Global climate change has received much attention
worldwide in the scientific as well as in the p... more Global climate change has received much attention worldwide in the scientific as well as in the political community, indicating that changes in precipitation, extreme droughts and floods may increasingly threaten many regions. Drought is a natural phenomenon that causes social, economical and environmental damage to society. In this study, we assess the drought intensity and severity and the groundwater potential to be used as a supplementary source of water to mitigate drought impacts in the Crocodile River catchment, a water-stressed sub-catchment of the Incomati River catchment in South Africa. The research methodology consists of three parts. First, the spatial and temporal variation of the meteorological and hydrological drought severity and intensity over the catchment were evaluated. The Standardized Precipitation Index (SPI) was used to analyse the meteorological drought and the Standardized Runoff Index (SRI) was used for the hydrological drought. Second, the water deficit in the catchment during the drought period was computed using a simple water balance method. Finally, a groundwater model was constructed in order to assess the feasibility of using groundwater as an emergency source for drought impact mitigation. Results show that the low-rainfall areas are more vulnerable to severe meteorological droughts (lower and upper crocodile). Moreover, the most water stressed subcatchments with high level of water uses but limited storage, such as the Kaap located in the middle catchment and the Lower Crocodile sub-catchments, are more vulnerable to severe hydrological droughts. The analysis of the potential groundwater use during droughts showed that a deficit of 97Mm3 yr1 could be supplied from groundwater without considerable adverse impacts on the river base flow and groundwater storage. Abstraction simulations for different scenarios of extremely severe droughts reveal that it is possible to use groundwater to cope with the droughts in the catchment. However, local groundwater exploitation in Nelspruit and White River sub-catchment will cause large drawdowns (> 10 m) and high base flow reduction (> 20 %). This case study shows that conjunctive water management of groundwater and surface water resources is necessary to mitigate the impacts of droughts.
Ensemble hydrological predictions are normally obtained by forcing hydrological models with ensem... more Ensemble hydrological predictions are normally obtained by forcing hydrological models with ensembles of atmospheric forecasts produced by Numerical weather prediction models. To be of practical value to water users, such forecasts should not only be sufficiently skilful, they should also provide information that is relevant to the decisions 5 end users make. The semi-arid Limpopo basin in Southern Africa has experienced severe droughts in the past, resulting in crop failures, high economic losses and the need for humanitarian aid. In this paper we address the seasonal prediction of hydrological drought for the Limpopo river basin by testing three proposed forecasting systems (FS) that can provide operational guidance to dam operators and water man-10 agers within the basin at the seasonal time scale. All three FS include a distributed hydrological model of the basin, and are forced with either (i) a global atmospheric model forecast (ECMWF seasonal forecast system -S4), (ii) the commonly applied Ensemble Streamflow Prediction approach (ESP) using resampled historical data, or (iii) a conditional ESP approach (ESPcond), which is conditional on the ENSO signal. We determine the skill of the three systems in predicting drought indices and streamflow. We also assess the skill of the model in predicting indicators that are meaningful to the local end users in the basin. FS_S4 shows moderate skill for all lead times (3, 4, and 5 months) and aggregation periods. FS_ESP also performs better than climatology for the shorter lead times, but with a lower skill than FS_S4. FS_ESPcond shows skill 20 in between the other two FS, though its skill is shown to be more robust. The skills of FS_ESP and FS_ESPcond reduce rapidly with increasing lead time. Both FS_S4 and FS_ESPcond show good potential for seasonal hydrological drought forecasting in the Limpopo river basin, which is encouraging in the context of providing better operational guidance to water users.
