The Three Gorges Reservoir (TGR) is one of the world's largest hydropower projects and plays an important role in water resources management in the Yangtze River. For the sake of disaster prevention and catchment management, it is crucial to understand the regulation capacity of the TGR on extreme hydrological events and its impact on flow regime in a changing climate. This study obtains historical inflows of the TGR from 1961 to 2019 and uses a distributed hydrological model to simulate the future inflows from 2021 to 2070. These data are adopted to drive a machine learning-based TGR operation model to obtain the simulated outflow with TGR operation, which are then compared with the natural flow without TGR operation to assess the impact of TGR. The results indicate that the average flood peaks and total flooding days in the historical period could have been reduced by 29.2% and 53.4% with the operation of TGR. The relative declines in drought indicators including duration and intensity were generally less than 10%. Faced with more severe extreme hydrological events in the future, the TGR is still expected to alleviate floods and droughts, but cannot bring them down to historical levels. The impact of TGR operation on flow regime will also evolve in a changing climate, potentially altering the habitats of river ecosystems. This study proposes feasible methods for simulating the operation of large reservoirs and quantifying the impact on flow regime, and provides insights for integrated watershed management in the upper Yangtze River basin.
{"title":"Quantifying the Regulation Capacity of the Three Gorges Reservoir on Extreme Hydrological Events and Its Impact on Flow Regime in a Changing Climate","authors":"Han Cheng, Taihua Wang, Dawen Yang","doi":"10.1029/2023wr036329","DOIUrl":"https://doi.org/10.1029/2023wr036329","url":null,"abstract":"The Three Gorges Reservoir (TGR) is one of the world's largest hydropower projects and plays an important role in water resources management in the Yangtze River. For the sake of disaster prevention and catchment management, it is crucial to understand the regulation capacity of the TGR on extreme hydrological events and its impact on flow regime in a changing climate. This study obtains historical inflows of the TGR from 1961 to 2019 and uses a distributed hydrological model to simulate the future inflows from 2021 to 2070. These data are adopted to drive a machine learning-based TGR operation model to obtain the simulated outflow with TGR operation, which are then compared with the natural flow without TGR operation to assess the impact of TGR. The results indicate that the average flood peaks and total flooding days in the historical period could have been reduced by 29.2% and 53.4% with the operation of TGR. The relative declines in drought indicators including duration and intensity were generally less than 10%. Faced with more severe extreme hydrological events in the future, the TGR is still expected to alleviate floods and droughts, but cannot bring them down to historical levels. The impact of TGR operation on flow regime will also evolve in a changing climate, potentially altering the habitats of river ecosystems. This study proposes feasible methods for simulating the operation of large reservoirs and quantifying the impact on flow regime, and provides insights for integrated watershed management in the upper Yangtze River basin.","PeriodicalId":23799,"journal":{"name":"Water Resources Research","volume":null,"pages":null},"PeriodicalIF":5.4,"publicationDate":"2024-06-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141333909","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
In streams, short-term element-specific solute fluxes are often not balanced with long-term chemical weathering fluxes determined in the residual solids from fractional element loss and denudation rate. The ratio of both estimates—the “Dissolved Export Efficiency” (DEE)—is frequently <1, indicating deficits in the stream dissolved load. To explore the cause of the stream deficits, we performed a daily water sampling campaign for one year in a forested headwater watershed in Southern Germany. We sampled surface runoff, above-canopy and below-canopy precipitation, subsurface flow from the organic soil layer, upper, and deep mineral soil, and groundwater. Regolith samples were obtained from a drill core and revealed the weathering front to lie between 7 and 15 m depth. We found a DEE < 1 for K, Si, Al, Fe. These elements are characterized by shallow slopes in C-Q relationships, and the imbalances were found to originate in the deep saprolite. Their export pathway potentially includes “hidden” Critical Zone compartments or fluxes, presumably unsampled colloids that are exported preferentially during rare flushing events with stochastic temporal distribution. The DEE of nutritive elements like Ca, Mg, and P is also <1. These elements are characterized by steeper C-Q slopes, and their imbalance can be explained by deep nutrient uptake followed by nutrient retainment in re-growing forest biomass or export in plant debris. The collective evidence for these imbalances, including previous evidence from metal stable isotopes, suggests that the deep Critical Zone represents the location for chemical or biogenic retention and release of solutes.
