scholarly journals Sand mining far outpaces natural supply in a large alluvial river

2021 ◽  
Vol 9 (5) ◽  
pp. 1323-1334
Author(s):  
Christopher R. Hackney ◽  
Grigorios Vasilopoulos ◽  
Sokchhay Heng ◽  
Vasudha Darbari ◽  
Samuel Walker ◽  
...  
Keyword(s):  
Satellite Imagery ◽  
Anthropogenic Activities ◽  
Low Cost ◽  
Large River ◽  
Large Rivers ◽  
Mekong River ◽  
Sand Mining ◽  
Natural Sand ◽  
Sand Extraction ◽  
Best Estimates

Abstract. The world's large rivers are facing reduced sediment loads due to anthropogenic activities such as hydropower development and sediment extraction. Globally, estimates of sand extraction from large river systems are lacking, in part due to the pervasive and distributed nature of extraction processes. For the Mekong River, the widely assumed estimate of basin-wide sand extraction is 50 Mt per year. This figure is based on 2013 estimates and is likely to be outdated. Here, we demonstrate the ability of high-resolution satellite imagery to map, monitor, and estimate volumes of sand extraction on the Lower Mekong River in Cambodia. We use monthly composite images from PlanetScope imagery (5 m resolution) to estimate sand extraction volumes over the period 2016–2020 through tracking sand barges. We show that rates of extraction have increased on a yearly basis from 24 Mt (17 to 32 Mt) in 2016 to 59 Mt (41 to 75 Mt) in 2020 at a rate of ∼8 Mt yr−1 (6 to 10 Mt yr−1), where values in parentheses relate to lower and upper error bounds, respectively. Our revised estimates for 2020 (59 Mt) are nearly 2 times greater than previous best estimates for sand extraction for Cambodia (32 Mt) and greater than current best estimates for the entire Mekong Basin (50 Mt). We show that over the 5-year period, only 2 months have seen positive (supply exceeds extraction) sand budgets under mean scenarios (5 months under the scenarios with the greatest natural sand supply). We demonstrate that this net negative sand budget is driving major reach-wide bed incision with a median rate of −0.26 m a−1 over the period 2013 to 2019. The use of satellite imagery to monitor sand mining activities provides a low-cost means to generate up-to-date, robust estimates of sand extraction in the world's large rivers that are needed to underpin sustainable management plans of the global sand commons.

scholarly journals An Alternative Statistical Model for Predicting Salinity Variations in Estuaries

2020 ◽  
Vol 12 (24) ◽  
pp. 10677
Author(s):  
Ronghui Ye ◽  
Jun Kong ◽  
Chengji Shen ◽  
Jinming Zhang ◽  
Weisheng Zhang
Keyword(s):  
Statistical Model ◽  
River Discharge ◽  
Numerical Models ◽  
Low Cost ◽  
River Estuary ◽  
Pearl River Estuary ◽  
Large River ◽  
Physical Models ◽  
Long Term Effects ◽  
Salinity Variations

Accurate salinity prediction can support the decision-making of water resources management to mitigate the threat of insufficient freshwater supply in densely populated estuaries. Statistical methods are low-cost and less time-consuming compared with numerical models and physical models for predicting estuarine salinity variations. This study proposes an alternative statistical model that can more accurately predict the salinity series in estuaries. The model incorporates an autoregressive model to characterize the memory effect of salinity and includes the changes in salinity driven by river discharge and tides. Furthermore, the Gamma distribution function was introduced to correct the hysteresis effects of river discharge, tides and salinity. Based on fixed corrections of long-term effects, dynamic corrections of short-term effects were added to weaken the hysteresis effects. Real-world model application to the Pearl River Estuary obtained satisfactory agreement between predicted and measured salinity peaks, indicating the accuracy of salinity forecasting. Cross-validation and weekly salinity prediction under small, medium and large river discharges were also conducted to further test the reliability of the model. The statistical model provides a good reference for predicting salinity variations in estuaries.

scholarly journals Distributed model of hydrological and sediment transport processes in large river basins in Southeast Asia

