Adisorn Champathong, N. Hanasaki, Masashi Kiguchi, T. Oki
Understanding the extent to which human activities affect river flow is fundamental for enhancing effective water resources management. In past decades, various methods have been proposed to estimate naturalized flow (i.e. the expected flow if the basin is unaffected by human activities). However, there are still drawbacks to natural‐ ized flow estimation, particularly in a highly regulated basin with incomplete hydrological observation. This study proposes a method for daily naturalized flow development at the key station of the Chao Phraya River Basin; the most highly regulated basin in Thailand. The naturalized flow is estimated by applying the Naturalization with Coarse and Fine Components (NCFC) method to perceive river flow conditions unaffected by human disturbance. The estima‐ tion is derived with the integration of five components: (1) observed river flow at the key hydrological station; (2) changes in major reservoir storage; (3) water withdrawal along the river; (4) travel time from major reservoirs to the station; and (5) the filtering technique used by SavitzkyGolay with a three-day window.
{"title":"Reconstructing the pristine flow of highly developed rivers − a case study on the Chao Phraya River","authors":"Adisorn Champathong, N. Hanasaki, Masashi Kiguchi, T. Oki","doi":"10.3178/hrl.14.89","DOIUrl":"https://doi.org/10.3178/hrl.14.89","url":null,"abstract":"Understanding the extent to which human activities affect river flow is fundamental for enhancing effective water resources management. In past decades, various methods have been proposed to estimate naturalized flow (i.e. the expected flow if the basin is unaffected by human activities). However, there are still drawbacks to natural‐ ized flow estimation, particularly in a highly regulated basin with incomplete hydrological observation. This study proposes a method for daily naturalized flow development at the key station of the Chao Phraya River Basin; the most highly regulated basin in Thailand. The naturalized flow is estimated by applying the Naturalization with Coarse and Fine Components (NCFC) method to perceive river flow conditions unaffected by human disturbance. The estima‐ tion is derived with the integration of five components: (1) observed river flow at the key hydrological station; (2) changes in major reservoir storage; (3) water withdrawal along the river; (4) travel time from major reservoirs to the station; and (5) the filtering technique used by SavitzkyGolay with a three-day window.","PeriodicalId":13111,"journal":{"name":"Hydrological Research Letters","volume":null,"pages":null},"PeriodicalIF":1.1,"publicationDate":"2020-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"69394479","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
: The Central Asian countries have abundant but unevenly distributed natural resources including water. The Central Asia Power System (CAPS) project initiated by the Asian Development Bank and the Central Asia-South Asia Elec‐ tricity Transmission and Trade Project (CASA-1000) initi‐ ated by the World Bank are planned to catalyze trade of electricity in this region. However, the existing surplus of the hydropower generation capacity of Tajikistan in sum‐ mer may only meet the anticipated power demand by one project. The CAPS project (to be completed in 2023) may monopolize the surplus in Tajikistan and the CASA-1000 project (to be completed later) may suffer from the shortage of electricity. It stems from the failure of aid coordination between the Asian Development Bank and the World Bank. This study reveals (a) how the assumptions made for the CAPS and CASA-1000 projects differ, and (b) possible causes of the failed aid coordination. It turned out that (a) the officer in a development bank who is in charge of project development has little motivation to submit his or her project to aid coordination, (b) only “geographic demarcation” between two projects was discussed and agreed upon in the aid coordination, and (c) no technical detail of these projects was discussed in the aid coordina‐ tion.
