Thu Thanh Nguyen, M. Nakatsugawa, T. Yamada, T. Hoshino
: This study investigates the change in extreme rainfall and river flooding for a large river basin due to climate change during the summer monsoon using a large ensemble dataset (d4PDF) coupled with the Integrated Flood Analy‐ sis System (IFAS). Frequent severe flooding causes signifi‐ cant damage in Japan. Therefore, we aim to provide useful information to mitigate flood damage. The study area is the Ishikari River basin (IRB) in Hokkaido, Japan. We used the d4PDF 5-km downscaled rainfall data as input for the IFAS model. The results showed that, for a given increase in extreme rainfall, the discharges from the IRB and its main sub-basins increase to a greater extent. The differences between the time of peak discharge at the reference stations in each tributary and the time of peak water level at the confluence points in the main river are evaluated. Climate change effects are significant in the southern sub-basins, wherein the amount of extreme rainfall increases by 29%– 35%, whereas the river discharge increases drastically (37%–56%). Additionally, the time difference decreases by 1.02–2.14 h. These findings will help policymakers develop future flood control measures in flood-prone areas.
{"title":"Assessing climate change impacts on extreme rainfall and severe flooding during the summer monsoon season in the Ishikari River basin, Japan","authors":"Thu Thanh Nguyen, M. Nakatsugawa, T. Yamada, T. Hoshino","doi":"10.3178/hrl.14.155","DOIUrl":"https://doi.org/10.3178/hrl.14.155","url":null,"abstract":": This study investigates the change in extreme rainfall and river flooding for a large river basin due to climate change during the summer monsoon using a large ensemble dataset (d4PDF) coupled with the Integrated Flood Analy‐ sis System (IFAS). Frequent severe flooding causes signifi‐ cant damage in Japan. Therefore, we aim to provide useful information to mitigate flood damage. The study area is the Ishikari River basin (IRB) in Hokkaido, Japan. We used the d4PDF 5-km downscaled rainfall data as input for the IFAS model. The results showed that, for a given increase in extreme rainfall, the discharges from the IRB and its main sub-basins increase to a greater extent. The differences between the time of peak discharge at the reference stations in each tributary and the time of peak water level at the confluence points in the main river are evaluated. Climate change effects are significant in the southern sub-basins, wherein the amount of extreme rainfall increases by 29%– 35%, whereas the river discharge increases drastically (37%–56%). Additionally, the time difference decreases by 1.02–2.14 h. These findings will help policymakers develop future flood control measures in flood-prone areas.","PeriodicalId":13111,"journal":{"name":"Hydrological Research Letters","volume":"1 1","pages":""},"PeriodicalIF":1.1,"publicationDate":"2020-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"69393812","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}
Using high-resolution elevation data (2 m × 2 m), obtained during a 2012 aerial Lidar survey as part of the Chao Phraya River basin flood management project in Thailand, we assessed the impact of sea level rise due to climate change on the Bangkok metropolitan area. The area below the current median tide of 1.11 m was estimated to be 2,520 km2, with a vulnerable population of 3.9 million, equivalent to 23% of the total population of the Bangkok metropolitan area. In the worst-case scenario of Represen‐ tative Concentration Pathway (RCP) 8.5 (sea level rise of +1.10 m), the affected area would extend to 6,140 km2, increasing the estimated vulnerable population by 86% to 7.2 million. With a sea level rise of less than +1.10 m, the affected area would extend from the Chao Phraya River mouth to Suphan Buri, which is about 80 km inland; how‐ ever, the density of the vulnerable population would increase. The results of this study suggest that sea level rise adaptation measures, such as migration and settlement, must be developed as soon as possible.
