Validation of Soil Survey Estimates of Saturated Hydraulic Conductivity in Major Soils of Puerto Rico

Round 1

Reviewer 1 Report

In general, this manuscript is well written and structured. This manuscript fits the scope of the journal. I only have one general comment.

In the Introduction, the authors should summarize previous relevant research and highlight the limitations or knowledge gaps of the existing studies in using USDA PTFs to predict K_sat. In this way, the scientific significance and novelty of this manuscript can be clearly presented.

Author Response

New material reviewing previous research and current knowledge gaps has been added in lines 38 - 74 of the Introduction in the revised manuscript. 

Reviewer 2 Report

1. Fix figure 1, where is soil and where is water in this scheme?
2. I really did not understand the analysis related to Table 6

Author Response

Response to comment 1. Figure 1 (now Figure 2) has been completely redrawn.

Response to comment 2. The reviewer does not specify what part of the discussion regarding Table 6 is hard to understand, which makes it difficult for me to know how to respond. The other reviewers did not seem to have any problem with this section. I have therefore not made any changes, although I am open to making changes if the questions are made more specific.

Reviewer 3 Report

Dear Authors,

I marked copy was provided.

Best regards

Reviewer

Comments for author File: Comments.pdf

Author Response

The reviewer simply highlights lines 40-43, line 143 and lines 166-168 in the manuscript, making no comment as to what needs to be corrected or addressed. I have made some changes based on what I think the problems were.

The section in lines 40-43 has been greatly expanded following recommendations of reviewer No. 1.

Line 143 - Equation [5] has been slightly changed

lines 166-168 - Letters in the second column of Table 5 have been made lower case as indicated in the text.

Reviewer 4 Report

Dear Authors,

I really enjoyed reading your manuscript containing results and evaluation of in-situ measurements of hydraulic conductivity, although it was used for evaluation of its indirect estimates. I do recommend to accept your manuscript after minor revision. Please see my comments below.

Your manuscript evaluating the applicability and accuracy of the soil survey estimates of saturated hydraulic conductivity (Ksat) of nine major soil series of Puerto Rico is very interesting. Knowledge of Ksat value is of vital importance for any modelling of hydrological processes. Since you have based your conclusions on 202 in-situ measurements of Ksat by Guelph permeameter, some reasoning which has led you to the selection of this method would be appropriate, as no reference method for Ksat determination exists. The in-situ measured Ksat data are very valuable, but Ksat is often reported as a characteristic with high temporal and spatial variability; e.g. Rienzner and Gandolfi (2014), Kargas et al., (2021), or Gupta et al. (2006).  The spatial variability is taken into consideration within the presented study, but the temporal variability is not. Some indication about the land use and its effects on Ksat is also missing.  These are my only concerns about the presented manuscript.

 Your manuscript is nicely written, easy to follow and you utilised some current references as well. However, a relatively low number of references reflects the lack of information within the introduction dealing with the Ksat variability and also with the outcomes of others, who were evaluating the efficiency of Ksat estimates by PTF.  I would like to acknowledge the in-situ measurement of Ksat and also the detailed work to identify the locations of previous research for the PTF evaluation. The use of the one-head-method for the measurements instead the two-head-method (which is recommended in the User’s manual for scientific use due to higher accuracy) should be justified. Was it because of the soil heterogeneity? The use of one-order of magnitude range (for Ks in micrometers per second) is in my opinion a reasonable scale for the evaluation.

Please see my minor comments listed below:

MINOR COMMENTS

Lines 28-57: Introduction – should be revised, some information about the Ksat variability and PTF efficiency evaluation should be added.

Line 60: “Saturated hydraulic conductivity” instead of “Hydraulic conductivity” should be used.

