The Tonle Sap Lake (known also as the Great Lake), located in central Cambodia, is the largest fr... more The Tonle Sap Lake (known also as the Great Lake), located in central Cambodia, is the largest freshwater lake in Southeast Asia and an important component in the Mekong River system. The area is globally unique and the lake has an extraordinary hydrological system. The importance of the Tonle Sap Lake goes far beyond provincial and even national boundaries. A MRCS/WUP-FIN project simulating the present ecosystem and functions of the lake has set up a three-dimensional (3D) EIA Flow Model and 3D EIA Water Quality Model for the Tonle Sap Lake. The models applied to the lake give an excellent tool to understand the ecosystem of the Tonle Sap Lake and to run different scenarios helping to find sustainable decisions for the future.
During the summers of 1989–1990, the pattern of water flow and the water quality in Lake Pyhäselk... more During the summers of 1989–1990, the pattern of water flow and the water quality in Lake Pyhäselkä, Finland, were studied using field observations and a 3-dimensional model. The lake receives its major point-source loading, including pulp mill effluents, via the Pielisjoki River in the northeastern part of the lake, where the water is slightly eutrophic. The flow pattern was measured with three types of recording current meters, two of which were conventional mechanical meters and the third a new acoustic current profiler. The profiler was used in direct reading mode on a research vessel and also in self-contained mode on a float installed in the deep basin of the lake. The water-quality part of the model simulates oxygen, BOD, total phosphorus, AOX, and phytoplankton biomass. The three-dimensional model applied here simulates accurately the flow pattern of the water in Lake Pyhäselkä. The results of this study made it possible to detect different flow patterns in the lake. The main load is clearly affected by the wind-induced pattern of flow.
During the summers of 1989–1990, the pattern of water flow and the water quality in Lake Pyhäselk... more During the summers of 1989–1990, the pattern of water flow and the water quality in Lake Pyhäselkä, Finland, were studied using field observations and a 3-dimensional model. The lake receives its major point-source loading, including pulp mill effluents, via the Pielisjoki River in the northeastern part of the lake, where the water is slightly eutrophic. The flow pattern was measured with three types of recording current meters, two of which were conventional mechanical meters and the third a new acoustic current profiler. The profiler was used in direct reading mode on a research vessel and also in self-contained mode on a float installed in the deep basin of the lake. The water-quality part of the model simulates oxygen, BOD, total phosphorus, AOX, and phytoplankton biomass. The three-dimensional model applied here simulates accurately the flow pattern of the water in Lake Pyhäselkä. The results of this study made it possible to detect different flow patterns in the lake. The main load is clearly affected by the wind-induced pattern of flow.
The ecosystem of the Gulf of Finland is currently dominated by internal phosphorus loading from s... more The ecosystem of the Gulf of Finland is currently dominated by internal phosphorus loading from sediments. The internal load is highly redox sensitive, and its successful modelling on basin-wide scale requires a simplified description of the sediment process. We present here an approach in which redox-sensitive sediment processes are directly linked to the decomposition of carbon instead of the oxygen concentration in near-bottom water. Mineralisation of organic carbon is known to be the major factor controlling sediment nutrient cycling, including denitrification and Fe(III) oxide reduction, giving rise to high phosphorus fluxes from anoxic sediments.
Natural resources are vital to people along the Mekong as the livelihood of most of the people de... more Natural resources are vital to people along the Mekong as the livelihood of most of the people depend to large extent on natural ecosystems, especially in the poorest countries Cambodia and Lao PDR. One of the most important parts of the Mekong system is the Tonle Sap Lake in Cambodia being the main source of animal protein for Cambodia and working as a natural reservoir for the Lower Mekong Basin. The Tonle Sap is also a significant breeding ground for many of the Mekong fish species.
... proper model for water quality in northern reservoirs. As a practical challenge, the model wa... more ... proper model for water quality in northern reservoirs. As a practical challenge, the model was to predict and help optimize the water quality effects of a scheduled third reservoir, Vuotos (Fig. 1). In 1988-92 the model development ...