{"title":"Use of high-resolution elevation data to assess the vulnerability of the Bangkok metropolitan area to sea level rise","authors":"T. Tebakari","doi":"10.3178/hrl.14.136","DOIUrl":"https://doi.org/10.3178/hrl.14.136","url":null,"abstract":"Using high-resolution elevation data (2 m × 2 m), obtained during a 2012 aerial Lidar survey as part of the Chao Phraya River basin flood management project in Thailand, we assessed the impact of sea level rise due to climate change on the Bangkok metropolitan area. The area below the current median tide of 1.11 m was estimated to be 2,520 km2, with a vulnerable population of 3.9 million, equivalent to 23% of the total population of the Bangkok metropolitan area. In the worst-case scenario of Represen‐ tative Concentration Pathway (RCP) 8.5 (sea level rise of +1.10 m), the affected area would extend to 6,140 km2, increasing the estimated vulnerable population by 86% to 7.2 million. With a sea level rise of less than +1.10 m, the affected area would extend from the Chao Phraya River mouth to Suphan Buri, which is about 80 km inland; how‐ ever, the density of the vulnerable population would increase. The results of this study suggest that sea level rise adaptation measures, such as migration and settlement, must be developed as soon as possible.","PeriodicalId":13111,"journal":{"name":"Hydrological Research Letters","volume":"1 1","pages":""},"PeriodicalIF":1.1,"publicationDate":"2020-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"69394224","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}
Yutaka Abe, Y. Uchiyama, M. Saito, Mitsuru Ohira, T. Yokoyama
: This study investigated runoff to clarify the effect of bedrock groundwater dynamics on runoff generation pro‐ cesses in granodiorite headwater catchments (NA and NB) located in the western Tanzawa Mountains, Central Japan. The rainfall–runoff response and water balance calculated using the hydrological cycle (HYCY) model with outflow were also analyzed based on the observed precipitation, runoff, and bedrock groundwater level (at a depth of 50 m). In 2013, the annual runoff rate was 398 mm (21% of the rainfall) in NA and 1209 mm (63% of the rainfall) in NB, respectively. The bedrock groundwater level varied for approximately 3 m, and responded to 30-mm rainfall events. The significant relationship between the base flow and bedrock groundwater level indicated that the bedrock groundwater markedly influenced base flow generation. The calculated annual bedrock infiltration values of 656 mm (34% of the rainfall) in NA and 52 mm (3% of the rainfall) in NB significantly influenced the runoff rate. Our results demonstrated that significant and negligible amounts of bedrock groundwater infiltration were observed, even in neighboring catchments. Those bedrock groundwater dynamics significantly influenced the observed differences in the runoff rate and base flow gener‐ ation.
{"title":"Effects of bedrock groundwater dynamics on runoff generation: a case study on granodiorite headwater catchments, western Tanzawa Mountains, Japan","authors":"Yutaka Abe, Y. Uchiyama, M. Saito, Mitsuru Ohira, T. Yokoyama","doi":"10.3178/hrl.14.62","DOIUrl":"https://doi.org/10.3178/hrl.14.62","url":null,"abstract":": This study investigated runoff to clarify the effect of bedrock groundwater dynamics on runoff generation pro‐ cesses in granodiorite headwater catchments (NA and NB) located in the western Tanzawa Mountains, Central Japan. The rainfall–runoff response and water balance calculated using the hydrological cycle (HYCY) model with outflow were also analyzed based on the observed precipitation, runoff, and bedrock groundwater level (at a depth of 50 m). In 2013, the annual runoff rate was 398 mm (21% of the rainfall) in NA and 1209 mm (63% of the rainfall) in NB, respectively. The bedrock groundwater level varied for approximately 3 m, and responded to 30-mm rainfall events. The significant relationship between the base flow and bedrock groundwater level indicated that the bedrock groundwater markedly influenced base flow generation. The calculated annual bedrock infiltration values of 656 mm (34% of the rainfall) in NA and 52 mm (3% of the rainfall) in NB significantly influenced the runoff rate. Our results demonstrated that significant and negligible amounts of bedrock groundwater infiltration were observed, even in neighboring catchments. Those bedrock groundwater dynamics significantly influenced the observed differences in the runoff rate and base flow gener‐ ation.","PeriodicalId":13111,"journal":{"name":"Hydrological Research Letters","volume":"53 1","pages":""},"PeriodicalIF":1.1,"publicationDate":"2020-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"69394010","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}
Huu Le Tien, K. Okubo, Phuong Tham Ho Thi, M. Saito
External nutrient loadings to Lake Biwa were estimated using a combined tank model and loading-discharge curve approach. The model was applied to collective drainage basins of the lake’s Imazu (northwest), Hikone (northeast), and Otsu (south) areas. The hourly model was conducted using particular discharges from Kita (Ado) river, Takatoki (Ane) river, and Yasu River to obtain loading curves for phosphate (PO4) and silica (SiO2) by assimilating measured concentrations (2002–2003). The tank model was updated by adding an evapotranspiration routine and direct paths of groundwater discharges to the lake floor. The daily model was calibrated through analysis of water budget among the basin, inflow, lake and outflow, and then validated. The model was established and combined into a loadingdischarge curve to determine the long-term external nutri‐ ent loadings entering the lake (1980–2017). Seasonal varia‐ tion in nutrient loadings increased during spring and summer and decreased during winter. Annual phosphatephosphorus (PO4-P) loading ranged from 217 to 296 tons yr–1 in the North Basin and 45 to 76 tons yr–1 in the South Basin, while SiO2 loading fluctuated from 16,027 to 32,655 tons yr–1 and 2,518 to 5,490 tons yr–1 in the North and South Basins, respectively.