在溪流中，特定元素的短期溶质通量与根据元素损失率和剥蚀率确定的残余固体中长期化学风化通量往往不平衡。这两种估计值的比值--"溶解输出效率"（DEE）--经常为 1，表明溪流溶解负荷不足。为了探究溪流溶解负荷不足的原因，我们在德国南部一个森林覆盖的上游流域进行了为期一年的每日水样采集活动。我们采集了地表径流、树冠上和树冠下降水、来自有机土层、上层和深层矿质土壤的地下水流以及地下水样本。我们从钻孔岩芯中获取了岩石样本，发现风化前沿位于 7 至 15 米深处。我们发现 K、Si、Al、Fe 的 DEE < 1。这些元素在C-Q关系中具有浅斜率的特征，并且发现不平衡源自深部的溶蚀岩。它们的输出途径可能包括 "隐藏的 "临界区分区或通量，推测是在具有随机时间分布的罕见冲刷事件中优先输出的未取样胶体。钙、镁和磷等营养元素的 DEE 也是 1。这些元素的特点是 C-Q 斜率较陡，其失衡的原因可能是养分被深层吸收，然后养分被保留在重新生长的森林生物量中或随植物碎屑输出。这些不平衡现象的综合证据，包括以前的金属稳定同位素证据，表明深部临界区是溶质的化学或生物滞留和释放地点。
{"title":"Imbalances in Dissolved Elemental Export Fluxes Disclose “Hidden” Critical Zone Compartments","authors":"D. Uhlig, J. Sohrt, F. von Blanckenburg","doi":"10.1029/2023wr035517","DOIUrl":"https://doi.org/10.1029/2023wr035517","url":null,"abstract":"In streams, short-term element-specific solute fluxes are often not balanced with long-term chemical weathering fluxes determined in the residual solids from fractional element loss and denudation rate. The ratio of both estimates—the “Dissolved Export Efficiency” (DEE)—is frequently <1, indicating deficits in the stream dissolved load. To explore the cause of the stream deficits, we performed a daily water sampling campaign for one year in a forested headwater watershed in Southern Germany. We sampled surface runoff, above-canopy and below-canopy precipitation, subsurface flow from the organic soil layer, upper, and deep mineral soil, and groundwater. Regolith samples were obtained from a drill core and revealed the weathering front to lie between 7 and 15 m depth. We found a DEE < 1 for K, Si, Al, Fe. These elements are characterized by shallow slopes in C-Q relationships, and the imbalances were found to originate in the deep saprolite. Their export pathway potentially includes “hidden” Critical Zone compartments or fluxes, presumably unsampled colloids that are exported preferentially during rare flushing events with stochastic temporal distribution. The DEE of nutritive elements like Ca, Mg, and P is also <1. These elements are characterized by steeper C-Q slopes, and their imbalance can be explained by deep nutrient uptake followed by nutrient retainment in re-growing forest biomass or export in plant debris. The collective evidence for these imbalances, including previous evidence from metal stable isotopes, suggests that the deep Critical Zone represents the location for chemical or biogenic retention and release of solutes.","PeriodicalId":23799,"journal":{"name":"Water Resources Research","volume":null,"pages":null},"PeriodicalIF":5.4,"publicationDate":"2024-06-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141333810","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
David G. Litwin, Gregory E. Tucker, Katherine R. Barnhart, Ciaran J. Harman
Features of landscape morphology—including slope, curvature, and drainage dissection—are important controls on runoff generation in upland landscapes. Over long timescales, runoff plays an essential role in shaping these same features through surface erosion. This feedback between erosion and runoff generation suggests that modeling long-term landscape evolution together with dynamic runoff generation could provide insight into hydrological function. Here we examine the emergence of variable source area runoff generation in a new coupled hydro-geomorphic model that accounts for water balance partitioning between surface flow, subsurface flow, and evapotranspiration as landscapes evolve over millions of years. We derive a minimal set of dimensionless numbers that provide insight into how hydrologic and geomorphic parameters together affect landscapes. Across the parameter space we investigated, model results collapsed to a single inverse relationship between the dimensionless relief and the ratio of catchment quickflow to discharge. Furthermore, we found an inverse relationship between the Hillslope number, which describes topographic relief relative to aquifer thickness, and the proportion of the landscape that was variably saturated. While the model generally produces fluvial topography visually similar to simpler landscape evolution models, certain parameter combinations produce wide valley bottom wetlands and non-dendritic, trellis-like drainage networks, which may reflect real conditions in some landscapes where aquifer gradients become decoupled from topography. With these results, we demonstrate the power of hydro-geomorphic models for generating new insights into hydrological processes, and also suggest that subsurface hydrology may be integral for modeling aspects of long-term landscape evolution.