{"title":"Bottlenecks of hydropower development in Central Asia: Failure of aid coordination by development banks","authors":"Hiroyuki Deguchi, Daisuke Sasaki, M. Nakayama","doi":"10.3178/hrl.14.29","DOIUrl":"https://doi.org/10.3178/hrl.14.29","url":null,"abstract":": The Central Asian countries have abundant but unevenly distributed natural resources including water. The Central Asia Power System (CAPS) project initiated by the Asian Development Bank and the Central Asia-South Asia Elec‐ tricity Transmission and Trade Project (CASA-1000) initi‐ ated by the World Bank are planned to catalyze trade of electricity in this region. However, the existing surplus of the hydropower generation capacity of Tajikistan in sum‐ mer may only meet the anticipated power demand by one project. The CAPS project (to be completed in 2023) may monopolize the surplus in Tajikistan and the CASA-1000 project (to be completed later) may suffer from the shortage of electricity. It stems from the failure of aid coordination between the Asian Development Bank and the World Bank. This study reveals (a) how the assumptions made for the CAPS and CASA-1000 projects differ, and (b) possible causes of the failed aid coordination. It turned out that (a) the officer in a development bank who is in charge of project development has little motivation to submit his or her project to aid coordination, (b) only “geographic demarcation” between two projects was discussed and agreed upon in the aid coordination, and (c) no technical detail of these projects was discussed in the aid coordina‐ tion.","PeriodicalId":13111,"journal":{"name":"Hydrological Research Letters","volume":null,"pages":null},"PeriodicalIF":1.1,"publicationDate":"2020-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"69393831","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Y. Hiraga, S. Kazama, C. Ekkawatpanit, Keitaro Yamada
Nowadays, a deterioration of floodplain water quality in the Lower Mekong River Basin in Cambodia is expected because of urbanization/industrialization by landfilling. This study aimed to evaluate the impact of floodplain land‐ filling on basin water quality. Field observations of total phosphorus (TP), chemical oxygen demand and heavy met‐ als were conducted in the Mekong River Basin in Cambodia and the Chao Phraya River Basin in Thailand. In the Mekong River Basin, TP was 2.05 mg/L in the flood‐ plain where large-scale landfill was carried out using waste, with iron (Fe) at the factory site 6.54 mg/L. In comparison, in the Chao Phraya River Basin, TP and Fe concentrations were low. A degree of floodplain water quality manage‐ ment commensurate to the level of economic development was confirmed from water quality conservation efforts, among others, in Thailand.
{"title":"Evaluation of the impact of landfill on floodplain water quality in a tropical monsoon region","authors":"Y. Hiraga, S. Kazama, C. Ekkawatpanit, Keitaro Yamada","doi":"10.3178/hrl.14.48","DOIUrl":"https://doi.org/10.3178/hrl.14.48","url":null,"abstract":"Nowadays, a deterioration of floodplain water quality in the Lower Mekong River Basin in Cambodia is expected because of urbanization/industrialization by landfilling. This study aimed to evaluate the impact of floodplain land‐ filling on basin water quality. Field observations of total phosphorus (TP), chemical oxygen demand and heavy met‐ als were conducted in the Mekong River Basin in Cambodia and the Chao Phraya River Basin in Thailand. In the Mekong River Basin, TP was 2.05 mg/L in the flood‐ plain where large-scale landfill was carried out using waste, with iron (Fe) at the factory site 6.54 mg/L. In comparison, in the Chao Phraya River Basin, TP and Fe concentrations were low. A degree of floodplain water quality manage‐ ment commensurate to the level of economic development was confirmed from water quality conservation efforts, among others, in Thailand.","PeriodicalId":13111,"journal":{"name":"Hydrological Research Letters","volume":null,"pages":null},"PeriodicalIF":1.1,"publicationDate":"2020-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"69393931","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Y. Asada, M. Kimura, Issaku Azechi, T. Iida, Naritaka Kubo
: Numerous leak detection methods have been developed for pipeline systems because of the shortage of water resources, increased water demand, and leak accidents. These methods have their advantages and disadvantages in terms of cost, labor, and accuracy; therefore, it is important to narrow down the location of a leak as easily, rapidly, and accurately as possible. This study applies the technologies based on the execution of a transient event (transient test-based technologies (TTBTs)), and a model is presented for representing the relation between the leak location and the damping of the pressure transient due to the leakage. The model is verified with laboratory experiments in which the leak location can be narrowed down to be less than 10% to 30% of the total pipe length. The model is found to be more effective if the leak location is nearer to the upstream end. In addition, the leak location found by the damping model varies with an approximate absolute error of 2% to 5% of the pipe length. It is suggested that the damping model is suitable for narrowing down and not for finding the leak location, and should be used in combination with other leak detection methods.
