scholarly journals Assessing Climate Change Impacts on River Flows in the Tonle Sap Lake Basin, Cambodia

Water ◽  
2019 ◽  
Vol 11 (3) ◽  
pp. 618 ◽  
Author(s):  
Chantha Oeurng ◽  
Thomas Cochrane ◽  
Sarit Chung ◽  
Mathias Kondolf ◽  
Thanapon Piman ◽  
...  
Keyword(s):  
Climate Change ◽  
General Circulation ◽  
Rapid Development ◽  
Dry Season ◽  
Freshwater Ecosystem ◽  
Lake Basin ◽  
River Flows ◽  
Water Flows ◽  
Tonle Sap Lake ◽  
Tonle Sap

The Tonle Sap is the most fertile and diverse freshwater ecosystem in Southeast Asia, receiving nurturing water flows from the Mekong and its immediate basin. In addition to rapid development in the Tonle Sap basin, climate change may threaten natural flow patterns that sustain its diversity. The impacts of climate change on river flows in 11 sub-basins contributing to the Tonle Sap Lake were assessed using the Soil and Water Assessment Tool (SWAT) model to quantify the potential magnitude of future hydrological alterations. Projected river flows from three General Circulation Models (GFDL-CM3, GISS-E2-R-CC and IPSL-CM5A-MR) for three time horizons (2030s, 2060s and 2090s) indicate a likely decrease in both the wet and dry season flows. The mean annual projected flow reductions range from 9 to 29%, 10 to 35% and 7 to 41% for the 2030s, 2060s and 2090s projections, respectively. Moreover, a decrease in extreme river flows (Q5 and Q95) was also found, which implies there could be a decline in flood magnitudes and an increase in drought occurrences throughout the basin. The results of this study provide insight for water resources planning and adaptation strategies for the river ecosystems during the dry season, when water flows are projected to decrease.

scholarly journals An objective tropical Atlantic sea surface temperature gradient index for studies of south Amazon dry-season climate variability and change

2008 ◽  
Vol 363 (1498) ◽  
pp. 1761-1766 ◽  
Author(s):  
Peter Good ◽  
Jason A Lowe ◽  
Mat Collins ◽  
Wilfran Moufouma-Okia
Keyword(s):  
Climate Change ◽  
Surface Temperature ◽  
Sea Surface Temperature ◽  
General Circulation ◽  
Southern Oscillation ◽  
Circulation Model ◽  
Dry Season ◽  
Sea Surface ◽  
Tropical Atlantic ◽  
Sst Gradient

Future changes in meridional sea surface temperature (SST) gradients in the tropical Atlantic could influence Amazon dry-season precipitation by shifting the patterns of moisture convergence and vertical motion. Unlike for the El Niño-Southern Oscillation, there are no standard indices for quantifying this gradient. Here we describe a method for identifying the SST gradient that is most closely associated with June–August precipitation over the south Amazon. We use an ensemble of atmospheric general circulation model (AGCM) integrations forced by observed SST from 1949 to 2005. A large number of tropical Atlantic SST gradient indices are generated randomly and temporal correlations are examined between these indices and June–August precipitation averaged over the Amazon Basin south of the equator. The indices correlating most strongly with June–August southern Amazon precipitation form a cluster of near-meridional orientation centred near the equator. The location of the southern component of the gradient is particularly well defined in a region off the Brazilian tropical coast, consistent with known physical mechanisms. The chosen index appears to capture much of the Atlantic SST influence on simulated southern Amazon dry-season precipitation, and is significantly correlated with observed southern Amazon precipitation. We examine the index in 36 different coupled atmosphere–ocean model projections of climate change under a simple compound 1% increase in CO 2 . Within the large spread of responses, we find a relationship between the projected trend in the index and the Amazon dry-season precipitation trends. Furthermore, the magnitude of the trend relationship is consistent with the inter-annual variability relationship found in the AGCM simulations. This suggests that the index would be of use in quantifying uncertainties in climate change in the region.

scholarly journals Future changes in Mekong River hydrology: impact of climate change and reservoir operation on discharge

