Solute transport modelling for assessing the duration of river flow to improve the groundwater quality in an intensively irrigated deltaic region

Groundwater modelling is an important management tool to study the behaviour of aquifer system under various hydrological stresses. Present study was carried out in deltaic regions of the Cauvery river, with an objective of estimating the minimum river flow required to improve the groundwater quality by numerical modelling. Cauvery river delta is the most productive agricultural plains of south India, but the agricultural activities during the last few decades have decreased due to limited flow in the river and increasing concentration of solutes in groundwater in the eastern parts. In order to understand the causes for increasing concentration, a three-layered finite-difference flow model was formulated to simulate the groundwater head and solute transport. The model was used to simulate the groundwater flow and solute transport for 5 years from July 2007 to June 2012. There was a fairly good agreement between the computed and observed groundwater heads. The chloride and nitrate ions were considered for solute transport modelling. Observed and simulated temporal variation in chloride and nitrate concentrations were comparable. The simulated solute concentrations from July 2007 to June 2012 showed an accumulation of solutes in groundwater of coastal part of the study area. The model was used to find the flow to be maintained in the river and rainfall recharge required to flush the ions into the sea. This can be achieved by maintaining minimal flow in the river and through regulation of fertilizer use as well as by creating awareness of sustainable use of groundwater in this area.     

How did the Alxa Block respond to the Indo-Eurasian collision?

The Cenozoic deformation of the Alxa Block resulted directly from the evolution of the northern Qinghai-Tibetan Plateau. However, many data show that the deformation occurred only in the Middle-Late Miocene. Our studies show that the Altyn Tagh fault did not pass through the Alxa Block; on the contrary it went along the southern boundary of the Jintai-Huahai Basin, linking with the Helishan—southern Longshoushan fault. Due to important tectonic events in the northern Qinghai-Tibetan plateau during the Middle-Late Miocene time, the northern plateau underwent rapid uplift and the plateau compressed the Hexi Corridor Region, resulting in a change from NS-trending to EW-trending structures in the Jinta-Huahai basin, and in the development of compressive structures in the Beishan. The southern Alxa fault underwent right lateral movement, and in the northern and central parts of the block, NS-trending Tertiary extensional structures formed. These basins controlled by Tertiary faults are similar to basins developed by lateral extrusion with a strong foreland and weak limited boundaries. The authors suggest that a regional “conjugate” fault system resulted from nearly NS-trending compression from the Qinghai-Tibetan Plateau during the Miocene and Pliocene in the Alxa Block and southern Mongolia. And due to the control of early structures in these regions, most brittle faults reactivated earlier ductile faults; NW–SE faults along the Altai Mountain and NE–SW faults to the southeast in Mongolia consist of a “conjugate” fault system to the north. The Altyn Tagh fault and southern Helishan-Longshoushan fault comprise a “conjugate” fault system to the south. The Beishan and Jinta-Huahai Basin occupied the convergent area between these two sets of faults; the compression controlled the Tertiary deposition and led to the development of the Cenozoic Jinta-Huahai Basin. The Alxa Block bounded by these two sets of faults moved eastwards, which resulted in the development of Cenozoic compressive structures to the west of Helan Shan, and superimposed early ductile shear zones along the northeastern and southwestern boundaries of the Alxa Block respectively. This model could explain the Cenozoic deformation occurring in and around the Alxa region.     

How ready is ready? Measuring physical preparedness for severe storms

This paper investigates use of inventories, or checklists of activities, as an emergency management tool to motivate preparedness action in individuals. It develops the inventory concept to provide the foundation for a more targeted approach to storm preparation communication and community engagement. It also examines the potential efficacy of alternatives to paper-based checklists, such as web or smartphone applications. Academic and grey literature was reviewed to collect activities for a storm inventory for emergency agencies to measure individual preparedness and for individuals to measure their preparation progress. The resulting master list was refined for application and tested for useability in a pilot study of semi-structured interviews in a storm-susceptible community in Queensland, Australia. Also, clustering items by type of preparedness activity reveal where strengths and weaknesses exist in individual preparedness. For instance, preparation for leaving and safety planning were shown to be the areas of weakest activity in the pilot sample, while preparation of the house for a storm was the strongest area. In addition, behaviour change literature shows potential for effective use of an inventory-based smartphone application in motivating preparation activity. Data collected by a storm preparedness smartphone application could show where a communication or engagement program for targeted communities should be focused. It is supported by health literature that identifies preferences of individuals to make progress on complex tasks in stages, the value of lists to achievement of goals and demonstrated increase in uptake of activities prompted by smartphone applications over web or paper-based diaries.

