Tracking hidden crisis in India’s capital from space: implications of unsustainable groundwater use

National Capital Region (NCR, Delhi) in India is one of the fastest-growing metropolitan cities which is facing a severe water crisis due to increasing water demand. The over-extraction of groundwater, particularly from its unconsolidated alluvial deposits makes the region prone to subsidence. In this study, we investigated the effects of plummeting groundwater levels on land surface elevations in Delhi NCR using Sentinel-1 datasets acquired during the years 2014–2020. Our analysis reveals two distinct subsidence features in the study area with rates exceeding 11 cm/year in Kapashera—an urban village near IGI airport Delhi, and 3 cm/year in Faridabad throughout the study period. The subsidence in these two areas are accelerating and follows the depleting groundwater trend. The third region, Dwarka shows a shift from subsidence to uplift during the years which can be attributed to the strict government policies to regulate groundwater use and incentivizing rainwater harvesting. Further analysis using a classified risk map based on hazard risk and vulnerability approach highlights an approximate area of 100 square kilometers to be subjected to the highest risk level of ground movement, demanding urgent attention. The findings of this study are highly relevant for government agencies to formulate new policies against the over-exploitation of groundwater and to facilitate a sustainable and resilient groundwater management system in Delhi NCR.

Integration of Numerical Models and InSAR Techniques to Assess Land Subsidence Due to Excessive Groundwater Abstraction in the Coastal and Lowland Regions of Semarang City

This study was carried out to assess land subsidence due to excessive groundwater abstraction in the northern region of Semarang City by integrating the application of both numerical models and geodetic measurements, particularly those based on the synthetic aperture radar interferometry (InSAR) technique. Since 1695, alluvial deposits caused by sedimentations have accumulated in the northern part of Semarang City, in turn resulting in changes in the coastline and land use up to the present. Commencing in 1900, excessive groundwater withdrawal from deep wells in the northern section of Semarang City has exacerbated natural compaction and aggravated the problem of land subsidence. In the current study, a groundwater model equivalent to the hydrogeological system in this area was developed using MODFLOW to simulate the hydromechanical coupling of groundwater flow and land subsidence. The numerical computation was performed starting with the steady-state flow model from the period of 1970 to 1990, followed by the model of transient flow and land subsidence from the period of 1990 to 2010. Our models were calibrated with deformation data from field measurements collected from various sources (e.g., leveling, GPS, and InSAR) for simulation of land subsidence, as well as with the hydraulic heads from observation wells for simulation of groundwater flow. Comparison of the results of our numerical calculations with recorded observations led to low RMSEs, yet high R2 values, mathematically indicating that the simulation outcomes are in good agreement with monitoring data. The findings in the present study also revealed that land subsidence arising from groundwater pumping poses a serious threat to the northern part of Semarang City. Two groundwater management measures are proposed and the future development of land subsidence is accordingly projected until 2050. Our study shows quantitatively that the greatest land subsidence occurs in Genuk District, with a magnitude of 36.8 mm/year. However, if the suggested groundwater management can be implemented, the rate and affected area of land subsidence can be reduced by up to 59% and 76%, respectively.

Ways of solving the problems of rational nature management in the areas of alluvial deposits development

A characteristic feature of the developed placer deposits is that most of them (up to 90–95%) are hard to develop, and the sands included in them are hard to enrich, due to their location in the geographic and climatic zones with a harsh climate, where perennial and deep seasonal permafrost is widespread almost everywhere. About 40% of alluvial deposits are clayey, highly clayey or cemented. As a consequence, there are significant losses of the valuable component and a large negative impact on the environment, including due to repeated re–mining. The studies presented in this paper help to significantly reduce losses and increase the productivity of the dredge, thereby increasing metal recovery.