采用水池模型和负荷-流量曲线法对琵琶湖的外部养分负荷进行了估算。该模型应用于该湖泊西北部的今津、东北部的彦根和南部的大津地区的集体流域。利用基多河(Ado)、高木河(Ane)和Yasu河的特定排放进行逐时模型，通过同化测量浓度获得磷酸盐(PO4)和二氧化硅(SiO2)的负荷曲线(2002-2003年)。水箱模型通过添加蒸发蒸腾常规和地下水排放到湖底的直接路径进行了更新。通过分析流域、入流、湖泊和出水口之间的水量收支，对日模型进行了标定，并进行了验证。建立模型并将其结合到负荷-排放曲线中，确定了1980-2017年长期入湖的外部养分负荷。养分负荷的季节变化在春季和夏季增加，在冬季减少。北盆地磷磷(PO4-P)年负荷量为217 ~ 296 t /年，南盆地为45 ~ 76 t /年，北盆地和南盆地SiO2年负荷量分别为16027 ~ 32655 t /年和2518 ~ 5490 t /年。
{"title":"Estimation of long-term external nutrient loading from watersheds to Lake Biwa by a combined rainfall-runoff model and loading-discharge curve approach","authors":"Huu Le Tien, K. Okubo, Phuong Tham Ho Thi, M. Saito","doi":"10.3178/hrl.14.143","DOIUrl":"https://doi.org/10.3178/hrl.14.143","url":null,"abstract":"External nutrient loadings to Lake Biwa were estimated using a combined tank model and loading-discharge curve approach. The model was applied to collective drainage basins of the lake’s Imazu (northwest), Hikone (northeast), and Otsu (south) areas. The hourly model was conducted using particular discharges from Kita (Ado) river, Takatoki (Ane) river, and Yasu River to obtain loading curves for phosphate (PO4) and silica (SiO2) by assimilating measured concentrations (2002–2003). The tank model was updated by adding an evapotranspiration routine and direct paths of groundwater discharges to the lake floor. The daily model was calibrated through analysis of water budget among the basin, inflow, lake and outflow, and then validated. The model was established and combined into a loadingdischarge curve to determine the long-term external nutri‐ ent loadings entering the lake (1980–2017). Seasonal varia‐ tion in nutrient loadings increased during spring and summer and decreased during winter. Annual phosphatephosphorus (PO4-P) loading ranged from 217 to 296 tons yr–1 in the North Basin and 45 to 76 tons yr–1 in the South Basin, while SiO2 loading fluctuated from 16,027 to 32,655 tons yr–1 and 2,518 to 5,490 tons yr–1 in the North and South Basins, respectively.","PeriodicalId":13111,"journal":{"name":"Hydrological Research Letters","volume":"14 1","pages":"143-149"},"PeriodicalIF":1.1,"publicationDate":"2020-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"69394265","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}
: Simulating flow dynamics in large-scale lakes is often time-consuming. For river flood simulation, the automatic domain updating (ADU), which can effectively control the simulation domain only in and around the flooded areas, has recently been developed. It is easily implementable without any computational errors for river flood simulation; however, its applicability to lake flow simulation with pre‐ cipitation/evapotranspiration has not been investigated. This study examines the applicability of the ADU to large-scale lake flow simulation with the 2-dimensional local inertial equations (2D-LIE) taking the Tonle Sap Lake, Cambodia, as a study site. The 2D-LIE with the ADU demonstrated 2.1 times faster simulation with errors less than 5.5%. This efficiency was achieved owing to the wet/dry seasonal nature of the tropical lake and backflow from the mainstream of the Mekong River in the rainy sea‐ son, suggesting that the ADU is applicable to large-scale lake flow simulation.
