A number of rainfall-runoff models have been developed for hydraulic and hydrological engineering with an empha‐ sis on reproducing river discharge time series. Physicallybased rainfall-runoff models have recently reached a certain level of achievement following the advancement of com‐ puters and the development of various geographical and meteorological datasets. However, it has been pointed out that the current physically-based models do not properly reflect observed hillslope water dynamics. The present paper proposes a methodology to examine the capability of a depth-discharge constitutive equation for physicallybased rainfall-runoff modelling to simulate hillslope water dynamics. An application of the methodology suggested that 1) the targeted constitutive equation was capable of representing the depth-discharge relationship on hillslopes under the assumed conditions, 2) the runoff simulations with the constitutive equation described hillslope water flows, at least in the downward direction, and 3) there was a possibility that the parameters in the constitutive equation was determined from the internal structure of hillslope water dynamics.
{"title":"A methodology to examine a depth-discharge constitutive equation for rainfall-runoff modelling","authors":"Y. Ichikawa, H. An, Y. Tachikawa","doi":"10.3178/hrl.15.44","DOIUrl":"https://doi.org/10.3178/hrl.15.44","url":null,"abstract":"A number of rainfall-runoff models have been developed for hydraulic and hydrological engineering with an empha‐ sis on reproducing river discharge time series. Physicallybased rainfall-runoff models have recently reached a certain level of achievement following the advancement of com‐ puters and the development of various geographical and meteorological datasets. However, it has been pointed out that the current physically-based models do not properly reflect observed hillslope water dynamics. The present paper proposes a methodology to examine the capability of a depth-discharge constitutive equation for physicallybased rainfall-runoff modelling to simulate hillslope water dynamics. An application of the methodology suggested that 1) the targeted constitutive equation was capable of representing the depth-discharge relationship on hillslopes under the assumed conditions, 2) the runoff simulations with the constitutive equation described hillslope water flows, at least in the downward direction, and 3) there was a possibility that the parameters in the constitutive equation was determined from the internal structure of hillslope water dynamics.","PeriodicalId":13111,"journal":{"name":"Hydrological Research Letters","volume":"1 1","pages":""},"PeriodicalIF":1.1,"publicationDate":"2021-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"69394616","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}
: Global 500-m (18-arcsec) resolution cropland suitability was estimated using recently developed high-resolution global cropland data and a digital elevation model. The high-resolution estimation more precisely represented topo‐ graphical constraints to agriculture that were not adequately reflected in previous low-resolution estimates. It also suc‐ cessfully suppressed the overestimation of cropland suit‐ ability on areas with steep slopes. Furthermore, the distinc‐ tion of rainfed and irrigated cropland removed suitability overestimation induced by human agricultural intervention and enabled more natural and realistic estimation of crop‐ land suitability. The comparative analysis between the esti‐ mated land suitability and actual cropland distribution revealed that, if only natural condition is considered, it is possible to expand cropland area by 9.25 million km 2 , which is more than needed in the future while socio-economic factors controlling cropland suitability should be considered for more practical assessment. The newly developed highest-resolution cropland suitability map is expected to contribute to solving upcoming water, energy, and food issues, by integrating with water resource models and biomass studies.