2012 ◽  
Vol 9 (5) ◽  
pp. 6569-6614 ◽  
Author(s):  
H. Lauri ◽  
H. de Moel ◽  
P. J. Ward ◽  
T. A. Räsänen ◽  
M. Keskinen ◽  
...  
Keyword(s):  
Climate Change ◽  
Reservoir Operation ◽  
General Circulation ◽  
General Circulation Models ◽  
Dry Season ◽  
Mekong River ◽  
Cumulative Impacts ◽  
Cumulative Impact ◽  
Impacts Of Climate Change ◽  
Hydropower Reservoirs

Abstract. The transboundary Mekong River is facing two on-going changes that are estimated to significantly impact its hydrology and the characteristics of its exceptional flood pulse. The rapid economic development of the riparian countries has led to massive plans for hydropower construction, and the projected climate change is expected to alter the monsoon patterns and increase temperature in the basin. The aim of this study is to assess the cumulative impact of these factors on the hydrology of the Mekong within next 20–30 yr. We downscaled output of five General Circulation Models (GCMs) that were found to perform well in the Mekong region. For the simulation of reservoir operation, we used an optimisation approach to estimate the operation of multiple reservoirs, including both existing and planned hydropower reservoirs. For hydrological assessment, we used a distributed hydrological model, VMod, with a grid resolution of 5 km × 5 km. In terms of climate change's impact to hydrology, we found a high variation in the discharge results depending on which of the GCMs is used as input. The simulated change in discharge at Kratie (Cambodia) between the baseline (1982–1992) and projected time period (2032–2042) ranges from −11% to +15% for the wet season and −10% to +13% for the dry season. Our analysis also shows that the changes in discharge due to planned reservoir operations are clearly larger than those simulated due to climate change: 25–160% higher dry season flows and 5–24% lower flood peaks in Kratie. The projected cumulative impacts follow rather closely the reservoir operation impacts, with an envelope around them induced by the different GCMs. Our results thus indicate that within the coming 20–30 yr, the operation of planned hydropower reservoirs is likely to have a larger impact on the Mekong hydrograph than the impacts of climate change, particularly during the dry season. On the other hand, climate change will increase the uncertainty of the estimated hydropower impacts. Consequently, both dam planners and dam operators should pay better attention to the cumulative impacts of climate change and reservoir operation to the aquatic ecosystems, including the multibillion-dollar Mekong fisheries.

scholarly journals Assessing the Potential for Small-Scale Aquaculture in Cambodia

2018 ◽  
Author(s):  
Robert B. Richardson ◽  
Murari Suvedi
Keyword(s):  
Food Security ◽  
Household Food Security ◽  
Small Scale ◽  
Lake Ecosystem ◽  
Lake Basin ◽  
Fishing Pressure ◽  
Commercial Fish ◽  
Tonle Sap Lake ◽  
Household Food ◽  
Tonle Sap

Fisheries in Cambodia play an important role in supporting household food security and livelihoods throughout the country. Inland fisheries production is largely dependent on numerous ecosystem services, particularly the flood waters of the Tonle Sap Lake basin, which has been degraded from increased fishing pressure because of population growth and a rising demand for fish. To address the dual problem of food insecurity and overfishing, an integrated food security and climate change program involved the promotion of small-scale aquaculture through semi-intensive pond management. The objective of this study is to examine perceptions of small-scale aquaculture by participants in this program in order to assess the potential for aquaculture to contribute to household food security and conservation of the Tonle Sap Lake ecosystem. Focus group discussions and a household survey were conducted among current and previous fish farmers. Results demonstrate that most farmers continue to practice small-scale aquaculture as a means to supplement household food availability and income. Numerous barriers to adoption of small-scale aquaculture were identified, including access to water, prices of commercial fish feed, selling price of fish in markets, and concerns about profitability. Seasonal water scarcity is the most prominent challenge in promoting aquaculture technologies, so aquaculture development should be expanded in areas where there are abundant supplies of water, or where use of water storage techniques are feasible. Aquaculture technology appears to have the potential to contribute to food security, nutrition, and household income, and the expansion of the practice of small-scale aquaculture has the potential to reduce fishing pressure on the wild fisheries of the Tonle Sap Lake.