In the present study, we developed a catchment hydrological model which can be used to inform wat... more In the present study, we developed a catchment hydrological model which can be used to inform water resources planning and decision making for better management of the Migina Catchment (257.4 km 2 ). The semidistributed hydrological model HEC-HMS (Hydrologic Engineering Center -the Hydrologic Modelling System) (version 3.5) was used with its soil moisture accounting, unit hydrograph, liner reservoir (for baseflow) and Muskingum-Cunge (river routing) methods. We used rainfall data from 12 stations and streamflow data from 5 stations, which were collected as part of this study over a period of 2 years (May 2009 and June 2011). The catchment was divided into five subcatchments. The model parameters were calibrated separately for each sub-catchment using the observed streamflow data. Calibration results obtained were found acceptable at four stations with a Nash-Sutcliffe model efficiency index (NS) of 0.65 on daily runoff at the catchment outlet. Due to the lack of sufficient and reliable data for longer periods, a model validation was not undertaken. However, we used results from tracer-based hydrograph separation from a previous study to compare our model results in terms of the runoff components. The model performed reasonably well in simulating the total flow volume, peak flow and timing as well as the portion of direct runoff and baseflow. We observed considerable disparities in the parameters (e.g. groundwater storage) and runoff components across the five sub-catchments, which provided insights into the different hydrological processes on a sub-catchment scale. We conclude that such disparities justify the need to consider catchment subdivisions if such parameters and components of the water cycle are to form the base for decision making in water resources planning in the catchment.
Satellite radar altimetry measures the time required for a pulse to travel from the satellite ant... more Satellite radar altimetry measures the time required for a pulse to travel from the satellite antenna to the earth’s surface and back to the satellite receiver. Altimetry on inland lakes generally shows some deviation from in situ level measurements. The deviation is attributed to the geographically varying corrections applied to account for atmospheric effects on radar waves. This study was
As well-known of the largest flat low-lying and fertile delta in the world, the Mekong River Delt... more As well-known of the largest flat low-lying and fertile delta in the world, the Mekong River Delta experiences annual widespread flooding where mainly provides primary sources for about 17 million habitants, of which, suspended sediment load play an important role in carrying contaminants, nutrients, etc.. used for agriculture cultivation as well as important factors for geomorphological phenomena in rivers. In current decades, the changes of water availability under climate change are entailing the changes of hydrodynamic on rivers, influencing to sediment transport, but observed sediment data is lacking. Moreover, after natural floodplains, the sediment deposition have replaced by dense river systems as resulting in floodplain compartments protected by embankments. The cropping seasons depend on flood events and sediment associated nutrient input for agricultural productivity. However, sediment quantitative information and these influences on changes of hydrodynamic pay less attention. This study is aimed to investigate impacts of water availability and sea level rise on sediment transport under anticipated scenarios. Therefore, the hydrodynamic model and sediment transport model -Mike 11 are applied for simulating sediment load processes on the Mekong Rivers. The simulated results of various upstream discharges and sea level rise based on anticipated scenarios will indicate the variability of sediment transport. The findings of outcomes are the concrete basis in contribution to propose sustainable measures for improving positive effects and restricting negative impacts on cultivation, guiding Mekong River Delta towards aspired benefits.
This paper evaluates the impact of climate change on sediment yield in the Nam Ou basin located i... more This paper evaluates the impact of climate change on sediment yield in the Nam Ou basin located in northern Laos. Future climate (temperature and precipitation) from four general circulation models (GCMs) that are found to perform well in the Mekong region and a regional circulation model (PRECIS) are downscaled using a delta change approach. The Soil and Water Assessment Tool (SWAT) is used to assess future changes in sediment flux attributable to climate change. Results indicate up to 3.0 • C shift in seasonal temperature and 27 % (decrease) to 41 % (increase) in seasonal precipitation. The largest increase in temperature is observed in the dry season while the largest change in precipitation is observed in the wet season. In general, temperature shows increasing trends but changes in precipitation are not unidirectional and vary depending on the greenhouse gas emission scenarios (GHGES), climate models, prediction period and season. The simulation results show that the changes in annual stream discharges are likely to range from a 17 % decrease to 66 % increase in the future, which will lead to predicted changes in annual sediment yield ranging from a 27 % decrease to about 160 % increase. Changes in intra-annual (monthly) discharge as well as sediment yield are even greater (−62 to 105 % in discharge and −88 to 243 % in sediment yield). A higher discharge and sediment flux are expected during the wet seasons, although the highest relative changes are observed during the dry months. The results indicate high uncertainties in the direction and magnitude of changes of discharge as well as sediment yields due to climate change. As the projected climate change impact on sediment varies remarkably between the different climate models, the uncertainty should be taken into account in both sediment management and climate change adaptation.
