Interactive comment on “ Quantifying heterogeneous transport of a tracer and a degradable contaminant in the field , under two infiltration rates ” by D . Schotanus

In general, the abstract needs revision in terms of wording and line of argumentation. P1 L2: “of a non-degradable tracer” – per definition a tracer should be non-degradable and should not sorb. Better use “conservative tracer” P1 L3: should be:..field experiments were performed P1 L5: should be: During the second. . .. P1 L8: should be:..correlated, indicating that. . . P1 L8: here you argue that the flow path are stable between the seasons which will not be supported by the data presented. The only conclusion you can draw is that they are comparable between the two experiments. Later you argue that the preferential flow is not induced by macropores but by local differences in soil hydraulic properties. But if you assume that this will be the case, flow pattern will change in dependency of the flow rate imposed (or the actual water content). This has been already shown by Roth (1995). P1 P9-11: weak sentence P1 L11: should be: Therefore, . . . P1 L13: What do you mean by clustering? P1 L13: the leached mass. . . this should be the case if the substance is degradable and if the temperature is high enough. On the other hand, the second part is highly interesting


Specific Comments: Abstract:
In general, the abstract needs revision in terms of wording and line of argumentation.P1 L2: "of a non-degradable tracer"per definition a tracer should be non-degradable and should not sorb.Better use "conservative tracer" To avoid ambiguity, we deleted the 'non-degradable' and now just refer to 'tracer'.
P1 L3: should be:..field experiments were performed P1 L5: should be: During the second. ... P1 L8: should be:..correlated, indicating that. . .We changed this in the ms.P1 L8: here you argue that the flow path are stable between the seasons which will not be supported by the data presented.The only conclusion you can draw is that they are comparable between the two experiments.Later you argue that the preferential flow is not induced by macropores but by local differences in soil hydraulic properties.But if you assume that this will be the case, flow pattern will change in dependency of the flow rate imposed (or the actual water content).This has been already shown by Roth (1995).The phrasing of the reviewer is more exact.Hence, we changed the comparison between seasons, in the new version we conclude that the flow paths were stable between the two experiments.P1 P9-11: weak sentence P1 L11: should be: Therefore, . . .We changed this in the ms.

P1 L13: What do you mean by clustering?
By clustering we mean that several high leaching cells tend to be close to each other.We changed this sentence to: 'With higher infiltration rates, the high and low leaching cells were more clustered.'.P1 L13: the leached mass. . .-this should be the case if the substance is degradable and if the temperature is high enough.On the other hand, the second part is highly interesting but due to the constant flow not surprising.Please discuss critically.The flow was not constant.We clarified the discussion of this finding is in the results section, lines 429-436.P1 L15-16: Please rewrite the sentence and do not list up some findings without giving any interpretation or discussion here.We have rewritten these lines, while keeping in mind the abstract should be concise.The full discussion can of course be found in the result section.

P1 L18: weak sentence and line of argumentation
We changed this sentence to: "The persistence of the flow paths during the experiments suggests soil heterogeneity as the driver for heterogeneous flow and solute transport, in this soil.At the MCS scale heterogeneous snowmelt did not seem to have much influence on the flow and solute paths."

Introduction:
In general, the introduction needs strong revisions in terms of references used and the line of argumentation.For example, there is a nice review from Javis (European Journal of Soil Science, 2007) which should give some background information and should also be cited.We included review papers from Flury (1996), Simunek et al (2003), Jarvis (2007), Feyen et al (1998), Weihermüller et al (2007), and Allaire et al (2009).Furthermore, we streamlined the introduction for a better line of argumentation for our objectives.
P2 L22: should be core, profile, and landscape scale We changed this in the ms.P2 L25: when average parameters. ..-for the soil hydraulic properties this is not an average of all single properties but an effective set of parameters.For climatic parameters this is slightly different, because short time high flow will not be captured by the daily mean We changed average in effective.
P2 L26: should be: hydrological models We changed this in the ms.P2 L26-27: weak sentence: maybe like this: To account for preferential flow in the models additional parameters are needed. ... We changed this in the ms.

