the wetland types in two main classes could be done: i) the wetland generated by an increase of the water table depth from below, i.e. wetlands resulting from vertical water fluxes (peatlands, swamps, marsh; hereafter called ”saturated wetlands”) and 2) the floodplains, i.e. wetlands associated with a river and resulting from horizontal flows. The main interest of the paper is to try to simulate these two kinds of wetlands with a common approach and to test if this latter could reproduce with success the big patterns of the wetland distribution at the global scale. Some indications let think it is also the aim of the authors, e.g.: p409;l14-15 “Both parts share a joint water storage” with “both parts" referring to the land surface model part computing the vertical water fluxes and a state of the art river routing model.p412;l1-5: The authors do a distinction based on the topography between areas where the “water is distributed over a large plain” . vs. areas where a “new water volume is need to raise the water table”. But this aim is not clearly stated in the draft. Thus, the reader wonders if the authors model floodplains, saturated wetlands or the both until the end of the Method section. I found the problematic is not well described in the draft. Thanks to this comment, we see that a more elaborate paragraph on the rational of our model development is needed. The major scope of our study is the development of a simple hydrological scheme dedicated to represent the global distribution and extent variability of very different kinds of wetlands. The scheme is designed for the application in complex Earth System Models (ESMs) on global scale with medium to coarse resolutions, because we feel that the representation of surface water dynamics is – albeit important – not strongly developed in such models. While an explicit representation of wetland dynamics is necessary for the calculation of CH4 emissions, we also expect an improved simulation of the hydrological cycle due to our scheme. From this objective several limitations arise. Of course, we strive for a realistic representation of wetland extent but nevertheless our approach needs to be simple. It should be easily implementable into different ESMs and should only require boundary data which is readily available on global scale. Thus, we want to minimize the necessity to recalibrate our model parameters for different applications or setups of the ESM in order to allow for future projections and hindcast experiments as well as for present day simulations. Thus, we restrict our scheme to the use of the general water balance terms, which are considered in all ESMs, and topographical data, which is globally available. Furthermore, we decided not to differentiate the treatment of different wetland types but to use a general approach. This simplifies the scheme as the need to derive specific parameters sets for every type of surface water body is omitted. Indeed, considering our focus on hydrological processes and the global perspective of the approach, we argue that the different surface water bodies are very similar in that respect and only vary in the relation of the different water fluxes in their water balance as well as their topographic conditions. Both aspects are explicitly accounted for in our approach. Being restricted to hydrological indices only, we also lack the means to classify our simulated water body fractions into different type of wetlands or even separate between wetlands and lakes. We kept the term “wetland” though as wetlands represent the largest fraction of surface water bodies on the land surface. Nonetheless, we find your proposed separation of wetland types into saturated wetlands and floodplains very useful. It reflects our model structure with the separate modules for the computation of vertical and horizontal water fluxes and will clearly improve the comprehensibility of our method. Please note that in our approach both water balances are coupled. Thus, we do not model only the one or the other type but also allow for wetlands that are influenced by both regimes of water flow or vary seasonally between the dominance of either horizontal or vertical water fluxes. We will include this explanation in the beginning of our manuscript to avoid any confusion about