Evaporation is a key process in the water cycle with implications ranging, inter alia, from water... more Evaporation is a key process in the water cycle with implications ranging, inter alia, from water management to weather forecast and climate change assessments. The estimation of continental evaporation fluxes is complex and typically relies on continental-scale hydrological models or land-surface models. However, it appears that most global or continental-scale hydrological models underestimate evaporative fluxes in some regions of Africa, and as a result overestimate stream flow. Other studies suggest that landsurface models may overestimate evaporative fluxes. In this study, we computed actual evaporation for the African continent using a continental version of the global hydrological model PCR-GLOBWB, which is based on a water balance approach. Results are compared with other independently computed evaporation products: the evaporation results from the ECMWF reanalysis ERA-Interim and ERA-Land (both based on the energy balance approach), the MOD16 evaporation product, and the GLEAM product. Three other alternative versions of the PCR-GLOBWB hydrological model were also considered. This resulted in eight products of actual evaporation, which were compared in distinct regions of the African continent spanning different climatic regimes. Annual totals, spatial patterns and seasonality were studied and compared through visual inspection and statistical methods. The comparison shows that the representation of irrigation areas has an insignificant contribution to the actual evaporation at a continental scale with a 0.5 • spatial resolution when averaged over the defined regions. The choice of meteorological forcing data has a larger effect on the evapo-ration results, especially in the case of the precipitation input as different precipitation input resulted in significantly different evaporation in some of the studied regions. ERA-Interim evaporation is generally the highest of the selected products followed by ERA-Land evaporation. In some regions, the satellite-based products (GLEAM and MOD16) show a different seasonal behaviour compared to the other products. The results from this study contribute to a better understanding of the suitability and the differences between products in each climatic region. Through an improved understanding of the causes of differences between these products and their uncertainty, this study provides information to improve the quality of evaporation products for the African continent and, consequently, leads to improved water resources assessments at regional scale.
ABSTRACT To guarantee a safe flood defence in a changing environment, the adaptation to climate c... more ABSTRACT To guarantee a safe flood defence in a changing environment, the adaptation to climate change needs to be considered in the design of river dikes. However, the large uncertainty in the projections of future climate leads to varied estimations of future flood probability. How to cope with the uncertainties in future flood probability under climate change is an inevitable question in the adaptation. In this paper, the uncertainty introduced by climate projections was integrated into the ‘expected predictive flood probability’, and the risk-aversion attitude was introduced in the adaptation of river dikes. In detail, the uncertain effect of climate change on flood probability was represented by the uncertainty in the parameters of the probabilistic model. This parameter uncertainty was estimated based on the outputs from the GCMs participated in IPCC AR4. The parameter uncertainty estimated from different GCMs under selected scenarios was integrated into the expected predictive probability of flooding, which was used in the risk-aversion economic optimization. Different optimal results were obtained based on varied values of the risk-aversion index. The case of Bengbu Dike in China was studied as an example using the proposed approach. The results show that the uncertain effect of climate change causes an increase of optimal dike height but a decrease of the optimal safety level. The proposed approach enables decision makers to cope with the uncertain effects of climate change by adjusting their risk-aversion attitude.
Please cite this article as: Masih, I., Uhlenbrook, S., Maskey, S., Ahmad, M.D., Regionalization ... more Please cite this article as: Masih, I., Uhlenbrook, S., Maskey, S., Ahmad, M.D., Regionalization of a conceptual rainfall-runoff model based on similarity of the flow duration curve: A case study from the semi-arid Karkheh basin, Abstract 11
To guarantee a safe flood defence in a changing environment, the adaptation to climate change nee... more To guarantee a safe flood defence in a changing environment, the adaptation to climate change needs to be considered in the design of river dikes. However, the large uncertainty in the projections of future climate leads to varied estimations of future flood probability. How to cope with the uncertainties in future flood probability under climate change is an inevitable question in the adaptation. In this paper, the uncertainty introduced by climate projections was integrated into the 'expected predictive flood probability', and the risk-aversion attitude was introduced in the adaptation of river dikes. The uncertainty of climate change impact on flood probability was represented by the uncertainty in the parameters of the probabilistic model. This parameter uncertainty was estimated based on the outputs from the GCMs participated in IPCC AR4. The parameter uncertainty estimated from different GCMs under selected scenarios was integrated into the expected predictive probability of flooding, which was used in the risk-averse economic optimization. Different optimal results were obtained based on varied values of the risk-aversion index. A case of dike ring area in China was studied as an example using the proposed approach. The results show that the uncertainty of climate change increases the optimal dike height and decreases the optimal safety level. The proposed approach enables decision makers to cope with the climate change and the associated uncertainty by adjusting the risk-aversion level.