{"title":"Global high-resolution estimation of cropland suitability and its comparative analysis to actual cropland distribution","authors":"Y. Ishikawa, Dai Yamazaki","doi":"10.3178/HRL.15.9","DOIUrl":"https://doi.org/10.3178/HRL.15.9","url":null,"abstract":": Global 500-m (18-arcsec) resolution cropland suitability was estimated using recently developed high-resolution global cropland data and a digital elevation model. The high-resolution estimation more precisely represented topo‐ graphical constraints to agriculture that were not adequately reflected in previous low-resolution estimates. It also suc‐ cessfully suppressed the overestimation of cropland suit‐ ability on areas with steep slopes. Furthermore, the distinc‐ tion of rainfed and irrigated cropland removed suitability overestimation induced by human agricultural intervention and enabled more natural and realistic estimation of crop‐ land suitability. The comparative analysis between the esti‐ mated land suitability and actual cropland distribution revealed that, if only natural condition is considered, it is possible to expand cropland area by 9.25 million km 2 , which is more than needed in the future while socio-economic factors controlling cropland suitability should be considered for more practical assessment. The newly developed highest-resolution cropland suitability map is expected to contribute to solving upcoming water, energy, and food issues, by integrating with water resource models and biomass studies.","PeriodicalId":13111,"journal":{"name":"Hydrological Research Letters","volume":"1 1","pages":""},"PeriodicalIF":1.1,"publicationDate":"2021-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"69394757","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. Hirabayashi, Haireti Alifu, Dai Yamazaki, Gennadii Donchyts, Yuki Kimura
Floods are major natural disasters that have considerable consequences worldwide. As the frequency and magnitude of flooding are expected to be affected by ongoing climate change, understanding their past changes is important for developing adequate adaptation measures. However, the limited spatiotemporal coverage of flood gauges hinders detection of changes in flooding, particularly in poorly gauged regions. Here, we propose a method using surface water data of river floodplain inundation as a proxy of the magnitude and frequency of flooding. Surface water data − Aqua Monitor which represented the probability linear trend changes in land and water surface area based on 30-m Landsat images between 1984–2000 and 2000–2013 was used in this study. The changes in water surface area over the floodplain obtained from Aqua Monitor showed high correspondence with historical trends observed or simulated annual maximum daily discharge, indicating the potential to detect changes in frequency and magnitude of flood from satellite data. In regions where changes could be measured with sufficient satellite images, 29% showed an increase in water surface area in the flood plain, 41% showed a decrease, and 30% showed small or no changes.
洪水是一种严重的自然灾害，在世界范围内造成严重后果。由于洪水的频率和强度预计将受到持续气候变化的影响，了解其过去的变化对于制定适当的适应措施非常重要。然而，洪水测量仪有限的时空覆盖范围阻碍了对洪水变化的探测，特别是在测量差的地区。在这里，我们提出了一种使用河流泛滥平原的地表水数据作为洪水强度和频率的代理的方法。−Aqua Monitor基于1984-2000年和2000-2013年的30 m Landsat影像，代表陆地和水面面积的概率线性趋势变化。Aqua Monitor获得的洪泛平原水面面积变化与观测或模拟的年最大日流量的历史趋势高度对应，表明可以从卫星数据检测洪水频率和强度的变化。在有足够的卫星图像可以测量变化的地区，29%的地区洪泛区水面面积增加，41%的地区减少，30%的地区变化很小或没有变化。
{"title":"Detectability of variation in river flood from satellite images","authors":"Y. Hirabayashi, Haireti Alifu, Dai Yamazaki, Gennadii Donchyts, Yuki Kimura","doi":"10.3178/hrl.15.37","DOIUrl":"https://doi.org/10.3178/hrl.15.37","url":null,"abstract":"Floods are major natural disasters that have considerable consequences worldwide. As the frequency and magnitude of flooding are expected to be affected by ongoing climate change, understanding their past changes is important for developing adequate adaptation measures. However, the limited spatiotemporal coverage of flood gauges hinders detection of changes in flooding, particularly in poorly gauged regions. Here, we propose a method using surface water data of river floodplain inundation as a proxy of the magnitude and frequency of flooding. Surface water data − Aqua Monitor which represented the probability linear trend changes in land and water surface area based on 30-m Landsat images between 1984–2000 and 2000–2013 was used in this study. The changes in water surface area over the floodplain obtained from Aqua Monitor showed high correspondence with historical trends observed or simulated annual maximum daily discharge, indicating the potential to detect changes in frequency and magnitude of flood from satellite data. In regions where changes could be measured with sufficient satellite images, 29% showed an increase in water surface area in the flood plain, 41% showed a decrease, and 30% showed small or no changes.","PeriodicalId":13111,"journal":{"name":"Hydrological Research Letters","volume":"1 1","pages":""},"PeriodicalIF":1.1,"publicationDate":"2021-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"69394574","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}
