Xu-Sheng Wang

Submarine fresh groundwater discharge into Laizhou Bay comparable to the Yellow River flux

Near- and off-shore fresh groundwater resources become increasingly important with the social and economic development in coastal areas. Although large scale (hundreds of km) submarine groundwater discharge (SGD) to the ocean has been shown to be of the same magnitude order as river discharge, submarine fresh groundwater discharge (SFGD) with magnitude comparable to large river discharge is never reported. Here, we proposed a method coupling mass-balance models of water, salt and radium isotopes based on field data of 223Ra, 226Ra and salinity to estimate the SFGD, SGD. By applying the method in Laizhou Bay (a water area of ~6000 km2), we showed that the SFGD and SGD are 0.57 ~ 0.88 times and 7.35 ~ 8.57 times the annual Yellow River flux in August 2012, respectively. The estimate of SFGD ranges from 4.12 × 107 m3/d to 6.36 × 107 m3/d, while SGD ranges from 5.32 × 108 m3/d to 6.20 × 108 m3/d. The proportion of the Yellow River input into Laizhou Bay was less than 14% of the total in August 2012. Our method can be used to estimate SFGD in various coastal waters.

A new analytical solution of topography‐driven flow in a drainage basin with depth‐dependent anisotropy of permeability

[1] Theoretical analysis and field observations suggest that the depth‐dependent trend of permeability anisotropy is a nature of the geological media accompanying the depth‐decaying permeability. However, the effect of depth‐dependent anisotropy has not been investigated in previous studies of regional groundwater flow. A more general analytical solution of topography‐driven flow in drainage basins is derived in this study. Exponential trend of permeability with depth is assumed, and different decay rates of horizontal permeability (kx) and vertical permeability (kz) are included to account for the depth‐dependent anisotropy. It is found that the shape of the nested flow systems in a drainage basin depends on not only the depth‐dependent permeability but also the depth‐dependentanisotropyratio(kx/kz).Forstagnationpointsbetweentheflowsystems,the number of stagnation points is not influenced by the depth‐dependent permeability and anisotropy; however, an increase in kx/kz can lead to a decrease in the depth of their location. When kx is smaller than kz on the top boundary, this phenomenon is especially significant.

Accumulation and transport of ammonium in aquitards in the Pearl River Delta (China) in the last 10,000 years: conceptual and numerical models