This paper presents a comprehensive review and analysis of the available literature and informati... more This paper presents a comprehensive review and analysis of the available literature and information on droughts to build a continental, regional and country level perspective on geospatial and temporal variation of droughts in Africa. The study is based on the review and analysis of droughts occurred during 1900-2013, as well as evidence available from past centuries based on studies on the lake sediment analysis, tree-ring chronologies and written and oral histories and future predictions from the global climate change models. Most of the studies based on instrumental records indicate that droughts have become more frequent, intense and widespread during the last 50 years. The extreme droughts of
ABSTRACT The study aimed at developing a tool to investigate the effect of prospective climate ch... more ABSTRACT The study aimed at developing a tool to investigate the effect of prospective climate change (until 2100) on hydrology and productivity of rain-fed crops (wheat Triticum L., maize Zea Mais L., and rice Oryza L.) in the Indrawati river basin, Nepal, Himalaya. Climate scenarios from 3 climate models (GCMs), namely CCSM4, EC-Earth and ECHAM6, each one under 3 different representative concentration pathways (RCPs) were fed to Soil and Water Assessment Tool (SWAT) and hydrological fluxes and crop yields were estimated for two time windows, i.e. half century (2045–2054) and end of century (2085–2094) against control run decade (1995–2004). The results foresee considerable potential changes of hydrological fluxes (from −26% to +37% yearly, with large difference seasonally and between models and RCPs), and potential changes of crop production (−36% to +18% for wheat, −17% to +4% for maize, and −17% to +12% for rice, again with differences between models and RCPs), also in term of yearly variability, potentially affecting food security. The CCSM4T model projected larger changes in hydrology and reduction in crop yields than other models. Wheat was found to be more vulnerable than maize and rice to climate change.
Global climate change has received much attention
worldwide in the scientific as well as in the p... more Global climate change has received much attention worldwide in the scientific as well as in the political community, indicating that changes in precipitation, extreme droughts and floods may increasingly threaten many regions. Drought is a natural phenomenon that causes social, economical and environmental damage to society. In this study, we assess the drought intensity and severity and the groundwater potential to be used as a supplementary source of water to mitigate drought impacts in the Crocodile River catchment, a water-stressed sub-catchment of the Incomati River catchment in South Africa. The research methodology consists of three parts. First, the spatial and temporal variation of the meteorological and hydrological drought severity and intensity over the catchment were evaluated. The Standardized Precipitation Index (SPI) was used to analyse the meteorological drought and the Standardized Runoff Index (SRI) was used for the hydrological drought. Second, the water deficit in the catchment during the drought period was computed using a simple water balance method. Finally, a groundwater model was constructed in order to assess the feasibility of using groundwater as an emergency source for drought impact mitigation. Results show that the low-rainfall areas are more vulnerable to severe meteorological droughts (lower and upper crocodile). Moreover, the most water stressed subcatchments with high level of water uses but limited storage, such as the Kaap located in the middle catchment and the Lower Crocodile sub-catchments, are more vulnerable to severe hydrological droughts. The analysis of the potential groundwater use during droughts showed that a deficit of 97Mm3 yr1 could be supplied from groundwater without considerable adverse impacts on the river base flow and groundwater storage. Abstraction simulations for different scenarios of extremely severe droughts reveal that it is possible to use groundwater to cope with the droughts in the catchment. However, local groundwater exploitation in Nelspruit and White River sub-catchment will cause large drawdowns (> 10 m) and high base flow reduction (> 20 %). This case study shows that conjunctive water management of groundwater and surface water resources is necessary to mitigate the impacts of droughts.