... simulation of pollutants transport in the Abu-Qir Bay, East Alexandria, Egypt E. Al-Hogaraty^... more ... simulation of pollutants transport in the Abu-Qir Bay, East Alexandria, Egypt E. Al-Hogaraty^'*, W. Hamza^ J. Koponen J. Sarkkula^ and Alam El-Din ... 5. Lead In Abu-Qir Bay, the particulate form of lead was dominant in both surface and bottom water layers (Younes et al., 1997 ...
The three-dimensional water quality and flow model was used to simulate phytoplankton biomass and... more The three-dimensional water quality and flow model was used to simulate phytoplankton biomass and dissolved nutrient concentrations in the Gulf of Finland. In the model, transport of nutrients is based on calculated wind and river flow-induced currents. Water quality data from two points off the Finnish coast were used for the model calibration.
Riverbank erosion is a natural process, but often human activities can have a significant impact ... more Riverbank erosion is a natural process, but often human activities can have a significant impact on the rates of morphological change. This paper aims to assess bank erosion problems in the Vientiane-Nong Khai section of the Mekong River, where the Mekong borders Thailand and Lao PDR. The study provides new and more accurate information about recent riverbank movement rates. The bank movement rates are quantified using two Hydrographic Atlases dated 1961 and 1992, derived originally from aerial photos and a field survey, and SPOT5 satellite images acquired on 4 December 2004 and 28 April 2005 with a resolution of 2.5 m in natural colours. Bank erosion and accretion rates on the left (Lao PDR) and right (Thailand) banks of the Mekong are analysed for two time periods: 1961-1992 and 1992-2005, respectively. The quantified average bank erosion rates were found to be slow, ranging from 0.8 to 1.0 m/a for the first and second analysis period, respectively. These average annual erosion rates are only 0.1% of the channel width, which is very low on a global scale. However, erosion rates were much higher for the islands in the river, 2.4 and 4.8 m/a for the two time periods. The quantified accretion for the main banks was 0.4 m/a during 1961-1992 and 0.7 m/a during 1992-2005, which for the islands increased from 0.6 to 6.4 m/a from the first to the second period. r
Integrated Water Resources Management has been identified as one of the basic water resources rel... more Integrated Water Resources Management has been identified as one of the basic water resources related policy approaches in several recent important commitments and recommendations including the Johannesburg Summit and World Water Forums. Recognizing that IWRM is largely still a theoretical concept with not much sound scientific research, our objective is to investigate how the IWRM process in the Mekong Basin is institutionalised, and implemented in practice. We focus on the Cambodia's Great Lake, the Tonle Sap. Of particular interest are the bottlenecks of IWRM, both those that are within the water sector and those that relate to various, more general development tendencies.
International Journal of Water Resources Development, 2006
The monsoon floods of the Mekong River are a key driver of the Tonle Sap Lake ecosystem. This pul... more The monsoon floods of the Mekong River are a key driver of the Tonle Sap Lake ecosystem. This pulsing system together with a large floodplain, rich biodiversity and high annual sedimentation and nutrient fluxes from the Mekong makes the lake one of the most productive fresh water ecosystems in the world. The livelihoods of people living in and around the Tonle Sap are strongly dependent on the lake's natural resources. An integrated modelling system, supported with primary data collection and analysis, has been ...