2015 ◽  
Vol 12 (7) ◽  
pp. 6755-6797 ◽  
Author(s):  
S. Zuliziana ◽  
K. Tanuma ◽  
C. Yoshimura ◽  
O. C. Saavedra
Keyword(s):  
Sediment Transport ◽  
Suspended Sediment ◽  
River Basin ◽  
River Basins ◽  
Large River ◽  
Mekong River ◽  
Distributed Model ◽  
Mekong River Basin ◽  
Chao Phraya River ◽  
Large River Basins

Abstract. Soil erosion and sediment transport have been modeled at several spatial and temporal scales, yet few models have been reported for large river basins (e.g., drainage areas > 100 000 km2). In this study, we propose a process-based distributed model for assessment of sediment transport at a large basin scale. A distributed hydrological model was coupled with a process-based distributed sediment transport model describing soil erosion and sedimentary processes at hillslope units and channels. The model was tested on two large river basins: the Chao Phraya River Basin (drainage area: 160 000 km2) and the Mekong River Basin (795 000 km2). The simulation over 10 years showed good agreement with the observed suspended sediment load in both basins. The average Nash–Sutcliffe efficiency (NSE) and average correlation coefficient (r) between the simulated and observed suspended sediment loads were 0.62 and 0.61, respectively, in the Chao Phraya River Basin except the lowland section. In the Mekong River Basin, the overall average NSE and r were 0.60 and 0.78, respectively. Sensitivity analysis indicated that suspended sediment load is sensitive to detachability by raindrop (k) in the Chao Phraya River Basin and to soil detachability over land (Kf) in the Mekong River Basin. Overall, the results suggest that the present model can be used to understand and simulate erosion and sediment transport in large river basins.

scholarly journals A Portable Device for Methane Measurement Using a Low-Cost Semiconductor Sensor: Development, Calibration and Environmental Applications

Sensors ◽  
2021 ◽  
Vol 21 (22) ◽  
pp. 7456
Author(s):  
Leonardo Furst ◽  
Manuel Feliciano ◽  
Laercio Frare ◽  
Getúlio Igrejas
Keyword(s):  
Tin Dioxide ◽  
Anthropogenic Activities ◽  
Low Cost ◽  
Ventilation System ◽  
Treatment Plant ◽  
Good Alternative ◽  
Oxide Semiconductor ◽  
Spatial And Temporal Patterns ◽  
Cost System ◽  
Methane Concentrations

Methane is a major greenhouse gas and a precursor of tropospheric ozone, and most of its sources are linked to anthropogenic activities. The sources of methane are well known and its monitoring generally involves the use of expensive gas analyzers with high operating costs. Many studies have investigated the use of low-cost gas sensors as an alternative for measuring methane concentrations; however, it is still an area that needs further development to ensure reliable measurements. In this work a low-cost platform for measuring methane within a low concentration range was developed and used in two distinct environments to continuously assess and improve its performance. The methane sensor was the Figaro TGS2600, a metal oxide semiconductor (MOS) based on tin dioxide (SnO2). In a first stage, the monitoring platform was applied in a small ruminant barn after undergoing a multi-point calibration. In a second stage, the system was used in a wastewater treatment plant together with a multi-gas analyzer (Gasera One Pulse). The calibration of low-cost sensor was based on the relation of the readings of the two devices. Temperature and relative humidity were also measured to perform corrections to minimize the effects of these variables on the sensor signal and an active ventilation system was used to improve the performance of the sensor. The system proved to be able to measure low methane concentrations following reliable spatial and temporal patterns in both places. A very similar behavior between both measuring systems was also well noticeable at WWTP. In general, the low-cost system presented good performance under several environmental conditions, showing itself to be a good alternative, at least as a screening monitoring system.

scholarly journals Assessment of the Impacts of Anthropogenic Activities on a Large River Using Longfin Eel as a Bioindicator

2020 ◽  
Vol 12 (20) ◽  
pp. 8412
Author(s):  
Olivier Champeau ◽  
James M. Ataria ◽  
Grant L. Northcott ◽  
Gen Kume ◽  
Andrew Barrick ◽  
...  
Keyword(s):  
Native Species ◽  
Anthropogenic Activities ◽  
Economic Value ◽  
River System ◽  
Large River ◽  
Chemical Contamination ◽  
Bioindicator Species ◽  
Tissue Samples ◽  
Anthropogenic Stressors ◽  
Residential Land Use