Ensemble hydrological predictions are normally obtained by forcing hydrological models with ensem... more Ensemble hydrological predictions are normally obtained by forcing hydrological models with ensembles of atmospheric forecasts produced by Numerical weather prediction models. To be of practical value to water users, such forecasts should not only be sufficiently skilful, they should also provide information that is relevant to the decisions 5 end users make. The semi-arid Limpopo basin in Southern Africa has experienced severe droughts in the past, resulting in crop failures, high economic losses and the need for humanitarian aid. In this paper we address the seasonal prediction of hydrological drought for the Limpopo river basin by testing three proposed forecasting systems (FS) that can provide operational guidance to dam operators and water man-10 agers within the basin at the seasonal time scale. All three FS include a distributed hydrological model of the basin, and are forced with either (i) a global atmospheric model forecast (ECMWF seasonal forecast system -S4), (ii) the commonly applied Ensemble Streamflow Prediction approach (ESP) using resampled historical data, or (iii) a conditional ESP approach (ESPcond), which is conditional on the ENSO signal. We determine the skill of the three systems in predicting drought indices and streamflow. We also assess the skill of the model in predicting indicators that are meaningful to the local end users in the basin. FS_S4 shows moderate skill for all lead times (3, 4, and 5 months) and aggregation periods. FS_ESP also performs better than climatology for the shorter lead times, but with a lower skill than FS_S4. FS_ESPcond shows skill 20 in between the other two FS, though its skill is shown to be more robust. The skills of FS_ESP and FS_ESPcond reduce rapidly with increasing lead time. Both FS_S4 and FS_ESPcond show good potential for seasonal hydrological drought forecasting in the Limpopo river basin, which is encouraging in the context of providing better operational guidance to water users.
In the present study, we developed a catchment hydrological model which can be used to inform wat... more In the present study, we developed a catchment hydrological model which can be used to inform water resources planning and decision making for better management of the Migina Catchment (257.4 km 2 ). The semidistributed hydrological model HEC-HMS (Hydrologic Engineering Center -the Hydrologic Modelling System) (version 3.5) was used with its soil moisture accounting, unit hydrograph, liner reservoir (for baseflow) and Muskingum-Cunge (river routing) methods. We used rainfall data from 12 stations and streamflow data from 5 stations, which were collected as part of this study over a period of 2 years (May 2009 and June 2011). The catchment was divided into five subcatchments. The model parameters were calibrated separately for each sub-catchment using the observed streamflow data. Calibration results obtained were found acceptable at four stations with a Nash-Sutcliffe model efficiency index (NS) of 0.65 on daily runoff at the catchment outlet. Due to the lack of sufficient and reliable data for longer periods, a model validation was not undertaken. However, we used results from tracer-based hydrograph separation from a previous study to compare our model results in terms of the runoff components. The model performed reasonably well in simulating the total flow volume, peak flow and timing as well as the portion of direct runoff and baseflow. We observed considerable disparities in the parameters (e.g. groundwater storage) and runoff components across the five sub-catchments, which provided insights into the different hydrological processes on a sub-catchment scale. We conclude that such disparities justify the need to consider catchment subdivisions if such parameters and components of the water cycle are to form the base for decision making in water resources planning in the catchment.
Satellite radar altimetry measures the time required for a pulse to travel from the satellite ant... more Satellite radar altimetry measures the time required for a pulse to travel from the satellite antenna to the earth’s surface and back to the satellite receiver. Altimetry on inland lakes generally shows some deviation from in situ level measurements. The deviation is attributed to the geographically varying corrections applied to account for atmospheric effects on radar waves. This study was
As well-known of the largest flat low-lying and fertile delta in the world, the Mekong River Delt... more As well-known of the largest flat low-lying and fertile delta in the world, the Mekong River Delta experiences annual widespread flooding where mainly provides primary sources for about 17 million habitants, of which, suspended sediment load play an important role in carrying contaminants, nutrients, etc.. used for agriculture cultivation as well as important factors for geomorphological phenomena in rivers. In current decades, the changes of water availability under climate change are entailing the changes of hydrodynamic on rivers, influencing to sediment transport, but observed sediment data is lacking. Moreover, after natural floodplains, the sediment deposition have replaced by dense river systems as resulting in floodplain compartments protected by embankments. The cropping seasons depend on flood events and sediment associated nutrient input for agricultural productivity. However, sediment quantitative information and these influences on changes of hydrodynamic pay less attention. This study is aimed to investigate impacts of water availability and sea level rise on sediment transport under anticipated scenarios. Therefore, the hydrodynamic model and sediment transport model -Mike 11 are applied for simulating sediment load processes on the Mekong Rivers. The simulated results of various upstream discharges and sea level rise based on anticipated scenarios will indicate the variability of sediment transport. The findings of outcomes are the concrete basis in contribution to propose sustainable measures for improving positive effects and restricting negative impacts on cultivation, guiding Mekong River Delta towards aspired benefits.