{"title":"Catchment Coevolution and the Geomorphic Origins of Variable Source Area Hydrology","authors":"David G. Litwin, Gregory E. Tucker, Katherine R. Barnhart, Ciaran J. Harman","doi":"10.1029/2023wr034647","DOIUrl":"https://doi.org/10.1029/2023wr034647","url":null,"abstract":"Features of landscape morphology—including slope, curvature, and drainage dissection—are important controls on runoff generation in upland landscapes. Over long timescales, runoff plays an essential role in shaping these same features through surface erosion. This feedback between erosion and runoff generation suggests that modeling long-term landscape evolution together with dynamic runoff generation could provide insight into hydrological function. Here we examine the emergence of variable source area runoff generation in a new coupled hydro-geomorphic model that accounts for water balance partitioning between surface flow, subsurface flow, and evapotranspiration as landscapes evolve over millions of years. We derive a minimal set of dimensionless numbers that provide insight into how hydrologic and geomorphic parameters together affect landscapes. Across the parameter space we investigated, model results collapsed to a single inverse relationship between the dimensionless relief and the ratio of catchment quickflow to discharge. Furthermore, we found an inverse relationship between the Hillslope number, which describes topographic relief relative to aquifer thickness, and the proportion of the landscape that was variably saturated. While the model generally produces fluvial topography visually similar to simpler landscape evolution models, certain parameter combinations produce wide valley bottom wetlands and non-dendritic, trellis-like drainage networks, which may reflect real conditions in some landscapes where aquifer gradients become decoupled from topography. With these results, we demonstrate the power of hydro-geomorphic models for generating new insights into hydrological processes, and also suggest that subsurface hydrology may be integral for modeling aspects of long-term landscape evolution.","PeriodicalId":23799,"journal":{"name":"Water Resources Research","volume":null,"pages":null},"PeriodicalIF":5.4,"publicationDate":"2024-06-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141333855","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Rumbidzai A. E. Nhunduru, Amir Jahanbakhsh, Omid Shahrokhi, Krystian L. Wlodarczyk, Susana Garcia, M. Mercedes Maroto-Valer
Continuum-scale models used to model and predict two-phase flow in the subsurface are often based on averaged flow parameters and do not consider pore-scale fluid flow phenomena, for example, ganglion dynamics and thin-film flow. As such, a major challenge in upscaling two-phase flow for groundwater engineering applications is understanding the impact of disconnected flow and ganglion dynamics on continuum-scale flow functions such as relative permeability-saturation and capillary pressure-saturation curves. In this study, we explored how changes in wettability and fluid velocity affect ganglion dynamics. We conducted pore-scale numerical simulations with OpenFOAM to investigate the displacement of decane by water. Additionally, we examined how displaced phase saturation (a continuum-scale flow function) responds to changes in dynamic fluid connectivity. We identified three different fluid flow regimes, that is, the connected pathway flow regime, ganglion dynamics (GD) flow regime, and droplet traffic flow regime, and studied the effects of changes in the wettability of the porous medium and the velocity of the invading fluid on the transitions between these different regimes. Our research showed that transitions between connected and disconnected pore-scale flow regimes, which are induced by changes in fluid velocity and wettability, have a significant impact on both fluid displacement efficiency and average fluid flow transport kinetics.
