Hydraulic Connection Research Articles

Applying Electrical Resistivity Tomography and Biological Methods to Assess the Hyporheic Zone Water Exchanges in Two Mediterranean Stream Reaches

The hyporheic zone (HZ) is a critical area of all river ecosystems. It is the area beneath the stream and adjacent to the stream, where the surface water and groundwater are mixed. The HZ extends both vertically and laterally depending on the sediment configuration, namely their porosity and permeability. This influences the hyporheic communities’ structural pattern and their active dispersal among distinct rivers compartments and alluvial aquifers. It is still difficult to assess the spatial extent of the HZ and the distribution of the mixing zones. This study applies time-lapse images obtained using electrical resistivity tomography (ERT) of 20 m wide and 5 m deep alluvial streams, with regards to the structural pattern of hyporheic communities represented by cyclopoids and ostracods, in order to assess the extent of the HZ in the riverbed and the parafluvial sediment configurations. The ERT images obtained at the hyporheic Site 1 are characterized by alluvial deposits dominated by coarse and very coarse sands with resistivity values ranging from ~20 to 80 Ohm.m, indicating a permeable zone up to ~0.5 m thick and extending laterally for ca. 5 m from the channel and associated with the hyporheic zone. The sediment configurations, texture, and structure indicate an active surface–hyporheic water exchange and low water retention into the sediments. This is also indicated by the hyporheic copepods and ostracods communities’ structure formed by a mixture of non-stygobites (five species) and stygobites (two species). A low-resistivity (<70 Ohm.m) permeable zone located 2.3 m below the streambed and unconnected with the river channel was also detected and associated with the associated alluvial aquifer. In contrast, the resistivity image at Site 2 dominated by coarse, medium, and very fine sands, shows a low-permeability zone in the upper ~0.5 m of the profile, with a resistivity value ranging from ~45 to 80 Ohm.m, indicating a reduced HZ extension in both vertical and lateral dimensions. Here the sediment configurations indicate that the water retention and interaction with the sediment is higher, reflected by more diverse hyporheic communities and with highly abundant stygobite species. The two examples show that non-invasive ERT images and biological assessments provide complementary and valuable information about the characterization of the sub-channel architecture and its potential hydraulic connection to the floodplain aquifer.

Microscopic investigation of the influence of complex stress states on internal erosion and its impacts on critical hydraulic gradients

AbstractInternal erosion involves the loss of fine particles within the matrix of coarse particles under seepage flow, posing a severe threat to hydraulic structures. This paper focuses on internal erosion considering anisotropic stress conditions. The influence of the anisotropic stress state, represented by vertical stress equal to, bigger than, or smaller than horizontal stress, was investigated using coupled computational fluid dynamics (CFD) and the discrete element method (DEM). Results show that the loss of fine particle specimens under anisotropic stress conditions is greater than that for samples under isotropic stress states, as the loss of fine particles leads to an evolution of anisotropy into isotropy, with local contact force chains gradually forming spatially isotropic structures. The strong force chains of specimens under triaxial compression were also found to develop a dominant orientation in the vertical direction, leading to clogging in the upward migration of fine particles and increasing the critical hydraulic gradient. In addition, the evolution of void ratio, hydraulic drag force, connectivity, and coordination number has also been analyzed to exhibit the influence of stress anisotropy on internal erosion.

Combined use of statistical Bayesian model and strontium isotopes deciphering the high complexity groundwater flow in the Guarani Aquifer System (GAS)