Generation, accumulation and migration of ammonium in the coastal aquifer-aquitard system of the Pearl River Delta, China, are a result of complex and long-term processes including sea-level changes, shoreline migration, sedimentation, decomposition of organic matter, solute-transport processes, and chemical reaction during the Holocene. Simulation of long-term ammonium distribution is not well addressed in the literature due to the difficulties in quantifying the complex geochemical processes. Salinity and ammonium profiles in the aquitards at two typical sites were obtained from geochemical analyses of soil and water samples. One-dimensional numerical models were used to integrate present knowledge of stratigraphy, historical evolution of the geological system during the Holocene, and the processes related to the generation and migration of ammonium. The ammonium generation and accumulation were approximated by an exponential function, and a moving boundary condition was used to reflect the sea-level changes during the Holocene. The observed salinity profiles were used to estimate flow and dispersion parameters, then the observed ammonium profiles were used to estimate the reactive parameters related to ammonium generation. The reasonably good match between the simulated and observed results demonstrates that the models can capture the dominant processes that control the generation and movement of ammonium.RésuméLa genèse, l’accumulation et la migration d’ammonium dans le système d’aquitards côtier du delta de la Rivière des Perles, Chine, sont le résultat de processus complexes à long terme incluant des changements de niveau marin, des migrations de la ligne côtière, la décomposition des matières organiques, des processus de transport de solutés, et des réactions chimiques durant l’Holocène. La simulation d’une distribution de l’ammonium à long terme n’est pas bien abordée dans la littérature en raison de la difficulté de quantifier les processus géochimiques complexes. Des profils de salinité ammonium dans les aquitards de deux sites typiques ont été obtenus à partir d’analyses géochimiques de sol et d’échantillons d’eau. Des modèles unidimensionnels ont été utilisés pour intégrer la connaissance actuelle de la stratigraphie, de l’évolution historique du système géologique durant l’Holocène, et les processus liés à la génération et à la migration de l’ammonium. La génération de l’ammonium et son accumulation ont fait l’objet d’approximation par une fonction exponentielle avec conditions aux limites variables pour prendre en compte les variations du niveau marin durant l’Holocène. Les profils de salinité observés sont été utilisés pour estimer débit et paramètres de dilution, puis les profils ammonium ont été utilisés pour estimer les paramètres contribuant à la génération de l’ammonium. La correspondance relativement bonne entre les résultats simulés et l’observation montre que le modèle peut représenter le processus dominant qui contrôle la genèse et le déplacement de l’ammonium.ResumenLa generación, migración y acumulación de amonio en el sistema acuífero – acuitardo del Delta del Río Pearl, China, son el resultado de procesos complejos y de largo plazo, incluyendo cambios del nivel del mar, migración de la línea de costa, sedimentación, descomposición de materia orgánica, procesos de transporte de soluto, y reacciones químicas durante el Holoceno. La simulación de la distribución a largo plazo del amonio no está bien abordada en la literatura debido a las dificultades en la cuantificación de los complejos procesos geoquímicos. Se obtuvieron perfiles de salinidad y de amonio en el acuitardo a partir de análisis geoquímicos y muestreos de agua en dos sitios típicos. Se usaron modelos numéricos unidimensionales para integrar el conocimiento actual de la estratigrafía, evolución histórica del sistema geológico durante el Holoceno, y los procesos relacionados a la generación y migración de amonio. La generación y la acumulación de amonio fueron aproximados por una función exponencial, y se usó una condición de borde en movimiento por reflejar el cambio del nivel de mar durante el Holoceno. Se usaron los perfiles de salinidad observados para estimar los parámetros de flujo y dispersión, luego se usaron los perfiles de amonio observados para estimar los parámetros reactivos relacionados con la generación de amonio. El razonablemente buen acuerdo logrado entre los resultados simulados y los observados demuestra que los modelos pueden capturar los procesos dominantes que controlan la generación y movimiento del amonio.摘要中国珠江三角洲滨海含水层-弱透水层系统中铵的形成、积累和运移,是全新世以来一系列复杂过程长期作用的结果,包括海平面升降、海岸线进退、沉积、有机质降解、溶质运移和化学反应等。由于定量刻画这些复杂地球化学过程存在困难,目前还很少有模拟铵的长期分布演化的文献。通过对两个典型场地土水样的水文地球化学分析,获得了弱透水层中盐分和铵的剖面分布特征。综合现有关于地层、全新世以来地质系统演变历史以及铵化反应方面的认识,本文提出了铵的累积运移过程的一维模型。铵的生成和累积用一个指数经验公式近似描述。采用移动上边界来表现全新世时期海平面的变化。首先利用观测的盐分剖面识别水流和水动力弥散参数,在此基础上利用观测的铵分布剖面来反演铵的生成反应参数。模拟结果与实测结果之间具有良好的一致性,这说明所提出的模型刻画了铵在弱透水层中积累和运移的主要过程。ResumoA geração, acumulação e migração de amónio no sistema costeiro aquífero-aquitardo do Delta do Rio Pearl, na China, são o resultado de processos complexos e de longo prazo, incluindo mudanças no nível do mar, migração da linha de costa, sedimentação, decomposição de matéria orgânica, processos de transporte de solutos e reações químicas durante o Holocénico. A simulação a longo prazo da distribuição de amónio não é bem abordada na literatura, devido às dificuldades em quantificar os complexos processos geoquímicos. Foram obtidos perfis de salinidade e de amónio nos aquitardos, em dois locais típicos, a partir de análises geoquímicas de amostras de solo e água. Foram usados modelos numéricos unidimensionais para integrar o conhecimento atual da estratigrafia, a evolução histórica do sistema geológico durante o Holocénico e os processos relacionados com a geração e migração de amónio. A geração e acumulação de amónio foram estimados por uma função exponencial, e foi usada uma condição fronteira móvel para refletir as mudanças do nível do mar durante o Holocénico. Os perfis de salinidade observados foram utilizados para estimar os parâmetros de fluxo e de dispersão, e, em seguida, os perfis observados de amónio foram utilizados para estimar os parâmetros reativos relacionados com a produção de amónio. A correspondência razoavelmente boa entre os resultados simulados e observados demonstra que os modelos podem capturar os processos dominantes que controlam a geração e a circulação de amónio.

