General Comments

This paper uses soil moisture measurements to estimate recharge to a karst groundwater system via a soil drainage model. The karst outflow is from a single spring, whose discharge is used for comparison with the estimated recharge. The model performed reasonably well for single rainfall events and simulated 88% of the long-term average annual recharge volume for a Swabian Alb catchment.

 The research question is well within the scope of HESS and presents novel concepts leading to a new method of estimating recharge in a karst groundwater system. The conclusions reached are substantial, relating to the validation of the method. The methods and assumptions are valid and clearly described. The experimental results are extensive and amply sufficient to support the interpretations and conclusions. Description of the method is clear and would allow the recharge estimation method to be applied to other catchments with the required data. The authors give adequate credit to related work and clearly describe their own contribution. The title is good, and the abstract is concise and appears complete.

Presentation is well structured and clear, and the language is satisfactory – some technical corrections are made below. Math formulae appear to be correct. There do not appear to be any unnecessary parts of the paper. The number and quality of references is satisfactory.  

Specific Comments

The method is original and ingenious, and works relatively well for the catchment tested, which has eight years of hourly data on rainfall, soil moisture and spring discharge available for testing. There may be problems with application to different catchments because of lack of data. In addition, catchments with substantially different types of recharge such as recharge from sinkholes or from streams flowing into sinks in their beds may present problems with implementation of the method. Larger catchments with very varied catchment areas may also present problems.

There are considerable assumptions/requirements with the method. 1. The catchment area must be delineated accurately, this may be difficult in some areas. 2. Contributions from different vegetation covers and soils (as in this study) need to be assessed by multiple soil moisture measurement sites. 3. For comparison with the recharge estimated from the soil measurements, the spring discharge should be able to accurately represent groundwater recharge. This may be difficult in systems with several outlets.

Technical Comments

L52 What does ‘edaphic’ mean? It’s not in my dictionary.

L64 ‘advise’ not ‘advice’

L77 ’.. observation in an ungauged ..’ not ‘.. observation and on ungauged ..’

L167 Poor English

L185 Delete ‘is’ i.e. ‘.. +1 or -1 the stronger is ..’ not ‘.. +1 or -1 is the stronger is ..’

L169 Caption Figure 2 Delete word ‘exemplified’ i.e. ‘.. in this study for the attribution ..’ not ‘.. in this study exemplified for the attribution ..’

L376 ‘On the other hand,’ not ‘In another hand,’

L432 ‘.. that a soil moisture ..’ not ‘.. that no soil moisture ..’

L448 Omit words ‘it is more meant that’

L450 ‘.. the wider the range of pore sizes (Cary ..’ not ‘.. the wider is the range of pore sizes are (Cary ..’

L459 ‘..use a simple overflow bucket model that simulates zero ..’ not ‘..use simple overflow bucket model that simulate zero ..’

L462 ‘considerable’ not ‘considerably’

L464 ‘.. could be linked clearly to both a soil moisture and a recharge event. ..’ not ‘.. could clearly be linked to only a soil moisture events and a recharge event. ..’

L469 ‘led’ not ‘lead’

L472 ‘.. we expected ..’ not ‘.. we were expected ..’

L475 ‘measurement’ not ‘measurements’

L477 ‘events’ not ‘event’

L496 ‘.. usually have very high permeabilities ( ..’ not ‘.. usually presents a very high rocks permeability ( ..’

This paper tries to link precipitation- soil moisture- recharge relationship in catchment area scale of karst aquifer environment Good results and discussions are valid and clearly described. The contents of the paper are good and with valuable information to share with related field. 

Just some minor points suggest to check before the publishing:

1.There are limited information about the data distribution. For example, 15 sites of soil moisture measurement and discharge hydrograph. It's quite importance to evaluate characteristic from time series of different observation. I like to suggest to authors to add some typical hydrograph or data plots in suitable time windows.

2.Some challenges rises after author use three spatially-combined-averaged soil moisture time series: grassland (G), woodland (W) and all area (C). It's needs to have some assumption and simplify the sites specific and spatially heterogeneity. Specially the karst surface - groundwater system will be spatially continuity such as G-W-G or W-G-W... from upstream to downstream. Such assumption as the paper describe could be only on infiltration processes and assume homogeneous after that.

3. Precipitation- soil moisture- recharge relationship as Fig.2, the paper chose "temporal delays" with a simple temporal buffer. Actually, the time lag or responses lag could be evaluating from cross check between two time-series. Such quantitative linkages also needed to support the following analysis and discussion.

4.I am concerning the precipitation- soil moisture- recharge relationship analysis is event base, and the referred hydraulic parameters also random walks or with discrete distribution. For the calculation in catchment scale or annual flow in close years, such representative hydraulic parameters should be stable. It's better to check the time-variation of the related parameter between different events.