scholarly journals Monitoring the Spatial and Temporal Variations in The Water Surface and Floating Algal Bloom Areas in Dongting Lake Using a Long-Term MODIS Image Time Series

2020 ◽  
Vol 12 (21) ◽  
pp. 3622
Author(s):  
Mengmeng Cao ◽  
Kebiao Mao ◽  
Xinyi Shen ◽  
Tongren Xu ◽  
Yibo Yan ◽  
...  
Keyword(s):  
Water Quality ◽  
Human Activities ◽  
Water Surface ◽  
Algal Bloom ◽  
Environmental Changes ◽  
Climatic Factors ◽  
Dongting Lake ◽  
Dynamic Learning ◽  
Traditional Methods

Significant water quality changes have been observed in the Dongting Lake region due to environmental changes and the strong influence of human activities. To protect and manage Dongting Lake, the long-term dynamics of the water surface and algal bloom areas were systematically analyzed and quantified for the first time based on 17 years of Moderate Resolution Imaging Spectroradiometer (MODIS) observations. The traditional methods (index-based threshold algorithms) were optimized by a dynamic learning neural network (DL-NN) to extract and identify the water surface area and algal bloom area while reducing the extraction complexity and improving the extraction accuracy. The extraction accuracy exceeded 94.5% for the water and algal bloom areas, and the analysis showed decreases in the algal bloom and water surface areas from 2001–2017. Additionally, the variations in the water surface and algal bloom areas are greatly affected by human activities and climatic factors. The results of these analyses can help us better monitor human contamination in Dongting Lake and take measures to control the water quality during certain periods, which is crucial for future management. Moreover, the traditional methods optimized by the DL-NN used in this study can be extended to other inland lakes to assess and monitor long-term temporal and spatial variations in algal bloom areas and can also be used to acquire baseline information for future assessments of the water quality of lakes.

Long-term effects of hydrometeorological and water quality conditions on algal dynamics in the Paldang dam watershed, Korea

2014 ◽  
Vol 14 (4) ◽  
pp. 601-608
Author(s):  
D.-W. Kim ◽  
J.-H. Min ◽  
M. Yoo ◽  
M. Kang ◽  
K. Kim
Keyword(s):  
Water Quality ◽  
Water Temperature ◽  
Chlorophyll A ◽  
Algal Bloom ◽  
Temporal Variations ◽  
Regulated River ◽  
Han River ◽  
Nutrient Levels ◽  
Short Period

The primary goal of this study is to shed light on some important factors that control algal bloom in a large-scale regulated river system. Long-term impacts of environmental conditions on algal dynamics were investigated in the Paldang dam watershed, Korea. Dam inflow, water temperature, chlorophyll-a, TN, PO4-P and TP data collected at five major dams located on the North Han River (NHR) and at four water quality monitoring sites on the South Han River were analyzed for 21 years (1992 to 2012) to examine spatio-temporal variations in each. A pattern of slightly increasing chlorophyll-a and nutrient levels in the NHR since 2001 indicates that algal dynamics were affected by the increased nutrient levels as well as the reduced flow conditions (−10% to −37%). The temporal variations in monthly averaged data collected during summer monsoon seasons (mainly July) over the two decades show that high chlorophyll-a levels observed in both rivers corresponded to the relatively lower flow condition, which means a reduced amount of dam water release due to low or no rainfall over a short period of time, and abnormally high water temperature. This study shows that flow control is most critical for effectively managing algal level in the rivers in the short term, and nutrient management in the watershed is the key to reducing the potential for algal bloom in the long term.

scholarly journals Environmental Reconstructions in the Upper Tana region, Kenya

2020 ◽  
Vol 1 (1) ◽  
pp. 1-10
Author(s):  
Lazarus Kinyua Ngari
Keyword(s):  
Environmental Change ◽  
Human Activities ◽  
Vegetation Change ◽  
Environmental Changes ◽  
Climatic Factors ◽  
Livestock Grazing ◽  
Plant Succession ◽  
Economic Activities ◽  
Agricultural Communities ◽  
The Past