scholarly journals Impacts of climate change on environmental flows in West Africa's Upper Niger Basin and the Inner Niger Delta

2021 ◽  
Author(s):  
Julian R. Thompson ◽  
Cédric L. R. Laizé ◽  
Michael C. Acreman ◽  
Andrew Crawley ◽  
Daniel G. Kingston
Keyword(s):  
Climate Change ◽  
Niger Delta ◽  
General Circulation ◽  
Environmental Flows ◽  
Circulation Model ◽  
Freshwater Ecosystem ◽  
Low Flows ◽  
Ensemble Mean ◽  
Medium Risk ◽  
High Flows

Abstract Modified water regimes due to climate change are likely to be a major cause of freshwater ecosystem alteration. General Circulation Model (GCM)-related uncertainty in environmental flows at 12 gauging stations in the Upper Niger Basin and flooding within the Inner Niger Delta is assessed using the Ecological Risk due to the Flow Alteration method and a hydrological model forced with projections from 12 GCM groups for RCP 4.5 in the 2050s and 2080s. Risk varies between GCM groups and stations. It increases into the future and is larger for changes in low flows compared to high flows. For the ensemble mean, a small minority of GCM groups projects no risk for high flows in the 2050s (low risk otherwise). This reverses for the 2080s. For low flows, no risk is limited to three stations in the 2050s and one station in the 2080s, the other experience either low or medium risk. There is greater consistency in the risk of change in flood extent, especially in the dry season (medium risk for all groups and the ensemble mean). Some (low or medium) risk of change in peak annual inundation is projected for most groups. Changing flood patterns have implications for wetland ecology and ecosystem services.

scholarly journals How Local People Use Their Indigenous Knowledge to Respond to Floods and Droughts: A Case Study of Tonle Sap Lake Community, Cambodia

2021 ◽  
Author(s):  
◽  
Sopheak Seng
Keyword(s):  
Climate Change ◽  
Indigenous Knowledge ◽  
Local Communities ◽  
Adaptation Strategies ◽  
Structured Interviews ◽  
Local Livelihoods ◽  
Lake Region ◽  
Tonle Sap Lake ◽  
Tonle Sap ◽  
Floods And Droughts

<p>This thesis investigates the impacts of floods and droughts in the Tonle Sap Lake region and examines to what extent the local communities’ indigenous knowledge (IK) is used to deal with floods and droughts. The thesis begins by exploring the Tonle Sap Lake communities’ perceptions of climate change, especially floods and droughts and their impacts on local livelihoods. It then examines how the communities have used their IK to develop livelihood adaptation methods to cope with floods and droughts. To conduct this study, a qualitative methodology was adopted using semi-structured interviews, and non-participant and unstructured observation as the main methods. The semi-structured interviews were conducted with local people and local authorities from two communities, and NGO staff.   The study found that the intensity of floods and droughts in the Tonle Sap Lake region has increased in the last few years. Floods and droughts have threatened local livelihoods and food security. To mitigate the effects of floods and droughts, the local communities in this region have developed various livelihood adaptation strategies to adapt to the hazards. The communities appeared to use both IK and technologies for their adaptation strategies. IK is seen as an invaluable local community asset in developing livelihood adaptation methods.   Although a mixture of IK and new knowledge has been used to develop various adaptation strategies, the sufficiency of the adaptation is still limited. The current severity of climate change is seen to limit the local communities’ response capacities. To strengthen the communities’ adaptation capacity, contribution and involvement from non-governmental organisations and the government in developing climate change adaptation policy at a local level are essential.</p>

scholarly journals Assessment of the Impact of Climate Change on Snow Distribution and River Flows in a Snow-Dominated Mountainous Watershed in the Western Hindukush–Himalaya, Afghanistan

Hydrology ◽  
2020 ◽  
Vol 7 (4) ◽  
pp. 74
Author(s):  
Abdul Haseeb Azizi ◽  
Yoshihiro Asaoka
Keyword(s):  
Climate Change ◽  
Snow Cover ◽  
21St Century ◽  
General Circulation ◽  
River Flow ◽  
General Circulation Models ◽  
Snow Cover Area ◽  
River Flows ◽  
Late 21St Century ◽  
The Impact