{"title":"Transient damping method for narrowing down leak location in pressurized pipelines","authors":"Y. Asada, M. Kimura, Issaku Azechi, T. Iida, Naritaka Kubo","doi":"10.3178/hrl.14.41","DOIUrl":"https://doi.org/10.3178/hrl.14.41","url":null,"abstract":": Numerous leak detection methods have been developed for pipeline systems because of the shortage of water resources, increased water demand, and leak accidents. These methods have their advantages and disadvantages in terms of cost, labor, and accuracy; therefore, it is important to narrow down the location of a leak as easily, rapidly, and accurately as possible. This study applies the technologies based on the execution of a transient event (transient test-based technologies (TTBTs)), and a model is presented for representing the relation between the leak location and the damping of the pressure transient due to the leakage. The model is verified with laboratory experiments in which the leak location can be narrowed down to be less than 10% to 30% of the total pipe length. The model is found to be more effective if the leak location is nearer to the upstream end. In addition, the leak location found by the damping model varies with an approximate absolute error of 2% to 5% of the pipe length. It is suggested that the damping model is suitable for narrowing down and not for finding the leak location, and should be used in combination with other leak detection methods.","PeriodicalId":13111,"journal":{"name":"Hydrological Research Letters","volume":null,"pages":null},"PeriodicalIF":1.1,"publicationDate":"2020-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.3178/hrl.14.41","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"69393885","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
: To classify the aquifer type and to estimate the pneu‐ matic diffusivity using harmonic analysis and analytical expressions, we measured groundwater levels and baro‐ metric pressure in an unconfined aquifer with a thick un‐ saturated zone at a southern part of the Beppu volcanic fan, Japan. The groundwater level was inversely related to the barometric pressure, with little or no time lag behind baro‐ metric pressure. The groundwater level and barometric pressure exhibit periodic changes with prominent spectra at K 1 (lunar-solar diurnal) and S 2 (main solar semidiurnal) tidal constituents but not at O 1 (main lunar diurnal) and M 2 (main lunar semidiurnal) tidal constituents, which are the motions of solar and lunar relative to the earth. It indicates that the aquifer is an unconfined aquifer type with no earth tide effect. Pneumatic diffusivity in the unsaturated zone was estimated as 7.6 × 10 –2 to 5.7 × 10 –3 m 2 /s using changes between the groundwater level and the barometric pressure. The pneumatic diffusivity and the unsaturated zone thick‐ ness strongly affect amplitude ratios and phase lags between the groundwater level and the barometric pressure in the unconfined aquifer.
