Response to Dr. YongCheol Kim

Abstract

Managed aquifer recharge (MAR) can be affected by many risks. Those risks are related to different technical and non-technical aspects of recharge, like water availability, water quality, legislation, social issues, etc. Many other works have acknowledged risks of this nature theoretically; however, their quantification and definition has not been developed. In this study, the risk definition and quantification has been performed by means of "fault trees" and probabilistic risk assessment (PRA). We defined a fault tree with 65 basic events applicable to the operation phase. After that, we have applied this methodology to six different managed aquifer recharge sites located in the Mediterranean Basin (Portugal, Spain, Italy, Malta, and Israel). The probabilities of the basic events were defined by expert criteria, based on the knowledge of the different managers of the facilities. From that, we conclude that in all sites, the perception of the expert criteria of the non-technical aspects were as much or even more important than the technical aspects. Regarding the risk results, we observe that the total risk in three of the six sites was equal to or above 0.90. That would mean that the MAR facilities have a risk of failure equal to or higher than 90 % in the period of 2-6 years. The other three sites presented lower risks (75, 29, and 18 % for Malta, Menashe, and Serchio, respectively). Published by Copernicus Publications on behalf of the European Geosciences Union. P. Rodriguez-Escales et al.: A risk assessment methodology in MAR 10 %, with a larger decrease in summer and in the southern areas (Pachauri et al., 2014). At the same time, large water quantities are lost to the Mediterranean Sea as surface runoff and discharges from rivers, treated and untreated wastewater, or excess water from various sources during periods of low demand. These alternative water sources can potentially help to increase water availability, both in general terms and in periods of high demand, therefore improving water security. The main factors hindering the effective use of such waters are related to concerns about water quality and the lack of sufficient low-cost intermediate storage options. In principal, large storage capacity is available in shallow aquifers, mostly in thick unsaturated zones or in already depleted overexploited aquifers. Managed aquifer recharge (MAR) takes advantage of this available storage. MAR is defined as the intentional infiltration of water into aquifers with the purpose of either later recovering that water for different uses (agricultural, industrial, or urban) or obtaining an environmental benefit (Dillon et al., 2009). MAR includes a range of recharge options (surface or subsurface) and water sources (natural, reclaimed, or desalinated) (