Hydrological Cycle in the Heihe River Basin and Its Implication for Water Resource Management in Endorheic Basins

Endorheic basins around the world are suffering from water and ecosystem crisis. To pursue sustainable development, quantifying the hydrological cycle is fundamentally important. However, knowledge gaps exist in how climate change and human activities influence the hydrological cycle in endorheic basins. We used an integrated ecohydrological model, in combination with systematic observations, to analyze the hydrological cycle in the Heihe River Basin, a typical endorheic basin in arid region of China. The water budget was closed for different landscapes, river channel sections, and irrigation districts of the basin from 2001 to 2012. The results showed that climate warming, which has led to greater precipitation, snowmelt, glacier melt, and runoff, is a favorable factor in alleviating water scarcity. Human activities, including ecological water diversion, cropland expansion, and groundwater overexploitation, have both positive and negative effects. The natural oasis ecosystem has been restored considerably, but the overuse of water in midstream and the use of environmental flow for agriculture in downstream have exacerbated the water stress, resulting in unfavorable changes in surface-ground water interactions and raising concerns regarding how to fairly allocate water resources. Our results suggest that the water resource management in the region should be adjusted to adapt to a changing hydrological cycle, cropland area must be reduced, and the abstraction of groundwater must be controlled. To foster long-term benefits, water conflicts should be handled from a broad socioeconomic perspective. The findings can provide useful information on endorheic basins to policy makers and stakeholders around the world.

An analytical study on artesian flow conditions in unconfined-aquifer drainage basins

Although it has been reported that flowing artesian wells could be topographically controlled, there is no quantitative research on artesian flow conditions in unconfined aquifers. In this study, the water table, which has a lower amplitude than the land surface, is damped from the topography and used as the boundary condition to obtain the analytical solution of hydraulic head of a unit basin with a single flow system. The term artesian head is defined to characterize the condition of flowing artesian wells. The zone with positive artesian head is called artesian zone while with negative artesian head is nonartesian zone. The maximum artesian head and the size of artesian zones are found to increase with the damping factor and the anisotropy ratio, and decrease with the ratio of basin width to depth and the depth-decay exponent of hydraulic conductivity. Moreover, the artesian head increases with depth nearby the valley and decreases with depth near by the divide, and the variation rates are influenced by the decay exponent and the anisotropy ratio. Finally, the distribution of flowing artesian wells and the artesian head measurements in different depths of a borehole in a small catchment in the Ordos Plateau, Northwestern China is used to illustrate the theoretical findings. The change in artesian head with depth was used to estimate the anisotropy ratio and the decay exponent. This study opens up a new door to analyze basin-scale groundwater flow.

Numerical modeling of slug tests with MODFLOW using equivalent well blocks.

Slug tests are a widely used technique to estimate aquifer hydraulic parameters and the test data are generally interpreted with analytical solutions under various assumptions. However, these solutions are not convenient when slug tests are required to be analyzed in a three-dimensional model for complex aquifer-aquitard systems. In this study, equivalent well blocks (EWB) are proposed in numerical modeling of slug test data with MODFLOW. Multi-well slug tests in partially penetrating wells with skin zones can be simulated. Accuracy of the numerical method is demonstrated by benchmarking with analytical solutions. The EWB method is applied in a case study on slug tests in aquitards in the Pearl River Delta, China.

Groundwater contributions in water-salt balances of the lakes in the Badain Jaran Desert, China

Groundwater-fed lakes are essential for the ecology in arid and semiarid regions. As a typical arid region, the Badain Jaran Desert (BJD) is famous in the world for the presence of a large number of groundwater-fed saline lakes among the mega dunes. Based on the up to date geological surveys and observations, this study analyzed the groundwater contributions in water-salt balances of the lakes in the desert. We found different types of springs, including the sublacustrine springs that indicate an upward flow of groundwater under the lakebed. A simplified water balance model was developed to analyze the seasonal variations of water level in the SumuBarunJaran Lake, which revealed an approximately steady groundwater discharge in the lake and explained why the amplitude of seasonal changes in lake level is less than 0.5 m. In addition, a salt balance model was developed to evaluate the salt accumulations in the groundwater-fed lakes. The relative salt accumulation time is 800–7,000 years in typical saline lakes, which were estimated from the concentration of Cl−, indicating a long history evolution for the lakes in the BJD. Further researches are recommended to provide comprehensive investigations on the interactions between the lakes and groundwater in the BJD.