This paper evaluates the impact of climate change on sediment yield in the Nam Ou basin located i... more This paper evaluates the impact of climate change on sediment yield in the Nam Ou basin located in northern Laos. Future climate (temperature and precipitation) from four general circulation models (GCMs) that are found to perform well in the Mekong region and a regional circulation model (PRECIS) are downscaled using a delta change approach. The Soil and Water Assessment Tool (SWAT) is used to assess future changes in sediment flux attributable to climate change. Results indicate up to 3.0 • C shift in seasonal temperature and 27 % (decrease) to 41 % (increase) in seasonal precipitation. The largest increase in temperature is observed in the dry season while the largest change in precipitation is observed in the wet season. In general, temperature shows increasing trends but changes in precipitation are not unidirectional and vary depending on the greenhouse gas emission scenarios (GHGES), climate models, prediction period and season. The simulation results show that the changes in annual stream discharges are likely to range from a 17 % decrease to 66 % increase in the future, which will lead to predicted changes in annual sediment yield ranging from a 27 % decrease to about 160 % increase. Changes in intra-annual (monthly) discharge as well as sediment yield are even greater (−62 to 105 % in discharge and −88 to 243 % in sediment yield). A higher discharge and sediment flux are expected during the wet seasons, although the highest relative changes are observed during the dry months. The results indicate high uncertainties in the direction and magnitude of changes of discharge as well as sediment yields due to climate change. As the projected climate change impact on sediment varies remarkably between the different climate models, the uncertainty should be taken into account in both sediment management and climate change adaptation.
Evaporation is a key process in the water cycle with implications ranging, inter alia, from water... more Evaporation is a key process in the water cycle with implications ranging, inter alia, from water management to weather forecast and climate change assessments. The estimation of continental evaporation fluxes is complex and typically relies on continental-scale hydrological models or land-surface models. However, it appears that most global or continental-scale hydrological models underestimate evaporative fluxes in some regions of Africa, and as a result overestimate stream flow. Other studies suggest that landsurface models may overestimate evaporative fluxes. In this study, we computed actual evaporation for the African continent using a continental version of the global hydrological model PCR-GLOBWB, which is based on a water balance approach. Results are compared with other independently computed evaporation products: the evaporation results from the ECMWF reanalysis ERA-Interim and ERA-Land (both based on the energy balance approach), the MOD16 evaporation product, and the GLEAM product. Three other alternative versions of the PCR-GLOBWB hydrological model were also considered. This resulted in eight products of actual evaporation, which were compared in distinct regions of the African continent spanning different climatic regimes. Annual totals, spatial patterns and seasonality were studied and compared through visual inspection and statistical methods. The comparison shows that the representation of irrigation areas has an insignificant contribution to the actual evaporation at a continental scale with a 0.5 • spatial resolution when averaged over the defined regions. The choice of meteorological forcing data has a larger effect on the evapo-ration results, especially in the case of the precipitation input as different precipitation input resulted in significantly different evaporation in some of the studied regions. ERA-Interim evaporation is generally the highest of the selected products followed by ERA-Land evaporation. In some regions, the satellite-based products (GLEAM and MOD16) show a different seasonal behaviour compared to the other products. The results from this study contribute to a better understanding of the suitability and the differences between products in each climatic region. Through an improved understanding of the causes of differences between these products and their uncertainty, this study provides information to improve the quality of evaporation products for the African continent and, consequently, leads to improved water resources assessments at regional scale.
