| 30 Jun 2025
Crop salinization by intense pumping in regional discharge areas of an inland aquifer system (Cenozoic Duero basin aquifer, Spain)
Abstract. Salinization of crops irrigated with groundwaters in the Tordesillas area has been investigated to determine its cause. Hydrogeological, geophysical, and geochemical techniques reveal that regional saline groundwater flows through the Cenozoic aquifer system of the Duero Basin discharge into the Tordesillas area. Groundwater salinity increases below 150–200 depth. TDEM profiles indicate that salinity distribution is influenced by local and regional flow mixing, as well as by fault structures affecting the Cenozoic succession. Isotopic analyses (δ18O, δD, δ34S) suggest multiple sources of dissolved sulphate and evidence that regional groundwaters recharged at higher altitudes and/or lower temperatures.
Irrigation return flows do not noticeably contribute to salinization, as δ18O and δD data from boreholes in the Duero Floodplain do not show an evaporation trend. Instead, intensive groundwater pumping (from boreholes in the Duero River floodplain), particularly during the irrigation season, induces upwelling of saline groundwater. Piezometric records indicate that hydraulic potential at intermediate depths (about 100 m depth) decreases during pumping (summer), facilitating upwelling of deeper saline groundwaters. Salinity profiles confirm this process, demonstrating a shift from fresher to more saline conditions over time.
Groundwater management authorities must address this issue to prevent further salinization. These findings provide crucial insights for optimizing well design and identifying depths where groundwater is unsuitable for irrigation, ensuring sustainable water use in the region.
Unfortunately, this paper is not suitable for publication in an international journal such as HESS. It has no novel aspects and would not be of interest to the broader academic community. The conclusions are reasonable, but the main finding that groundwater pumping causes changes to aquifer salinities is not unexpected and not novel. In its present form it is more suited to a regional journal. Case studies are certainly acceptable in the international literature, but they need to add to our general understanding; so, indications of what new ideas come out of a study and what researchers working on similar projects elsewhere can take from it are needed.
The limited and parochial scope of the paper is evident in the Introduction, which is focused on the local issue of crop yields being impacted by salinization. Salinization of water resources is a major problem globally, but there is no effort here to review the global understanding or to put this study into a broader context. The Aims are also very specific to understanding the local hydrogeology and the Conclusions are just a restatement of the specific findings of the research with no indication of how or why this research is of general interest. Even within the local context, the end of the paper is underwhelming with a general suggestion that these data should help management (without specifying how).
There are several issues with the data and its interpretation.
I have not gone through the paper in more detail, as I cannot see that the data can be woven into a story that is of sufficient interest for this journal. It is never pleasant to receive negative reviews, but I would encourage the authors to see if they can bring more rigor to the study and consider how generally interesting / novel this work is, which will dictate where it should be submitted.