Meteorological Variability and Groundwater Quality: Examples in Different Hydrogeological Settings

Abstract

Rainfall and temperature variability causes changes in groundwater recharge that can also influence groundwater quality by different processes. The aim of this study is the analysis of the hydrogeochemical variations over time due to meteorological variability in two different study areas in Italy: an alluvial aquifer in the Piedmont Po plain and an alluvial-pyroclastic aquifer in the Campanian plain. The examined plains show groundwater with natural quality not satisfying the European drinking water standards, or anthropogenic contamination. The peculiar natural quality is due, in the Campanian plain, to the closeness of volcanic areas, and to the presence of reducing conditions. In Piedmont plain a test site is characterized by a point-source contamination by heavy metals, due to the presence of past industrial activities. In all the examined areas there is a diffuse nitrate contamination. The fluctuations of the ions As, F, Fe, Mn, Cr VI, NO3, and Cl were analyzed and compared, using statistical methods, with the variations over time in precipitation, temperature, and piezometric levels, sometimes significant. Results highlight the importance of the groundwater and meteorological monitoring and the key role of the recharge variation in the hydrogeochemical processes. The linking degree between rainfall/temperature variability and hydrogeochemistry is variable, in function of the typology of chemical species, their origin, and of the aquifer characteristics. The fluctuation of climate variables determines sudden changes in the geochemistry of shallow unconfined aquifers (e.g., in the Piedmont plain), while semiconfined or confined aquifers (e.g., in the Volturno-Regi Lagni plain) react with a greater delay to these variations. Moreover, natural quality is more affected by climatic variations than anthropogenic contamination, which is the result of multiple environmental and anthropic factors.

Groundwater quality trend and trend reversal assessment in the European Water Framework Directive context: an example with nitrates in Italy

“…Further, variations in the land use or in water management practices might result in upward trends related to impacts happened in the past and this could be difficult to distinguish without an appropriate knowledge of the groundwater body recent history. Finally, even the ongoing climatic variations could act on pollutants concentration and transport in the subsurface, eventually modifying actual trends (Lasagna et al 2020 ). Further checks, applying also different methods (such as groundwater dating, deterministic flow and transport modelling), are always recommended.…”

“…Applying this concept to groundwater chemical time series, the null hypothesis is whether there is no significant monotonic trend of a pollutant. The Mann-Kendall test (Mann 1945;Kendall 1975) is a very popular one, used to statistically assess whether there is a monotonic upward or downward trend over time. It is a nonparametric test; hence, it does not require assumptions about the probability distribution of the dataset, and it is commonly used for the statistical treatment of environmental data (Ducci et al 2019;Helsel and Frans 2006;Urresti-Estala et al 2016;Zhang et al 2006).…”

“…This is a key point, as in these situations one has to deal with a limited number of temporal observations (< 40 annual data). For this reason, the S statistics from Hollander et al 2014; Hollander and Wolfe (1973) and Kendall (1975) for the one-tail test was implemented in a spreadsheet (described in Appendix A and provided as supplementary material).…”

Groundwater Resources Assessment for Sustainable Development in South Sudan

“…An interesting approach to investigate this topic is the analysis of the water resource potential; after the selection of a number of target stations, the study should provide an estimation of rainfall amount on average over the last 30 years and a comparison of rainfall data and survey campaign outputs. The results would show whether the climate change affected the groundwater, with a quantitative evaluation of the entity of this influence on both availability and quality of the water resource [31,32].…”

Hydrochemical and Isotopic Applications in the Western Aosta Valley (Italy) for Sustainable Groundwater Management

“…Water and groundwater availability are seriously affected by pollution, overexploitation and climate change [1][2][3][4][5]. As stated by the EU Water Framework Directive 2000/60, water protection must be a priority for each European country, and continuous monitoring is recommended to avoid serious contamination events and overexploitation of water resources.…”