The Matāura River is the sixth largest river system in New Zealand and has long been subject to agricultural, industrial, and residential land use activities. The catchment has economic value and is of great cultural importance for local Māori, who have concerns over potential adverse impacts that anthropogenic stressors exert on the health of the river. There is a dearth of information on the impacts of these stressors towards the health of native species such as the longfin eel Anguilla dieffenbachii. This study assessed the environmental status of the Matāura River using biological and chemical methodologies incorporating A. dieffenbachii as a bioindicator species for exposure to multiple anthropogenic stressors. A range of biomarkers were measured in caged and wild-caught eels (when available) to characterize site-specific responses to anthropogenic stressors. While there was no clear indication of cumulative impacts moving from pristine headwaters to the lower reaches of the Matāura River, biomarkers of xenobiotic metabolization were induced in A. dieffenbachia and there was evidence of chemical contamination in sediment and tissue samples.

scholarly journals Study on Compressive Strength of Quarry Dust as Fine Aggregate in Concrete

2016 ◽  
Vol 2016 ◽  
pp. 1-5 ◽  
Author(s):  
K. Shyam Prakash ◽  
Ch. Hanumantha Rao
Keyword(s):  
Compressive Strength ◽  
Environmental Pollution ◽  
Low Cost ◽  
Experimental Investigations ◽  
Fine Aggregate ◽  
Normal Concrete ◽  
Natural Sand ◽  
Alternative Material ◽  
Quarry Dust

The concept of replacement of natural fine aggregate by quarry dust which is highlighted in the study could boost the consumption of quarry dust generated from quarries. By replacement of quarry dust, the requirement of land fill area can be reduced and can also solve the problem of natural sand scarcity. The availability of sand at low cost as a fine aggregate in concrete is not suitable and that is the reason to search for an alternative material. Quarry dust satisfies the reason behind the alternative material as a substitute for sand at very low cost. It even causes burden to dump the crusher dust at one place which causes environmental pollution. From the results of experimental investigations conducted, it is concluded that the quarry dust can be used as a replacement for fine aggregate. It is found that 40% replacement of fine aggregate by quarry dust gives maximum result in strength than normal concrete and then decreases from 50%. The compressive strength is quantified for varying percentage and grades of concrete by replacement of sand with quarry dust.

Change Detection Within Pipeline ROWs: Environmental Change Analysis Using High Resolution Satellite Imagery

2015 ◽  
Author(s):  
Otto Huisman ◽  
Arash Gharibi
Keyword(s):  
Decision Making ◽  
High Resolution ◽  
Environmental Change ◽  
Satellite Imagery ◽  
Vegetation Index ◽  
Low Cost ◽  
Comparison Method ◽  
Large Area ◽  
Change Analysis ◽  
High Resolution Satellite Images

One of the major concerns for pipeline operators is to efficiently monitor the events happening over the pipeline corridor, or right-of-way (ROW). Monitoring of the ROW is an important part of ensuring the safe and efficient transportation of oil and gas. Events occurring within this zone require rapid assessment and, if necessary, mitigation. These events could be physical intrusions such as encroachment from growing settlements, impact of vegetation, pipeline leakage or geo-environmental hazards. Analysis of satellite imagery can provide an efficient and low cost solution to access and quantify change across the ROW. Examining these events over a periodic interval requires implementation of specific methods that can support the on-going monitoring and decision making practices. In this context, satellite remote sensing images can provide a low cost and efficient solution for monitoring the physical and environmental impacts over the ROW of pipeline system. This paper reports on the development of a methodological approach for environmental change analysis using high resolution satellite images that can help decision making in pipeline systems. Analysis results and maps produced during this work provide an insight into landcover change over the study area and expected to support in on-going pipeline management practices. Two methods, Vegetation index differencing and post classification comparison have been implemented to identify change areas in the Taranaki region of the North Island of New Zealand. Vegetation index differencing with NDVI shows increase or decrease of overall vegetation within the study area. Special focus was given on large area increase and decrease with area threshold value above 0.2 hectare. Detailed analysis of change was conducted with post classification comparison method that uses land cover classification results of year 2010 and 2013. An overall change of 10% has been observed throughout the study area with large area change of approximately 5%. Results obtained from post classification comparison method were further analyzed with 6 focus areas and compared with the existing soil data and rainfall data. The methods adopted during this study are expected to provide a base for environmental change analysis in similar pipeline corridors to support decision making.