{"title":"An application of the automatic domain updating to the Tonle Sap Lake, Cambodia","authors":"Tomohiro Tanaka, H. Yoshioka","doi":"10.3178/hrl.14.68","DOIUrl":"https://doi.org/10.3178/hrl.14.68","url":null,"abstract":": Simulating flow dynamics in large-scale lakes is often time-consuming. For river flood simulation, the automatic domain updating (ADU), which can effectively control the simulation domain only in and around the flooded areas, has recently been developed. It is easily implementable without any computational errors for river flood simulation; however, its applicability to lake flow simulation with pre‐ cipitation/evapotranspiration has not been investigated. This study examines the applicability of the ADU to large-scale lake flow simulation with the 2-dimensional local inertial equations (2D-LIE) taking the Tonle Sap Lake, Cambodia, as a study site. The 2D-LIE with the ADU demonstrated 2.1 times faster simulation with errors less than 5.5%. This efficiency was achieved owing to the wet/dry seasonal nature of the tropical lake and backflow from the mainstream of the Mekong River in the rainy sea‐ son, suggesting that the ADU is applicable to large-scale lake flow simulation.","PeriodicalId":13111,"journal":{"name":"Hydrological Research Letters","volume":"1 1","pages":""},"PeriodicalIF":1.1,"publicationDate":"2020-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"69394413","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}
Hydrological responses due to deforestation in a humid tropical catchment were analyzed using two runoff genera‐ tion methods available in the Soil Water Assessment Tool (SWAT) model: the Curve Number (CN) and the GreenAmpt (GA) methods. The calibrated model, which per‐ formed well in simulating runoff under present land use condition in the Batanghari River Basin, Indonesia (42,960 km2), was then used to simulate runoff using past and future land use scenarios. Simulations showed similar changes in the annual water budget: decreasing evaporation and increasing total discharge. However, the two methods showed opposite changes in flow regimes: high flow increased (13%) under the CN while low flow increased (27%) under the GA. These results are associated with dif‐ ferences in runoff generation mechanisms, where surface runoff contributes to total discharge to a much larger extent under the CN (43%) than the GA (4%). Land use changes caused a reduction in infiltration rate, leading to higher high flow under the CN, while high flow did not change under the GA. Instead, lower evapotranspiration increased groundwater flow under the GA, and thus the steady low flow increased. This study suggests that the runoff genera‐ tion method should be selected carefully based on the dom‐ inant flow pathway of a catchment, particularly for land use impact studies in the humid tropics.