ABSTRACT To guarantee a safe flood defence in a changing environment, the adaptation to climate c... more ABSTRACT To guarantee a safe flood defence in a changing environment, the adaptation to climate change needs to be considered in the design of river dikes. However, the large uncertainty in the projections of future climate leads to varied estimations of future flood probability. How to cope with the uncertainties in future flood probability under climate change is an inevitable question in the adaptation. In this paper, the uncertainty introduced by climate projections was integrated into the ‘expected predictive flood probability’, and the risk-aversion attitude was introduced in the adaptation of river dikes. In detail, the uncertain effect of climate change on flood probability was represented by the uncertainty in the parameters of the probabilistic model. This parameter uncertainty was estimated based on the outputs from the GCMs participated in IPCC AR4. The parameter uncertainty estimated from different GCMs under selected scenarios was integrated into the expected predictive probability of flooding, which was used in the risk-aversion economic optimization. Different optimal results were obtained based on varied values of the risk-aversion index. The case of Bengbu Dike in China was studied as an example using the proposed approach. The results show that the uncertain effect of climate change causes an increase of optimal dike height but a decrease of the optimal safety level. The proposed approach enables decision makers to cope with the uncertain effects of climate change by adjusting their risk-aversion attitude.
Please cite this article as: Masih, I., Uhlenbrook, S., Maskey, S., Ahmad, M.D., Regionalization ... more Please cite this article as: Masih, I., Uhlenbrook, S., Maskey, S., Ahmad, M.D., Regionalization of a conceptual rainfall-runoff model based on similarity of the flow duration curve: A case study from the semi-arid Karkheh basin, Abstract 11
To guarantee a safe flood defence in a changing environment, the adaptation to climate change nee... more To guarantee a safe flood defence in a changing environment, the adaptation to climate change needs to be considered in the design of river dikes. However, the large uncertainty in the projections of future climate leads to varied estimations of future flood probability. How to cope with the uncertainties in future flood probability under climate change is an inevitable question in the adaptation. In this paper, the uncertainty introduced by climate projections was integrated into the 'expected predictive flood probability', and the risk-aversion attitude was introduced in the adaptation of river dikes. The uncertainty of climate change impact on flood probability was represented by the uncertainty in the parameters of the probabilistic model. This parameter uncertainty was estimated based on the outputs from the GCMs participated in IPCC AR4. The parameter uncertainty estimated from different GCMs under selected scenarios was integrated into the expected predictive probability of flooding, which was used in the risk-averse economic optimization. Different optimal results were obtained based on varied values of the risk-aversion index. A case of dike ring area in China was studied as an example using the proposed approach. The results show that the uncertainty of climate change increases the optimal dike height and decreases the optimal safety level. The proposed approach enables decision makers to cope with the climate change and the associated uncertainty by adjusting the risk-aversion level.
This paper presents a comprehensive review and analysis of the available literature and informati... more This paper presents a comprehensive review and analysis of the available literature and information on droughts to build a continental, regional and country level perspective on geospatial and temporal variation of droughts in Africa. The study is based on the review and analysis of droughts occurred during 1900-2013, as well as evidence available from past centuries based on studies on the lake sediment analysis, tree-ring chronologies and written and oral histories and future predictions from the global climate change models. Most of the studies based on instrumental records indicate that droughts have become more frequent, intense and widespread during the last 50 years. The extreme droughts of
ABSTRACT The study aimed at developing a tool to investigate the effect of prospective climate ch... more ABSTRACT The study aimed at developing a tool to investigate the effect of prospective climate change (until 2100) on hydrology and productivity of rain-fed crops (wheat Triticum L., maize Zea Mais L., and rice Oryza L.) in the Indrawati river basin, Nepal, Himalaya. Climate scenarios from 3 climate models (GCMs), namely CCSM4, EC-Earth and ECHAM6, each one under 3 different representative concentration pathways (RCPs) were fed to Soil and Water Assessment Tool (SWAT) and hydrological fluxes and crop yields were estimated for two time windows, i.e. half century (2045–2054) and end of century (2085–2094) against control run decade (1995–2004). The results foresee considerable potential changes of hydrological fluxes (from −26% to +37% yearly, with large difference seasonally and between models and RCPs), and potential changes of crop production (−36% to +18% for wheat, −17% to +4% for maize, and −17% to +12% for rice, again with differences between models and RCPs), also in term of yearly variability, potentially affecting food security. The CCSM4T model projected larger changes in hydrology and reduction in crop yields than other models. Wheat was found to be more vulnerable than maize and rice to climate change.