A theoretical analysis of basin-scale groundwater temperature distribution

The theory of regional groundwater flow is critical for explaining heat transport by moving groundwater in basins. Domenico and Palciauskas’s (1973) pioneering study on convective heat transport in a simple basin assumed that convection has a small influence on redistributing groundwater temperature. Moreover, there has been no research focused on the temperature distribution around stagnation zones among flow systems. In this paper, the temperature distribution in the simple basin is reexamined and that in a complex basin with nested flow systems is explored. In both basins, compared to the temperature distribution due to conduction, convection leads to a lower temperature in most parts of the basin except for a small part near the discharge area. There is a high-temperature anomaly around the basin-bottom stagnation point where two flow systems converge due to a low degree of convection and a long travel distance, but there is no anomaly around the basin-bottom stagnation point where two flow systems diverge. In the complex basin, there are also high-temperature anomalies around internal stagnation points. Temperature around internal stagnation points could be very high when they are close to the basin bottom, for example, due to the small permeability anisotropy ratio. The temperature distribution revealed in this study could be valuable when using heat as a tracer to identify the pattern of groundwater flow in large-scale basins. Domenico PA, Palciauskas VV (1973) Theoretical analysis of forced convective heat transfer in regional groundwater flow. Geological Society of America Bulletin 84:3803–3814RésuméLa théorie du flux souterrain régional est indispensable pour expliquer le transport de chaleur par mouvements d’eau souterraine dans les bassins. Domenico et Palciauskas (1973), pionniers dans l’étude du transport convectif de chaleur dans un bassin simple, assumaient que la convection avait une faible influence sur la redistribution des températures dans un aquifère. De plus, il n’y a pas eu de recherche se focalisant sur la distribution des températures près des zones de stagnation entre différents systèmes de flux. Dans cet article, la distribution des températures dans un bassin simple est réexaminée et de plus, celle d’un bassin complexe avec des systèmes de flux imbriqués est explorée. Dans ces deux bassins pour lesquels la distribution de la température due à la conduction est comparée, la convection entraine une baisse de température dans la plus grande partie du bassin à l’exception d’un petit secteur proche de la zone de décharge. Il existe une anomalie de hautes températures près du point de stagnation en fond de bassin où deux systèmes de flux convergent du fait d’un faible degré de convection et une distance de trajet importante. Par contre, il n’y a pas d’anomalie près du point de stagnation de fond de bassin lorsque deux systèmes de flux divergent. Dans le bassin complexe, il y a également une anomalie de fortes températures vers le point de stagnation interne. La température vers le point interne de stagnation peut être très élevée lorsqu’ils sont proches du fond du bassin du fait, par exemple, d’un faible rapport d’anisotropie de la perméabilité. La distribution de la température montrée dans cette étude peut être intéressante lorsque l’on utilise la chaleur comme un traceur pour identifier les schémas de circulation des flux souterrains dans de grands bassins. Domenico PA, Palciauskas VV (1973) Theoretical analysis of forced convective heat transfer in regional groundwater flow (Analyse théorique du transfert de chaleur par convection sous contraintes dans l’écoulement régional d’eaux souterraines). Geological Society of America Bulletin 84:3803–3814ResumenLa teoría del flujo regional de agua subterránea es crítica para explicar el transporte del calor por movimiento del agua subterránea en cuencas. El estudio pionero de Domenico y Palciauskas (1973) sobre transporte convectivo de calor en una cuenca simple asumió que la convección tenía una influencia pequeña en la redistribución de la temperatura en el agua subterránea. Más aún, no ha habido ninguna