Динамика хозяйственного освоения Посурья в I тысячелетии н.э. Часть 1: данные стратиграфического анализа пойменных и балочных отложений

The article summarizes the results of a comprehensive landscape-archaeological study of the dynamics of human-environmental interaction in the Middle Sura region during the first millennium AD. The data resulted from the study of the River Sura floodplain at the former confluence of the Sura and the Malaya Sarka. The analysis of the sediments and buried soils indicates that the period between the first millennium BC and the first millennium AD saw a series of climatic cycles changing each other, with the floodplain periodically being available for various types of economic development. The Early Iron Age (first millennium BC – 2nd–3rd centuries AD) saw the formation of grey forest soils in the part of the floodplain under study. During this period, the area remained uninhabited, while the population was involved in the development of the elevated terraces and riverbanks. In contrast, in the second quarter of the first millennium AD the floodplain covered at the time by broadleaf forest had the most favorable conditions for settlement; the area was developed by the population that belonged to the Middle Volga variant of the Kiev culture. Their economic activity resulted in the gradual deforestation of the floodplain, with meadow landscapes arising instead of the forest. The second half of the 5th century saw drastic intensification of the floods and an increased runoff. The sites assigned to this period represent the developed stage of the Imen´kovo culture; these were located on the elevated terraces. The new stage of low flooding dates to the medieval period (8th–13th centuries), the soils bearing traces of steppe formation and subsequent development of the floodplain. Later, in the late Middle Age and the early Modern period, tillage shifted to watersheds and intensified, while the accumulation of layered alluvial deposits on the floodplain started again, with frequent and intense floods taking place. The study of the dynamics of the moistening of the Sura floodplain is asynchronous with the data of other studied regions of the Russian Plain, which raises the question of a relationship between the availability of floodplains for economic development and migration processes.

From Lithological Modelling to Groundwater Modelling: A Case Study in the Tiber River Alluvial Valley

This study presents the results of a research project financed by the Lazio Regional Government. The research focused on defining an integrated model of recent alluvial deposits in the Tiber River. To achieve this objective, geological boreholes were made to monitor the aquifer and in situ and laboratory tests were carried out. The data obtained were used to detail stratigraphic aspects and improve the comprehension of water circulation beneath the recent alluvial deposits of the Tiber River in the urban area of Rome, between the Ponte Milvio bridge and the Tiber Island. The stratigraphic intervals recognised in the boreholes were parameterised based on their litho-technical characteristics. The new data acquired, and integrated with existing data in the database of Institute of Environmental Geology and Geoengineering of the Italian National Research Council, made it possible to produce a three-dimensional model of the lithologies in the study area. The model of the subsoil, simplified for applied reasons, was described in hydrostratigraphic terms: three different lithotypes were subjected to piezometric levels monitoring. Finally, the research generated a numerical hydrological model in a steady state. In general, this study demonstrates how a numerical hydrogeological model calibrated by piezometric monitoring data can support the construction of a geological model, discarding or confirming certain hypotheses and suggesting other means of reconstructing sedimentary bodies.

Pattern and direction of groundwater flow and distribution of physical-chemical properties of groundwater in Randublatung basin

The people in the Randublatung basin (Grobogan, Blora, and Bojonegoro Regencies) using groundwater for daily needs and agriculture activity. As the initial step of basin-based groundwater management, it is necessary to understand the groundwater potential in this area: pattern and direction of groundwater flow and groundwater physical-chemical properties (pH, temperature, total dissolved solids, and electrical conductivity). This research aims to analyze the pattern and directions of groundwater flow, the physical-chemical properties, and the correlation between the two. This research method is field measurement of 45 different spots of dug wells in the Randublatung basin. Our results indicate that the pattern and direction of groundwater flow in the Randublatung basin are heading to Bengawan Solo River and then following the river’s flow. The groundwater physical-chemical properties measured: pH value is 6.8 on average, the temperature is 28.9 °C on average, TDS concentration is 409 mg/L average, and electrical conductivity rate is 843 μS/cm average. There is no significant correlation between groundwater flow with pH value and groundwater temperature. However, groundwater TDS concentration and electrical conductivity rate in the Randublatung basin increase as groundwater flows to the Bengawan Solo River, which is affected by the minerals of aquifer rocks (alluvial deposits).