{"title":"Comparison of runoff generation methods for land use impact assessment using the SWAT model in humid tropics","authors":"E. Yamamoto, T. Sayama, Kodai Yamamoto, Apip","doi":"10.3178/hrl.14.81","DOIUrl":"https://doi.org/10.3178/hrl.14.81","url":null,"abstract":"Hydrological responses due to deforestation in a humid tropical catchment were analyzed using two runoff genera‐ tion methods available in the Soil Water Assessment Tool (SWAT) model: the Curve Number (CN) and the GreenAmpt (GA) methods. The calibrated model, which per‐ formed well in simulating runoff under present land use condition in the Batanghari River Basin, Indonesia (42,960 km2), was then used to simulate runoff using past and future land use scenarios. Simulations showed similar changes in the annual water budget: decreasing evaporation and increasing total discharge. However, the two methods showed opposite changes in flow regimes: high flow increased (13%) under the CN while low flow increased (27%) under the GA. These results are associated with dif‐ ferences in runoff generation mechanisms, where surface runoff contributes to total discharge to a much larger extent under the CN (43%) than the GA (4%). Land use changes caused a reduction in infiltration rate, leading to higher high flow under the CN, while high flow did not change under the GA. Instead, lower evapotranspiration increased groundwater flow under the GA, and thus the steady low flow increased. This study suggests that the runoff genera‐ tion method should be selected carefully based on the dom‐ inant flow pathway of a catchment, particularly for land use impact studies in the humid tropics.","PeriodicalId":13111,"journal":{"name":"Hydrological Research Letters","volume":"1 1","pages":""},"PeriodicalIF":1.1,"publicationDate":"2020-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.3178/hrl.14.81","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"69394463","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}
M. Zaki, K. Noda, Kengo Ito, Komariah, D. Ariyanto, M. Senge
: This study examined the effect of three organic amend‐ ments − compost (CP), sugarcane bagasse (SB), and rice husk ash (RA) − on soil moisture and maize growth in rainfed farmland under agricultural drought conditions in Central Java, Indonesia. The wet organic amendments were applied at a rate of 20 t ha –1 and mixed into the root zone 3 days before seeding. Chemical fertilizers were not included in any treatment during the experiment. CP and RA kept the soil moisture above the soil suction of pF 1.0 between initial planting and harvesting. By contrast, SB treatment exacerbated the impact of the agricultural drought com‐ pared with the control (CO) or no organic material. The maize yields of CP (690 kg ha –1 ) and RA (538 kg ha –1 ) were higher than those of CO (456 kg ha –1 ) and SB (382 kg ha –1 ); all yields were lower than the regional average in Central Java (698 kg ha –1 ). Maize yield was correlated with the lowest soil moisture value (R 2 = 0.80). Overall, CP and RA substantially reduced the damage to rain-fed farmland caused by agricultural drought. The lowest soil moisture value was a major explanatory factor with respect to the yield gap of maize under agricultural drought conditions.
本研究考察了三种有机改良剂——堆肥(CP)、甘蔗渣(SB)和稻壳灰(RA)——在农业干旱条件下对印度尼西亚中爪哇旱作农田土壤水分和玉米生长的影响。湿性有机改进剂在播种前3天以20 t / ha -1的速率施用于根区。在试验期间，不施用化肥。CP和RA在初种和收获期间使土壤水分保持在土壤吸力pF 1.0以上。相反，与对照(CO)或不施用有机物相比，SB处理加重了农业干旱的影响。CP (690 kg ha -1)和RA (538 kg ha -1)的玉米产量高于CO (456 kg ha -1)和SB (382 kg ha -1);所有产量都低于中爪哇的区域平均水平(698公斤公顷-1)。玉米产量与最低土壤水分呈显著正相关(r2 = 0.80)。总体而言，CP和RA大大减少了农业干旱对雨养农田的破坏。土壤水分最低是农业干旱条件下玉米产量缺口的主要解释因素。
{"title":"Effect of organic amendments on maize cultivation under agricultural drought conditions in Central Java, Indonesia","authors":"M. Zaki, K. Noda, Kengo Ito, Komariah, D. Ariyanto, M. Senge","doi":"10.3178/hrl.14.150","DOIUrl":"https://doi.org/10.3178/hrl.14.150","url":null,"abstract":": This study examined the effect of three organic amend‐ ments − compost (CP), sugarcane bagasse (SB), and rice husk ash (RA) − on soil moisture and maize growth in rainfed farmland under agricultural drought conditions in Central Java, Indonesia. The wet organic amendments were applied at a rate of 20 t ha –1 and mixed into the root zone 3 days before seeding. Chemical fertilizers were not included in any treatment during the experiment. CP and RA kept the soil moisture above the soil suction of pF 1.0 between initial planting and harvesting. By contrast, SB treatment exacerbated the impact of the agricultural drought com‐ pared with the control (CO) or no organic material. The maize yields of CP (690 kg ha –1 ) and RA (538 kg ha –1 ) were higher than those of CO (456 kg ha –1 ) and SB (382 kg ha –1 ); all yields were lower than the regional average in Central Java (698 kg ha –1 ). Maize yield was correlated with the lowest soil moisture value (R 2 = 0.80). Overall, CP and RA substantially reduced the damage to rain-fed farmland caused by agricultural drought. The lowest soil moisture value was a major explanatory factor with respect to the yield gap of maize under agricultural drought conditions.","PeriodicalId":13111,"journal":{"name":"Hydrological Research Letters","volume":"1 1","pages":""},"PeriodicalIF":1.1,"publicationDate":"2020-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"69393802","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}