The Guarani Aquifer System (GAS) is one of the most important groundwater reservoirs in Latin America. Even though its geological aspects and hydraulic behavior are deeply studied, questions regarding hydraulic connections between the GAS and the overlying (SGAS) and underlying (PRE-GAS) aquifers within the Paraná Sedimentary Basin geological framework are recently being pursued. This paper presents a new tracer approach within the GAS, incorporating strontium isotopes in a statistical Bayesian model. The multi-pronged approach is used to quantify mixing proportions and identify different processes related to water-rock interaction and hydrochemical data. Strontium isotopic ratio ranged from enriched values (>0.711) associated with higher GAS groundwater contribution, to lower values associated with contribution from the SGAS (∼0.707) and PRE-GAS (∼0.709) units, as well as isotopic fingerprint associated with direct rainwater recharge. As groundwater flows through the GAS, the mixing proportions between the end-members changes along with the hydrogeochemical evolution. Near recharge zones, GAS represents the dominant source (38% ± 10%), followed by PRE-GAS (28% ± 16%), SGAS (19% ± 11%) and rainwater (14% ± 10%). In transition waters between outcrop and confined areas, the GAS contribution remains dominant (48% ± 9%), followed by PRE-GAS (37% ± 14%) and SGAS (14% ± 8%). In the GAS confined zone, where contributions from rainwater and SGAS is absent, 87Sr/86Sr ratio is more associated with waters from PRE-GAS (53% ± 16%) than from GAS (46% ± 16%). This behavior indicates that groundwater flow in the GAS represent a more complex and vulnerable groundwater mixing system, closely related to the regional geological context of a closed intracratonic basin, than previously understood. The use of strontium isotopes as a hydrogeochemical tracer applied in a statistical mixing model, contributes to a more refined understanding of regional groundwater flow and water origin in the GAS.

Electrical resistivity imaging of an enhanced aquifer recharge site.

Enhanced aquifer recharge (EAR) is defined as any engineered structure or enhanced natural feature designed to convey stormwater, surface water or wastewater directly into an aquifer (e.g. aquifer storage and recovery (ASR) wells) or into the vadose zone eventually percolating to an aquifer (e.g. spreading basins, dry well, etc.; USEPA 2021). Identifying the storage and flow capabilities of complex aquifers can improve the efficacy of many conceptual site models (CSM) for sites considered for ASR projects. In a karst setting, the EAR process may be able to take advantage of natural surficial features and the increased storage capacity of karst aquifers to improve recharge to groundwater. However, the suitability for an EAR project in a karst setting depends on the maturity of the karst and its preceding epikarst. The focus of flow within the epikarst causes enlargement of fractures and karst conduits. Thus, the storage and transmissivity within the karst vary greatly. Electrical resistivity imaging (ERI) is a well-known geophysical tool for mapping fractures and sinkholes, typical in karst settings. Locating enhanced water conveyance structures of a karst aquifer can improve the design and operation of an EAR site. This study investigated the hydraulic connection between shallow and deep groundwater using ERI to identify potential flow pathways and to improve our understanding of the storage mechanisms of the epikarst. The results presented in this paper validate the effectiveness of ERI in characterizing karst/epikarst and delineating soil, bedrock and local faults and fractures in the subsurface.

Deterministic processes shape bacterial community assembly in a karst river across dry and wet seasons.

Karst rivers are particularly vulnerable to bacterial pollution because immigrations are easily diffused from the surrounding environments due to their strong hydraulic connectivity. However, the assembly mechanism in shaping riverine bacterial biogeography is still poorly understood, especially for an ecosystem in the karst area. Here, 16S rRNA genes were used to explore the spatiotemporal and biogeographical patterns of bacterial communities from the Chishui River in the dry and wet seasons, and explore the impact of external immigration on the assembly of water bacterial communities. Our results showed clear spatiotemporal patterns of bacterial communities with a more pronounced seasonal rather than spatial fluctuation, which appeared to be dependent on seasonal-related environmental factors (e.g., temperature and turbidity). The bacterial communities exhibited a significant (p < 0.05) distance–decay pattern in both seasons, and they had a stronger distance–decay relationship in the dry season than in the wet season. However, most of the biomarkers of different external immigrations did not show significant (p > 0.05) distance–decay patterns along the Chishui river, implying that the biomarkers could be used as indicators of external immigration (e.g., OTU_125 and OTU_536). Also, the tributaries were the main external immigration (20.44–83.68%) for the Chishui River, while other terrestrial immigration (e.g., livestock, the soil of the cropland, brewing wastewater treatment plant, and sewages) showed relatively little influence, which could be due to the hydrodynamic conditions (e.g., fragile rock–soil system and hydrological structure) of the karst river. Additionally, the assembly of water bacterial communities in the Chishui river was governed by more determinism (50.7–85.7%) than stochasticity (14.3–49.3%) in both the dry and wet seasons. We demonstrated that the bacterial community’s substantial variations are largely shaped by deterministic processes, thereby providing a better understanding of spatiotemporal patterns and mechanisms of the bacterial community in karst river waters.