{"title":"Aquifer classification and pneumatic diffusivity estimation using periodic groundwater level changes induced by barometric pressure","authors":"Heejun Yang, T. Shibata","doi":"10.3178/HRL.14.111","DOIUrl":"https://doi.org/10.3178/HRL.14.111","url":null,"abstract":": To classify the aquifer type and to estimate the pneu‐ matic diffusivity using harmonic analysis and analytical expressions, we measured groundwater levels and baro‐ metric pressure in an unconfined aquifer with a thick un‐ saturated zone at a southern part of the Beppu volcanic fan, Japan. The groundwater level was inversely related to the barometric pressure, with little or no time lag behind baro‐ metric pressure. The groundwater level and barometric pressure exhibit periodic changes with prominent spectra at K 1 (lunar-solar diurnal) and S 2 (main solar semidiurnal) tidal constituents but not at O 1 (main lunar diurnal) and M 2 (main lunar semidiurnal) tidal constituents, which are the motions of solar and lunar relative to the earth. It indicates that the aquifer is an unconfined aquifer type with no earth tide effect. Pneumatic diffusivity in the unsaturated zone was estimated as 7.6 × 10 –2 to 5.7 × 10 –3 m 2 /s using changes between the groundwater level and the barometric pressure. The pneumatic diffusivity and the unsaturated zone thick‐ ness strongly affect amplitude ratios and phase lags between the groundwater level and the barometric pressure in the unconfined aquifer.","PeriodicalId":13111,"journal":{"name":"Hydrological Research Letters","volume":null,"pages":null},"PeriodicalIF":1.1,"publicationDate":"2020-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"69394163","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A. Hama, Kei Tanaka, A. Mochizuki, Y. Tsuruoka, A. Kondoh
: The objectives of this study were to improve the yield estimation of paddy rice based on the unmanned aerial vehicle remote sensing (UAV-RS) and solar radiation data sets. The study used the UAV-RS-based normalized differ‐ ence vegetation index (NDVI) at the heading stage, the solar radiation data of geostationary satellite Himawari-8 and the solar radiation data of polar orbiting satellite Aqua/ MODIS. A comparison of two satellite-based solar radia‐ tion data sets (Himawari-8 and MODIS PAR) showed that the coefficient of determination ( R 2 ) of estimated yield based on Himawari-8 solar radiation was 0.7606 while the R 2 of estimated yield based on the MODIS PAR was 0.4749. Additionally, the root mean square error (RMSE) of Himawari-8 solar radiation was 26.5 g/m 2 while the RMSE of estimated yield based on the MODIS PAR was 39.2 g/m 2 (The average observed yield was 489.3 g/m 2 ). The Estimated yield based on Himawari-8 solar radiation, therefore, outperformed the MODIS PAR-based estimated yield. The improvement of the temporal resolution of the satellite-based dataset allowed by using the Himawari-8 data set contributed to the improvement of estimation accu‐ racy. Satellite-based solar radiation data allow yield estima‐ tion based on remote sensing in regions where there are no ground observation data of solar radiation.
{"title":"Improving the UAV-based yield estimation of paddy rice by using the solar radiation of geostationary satellite Himawari-8","authors":"A. Hama, Kei Tanaka, A. Mochizuki, Y. Tsuruoka, A. Kondoh","doi":"10.3178/hrl.14.56","DOIUrl":"https://doi.org/10.3178/hrl.14.56","url":null,"abstract":": The objectives of this study were to improve the yield estimation of paddy rice based on the unmanned aerial vehicle remote sensing (UAV-RS) and solar radiation data sets. The study used the UAV-RS-based normalized differ‐ ence vegetation index (NDVI) at the heading stage, the solar radiation data of geostationary satellite Himawari-8 and the solar radiation data of polar orbiting satellite Aqua/ MODIS. A comparison of two satellite-based solar radia‐ tion data sets (Himawari-8 and MODIS PAR) showed that the coefficient of determination ( R 2 ) of estimated yield based on Himawari-8 solar radiation was 0.7606 while the R 2 of estimated yield based on the MODIS PAR was 0.4749. Additionally, the root mean square error (RMSE) of Himawari-8 solar radiation was 26.5 g/m 2 while the RMSE of estimated yield based on the MODIS PAR was 39.2 g/m 2 (The average observed yield was 489.3 g/m 2 ). The Estimated yield based on Himawari-8 solar radiation, therefore, outperformed the MODIS PAR-based estimated yield. The improvement of the temporal resolution of the satellite-based dataset allowed by using the Himawari-8 data set contributed to the improvement of estimation accu‐ racy. Satellite-based solar radiation data allow yield estima‐ tion based on remote sensing in regions where there are no ground observation data of solar radiation.","PeriodicalId":13111,"journal":{"name":"Hydrological Research Letters","volume":null,"pages":null},"PeriodicalIF":1.1,"publicationDate":"2020-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.3178/hrl.14.56","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"69393945","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
: In this research, power generation potential is estimated using overflow discharge for eight headworks (Inuyama, Meiji-yousui, Muromatsubara, Kansakawa, Furikusa, Onyu, Hosokawa and Okajima) located in Aichi and Gifu Prefectures, and the characteristics of their power genera‐ tion are clarified in order to evaluate the feasibility of small hydropower plants. The results are as follows. Firstly, over‐ flow discharge is more stable than the discharge of intake water at the headworks, which suggests that power genera‐ tion using overflow discharge is more suitable for actual power generation. Secondly, maximum power outputs of 43 kW to 2,002 kW, under a discharge utilization factor of 60%, show great potential for power generation at these eight headworks. Finally, fluctuations in monthly power generation are higher than that of annual power generation due to the influences of irrigation and seasonal changes in precipitation on water intake.