1] Hydraulic erosion of bank toe materials is the dominant factor controlling the long-term rate ... more 1] Hydraulic erosion of bank toe materials is the dominant factor controlling the long-term rate of riverbank retreat. In principle, hydraulic bank erosion can be quantified using an excess shear stress model, but difficulties in estimating input parameters seriously inhibit the predictive accuracy of this approach. Herein a combination of analytical modeling and novel field measurement techniques is employed to improve the parameterization of an excess shear stress model as applied to the Lower Mekong River. Boundary shear stress is estimated using a model Smith, 2006a, 2006b) for flow over the irregular bank topography that is characteristic of fine-grained riverbanks. Bank erodibility parameters were obtained using a cohesive strength meter . The new model was used to estimate annual bank erosion rates via integration across the Mekong's annual flow regime. Importantly, the simulations represent the first predictions of hydraulic bank erosion that do not require recourse to calibration, thereby providing a stronger physical basis for the simulation of bank erosion. Model predictions, as evaluated by comparing simulated annual rates of bank toe retreat with estimates of bank retreat derived from analysis of aerial photographs and satellite imagery, indicate a tendency to overpredict erosion (root-mean-square error equals ±0.53 m/yr). Form roughness induced by bank topographic features is shown to be a major component (61%-85%) of the spatially averaged total shear stress, and as such it can be viewed as an important factor that self-limits bank erosion. Citation: Darby, S. E., H. Q. Trieu, P. A. Carling, J. Sarkkula, J. Koponen, M. Kummu, I. Conlan, and J. Leyland (2010), A physically based model to predict hydraulic erosion of fine-grained riverbanks: The role of form roughness in limiting erosion,
The Tonle Sap Lake and floodplains in the heart of Cambodia contain the largest continuous areas ... more The Tonle Sap Lake and floodplains in the heart of Cambodia contain the largest continuous areas of natural wetlands habitats remaining in the Mekong system, while being the largest permanent freshwater body in Southeast Asia. Tonle Sap is a crucially important source for food and living in Cambodia. More than one million people live in the immediate surroundings of the Tonle Sap Lake and wetlands, being the poorest ones in Cambodia, and highly dependent on agriculture and fisheries. An important phosphorus source of the mainly phosphorus limited aquatic ecosystem is the sediment carried by the flood. Mekong Upstream developments, like construction of dams may lead, and has already led, to significant trapping of sediments and nutrients. This would dramatically reduce the productivity of the Tonle Sap system. The 3D mathematical model has been set up for Tonle Sap Lake for simulating water levels and currents, inundation of the floodplain, suspended sediment transport and sedimentation, dissolved oxygen as well as nutrients and algal growth (chlorophyll-a) to understand the ecosystem processes and the possible changes in it due to the upstream development.
Helsinki is located on the southern coast of Finland by the Baltic Sea. The ecological state of t... more Helsinki is located on the southern coast of Finland by the Baltic Sea. The ecological state of the archipelago in front of Helsinki is affected by several factors. The effects of local point and scattered loads are mixed with the transboundary effects from neighbouring countries and atmospheric deposition. Municipal waste waters of 800 000 inhabitants of the capital area are released outside the archipelago into the open Gulf of Finland (GoF). In addition, river Vantaanjoki is transporting load originating from agriculture, industry and settlements of the drainage area to the shores of Helsinki. Toxic algal blooms and annoying filamentous algal mats have become a problem to the users of the coastal zone.
Natural resources are vital to people along the Mekong as the livelihood of most of the people de... more Natural resources are vital to people along the Mekong as the livelihood of most of the people depend to large extent on natural ecosystems, especially in the poorest countries Cambodia and Lao PDR. One of the most important parts of the Mekong system is the Tonle Sap Lake in Cambodia being the main source of animal protein for Cambodia and working as a natural reservoir for the Lower Mekong Basin. The Tonle Sap is also a significant breeding ground for many of the Mekong fish species.
One of the most visible symptoms of eutrophication in the Gulf of Finland is blooms of unattached... more One of the most visible symptoms of eutrophication in the Gulf of Finland is blooms of unattached filamentous algae. This decomposing algal biomass causes serious nuisance problems for recreational uses of the coastal zone, particularly when cast ashore. The nutrient availability for these macroscopic filamentous algae is regulated by a superior competitor, the phytoplankton. Nutrients are left for the weaker competitor only when the conditions are not suitable for the growth of phytoplankton. This happens during vertical mixing of the water column. The lack of stratification prevents the formation of phytoplankton blooms, but does not limit the growth of filamentous algae when still growing attached to the bottom. A simple growth model was developed to describe the growth and biomass of filamentous algae. In the absence of suitable nutrient measurements, the model was linked to a 3D-ecohydrodynamic model which generated the nutrient input data. The model was calibrated with three-year monitoring data of filamentous algal biomass at one location. Validation was carried out with one-year monitoring data from an adjacent location. The model was able to describe the number of biomass peaks and their timing with good accuracy. After further development, the filamentous algal model will be used as one of the management tools for the evaluation of the sustainable nutrient load to the Gulf of Finland.
... proper model for water quality in northern reservoirs. As a practical challenge, the model wa... more ... proper model for water quality in northern reservoirs. As a practical challenge, the model was to predict and help optimize the water quality effects of a scheduled third reservoir, Vuotos (Fig. 1). In 1988-92 the model development ...
