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Peer review report 1 on “Flow modelling of Strategically Vital Fresh Water Aquifers in Kuwait”
Journal of Hydrology: Regional Studies 9 (2017) 26–27
Contents lists available at ScienceDirect
Journal of Hydrology: Regional Studies journal homepage: www.elsevier.com/locate/ejrh
Peer Review Report
Peer review report 1 on “Flow modelling of Strategically Vital Fresh Water Aquifers in Kuwait”
Original Submission Recommendation Major Revision Comments to Author: 1. Title should clarify that the paper mainly deals with flow modeling only and has not addressed the transport of pollutants (hydrocarbons from oil flow and salts from seawater) to any significant extent. The suggested title can be: Flow Modeling of Fresh Water Aquifers in Kuwait. 2. The arrangement of the text in the Abstract and in the Introduction and Regional Setting sections is somewhat incoherent and needs rearrangement. Some parts are unnecessary and should be removed. Not sure whether subheadings within the Abstract are required by the journal; but otherwise unnecessary. Revised drafts of Abstract, Introduction and Regional Setting are provided at the end to assist the authors. 3. The lines 163–168 (p. 7) under Groundwater Pumping History are irrelevant to the reported study and may be omitted. 4. The first sentence (lines 215–216; p. 9) of the last paragraph under Numerical Groundwater Model may be deleted. 5. For steady state simulation a recharge figure of 280.3 mm/year is too precise to be convincing. Rounding up to the nearest ten or even hundred will not affect the result very much and will be more acceptable. 6. A correlation coefficient of 0.91 is indicated in Figure 8 and Line 353 (p. 14) for the correlation between observed and simulated heads of the calibrated steady state model. A figure of 0.95 has, however, been mentioned in Line 338 (p. 13) that should be corrected. 7. It is not very clear how the unsteady state flow modeling has confirmed “that changes in the direction of the groundwater flow are sufficient to partially explain the observed variations in the hydrocarbon concentration and that its biodegradation is active across the whole studied area” (lines 361–363, p. 14). It needs further elaboration, especially with respect to the active nature of biodegradation, as claimed by the authors. 8. Apart from Figure 9, the degree of match between the observed and the simulated heads for the unsteady state model may be presented both in a contour map and in a cross plot as has been done for the steady state model. 9. It has been claimed that MODFLOW-SURFACT code has helped in the simulation of the movement of (recharge) water through the unsaturated zone. No information has, however, been provided on the initial (steady state) and final (unsteady state) distribution of water saturation and pollutants (hydrocarbons and salts) in the unsaturated zone and the conclusions that can be derived from those distributions. In fact, presentation of those results (in the form of maps and/or cross sections) will add uniqueness to the manuscript that will make it worthy of publication in a journal like the Journal of Hydrology. 10. Figure 1 suggests that the Raudhatain fresh water field and the Raudhatain oil field are juxtaposed on each other. On ground, that is not exactly true. There is only partial overlap between the water field and the oil field in the southeastern corner of the Raudhatain fresh water field. In the case of the Umm Al-Aish water field also, the overlap between the water
DOI of the original article:http://dx.doi.org/10.1016/j.ejrh.2016.01.001. 2214-5818/$ – see front matter http://dx.doi.org/10.1016/j.ejrh.2016.11.041
Peer Review Report / Journal of Hydrology: Regional Studies 9 (2017) 26–27
27
field and the oil field (Sabriya) takes place in a small area at the northeastern corner of the water field. The figure should be replaced by one that is more authentic and nearer to the reality. 11. The assumed recharge zones should be highlighted in one of the figures such as Figures 2, 3 or 4, or an additional figure should be added to indicate the recharge zones. 12. The manuscript will need editing for grammar and language. Suggested write-ups for Abstract, Introduction and Regional Setting Abstract Oil flow from the oil wells, damaged during the 1991 Gulf War, and seawater used for extinguishing the resulting oil fire, have contaminated the freshwater aquifers of Raudhatain and Umm Al-Aish water fields in north Kuwait. The numerical flow modeling of the aquifers was undertaken to create a calibrated and validated model that could be used in future to explore a viable remediation strategy for the aquifers. The Environmental Visualization Software Pro, EVS-pro 3-D data presentation program was used to construct a conceptual model as a preliminary step. A 3-D numerical model was developed using the MODFLOW SURFACT code that overcame the limitations of classical MODDFLOW. This model was able to combine both fresh water lenses in one model domain simulating the vadose zone together with the saturated zone. The model domain covered an area of 580 km2 encompassing the Al-Raudhatain and Umm Al-Aish basins. A steady-state model was developed first to study regional flow patterns in the aquifer. A transient model was