The Duration and Geodynamics of Formation of the Angara–Vitim Batholith: Results of U–Pb Isotope (LA-ICP-MS) Dating of Magmatic and Detrital Zircons

—We present results of U–Pb (LA-ICP-MS) dating of detrital zircons from the alluvial deposits of the Angarakan River (North Muya Ridge, northern Baikal region), whose drainage basin is composed mainly of granitoids of the Barguzin Complex, typomorphic for the late Paleozoic Angara–Vitim batholith (AVB). Three age clusters with peaks at 728, 423, and 314 Ma have been identified in the studied population of detrital zircons. It is shown that small outliers of igneous and metamorphic rocks, probably similar to the large AVB roof pendants mapped beyond the drainage basin, are the source of Neoproterozoic and early Paleozoic zircons. The late Paleozoic cluster comprises two close peaks at 314 and 28 Ma, which totally “overlap” with the time of the AVB formation and mark a granitoid source of the zircons. The results of detrital-zircon geochronology, together with the data on bedrocks, point to the prolonged (~40 Myr) formation of the AVB, but the intensity of magmatism during this period calls for additional study. Based on the analysis of published geological, geochemical, and geochronological data, we assume that the AVB resulted from the plume–lithosphere interaction that began in the compression setting and gave way to extension 305–300 Ma (the Carboniferous–Permian boundary), which caused replacement of “crustal” granitoids by granitoids formed from a mixed mantle–crustal source.

Groundwater pollution in the Mesta River terrace caused by Eleshnitsa tailings pond – current status

Even after the implementation of eco-protective measures, the Eleshnitsa tailings pond continues to contaminate the Quaternary aquifer, formed in the alluvial deposits of Mesta River. A three-dimensional model of mass transport of selected key pollutants is developed on the basis of hydrochemical studies, geophysical surveys, and processing and systematization of monitoring data. The spread and degree of contamination in the Quaternary aquifer are estimated.

MORPHOLOGY OF THE FIRST MANDIBULAR TOOTH MICROTUS GREGALIS (RODENTIA, ARVICOLINAE) FROM THE MIDDLE PLEISTOCENE OF THE PRE-ALTAI PLAIN

In this paper morphological structure of the first lower molar m1 tooth of the narrow-skulled vole from alluvial deposits of the Pre-Altai Plain Middle Neo-Pleistocene is described. Morphological study of the vole remains showed that they belong to the modern species Microtus gregalis. At the same time, the study sample showed significant differences, both in morphological structure and in the size of the first lower molar, in comparison with the recent representatives of the same territory. The set of morphological and morphometric data shows that the studied voles occupy an intermediate position between M. gregaloides of the Early and M. gregalis of the Late Neo-Pleistocene. The ratio of m1 morphotypes also showed the relative primitiveness of the M. gregalis sampling. Morphological study of remains of the narrow-skulled vole from the Solonovka, Petropavlovskoe and Malinovka-4 locations confirmed the previously determined age for sediments containing the remains of microtheriofauna.

PROBLEMS OF DIFFERENTIATION AND CORRELATION OF ALLUVIAL DEPOSITS OF THE NEO-PLEISTOCENE IN THE LOWER OB REGION

The Upper Neo-Pleistocene alluvial deposits lie in a close hypsometric position in outcrops of the Lower Ob Region right bank. Their top usually does not rise above the level of 5 m above the tow-path edge. At the same level, glacial erratic masses of the Middle Pleistocene alluvium were recorded in a number of areas. The height of the 1st and 2nd sites of terraces (on average from 5 to 10–15 m) depends on the thickness of subaerial deposits overlapping the alluvium. The 3rd terrace above flood-plain of the Bolshaya (Big) Ob has no geomorphological expression, since the alluvium of the first Late Neo-Pleistocene interglacial period without ablation is drape overlain by parallely bedded precipitates of the glacier-ice-blocked lake of the first Late Neo-Pleistocene glaciation. Thus, the height of sites of terraced surfaces does not directly correlate with the age of their alluvial basement. Therefore, the geomorphological method for differentiation of river sediments is not effective for this region. In addition, the problems of differentiation and correlation of alluvial deposits of the Lower Ob Region right bank are complicated by the presence of fluvioglacial incisions of deglaciation stages of the Middle Neo-Pleistocene and Upper Neo-Pleistocene glaciations.