As one of main directions of green mining, short-wall block backfill mining (SBBM) could provide active control of water-conducting fractures development and strata movement. Furthermore, it could ...solve the problem of gangue accumulation on surface. According to the physical similarity criterion and the characteristics of SBBM technology, the protection effect for surface water resources of SBBM was studied by physical similarity simulation tests. The results of tests had shown that SBBM decreased the water-conducting fractures development caused by strata movement after coal mining, and it has a significant effect in protecting surface water resources above the working face. Therefore, based on movement characteristics of overlying strata using SBBM, a mechanical analysis model was established under SBBM for a superimposed beams in elastic foundation with extended water-conducting fractures in overlying strata, furthermore, a method to calculate the height of water-conducting fractured zone (HWFZ) in SBBM was given, and the mechanical mechanism of water-conducting fractures development in overlying strata was revealed. The calculated HWFZ after SBM was only 2.0 m according to the mechanical model, whereas the measured HWFZ of the washing fluid loss and drilling TV imaging was 6.3 m in experimental SBBM working face. The field-measured data was closely consistent with the results of the tests (7.9 m) and the mechanical calculation (2.0 m), which verified the accuracy of physical similarity simulation tests and the mechanical model. The results of the study will enhance the recovery rate of coal resources, and they have a significant for protection of the ecological environment.
Display omitted
•SBBM was proposed to recover coal seam under surface water.•Surface water resources protection effect using SBBM was analyzed by physical tests.•Mechanical mechanism of water-conducting fractures development was explained.•A method was proposed to calculate HWFZ in SBBM.
Continuous monitoring of surface water resources is often challenging due to the lack of monitoring systems in remote areas and the high spatial distribution of water bodies. The Google Earth Engine ...(GEE) platform, which houses a large set of remote sensing datasets and geospatial processing power, has been applied in various aspects of surface water resources monitoring to solve some of the challenges. PyGEE-SWToolbox is a freely available Google Earth Engine-enabled open-source toolbox developed with Python to be run in Jupyter Notebooks that provides an easy-to-use graphical user interface (GUI) that enables the user to obtain time series of Landsat, Sentinel-1, and Sentinel-2 satellite imagery, pre-process them, and extract surface water using water indices, such as the Normalized Difference Water Index (NDWI), Modified NDWI (MNDWI), Automated Water Extraction Index (AWEI), and Dynamic Surface Water Extent (DSWE). The validation of the toolbox is carried out at four reservoir and lake locations: Elephant Butte Lake, Hubbard Creek Reservoir, Clearwater Lake, and Neversink Reservoir in the United States. A time series of the water surface area generated from PyGEE-SWToolbox compared to the observed surface areas yielded good results, with R2 ranging between 0.63 and 0.99 for Elephant Butte Lake, Hubbard Creek Reservoir, and Clearwater Lake except the Neversink Reservoir with a maximum R2 of 0.52. The purpose of PyGEE-SWToolbox is to provide water resource managers, engineers, researchers, and students a user-friendly environment to utilize the GEE platform for water resource monitoring and generation of datasets. The toolbox is accompanied by a step-by-step user manual and Readme documentation for installation and usage.
Abstract
This paper combines environmental science, inorganic chemistry, water quality monitoring and other disciplines to analyze and assess the heavy metals in the water bodies and sediments of the ...Fenghe River Basin (FRB) in Shaanxi Province, and reveal their sources. The Water Quality Index (WQI), Nemero Index (Pn), Geological Accumulation Index (I-geo) and Potential Ecological Risk Index (RI) are used to assess heavy metals in water and sediments. Pearson correlation analysis (CA), hierarchical cluster analysis (HCA), principal component analysis (PCA) and positive matrix factorization (PMF) models are used to study the relationship and source of heavy metals. The results show that most of the residual heavy metals in the water are below the corresponding environmental quality standards for surface water. Most of the heavy metals in the sediment exceed the background value of the soil. The factors or sources of heavy metals in water and sediment are revealed in detail through PMF models. The main sources of pollution in the region are urban construction and transportation, the electronics industry, machinery manufacturing and tourism. In water, the average contribution rates of these four sources to heavy metals were 36.8%, 11.7%, 9.4% and 42.0%, and in sediments were 8.0%, 29.2%, 23.9% and 38.9%. Therefore, these sectors should be given sufficient attention.