developed subsequently to assess seasonal recharge on groundwater and investigate their effects on flow patterns. Analysis of the calibrated steady state model output indicated that the model simulated the groundwater elevation and flow direction across the model domain to an acceptable level. Keywords: Groundwater modeling; Gulf war; Groundwater management; Freshwater aquifer 1. Introduction The only two freshwater aquifer lenses in Kuwait, the Al-Raudhatain and Umm Al-Aish, are located in the northern part of the country. The areas belong to the Al Jahra Governorate and are near to the Raudhatain and Sabriyah oil fields, respectively. The lenses occur beneath the topographic depressions associated with the Al-Raudhatain-Umm Al-Aish drainage basin (Figure 1). These freshwater aquifers are unique in that their recharge process reflects the rapid infiltration of surface water runoff and their proximity to the oilfield makes them very vulnerable to contamination. The damage caused from the destruction of oil wells during the Gulf War of 1991 and sea water used to control and extinguish oil fires has directly affected the aquifers (Sadiq and McCain, 1993). The State of Kuwait filed claims in 1995 for compensation with the United Nations Compensation Commission (UNCC) regarding the damages caused by the Iraqi invasion and occupation of Kuwait in 1990. The UNCC awarded funding to Kuwait for the remediation of the Al-Raudhatain and Umm Al-Aish freshwater aquifers (UNCC website, 2014). Numerical modeling of these aquifers has been carried out for this purpose. A conceptual hydrogeological model for the freshwater fields of Al-Raudhatain and Umm Al-Aish has been developed first and this has been used to construct a steady and subsequently, a transient groundwater flow model. The model can be used in the future to identify the best feasible approach for the remediation of the damaged freshwater aquifers in these areas. 2. Regional setting The State of Kuwait is located at the north western side of the Arabian Gulf and occupies an area of about 18,000 km2. It is an arid country, home to over 3.4 million people, and is characterized by long summers with extremely high temperatures and high humidity, short mild winters with low humidity, and high evaporation rates. Temperature often exceeds 50 ◦ C in the summer and the long term mean annual rainfall is about 121 mm/year with a mean annual potential evaporation of about 2600 mm/year (FAO, Aquastat, 2013). The bulk of Kuwait’s groundwater is brackish (Omar et al., 1981). As already mentioned, fresh groundwater (total dissolved solid of 350 to 1000 mg/L) reserves are limited in volume and confined in Al-Raudhatain and Umm Al-Aish areas in the northern parts of the country. Anonymous
Contents lists available at ScienceDirect
Journal of Hydrology: Regional Studies journal homepage: www.elsevier.com/locate/ejrh
Peer Review Report
Peer review report 1 on “Flow modelling of Strategically Vital Fresh Water Aquifers in Kuwait”
Original Submission Recommendation Major Revision Comments to Author: 1. Title should clarify that the paper mainly deals with flow modeling only and has not addressed the transport of pollutants (hydrocarbons from oil flow and salts from seawater) to any significant extent. The suggested title can be: Flow Modeling of Fresh Water Aquifers in Kuwait. 2. The arrangement of the text in the Abstract and in the Introduction and Regional Setting sections is somewhat incoherent and needs rearrangement. Some parts are unnecessary and should be removed. Not sure whether subheadings within the Abstract are required by the journal; but otherwise unnecessary. Revised drafts of Abstract, Introduction and Regional Setting are provided at the end to assist the authors. 3. The lines 163–168 (p. 7) under Groundwater Pumping History are irrelevant to the reported study and may be omitted. 4. The first sentence (lines 215–216; p. 9) of the last paragraph under Numerical Groundwater Model may be deleted. 5. For steady state simulation a recharge figure of 280.3 mm/year is too precise to be convincing. Rounding up to the nearest ten or even hundred will not affect the result very much and will be more acceptable. 6. A correlation coefficient of 0.91 is indicated in Figure 8 and Line 353 (p. 14) for the correlation between observed and simulated heads of the calibrated steady state model. A figure of 0.95 has, however, been mentioned in Line 338 (p. 13) that should be corrected. 7. It is not very clear how the unsteady state flow modeling has confirmed “that changes in the direction of the groundwater flow are sufficient to partially explain the observed variations in the hydrocarbon concentration and that its biodegradation is active across the whole studied area” (lines 361–363, p. 14). It needs further elaboration, especially with respect to the active nature of biodegradation, as claimed by the authors. 8. Apart from Figure 9, the degree of match between the observed and the simulated heads for the unsteady state model may be presented both in a contour map and in a cross plot as has been done for the steady state model. 