Low frequency (once a month) but long-term (ca. 6 years) sampling including snow-melt periods in a moun‐ tainous stream, the Okura River (Sendai, Japan), revealed that loadings of 5 parameters (COD, TN, TP, TOC and DSiO2) could be expressed exponentially using discharge (Q), while the coefficients for the 5 loadings were all about 1. Here, mathematically, the periodically averaged Q leads to approximation of that of load (L). We analyzed the bias of the spot Q to that of the periodical (30, 14 and 8 days) means. The results ensured the utilization of the spot Q instead of the periodical mean Q for estimating L because of the high correlation factors (0.872, 0.914 and 0.923 on 30-, 14-, 8-day mean Q analyses, respectively) and sug‐ gested the validity of the usage of the observed regression slopes of 1.06, 1.22, and 1.22 over 30, 14, 8 days for quan‐ titative correction of L because the fact that the slopes are larger than 1 indicate that the usage of the spot Q instead of the mean Q leads to the overestimation of L. Both changing correlation factors and the regression slopes realized small improvements via shortening the periods from 14 to 8 days. The protocol proposed here is quite original and is applica‐ ble to designing sampling strategies at target sites based on quantification of the limitations and/or reliability of L esti‐ mations.
{"title":"Analyzing the bias in dry weather spot flow rates to periodical mean flow rates in mountain streams: toward determining water pollution loads and optimizing water sampling strategies","authors":"Ami Tanno, S. Harada","doi":"10.3178/HRL.15.31","DOIUrl":"https://doi.org/10.3178/HRL.15.31","url":null,"abstract":"Low frequency (once a month) but long-term (ca. 6 years) sampling including snow-melt periods in a moun‐ tainous stream, the Okura River (Sendai, Japan), revealed that loadings of 5 parameters (COD, TN, TP, TOC and DSiO2) could be expressed exponentially using discharge (Q), while the coefficients for the 5 loadings were all about 1. Here, mathematically, the periodically averaged Q leads to approximation of that of load (L). We analyzed the bias of the spot Q to that of the periodical (30, 14 and 8 days) means. The results ensured the utilization of the spot Q instead of the periodical mean Q for estimating L because of the high correlation factors (0.872, 0.914 and 0.923 on 30-, 14-, 8-day mean Q analyses, respectively) and sug‐ gested the validity of the usage of the observed regression slopes of 1.06, 1.22, and 1.22 over 30, 14, 8 days for quan‐ titative correction of L because the fact that the slopes are larger than 1 indicate that the usage of the spot Q instead of the mean Q leads to the overestimation of L. Both changing correlation factors and the regression slopes realized small improvements via shortening the periods from 14 to 8 days. The protocol proposed here is quite original and is applica‐ ble to designing sampling strategies at target sites based on quantification of the limitations and/or reliability of L esti‐ mations.","PeriodicalId":13111,"journal":{"name":"Hydrological Research Letters","volume":"1 1","pages":""},"PeriodicalIF":1.1,"publicationDate":"2021-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"69394566","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}
Uncertainty in hydrological statistics estimated with finite observations, such as design rainfall, can be quanti‐ fied as a confidence interval using statistical theory. Ensemble climate data also enables derivation of a confi‐ dence interval. Recently, the database for policy decision making for future climate change (d4PDF) was developed in Japan, which contains dozens of simulated extreme rain‐ fall events for the past and 60 years into the future, allow‐ ing the uncertainty of design rainfall to be quantified as a confidence interval. This study applies an order statistics distribution to evaluate uncertainty in the order statistics of extreme rainfall from the perspective of mathematical theory, while a confidence interval is used for uncertainty evaluation in the probability distribution itself. An advan‐ tage of the introduction of an order statistics distribution is that it can be used to quantify the goodness-of-fit between observation and ensemble climate data under the condition that the extreme value distribution estimated from observa‐ tions is a true distribution. The order statistics distribution is called the control density distribution, which is derived from characteristics that order statistics from standard uni‐ form distribution follows beta distribution. The overlap ratio of the control density distribution and frequency dis‐ tributions derived from ensemble climate data is utilized for evaluation of the degree of goodness-of-fit for both data.