This article sets out to unravel aspects of environmental changes in the Upper Tana during the second millennium AD. This aspect has not been adequately addressed in the Upper Tana. This makes it clear that a lacuna exists in the study of communities of the Upper Tana and the way they interact with their environment in the past and present times. The objective of this article is to evaluate the relationship between human activities and environmental change in the Upper Tana from AD 1000 to 1950. It is hypothesized that the advent of iron technology and its attendant economic activities led to the depletion of indigenous forests and the general environmental degradation. The article has employed archaeological, ethnographic, oral and historical methodologies to gather data on vegetation change in the Upper Tana and other related regions.  The article, argues that livestock grazing, iron smelting, slush and burn agriculture, and the clearing of forests for housing are key contributors to vegetation change in the Upper Tana.  Results from oral reconstruction of the past vegetation of the area, and using the plant succession theory, shows that the lowland area of the Upper Tana is actually savanna with scattered trees probably inhabited by grazers. It is posited that the above factors, together with persistent droughts have altered the vegetation cover of the area.  What we have today is colonization of less desirable stunted growth. The theory advanced here is that the vegetation change has been a result of human activities.  Overwhelmingly, results the study that the researcher carried out, showed that the causes of these changes have been socio-economically associated with the expansion of agricultural communities into the area; rather than through climatic factors. Colonisation and other forces of modernistion have also contributed to the underlying problem. The article concludes that anthropogenetic factors have greatly contributed to environmental change in the upper Tana. Certainly, environmental change is a global phenomenon that has elicited research interests due to its negative impacts on human population. It is recommended that knowledge of environmental change in the past should be used to extrapolate modern environmental challenges affecting African ecosystems.

scholarly journals Monitoring water quality in estuarine environments: lessons from the MAGEST monitoring programme in the Gironde fluvial-estuarine system

2010 ◽  
Vol 7 (6) ◽  
pp. 9411-9436
Author(s):  
H. Etcheber ◽  
S. Schmidt ◽  
A. Sottolichio ◽  
E. Maneux ◽  
G. Chabaux ◽  
...  
Keyword(s):  
Water Quality ◽  
Environmental Changes ◽  
Monitoring Programme ◽  
Reference Database ◽  
Estuarine System ◽  
Gironde Estuary ◽  
Future Evolution ◽  
External Forcings ◽  
Frequency Monitoring

Abstract. The Gironde estuary, one of the largest European ones, presents temporary low dissolved oxygen content in its fluvial section close to the Bordeaux urban area. In a context of population growth and of long-term environmental changes, the development of a high-frequency monitoring programme of the fluvial-estuarine system of the Gironde, called MAGEST (MArel Gironde ESTuary), had appeared essential to address current and future water-quality issues/evaluations. The objectives of the MAGEST survey programme are to establish a reference database to improve the knowledge of the Gironde estuary functioning, encompassing the aspects of hydrology, sediment dynamics and biogeochemistry. Through examples of results from intratidal to seasonal time scales, we demonstrate how such a time-series is of valuable interest to extract the main trends of its functioning and of the water quality in relation to external forcings (climatology, urban wastes, land use, ...) and to predict the future evolution of the Gironde estuary with global and environmental changes.

scholarly journals A Remote Sensing Algorithm of Column-Integrated Algal Biomass Covering Algal Bloom Conditions in a Shallow Eutrophic Lake

2018 ◽  
Vol 7 (12) ◽  
pp. 466 ◽  
Author(s):  
Jing Li ◽  
Ronghua Ma ◽  
Kun Xue ◽  
Yuchao Zhang ◽  
Steven Loiselle
Keyword(s):  
Remote Sensing ◽  
Water Column ◽  
Algal Biomass ◽  
Water Surface ◽  
Algal Bloom ◽  
Eutrophic Lake ◽  
Retrieval Algorithm ◽  
Temporal Consistency ◽  
Eutrophic Lakes

Column integrated algal biomass provides a robust indicator for eutrophication evaluation because it considers the vertical variability of phytoplankton. However, most remote sensing-based inversion algorithms of column algal biomass assume a homogenous distribution of phytoplankton within the water column. This study proposes a new remote sensing-based algorithm to estimate column integrated algal biomass incorporating different possible vertical profiles. The field sampling was based on five surveys in Lake Chaohu, a large eutrophic shallow lake in China. Field measurements revealed a significant variation in phytoplankton profiles in the water column during algal bloom conditions. The column integrated algal biomass retrieval algorithm developed in the present study is shown to effectively describe the vertical variation of algal biomass in shallow eutrophic water. The Baseline Normalized Difference Bloom Index (BNDBI) was adopted to estimate algal biomass integrated from the water surface to 40 cm. Then the relationship between 40 cm integrated algal biomass and the whole column algal biomass at various depths was built taking into consideration the hydrological and bathymetry data of each site. The algorithm was able to accurately estimate integrated algal biomass with R2 = 0.89, RMSE = 45.94 and URMSE = 28.58%. High accuracy was observed in the temporal consistency of satellite images (with the maximum MAPE = 7.41%). Sensitivity analysis demonstrated that the estimated algal biomass integrated from the water surface to 40 cm has the greatest influence on the estimated column integrated algal biomass. This algorithm can be used to explore the long-term variation of algal biomass to improve long-term analysis and management of eutrophic lakes.