9. It has been claimed that MODFLOW-SURFACT code has helped in the simulation of the movement of (recharge) water through the unsaturated zone. No information has, however, been provided on the initial (steady state) and final (unsteady state) distribution of water saturation and pollutants (hydrocarbons and salts) in the unsaturated zone and the conclusions that can be derived from those distributions. In fact, presentation of those results (in the form of maps and/or cross sections) will add uniqueness to the manuscript that will make it worthy of publication in a journal like the Journal of Hydrology. 10. Figure 1 suggests that the Raudhatain fresh water field and the Raudhatain oil field are juxtaposed on each other. On ground, that is not exactly true. There is only partial overlap between the water field and the oil field in the southeastern corner of the Raudhatain fresh water field. In the case of the Umm Al-Aish water field also, the overlap between the water
DOI of the original article:http://dx.doi.org/10.1016/j.ejrh.2016.01.001. 2214-5818/$ – see front matter http://dx.doi.org/10.1016/j.ejrh.2016.11.041
Peer Review Report / Journal of Hydrology: Regional Studies 9 (2017) 26–27
27
field and the oil field (Sabriya) takes place in a small area at the northeastern corner of the water field. The figure should be replaced by one that is more authentic and nearer to the reality. 11. The assumed recharge zones should be highlighted in one of the figures such as Figures 2, 3 or 4, or an additional figure should be added to indicate the recharge zones. 12. The manuscript will need editing for grammar and language. Suggested write-ups for Abstract, Introduction and Regional Setting Abstract Oil flow from the oil wells, damaged during the 1991 Gulf War, and seawater used for extinguishing the resulting oil fire, have contaminated the freshwater aquifers of Raudhatain and Umm Al-Aish water fields in north Kuwait. The numerical flow modeling of the aquifers was undertaken to create a calibrated and validated model that could be used in future to explore a viable remediation strategy for the aquifers. The Environmental Visualization Software Pro, EVS-pro 3-D data presentation program was used to construct a conceptual model as a preliminary step. A 3-D numerical model was developed using the MODFLOW SURFACT code that overcame the limitations of classical MODDFLOW. This model was able to combine both fresh water lenses in one model domain simulating the vadose zone together with the saturated zone. The model domain covered an area of 580 km2 encompassing the Al-Raudhatain and Umm Al-Aish basins. A steady-state model was developed first to study regional flow patterns in the aquifer. A transient model was developed subsequently to assess seasonal recharge on groundwater and investigate their effects on flow patterns. Analysis of the calibrated steady state model output indicated that the model simulated the groundwater elevation and flow direction across the model domain to an acceptable level. Keywords: Groundwater modeling; Gulf war; Groundwater management; Freshwater aquifer 1. Introduction The only two freshwater aquifer lenses in Kuwait, the Al-Raudhatain and Umm Al-Aish, are located in the northern part of the country. The areas belong to the Al Jahra Governorate and are near to the Raudhatain and Sabriyah oil fields, respectively. The lenses occur beneath the topographic depressions associated with the Al-Raudhatain-Umm Al-Aish drainage basin (Figure 1). These freshwater aquifers are unique in that their recharge process reflects the rapid infiltration of surface water runoff and their proximity to the oilfield makes them very vulnerable to contamination. The damage caused from the destruction of oil wells during the Gulf War of 1991 and sea water used to control and extinguish oil fires has directly affected the aquifers (Sadiq and McCain, 1993). The State of Kuwait filed claims in 1995 for compensation with the United Nations Compensation Commission (UNCC) regarding the damages caused by the Iraqi invasion and occupation of Kuwait in 1990. The UNCC awarded funding to Kuwait for the remediation of the Al-Raudhatain and Umm Al-Aish freshwater aquifers (UNCC website, 2014). Numerical modeling of these aquifers has been carried out for this purpose. A conceptual hydrogeological model for the freshwater fields of Al-Raudhatain and Umm Al-Aish has been developed first and this has been used to construct a steady and subsequently, a transient groundwater flow model. The model can be used in the future to identify the best feasible approach for the remediation of the damaged freshwater aquifers in these areas. 2. Regional setting The State of Kuwait is located at the north western side of the Arabian Gulf and occupies an area of about 18,000 km2. It is an arid country, home to over 3.4 million people, and is characterized by long summers with extremely high temperatures and high humidity, short mild winters with low humidity, and high evaporation rates. Temperature often exceeds 50 ◦ C in the summer and the long term mean annual rainfall is about 121 mm/year with a mean annual potential evaporation of about 2600 mm/year (FAO, Aquastat, 2013). The bulk of Kuwait’s groundwater is brackish (Omar et al., 1981). As already mentioned, fresh groundwater (total dissolved solid of 350 to 1000 mg/L) reserves are limited in volume and confined in Al-Raudhatain and Umm Al-Aish areas in the northern parts of the country. Anonymous