{"title":"Hydrological frequency analysis of large-ensemble climate simulation data using control density as a statistical control","authors":"Daiwei Cheng, K. Shimizu, Tomohito J. Yamada","doi":"10.3178/hrl.15.84","DOIUrl":"https://doi.org/10.3178/hrl.15.84","url":null,"abstract":"Uncertainty in hydrological statistics estimated with finite observations, such as design rainfall, can be quanti‐ fied as a confidence interval using statistical theory. Ensemble climate data also enables derivation of a confi‐ dence interval. Recently, the database for policy decision making for future climate change (d4PDF) was developed in Japan, which contains dozens of simulated extreme rain‐ fall events for the past and 60 years into the future, allow‐ ing the uncertainty of design rainfall to be quantified as a confidence interval. This study applies an order statistics distribution to evaluate uncertainty in the order statistics of extreme rainfall from the perspective of mathematical theory, while a confidence interval is used for uncertainty evaluation in the probability distribution itself. An advan‐ tage of the introduction of an order statistics distribution is that it can be used to quantify the goodness-of-fit between observation and ensemble climate data under the condition that the extreme value distribution estimated from observa‐ tions is a true distribution. The order statistics distribution is called the control density distribution, which is derived from characteristics that order statistics from standard uni‐ form distribution follows beta distribution. The overlap ratio of the control density distribution and frequency dis‐ tributions derived from ensemble climate data is utilized for evaluation of the degree of goodness-of-fit for both data.","PeriodicalId":13111,"journal":{"name":"Hydrological Research Letters","volume":"1 1","pages":""},"PeriodicalIF":1.1,"publicationDate":"2021-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"69394747","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}
H. Matsunaga, N. Matsuo, Takahisa Nakai, N. Yoshifuji, N. Tanaka, Katsunori Tanaka, C. Tantasirin
: Changes in stem circumference (SC) were observed in teak ( Tectona grandis ) in a tropical region during the dry season after tree-ring formation had stopped. We hypothe‐ sized that these SC changes were caused by water absorp‐ tion and emission from the outer bark surface. To test this hypothesis, we measured SC, heat pulse velocity (HPV), and leaf number using time series images in a teak tree plantation in northern Thailand. We also performed labora‐ tory experiments to observe changes in the weight and thickness of teak bark blocks under various vapor pressure conditions. Increases in teak tree SC were observed after rainfall during the dry season, when defoliation was almost complete and HPV was low. The weight and thickness of the bark blocks, on which all surfaces other than the outer bark were sealed, varied with water vapor content. These results suggest that water vapor absorption and emission through the outer bark surface can affect SC during the dry season. However, SC continued to increase after the vapor pressure deficit increased, and decreased more rapidly in the tree with higher HPV, suggesting that water exchange between the xylem and inner bark also contributes to changes in SC.