{"title":"Potential for and feasibility of small hydropower generation at headworks in Japan","authors":"Fenglan Wang, K. Noda, Issaku Azechi, M. Senge","doi":"10.3178/hrl.14.23","DOIUrl":"https://doi.org/10.3178/hrl.14.23","url":null,"abstract":": In this research, power generation potential is estimated using overflow discharge for eight headworks (Inuyama, Meiji-yousui, Muromatsubara, Kansakawa, Furikusa, Onyu, Hosokawa and Okajima) located in Aichi and Gifu Prefectures, and the characteristics of their power genera‐ tion are clarified in order to evaluate the feasibility of small hydropower plants. The results are as follows. Firstly, over‐ flow discharge is more stable than the discharge of intake water at the headworks, which suggests that power genera‐ tion using overflow discharge is more suitable for actual power generation. Secondly, maximum power outputs of 43 kW to 2,002 kW, under a discharge utilization factor of 60%, show great potential for power generation at these eight headworks. Finally, fluctuations in monthly power generation are higher than that of annual power generation due to the influences of irrigation and seasonal changes in precipitation on water intake.","PeriodicalId":13111,"journal":{"name":"Hydrological Research Letters","volume":null,"pages":null},"PeriodicalIF":1.1,"publicationDate":"2020-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.3178/hrl.14.23","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"69393818","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
: A Snow Model (SM) using a temperature-index method was used to optimize the degree-day factor ( DDF ) and pre‐ cipitation gradient ( PG ) for the different elevation zones of the Panjshir sub-basin for snowmelt runoff modelling. The values derived for DDF and PG were calibrated and vali‐ dated by comparing observed snow cover area and snow cover area simulated by SM. The Snowmelt Runoff Model (SRM) was used to simulate daily runoff over the hydro‐ logical years 2009–2014 using the optimized values for SRM accuracy. The optimized DDF values were 0.3 to 0.9 (cm °C –1 d –1 ) for elevations from 1593 m to 5694 m. Mean‐ while the PG was +0.002 m –1 for elevations 1593–4000 m and 0 m –1 above 4000 m. The simulated runoff by SRM during the entire data period correlated very well with a Nash-Sutcliffe coefficient NS = 0.93 utilizing both observed and simulated snow cover area. This method not only evaluates the characteristics of snowfall and snowmelt in different elevation zones to obtain the DDF and PG , but can also estimate the snowmelt runoff.
