General Comments

Here the authors explore different model complexities and configurations to highlight the need for coupling upland-wetland interactions in land surface models to better capture downstream hydrologic fluxes. In general, the inclusion of wetlands in LSMs is an important consideration for many types of landscapes. Overall, the manuscript was clear and the approach was sound. Below are some points that I think the authors should consider to help clarify some points for the reader.  

One broad comment is that there is a bit of a disconnect in how the manuscript was framed (the title, abstract, introduction had a heavier emphasis on wetlands in general) vs the actual analysis and discussion (much larger emphasis on fens, which is the study site). The conclusions were logical based on the data from the fen, but it would be helpful to a) emphasize that fens by definition receive significant amounts of groundwater inputs and b) how other types of wetlands with different levels of GW connectivity could change your conclusions.

Specific Comments

• It would be helpful to reference more existing literature on the need for including proper interaction between wetlands and the upland to help strengthen the case for this particular study. While there may not be as many LSM studies that look at this directly, drawing parallels to watershed scale studies, which has quite a few studies in the recent years.
• Minor suggestions for Figure 1
  • Expand part d to be larger to match the other panels for clarity;
  • add the location of POJP piezometer for clearer connection to panel c);
  • if possible, indicate the extent of the fen in part d) just to give some context for the reader. I understand that this can be variable throughout the fen. If the fen goes beyond the transect, ignore this comment!
• L123: The statement regarding the amount of surface water vs groundwater into the fen seems something unique to this system, and isn’t necessarily a feature of the V2 configuration – consider putting this elsewhere. As a side note, because I don’t have much context to the wetland:upland ratio or the water balance, the reader might be surprised by this statement. Might be worth indicating the relative areas for the wetland + upland and/or some estimated water balance in the site description
• L137: does the MESH-CLASS model have saturation-excess and infiltration-excess runoff components to determine runoff vs recharge? Similarly, how does it calculate the R flux? I would not expect a full description of the model, but since this is a major connection to the GW component, it would be helpful to briefly describe it. Also, is snow accumulation and melt modelled in the upland? I assume so, but since it’s explicitly mentioned in the fen model, but not here, it can create confusion
• L148: I may be mistaken, but I don’t think Figure 1 show the groundwater divide/no-flow boundary condition (this is in Fig 2?)
• L151 and paragraph: would be helpful to mention how dx is determined within the Darcy’s Law calculation
• L165: Units are not consistent across equation. If Ro is upland runoff (m3/d) and L is the hillslope length (m), the units are [L4/T]; similarly the (Rg+M-Ef)wf component have units of [L2/T], while the Q terms are [L3/T].
• L168: Are Cspill, hspill, n calibrated parameters, and is the model sensitive to them? I believe they are not referenced again later on but one might assume that they have major roles in changing Q.
• L181: Is there any downstream gage to calibrate? I would be hesitant to say that calibrating the GWT in the upland represents the performance of the collective fen-upland-GW models - especially since three of them do not have the backwards interaction in the model structure
• L185: were these all generated from uniform distributions?
• L186: maybe use “(threshold is chosen arbitrarily based on…)” instead of “chosen rather arbitrary”
• L189: I would consider putting in the best parameter set in Table 1 to give context for readers rather than just embedded in the text later on
• L194: are these L values corresponding to likely wetland-upland areas?
• Figure 3: Should write in caption the simulation number (V1?)
• Figure 6d: missing y axis label to be consistent
• L291: It is slightly hard to understand why at low L values, the groundwater table does not fluctuate in the chained model – it would be worth discussing why. I would assume there’s still stochastic inputs to the groundwater from recharge/precipitation, and it’s not that the groundwater table has reached the lower boundary/bedrock
• L306: Land is capitalized mid-sentence
• L306: Because the reader does not know how the forest and grass (is it solely a runoff-coefficient difference, or does ET get affected too?) affects the model fluxes, it’s hard to attribute the changes in the model to solely the soil properties, which is the focus of this section.
• L313: I think that for this instance, it is true that the chained approach is adequate to illustrate the coarse grained soil texture. But I think it’s worth commenting that in areas of smaller hillslopes/contributing areas, that may not be the case (as proven in your previous experiment)
• L346: I would not necessarily include wetlands in ‘fen/wetlands’ as fens by definition have a lot of GW inputs. Having wetlands here can cause readers to assume that wetlands that either have more bi-directional interactions with the upland via groundwater, or don’t receive groundwater, should be treated the same way. While the authors wouldn’t run more simulations to capture other wetland types, I think it’s a valuable discussion point