GIS-ROUT: A River Model for Watershed Planning

10.1068/b2624 ◽  
2000 ◽  
Vol 27 (2) ◽  
pp. 231-246 ◽  
Author(s):  
Xinhao Wang ◽  
Charlotte White-Hull ◽  
Scott Dyer ◽  
Ying Yang
Keyword(s):  
Water Quality ◽  
River Water ◽  
Spatial Data ◽  
Human Activities ◽  
Environmental Changes ◽  
Research Area ◽  
Analytical Models ◽  
Watershed Planning ◽  
Quality Model ◽  
Development Scenarios

Previous studies have shown that significant environmental changes are the result of human activities such as urbanization occurring at the spatial scale of landscapes. The challenge faced by many planners today is how to understand such relationships in order to support integrated watershed planning and management. Although many mathematical models have been developed to simulate the chemical transport process in a river, few are actually used in watershed assessment and management. Recently, incorporating analytical models into GIS platforms has emerged as a promising research area attracting planners and other resource managers. In this paper we present a GIS-based river water quality model (GIS-ROUT) to predict chemistry changes in river water as a result of sewage discharge changes in a watershed. Integration of spatial data, GIS, and analytical models in GIS-ROUT makes it possible to examine the dynamic linkages between water quality and human activities in a watershed. Furthermore, the user-friendly interface of the model allows its users to concentrate on the planning issues, such as examining the “What if…” questions related to different development scenarios. The study not only contributes to the application of GIS and water quality models in planning, but it also provides a comprehensive view of the watershed that can help government agencies and other stakeholders to make informed decisions.

scholarly journals Identification of Environment Chase in Surround of Sermo Reservoir; and the Influence Possibility for Function and at the Age of Reservoi

2004 ◽  
Vol 16 (1) ◽  
Author(s):  
Sudarmadji Sudarmadji
Keyword(s):  
Water Quality ◽  
Water Supply ◽  
Human Activities ◽  
Flood Control ◽  
Environmental Changes ◽  
Life Time ◽  
Early Observation ◽  
Domestic Water ◽  
Reservoir Water ◽  
Quality Degradation

Sermo reservoir is the only one belongs to Yogyakarta Special Province; it is relatively a new reservoir with the area of 1.9 kilometer square and its capacity of 25 million cubic meter: It started to operate since 1996 as flood control, irigation, water supply, tourism and fishery purposes. As a reservoir it could be considered to be a manmade lake, as its condition nearly similar to a lake. Since it operated (even during construction period) there were some significant environmental changes within the reservoir and in the area around the reservoir due to the human activities. These changes could threat the sustainability of the reservoir itselfThis research aims to identiflr the human activities living around the reservoir and visitors coming to the area, and to evaluate the potensial of the activities to produce wastes which is discharging in into the reservoir; which may threat the sustainability of the reservoir: The observatorium in the field has been conducted in the area of the reservoir and its sorrounding. I t was firund fiom the observation that activities o f fishery using net (karamba), tourism altogether with its facilities, land use around the reservoir for agriculture purposes, mining of class C ore, have given a lot of contribution to wastes (liquid and solids) and sediments into the reservoir: Those activities may cause water quality of the reservoir lo decrease as well as reducing the reservoir depth. Those situation was observed in the northern and north western parts of the reservoir Water quality degradation of the reservoir may threat reservoir as source of domestic water supply, while the sedimentation may reduce the life time of the reservoir The fishery and tourism activities was estimated as a main cause of water quality degradation, beside agricultural and domestic wastes originated from sattlement area around the reservoir: Sediments coming into the reservoir are derived fiom transported and movement of materials from land slide occuring around the reservoir; due to distruction of land in constructing the relatively new ring-road close to the shore line of the reservoir: Of course, the sediment is also coming from rivers enteringdie reservoir. Sermo reservoir is a relatively young reservoir; the early observation of environmental changes of the reservoir could hopely be used as indicator to study ecological changes of the area within and around of the reservoir; and could be used as a comparison to other reservoirs, as well as basic environmental management of the reservoir and its surrounding.