{"title":"Absorption and emission of water vapor from the bark of teak (Tectona grandis), a deciduous tree, in a tropical region during the dry season","authors":"H. Matsunaga, N. Matsuo, Takahisa Nakai, N. Yoshifuji, N. Tanaka, Katsunori Tanaka, C. Tantasirin","doi":"10.3178/hrl.15.58","DOIUrl":"https://doi.org/10.3178/hrl.15.58","url":null,"abstract":": Changes in stem circumference (SC) were observed in teak ( Tectona grandis ) in a tropical region during the dry season after tree-ring formation had stopped. We hypothe‐ sized that these SC changes were caused by water absorp‐ tion and emission from the outer bark surface. To test this hypothesis, we measured SC, heat pulse velocity (HPV), and leaf number using time series images in a teak tree plantation in northern Thailand. We also performed labora‐ tory experiments to observe changes in the weight and thickness of teak bark blocks under various vapor pressure conditions. Increases in teak tree SC were observed after rainfall during the dry season, when defoliation was almost complete and HPV was low. The weight and thickness of the bark blocks, on which all surfaces other than the outer bark were sealed, varied with water vapor content. These results suggest that water vapor absorption and emission through the outer bark surface can affect SC during the dry season. However, SC continued to increase after the vapor pressure deficit increased, and decreased more rapidly in the tree with higher HPV, suggesting that water exchange between the xylem and inner bark also contributes to changes in SC.","PeriodicalId":13111,"journal":{"name":"Hydrological Research Letters","volume":"1 1","pages":""},"PeriodicalIF":1.1,"publicationDate":"2021-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"69394626","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 streamflow under both high-and low-flows is required for versatile eco-hydrological modeling. Typical streamflow simulators require hydrological data such as river geometry and observed river discharge/water level as upstream/downstream boundary conditions. However, these are not always available in data-sparse regions. Further‐ more, because of the potential inaccuracy of digital eleva‐ tion model (DEM) data around water surfaces, this data has not generally been utilized in streamflow simulations. Therefore, this study explores the potential applicability of DEM data to extract river cross-sections, focusing on the upstream Hiikawa River, Japan. A 1-D streamflow simula‐ tion was performed using river cross-sections extracted from a 5 m LiDAR DEM and the observed dam discharge from 2018 to 2020 as the upstream boundary condition. The simulated water depths with Manning’s roughness coefficients of 0.03 to 0.05 m –1/3 s reproduce the observa‐ tion results with Nash-Sutcliffe coefficients of 0.91–0.97 for the whole period and 0.60–0.97 for a flood event. The accurate results for both low and high flows were consid‐ ered to reflect the reasonable representations of the river cross-section. Finally, the velocity-based suitability index for Ayu ( P. altivelis ) was evaluated. We demonstrate appli‐ cability and several possible limitations of DEM data for eco-hydrological modeling of data-scarce rivers.
:多用途的生态水文模型需要同时模拟高流量和低流量下的水流。典型的溪流模拟器需要水文数据，如河流几何形状和观察到的河流流量/水位作为上游/下游边界条件。然而，这些在数据稀疏的区域并不总是可用的。此外，由于水面附近的数字高程模型(DEM)数据可能存在不准确性，因此该数据通常未用于水流模拟。因此，本研究以日本Hiikawa河上游为研究对象，探讨了DEM数据在河流断面提取中的潜在适用性。利用从5 m LiDAR DEM中提取的河流断面和2018 - 2020年观测到的水坝流量作为上游边界条件，进行了一维水流模拟。Manning粗糙度系数为0.03 ~ 0.05 m -1/3 s的模拟水深再现了整个时期的Nash-Sutcliffe系数为0.91 ~ 0.97，一次洪水事件的Nash-Sutcliffe系数为0.60 ~ 0.97的观测结果。低流量和高流量的准确结果被认为反映了河流断面的合理表征。最后，对基于速度的阿玉适宜性指数进行了评价。我们展示了DEM数据在数据稀缺河流生态水文建模中的适用性和几个可能的局限性。