Soil surface connectivity of tilled soil with wheel tracks and its development under simulated rainfall

• Linkage between soil surface microrelief and overland flow was examined. • Differently oriented wheel tracks served as water flow paths or as sediment sinks. • Increase of surface connectivity after a rain was shown by functional connectivity. • Structural connectivity showed reorganization of the surface runoff pathways. Although wheel tracks cover only a small portion of the surface of agricultural fields, their effect on surface runoff and sediment transport is substantial. Wheel tracks change the microrelief of the soil surface, and influence how the surface is further altered by rainfall and runoff. This study presents a plot-scale microrelief analysis of a tilled surface with wheel tracks under simulated rainfall. Digital elevation models of the microrelief with 1 cm spatial resolution were obtained using the Structure from Motion method. The random roughness, the structural connectivity, and functional connectivity were calculated for before-rainfall and after-rainfall soil surface conditions. The experiments were carried out on inclined, freshly-tilled plots (8 m long, 2 m wide). The wheel tracks were created by four passages of machinery in the slope direction (SWT) and in the contour-line direction (CWT). The experiments were compared to reference plots without wheel tracks (NWT). The wheel tracks increase water and sediment connectivity if they are oriented in slope-wise direction. Microrelief analysis shows that SWT drains water from the surrounding soil. The soil surface adjacent to SWT can also become more connected with the wheel track, due to changes in microrelief introduced by rainfall and runoff. The calculated higher connectivity in the SWT plot corresponded to the measured increased sediment loads. This suggests faster overland flow and therefore shorter flow pathways on the soil surface microrelief. CWT leads to a decrease in the water and sediment connectivity compared to the NWT and SWT plots. Although the surface runoff can overflow the CWT, the network of flow paths results in decreased flow velocity and a slower sediment transport rate. However, the CWT effect is not permanent, and declines as the wheel tracks become silted with the deposited sediment. It is shown that detailed microrelief data provide relevant information for a study of the changes in flow routing in a tilled agricultural field with the presence of a wheel track. SWT accelerates the runoff and especially the sediment transport. During a rainfall event, the hydraulic connection between the wheel track and the surrounding soil increases dramatically. CWT reduces the surface runoff and also the sediment transport. In the long term, rainfall events and surface runoff alter the microrelief connectivity, causing the soil surface to be more hydraulically connected, irrespective of the wheel track orientation. This study demonstrates the effect of wheel tracks on water and sediment transport. The results draw attention to the importance of appropriate soil protection measures, as a bare unprotected surface microrelief exposed to rainfall leads to increased sediment connectivity.

Hydrogeochemical Processes and Connection of Multi-Layer Groundwater System in Sunan Mining Area, Eastern China.

Groundwater is an important freshwater resource in the world and serves as the main source of water for mining areas in Northern China. Coal mining may cause changes in water quality. As such, to identify ways to prevent water contamination, this study investigates the hydrogeochemical processes and transport paths of a complex aquifer system in the Sunan mining area in Northern China. Using the APFS-MLR model, a geographic information system (GIS) spatial analysis, and a hydrochemical correlation analysis method, this study identifies the potential mineral phases in groundwater, the spatial distribution of mineral reactions, and the contribution rate of these reactions to hydrochemical variables. Inverse modeling is used to verify hydrogeochemical process. The study reveals the relationship between multiple aquifers and four hydrological transport paths. Here, Path 1 and Path 2 show that the Quaternary aquifer, Carboniferous aquifer, and Ordovician aquifer are recharging the Permian aquifer through mineral dissolution and precipitation, cation exchange, and sulfate reduction. On the other hand, Path 3 and Path 4 show that tthe connections of Carboniferous and Ordovician limestone aquifers are dominated by the dissolution and precipitation of minerals and cation exchange, and that they are mainly recharged by the Quaternary aquifer. In the future, the water level of the Permian aquifer may rise somewhat after mining ends, and the mixing of water from the Permian aquifer, Quaternary aquifer, Carboniferous aquifer, and Ordovician aquifer could cause cross-pollution. In addition, sewage produced by human activities may recharge the deep water through the shallow water, polluting the deep karst water. As such, measures should be taken to reduce the hydraulic connection between Permian mine water and karst aquifers. The results of this study may benefit water quality predictions and treatment approaches in other complex multi-layer aquifer areas in the world.