scholarly journals Paleontological methods in environmental science

1992 ◽  
Vol 6 ◽  
pp. 40-40
Author(s):  
Grace S. Brush ◽  
Humaira Khan
Keyword(s):  
Water Quality ◽  
Environmental Conditions ◽  
Human Disturbance ◽  
Large Scale ◽  
Environmental Changes ◽  
Nitrogen And Phosphorus ◽  
Ecological Requirements ◽  
Inorganic Substances ◽  
Stratigraphic Record

Long term environmental changes, induced both by natural and anthropogenic causes, cannot be assessed by looking solely at historical records of temperature, rainfall, water quality, etc. Frequently, such records are nonexistent. Where they do exist, they are often too short to be of much use. However, sediments contain a stratigraphic record of environmental change that allows comparison of the historic period influenced largely by humans, with prehistoric time when climate was the major determinant of environmental conditions.The stratigraphic record contains various fossilized organic materials which reflect environmental conditions at the time of the their deposition. Most abundant are pollen and spores of aquatic and terrestrial plants. Correspondence between pollen assemblages and vegetation has been found in all parts of the world. Therefore stratigraphic changes in pollen taxa reveal much information regarding the vegetational history of a region. Knowledge of the ecological requirements of various taxa can then be used to infer past climatic conditions. For example, dominance of Juglans (walnut) pollen indicates wet conditions while abundance of Pteridium (bracken fern) spores is an indicator of fire, suggesting drier conditions. Pollen can also be used to trace human disturbance to the environment. Sharp increases in the pollen of Ambrosia (ragweed) in sediment cores indicate large scale land clearance by man.Seeds preserved in sediments provide another measure of temporal vegetational change. Generally, seeds are not dispersed far from the parent plant; hence they provide a more local record of vegetation than pollen. A decrease in seeds of aquatic plants and increase in seeds of higher ground taxa when accompanied by increased sedimentation rates is an indicator of infilling of an aquatic environment. If unaccompanied by increased sedimentation, the change more likely represents lowering of sea level. Disappearance of seeds of taxa sensitive to turbidity and eutrophication provide another long term record of human disturbance.Distributions of diatoms are affected by temperature, salinity, oxygen, light availability and nutrient levels in the water. Therefore changes in diatom species preserved in the sediments can be used as indicators of climate, turbidity, anoxia and eutrophication in aquatic ecosystems.Many inorganic substances preserved in sediments also provide a long term record of changes in the environment. Nitrogen and phosphorus can be measured in cores and used as a surrogate record of water quality in lakes and estuaries. Sharp increases in sedimentary accumulation of metals record wastewater discharge and fuel emissions, related to human activity.

scholarly journals Monitoring water quality in estuarine environments: lessons from the MAGEST monitoring program in the Gironde fluvial-estuarine system

2011 ◽  
Vol 15 (3) ◽  
pp. 831-840 ◽  
Author(s):  
H. Etcheber ◽  
S. Schmidt ◽  
A. Sottolichio ◽  
E. Maneux ◽  
G. Chabaux ◽  
...  
Keyword(s):  
Water Quality ◽  
High Frequency ◽  
Environmental Changes ◽  
Monitoring Program ◽  
Reference Database ◽  
Estuarine System ◽  
Gironde Estuary ◽  
Future Evolution ◽  
Frequency Monitoring

Abstract. The Gironde Estuary, one of the largest European ones, presents temporary low dissolved oxygen content in its fluvial section close to the Bordeaux urban area. In a context of population growth and of long-term environmental changes, the development of a high-frequency monitoring programme of the fluvial-estuarine system of the Gironde, called MAGEST (MArel Gironde ESTuary), had appeared essential to address current and future water-quality issues/evaluations. The objectives of the MAGEST survey program are to establish a reference database to improve the knowledge of the Gironde Estuary functioning, encompassing the aspects of hydrology, sediment dynamics and biogeochemistry. Through examples of results from intratidal to seasonal time scales, we demonstrate how such a long-term, high-frequency monitoring of a fluvio-estuarine system is of valuable interest to extract the main trends of its functioning and of the water quality in relation to external forcings (climatology, urban wastes, land use, ...) and to predict the future evolution of an estuary with global and environmental changes.

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