investigación enfocada en la distribución de la temperatura alrededor de las zonas de estancamiento entre los sistemas de flujo. En este trabajo, se reexamina la distribución de la temperatura en la cuenca simple y se explora dicha distribución en una cuenca compleja con sistemas de flujo anidados. Comparada con la distribución de la temperatura debido a la conducción, la convección en ambas cuenca lleva a temperaturas más bajas en la mayor parte de la cuenca excepto para una parte pequeña cercana a la zona de descarga. Existe una anomalía de alta temperatura alrededor del punto de estancamiento en el fondo de la cuenca donde dos sistema de flujo convergen debido a un bajo grado de convección y a una gran distancia de tránsito, pero no existe anomalía alrededor de un punto de estancamiento en el fondo de la cuenca donde dos sistemas de flujo divergen. En la cuenca compleja, también existen anomalías de alta temperatura alrededor de puntos internos de estancamiento. La temperatura alrededor de los puntos internos de estancamiento podría ser muy alta cuando ellos están cercanos al fondo de la cuenca, por ejemplo, debido a una baja relación entre permeabilidad y anisotropía. La distribución de temperatura revelada en este estudio podría ser valiosa al utilizar el calor como un trazador para identificar el esquema del flujo de agua subterránea en cuencas a gran escala. Domenico PA, Palciauskas VV (1973) Theoretical analysis of forced convective heat transfer in regional groundwater flow (Análisis teórico de la transferencia de calor por convección forzada en el flujo regional de agua subterránea). Geological Society of America Bulletin 84:3803–3814摘要区域地下水流理论对解释盆地内依靠地下水流动的热量传输过程至关重要。Domenico 和 Palciauskas (1973年)对一个简单盆地进行热对流传输的开拓性研究中, 假定对流对地下水温度的再分布影响很小。此外,对水流系统中滞流区周围的的温度分布还没有研究过。本文中,重新研究了简单盆地的温度分布规律,并对拥有多级次水流系统的复杂盆地进的温度分布规律开展了研究。在这两种盆地中,与传导造成的温度分布相比,除了排泄区附近很小一片区域外,对流将会使流域大部分地区的温度偏低。在两个水流系统汇聚的盆地底部驻点周围,由于对流程度较低及流动距离很长,存在着一个高温异常,但在两个水流系统分岔的盆地底部驻点周围,没有高温异常。在复杂盆地中,内部驻点周围也有高温异常。当内部驻点靠近盆地底部时,例如,由于渗透性各向异性比值很小,其周围的温度可能非常高。在利用温度作为示踪剂确定大尺度盆地地下水水流模式时,本研究所揭示的温度分布规律非常有价值。Domenico PA, Palciauskas VV (1973年),Theoretical analysis of forced convective heat transfer in regional groundwater flow (区域地下水流中强迫性对流热量转移的理论分析)。美国地质学会学报 84:3803–3814ResumoA teoria do fluxo de água subterrânea regional é crítica para explicar o transporte de calor através do movimento da água subterrânea nas bacias. O estudo pioneiro de Domenico e Palciauskas (1973) sobre transporte de calor convectivo numa bacia simples assumiu que a convecção tem uma influência diminuta na redistribuição da temperatura da água subterrânea. Para além disso, não tem havido pesquisa vocacionada para a distribuição de temperatura em redor de zonas de estagnação dentro dos sistemas de fluxo. Neste documento, a distribuição de temperatura na bacia simples é reexaminada e é explorada a mesma situação numa bacia complexa com sistemas de fluxo aninhados. Em ambas as bacias, em comparação com a distribuição de temperaturas devidas a condução, a convecção leva a temperaturas mais baixas na maior parte das bacias, exceto em pequenas zonas próximas das áreas de descarga. Existe uma grande anomalia de alta temperatura em redor do ponto de estagnação na base da bacia, onde dois sistemas de fluxo convergem devido ao baixo grau de convecção e à longa distância de circulação, mas não há anomalia em redor do ponto de estagnação da base da bacia onde os dois sistemas de fluxo divergem. Na bacia complexa existem também anomalias de alta temperatura em redor de pontos de estagnação internos. A temperatura em redor de pontos de estagnação internos pode ser muito elevada quando estes estão próximos da base da bacia, por exemplo devido a pequenos efeitos anisotrópicos na permeabilidade. A distribuição de temperatura revelada neste estudo pode ser valiosa quando se usa o calor como traçador para identificar o padrão de fluxo da água subterrânea em bacias a grande escala. Domenico PA, Palciauskas VV (1973) Theoretical analysis of forced convective heat transfer in regional groundwater flow [Análise teórica de transferência de calor convectivo forçado em fluxos regionais de água subterrânea]. Geological Society of America Bulletin 84:3803–3814