     

How cold was it for Neanderthals moving to Central Europe during warm phases of the last glaciation?

Precise estimates of mean annual temperature (MAT) for when Neanderthals occupied Central Europe are critical for understanding the role that climatic and associated environmental factors played in Neanderthal migrations and in their ultimate extinction. Neanderthals were continuously present in the relatively warm regions of southern and Western Europe in the Pleistocene but only temporarily settled Central Europe (CE), presumably because of its colder and less hospitable climate. Here, we present a new approach for more spatially and temporally accurate estimation of palaeotemperatures based on the stable oxygen isotope composition of phosphates extracted from animal teeth found at sites linked directly to concurrent Neanderthal occupation. We provide evidence that Neanderthals migrated along the Odra Valley of CE during warmer periods throughout the Upper Pleistocene. The MATs during these migrations were about 6.8 °C for the warm phase of Oxygen Isotope Stage OIS 5a–d (prior to the OIS4 cold event) at ～115–74,000 yr BP and about 6.3 °C during the early OIS 3 warm phase ～59–41,000 yr BP. Our results show that temperatures during these phases peaked 2–4 °C above longer term estimates from ice cores and pollen records. We argue that our approach can provide valuable insights into evaluating the role of climate in human migration patterns in the Pleistocene.     

Is UN Sustainable Development Goal 15 relevant to governing the intimate land-use/groundwater linkage?

Hydrogeology Journal - The close link between land use and groundwater has long been recognised, but not widely translated into integrated policy and management practices. Common understanding is...     

How resilient is the labour market against natural disaster? Evaluating the effects from the 2010 earthquake in Chile

Natural disasters are one of the main channels through which ecological and socio-economic systems interact. In particular, the severe impacts of earthquakes could disrupt activities in the labour market. However, the literature barely researched the long-term effects of such events. To investigate this issue, this article is concentrated in Chile that is subject to recurring seismic movements. The 27 February 2010 Bío-Bío Chile earthquake (M_w 8.8) was the second strongest in the history of the country. This natural disaster can be used to evaluate the response of the labour market to an exogenous shock. Besides, the capacity for resilience in the labour market is crucial for people who rely on their job. This document analyses the impacts of the 2010 Bío-Bío earthquake and tsunami on Chilean labour market outcomes, in particular, the quality of employment. With this objective, different data are combined for analysing the effect in the short and long term. Also, distinct econometric techniques and exogenous measurements of seismic acceleration are used. The evidence shows that these catastrophes harmed the labour market in the short term. However, in the long term, the government’s reconstruction efforts and other factors could have attenuated the adverse effects over some variables in the most affected zones.

     

Indicators of the Anthropocene: is there a case for conservation?

The Earth's atmosphere, biosphere and lithosphere are increasingly being modified by human activity. Given this anthropogenic influence on the natural environment, the case for recognizing an Anthropocene Epoch has recently been made and there is ongoing debate as to whether, and how, to formally characterize and define such an epoch. As a contribution to this debate, this article explores whether or not the landscapes, deposits, landforms and key marker horizons that may be used to characterize and define an Anthropocene Epoch could, and should, be identified and conserved in the same manner as other parts of the geological succession. Anthropogenic features pose a conservation challenge, however, as they often cross cut existing conservation frameworks which tend to focus on the natural, historic or cultural environment. Developing a coherent approach to the conservation of the indicators of an Anthropocene Epoch would, therefore, require an integrated system of describing, auditing and designating features for conservation. A major benefit of such an approach would be the opportunities for interdisciplinary collaboration between the wide range of researchers interested or involved in studying and conserving the record of anthropogenic activity.     

