This manuscript describes a study that uses an Expanded Attenuation Factor index model to determine risk factors for a range of agricultural pesticides in terms of their potential for leaching into the groundwater environment in Saudi Arabia. The results of the study are encouraging with relative ranking of leachability comparable with monitoring data. The manuscript fits well with the scope and aims of the journal and is likely to be of interest to the journals readership. Generally, this appears to be a sound study and is presented well.

The manuscript is well written and appropriately structured although there are a few issues. Firstly, pesticide names are not all referred to in their English form. For example Attrazin should be written as Atrazine. The manuscript needs checking in this respect. Secondly, the main data source appears to be the online Pesticide Properties Database. This is abbreviated to PPDP in the article but should be PPDB. The PPDB does not, as far as I am aware, have anything to do with the European Union but is a world-wide system without permanent funding from any source. The reference to the EU should be removed or at least verified with the PPDB management team in the UK. I would also suggest that the manuscript is de-personalised and use of the first person removed (e.g. the use of we and our). Use of the first person places emphasis on the researchers and not on the science, the latter being the the main purpose of publication.

The introduction provides good background and summary to the use of pesticide risk modelling. However at line 51 the text states that the GUS index is too simple. No details have been given as to why it is too simple. This can be further questioned when the GUS index values for the pesticides given in Table 6 are explored in the context of section 3.5. As the authors themselves identify there are very few incidences where the GUS index disagrees with the broad model findings and where there are differences these are just displacement up or down a class. So it is very unclear as to where the added value for this approach is considering the additional and significant extra work involved especially if risk rankings are required. I would also argue that ranking pesticide leachability is not a helpful process as it will depend on local conditions, the time of application, weather and two individual pesticides will not behave in the same way hence rankings will be somewhat fluid. Would the authors please address this in their revisions.

An explanation of why/how the 30 pesticides used in the study have been chosen. Some of them are obsolete.

I should also point out that the reference to the Pesticide Properties Database is not the compliant with that on the database website. It seems to me that use of the one provided by the database management is required in order to comply with their terms and conditions of use. Again I would suggest that this is checked.

Minor review