Interactions between sediment microbial fuel cells and voltage loss in series connection in open channels

In the present study, a sediment microbial fuel cell (SMFC) was added to an open channel previously containing another SMFC. Interaction between the two SMFCs was investigated when the new SMFC was located either in downstream or upstream of the former SMFC. Addition of new SMFC in both cases caused a 24–25 % voltage increase in the former SMFC and eliminated initial voltage fluctuations in the new SMFC. Furthermore, voltage loss was studied in two stacked SMFCs operating in open channels, whether both SMFCs operated simultaneously from beginning of operation or added to the channel sequentially. It was observed that in both cases, the SMFC whose anode was used to establish series connection experienced a considerable increase in its anode potential that led to voltage loss in the SMFC. As an example, one of the SMFCs whose anode was connected in series produced an open circuit voltage of 124 mV compared to 716 mV in single mode, although 621 mV was produced when cathode was connected in series. Findings of this study showed the presence of interactions between SMFCs in open channels as well as simultaneous influence of electrical and hydraulic connection on voltage drop within SMFCs.

Study on key technology of identification of mine water inrush source by PSO-LightGBM

Abstract Mine water inrush is a major type of disaster in coal mine production in China. It causes heavy casualties and serious economic losses and threatens coal mine safety. To quickly and accurately identify mine water inrush source, according to the hydrochemical characteristics of different aquifers in the Donghuantuo mining area, this paper systematically analyzes the hydraulic connection of the aquifers in main coal mining areas before and after mining activities. Four types of hydrochemical data were collected: No. 5 coal seam roof water, No. 8 coal seam roof water, No. 122 coal seam floor water, and No. 1214 coal seam aquifer water in the Donghuantuo mining area. In addition, based on the hydrochemical data, the parameter selection of LightGBM was optimized by Particle Swarm Optimization (PSO) and constructed the PSO-LightGBM water inrush source identification model. The recognition accuracy of PSO-LightGBM model was compared with LightGBM model, classification regression tree (CART) model, and random forest (RF) model. The results showed that coal mining activities would have a significant impact on the water quality characteristics of the roof sandstone fissure water of No. 5 coal mine. Mining activities had a certain impact on the accuracy of the identification model. In addition, compared with the four recognition models, PSO-LightGBM model had the highest recognition accuracy of 97.22%. It showed that the model had high accuracy, stability, generalization ability, and important reference value for the identification of mine water inrush source.

Statistical analyses of hydrochemistry in multi-aquifers of the Pansan coalmine, Huainan coalfield, China: implications for water-rock interaction and hydraulic connection

Understanding the groundwater hydrogeochemical processes and aquifer hydraulic connections are essential for effective prevention of water inrush in concealed coal mines. In this study, 40 groundwater samples were collected from the loose layer aquifer (LA), coal measure aquifer (CA), and limestone aquifer (LA) in the Pansan coal mine, Huanan coalfield, China, and the major ion concentrations were analyzed by bivariate diagrams (Na+ + K+ - Cl− versus Ca2+ + Mg2+ - SO42− - HCO3− and CAI-I versus CAI-II), multivariate statistical methods, and receptor model in order to identify the water-rock interactions and aquifer hydraulic connections. Piper diagram showed that groundwater in LA and TA was dominated by the Na–Cl type, while groundwater in CA was mainly of the Na–HCO3 type. Based on the results of bivariate diagrams and PCA/FA, weathering of silicate minerals and cation exchange (source 1), sulfate dissolution (source 2) and chloride dissolution (source 3) were the main processes controlling the groundwater chemistry. Unmix model revealed that the mean contribution of source 1 to CA samples was 74%, while LA and TA samples have higher contributions from evaporite dissolution (source 2 and source 3) relative to CA samples. Moreover, both clustering analysis methods (Q-type hierarchical and K-means cluster) confirmed the existence of a hydraulic connection between LA and TA in the northeastern part of the study area. It is concluded that the application of multivariate statistical analysis to interpret groundwater chemistry can provide useful guidance to prevent water inrush in coal mines.