The Tonle Sap Lake (known also as the Great Lake), located in central Cambodia, is the largest fr... more The Tonle Sap Lake (known also as the Great Lake), located in central Cambodia, is the largest freshwater lake in Southeast Asia and an important component in the Mekong River system. The area is globally unique and the lake has an extraordinary hydrological system. The importance of the Tonle Sap Lake goes far beyond provincial and even national boundaries. A MRCS/WUP-FIN project simulating the present ecosystem and functions of the lake has set up a three-dimensional (3D) EIA Flow Model and 3D EIA Water Quality Model for the Tonle Sap Lake. The models applied to the lake give an excellent tool to understand the ecosystem of the Tonle Sap Lake and to run different scenarios helping to find sustainable decisions for the future.
During the summers of 1989–1990, the pattern of water flow and the water quality in Lake Pyhäselk... more During the summers of 1989–1990, the pattern of water flow and the water quality in Lake Pyhäselkä, Finland, were studied using field observations and a 3-dimensional model. The lake receives its major point-source loading, including pulp mill effluents, via the Pielisjoki River in the northeastern part of the lake, where the water is slightly eutrophic. The flow pattern was measured with three types of recording current meters, two of which were conventional mechanical meters and the third a new acoustic current profiler. The profiler was used in direct reading mode on a research vessel and also in self-contained mode on a float installed in the deep basin of the lake. The water-quality part of the model simulates oxygen, BOD, total phosphorus, AOX, and phytoplankton biomass. The three-dimensional model applied here simulates accurately the flow pattern of the water in Lake Pyhäselkä. The results of this study made it possible to detect different flow patterns in the lake. The main load is clearly affected by the wind-induced pattern of flow.
During the summers of 1989–1990, the pattern of water flow and the water quality in Lake Pyhäselk... more During the summers of 1989–1990, the pattern of water flow and the water quality in Lake Pyhäselkä, Finland, were studied using field observations and a 3-dimensional model. The lake receives its major point-source loading, including pulp mill effluents, via the Pielisjoki River in the northeastern part of the lake, where the water is slightly eutrophic. The flow pattern was measured with three types of recording current meters, two of which were conventional mechanical meters and the third a new acoustic current profiler. The profiler was used in direct reading mode on a research vessel and also in self-contained mode on a float installed in the deep basin of the lake. The water-quality part of the model simulates oxygen, BOD, total phosphorus, AOX, and phytoplankton biomass. The three-dimensional model applied here simulates accurately the flow pattern of the water in Lake Pyhäselkä. The results of this study made it possible to detect different flow patterns in the lake. The main load is clearly affected by the wind-induced pattern of flow.
The ecosystem of the Gulf of Finland is currently dominated by internal phosphorus loading from s... more The ecosystem of the Gulf of Finland is currently dominated by internal phosphorus loading from sediments. The internal load is highly redox sensitive, and its successful modelling on basin-wide scale requires a simplified description of the sediment process. We present here an approach in which redox-sensitive sediment processes are directly linked to the decomposition of carbon instead of the oxygen concentration in near-bottom water. Mineralisation of organic carbon is known to be the major factor controlling sediment nutrient cycling, including denitrification and Fe(III) oxide reduction, giving rise to high phosphorus fluxes from anoxic sediments.
Natural resources are vital to people along the Mekong as the livelihood of most of the people de... more Natural resources are vital to people along the Mekong as the livelihood of most of the people depend to large extent on natural ecosystems, especially in the poorest countries Cambodia and Lao PDR. One of the most important parts of the Mekong system is the Tonle Sap Lake in Cambodia being the main source of animal protein for Cambodia and working as a natural reservoir for the Lower Mekong Basin. The Tonle Sap is also a significant breeding ground for many of the Mekong fish species.
... proper model for water quality in northern reservoirs. As a practical challenge, the model wa... more ... proper model for water quality in northern reservoirs. As a practical challenge, the model was to predict and help optimize the water quality effects of a scheduled third reservoir, Vuotos (Fig. 1). In 1988-92 the model development ...
