Closing a scale-gap in Earth observation using regional-scale airborne geophysics in the lower Mississippi Valley

<p>Critical groundwater resources and hidden seismic hazards underly much of the Mississippi Alluvial Plain. Spanning nearly 100,000 square kilometers across seven states, this region hosts one of the most prolific shallow aquifer systems in the United States that supports a $12 billion agricultural economy amidst chronic groundwater decline. Further, underlying fault structures of the Reelfoot Rift and New Madrid Seismic Zone represent an important and poorly understood hazard with a complex pattern of historical impacts. Despite its societal and economic importance, mapping of shallow subsurface architecture with spatial resolution needed for effective management is insufficient. Here, we report the results of 40,000 flight-line-kilometers of electromagnetic, magnetic, and radiometric data collectively providing a system-scale snapshot of an entire aquifer system, the first such effort in the United States. This survey enables new understanding of the regional hydrogeology while also revealing previously unseen large vertical displacements (exceeding 50 m) in the uppermost Tertiary units within the New Madrid Seismic Zone.</p>

Karst water resources and their complex utilization in the Bükk Mountains, northeast Hungary: an assessment from a regional hydrogeological perspective

The cold and thermal karst water resources of the Bükk Mountains play a significant role in the hydrogeological setting of northeastern Hungary. Although there is much geological and hydrogeological information available, the regional hydrogeology of the Bükk Mountains had not been described in a standalone study involving all this information. The drinking water supply of the city of Miskolc and some other neighboring cities is based on the cold karst water resources of the Bükk Mountains. The thermal water resources have been getting more important, in terms of balneology and geothermal energy production, in this region over the last decade. An evaluation of the measurements of a 27-year-old groundwater quantity and quality monitoring system was performed. As a result, several types of new field hydrogeology, meteorology and spring discharge measurements were added to the monitoring scheme to provide information for studying the tendencies connected to extreme weather conditions. This will help to achieve sustainable utilization of the karst water resources. The main conclusions drawn in this study underline the importance of the strict measures associated with the water management of the Bükk Mountains because of the limited natural recharge and the continuously increasing demands on the cold and thermal water resources. A success story is found in Miskolc, which demonstrates the sustainable utilization of the deep thermal karst water; Miskolc hosts the largest geothermal heating plant in Central Europe with 60 MWt capacity.

A New Perspective to Explore the Hydraulic Connectivity of Karst Aquifer System in Jinan Spring Catchment, China

Investigating the hydraulic connectivity of a complex karst aquifer system is an important research topic for sustainable operation and optimization layout of karst groundwater exploitation and recharge. However, the identification of preferential sites of recharge and exploitation is usually subject to regional hydrogeology conditions and the mechanisms of recharge and exploitation. The conventional research methods of hydraulic connectivity often have some limitations. In this study, we developed an improved grey amplitude relation model to explore the hydraulic connectivity in Jinan spring catchment and presented a quantized evaluation index water table fluctuation relation degree (WTFRD) using karst groundwater table data in Western Jinan and Jinan spring groups from 2014 to 2017. Results showed that the total WTFRD was 0.854 between Western Jinan and Jinan spring groups when the external distraction for karst groundwater table was the smallest, which was in high relation degree grade. Meanwhile, the change rules of karst groundwater table in the two sites were basically the same. Accordingly, a high connectivity occurred between the two karst aquifers from a statistical perspective, and further illustrated that Western Jinan could be selected as preferential experiment sites. A comprehensive case in Jinan spring catchment indicated that the WTFRD provided a preliminary idea to investigate hydraulic connectivity quantitatively. This method could be considered as a pre-study of the conventional experiments to form a high-efficiency and low-cost combined method, which has great potential and merits further study.

Secondary rock structures and the regional hydrogeology of claystone-rich cretaceous strata, Williston Basin, Saskatchewan, Canada

The geometry and spatial distribution of a polygonal fault system (PFS) and collapse features within Cretaceous strata (predominantly mudstones and claystones) were investigated using three high-resolution three-dimensional seismic datasets of the Williston Basin, Saskatchewan, Canada. Mapping of the planform geometry and fault throw distributions (throw–depth (T–z) profiling) shows that the PFS present in the Colorado Group and Pierre Fm has a vertical extent of 200–330 m. Variation in the lateral planform geometry is attributed to the relative rates of stress accumulation during early development of the planar faults and is constrained using sequence stratigraphic principles. The mean fault dip is 60° ± 12° (number of measurements, n = 225). The T–z profiles appear as partial C-type profiles, demonstrating that at least half of the total height of the PFS was removed during post-Cretaceous erosion. The presence of polygonal faults in equivalent strata of the Western Interior Sedimentary Basin (WISB) suggests the PFS described in the current study (1510 km2) may be present across the WISB. Collapse features, formed in response to dissolution cavities within underlying strata, crosscut the entire Cretaceous sequence and are subcircular in plan view with typical diameters of 350–450 m. These features are present in each of the datasets at a rate of 0.02–0.11 collapses/km2. The prevalence of collapses in areas where faults display modified throw distributions may suggest post-Cretaceous fault reactivation associated with Pleistocene glacial periods. Although these secondary rock structures likely affect groundwater and solute transport at the basin scale, the impact remains to be determined.

CARACTERIZAÇÃO DE PROCESSOS HIDROGEOQUÍMICOS EM ÁGUAS SUBTERRÂNEAS DO SISTEMA AQUÍFERO SANTA MARIA, NA REGIÃO CENTRAL DO RIO GRANDE DO SUL

A study was carried out of the hydrogeochemical processes involving the groundwater of the western portion of the Santa Maria Aquifer System (SMAS) in the central region of Rio Grande do Sul. The objective of this study was to characterize the behavior of a portion of the groundwater between São Pedro do Sul, Santa Maria and Restinga Seca municipalities, based on a model between water/rock interaction. Mineralogical and hydrochemical information were analyzed, aiming to model the hydrogeochemical evolution of the aquifer in these municipalities. For this purpose, a processing of the information in a geochemical modeling code was performed, using as previous reference mineralogical studies. The results pointed out the main geochemical interactions responsible for groundwater chemistry, which is strongly dependent of the chemical composition of the recharge waters and the mineralogical contribution of the sedimentary rocks of this aquifer system. The groundwater saturation states showed subsaturation processes tending to the balance of carbonate minerals, indicating the dissolution of these minerals, mainly calcite, as well as supersaturation of clay-minerals ilite, montmorillonite (smectite) and kaolinite, in both cases tending to the alkalinization of the environment. The characterization of the hydrogeochemical properties of aquifers is important for a correct understanding of the processes that occur in it and dominate the regional hydrogeology.