{"title":"DEM-based river cross-section extraction and 1-D streamflow simulation for eco-hydrological modeling: a case study in upstream Hiikawa River, Japan","authors":"Tomohiro Tanaka, H. Yoshioka, Y. Yoshioka","doi":"10.3178/hrl.15.71","DOIUrl":"https://doi.org/10.3178/hrl.15.71","url":null,"abstract":": Simulating streamflow under both high-and low-flows is required for versatile eco-hydrological modeling. Typical streamflow simulators require hydrological data such as river geometry and observed river discharge/water level as upstream/downstream boundary conditions. However, these are not always available in data-sparse regions. Further‐ more, because of the potential inaccuracy of digital eleva‐ tion model (DEM) data around water surfaces, this data has not generally been utilized in streamflow simulations. Therefore, this study explores the potential applicability of DEM data to extract river cross-sections, focusing on the upstream Hiikawa River, Japan. A 1-D streamflow simula‐ tion was performed using river cross-sections extracted from a 5 m LiDAR DEM and the observed dam discharge from 2018 to 2020 as the upstream boundary condition. The simulated water depths with Manning’s roughness coefficients of 0.03 to 0.05 m –1/3 s reproduce the observa‐ tion results with Nash-Sutcliffe coefficients of 0.91–0.97 for the whole period and 0.60–0.97 for a flood event. The accurate results for both low and high flows were consid‐ ered to reflect the reasonable representations of the river cross-section. Finally, the velocity-based suitability index for Ayu ( P. altivelis ) was evaluated. We demonstrate appli‐ cability and several possible limitations of DEM data for eco-hydrological modeling of data-scarce rivers.","PeriodicalId":13111,"journal":{"name":"Hydrological Research Letters","volume":"1 1","pages":""},"PeriodicalIF":1.1,"publicationDate":"2021-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"69394643","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}
Guesh Zeru, T. Alamirew, H. Shishaye, Megersa Olmana, N. Tadesse, Michael J. Reading
In this study, the Hydrograph Analysis: Rainfall and Time-Trends (HARTT) model was used to determine the contribution of climatic and non-climatic stresses on groundwater levels in the Lake Haramaya well-field, Ethio‐ pia. Monthly precipitation and monitored water-level data were used as explanatory variables of the method. Variabil‐ ity in rainfall explained 81.3% of groundwater levels using 2-month average time-delay. The coefficient of the impact of rainfall on groundwater level (K1) was found to be 0.00562 ± 0.0007 mm. This K1 value indicates that a 1 mm increase in rainfall from the annual average rainfall raises the groundwater-level by 0.00562 ± 0.0007 mm, while 1 mm decrease in rainfall causes a 0.00562 ± 0.0007 mm drop in groundwater-level in the area. However, the aver‐ age falling trend of the groundwater level (K2) was 1.51 ± 0.133 m/year, even with rainfall causing water-levels to rise between 1.01 to 3.29 m/year. With decreased rainfall, rainfall accounted for about 19.5% of the total-drawdown, while 80.5% was due to cumulative effects of non-climatic variables. This shows that rainfall inputs are negated by cumulative non-climatic stresses leading to the long-term net decline in groundwater level. Projected water-level results show that groundwater levels will be below pump‐ ing positions in <24 years which may have dire conse‐ quences for local landowners.