K. Tsuruta, Y. Kosugi, M. Katsuyama, K. Kosugi, Masakazu Suzuki, M. Tani
: We quantified long-term trends in evapotranspiration, runoff, and deep percolation using 40 years of hydrological data, examining the effects of evapotranspiration on runoff during forest development in a coniferous species. Using the flow duration curve, we evaluated the effects of evapo‐ transpiration on the entire range of flow stages (high to low flows). During the 40-year forest development, deep perco‐ lation ranged from 97 mm to 105 mm. Annual evapotran‐ spiration increased by 623–766 mm, which appeared to be caused by increased air temperature as well as forest devel‐ opment. Annual runoff consequently decreased by 937– 777 mm. In particular, pronounced decreases in daily flow were found with an exceedance probability of >11% in the flow duration curve. Long-term effects of evapotranspira‐ tion on runoff during forest development continued for a longer period than predicted by previous catchment studies of ~20 years duration. Our results suggest that the long-term patterns of evapotranspiration and runoff during forest development would differ from those reported by previous catchment studies under climate warming conditions and highlight the need for further research into separating the effects of forest development and increasing air tempera‐ ture on evapotranspiration in long-term hydrological data.
{"title":"Long-term effects of evapotranspiration on the flow duration curve in a coniferous plantation forest over 40 years","authors":"K. Tsuruta, Y. Kosugi, M. Katsuyama, K. Kosugi, Masakazu Suzuki, M. Tani","doi":"10.3178/hrl.14.1","DOIUrl":"https://doi.org/10.3178/hrl.14.1","url":null,"abstract":": We quantified long-term trends in evapotranspiration, runoff, and deep percolation using 40 years of hydrological data, examining the effects of evapotranspiration on runoff during forest development in a coniferous species. Using the flow duration curve, we evaluated the effects of evapo‐ transpiration on the entire range of flow stages (high to low flows). During the 40-year forest development, deep perco‐ lation ranged from 97 mm to 105 mm. Annual evapotran‐ spiration increased by 623–766 mm, which appeared to be caused by increased air temperature as well as forest devel‐ opment. Annual runoff consequently decreased by 937– 777 mm. In particular, pronounced decreases in daily flow were found with an exceedance probability of >11% in the flow duration curve. Long-term effects of evapotranspira‐ tion on runoff during forest development continued for a longer period than predicted by previous catchment studies of ~20 years duration. Our results suggest that the long-term patterns of evapotranspiration and runoff during forest development would differ from those reported by previous catchment studies under climate warming conditions and highlight the need for further research into separating the effects of forest development and increasing air tempera‐ ture on evapotranspiration in long-term hydrological data.","PeriodicalId":13111,"journal":{"name":"Hydrological Research Letters","volume":"1 1","pages":""},"PeriodicalIF":1.1,"publicationDate":"2020-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"69394147","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 objective of this paper is to evaluate effects of strati‐ fied porous formation on solute dispersion using two-dimensional laboratory tracer tests. An image analysis tech‐ nique was used to analyze the solute dispersion processes and quantify the dispersivity and behaviors of forward and backward tails of solute plumes. Longitudinal dispersivity estimates for the stratified porous media increased with travel distance and are in reasonable agreement with previ‐ ous work. Moreover, in all of the stratified cases the trans‐ verse dispersivity exhibited a similar trend which decayed with travel distance. The summary of dispersivities esti‐ mated from this study and previous studies suggests that if both degree of heterogeneity and scale for stratified and randomly heterogeneous porous media are similar, the lon‐ gitudinal dispersivity is larger in stratified media than in randomly heterogeneous media. In order to quantify behav‐ iors of forward and backward tails, we defined the travel distances x 05 and x 95 corresponding to the 5th and 95th per‐ centiles, respectively, of the cumulative concentrations in the longitudinal direction, and found that the distance between x 05 and x 95 spread out linearly in the stratified cases.