{"title":"Relating Pore-Scale Observations to Continuum-Scale Models: Impact of Ganglion Dynamics on Flow Transport Kinetics","authors":"Rumbidzai A. E. Nhunduru, Amir Jahanbakhsh, Omid Shahrokhi, Krystian L. Wlodarczyk, Susana Garcia, M. Mercedes Maroto-Valer","doi":"10.1029/2023wr035624","DOIUrl":"https://doi.org/10.1029/2023wr035624","url":null,"abstract":"Continuum-scale models used to model and predict two-phase flow in the subsurface are often based on averaged flow parameters and do not consider pore-scale fluid flow phenomena, for example, ganglion dynamics and thin-film flow. As such, a major challenge in upscaling two-phase flow for groundwater engineering applications is understanding the impact of disconnected flow and ganglion dynamics on continuum-scale flow functions such as relative permeability-saturation and capillary pressure-saturation curves. In this study, we explored how changes in wettability and fluid velocity affect ganglion dynamics. We conducted pore-scale numerical simulations with OpenFOAM to investigate the displacement of decane by water. Additionally, we examined how displaced phase saturation (a continuum-scale flow function) responds to changes in dynamic fluid connectivity. We identified three different fluid flow regimes, that is, the connected pathway flow regime, ganglion dynamics (GD) flow regime, and droplet traffic flow regime, and studied the effects of changes in the wettability of the porous medium and the velocity of the invading fluid on the transitions between these different regimes. Our research showed that transitions between connected and disconnected pore-scale flow regimes, which are induced by changes in fluid velocity and wettability, have a significant impact on both fluid displacement efficiency and average fluid flow transport kinetics.","PeriodicalId":23799,"journal":{"name":"Water Resources Research","volume":null,"pages":null},"PeriodicalIF":5.4,"publicationDate":"2024-06-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141333833","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Determining the sources of water inside plants using its isotopic composition is a long-standing research challenge in ecohydrology. A better understanding of water sources can help improve models and ultimately contribute to more accurate forecasts of water availability, food production, carbon sequestration or ecosystem status. Over the years, several methods have been developed and applied to water source partitioning, and Gai et al. (2023, https://doi.org/10.1029/2022wr033849) provide a systematic assessment of the uncertainty of different isotopic tracers (2H, 3H, 17O, 18O) and mixing models (IsoSource, SIAR, MixSIR, MixSIAR) for an apple tree orchard on the Loess Plateau in north-central China. For that study area, the combination of 2H and 18O with the MixSIAR mixing model is recommended. Importantly, the systematic assessment provides a framework that can be applied to select a suitable combination of tracers and mixing models for different ecosystems and climate zones. This commentary aims to provide a wider context for a selection of key results from Gai et al. (2023, https://doi.org/10.1029/2022wr033849) and highlight potential future research directions.
{"title":"Telling Tales of Water Journeys With Isotopic Tracers","authors":"Gerbrand Koren","doi":"10.1029/2024wr037033","DOIUrl":"https://doi.org/10.1029/2024wr037033","url":null,"abstract":"Determining the sources of water inside plants using its isotopic composition is a long-standing research challenge in ecohydrology. A better understanding of water sources can help improve models and ultimately contribute to more accurate forecasts of water availability, food production, carbon sequestration or ecosystem status. Over the years, several methods have been developed and applied to water source partitioning, and Gai et al. (2023, https://doi.org/10.1029/2022wr033849) provide a systematic assessment of the uncertainty of different isotopic tracers (<sup>2</sup>H, <sup>3</sup>H, <sup>17</sup>O, <sup>18</sup>O) and mixing models (IsoSource, SIAR, MixSIR, MixSIAR) for an apple tree orchard on the Loess Plateau in north-central China. For that study area, the combination of <sup>2</sup>H and <sup>18</sup>O with the MixSIAR mixing model is recommended. Importantly, the systematic assessment provides a framework that can be applied to select a suitable combination of tracers and mixing models for different ecosystems and climate zones. This commentary aims to provide a wider context for a selection of key results from Gai et al. (2023, https://doi.org/10.1029/2022wr033849) and highlight potential future research directions.","PeriodicalId":23799,"journal":{"name":"Water Resources Research","volume":null,"pages":null},"PeriodicalIF":5.4,"publicationDate":"2024-06-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141334599","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Quantitative estimates of hydrological state variables using electrical or electromagnetic geophysical methods are systematically biased by overlooked heterogeneity below the spatial scale resolved by the method. We generalize the high-salinity asymptotic limit of electrical conduction in porous media at the continuous (e.g., Darcy) scale, by introducing a new petrophysical parameter, the mixing factor M, which accounts for the effect of fluid conductivity heterogeneity on the equivalent electrical conductivity tensor; it is expressed in terms of the volume-average of the product of mean-removed fluid conductivity and electric fields. We investigate the behavior of M for static and evolving fluid conductivity scenarios. Considering 2-D ergodic log-normal random fields of fluid conductivity, we demonstrate, in absence of surface conductivity, that observing the components of the M-tensor allows univocally determining the variance and anisotropy of the field. Further, time-series of the M-tensor under diffusion-limited mixing allows distinguishing between different characteristic temporal scales of diffusion, which are directly related to the initial integral scales of the salinity field. Under advective-diffusive transport and for a pulse injection, the time-series of M have a strong dependence on the Péclet number. Since M is defined in the absence of surface conductivity, we investigate how to correct measurements for surface conductivity effects. The parameter M provides conceptual understanding about the impact of saline heterogeneity on electrical measurements. Further work will investigate how it can be incorporated into hydrogeophysical inverse formulations and interpretative frameworks.