Groundwater and surface-water interactions and impacts of human activities in the Hailiutu catchment, northwest China

The interactions between groundwater and surface water have been significantly affected by human activities in the semi-arid Hailiutu catchment, northwest China. Several methods were used to investigate the spatial and temporal interactions between groundwater and surface water. Isotopic and chemical analyses of water samples determined that groundwater discharges to the Hailiutu River, and mass balance equations were employed to estimate groundwater seepage rates along the river using chemical profiles. The hydrograph separation method was used to estimate temporal variations of groundwater discharges to the river. A numerical groundwater model was constructed to simulate groundwater discharges along the river and to analyze effects of water use in the catchment. The simulated seepage rates along the river compare reasonably well with the seepage estimates derived from a chemical profile in 2012. The impacts of human activities (river-water diversion and groundwater abstraction) on the river discharge were analyzed by calculating the differences between the simulated natural groundwater discharge and the measured river discharge. Water use associated with the Hailiutu River increased from 1986 to 1991, reached its highest level from 1992 to 2000, and decreased from 2001 onwards. The reduction of river discharge might have negative impacts on the riparian ecosystem and the water availability for downstream users. The interactions between groundwater and surface water as well as the consequences of human activities should be taken into account when implementing sustainable water resources management in the Hailiutu catchment.RésuméLes interactions entre les eaux souterraines et les eaux de surface ont été affectées de manière significative par les activités anthropiques dans le bassin versant d’Hailiutu en contexte semi-aride, dans le Nord-Ouest de la Chine. Plusieurs méthodes ont été utilisées pour étudier les interactions spatio-temporelles entre les eaux souterraines et les eaux de surface. Les analyses isotopiques et chimiques des échantillons d’eau ont permis de déterminer que l’eaux souterraines alimentent la rivière Hailiutu, et les équations de bilan de masse ont été employées pour estimer le taux d’alimentation par les eaux souterraines le long de la rivière en utilisant des profils chimiques. La méthode de séparation d’hydrogramme a été utilisée pour estimer les variations temporelles de l’alimentation de la rivière par les eaux souterraines. Un modèle numérique de l’écoulement des eaux souterraines a été élaborée pour simuler l’alimentation par les eaux souterraines le long de la rivière et pour analyser les effets de l’utilisation des ressources en eau dans le bassin versant. Les taux d’alimentation simulés le long de la rivière s’accordent de façon raisonnable avec les estimations d’alimentation dérivées du profil chimique de 2012. Les impacts des activités anthropiques (diversion de l’eau de rivière et prélèvement en eaux souterraines) sur le débit de la rivière ont été analysés en calculant les différences entre l’alimentation naturelle simulée par les eaux souterraines et le débit mesuré de la rivière. L’utilisation de l’eau associées à la rivière Hailiutu a augmenté entre 1986 et 1991, atteignant son niveau le plus élevé entre 1992 et 2000, et décroissant à partir de 2001. La réduction du débit de la rivière peut avoir des impacts négatifs sur l’écosystème riverain et pour la disponibilité en eau pour les usagers situés en aval. Les interactions entre les eaux souterraines et les eaux de surface ainsi que les conséquences sur les activités anthropiques devraient être prises en considération lors de la mise en œuvre d’une gestion durable des ressources en eau dans le bassin versant d’Hailiutu.ResumenLas interacciones entre agua subterránea y agua superficial han sido afectadas significativamente por las actividades humanas en la cuenca semiárida de Hailiutu, noroeste de China. Se utilizaron varios métodos para investigar las interacciones espaciales y temporales entre el agua subterránea y el agua superficial. Los