A. E. Brookfield

Implications of Hyporheic Flow on Temperature-Based Estimates of Groundwater/Surface Water Interactions

AbstractThe hyporheic zone has received significant attention in recent years due to its role in regulating the physical, chemical, and biological processes that buffer fluvial systems at a variety of scales. The exchange of water through the hyporheic zone is also important for the regulation of stream and streambed temperatures. Recent research has utilized stream and streambed temperatures to quantify groundwater discharge to streams using a variety of methods, including one-dimensional analytical solutions for vertical flux across the streambed interface. The presence of lateral flows, including hyporheic flow, will cause uncertainty in these analytical solution results. In this study, HydroGeoSphere, a three-dimensional, fully integrated surface/subsurface hydrologic model, is used to simulate the manner in which streambed heterogeneity influences groundwater/surface water interactions along a stream section, and the uncertainty of groundwater/surface water flux estimates based upon streambed tempera...

Effects of Changing Meteoric Precipitation Patterns on Groundwater Temperature in Karst Environments

Climate predictions indicate that precipitation patterns will change and average air temperatures will increase across much of the planet. These changes will alter surface water and groundwater temperatures which can significantly affect the local and regional environment. Here, we examine the role of precipitation timing in changes to groundwater temperature in carbonate-karst aquifers using measured groundwater level and temperature data from the Konza Prairie Long-Term Ecological Research Site, Kansas. We demonstrate that shifts to increased cool-season precipitation may mitigate the increases in groundwater temperature produced by increases in average annual air temperature. In karst, the solution-enlarged conduits allow faster and focused recharge, and the recharge-event temperature can strongly influence the groundwater temperature in the aquifer. Our field data and analysis show that predictions of future groundwater conditions in karst aquifers need to consider changes in precipitation patterns, in addition to changes to average annual air temperature.

Incorporating Surface Water Operations in an Integrated Hydrologic Model: Model Development and Application to the Lower Republican River Basin, United States

AbstractFew river systems remain unaltered by engineered water management structures. Yet research investigating the interdependence between natural and engineered components of a hydrologic system...

Importance of a sound hydrologic foundation for assessing the future of the High Plains Aquifer in Kansas

Steward et al. (1) assess the hydrologic and agricultural future of the High Plains Aquifer. We have many concerns about hydrologic aspects of their study and describe the most significant here.

Interpreting temporal variations in river response functions: an example from the Arkansas River, Kansas, USA

Groundwater/surface-water interactions can play an important role in management of water quality and quantity, but the temporal and spatial variability of these interactions makes them difficult to incorporate into conceptual models. There are simple methods for identifying the presence of groundwater/surface-water interactions; however, identifying flow mechanisms and pathways can be challenging. More complex methods are available to better identify these mechanisms and pathways but are often too time consuming or costly. In this work, a simple method for interpreting and identifying flow mechanisms and sources using temporal variations of river response functions is presented. This approach is demonstrated using observations from two sites along the Arkansas River in Kansas, USA. A change in flow mechanisms between the rising and falling limbs of river hydrographs was identified, along with a second surface-water source to the aquifer, a finding that was validated with stable isotope analyses.RésuméLes relations nappe–rivière peuvent jouer un rôle important dans la gestion de la quantité et de la qualité de l’eau, mais la variabilité spatiale et temporelle de ces interactions rend difficile leur prise en compte dans les modèles conceptuels. Il y a des méthodes simples pour identifier l’existence de relations nappe-rivière. Cependant, l’identification des mécanismes et voies d’écoulement peuvent constituer un défi. Des méthodes plus complexes sont disponibles pour mieux identifier ces mécanismes et voies de transfert, mais elles sont souvent trop chronophages et coûteuses. Dans ce travail, une méthode simple est présentée pour interpréter et identifier les mécanismes de transfert et leurs origines, en utilisant les variations temporelles des fonctions de réponse d’une rivière. Cette approche est démontrée en utilisant les observations effectuées pour deux sites sur le cours de la rivière Arkansas, au Kansas (Etats-Unis d’Amérique). Un changement des mécanismes d’écoulement entre les montées et descentes des hydrographes de la rivière a été identifié conjointement avec une deuxième origine d’eau de surface alimentant l’aquifère, un résultat qui a été validé par les analyses d’isotopes stables.ResumenLas interacciones agua subterránea–agua superficial pueden desempeñar un papel importante en el manejo de la calidad y cantidad del agua, pero la variabilidad temporal y espacial de estas interacciones hace que sea difícil incorporarlas en los modelos conceptuales. Existen métodos sencillos para identificar la presencia de las interacciones agua subterránea/agua superficial; Sin embargo, la identificación de los mecanismos y trayectorias de flujo puede ser un desafío. Existen métodos más complejos para identificar mejor estos mecanismos y trayectorias, pero a menudo insumen demasiado tiempo o son costosos. En este trabajo, se presenta un método sencillo para interpretar e identificar los mecanismos de flujo y los aportes utilizando las variaciones temporales de las funciones de las respuestas fluviales. Este enfoque se demuestra usando observaciones de dos sitios a lo largo del río Arkansas en Kansas, EEUU. Se identificó un cambio en los mecanismos de flujo entre las ramas ascendentes y descendentes de los hidrogramas del río, junto con un segundo aporte de agua superficial hacia el acuífero, hallazgo que fue validado con análisis de isótopos estables.摘要地下水/地表水相互作用在水的数量和质量管理中可以发挥重要的作用,这些相互作用的时空变化使其很难包含在概念模型中。有确定地下水/地表水相互作用是否存在的简单方法;然而,确定水流机理和水流通道具有挑战性。有更复杂的方法能够更好地确定这些机理和通道,但通常太费时或者代价太高。在本研究中,提出了采用河流响应功能的时间变化解译和确定河流机理和来源的一个简单方法。利用美国堪萨斯州阿肯色河两个地点的观测数据展示了该方法。确定了河流水位图上升和下降翼之间河流机理的变化,以及确定了第二个到含水层的地表水源,这个发现得到了稳定同位素分析的验证。ResumoInterações entre águas subterrâneas e superficiais podem desempenhar uma função importante na gestão da qualidade e da quantidade da água, mas a variabilidade temporal e espacial dessas interações as torna difíceis de incorporar à modelos conceituais. Existem métodos simples para identificar a presença de interações entre águas subterrâneas e superficiais; entretanto a identificação de fluxos e caminhos preferenciais pode ser desafiador. Métodos mais complexos estão disponíveis para uma melhor identificar esses mecanismos e caminhos preferenciais mas são geralmente dispendiosos em tempo ou custo. Nesse trabalho, apresenta-se um método simples para interpretar e identificar mecanismos de fluxo e fontes usando variações temporais de funções de resposta fluviais. Essa abordagem é demonstrada usando observações de dois locais ao longo do Rio Arkansas, Kansas, EUA. Uma mudança nos mecanismos de fluxo entre os membros ascendentes e descendentes dos hidrogramas do rio foi identificada, junto com uma segunda fonte de águas superficiais ao aquífero, uma discoberta que foi validada com análises de isótopos estáveis.

