We present a contaminant treatment system (CTS) package for MODFLOW 6 that facilitates the simulation of pump-and-treat systems for groundwater remediation. Using the “nonintrusive” MODFLOW 6 application programming interface (API) capability, the CTS package can balance flows between extraction and injection wells within the outer flow solution loop and applies blended concentration/mass treatment efficiency within the outer transport solution loop. The former can be important when the requested extraction rate cannot be satisfied by the current simulated groundwater system conditions, while the latter can be important for simulating incomplete/imperfect treatment schemes. Furthermore, the CTS package allows users to temporally vary all aspects of a simulated CTS system, including the configuration and location of injection and extraction wells, and the CTS efficiency. This flexibility combined with the API-based implementation provide a generic and general CTS package that can be applied across the wide range of MODFLOW 6 simulation options and that evolves in step with MODFLOW 6 code modifications and advancements without needing to update the CTS package itself. 相似文献
Categorical parameter distributions consisting of geologic facies with distinct properties, for example, high-permeability channels embedded in a low-permeability matrix, are common at contaminated sites. At these sites, low-permeability facies store solute mass, acting as secondary sources to higher-permeability facies, sustaining concentrations for decades while increasing risk and cleanup costs. Parameter estimation is difficult in such systems because the discontinuities in the parameter space hinder the inverse problem. This paper presents a novel approach based on Traveling Pilot Points (TRIPS) and an iterative ensemble smoother (IES) to solve the categorical inverse problem. Groundwater flow and solute transport in a hypothetical aquifer with a categorical parameter distribution are simulated using MODFLOW 6. Heads and concentrations are recorded at multiple monitoring locations. IES is used to generate posterior ensembles assuming a TRIPS prior and an approximate multi-Gaussian prior. The ensembles are used to predict solute concentrations and mass into the future. The evaluation also includes an assessment of how the number of measurements and the choice of the geological prior determine the characteristics of the posterior ensemble and the resulting predictions. The results indicate that IES was able to efficiently sample the posterior distribution and showed that even with an approximate geological prior, a high degree of parameterization and history matching could lead to parameter ensembles that can be useful for making certain types of predictions (heads, concentrations). However, the approximate geological prior was insufficient for predicting mass. The analysis demonstrates how decision-makers can quantify uncertainty and make informed decisions with an ensemble-based approach. 相似文献
Hyporheic exchange is the interaction of river water and groundwater, and is difficult to predict. One of the largest contributions to predictive uncertainty for hyporheic exchange has been attributed to the representation of heterogeneous subsurface properties. Our study evaluates the trade-offs between intrinsic (irreducible) and epistemic (reducible) model errors when choosing between homogeneous and highly complex subsurface parameter structures. We modeled the Steinlach River Test Site in Southwest Germany using a fully coupled surface water-groundwater model to simulate hyporheic exchange and to assess the predictive errors and uncertainties of transit time distributions. A highly parameterized model was built, treated as a “virtual reality” and used as a reference. We found that if the parameter structure is too simple, it will be limited by intrinsic model errors. By increasing subsurface complexity through the addition of zones or heterogeneity, we can begin to exchange intrinsic for epistemic errors. Thus, the appropriate level of detail to represent the subsurface depends on the acceptable range of intrinsic structural errors for the given modeling objectives and the available site data. We found that a zonated model is capable of reproducing the transit time distributions of a more detailed model, but only if the geological structures are known. An interpolated heterogeneous parameter field (cf. pilot points) showed the best trade-offs between the two errors, indicating fitness for practical applications. Parameter fields generated by multiple-point geostatistics (MPS) produce transit time distributions with the largest uncertainties, however, these are reducible by additional hydrogeological data, particularly flux measurements. 相似文献
The spatial distribution of hydraulic properties in the subsurface controls groundwater flow and solute transport. However, many approaches to modeling these distributions do not produce geologically realistic results and/or do not model the anisotropy of hydraulic conductivity caused by bedding structures in sedimentary deposits. We have developed a flexible object-based package for simulating hydraulic properties in the subsurface—the Hydrogeological Virtual Realities (HyVR) simulation package. This implements a hierarchical modeling framework that takes into account geological rules about stratigraphic bounding surfaces and the geometry of specific sedimentary structures to generate realistic aquifer models, including full hydraulic-conductivity tensors. The HyVR simulation package can create outputs suitable for standard groundwater modeling tools (e.g., MODFLOW), is written in Python, an open-source programming language, and is openly available at an online repository. This paper presents an overview of the underlying modeling principles and computational methods, as well as an example simulation based on the Macrodispersion Experiment site in Columbus, Mississippi. Our simulation package can currently simulate porous media that mimic geological conceptual models in fluvial depositional environments, and that include fine-scale heterogeneity in distributed hydraulic parameter fields. The simulation results allow qualitative geological conceptual models to be converted into digital subsurface models that can be used in quantitative numerical flow-and-transport simulations, with the aim of improving our understanding of the influence of geological realism on groundwater flow and solute transport. 相似文献
Parameterization of wave runup is of paramount importance for an assessment of coastal hazards. Parametric models employ wave (e.g., Hs and Lp) and beach (i.e., β) parameters to estimate extreme runup (e.g., R2%). Thus, recent studies have been devoted to improving such parameterizations by including additional information regarding wave forcing or beach morphology features. However, the effects of intra-wave dynamics, related to the random nature of the wave transformation process, on runup statistics have not been incorporated. This work employs a phase- and depth- resolving model, based on the Reynolds-averaged Navier-Stokes equations, to investigate different sources of variability associated with runup on planar beaches. The numerical model is validated with laboratory runup data. Subsequently, the role of both aleatory uncertainty and other known sources of runup variability (i.e., frequency spreading and bed roughness) is investigated. Model results show that aleatory uncertainty can be more important than the contributions from other sources of variability such as the bed roughness and frequency spreading. Ensemble results are employed to develop a new parametric model which uses the Hunt (J Waterw Port Coastal Ocean Eng 85:123–152, 1959) scaling parameter \(\beta \left (H_{s}L_{p}\right )^{1/2}\).