análisis isotópicos y químicos de las muestras de agua determinaron las descargas de agua subterránea al río Hailiutu y las ecuaciones del balance de masa fueron empleadas para estimar las tasas de filtración del agua subterránea a lo largo del río usando perfiles químicos. Se utilizó el método de separación de hidrogramas para estimar las variaciones temporales de las descargas de aguas subterráneas al río. Se construyó un modelo numérico de agua subterránea para simular las descargas de agua subterránea a lo largo del río y para analizar los efectos del uso del agua en la cuenca. Las tasas de filtración simuladas a lo largo del río se comparan razonablemente bien con las estimaciones de filtración derivadas de un perfil químico en 2012. Se analizaron los impactos de las actividades humanas (desvío de agua y captación de agua subterránea) en la descarga del río mediante el cálculo de las diferencias entre la descarga natural simulada del agua subterránea y la descarga de río medida. El uso del agua asociado con el río Hailiutu aumentó de 1986 a 1991, alcanzó su nivel más alto entre 1992 y 2000 y disminuyó a partir de 2001. La reducción de la descarga del río podría tener impactos negativos en el ecosistema ribereño y la disponibilidad de agua para los usuarios aguas abajo. Las interacciones entre el agua subterránea y el agua superficial, así como las consecuencias de las actividades humanas, deben tenerse en cuenta al aplicar una gestión sostenible de los recursos hídricos en la cuenca Hailiutu.摘要在中国西北地区半干旱的Hailiutu流域,地下水和地表水之间的相互作用受到人类活动的极大影响。采用几种方法调查了地下水和地表水之间时空上的相互作用。水样的同位素和化学分析确定地下水排泄到Hailiutu河,采用质量平衡方程利用化学剖面估算了沿河流的地下水渗入量。利用自记水位计分离方法估算了地下水排泄到河流的时间变化。建立了数值地下水模型模拟沿河流的地下水排泄,分析了流域内水利用的影响。沿河流的模拟渗入量与源自2012年化学剖面的渗入量估算结果对比良好。通过计算模拟的天然地下水排泄量和观测的河流排泄量之间的差,分析了人类活动(河水改道及地下水抽取)对河流排泄的影响。与Hailiutu河相关的水利用从1986年到1991年呈增加势态,从1992年到2000年达到最高水平,然后从2001年开始下降。河流排泄量的减少可能对河岸带生态系统及下游用水者的水利用量产生负面影响。在实施Hailiutu流域可持续的水源管理中,应该考虑地下水和地表水之间的相互作用以及人类活动的影响。ResumoAs interações entre águas subterrâneas e águas superficiais tem sido significativamente afetadas por atividades humanas na bacia hidrográfica semiárida de Hailutu, noroeste da China. Vários métodos foram utilizados para investigar as interações espaciais e temporais entre as águas subterrâneas e as águas superficiais. Análises químicas e isotópicas de amostras de água determinaram que as águas subterrâneas descarregam no Rio Hailiutu, e as equações do balanço de massa foram empregadas para estimar a infiltração de águas subterrâneas ao longo do rio utilizando perfis químicos. O método de separação do hidrograma foi utilizado para estimar as variações temporais da descarga de águas subterrâneas para o rio. Um modelo numérico de águas subterrâneas foi construído para simular a descarga de águas subterrâneas ao longo do rio e analisar os efeitos do uso da água na bacia. A taxa de infiltração estimada ao longo do rio se compara razoavelmente bem com as estimativas de infiltração derivadas de um perfil químico em 2012. Os impactos das atividades humanas (derivação de água do rio e captação de águas subterrâneas) na descarga do rio foram analisados calculando as diferenças entre a descarga natural simulada e a descarga medida no rio. Os usos da água associados ao Rio Hailiutu aumentaram de 1986 até 1991, atingindo seu mais alto nível entre 1992 até 2000, e decresceu de 2001 em diante. A redução na descarga do rio pode ter efeitos negativos no ecossistema ribeirinho e na disponibilidade de água para os usuários a jusante. As interações entre águas subterrâneas e águas superficiais, bem como as consequências das atividades humanas, devem ser levadas em conta ao implementar a gestão sustentável dos recursos hídricos na bacia de Hailiutu.

Parallelization of MODFLOW using a GPU library.

A new method based on a graphics processing unit (GPU) library is proposed in the paper to parallelize MODFLOW. Two programs, GetAb_CG and CG_GPU, have been developed to reorganize the equations in MODFLOW and solve them with the GPU library. Experimental tests using the NVIDIA Tesla C1060 show that a 1.6- to 10.6-fold speedup can be achieved for models with more than 10(5) cells. The efficiency can be further improved by using up-to-date GPU devices.