Projected snow cover and river flows are important for planning and managing water resources in snow-dominated basins of the Himalayas. To quantify the impacts of climate change in the data scarce Panjshir River basin of Afghanistan, this study simulated present and future snow cover area (SCA) distributions with the snow model (SM), and river flows with the snowmelt runoff model (SRM). The SRM used the degree-day factor and precipitation gradient optimized by the SM to simulate river flows. Temperature and precipitation data from eight kinds of general circulation models (GCMs) were used for bias correction. The SM and SRM were first calibrated and validated using 2009–2015 data, and then bias-corrected future climate data were input to the models to simulate future SCA and river flows. Under both the representative concentration pathways (RCP) 4.5 and 8.5, the annual average SCA and river flow were projected to decrease in the mid and late 21st century, although seasonal increases were simulated in some instances. Uncertainty ranges in projected SCA and river flow under RCP 8.5 were small in the mid 21st century and large in the late 21st century. Therefore, climate change is projected to alter high-altitude stream sources in the Hindukush mountains and reduce the amount of water reaching downstream areas.

scholarly journals Future changes in Mekong River hydrology: impact of climate change and reservoir operation on discharge

2012 ◽  
Vol 16 (12) ◽  
pp. 4603-4619 ◽  
Author(s):  
H. Lauri ◽  
H. de Moel ◽  
P. J. Ward ◽  
T. A. Räsänen ◽  
M. Keskinen ◽  
...  
Keyword(s):  
Climate Change ◽  
Reservoir Operation ◽  
General Circulation ◽  
General Circulation Models ◽  
Dry Season ◽  
Mekong River ◽  
Cumulative Impacts ◽  
Cumulative Impact ◽  
Impacts Of Climate Change ◽  
Hydropower Reservoirs

Abstract. The transboundary Mekong River is facing two ongoing changes that are expected to significantly impact its hydrology and the characteristics of its exceptional flood pulse. The rapid economic development of the riparian countries has led to massive plans for hydropower construction, and projected climate change is expected to alter the monsoon patterns and increase temperature in the basin. The aim of this study is to assess the cumulative impact of these factors on the hydrology of the Mekong within next 20–30 yr. We downscaled the output of five general circulation models (GCMs) that were found to perform well in the Mekong region. For the simulation of reservoir operation, we used an optimisation approach to estimate the operation of multiple reservoirs, including both existing and planned hydropower reservoirs. For the hydrological assessment, we used a distributed hydrological model, VMod, with a grid resolution of 5 km × 5 km. In terms of climate change's impact on hydrology, we found a high variation in the discharge results depending on which of the GCMs is used as input. The simulated change in discharge at Kratie (Cambodia) between the baseline (1982–1992) and projected time period (2032–2042) ranges from −11% to &amp;plus;15% for the wet season and −10% to &amp;plus;13% for the dry season. Our analysis also shows that the changes in discharge due to planned reservoir operations are clearly larger than those simulated due to climate change: 25–160% higher dry season flows and 5–24% lower flood peaks in Kratie. The projected cumulative impacts follow rather closely the reservoir operation impacts, with an envelope around them induced by the different GCMs. Our results thus indicate that within the coming 20–30 yr, the operation of planned hydropower reservoirs is likely to have a larger impact on the Mekong hydrograph than the impacts of climate change, particularly during the dry season. On the other hand, climate change will increase the uncertainty of the estimated reservoir operation impacts: our results indicate that even the direction of the flow-related changes induced by climate change is partly unclear. Consequently, both dam planners and dam operators should pay closer attention to the cumulative impacts of climate change and reservoir operation on aquatic ecosystems, including the multibillion-dollar Mekong fisheries.

scholarly journals Impacts of future deforestation and climate change on the hydrology of the Amazon basin: a multi-model analysis with a new set of land-cover change scenarios

2016 ◽  
Author(s):  
Matthieu Guimberteau ◽  
Philippe Ciais ◽  
Agnès Ducharne ◽  
Juan Pablo Boisier ◽  
Ana Paula Dutra Aguiar ◽  
...  
Keyword(s):  
Climate Change ◽  
Land Cover ◽  
Land Cover Change ◽  
River Discharge ◽  
General Circulation ◽  
Amazon Basin ◽  
Dry Season ◽  
Forest Area ◽  
Basin Scale ◽  
Concentration Changes