{"title":"Experimental assessment of solute dispersion in stratified porous media","authors":"T. Kurasawa, Mariko Suzuki, Kazuya Inoue","doi":"10.3178/hrl.14.123","DOIUrl":"https://doi.org/10.3178/hrl.14.123","url":null,"abstract":": The objective of this paper is to evaluate effects of strati‐ fied porous formation on solute dispersion using two-dimensional laboratory tracer tests. An image analysis tech‐ nique was used to analyze the solute dispersion processes and quantify the dispersivity and behaviors of forward and backward tails of solute plumes. Longitudinal dispersivity estimates for the stratified porous media increased with travel distance and are in reasonable agreement with previ‐ ous work. Moreover, in all of the stratified cases the trans‐ verse dispersivity exhibited a similar trend which decayed with travel distance. The summary of dispersivities esti‐ mated from this study and previous studies suggests that if both degree of heterogeneity and scale for stratified and randomly heterogeneous porous media are similar, the lon‐ gitudinal dispersivity is larger in stratified media than in randomly heterogeneous media. In order to quantify behav‐ iors of forward and backward tails, we defined the travel distances x 05 and x 95 corresponding to the 5th and 95th per‐ centiles, respectively, of the cumulative concentrations in the longitudinal direction, and found that the distance between x 05 and x 95 spread out linearly in the stratified cases.","PeriodicalId":13111,"journal":{"name":"Hydrological Research Letters","volume":"29 1","pages":""},"PeriodicalIF":1.1,"publicationDate":"2020-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"69394203","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}
: Design rainfall depth, which is a fundamental index used in river planning, was estimated by rainfall obtained from super-ensemble simulations with bias correction, and the future change under 4 degree warming was projected. The modifications of existing bias correction methods were pro‐ posed to resolve the issue of overfitting and gap in size between reference and super-ensemble simulation data. A bias correction approach considering the bias between the historical experiment, the reference data, and the change between the historical and future experiments separately was defined as two-pass bias correction. The two-pass bias correction was performed with a moving window method that calculated moving average for time period and rank-order statistics. The result indicated that the approach pro‐ posed in this study estimates the design rainfall depth with a small error compared to that calculated without the moving window. The moving window method effectively resolves the issue of overfitting. The projection indicated that the range of projection among sea-surface temperature (SST) patterns is equivalent to 25% of the design rainfall depth for most basins and 60% for certain specific basins. The results indicate the importance of the appropriate bias correction and the consideration of range among the SST patterns for super-ensemble simulation data.
{"title":"Bias correction of d4PDF using a moving window method and their uncertainty analysis in estimation and projection of design rainfall depth","authors":"Satoshi Watanabe, Masafumi Yamada, Shiori Abe, Misako Hatono","doi":"10.3178/hrl.14.117","DOIUrl":"https://doi.org/10.3178/hrl.14.117","url":null,"abstract":": Design rainfall depth, which is a fundamental index used in river planning, was estimated by rainfall obtained from super-ensemble simulations with bias correction, and the future change under 4 degree warming was projected. The modifications of existing bias correction methods were pro‐ posed to resolve the issue of overfitting and gap in size between reference and super-ensemble simulation data. A bias correction approach considering the bias between the historical experiment, the reference data, and the change between the historical and future experiments separately was defined as two-pass bias correction. The two-pass bias correction was performed with a moving window method that calculated moving average for time period and rank-order statistics. The result indicated that the approach pro‐ posed in this study estimates the design rainfall depth with a small error compared to that calculated without the moving window. The moving window method effectively resolves the issue of overfitting. The projection indicated that the range of projection among sea-surface temperature (SST) patterns is equivalent to 25% of the design rainfall depth for most basins and 60% for certain specific basins. The results indicate the importance of the appropriate bias correction and the consideration of range among the SST patterns for super-ensemble simulation data.","PeriodicalId":13111,"journal":{"name":"Hydrological Research Letters","volume":"1 1","pages":""},"PeriodicalIF":1.1,"publicationDate":"2020-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"69394198","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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