使用电学或电磁地球物理方法对水文状态变量进行定量估算时，会因方法解析的空间尺度以下的被忽略的异质性而产生系统性偏差。我们在连续（如达西）尺度上对多孔介质中电导的高盐度渐近极限进行了概括，引入了一个新的岩石物理参数--混合因子 M，该因子考虑了流体电导率异质性对等效电导率张量的影响；它用平均去除的流体电导率与电场乘积的体积平均值表示。我们研究了 M 在静态和不断变化的流体电导情况下的行为。考虑到流体电导率的二维对数正态随机场，我们证明，在没有表面电导率的情况下，观察 M 张量的分量可以统一确定场的方差和各向异性。此外，在扩散受限的混合条件下，M 张量的时间序列可以区分扩散的不同特征时间尺度，这些尺度与盐度场的初始积分尺度直接相关。在平流扩散输运和脉冲注入条件下，M 的时间序列与佩克莱特数有很大关系。由于 M 是在没有表面传导性的情况下定义的，因此我们研究了如何校正测量结果的表面传导性效应。参数 M 使我们从概念上理解了盐水异质性对电学测量的影响。下一步工作将研究如何将其纳入水文地质物理反演公式和解释框架。
{"title":"An Electrical Parameter Characterizing Solute Heterogeneity: The Mixing Factor M","authors":"Alejandro Fernandez Visentini, Niklas Linde","doi":"10.1029/2023wr036059","DOIUrl":"https://doi.org/10.1029/2023wr036059","url":null,"abstract":"Quantitative estimates of hydrological state variables using electrical or electromagnetic geophysical methods are systematically biased by overlooked heterogeneity below the spatial scale resolved by the method. We generalize the high-salinity asymptotic limit of electrical conduction in porous media at the continuous (e.g., Darcy) scale, by introducing a new petrophysical parameter, the mixing factor <i>M</i>, which accounts for the effect of fluid conductivity heterogeneity on the equivalent electrical conductivity tensor; it is expressed in terms of the volume-average of the product of mean-removed fluid conductivity and electric fields. We investigate the behavior of <i>M</i> for static and evolving fluid conductivity scenarios. Considering 2-D ergodic log-normal random fields of fluid conductivity, we demonstrate, in absence of surface conductivity, that observing the components of the <i>M</i>-tensor allows univocally determining the variance and anisotropy of the field. Further, time-series of the <i>M</i>-tensor under diffusion-limited mixing allows distinguishing between different characteristic temporal scales of diffusion, which are directly related to the initial integral scales of the salinity field. Under advective-diffusive transport and for a pulse injection, the time-series of <i>M</i> have a strong dependence on the Péclet number. Since <i>M</i> is defined in the absence of surface conductivity, we investigate how to correct measurements for surface conductivity effects. The parameter <i>M</i> provides conceptual understanding about the impact of saline heterogeneity on electrical measurements. Further work will investigate how it can be incorporated into hydrogeophysical inverse formulations and interpretative frameworks.","PeriodicalId":23799,"journal":{"name":"Water Resources Research","volume":null,"pages":null},"PeriodicalIF":5.4,"publicationDate":"2024-06-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141333840","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Glenn A. Hodgkins, Benjamin Renard, Paul H. Whitfield, Gregor Laaha, Kerstin Stahl, Jamie Hannaford, Donald H. Burn, Seth Westra, Anne K. Fleig, Walszon Terllizzie Araújo Lopes, Conor Murphy, Luis Mediero, Martin Hanel
Understanding temporal trends in low streamflows is important for water management and ecosystems. This work focuses on trends in the occurrence rate of extreme low-flow events (5- to 100-year return periods) for pooled groups of stations. We use data from 1,184 minimally altered catchments in Europe, North and South America, and Australia to discern historical climate-driven trends in extreme low flows (1976–2015 and 1946–2015). The understanding of low streamflows is complicated by different hydrological regimes in cold, transitional, and warm regions. We use a novel classification to define low-flow regimes using air temperature and monthly low-flow frequency. Trends in the annual occurrence rate of extreme low-flow events (proportion of pooled stations each year) were assessed for each regime. Most regimes on multiple continents did not have significant (p < 0.05) trends in the occurrence rate of extreme low streamflows from 1976 to 2015; however, occurrence rates for the cold-season low-flow regime in North America were found to be significantly decreasing for low return-period events. In contrast, there were statistically significant increases for this period in warm regions of NA which were associated with the variation in the Pacific Decadal Oscillation. Significant decreases in extreme low-flow occurrence rates were dominant from 1946 to 2015 in Europe and NA for both cold- and warm-season low-flow regimes; there were also some non-significant trends. The difference in the results between the shorter (40-year) and longer (70-year) records and between low-flow regimes highlights the complexities of low-flow response to changing climatic conditions.