The stability and equation of state for the cotunnite phase of TiO2 up to 70 GPa

The stability and equation of state for the cotunnite phase in TiO₂ were investigated up to a pressure of about 70 GPa by high-pressure in situ X-ray diffraction measurements using a laser-heated diamond anvil cell. The transition sequence under high pressure was rutile → α-PbO₂ phase → baddeleyite phase → OI phase → cotunnite phase with increasing pressure. The cotunnite phase was the most stable phase at pressures from 40 GPa to at least 70 GPa. The equation of state parameters for the cotunnite phase were established on the platinum scale using the volume data at pressures of 37–68 GPa after laser annealing, in which the St value, an indicator of the magnitude of the uniaxial stress component in the samples, indicates that these measurements were performed under quasi-hydrostatic conditions. The third-order Birch-Murnaghan equation of state at K ₀′ = 4.25 yields V ₀ = 15.14(5) cm³/mol and K ₀ = 294(9), and the second-order Birch-Murnaghan equation of state yields V ₀ = 15.11(5) cm³/mol and K ₀ = 306(9). Therefore, we conclude that the bulk modulus for the cotunnite phase is not comparable to that of diamond.     

How important is the impact of land-surface inundation on seawater intrusion caused by sea-level rise?

The influence of sea-level rise (SLR) on seawater intrusion (SWI) has been the subject of several publications, which consider collectively a range of functional relationships within various hydrogeological and SLR settings. Most of the recent generalized analyses of SWI under SLR neglect land-surface inundation (LSI) by seawater. A simple analytical method is applied to quantitatively assess the influence and importance of LSI on SLR–SWI problems under idealized conditions. The results demonstrate that LSI induces significantly more extensive SWI, with inland penetration up to an order of magnitude larger in the worst case, compared to the effects of pressure changes at the shoreline in unconfined coastal aquifers with realistic parameters. The study also outlines some of the remaining research challenges in related areas, concluding that LSI impacts are among other important research questions regarding the SLR–SWI problems that have not been addressed, including the effects of aquifer heterogeneities, real-world three dimensionality, and mitigation measures.     

The smoke is rising but where is the fire? Exploring effective online map design for wildfire warnings

The current study sought to offer guidance for developing effective web-based mapping tools for wildfire warnings by identifying (1) the important content for facilitating individuals’ decision-making, and (2) the optimal interface design for ensuring usability and ease of information access. A map-based warning tool was prototyped in the Australian context, followed by a usability and effectiveness evaluation through individual interviews and verbal protocol analysis to assess participants’ interaction with the mapping interface and information in response to the simulated warning scenario. The results demonstrated variations in participants’ approaches to wildfire warning response, revealing varied information needs. Specifically, most participants relied on their own assessment of the prospective threat, requiring specific wildfire-related information before eliciting a response. In contrast, the decision of a minority of the participants was motivated by response guidance from agencies, and accurate wildfire information was less important for their response. Imperative information for both types of residents therefore needs to be highlighted in a map-based warning tool to cater to a wide audience. Furthermore, a number of heuristics were identified for designing effective interactive functions to facilitate the control of, and access to, the various maps and textual information presented on the map-based warning interface.     

Long-term spatio-temporal hydrochemical and 222Rn tracing to investigate groundwater flow and water–rock interaction in the Gran Sasso (central Italy) carbonate aquifer

In the Gran Sasso fissured carbonate aquifer (central Italy), a long-term (2001–2007) spatio-temporal hydrochemical and ²²²Rn tracing survey was performed with the goal to investigate groundwater flow and water–rock interaction. Analyses of the physico-chemical parameters, and comparisons of multichemical and characteristic ratios in space and time, and subsequent statistical analyses, permitted a characterisation of the hydrogeology. At the regional scale, groundwater flows from recharge areas to the springs located at the aquifer boundaries, with a gradual increase of mineralisation and temperature along its flowpaths. However, the parameters of each group of springs may significantly deviate from the regional trend owing to fast flows and to the geological setting of the discharge spring areas, as corroborated by statistical data. Along regional flowpaths, the effects of seasonal recharge and lowering of the water table clearly cause changes in ion concentrations over time. This conceptual model was validated by an analysis of the ²²²Rn content in groundwater. ²²²Rn content, for which temporal variability depends on seasonal fluctuations of the water table, local lithology and the fracture network at the spring discharge areas, was considered as a tracer of the final stages of groundwater flowpaths.     