scholarly journals Climate and Human-Driven Variability of Summer Hypoxia on a Large River-Dominated Shelf as Revealed by a Hypoxia Index

2021 ◽  
Vol 8 ◽  
Author(s):  
Kui Wang ◽  
Wei-Jun Cai ◽  
Jianfang Chen ◽  
David Kirchman ◽  
Bin Wang ◽  
...  
Keyword(s):  
Anthropogenic Activities ◽  
Principal Component ◽  
Large River ◽  
Subsurface Water ◽  
Nutrient Concentrations ◽  
Oxygen Solubility ◽  
Shelf Area ◽  
Nutrient Inputs ◽  
The Past ◽  
Respiration Rates

Coastal hypoxia has become common especially in large river dominated coastal ecosystems. To better quantify the severity of hypoxia and the contribution of hypoxia drivers, we applied principal component analysis (PCA) on observable properties from eight summer hypoxia events in the East China Sea and defined the first principal component as the hypoxia index (HI). Multiple linear regression showed that the HI significantly correlated with three direct hypoxia drivers including water column stratification, subsurface water residence time, and respiration rates, which accounted for 5.7, 55.3, and 34.5%, respectively, of the total variance of PCA derived HI. We further reconstructed the HI over the past 60 years using available long-term data of stratification, model-derived residence times and respiration rates. The results show that summer hypoxia has become more severe since the 1960s. ENSO and global warming may have exacerbated hypoxia by affecting the river discharge, resulting in freshening in the plume-impacted shelf area, while anthropogenic activities may have exacerbated hypoxia by elevating fluvial nutrient concentrations, resulting in higher respiration rates. In addition, warming of the bottom water from the Kuroshio Current accounts for an additional increasing rate for HI, which made hypoxia more severe by means of decreasing oxygen solubility. Overall, our results indicate that stratification, water residence and oxygen solubility resulting from climate change can explain about 80% while higher respiration resulting from higher nutrient inputs can explain about 20% of the variation in the severity of hypoxia during the past half century.

scholarly journals Strategies and Approaches Towards Environmental Biomonitoring of Freshwater Ecosystems in Philippines

2021 ◽  
Vol 20 (4) ◽  
Author(s):  
J. S. Berame ◽  
M. B. Hojilla ◽  
E. Trinidad ◽  
N. L. Lawsin ◽  
J. A. Orozco ◽  
...  
Keyword(s):  
Aquatic Ecosystems ◽  
Anthropogenic Activities ◽  
Low Cost ◽  
Action Plan ◽  
The Philippines ◽  
Freshwater Ecosystems ◽  
Current Status ◽  
Biochemical Alterations ◽  
Pollution Levels ◽  
Environmental Biomonitoring

The Philippines, like many other Asian countries, is struggling to combat the current widespread aquatic pollution levels caused by anthropogenic activities. Environmental biomonitoring is an efficient tool to detect and monitor the fluctuating toxicity levels in a dynamic ecosystem using bioindicators like algae, macrophytes, zooplankton, insect, bivalve mollusks, gastropod, fish, amphibians, and others to assess the extent and levels of pollution in aquatic ecosystems. The present review deliberates on the biomonitoring techniques such as bioaccumulation, biochemical alterations, population, and community-level approaches to evaluate the current status with respect to the extent and levels of pollution in the aquatic ecosystems in the Philippines which also is one of the biodiversity hotspots. Therefore, the potential applications for biomonitoring are proposed to mainly include evaluation of actual aquatic pollutions, bioremediation, toxicology prediction, and research on toxicological mechanisms. The purpose of such evaluations is to critically analyze and help stakeholders to come up with a strategic action plan with recommendations on a low-cost, sensitive, and effective bioindicator for rapid and efficient environmental biomonitoring.