{"title":"Climate Driven Trends in Historical Extreme Low Streamflows on Four Continents","authors":"Glenn A. Hodgkins, Benjamin Renard, Paul H. Whitfield, Gregor Laaha, Kerstin Stahl, Jamie Hannaford, Donald H. Burn, Seth Westra, Anne K. Fleig, Walszon Terllizzie Araújo Lopes, Conor Murphy, Luis Mediero, Martin Hanel","doi":"10.1029/2022wr034326","DOIUrl":"https://doi.org/10.1029/2022wr034326","url":null,"abstract":"Understanding temporal trends in low streamflows is important for water management and ecosystems. This work focuses on trends in the occurrence rate of extreme low-flow events (5- to 100-year return periods) for pooled groups of stations. We use data from 1,184 minimally altered catchments in Europe, North and South America, and Australia to discern historical climate-driven trends in extreme low flows (1976–2015 and 1946–2015). The understanding of low streamflows is complicated by different hydrological regimes in cold, transitional, and warm regions. We use a novel classification to define low-flow regimes using air temperature and monthly low-flow frequency. Trends in the annual occurrence rate of extreme low-flow events (proportion of pooled stations each year) were assessed for each regime. Most regimes on multiple continents did not have significant (<i>p</i> < 0.05) trends in the occurrence rate of extreme low streamflows from 1976 to 2015; however, occurrence rates for the cold-season low-flow regime in North America were found to be significantly decreasing for low return-period events. In contrast, there were statistically significant increases for this period in warm regions of NA which were associated with the variation in the Pacific Decadal Oscillation. Significant decreases in extreme low-flow occurrence rates were dominant from 1946 to 2015 in Europe and NA for both cold- and warm-season low-flow regimes; there were also some non-significant trends. The difference in the results between the shorter (40-year) and longer (70-year) records and between low-flow regimes highlights the complexities of low-flow response to changing climatic conditions.","PeriodicalId":23799,"journal":{"name":"Water Resources Research","volume":null,"pages":null},"PeriodicalIF":5.4,"publicationDate":"2024-06-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141333892","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Bethany Cooper, Michael Burton, Lin Crase, Daniel Rigby
The world is more urbanized now than ever before and maintaining some form of amenity from natural or modified ecosystems in the urban context is an increasingly significant challenge. This is not aided by the somewhat amorphous definition of amenity itself. This article introduces a framework for conceptualizing the amenity of urban waterways and provides empirical evidence about the relative weight of the different determinants of waterway amenity. We use best-worst scaling to examine how households rate the relative importance of the amenity attributes along with data about how households rate their “connection” to waterways. Comparisons of preferences are made across four cities in Australia, all ranked in the top 10 most liveable cities in the World in 2021. The study also captures the relative importance of how “experts” in the field perceive these attributes. We find evidence that public preferences are not always aligned with those of experts and uncover significant heterogeneity within household respondents. To illustrate one way to cater for this heterogeneity in urban planning we report the results of a total unduplicated reach and frequency analysis as a means of identifying an efficacious portfolio of interventions. Accordingly, the study provides useful insights for waterway managers seeking to improve the allocation of resources and generate the most efficient amenity outcomes.