Lines 59-70: Description of the Project area- some overview map with the localities and indication of the major soils of Puerto Rico would be nice

Line 63: Table 2 – I miss the classification according to the WRB soil classification system (IUSS, 2015)

Lines 71-80: Experimental techniques – type and manufacturer of the used Guelph permeameter should be stated

Lines 101-102: Different size of letters in comparison to the surroundings

Lines 109-110: Table 4: The reference does not fit - Elrick and Reynolds references are no. 15-17

Line 122: Some indication about minimum and maximum measurement times would be interesting, as it is expected that the final data records correspond to the steady-state infiltration rates.

Line 126: Missing reference to the work from which the picture is taken.

Line 162: Table 5 –  As the ratio between the (Ksat)16.5 and 83.5 is discussed, this ratio should appear in the table; also the capitalizing of the column names of the tables should be unified “Soil Horizon” vs. “statistical grouping” vs. “Rated class”

Line 177: “columns” instead of “columnsa”

Lines 202-228: Discussion – the results are not discussed int the context of other published works dealing with Ksat estimates by means of PTF

With kind regards,

Your  reviewer

References:

GUPTA, N., RUDRA, R.P., PARKIN, G. 2006. Analysis of spatial variability of hydraulic conductivity at field scale. Canadian Biosystems Engineering, 48, 1.55-1.62.

IUSS Working Group  WRB (2015) World Reference Base for Soil Resources 2014, update 2015. International soil classification system for naming soils and creating legends for soil maps. World Soil Resources Reports No. 106. FAO, Rome. .

KARGAS, G., LONDRA, P. A. & SOTIRAKOGLOU, K. 2021. Saturated Hydraulic Conductivity Measurements in a Loam Soil Covered by Native Vegetation: Spatial and Temporal Variability in the Upper Soil Layer. Geosciences, 11, 105.

RIENZNER, M. & GANDOLFI, C. 2014. Investigation of spatial and temporal variability of saturated soil hydraulic conductivity at the field-scale. Soil and Tillage Research, 135, 28-40.

Author Response

In Comments and Suggestions, the reviewer requests justification for our choice of the Guelph permeameter method for measuring Ksat, and also our decision to use the one-head vs. the two-head version of the method. To address this and other issues raised by the reviewer we have added a new paragraph (lines 179 - 196) in the Methods section.

In Comments and Suggestions, the reviewer also asks that we provide information on land use at the experimental sites, and explain why we did not consider temporal effects on variability of Ksat. Replies to both issues are given in lines 104 -107 in the Methods section and lines 294 - 299 in the Discussion section.

Responses to "Minor Comments"

1. Comment regarding lines 28-57: The literature review concerning spatial variability of Ksat and PTF methodology has been expanded (lines 38-85 of revised manuscript)
2. Comment regarding line 60: The term "hydraulic conductivity" was changed to "saturated hydraulic conductivity".
3. Comment regarding lines 59-70: A new Figure 1 was added, consisting of a map of Puerto Rico indicating locations of the major soils studied.
4. Comment regarding line 63, Table 2- Table 2 has been modified to include the approximate Reference Soil Groups in the WRB system along with the classifications in the USDA Soil Taxonomy System.
5. Comment regarding lines 71-80: Manufacturer's name and location was added in line 136 of revised manuscript.
6. Comment regarding lines 101-102: Letter sizes were adjusted.
7. Comment regarding lines 109-110: Reference listing was corrected.
8. Comment regarding line 122: An indication of times required to reach steady state permeameter flux q is described in lines 136-138 of revised manuscript.
9. Comment regarding line 126: The picture (Figure 3) was replaced by our own drawing, avoiding the need for referencing and permission.
10. Comment regarding line 162. Capitalizations were made uniform, and a new column with the K_83.5/K_16.5 ratios was added to Table 5. Also, a new Figure 5 was added to highlight relations between the K_83.5/K_16.5 ratios and geometric means of K_sat values listed in Table 5.
11. Comment regarding line 177: corrected
12. Comment regarding line 202-228: The Discussion section of the revised manuscript has been augmented to include some comparison of our results with other research.

Round 2

Reviewer 2 Report

no further comments

Reviewer 3 Report

Accept in present form