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Papers by Shreedhar Maskey
worldwide in the scientific as well as in the political
community, indicating that changes in precipitation, extreme
droughts and floods may increasingly threaten many regions.
Drought is a natural phenomenon that causes social, economical
and environmental damage to society. In this study, we
assess the drought intensity and severity and the groundwater
potential to be used as a supplementary source of water to
mitigate drought impacts in the Crocodile River catchment,
a water-stressed sub-catchment of the Incomati River catchment
in South Africa. The research methodology consists of
three parts. First, the spatial and temporal variation of the meteorological
and hydrological drought severity and intensity
over the catchment were evaluated. The Standardized Precipitation
Index (SPI) was used to analyse the meteorological
drought and the Standardized Runoff Index (SRI) was
used for the hydrological drought. Second, the water deficit
in the catchment during the drought period was computed
using a simple water balance method. Finally, a groundwater
model was constructed in order to assess the feasibility of
using groundwater as an emergency source for drought impact
mitigation. Results show that the low-rainfall areas are
more vulnerable to severe meteorological droughts (lower
and upper crocodile). Moreover, the most water stressed subcatchments
with high level of water uses but limited storage,
such as the Kaap located in the middle catchment and
the Lower Crocodile sub-catchments, are more vulnerable
to severe hydrological droughts. The analysis of the potential
groundwater use during droughts showed that a deficit
of 97Mm3 yr1 could be supplied from groundwater without
considerable adverse impacts on the river base flow and
groundwater storage. Abstraction simulations for different
scenarios of extremely severe droughts reveal that it is possible
to use groundwater to cope with the droughts in the catchment.
However, local groundwater exploitation in Nelspruit
and White River sub-catchment will cause large drawdowns
(> 10 m) and high base flow reduction (> 20 %). This case
study shows that conjunctive water management of groundwater
and surface water resources is necessary to mitigate the
impacts of droughts.
worldwide in the scientific as well as in the political
community, indicating that changes in precipitation, extreme
droughts and floods may increasingly threaten many regions.
Drought is a natural phenomenon that causes social, economical
and environmental damage to society. In this study, we
assess the drought intensity and severity and the groundwater
potential to be used as a supplementary source of water to
mitigate drought impacts in the Crocodile River catchment,
a water-stressed sub-catchment of the Incomati River catchment
in South Africa. The research methodology consists of
three parts. First, the spatial and temporal variation of the meteorological
and hydrological drought severity and intensity
over the catchment were evaluated. The Standardized Precipitation
Index (SPI) was used to analyse the meteorological
drought and the Standardized Runoff Index (SRI) was
used for the hydrological drought. Second, the water deficit
in the catchment during the drought period was computed
using a simple water balance method. Finally, a groundwater
model was constructed in order to assess the feasibility of
using groundwater as an emergency source for drought impact
mitigation. Results show that the low-rainfall areas are
more vulnerable to severe meteorological droughts (lower
and upper crocodile). Moreover, the most water stressed subcatchments
with high level of water uses but limited storage,
such as the Kaap located in the middle catchment and
the Lower Crocodile sub-catchments, are more vulnerable
to severe hydrological droughts. The analysis of the potential
groundwater use during droughts showed that a deficit
of 97Mm3 yr1 could be supplied from groundwater without
considerable adverse impacts on the river base flow and
groundwater storage. Abstraction simulations for different
scenarios of extremely severe droughts reveal that it is possible
to use groundwater to cope with the droughts in the catchment.
However, local groundwater exploitation in Nelspruit
and White River sub-catchment will cause large drawdowns
(> 10 m) and high base flow reduction (> 20 %). This case
study shows that conjunctive water management of groundwater
and surface water resources is necessary to mitigate the
impacts of droughts.