We utilized an extensive data set (1977–2013) from a water quality monitoring program to investigate the recovery of a Danish estuary following large reductions in total phosphorus (TP) and total nitrogen (TN) loading. Monthly rates of net transport and biogeochemical transformation of dissolved inorganic nitrogen (DIN) and phosphorus (DIP) were computed in two basins of the estuary using a box model approach, and oxygen-based rates of net ecosystem production (NEP) were determined. Since 1990, nutrient loading was reduced by 58 % for nitrogen and 80 % for phosphorus, causing significant decreases in DIN (60 %) and DIP (85 %) concentrations. Reductions in nutrient loadings and concentrations reduced annual chlorophyll levels by 50 % in the inner estuary and improved Secchi depth by approximately 1 m during the same period, particularly in the summer period. In the outer, deeper region of the estuary trends in water quality was less evident. Improvements in the inner estuary were strongly coupled to declines in DIN. Thresholds of DIN and DIP concentrations limiting phytoplankton growth indicated that both regions of the estuary were nitrogen limited. NEP rates indicated the development of more net autotrophic conditions over time that were likely associated with higher benthic primary production stimulated by improved light conditions. Box model computations revealed a modest reduction in summer net production of DIP over time, despite the persistence of elevated fluxes for several years after external loads were reduced. Since the mid-1990s, nutrient loading and transformation were stable while nutrient concentrations continued to decline and water quality improved in the inner estuary. The oligotrophication trajectory involved an initial fast transformation and modest retention of nutrients followed by a gradual decline in the rate of improvement towards a new stable condition. 相似文献
The Consultative Committee for Space Data Systems (CCSDS), in 2002, released their first version of a Reference Model for an Open Archival Information System (OAIS). In 2003, the model was adopted by the International Standards Organization (ISO) as ISO 14721:2003. The CCSDS document was updated in 2012 with additional focus on verifying the authenticity of data and developing concepts of access rights and a security model. The OAIS model is the basis of research data management systems across institutions and disciplines around the world. The Organization for the Advancement of Structured Information Standards (OASIS), in 2006, released their first version of a Reference Model for Service Oriented Architecture (SOA). OASIS defines the SOA as “a paradigm for organizing and utilizing distributed capabilities that may be under the control of different ownership domains.” Systems designed around the SOA model benefit from improved scalability, flexibility, and agility. This paper applies the SOA model to the OAIS repository to describe how repositories can be implemented and extended through the use of services that may be internal or external to the host institution, including the consumption of network- or cloud-based services and resources. We use the Service Oriented Architecture (SOA) design paradigm to describe a set of potential extensions to OAIS Reference Model: purpose and justification for each extension, where and how each extension connects to the model, and an example of a specific service that meets the purpose. 相似文献
Abstract There are few published seismic (P- and S-waves) properties for seafloor bedrocks. At low pressures (1 to 10 MPa), velocities and attenuations are determined mainly by open microcracks. At higher pressures, the microcracks close, and the velocities and attenuations depend primarily on the matrix porosity. We have investigated both the relationships between the acoustic, petrophysical, and geological properties of the rocks at 40 MPa pressure and the effect of microcracks on the acoustic properties at 10 MPa pressure. In this paper we discuss the former; the latter will be discussed separately. P- and S-wave velocity and attenuation measurements were carried out on a suite of seabed sedimentary and igneous rocks at effective pressures from 10 to 40 MPa at ultrasonic frequencies. The porosities and permeabilities of the rocks ranged from 0% to 32% and 0 to 110 mDarcy, respectively. Characterization of the rocks revealed that most of the sandstones have a substantial clay content (kaolinite, illite, and chlorite) and fractures. Most of the igneous rocks are chloritized. The seismic properties of the rocks are markedly lower than those of similar continental rocks because of the microporosity formed by the alteration of feldspars, micas, and mafic minerals to clays (e.g., chloritization of pyroxenes) and the corresponding reduction of the elastic moduli. The results of this study suggest that the values of velocities and quality factors used for ocean acoustic propagation models are lower than normally assumed. 相似文献