scholarly journals Water quality and zooplankton community of the Eme River, Umuahia, Southeast Nigeria

2021 ◽  
pp. 1186-1194
Author(s):  
E.D. Anyanwu ◽  
◽  
O.G. Adetunji ◽  
S.N. Umeham ◽  
◽  
...  
Keyword(s):  
Water Quality ◽  
Community Structure ◽  
Human Activities ◽  
Anthropogenic Activities ◽  
Zooplankton Community ◽  
Sand Mining ◽  
Sample Collection ◽  
Zooplankton Community Structure ◽  
Filtration Method ◽  
Pollution Indicator

Abstract. Aquatic ecosystems and biota are often adversely affected by anthropogenic activities. Consequently, zooplanktons have been used to monitor anthropogenic impacts because of their sensitivity to their environment. Water quality and zooplankton community of the Eme River, Umuahia, was assessed between December 2017 and November 2018. The study was carried out in six stations in relation to human activities. Human activities in the watershed were dominated by sand mining. A quantitative filtration method was used for the zooplankton sample collection while standard sample collection and analytical methods were used for the water samples. The zooplankton species recorded were 27 while the most abundant zooplankton group was Rotifera. A known pollution indicator, Daphnia pulex, had the highest number of individuals. The effects of human activities in the watershed were reflected in the results of some of the physicochemical parameters of the river. The zooplankton assemblage and community structure also reflected the effects of human activities in the river. Combined effects of human activities and season contributed to the relatively low zooplankton abundance recorded particularly in some downstream stations. The impacts of sand mining on water quality and zooplankton were more remarkable in the downstream stations (4 6) where the activity was intense while a large number of children swimming and related activities during the dry season had some impacts in station 1. The dominance of indicator and tolerant species indicated that the river was undergoing eutrophication. Sand mining among other observed anthropogenic activities was a major contributor to the nutrient enrichment in the river. The major water quality parameters influencing the zooplankton community structure was revealed by canonical correspondence analysis.

scholarly journals Geospatial assessment of land use and land cover dynamics in the mid-zone of Ghana

2020 ◽  
Vol 62 (4) ◽  
pp. 288-305
Author(s):  
Addo Koranteng ◽  
Isaac Adu-Poku ◽  
Emmanuel Donkor ◽  
Tomasz Zawiła-Niedźwiecki
Keyword(s):  
Remote Sensing ◽  
Land Use ◽  
Land Cover ◽  
Satellite Imagery ◽  
Forest Cover ◽  
Anthropogenic Activities ◽  
Arable Land ◽  
Rapid Urbanization ◽  
The Past ◽  
Open Forest

AbstractLand use and land cover (LULC) terrain in Ghana has undergone profound changes over the past years emanating mainly from anthropogenic activities, which have impacted countrywide and sub-regional environment. This study is a comprehensive analysis via integrated approach of geospatial procedures such as Remote Sensing (RS) and Geographic Information System (GIS) of past, present and future LULC from satellite imagery covering Ghana’s Ashanti regional capital (Kumasi) and surrounding districts. Multi-temporal satellite imagery data sets of four different years, 1990 (Landsat TM), 2000 (Landsat ETM+), 2010 (Alos and Disaster Monitoring Constellation-DMC) and 2020 (SENTINEL), spanning over a 30-year period were mapped. Five major LULC categories – Closed Forest, Open Forest, Agriculture, Built-up and Water – were delineated premised on the prevailing geographical settings, field study and remote sensing data. Markov Cellular Automata modelling was applied to predict the probable LULC change consequence for the next 20 years (2040). The study revealed that both Open Forest and Agriculture class categories decreased 51.98 to 38.82 and 27.48 to 20.11, respectively. Meanwhile, Built-up class increased from 4.8% to 24.8% (over 500% increment from 1990 to 2020). Rapid urbanization caused the depletion of forest cover and conversion of farmlands into human settlements. The 2040 forecast map showed an upward increment in the Built-up area up to 35.2% at the expense of other LULC class categories. This trend from the past to the forecasted future would demand that judicious LULC resolutions have to be made to keep Ghana’s forest cover, provide arable land for farming activities and alleviate the effects of climate change.

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