Graphene oxide (GO) is widely employed due to its outstanding properties, leading to an increasing release into the environment and natural waters. Although some studies have reported on the ...photo-transformation of GO, its behavior in complex natural waters remains inadequately explored. This study demonstrates that different types of ions may promote the photoreduction of GO in the order of Ca2+ > K+ > NO3− > Na+ by interacting with the functional groups on the surface of GO, and the photoreduction is enhanced with increasing ion concentrations. Additionally, natural organic matter (NOM) can inhibit the photoreduction of GO by scavenging reactive oxygen species. However, with increasing NOM concentrations (≥ 5 mgC/L), more NOM adsorb onto the surface of GO through hydrogen bonding, Lewis acid-base interactions, and π-π interactions, thereby enhancing the photoreduction of GO. On this basis, our results further indicate that the combined effects of different ions, such as Ca2+, Mg2+, NOM, and other complex hydrochemical conditions in different natural waters can promote the photoreduction of GO, resulting in a reduction in oxygen functional groups and the formation of defects. This study provides a theoretical basis for assessing the long-term transformation and fate of GO in natural waters.
Display omitted
•Carbon/oxygen ratio of GO increased upon UV and visible irradiation.•GO photoreduction is enhanced by increasing Na+ in aqueous system.•NOM at ≥ 5 mgC/L enhances GO photoreduction through surface adsorption.•GO photoreduction in natural waters is complex due to intricate interactions.
A spatial analysis of hydrochemical data of groundwater and surface water was undertaken to identify groundwater-surface water connectivity in the headwaters of the Condamine River catchment, ...Southeast Queensland, Australia. An assessment of long-term hydrochemical and water level data supplemented by stable- and radioisotope measurements following a prolonged dry period dominated by baseflow, helped in determining patterns of interaction in different tributaries of the upper Condamine catchment. A conceptual hydrological model representing the major hydrochemical processes and their implications for stream-aquifer connectivity was developed and tested using multiple lines of evidence.
The results of a multivariate statistical analysis highlight that there are two main regions with distinct hydrochemical facies (salinity, alkalinity, and predominant ions) in surface water. Geomorphology, geology, anthropogenic and climate influence were identified as the most relevant controlling factors of the spatial variability in water quality.
Stable isotope data confirmed a clear evaporation trend in almost all surface water samples during baseflow conditions. Two water types can be identified and separated by the degree of evaporation and the proximity of one group to the local meteoric water line. The results confirm the discharge of groundwater from aquifers recharged by rainfall and located upstream of the surface water sampling sites.
Overall, 222Rn data show a trend of increased activity in surface water towards the upstream portions of these tributaries, validating the use of this tracer to estimate groundwater input to the local creeks. The proportion of groundwater contribution to stream flow calculated by 222Rn and chloride mass balance is in agreement, and ranges between 20–70% in tributaries in the northern areas, and between 8–50% in the upper reaches of the main river channel.
This study shows the efficacy of an integrated approach combining long-term hydrochemical data interpreted via multivariate statistics, hydraulic water level data and stable and radiogenic isotope hydrology for the determination of groundwater–surface interactions in headwater catchments.
•Two distinct surface water groups identified by multivariate statistical analysis•Groundwater contribution into creek flows estimated using hydrochemistry and 222Rn•Stable and radioisotopes greatly assisted in assessing GW–SW interactions.•A conceptual model describing GW–SW connectivity was developed.
Abstract
Groundwater provides critical freshwater supply, particularly in dry regions where surface water availability is limited. Climate change impacts on GWS (groundwater storage) could affect the ...sustainability of freshwater resources. Here, we used a fully-coupled climate model to investigate GWS changes over seven critical aquifers identified as significantly distressed by satellite observations. We assessed the potential climate-driven impacts on GWS changes throughout the 21
st
century under the business-as-usual scenario (RCP8.5). Results show that the climate-driven impacts on GWS changes do not necessarily reflect the long-term trend in precipitation; instead, the trend may result from enhancement of evapotranspiration, and reduction in snowmelt, which collectively lead to divergent responses of GWS changes across different aquifers. Finally, we compare the climate-driven and anthropogenic pumping impacts. The reduction in GWS is mainly due to the combined impacts of over-pumping and climate effects; however, the contribution of pumping could easily far exceed the natural replenishment.