{"title":"Managing and Prioritizing Investments in Urban Waterways: Empirical Insights Into the Preferences of the Public and Experts","authors":"Bethany Cooper, Michael Burton, Lin Crase, Daniel Rigby","doi":"10.1029/2022wr033737","DOIUrl":"https://doi.org/10.1029/2022wr033737","url":null,"abstract":"The world is more urbanized now than ever before and maintaining some form of amenity from natural or modified ecosystems in the urban context is an increasingly significant challenge. This is not aided by the somewhat amorphous definition of amenity itself. This article introduces a framework for conceptualizing the amenity of urban waterways and provides empirical evidence about the relative weight of the different determinants of waterway amenity. We use best-worst scaling to examine how households rate the relative importance of the amenity attributes along with data about how households rate their “connection” to waterways. Comparisons of preferences are made across four cities in Australia, all ranked in the top 10 most liveable cities in the World in 2021. The study also captures the relative importance of how “experts” in the field perceive these attributes. We find evidence that public preferences are not always aligned with those of experts and uncover significant heterogeneity within household respondents. To illustrate one way to cater for this heterogeneity in urban planning we report the results of a total unduplicated reach and frequency analysis as a means of identifying an efficacious portfolio of interventions. Accordingly, the study provides useful insights for waterway managers seeking to improve the allocation of resources and generate the most efficient amenity outcomes.","PeriodicalId":23799,"journal":{"name":"Water Resources Research","volume":null,"pages":null},"PeriodicalIF":5.4,"publicationDate":"2024-06-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141333822","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Jung-Hwi Kihm, Jun-Mo Kim, Yongje Kim, Sung Kim, Gour-Tsyh Yeh
A series of hydrogeologic framework model (HFM)-based steady- and transient-state numerical simulations is performed first using a coupled subsurface flow-transport numerical model to analyze groundwater flow and salt transport in an actual three-dimensional complex coastal aquifer system before and during groundwater pumping. A series of analytic hierarchy process (AHP)-based multi-criteria evaluations is then performed applying a multi-criteria decision-making approach to determine optimal pumping location and rate for a new pumping well in the complex coastal aquifer system during groundwater pumping. The complex coastal aquifer system is composed of six anisotropic fractured porous geologic media (five rock formations and one fault) and three isotropic porous geologic media (three soil formations) and shows high geometric irregularity and significant heterogeneity and anisotropy of the nine geologic media. Results of the steady-state numerical simulations show successful model calibration with 26 measured groundwater levels and two observed seawater intrusion front lines. The latter two are determined by spatial interpolation and extrapolation of electrical conductivity logging data and electrical resistivity survey data, respectively. Based on the status and prospect of necessary water uses and available groundwater resources, the field observations of groundwater and seawater intrusion, and the analyses of the steady-state numerical simulation after the model calibration, six candidate pumping locations are selected for the new pumping well. In addition, from six preliminary individual transient-state numerical simulations, maximum pumping rates at the six candidate pumping locations are calculated first, and a set of six incremental candidate pumping rates is then assigned at each of the six candidate pumping locations. Results of the transients-state numerical simulations show that groundwater flow and salt transport are spatially and temporally changed, and seawater intrusion is further intensified by groundwater pumping. In addition, the magnitudes of such spatial and temporal changes and intensification are significantly different depending on the candidate pumping locations and rates. Results of the steady- and transient-state numerical simulations also show that both complexity (geometric irregularity, heterogeneity, and anisotropy including the fault) and topography have significant effects on the spatial distributions and temporal changes of groundwater flow and salt transport in the coastal aquifer system before and during groundwater pumping. In addition, results of statistical estimations of the mesh Peclet and Courant numbers confirm acceptabilities of minimizing numerical dispersion in the steady- and transient-state numerical simulations. Based on the analyses of the transient-state numerical simulations, eight multiple criteria are chosen to judge, prioritize, and rank the six candidate pumping locations and six candidate pu
{"title":"Hydrogeologic Framework Model-Based Numerical Simulation of Groundwater Flow and Salt Transport and Analytic Hierarchy Process-Based Multi-Criteria Evaluation of Optimal Pumping Location and Rate for Mitigation of Seawater Intrusion in a Complex Coastal Aquifer System","authors":"Jung-Hwi Kihm, Jun-Mo Kim, Yongje Kim, Sung Kim, Gour-Tsyh Yeh","doi":"10.1029/2023wr035486","DOIUrl":"https://doi.org/10.1029/2023wr035486","url":null,"abstract":"A series of hydrogeologic framework model (HFM)-based steady- and transient-state numerical simulations is performed first using a coupled subsurface flow-transport numerical model to analyze groundwater flow and salt transport in an actual three-dimensional complex coastal aquifer system before and during groundwater pumping. A series of analytic hierarchy process (AHP)-based multi-criteria evaluations is then performed applying a multi-criteria decision-making approach to determine optimal pumping location and rate for a new pumping well in the complex coastal aquifer system during groundwater pumping. The complex coastal aquifer system is composed of six anisotropic fractured porous geologic media (five rock formations and one fault) and three isotropic porous geologic media (three soil formations) and shows high geometric irregularity and significant heterogeneity and anisotropy of the nine geologic media. Results of the steady-state numerical simulations show successful model calibration with 26 measured