{"title":"Groundwater level trend analysis using the statistical auto-regressive HARTT method","authors":"Guesh Zeru, T. Alamirew, H. Shishaye, Megersa Olmana, N. Tadesse, Michael J. Reading","doi":"10.3178/hrl.14.17","DOIUrl":"https://doi.org/10.3178/hrl.14.17","url":null,"abstract":"In this study, the Hydrograph Analysis: Rainfall and Time-Trends (HARTT) model was used to determine the contribution of climatic and non-climatic stresses on groundwater levels in the Lake Haramaya well-field, Ethio‐ pia. Monthly precipitation and monitored water-level data were used as explanatory variables of the method. Variabil‐ ity in rainfall explained 81.3% of groundwater levels using 2-month average time-delay. The coefficient of the impact of rainfall on groundwater level (K1) was found to be 0.00562 ± 0.0007 mm. This K1 value indicates that a 1 mm increase in rainfall from the annual average rainfall raises the groundwater-level by 0.00562 ± 0.0007 mm, while 1 mm decrease in rainfall causes a 0.00562 ± 0.0007 mm drop in groundwater-level in the area. However, the aver‐ age falling trend of the groundwater level (K2) was 1.51 ± 0.133 m/year, even with rainfall causing water-levels to rise between 1.01 to 3.29 m/year. With decreased rainfall, rainfall accounted for about 19.5% of the total-drawdown, while 80.5% was due to cumulative effects of non-climatic variables. This shows that rainfall inputs are negated by cumulative non-climatic stresses leading to the long-term net decline in groundwater level. Projected water-level results show that groundwater levels will be below pump‐ ing positions in <24 years which may have dire conse‐ quences for local landowners.","PeriodicalId":13111,"journal":{"name":"Hydrological Research Letters","volume":"14 1","pages":"17-22"},"PeriodicalIF":1.1,"publicationDate":"2020-01-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.3178/hrl.14.17","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48070792","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}
H. Matsuyama, Jiei Flores, Kosuke Oikawa, Kengo Miyaoka
: This study compared precipitable water vapor (PWV) of JRA-55 and GPS in Japan by considering different eleva‐ tions in JRA-55 (geopotential height) and GPS (antenna height) because JRA-55’s PWV is pointed out to be under‐ estimated as a result of dry bias in the middle and upper troposphere in the forecast model. We selected 26 grid points of JRA-55 over Japanese islands and the respective nearest 26 GPS stations operated by the Geospatial Infor‐ mation Authority of Japan. First, we linearly converted the geopotential height of 26 grid points to air pressure at the antenna height, assuming the sea surface and 1500-m height corresponding to 1013.25 hPa and 850 hPa, respec‐ tively. We then calculated JRA-55’s PWV by vertically integrating specific humidity in the pressure coordinate sys‐ tem using the antenna height from July 2010 through December 2012 (designated as “corrected PWV”). At 22 grid points among the 26, the geopotential height is higher than the antenna height, where the majority of the data of PWV provided by the JRA project was smaller than that retrieved from GPS. The underestimation of the corrected PWV decreased, although 65% of them remained under‐ estimated. The underestimation of the corrected PWV increased in winter and decreased in summer.
{"title":"Comparison of precipitable water via JRA-55 and GPS in Japan considering different elevations","authors":"H. Matsuyama, Jiei Flores, Kosuke Oikawa, Kengo Miyaoka","doi":"10.3178/hrl.14.9","DOIUrl":"https://doi.org/10.3178/hrl.14.9","url":null,"abstract":": This study compared precipitable water vapor (PWV) of JRA-55 and GPS in Japan by considering different eleva‐ tions in JRA-55 (geopotential height) and GPS (antenna height) because JRA-55’s PWV is pointed out to be under‐ estimated as a result of dry bias in the middle and upper troposphere in the forecast model. We selected 26 grid points of JRA-55 over Japanese islands and the respective nearest 26 GPS stations operated by the Geospatial Infor‐ mation Authority of Japan. First, we linearly converted the geopotential height of 26 grid points to air pressure at the antenna height, assuming the sea surface and 1500-m height corresponding to 1013.25 hPa and 850 hPa, respec‐ tively. We then calculated JRA-55’s PWV by vertically integrating specific humidity in the pressure coordinate sys‐ tem using the antenna height from July 2010 through December 2012 (designated as “corrected PWV”). At 22 grid points among the 26, the geopotential height is higher than the antenna height, where the majority of the data of PWV provided by the JRA project was smaller than that retrieved from GPS. The underestimation of the corrected PWV decreased, although 65% of them remained under‐ estimated. The underestimation of the corrected PWV increased in winter and decreased in summer.","PeriodicalId":13111,"journal":{"name":"Hydrological Research Letters","volume":"1 1","pages":""},"PeriodicalIF":1.1,"publicationDate":"2020-01-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.3178/hrl.14.9","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46230019","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":"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":"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}
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