How does the elevation changing response to crustal thickening process in the central Tibetan Plateau since 120 Ma?

When and how the Tibetan Plateau formed and maintained its thick crust and high elevation on Earth is continuing debated. Specifically, the coupling relationship between crustal thickening and corresponding paleoelevation changing has not been well studied. The dominant factors in crustal thickness changing are crustal shortening, magmatic input and surface erosion rates. Crustal thickness change and corresponding paleoelevation variation with time were further linked by an isostatic equation in this study. Since 120 Ma crustal shortening, magmatic input and surface erosion rates data from the central Tibetan Plateau are took as input parameters. By using a one-dimensional isostasy model, the authors captured the first-order relationship between crustal thickening and historical elevation responses over the central Tibetan Plateau, including the Qiangtang and Lhasa terranes. Based on the modeling results, the authors primarily concluded that the Qiangtang terrane crust gradually thickened to ca. 63 km at ca. 40 Ma, mainly due to tectonic shortening and minor magmatic input combined with a slow erosion rate. However, the Lhasa terrane crust thickened by a combination of tectonic shortening, extensive magmatic input and probably Indian plate underthrusting, which thickened the Lhasa crust over 75 km since 25 Ma. Moreover, a long-standing elevation >4000 m was strongly coupled with a thickened crust since about 35 Ma in the central Tibetan Plateau.©2021 China Geology Editorial Office.     

Record-High Losses for Weather Disasters in the United States During the 1990s: How Excessive and Why?

During 1990–1996 the United States experienced record-setting insured property losses due to numerous weather catastrophes, each event causing $100 million or more in losses (1991 dollars). The total loss in this 7-year period, after adjustment to inflation and other factors, was $39.65 billion with $15 billion coming from one event, Hurricane Andrew. In the 1990s, 72 catastrophes occurred, half of the total number in the 40 preceding years, 1950–1989. Although the total loss and the number of catastrophes were exceptionally high in the 1990s, the average loss per event was $551 million, only slightly more than the $467 million average for catastrophes during 1950–1989. Furthermore, storm intensities in the 1990s were slightly less than those during the preceding 40 years, revealing the excess losses of the 1990s to be a result of an extremely large number of damaging storms causing losses exceeding $100 million. Examination of historical values of most weather extremes including hurricanes, floods, and tornadoes, did not show an increase during the 1990s, revealing that weather changes were not the principal cause of more catastrophes. Examination of recent demographic shifts in the U.S. reveals two changes, each based on major re-locations to higher-valued property concentrated in areas either with a high frequency of damaging storms (Gulf and East Coast), or to where even a small but intense storm can cause huge losses (urban areas and West Coast). These shifts, plus the continuing growth of population in other storm-prone areas have greatly increased society's vulnerability to storm damage. An in-depth analysis of many conditions was required to establish that the high losses and numerous catastrophes of the 1990s were largely the result of societal changes and not major weather changes. This revised version was published online in June 2006 with corrections to the Cover Date.     

How important is it to integrate riverine suspended sediment chemical composition with depth? Clues from Amazon River depth-profiles