P2 L28-29: weak sentence
We changed this sentence to 'It is important to identify the main process that causes preferential flow, when solute transport is modelled.'.P2 L30: should be: . ..insight which. . .P2 L30: should be: Based on this knowledge. . .P2 L45: . ..is saturated.closeto saturation.Not necessarily at saturation We changed this in the ms.Part of this paragraph has been removed for a better focus in the introduction.
P2 L50-52: what do you want to say?This seems logic if you will have a closer look at the conductivity function.In general, I do have the impression that you did not well capture the ideas presented by Roth (1995).In general, they presented a microscopic heterogeneity and not macroscopic large scale heterogeneity.Therefore, it would be would be hard to present K-values at this short distances.It is apparent that we did not represent the Roth paper such that the content is represented well enough.However, we disagree about what he represented: hydraulic conductivity was indeed an autocorrelated lognormally distributed property at a scale larger than that of microscopic variability, hence the 'channeling' type of flow.However, this part has been removed from the ms for a better focus in the introduction.P3 L56: What do you mean?If the soil is dry you will not have any preferential flow at all.I believe you would like to state something different such as the flow path will change due to. ... But if you do so please provide reasons why.We mean that preferential flow paths might originate elsewhere after saturation or drying.However, we removed this part from the introduction.P3 L56-57: Not necessarily.It depends on the conductivity in dependence of the actual water content.Please clarify.P3 L57-58: see comment above P3 L61: This might be the case here but if you will have swelling or if cracking might occur this might look differently.Maybe not in effective parameters such as velocity and dispersivity but maybe in the transport pathways.These parts have been removed from the ms for a better focus in the introduction.
P3 L67: please delete: when macropores exist than when only matrix flow occurs.Or reformulate We deleted 'when macropores exist'.We want to compare the effects of macropore flow and matrix flow for degradable solutes.Therefore, we still include matrix flow in this sentence.
P3 L68: biodegradationthis is not only restricted to biodegradation.Also thermal degradation and photodegradation might play a role.We agree with the reviewer and removed "bio".P3 L74: weak sentence.We changed this part of the sentence to 'because the biodegradation rate depends on temperature, and soil moisture content, amongst others'.P3 L79: using wick samplers. . .or lysimeters, or porous plates as shown for example by Kasteel, R., Pütz, T., & Vereecken, H. ( 2006).An experimental and numerical study on flow and transport in a field soil using zero-tension lysimeters and suction plates.European Journal of Soil Science, 58(3), 632-645.) We added this to the ms.P3 L80: I do not see the problem here.The biggest problem is the limited range of pressure, and therefore, that water will not be sampled if the soil is not close to saturation.There is also a review available dealing with such instruments from Weihermüller (2007, JEQ) A wick sampler applies a constant pressure.With a constant pressure, water may flow to the sampler, or around the sampler, depending on the pressure in the sampler and the soil.With a variable pressure in the sampler that is adjusted to the pressure head, this effect will be much smaller.In the reference from Weihermuller also porous plates with variable pressure are discussed.We included this review in the ms.P3 L82: To overcome these disadvantages Bloem et al. ... P3 L83: Additionally, the spatial resolution of the MCS is high and fluxes through individual 3.15. ... . .We changed this in the ms.P3 L85-89: What do you want to say? P4 first paragraph: Please do not list up all information you can find.Better to put them into a nice order of argumentation.We changed the order of the sentences in this part.P4 L13: first point: I do not really believe that you can answer this question based on your given experimental setup.See also all detailed questions raised above.We extended the research question, such that it can be answered with the experimental setup.
Materials and Methods: P4 L123: Reference should be at the end of the sentence.Or better state that details can be looked up at French et al. (1994).We changed this in the ms.
P5 L131: The pressure in the MCs was variable.-In space or time?Tab 2:Caption should be: Solute transport parameters with pore water velocity v, dispersion coefficient D, and dispersivity lambda, (equation) for fast, average, and slow cells, as well as for the entire sampler.Does it make sense to show also dispersion coefficient if you also show dispersivity?All units are missing in caption.We changed the caption and removed the column with the dispersion coefficient.
Tab. 3: Caption should be: . . .Moran's I, A with 1 indicates perfect spatial autocorrelation, and -0.01 no spatial autocorrelation We changed this in the ms.

Figures:
Fig. 3: should be : daily mean air temperature.All units are missing.We changed this in the ms.
Fig. 4: delete same remarks as. . .and add full figure description because it is not the same as in Fig. 3.We changed the captions of Figs 3 and 4. Fig. 5: Why don't you rescale the drainage in the legend instead of suing 10 by the power of -1? Caption: should be of the cumulative drainage since solute application.Consequently the last sentence can be deleted.We changed this in the ms.

Fig.6: same as above
We changed this in the ms.Fig. 7: I would always sue full units or at least define it as volumetric water content.Otherwise it can be also gravimetric water content We changed Fig. 7, now the pressure head is shown instead of the soil moisture content, as the pressure was measured (not the soil moisture content).Maybe better to express cumulative area in percentage as you did in the text.Should be drainage, bromide, or PG leaching.We use cumulative sampler area in percentage instead of m2.We changed the caption as suggested.

Fig. 8 :
Fig. 8: Delete "marked with ellipses" We changed this in the ms.

Fig. 12 :
Fig. 12: There is some duplication in the caption: What do you mean by parallel flow?Do you mean 1-D vertical flow?We changed parallel flow in uniform flow in the captions of Figs 14 and 12, which is generally used.

Fig. 13 :
Fig.13: Should be Normalized cumulative drainage. . .Delete the unit at the end of first sentence.Maybe better to express cumulative area in percentage as you did in the text.Should be drainage, bromide, or PG leaching.We use cumulative sampler area in percentage instead of m2.We changed the caption as suggested.

Fig. 14 :
Fig. 14: indicate the 1.1 line in the plots with 1:1.Again what do you mean by parallelflow?Delet the last sentence if you add in the 1:1 in the plots.We included '1:1' in the figure, and removed the last sentence of the caption.