•Properties and processes of the GW–SW interface are variable in space and time.•Revealing hydrological and biogeochemical heterogeneity remains a challenge.•Geophysics offer useful tools for ...addressing variability across multiple scales.•Future studies should incorporate geophysical progress gained in parallel fields.
Interactions between groundwater (GW) and surface water (SW) have important implications for water quantity, water quality, and ecological health. The subsurface region proximal to SW bodies, the GW–SW interface, is crucial as it actively regulates the transfer of nutrients, contaminants, and water between GW systems and SW environments. However, geological, hydrological, and biogeochemical heterogeneity in the GW–SW interface makes it difficult to characterise with direct observations. Over the past two decades geophysics has been increasingly used to characterise spatial and temporal variability throughout the GW–SW interface. Geophysics is a powerful tool in evaluating structural heterogeneity, revealing zones of GW discharge, and monitoring hydrological processes. Geophysics should be used alongside traditional hydrological and biogeochemical methods to provide additional information about the subsurface. Further integration of commonly used geophysical techniques, and adoption of emerging techniques, has the potential to improve understanding of the properties and processes of the GW–SW interface, and ultimately the implications for water quality and environmental health.
Observation of surface water is a functional requirement for studying ecological and hydrological processes. Recent advances in satellite‐based optical remote sensors have promoted the field of ...sensing surface water to a new era. This paper reviews the current status of detecting, extracting, and monitoring surface water using optical remote sensing, especially progress in the last decade. It also discusses the current status and challenges in this field, including spatio‐temporal scale issues, integration with in situ hydrological data and elevation data, obscuration caused by clouds and vegetation, and the growing need to map surface water at a global scale. Historically, sensors have exhibited a contradiction in resolutions. Techniques including pixel unmixing and reconstruction, and spatio‐temporal fusion have been developed to alleviate this contradiction. Spatio‐temporal dynamics of surface water have been modeled by combining remote sensing data with in situ river flow. Recent studies have also demonstrated that the river discharge can be estimated using only optical remote sensing imagery, providing valuable information for hydrological studies in ungauged areas. Another historical issue for optical sensors has been obscuration by clouds and vegetation. An effective approach of reducing this limitation is to combine with synthetic aperture radar data. Digital elevation model data have also been employed to eliminate cloud/terrain shadows. The development of big data and cloud computation techniques makes the increasing demand of monitoring global water dynamics at high resolutions easier to achieve. An integrated use of multisource data is the future direction for improved global and regional water monitoring.
Plain Language Summary
Observing surface water is essential for ecological and hydrological studies. This paper reviews the current status of detecting, extracting, and monitoring surface water using optical remote sensing, especially progress in the last decade. It also discusses the current status and challenges in this field. For example, it was found that pixel unmixing and reconstruction, and spatio‐temporal fusion are two common and low‐cost approaches to enhance surface water monitoring. Remote sensing data have been integrated with in situ river flow to model spatio‐temporal dynamics of surface water. Recent studies have also proved that the river discharge can be estimated using only optical remote sensing imagery. This will be a breakthrough for hydrological studies in ungauged areas. Optical sensors are also easily obscured by clouds and vegetation. This limitation can be reduced by integrating optical data with synthetic aperture radar data and digital elevation model data. There is increasing demand of monitoring global water dynamics at high resolutions. It is now easy to achieve with the development of big data and cloud computation techniques. Enhanced global or regional water monitoring in the future requires integrated use of multiple sources of remote sensing data.
Key Points
Satellite‐based optical sensors are an efficient means for observing surface water regionally and globally
Pixel unmixing and reconstruction, and spatio‐temporal fusion are two common and low‐cost approaches to enhance surface water monitoring
The potential to estimate flow using only optical remote sensing has greatly enriched the data source of hydrological studies
PDF