采用温度指数法的积雪模型(SM)优化了潘杰希尔次流域不同高程带的日数因子(DDF)和降水梯度(PG)，用于融雪径流模拟。通过比较观测积雪面积和SM模拟积雪面积，对DDF和PG的数值进行了校准和验证。采用融雪径流模型(SRM)对2009-2014年水文年的日径流进行了模拟，得到了SRM精度的优化值。在海拔1593 ~ 5694 m范围内，最佳DDF值为0.3 ~ 0.9 (cm°C -1 d -1)。而海拔1593-4000 m的PG平均值为+0.002 m -1，海拔4000 m以上的PG平均值为0 m -1。利用实测和模拟积雪面积，SRM模拟径流在整个数据期内与Nash-Sutcliffe系数NS = 0.93的相关性非常好。该方法不仅可以评价不同高程带的降雪和融雪特征，得到DDF和PG，还可以估算融雪径流量。
{"title":"Incorporating snow model and snowmelt runoff model for streamflow simulation in a snow-dominated mountainous basin in the western Hindukush-Himalaya region","authors":"Abdul Haseeb Azizi, Y. Asaoka","doi":"10.3178/hrl.14.34","DOIUrl":"https://doi.org/10.3178/hrl.14.34","url":null,"abstract":": A Snow Model (SM) using a temperature-index method was used to optimize the degree-day factor ( DDF ) and pre‐ cipitation gradient ( PG ) for the different elevation zones of the Panjshir sub-basin for snowmelt runoff modelling. The values derived for DDF and PG were calibrated and vali‐ dated by comparing observed snow cover area and snow cover area simulated by SM. The Snowmelt Runoff Model (SRM) was used to simulate daily runoff over the hydro‐ logical years 2009–2014 using the optimized values for SRM accuracy. The optimized DDF values were 0.3 to 0.9 (cm °C –1 d –1 ) for elevations from 1593 m to 5694 m. Mean‐ while the PG was +0.002 m –1 for elevations 1593–4000 m and 0 m –1 above 4000 m. The simulated runoff by SRM during the entire data period correlated very well with a Nash-Sutcliffe coefficient NS = 0.93 utilizing both observed and simulated snow cover area. This method not only evaluates the characteristics of snowfall and snowmelt in different elevation zones to obtain the DDF and PG , but can also estimate the snowmelt runoff.","PeriodicalId":13111,"journal":{"name":"Hydrological Research Letters","volume":null,"pages":null},"PeriodicalIF":1.1,"publicationDate":"2020-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.3178/hrl.14.34","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"69393874","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
: A distributed hydrologic model based on a kinematic wave approximation with surface and subsurface flow com‐ ponents is applicable to basins that have temperate climatic conditions similar to those in Japan. However, it is difficult to present long-term river discharge using the existing model structure in basins with different climatic conditions. This study aims to improve the model structure for better estimates of long-term discharge in the Nam Ngum River, the main tributary of the Mekong River, by incorporating bedrock aquifers as part of the slope flow component of the original model structure. Three bedrock groundwater struc‐ tures are configured to incorporate the original model structure. The results show that a combination of the origi‐ nal model component and one unconfined aquifer structure are the best representations of the river flow regime from the original model structure, in which the rate of infiltration from the layer into the bedrock aquifer was calculated using vertical hydraulic conductivity. The Nash–Sutcliffe efficiency coefficient of the original and improved models increased from 0.80 to 0.86 during the calibration period and from 0.56 to 0.62 during the validation period. The results of this study show that the improved model structure is applicable for long-term hydrologic predictions in South‐ east Asian catchments with distinct dry and rainy seasons.