Aquifer connectivity assessment using stable isotope and hydrochemical analysis in the Raimanuk and its surrounding area on the Timor island

Raimanuk and its surroundings are a potential agricultural area in Indonesia. Sufficient groundwater in this area was a significant factor for supporting agricultural activities and household needs. Therefore, identifying the aquifer connectivity is essential to determine the groundwater utilization pattern in this area. This research aims to determine the aquifer connectivity based on stable isotopes and hydrochemical from the groundwater and the meteoric water (rainwater). The groundwater samples were taken from ten deep wells, six dug wells, and four springs. While the meteoric water samples were taken from four rainfed locations, samples were analyzed using Los Gatos Research DLT-100, Ion Chromatography Metrohm 830IC, and acid-base titration. The result shows there are four groups of groundwater. Group I is the springs that come from local meteoric water. Group II consists of the dug wells that evaporated and showed a relationship to the meteoric water that falls in higher elevations. Group III was the drilled well groundwater from the local flow system. Furthermore, Group IV is the drilled well groundwater with a more enriched δ18O isotope ratio due to water-rock interaction. Even though they are in a different group, there is a hydraulic connection between Group III and IV.

Heat potential of the Upper Jurassic–Lower Cretaceous aquifer in Central Northern Bulgaria: conditions and prospective use

The regional hydrogeological conditions in Northern Bulgaria determine the existence of a large artesian basin consisting of layered aquifers. The groundwater temperature increase with depth and the conditions in the deeper layers are favourable for the formation of stratified hydrothermal reservoirs with potential for heat extraction. Although it was initiated in the 1980s, the utilization of this green energy resource is still in a pre-feasibility phase. The Upper Jurassic–Lower Cretaceous aquifer has the highest yield and it is the most prospective geothermal source in the multi-layered sedimentary complex in Central Northern Bulgaria. This study provides new understanding of the formation and potential for extraction of thermal energy from this stratum, which has all characteristics of a low temperature hydrothermal reservoir. The study includes delineation of its boundaries, evaluation of hydrogeological and thermal parameters and data on hydraulic connectivity. The flow and temperature fields, the elements of the water and heat balance, as well as the groundwater quality, have been assessed. The groundwater and thermal energy resources in the hydrothermal reservoir have been estimated on a regional scale, including a scenario with reinjection. Different options for potential utilization of the thermal energy using reinjection wells have been put forward.

Potential hydraulic connectivity of coal mine aquifers based on statistical analysis of hydrogeochemistry

Mining activities interfere with the natural groundwater chemical environment, which may lead to hydrogeochemical changes of aquifers and mine water inrush disasters. This study analyzed the hydrochemical compositions of 80 water samples in three aquifers and developed a water source identification model to explore the control factors and potential hydraulic connection of groundwater chemistry in a coal mine. The results showed that the hydrochemical types of the three aquifers were different. The main hydrochemical compositions of the loose-layer, coal-bearing, and limestone aquifers were HCO3·Cl–Na, SO4·HCO3–Na, and SO4–Na·Ca, respectively. The correlation, Unmix, and factor analyses showed that the hydrochemical composition of groundwater was controlled by the dissolution of soluble minerals (such as calcite, dolomite, gypsum, and halite) and the weathering of silicate minerals. The factor score plot combined with Q-mode cluster analysis demonstrated no remarkable hydraulic connection among the three aquifers in the study area. The water source identification model effectively identified the source of inrush water. Moreover, the mixing ratio model rationally quantified the contributions of the three aquifers to inrush water.