The vertical variability in mineralogical, chemical and isotopic compositions observed in large river suspended sediments calls for a depth-integration of this variability to accurately determine riverine geochemical fluxes. In this paper, we present a method to determine depth-integrated chemical particulate fluxes of large rivers, based on river sampling along depth-profiles, and applied to the Amazon Basin lowland tributaries. The suspended particulate matter (SPM) concentration data from depth-profiles is modeled for a number of individual grain size fractions using the Rouse model, which allows to predict the grain size distribution of suspended sediment throughout the whole river cross-section. Then, using (1) the relationship between grain size distribution and the Al/Si ratio (2) relationships between the Al/Si ratio and the chemical concentrations, the chemical composition of river sediment is predicted throughout the river cross-section, and integrated to yield the depth-integrated chemical particulate flux for a number of chemical elements (e.g. Si, Al, Fe, Na, REEs, …). For elements such as Al, Fe, REEs, Th, the depth-integrated flux is around twice as high as the one calculated from river surface sample characteristics. For Na and Si, the depth-integrated flux is three times higher than the “surface” estimate, due to the enrichment of albite and quartz at the bottom of the river. Depth-integrated ⁸⁷Sr/⁸⁶Sr composition of suspended sediment, also predictable using this method, differs by more than 10⁻³ from the surface sample composition.Finally, potential implications of depth-integrated estimates of Amazon sediment chemistry are explored. Depth-integration of particulate ⁸⁷Sr/⁸⁶Sr isotopic ratios is necessary for a reliable use of Sr isotopes as a provenance tracer. The concept of steady-state weathering of a large river basin is revisited using depth-integrated sediment composition. This analysis shows that, in the Amazon Basin river, the previously observed discrepancy between (1) weathering intensities of channel surface sediment and (2) silicate-derived dissolved fluxes is only slightly accounted for by the vertical variability of suspended sediment weathering intensities. This observation confirms that most large rivers basins are not eroding at steady-state.     

Orbitally forced sedimentary rhythms in the stratigraphic record: is there room for tidal forcing?

The imprint of orbital cycles, which result from the varying eccentricity of the Earth’s orbit and changes in the orientation of its axis, have been recognised throughout the Phanerozoic rock record. Variations in insolation and their effect on climate are generally considered to be the sole transfer mechanism between the orbital variables and cyclic sedimentary successions. Common oceanographic principles, however, show that the ocean tide also responds to variations in the orbital parameters. The ocean tide has not yet been considered to be a valid, additional transfer mechanism for the orbital variations. In geological studies of Milankovitch cycles in sedimentary successions the insolation paradigm offers satisfying explanations, and the role of long‐term variations of the ocean tide has not yet been appreciated. Variations in the ocean tide, related to changing eccentricity (at present 0·0165, theoretical maximum 0·0728), affect a variety of oceanographic and sedimentary processes. In addition to the widely accepted paradigm of orbitally forced insolation changes, the tidal transfer of orbital signals may explain certain less well‐understood aspects of orbitally induced cycles in the stratigraphic record related to ocean mixing, organic productivity, and tidal processes in shallow seas and deep water. Variations of the ocean tide in relation to the 18·6 year lunar nodal cycle, which has no insolation counterpart by which they may be obscured, indeed show that these relatively small variations can produce significant effects in sedimentary environments that are sensitive to variations in the strength of the ocean tide. In analogy with the 18·6 year lunar nodal cycle, orbital variations of the tide on Milankovitch time scales are likely to have affected sedimentary systems in the past.     

Using impacts of deep-level mining to research karst hydrology—a Darcy-based approach to predict the future of dried-up dolomitic springs in the Far West Rand goldfield (South Africa). Part 2: predicting inter-compartmental flow and final groundwater tables

Some of the world’s deepest goldmines operate below dolomitic karst aquifers in the Far West Rand (FWR) goldfield, South Africa. Associated impacts include the continuous dewatering of karst aquifers for over six decades and irreversible changes of the hydrogeological setting. Affecting an area of approximately 400 km² by drawing down the water table up to 700 m, these impacts, and the large amounts of data generated in the process, are used as unique research opportunities to better understand the complex karst hydrology. The focus of this study is on predicting final water table elevations in rewatered aquifers after mining ceases taking the fact that mines hydraulically linked previously disconnected aquifers into account. While part 1 of this series develops the conceptual model, this second part utilises large sets of pertinent data to calculate actual flow rates for predicting the fate of dried up springs after mine closure. Following a Darcy-based approach first applied by Swart et al. (Environ Geol 44:751–770, 2003a) it is not only predicted that the springs will flow again but also shown that linear relationships exist between flow rates through a combined system of karst-fractured aquifers overlying the mine void and the associated hydraulic head driving them. This suggests that—at this scale—porous media-based equations can be meaningfully used to predict flow in non-porous media.