{"title":"Structural improvement of a kinematic wave-based distributed hydrologic model to estimate long-term river discharge in a tropical climate basin","authors":"Thatkiat Meema, Y. Tachikawa","doi":"10.3178/hrl.14.104","DOIUrl":"https://doi.org/10.3178/hrl.14.104","url":null,"abstract":": A distributed hydrologic model based on a kinematic wave approximation with surface and subsurface flow com‐ ponents is applicable to basins that have temperate climatic conditions similar to those in Japan. However, it is difficult to present long-term river discharge using the existing model structure in basins with different climatic conditions. This study aims to improve the model structure for better estimates of long-term discharge in the Nam Ngum River, the main tributary of the Mekong River, by incorporating bedrock aquifers as part of the slope flow component of the original model structure. Three bedrock groundwater struc‐ tures are configured to incorporate the original model structure. The results show that a combination of the origi‐ nal model component and one unconfined aquifer structure are the best representations of the river flow regime from the original model structure, in which the rate of infiltration from the layer into the bedrock aquifer was calculated using vertical hydraulic conductivity. The Nash–Sutcliffe efficiency coefficient of the original and improved models increased from 0.80 to 0.86 during the calibration period and from 0.56 to 0.62 during the validation period. The results of this study show that the improved model structure is applicable for long-term hydrologic predictions in South‐ east Asian catchments with distinct dry and rainy seasons.","PeriodicalId":13111,"journal":{"name":"Hydrological Research Letters","volume":null,"pages":null},"PeriodicalIF":1.1,"publicationDate":"2020-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"69394154","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
R. Ito, T. Ose, H. Endo, R. Mizuta, K. Yoshida, A. Kitoh, T. Nakaegawa
: Information on future climate change considering regional characteristics is necessary to establish adaptation strategies for global warming. We investigated the seasonal characteristics of future climate projections over Japan and surroundings (JPN) in the late 21st century, focusing espe‐ cially on the source of uncertainty, based on two ensembles of the Coupled Model Intercomparison Project Phase 5 (CMIP5) and the Meteorological Research Institute atmo‐ spheric general circulation model (MRI-AGCM) global warming simulations. The ensemble mean surface air tem‐ perature increase over JPN is lower than that over the East Asian land region (EAS), reflecting the continent–ocean contrast, whereas quantitative changes in future precipita‐ tion depend on the ensembles. The CMIP5 mean atmo‐ spheric circulation around JPN weakens in winter and sum‐ mer, while the future seasonal march tends to be delayed in the northern part of JPN during spring and autumn. Signifi‐ cant CMIP5 inter-model correlations are detected between the JPN climate projections and future circulation anoma‐ lies − e.g. the ensemble members simulating the westerly/ southeasterly wind anomaly tend to project hotter/wetter future summers. The high-resolution MRI-AGCM projec‐ tion is consistent with the CMIP5 inter-model correlations when the future change in typhoon–associated precipitation is removed, indicating typhoon simulations can substan‐ tially influence future projections.
{"title":"Seasonal characteristics of future climate change over Japan and the associated atmospheric circulation anomalies in global model experiments","authors":"R. Ito, T. Ose, H. Endo, R. Mizuta, K. Yoshida, A. Kitoh, T. Nakaegawa","doi":"10.3178/hrl.14.130","DOIUrl":"https://doi.org/10.3178/hrl.14.130","url":null,"abstract":": Information on future climate change considering regional characteristics is necessary to establish adaptation strategies for global warming. We investigated the seasonal characteristics of future climate projections over Japan and surroundings (JPN) in the late 21st century, focusing espe‐ cially on the source of uncertainty, based on two ensembles of the Coupled Model Intercomparison Project Phase 5 (CMIP5) and the Meteorological Research Institute atmo‐ spheric general circulation model (MRI-AGCM) global warming simulations. The ensemble mean surface air tem‐ perature increase over JPN is lower than that over the East Asian land region (EAS), reflecting the continent–ocean contrast, whereas quantitative changes in future precipita‐ tion depend on the ensembles. The CMIP5 mean atmo‐ spheric circulation around JPN weakens in winter and sum‐ mer, while the future seasonal march tends to be delayed in the northern part of JPN during spring and autumn. Signifi‐ cant CMIP5 inter-model correlations are detected between the JPN climate projections and future circulation anoma‐ lies − e.g. the ensemble members simulating the westerly/ southeasterly wind anomaly tend to project hotter/wetter future summers. The high-resolution MRI-AGCM projec‐ tion is consistent with the CMIP5 inter-model correlations when the future change in typhoon–associated precipitation is removed, indicating typhoon simulations can substan‐ tially influence future projections.","PeriodicalId":13111,"journal":{"name":"Hydrological Research Letters","volume":null,"pages":null},"PeriodicalIF":1.1,"publicationDate":"2020-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"69394211","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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