... simulation of pollutants transport in the Abu-Qir Bay, East Alexandria, Egypt E. Al-Hogaraty^... more ... simulation of pollutants transport in the Abu-Qir Bay, East Alexandria, Egypt E. Al-Hogaraty^'*, W. Hamza^ J. Koponen J. Sarkkula^ and Alam El-Din ... 5. Lead In Abu-Qir Bay, the particulate form of lead was dominant in both surface and bottom water layers (Younes et al., 1997 ...
The three-dimensional water quality and flow model was used to simulate phytoplankton biomass and... more The three-dimensional water quality and flow model was used to simulate phytoplankton biomass and dissolved nutrient concentrations in the Gulf of Finland. In the model, transport of nutrients is based on calculated wind and river flow-induced currents. Water quality data from two points off the Finnish coast were used for the model calibration.
Riverbank erosion is a natural process, but often human activities can have a significant impact ... more Riverbank erosion is a natural process, but often human activities can have a significant impact on the rates of morphological change. This paper aims to assess bank erosion problems in the Vientiane-Nong Khai section of the Mekong River, where the Mekong borders Thailand and Lao PDR. The study provides new and more accurate information about recent riverbank movement rates. The bank movement rates are quantified using two Hydrographic Atlases dated 1961 and 1992, derived originally from aerial photos and a field survey, and SPOT5 satellite images acquired on 4 December 2004 and 28 April 2005 with a resolution of 2.5 m in natural colours. Bank erosion and accretion rates on the left (Lao PDR) and right (Thailand) banks of the Mekong are analysed for two time periods: 1961-1992 and 1992-2005, respectively. The quantified average bank erosion rates were found to be slow, ranging from 0.8 to 1.0 m/a for the first and second analysis period, respectively. These average annual erosion rates are only 0.1% of the channel width, which is very low on a global scale. However, erosion rates were much higher for the islands in the river, 2.4 and 4.8 m/a for the two time periods. The quantified accretion for the main banks was 0.4 m/a during 1961-1992 and 0.7 m/a during 1992-2005, which for the islands increased from 0.6 to 6.4 m/a from the first to the second period. r
Integrated Water Resources Management has been identified as one of the basic water resources rel... more Integrated Water Resources Management has been identified as one of the basic water resources related policy approaches in several recent important commitments and recommendations including the Johannesburg Summit and World Water Forums. Recognizing that IWRM is largely still a theoretical concept with not much sound scientific research, our objective is to investigate how the IWRM process in the Mekong Basin is institutionalised, and implemented in practice. We focus on the Cambodia's Great Lake, the Tonle Sap. Of particular interest are the bottlenecks of IWRM, both those that are within the water sector and those that relate to various, more general development tendencies.
International Journal of Water Resources Development, 2006
The monsoon floods of the Mekong River are a key driver of the Tonle Sap Lake ecosystem. This pul... more The monsoon floods of the Mekong River are a key driver of the Tonle Sap Lake ecosystem. This pulsing system together with a large floodplain, rich biodiversity and high annual sedimentation and nutrient fluxes from the Mekong makes the lake one of the most productive fresh water ecosystems in the world. The livelihoods of people living in and around the Tonle Sap are strongly dependent on the lake's natural resources. An integrated modelling system, supported with primary data collection and analysis, has been ...
