Beatrice Maria Sole Giambastiani

The Importance of Data Acquisition Techniques in Saltwater Intrusion Monitoring

A detailed vertical characterization of a coastal aquifer was performed along a flow path to monitor the seawater intrusion. Physico-chemical logs were obtained by both open-borehole logging (OBL) and multilevel sampling technique (MLS) via straddle packers in piezometers penetrating the coastal aquifer of the Po River Delta, Italy. The open borehole logs led to a satisfactory reconstruction of the extent of the fresh-saltwater interface but provided a misleading characterization of the distribution of redox environments within the aquifer. On the contrary, good fits between sedimentological, stratigraphycal and physico-chemical data were obtained using the straddle packers devices. This study demonstrates that, within coastal shallow aquifers evenly recharged by irrigation canals, the simple and economical OBL technique can lead to misleading results when used to characterize density dependent groundwater stratification but is deemed adequate for preliminary assessments of the saltwater wedge location.

Training Images from Process-Imitating Methods

The lack of a suitable training image is one of the main limitations of the application of multiple-point statistics (MPS) for the characterization of heterogeneity in real case studies. Process-imitating facies modeling techniques can potentially provide training images. However, the parameterization of these process-imitating techniques is not straightforward. Moreover, reproducing the resulting heterogeneous patterns with standard MPS can be challenging. Here the statistical properties of the paleoclimatic data set are used to select the best parameter sets for the process-imitating methods. The data set is composed of 278 lithological logs drilled in the lower Namoi catchment, New South Wales, Australia. A good understanding of the hydrogeological connectivity of this aquifer is needed to tackle groundwater management issues. The spatial variability of the facies within the lithological logs and calculated models is measured using fractal dimension, transition probability, and vertical facies proportion. To accommodate the vertical proportions trend of the data set, four different training images are simulated. The grain size is simulated alongside the lithological codes and used as an auxiliary variable in the direct sampling implementation of MPS. In this way, one can obtain conditional MPS simulations that preserve the quality and the realism of the training images simulated with the process-imitating method. The main outcome of this study is the possibility of obtaining MPS simulations that respect the statistical properties observed in the real data set and honor the observed conditioning data, while preserving the complex heterogeneity generated by the process-imitating method. In addition, it is demonstrated that an equilibrium of good fit among all the statistical properties of the data set should be considered when selecting a suitable set of parameters for the process-imitating simulations.

A reassessment of the Lower Namoi Catchment aquifer architecture and hydraulic connectivity with reference to climate drivers

We demonstrate the need for better representations of aquifer architecture to understand hydraulic connectivity and manage groundwater allocations for the ∼140 m-thick alluvial sequences in the Lower Namoi Catchment, Australia. In the 1980s, an analysis of palynological and groundwater hydrograph data resulted in a simple three-layer stratigraphic/hydrostratigraphic representation for the aquifer system, consisting of an unconfined aquifer overlying two semi-confined aquifers. We present an analysis of 278 borehole lithological logs within the catchment and show that the stratigraphy is far more complex. The architectural features and the net-to-gross line-plot of the valley-filling sequence are best represented by a distributive fluvial system, where the avulsion frequency increases at a slower rate than the aggradation rate. We also show that an improved understanding of past climates contextualises the architectural features observable in the valley-filling sequence, and that the lithofacies distribution captures information about the impact of climate change during the Neogene and Quaternary. We demonstrate the correlation between climate and the vertical lithological succession by correlating the sediment net-to-gross ratio line-plot with the marine benthic oxygen isotope line-plot – a climate change proxy. Pollens indicate that there was a transition from a relatively wet climate in the mid–late Miocene to a drier climate in the Pleistocene, with a continuing drying trend until present. Groundwater is currently extracted from the sand and gravel belts associated with the high-energy wetter climate. However, some of these channel belts are disconnected from the modern river and flood zone. We show that the cutoff between the hydraulically well- and poorly connected portions of the valley-filling sequence matches the connectivity threshold expected from a fluvial system.

Coastal aquifer response to extreme storm events in Emilia‐Romagna, Italy

With global warming and sea level rise, many coastal systems will experience increased levels of inundation and storm flooding, especially along sandy lowland coastal areas, such as the Northern Adriatic coast (Italy). Understanding how extreme events may directly affect groundwater hydrology in shallow unconfined coastal aquifers is important to assess coastal vulnerability and quantifying freshwater resources. This study investigates shallow coastal aquifer response to storm events. The transitory and permanent effects of storm waves is evaluated through the real time monitoring of groundwater and soil parameters, in order to characterize both the saturated and unsaturated portions of the coastal aquifer of Ravenna and Ferrara (southern Po Delta, Italy). Results highlight a general increase in hydraulic head and soil moisture, along with a decrease in groundwater salinity and pore water salinity due to rainfall infiltration during the 2 days storm event. The only exceptions are represented by the observation wells in proximity to the coastline (within 100 m), which recorded a temporary increase in soil and water salinity caused by the exceptional high waves, which persist on top of the dune crest during the storm event. This generates a saline plume that infiltrates through the vadose zone down to the saturated portion of the aquifer causing a temporary disappearance of the freshwater lens generally present, although limited in size, below the coastal dunes. Despite the high hydraulic conductivity, the aquifer system does not quickly recover the pre-storm equilibrium and the storm effects are evident in groundwater and soil parameters after 10 days past the storm overwash recess.

Forest fire effects on groundwater in a coastal aquifer (Ravenna, Italy)

BiGeA—Department of Biological, Geological and Environmental Sciences, University of Bologna, Ravenna, Italy CIRI EA—Interdepartmental Centre for Industrial Research on Energy and Environment, University of Bologna, Ravenna, Italy Carabinieri for Biodiversity, Punta Marina, Ravenna, Italy Correspondence Nicolas Greggio, CIRI EA—Interdepartmental Centre for Industrial Research on Energy and Environment, University of Bologna, 48123 Ravenna, Italy. Email: nicolas.greggio2@unibo.it Funding information Flaminia Foundation

Monitoring heat transfer from a groundwater heat exchanger in a large tank model

A large tank (4x8x1.4 m), equipped with 26 standard piezometers and six temperature loggers with four channels each installed at different depth, is used to carry out thermal monitoring test and investigate environmental impact of heat borehole exchange. Loamy sediments (35 m3), used to fill the tank, were excavated from an unconfined alluvial aquifer near Ferrara (Northern Italy). To evaluate spatial heterogeneity, the tank’s filling material was characterized via slug tests and grain size distribution analysis. Constant heat input rate test was conducted by originating a heat plume using a groundwater heat exchanger (GHE). Temperature was monitored in continuous via data loggers. The effect of heat borehole exchange was small compared with the temperature applied. Results show a heat flux dominated by temperature gradient and thermal conduction. The effect of hydraulic conductivity heterogeneity on heat plume development is discussed. Tank model presented in this research looks to be suitable for heat transport modeling. Recommendations for future development of the research and future groundwater and heat transport modeling are also reported.