Model for how microbial methane generation can preserve early porosity in dolomite and limestone reservoirs

In some dolomite and limestone hydrocarbon reservoirs, protection from cementation is a primary factor in porosity preservation. We present a model in which methanogens (methane-producing microorganisms) produce methane gas (CH4[g]) that outgasses from solution in pore space, creating a two-phase system that reduces effective hydraulic conductivity (K), protecting pore space from cementation. Methanogens have been implicated in dolomite formation and can generate methane to fill pore space of a model near-surface carbonate sediment (37.5% primary porosity) with CH4(g) in 180 to 4650 yr, depending on nutrient levels. Gas generation results in occlusion of the aqueous phase from pore spaces and throats, creating a two-phase flow regime, reducing the effective hydraulic conductivity of model marine carbonate sand by about 50% (from 2.8 to 1.2 cm/day) in as little as 55 yr, therefore reducing aqueous fluid flow necessary for cementation. Despite rapid burial and complete cessation of methanogenesis, effective hydraulic conductivity could take more than 100,000 yr to return to its original value. If methanogenesis continues with burial, the effective hydraulic conductivity is reduced to zero (after 250 yr). Dolomites can preserve more primary porosity with depth than other carbonates. We propose that, in addition to increased structural resistance, a biogenic model exists for porosity preservation in dolomites that is linked to the activity of methanogens. This model represents specific end-member cases and illustrates the effect of methane buildup in relationship to the extent of reservoir diagenesis.

Using the Domenico Solution to Teach Contaminant Transport Modeling.

ABSTRACT The Domenico solution is a heuristic simplification of a solution to the transport equation. Although there is a growing consensus that the Domenico solution is undesirable for use in professional and research applications due to departures from exact solutions under certain conditions, it behaves well under conditions suitable for instruction. Moreover, the solution is easily programmed into spreadsheets, and incorporated into classroom exercises that illustrate the basic processes of advection, dispersion, retardation, evaluation of the error and complimentary error functions, sensitivity analyses, and Monte Carlo simulations. Exercises of these kinds provide students in introductory (e.g., students with no previous exposure to the subject) or intermediate courses (e.g., students having completed previous, related course work) with bottom-up experience preparing models, without a full commitment to learning a programming language. This frees the students to spend more time learning the physical processes, the parameter relationships, and experiencing the steps of moving from the equations to a computer code. A student survey and an instructor evaluation of a class project (class of 11 students) both indicated success in student learning at the levels desired for the course.