1] Hydraulic erosion of bank toe materials is the dominant factor controlling the long-term rate ... more 1] Hydraulic erosion of bank toe materials is the dominant factor controlling the long-term rate of riverbank retreat. In principle, hydraulic bank erosion can be quantified using an excess shear stress model, but difficulties in estimating input parameters seriously inhibit the predictive accuracy of this approach. Herein a combination of analytical modeling and novel field measurement techniques is employed to improve the parameterization of an excess shear stress model as applied to the Lower Mekong River. Boundary shear stress is estimated using a model Smith, 2006a, 2006b) for flow over the irregular bank topography that is characteristic of fine-grained riverbanks. Bank erodibility parameters were obtained using a cohesive strength meter . The new model was used to estimate annual bank erosion rates via integration across the Mekong's annual flow regime. Importantly, the simulations represent the first predictions of hydraulic bank erosion that do not require recourse to calibration, thereby providing a stronger physical basis for the simulation of bank erosion. Model predictions, as evaluated by comparing simulated annual rates of bank toe retreat with estimates of bank retreat derived from analysis of aerial photographs and satellite imagery, indicate a tendency to overpredict erosion (root-mean-square error equals ±0.53 m/yr). Form roughness induced by bank topographic features is shown to be a major component (61%-85%) of the spatially averaged total shear stress, and as such it can be viewed as an important factor that self-limits bank erosion. Citation: Darby, S. E., H. Q. Trieu, P. A. Carling, J. Sarkkula, J. Koponen, M. Kummu, I. Conlan, and J. Leyland (2010), A physically based model to predict hydraulic erosion of fine-grained riverbanks: The role of form roughness in limiting erosion,
The Tonle Sap Lake and floodplains in the heart of Cambodia contain the largest continuous areas ... more The Tonle Sap Lake and floodplains in the heart of Cambodia contain the largest continuous areas of natural wetlands habitats remaining in the Mekong system, while being the largest permanent freshwater body in Southeast Asia. Tonle Sap is a crucially important source for food and living in Cambodia. More than one million people live in the immediate surroundings of the Tonle Sap Lake and wetlands, being the poorest ones in Cambodia, and highly dependent on agriculture and fisheries. An important phosphorus source of the mainly phosphorus limited aquatic ecosystem is the sediment carried by the flood. Mekong Upstream developments, like construction of dams may lead, and has already led, to significant trapping of sediments and nutrients. This would dramatically reduce the productivity of the Tonle Sap system. The 3D mathematical model has been set up for Tonle Sap Lake for simulating water levels and currents, inundation of the floodplain, suspended sediment transport and sedimentation, dissolved oxygen as well as nutrients and algal growth (chlorophyll-a) to understand the ecosystem processes and the possible changes in it due to the upstream development.
Helsinki is located on the southern coast of Finland by the Baltic Sea. The ecological state of t... more Helsinki is located on the southern coast of Finland by the Baltic Sea. The ecological state of the archipelago in front of Helsinki is affected by several factors. The effects of local point and scattered loads are mixed with the transboundary effects from neighbouring countries and atmospheric deposition. Municipal waste waters of 800 000 inhabitants of the capital area are released outside the archipelago into the open Gulf of Finland (GoF). In addition, river Vantaanjoki is transporting load originating from agriculture, industry and settlements of the drainage area to the shores of Helsinki. Toxic algal blooms and annoying filamentous algal mats have become a problem to the users of the coastal zone.
Natural resources are vital to people along the Mekong as the livelihood of most of the people de... more Natural resources are vital to people along the Mekong as the livelihood of most of the people depend to large extent on natural ecosystems, especially in the poorest countries Cambodia and Lao PDR. One of the most important parts of the Mekong system is the Tonle Sap Lake in Cambodia being the main source of animal protein for Cambodia and working as a natural reservoir for the Lower Mekong Basin. The Tonle Sap is also a significant breeding ground for many of the Mekong fish species.
One of the most visible symptoms of eutrophication in the Gulf of Finland is blooms of unattached... more One of the most visible symptoms of eutrophication in the Gulf of Finland is blooms of unattached filamentous algae. This decomposing algal biomass causes serious nuisance problems for recreational uses of the coastal zone, particularly when cast ashore. The nutrient availability for these macroscopic filamentous algae is regulated by a superior competitor, the phytoplankton. Nutrients are left for the weaker competitor only when the conditions are not suitable for the growth of phytoplankton. This happens during vertical mixing of the water column. The lack of stratification prevents the formation of phytoplankton blooms, but does not limit the growth of filamentous algae when still growing attached to the bottom. A simple growth model was developed to describe the growth and biomass of filamentous algae. In the absence of suitable nutrient measurements, the model was linked to a 3D-ecohydrodynamic model which generated the nutrient input data. The model was calibrated with three-year monitoring data of filamentous algal biomass at one location. Validation was carried out with one-year monitoring data from an adjacent location. The model was able to describe the number of biomass peaks and their timing with good accuracy. After further development, the filamentous algal model will be used as one of the management tools for the evaluation of the sustainable nutrient load to the Gulf of Finland.
... proper model for water quality in northern reservoirs. As a practical challenge, the model wa... more ... proper model for water quality in northern reservoirs. As a practical challenge, the model was to predict and help optimize the water quality effects of a scheduled third reservoir, Vuotos (Fig. 1). In 1988-92 the model development ...
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Papers by Jorma Koponen