First‐order exchange coefficient coupling for simulating surface water–groundwater interactions: parameter sensitivity and consistency with a physics‐based approach

Distributed hydrologic models capable of simulating fully‐coupled surface water and groundwater flow are increasingly used to examine problems in the hydrologic sciences. Several techniques are currently available to couple the surface and subsurface; the two most frequently employed approaches are first‐order exchange coefficients (a.k.a., the surface conductance method) and enforced continuity of pressure and flux at the surface‐subsurface boundary condition. The effort reported here examines the parameter sensitivity of simulated hydrologic response for the first‐order exchange coefficients at a well‐characterized field site using the fully coupled Integrated Hydrology Model (InHM). This investigation demonstrates that the first‐order exchange coefficients can be selected such that the simulated hydrologic response is insensitive to the parameter choice, while simulation time is considerably reduced. Alternatively, the ability to choose a first‐order exchange coefficient that intentionally decouples the surface and subsurface facilitates concept‐development simulations to examine real‐world situations where the surface‐subsurface exchange is impaired. While the parameters comprising the first‐order exchange coefficient cannot be directly estimated or measured, the insensitivity of the simulated flow system to these parameters (when chosen appropriately) combined with the ability to mimic actual physical processes suggests that the first‐order exchange coefficient approach can be consistent with a physics‐based framework. Copyright © 2009 John Wiley & Sons, Ltd.     

Porphyrins in black trona water

Metalloporphyrins have been found in black trona water, a solution of sodium salts of organic acids occurring naturally in the Green River Formation of Wyoming. The porphyrins consist largely of nickel deoxophylloerythrin, a C-33 acid, and two lower methylene homologues, C-32 and C-31 acids, and possibly structural isomers of these. The C-32 acid is noticeably more abundant than either the C-33 or C-31 acids. Minor amounts of nickel etioporphyrins also are present. These porphyrins are believed to have been derived from the chlorophyll α synthesized by algae that inhabited Eocene Lake Gosiute. The transformations to porphyrins occurred under the influence of high pH, a reducing environment, and geological time.     

Nickel porphyrins in the bedding planes of a Colorado lean oil shale

A Colorado lean oil shale was found to have red-colored material on the faces of bedding planes and fractures. This red material is almost entirely the nickel chelate of a single C-29 porphyrin of deoxophylloerythroetioporphyrin type. The molecular weight of the chelate is 490 or 492, depending on which of the two major isotopes of nickel is chelated. A small amount of a methylene homologue 14 mass units higher in molecular weight is also present. Porphyrins extracted from the powdered shale are an extended homologous series of deoxophylloerythroetioporphyrin-type and possibly etio-type nickel porphyrins, as determined by mass spectrometry. The origin of the red porphyrins coating the shale fractures and bedding planes therefore was exogenous to these particular shale samples.     

Multiple-methods investigation of recharge at a humid-region fractured rock site,Pennsylvania, USA

Lysimeter-percolate and well-hydrograph analyses were combined to evaluate recharge for the Masser Recharge Site (central Pennsylvania, USA). In humid regions, aquifer recharge through an unconfined low-porosity fractured-rock aquifer can cause large magnitude water-table fluctuations over short time scales. The unsaturated hydraulic characteristics of the subsurface porous media control the magnitude and timing of these fluctuations. Data from multiple sets of lysimeters at the site show a highly seasonal pattern of percolate and exhibit variability due to both installation factors and hydraulic property heterogeneity. Individual event analysis of well hydrograph data reveals the primary influences on water-table response, namely rainfall depth, rainfall intensity, and initial water-table depth. Spatial and seasonal variability in well response is also evident. A new approach for calculating recharge from continuous water-table elevation records using a master recession curve (MRC) is demonstrated. The recharge estimated by the MRC approach when assuming a constant specific yield is seasonal to a lesser degree than the recharge estimate resulting from the lysimeter analysis. Partial reconciliation of the two recharge estimates is achieved by considering a conceptual model of flow processes in the highly-heterogeneous underlying fractured porous medium.     

Stable isotope constraints on the origin of the Cabo de Creus garnet-tourmaline pegmatites,Massif des Alberes,Eastern Pyrenees,Spain

Pegmatite dyke swarms are exposed within the easternmost Pyrenees at Cabo de Creus. These dykes were emplaced into high-grade metamorphosed sedimentary strata of Cambro-Ordovician age, but lack obvious field relationship to Hercynian intrusive rocks. Together with structural and geochemical data, equilibrium oxygen isotope fractionations at temperatures of ≈ 600°C, the lack of obvious subsolidus exchange, and the H- and O-isotopic signatures of water in equilibrium with pegmatite mica and quartz are interpreted to indicate a derivation from anatexis of a metapelitic source at shallow crustal levels.     

Further testing of the Integrated Hydrology Model (InHM): event‐based simulations for a small rangeland catchment located near Chickasha,Oklahoma

In the paper that is the foundation for this study, VanderKwaak and Loague (2001. Water Resources Research 37 : 999–1013) reported a demonstration of a fully coupled comprehensive physics‐based hydrologic‐response model, InHM (Integrated Hydrology Model), for two rainfall‐runoff events from the small rangeland catchment known as R‐5. The InHM simulations reported herein address (in three phases) limitations in the VanderKwaak and Loague (2001. Water Resources Research 37 : 999–1013) simulations. In Phase I, a new finite‐element mesh was selected to represent R‐5. In Phase II, with the new mesh in place, evaporation was considered for the R‐5 events. In Phase III, with the new mesh in place and evaporation considered, the geology of R‐5 was approximated. Each phase, compared with the results reported by VanderKwaak and Loague (2001. Water Resources Research 37 : 999–1013), shows a change in the simulated near‐surface response. The performance of InHM for 15 R‐5 events is also reported herein. The results from two stages of model calibration are presented. The uncertainty in initial soil‐water content estimates for event‐based simulation is shown to be a major limitation for physics‐based models. The performance of InHM, relative to past event‐based simulation efforts with a quasi‐physically based rainfall‐runoff model, is better for both peak stormflow and the time to peak stormflow, but worse for stormflow depth. The InHM simulations reported here set the stage for continuous simulation of near‐surface response for the R‐5 catchment with InHM. Copyright © 2004 John Wiley & Sons, Ltd.