Analysis of a steady-state model of groundwater discharge in a river valley without and with evapotranspiration

Riparian evapotranspiration is an important process that constrains water exchanges within a well-connected river–aquifer–vegetation hydrological system. In this study, we developed an extended analytical Dupuit–Forchheimer (DF) model to consider the additional water flow resistances due to both the vertical deformation of flow lines caused by evapotranspiration and discharge into the river screened by bottom sediments in which a river does not fully penetrate the aquifer. This analytical model can describe the groundwater discharge process in the presence of riparian evapotranspiration. We validated our analytical results with numerical simulations of a 2-D flow model that explicitly considers vertical hydraulic resistances, demonstrating that the surface water–groundwater exchanges in such hydrological systems are strongly dependent on the hydrogeological parameters, river width, riparian zone width, and parameters related to the hydraulic connection between evapotranspiration and groundwater. A sensitivity analysis of our extended DF model reveals that the water balance in hyperarid regions is determined by riparian evapotranspiration, and evapotranspiration most likely causes river flow losses. However, in humid regions, most groundwater (80% or more) is discharged into rivers rather than via riparian evapotranspiration. Our results confirm that riparian evapotranspiration in arid regions is an important process that affects surface water–groundwater exchanges and that evapotranspiration from riparian zones not only reduces groundwater discharge into rivers but also potentially causes disconnections within river–aquifer systems. The obtained analytical dependencies allow the grid-dependent parameters of the RIV and EVT packages to be calculated in the MODFLOW simulations of regional groundwater flow discharge in a river valley using coarse grids.

Porewater Sulfide: The Most Critical Regulator in the Degradation of Mangroves Dominated by Tides

The hydroperiod determines the biogeochemical conditions and processes developing in the mangrove soil. Floods control the input of nutrients and the presence of regulators such as salinity and sulfides that, in high concentrations, degrade mangrove vegetation. This work aimed to determine biogeochemical and hydroperiod characteristics in natural and degraded mangrove conditions. Three sampling sites were placed along a spatial gradient, including fringe and basin mangroves with different conditions. Tree characteristics and biogeochemical variables (temperature, salinity, pH, redox potential, sulfides) were measured. The structural analysis indicated two conditions: undisturbed (Rhizophora mangle fringe and Avicennia germinans basin under natural conditions) and disturbed (degraded basin, with standing A. germinans tree trunks). The soil porewater salinity, concentration of sulfides, and temperature were significantly higher, and redox potential lower in the disturbed site. The fringe mangrove was permanently waterlogged with higher tides than the basin mangrove. There were more extended flooding periods on the degraded mangrove due to the loss of hydrological connection with the adjacent water body. Waterlogging in basin mangroves increased soil porewater salinity to 87.8 and sulfides to 153 mg L−1, causing stress and death in A. germinans mangroves. Our results show that the loss of hydraulic connectivity causes the chronic accumulation of salinity and sulfides, with consequences on tree metabolism, ultimately causing its death. It probably also involves the succession in microbial communities.

Application of Temperature Fall-Off Interpretation Method in Superheavy Oil or Oil Sand SAGD Process

SAGD technology has been successfully and widely applied in the development of superheavy oil and oil sand projects. Before normal SAGD process, some preheating ways are often needed to realize interwell hydraulic connection, and this means that determining reasonable SAGD conversion timing from the preheating stage is an essential precondition for good performance. Previous numerical simulations or qualitative analysis of temperature fall-off data are often adopted in the industry, but they have deficiencies in terms of dependent on static geological model or insufficient data utilization. Therefore, on the basis of the temperature and pressure monitoring process comparison in China’s superheavy oil and Canada’s oil sand projects, this paper proposed a temperature fall-off interpretation model to obtain thermal diffusivity and preheating radius at different measurement points along the horizontal section by combining an unsteady thermal conduction model under constant heating power of wellbores in the radial coordinate system and approximately unsteady thermal conduction model with constant wellbore temperature and Fourier’s law of thermal conduction. Besides, the duration time, interpretation method, and application flow chart of temperature fall-off test were presented. Then, it was validated to successfully determine the timing of SAGD conversion from the preheating stage by an example combining with tracking numerical simulation, temperature inflection point analysis, and index analysis during the partial-SAGD and initial SAGD stages. The findings of this study can help determine the SAGD conversion timing from the preheating stage simpler and faster especially for the case of long horizontal well section deployed with more temperature measurement points.