Abstract. Neglecting any atmospheric feedback to precipitation, deforestation in Amazon, i.e., replacement of trees by shallow rooted short vegetation, is expected to decrease evapotranspiration (ET). Under energy-limited conditions, this process should lead to higher soil moisture and a consequent increase in river discharge. The magnitude and sign of the response of ET to deforestation depends both on land-cover change (LCC), and on climate and CO2 concentration changes in the future. Using three regional LCC scenarios recently established for the Brazilian and Bolivian Amazon, we investigate the combined impacts of deforestation and climate change on the surface hydrology of the Amazon basin for this century at sub-basin scale. For each LCC scenario, three land surface models (LSMs), LPJmL-DGVM, INLAND-DGVM and ORCHIDEE, are forced by bias-corrected climate simulated by three General Circulation Models (GCMs) for different scenarios of the IPCC 4th Assessment Report (AR4). The GCM results indicate that by 2100, without deforestation, the temperature will have increased by a mean of 3.3 °C (a range of 1.7 to 4.5 °C) over the Amazon basin, intensifing the regional water cycle, whereby precipitation, ET and runoff increase by 8.5, 5.0 and 14 %, respectively. However, under this same scenario in south-east Amazonia, precipitation decreases by 10 % at the end of the dry season and the three LSMs estimate a 6 % decrease of ET, which does not compensate for lower precipitation. Runoff in southeastern Amazonia decreases by 22 %, reducing minimum river discharge from the Rio Tapajós catchment by 31 % in 2100. The low LCC scenario projects a 7 % decline in the area of Amazonian forest by 2100, as compared to 2009; for the high LCC scenario the projection is a 34 % decline. In the extreme deforestation scenario, forest loss partly offsets (−2.5 %) the positive effect of climate change on increasing ET and slightly amplifies (+3.0 %) the increase of runoff. Effects of deforestation are more pronounced in the southern part of the Amazon basin, in particular in the Rio Madeira catchment where up to 56 % of the 2009 forest area is lost. The effect of deforestation on water budgets is more severe at the end of the dry season in the Tapajós and the Xingu catchments where the decrease of ET due to climate change is amplified by forest area loss. Deforestation enhances runoff during this period (+35 %) offsetting the negative effect of climate change (−22 %), and balances the decrease of low flows in the Rio Tapajós.

Water, livelihoods and climate change adaptation in the Tonle Sap Lake area, Cambodia: learning from the past to understand the future

2010 ◽  
Vol 1 (1) ◽  
pp. 87-101 ◽  
Author(s):  
Paula Nuorteva ◽  
Marko Keskinen ◽  
Olli Varis
Keyword(s):  
Climate Change ◽  
Adaptive Capacity ◽  
Climate Change Adaptation ◽  
Environmental Changes ◽  
Land Use Changes ◽  
Rural Livelihoods ◽  
Flood Pulse ◽  
Lake Area ◽  
Tonle Sap Lake ◽  
Tonle Sap

The changing environment is expected to intensify the challenges that people in developing countries are facing, particularly among the groups whose livelihoods depend on natural resources. The adaptive capacity of livelihoods largely defines the extent to which people can cope with future environmental changes, whether caused by climate change or other factors such as land use changes and water resources development. This article analyses the resilience and adaptive capacity of rural livelihoods around Cambodia's Tonle Sap Lake, an exceptional lake-floodplain system dominated by flood pulse. The research findings demonstrate that despite the people's tradition of adapting to the remarkable seasonal variation of water and related resources, their capacity to adapt to unusual environmental changes is weak, with the poorest being clearly the most vulnerable group. Reasons for the weak resilience include villages' relatively homogenous livelihood structures, unjust governance practices, increasing inequality and the lack of opportunities for livelihood diversification. It is concluded that while climate change is likely to pose a remarkable challenge to people's livelihoods in the longer term, climate change adaptation activities should also take into account other environmental changes. Equally critical is the understanding of the broader socio-political context and its dynamics in increasing—and decreasing—livelihood resilience.

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