groundwater levels and two observed seawater intrusion front lines. The latter two are determined by spatial interpolation and extrapolation of electrical conductivity logging data and electrical resistivity survey data, respectively. Based on the status and prospect of necessary water uses and available groundwater resources, the field observations of groundwater and seawater intrusion, and the analyses of the steady-state numerical simulation after the model calibration, six candidate pumping locations are selected for the new pumping well. In addition, from six preliminary individual transient-state numerical simulations, maximum pumping rates at the six candidate pumping locations are calculated first, and a set of six incremental candidate pumping rates is then assigned at each of the six candidate pumping locations. Results of the transients-state numerical simulations show that groundwater flow and salt transport are spatially and temporally changed, and seawater intrusion is further intensified by groundwater pumping. In addition, the magnitudes of such spatial and temporal changes and intensification are significantly different depending on the candidate pumping locations and rates. Results of the steady- and transient-state numerical simulations also show that both complexity (geometric irregularity, heterogeneity, and anisotropy including the fault) and topography have significant effects on the spatial distributions and temporal changes of groundwater flow and salt transport in the coastal aquifer system before and during groundwater pumping. In addition, results of statistical estimations of the mesh Peclet and Courant numbers confirm acceptabilities of minimizing numerical dispersion in the steady- and transient-state numerical simulations. Based on the analyses of the transient-state numerical simulations, eight multiple criteria are chosen to judge, prioritize, and rank the six candidate pumping locations and six candidate pu","PeriodicalId":23799,"journal":{"name":"Water Resources Research","volume":null,"pages":null},"PeriodicalIF":5.4,"publicationDate":"2024-06-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141333917","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Christian Moeck, Raoul A. Collenteur, Wouter R. Berghuijs, Elco Luijendijk, Jason J. Gurdak
Predictions of groundwater fluctuations in space and time are important for sustainable water resource management. Infiltration variability on monthly to decadal timescales leads to fluctuations in the water tables and thus groundwater resources. However, connections between global-scale climate variability and infiltration patterns and groundwater are often poorly understood because the relationships between groundwater conditions and infiltration tend to be highly nonlinear. In addition, understanding is further hampered because many groundwater records are incomplete and groundwater tables are often anthropogenically influenced, which makes identifying the effects of infiltration variability difficult. Previous studies that have evaluated how infiltration variability controls groundwater are based on a limited number of point measurements. Here, we present a global assessment of how infiltration variability is expected to affect groundwater tables. We use an analytical solution derived from Richards' equation to model water level responses to idealized periodic infiltration variability with periods that range from months to decades, to approximate both the effects of short-term and long-term climate variability and thus infiltration patterns. Our global-scale assessment reveals why infiltration variability would lead to periodicity in groundwater recharge in particular regions. The vadose zone strongly dampens short-term (seasonal and shorter) variations in infiltration fluxes throughout most of Earth's land surface, while infiltration cycles exceeding 1 year would yield transient recharge, except in more arid regions. Our results may help forecasting long-term groundwater tables and could support improving groundwater resource management.
{"title":"A Global Assessment of Groundwater Recharge Response to Infiltration Variability at Monthly to Decadal Timescales","authors":"Christian Moeck, Raoul A. Collenteur, Wouter R. Berghuijs, Elco Luijendijk, Jason J. Gurdak","doi":"10.1029/2023wr035828","DOIUrl":"https://doi.org/10.1029/2023wr035828","url":null,"abstract":"Predictions of groundwater fluctuations in space and time are important for sustainable water resource management. Infiltration variability on monthly to decadal timescales leads to fluctuations in the water tables and thus groundwater resources. However, connections between global-scale climate variability and infiltration patterns and groundwater are often poorly understood because the relationships between groundwater conditions and infiltration tend to be highly nonlinear. In addition, understanding is further hampered because many groundwater records are incomplete and groundwater tables are often anthropogenically influenced, which makes identifying the effects of infiltration variability difficult. Previous studies that have evaluated how infiltration variability controls groundwater are based on a limited number of point measurements. Here, we present a global assessment of how infiltration variability is expected to affect groundwater tables. We use an analytical solution derived from Richards' equation to model water level responses to idealized periodic infiltration variability with periods that range from months to decades, to approximate both the effects of short-term and long-term climate variability and thus infiltration patterns. Our global-scale assessment reveals why infiltration variability would lead to periodicity in groundwater recharge in particular regions. The vadose zone strongly dampens short-term (seasonal and shorter) variations in infiltration fluxes throughout most of Earth's land surface, while infiltration cycles exceeding 1 year would yield transient recharge, except in more arid regions. Our results may help forecasting long-term groundwater tables and could support improving groundwater resource management.","PeriodicalId":23799,"journal":{"name":"Water Resources Research","volume":null,"pages":null},"PeriodicalIF":5.4,"publicationDate":"2024-06-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141334639","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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