Optimal Decomposition for the Monthly Contracted Electricity of Cascade Hydropower Plants Considering the Bidding Space in the Day-Ahead Spot Market

With the gradual opening of China’s electricity market, it is effective for cascade hydropower plants to simultaneously participate in both the monthly contract market and the day-ahead spot market to obtain higher power generation benefits. Hence, this paper studies the optimal decomposition model for the monthly contracted electricity of cascade hydropower plants considering the bidding space in the day-ahead spot market. The close hydraulic and electric connection between cascade hydropower plants, the implementation requirements of contracted electricity, and the uncertainty of the day-ahead market clearing price are all well considered. Several linearization techniques are proposed to address the nonlinear factors, including the objective function and the power generation function. A successive approximation (SA) approach, along with a mixed-integer linear programming (MILP) approach, is then developed to solve the proposed model. The presented model is verified by taking the decomposition of the monthly contracted electricity of cascade hydropower plants in China as an example. The results indicate that the developed model has high computational efficiency and can increase the power generation benefits compared with the conventional deterministic model. The effect of the penalty coefficient for imbalanced monthly contracted electricity is also evaluated, which provides a practical reference for market managers.

Integrating hydrochemical and microbial methods to identify hydraulic connections between three saltworks in southern Laizhou Bay, China

Integrating hydrochemical and microbial methods to identify hydraulic connections between three saltworks in southern Laizhou Bay, China

Following the flow-Microbial ecology in surface- and groundwaters in the glacial forefield of a rapidly retreating glacier in Iceland.

The retreat of glaciers in response to climate change has major impacts on the hydrology and ecosystems of glacier forefield catchments. Microbes are key players in ecosystem functionality, supporting the supply of ecosystem services that glacier systems provide. The interaction between surface and groundwaters in glacier forefields has only recently gained much attention, and how these interactions influence the microbiology is still unclear. Here, we identify the microbial communities in groundwater from shallow (<15 m deep) boreholes in a glacial forefield floodplain ('sandur') aquifer at different distances from the rapidly retreating Virkisjökull glacier, Iceland, and with varying hydraulic connectivity with the glacial meltwater river that flows over the sandur. Groundwater communities are shown to differ from those in nearby glacial and non-glacial surface water communities. Groundwater-meltwater interactions and groundwater flow dynamics affect the microbial community structure, leading to different microbial communities at different sampling points in the glacier forefield. Groundwater communities differ from those in nearby glacial and non-glacial surface waters. Functional potential for microbial nitrogen and methane cycling was detected, although the functional gene copy numbers of specific groups were low.

Chemical interaction driven by deep fluids in the damage zone of a seismogenic carbonate fault

We analyzed from meso-to microscale the chemical interaction (e.g., bleaching) between deep fluids and carbonate rocks in pelagic limestones exposed along the seismically active Gubbio normal fault (Northern Apennines), exhumed from ca. 2 km depth. Bleaching is enhanced by the exploitation of inherited stylolitic seams by fluids and is favored by the progressive leaching and mobilization of primary components (i.e., Ca, Fe, Pb, and Cu) and the precipitation of authigenic baryte due to temperature and/or redox potential contrast.Analysis of fluid inclusions trapped in calcite veins in the damage zone precipitated from a H2O–NaCl-bearing fluid(s), with low salinity (1.22–2.57 wt%NaCleq) and a range of trapping temperature between 107 °C and 185 °C, higher than the host rock peak T conditions. Analysis of fluid inclusions and noble gases from syn-kinematic calcite and mineralogy of altered rocks suggests a mixed contribution between crustal-derived fluids with diagenetic fluids containing sulphates and CO2. We speculate that bleaching is a by-product of the circulation of such aggressive fluids with mixed contributions, likely mobilized during seismic event(s) and injected into the damage zone at shallow depths. Such processes, affecting the chemical-physical properties of limestones, are generally underestimated and should be considered when modelling hydraulic connectivity in fractured carbonate reservoirs.