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Summary Recycling spent lithium-ion batteries plays a significant role in alleviating the shortage of raw materials and environmental problems. However, recycled materials are deemed inferior to commercial materials, preventing the industry from adopting recycled materials in new batteries. Here, we demonstrate that the recycled LiNi1/3Mn1/3Co1/3O2 has a superior rate and cycle performance, verified by various industry-level tests. Specifically, 1 Ah cells with the recycled LiNi1/3Mn1/3Co1/3O2 have the best cycle life result reported for recycled materials and enable 4,200 cycles and 11,600 cycles at 80% and 70% capacity retention, which is 33% and 53% better than the state-of-the-art, commercial LiNi1/3Mn1/3Co1/3O2. Meanwhile, its rate performance is 88.6% better than commercial powders at 5C. From experimental and modeling results, the unique microstructure of recycled materials enables superior electrochemical performance. The recycled material outperforms commercially available equivalent, providing a green and sustainable solution for spent lithium-ion batteries.

Accelerated degradation tests can be used as the basis for predicting the performance or state of health of products and materials at use conditions over time. Measurements acquired at accelerated levels of stress are used to develop models that relate to the degradation of one or more performance measures. Frequently, products/materials of interest are subjected to variable stress levels during their lifetimes. However, testing is usually performed only at a few fixed stress levels. In such cases, cumulative degradation models are developed and assessed by using data acquired under those fixed stress conditions. The degradation rate at any stress condition within the range of the model can be estimated by the derivative of the cumulative model at that stress condition. It follows that, to predict cumulative degradation over variable use conditions, one might integrate the fluctuating degradation rate over time. Existing approaches for doing this consider degradation rates that depend only on the current stress level. Here, we propose to allow the degradation rate to also depend on the current state of health as indicated by the associated performance measure(s). The resulting modeling approach is capable of portraying a broader range of degradation behavior than existing approaches. The assertion of memoryless degradation by using this or any other approach should be assessed experimentally with data acquired under variable stress in order to increase confidence that the integrated rate model is accurate. In this article, we demonstrate the additional capability of the proposed approach by developing empirical memoryless rate-based degradation models to predict resistance increase and capacity decrease in lithium-ion cells that are being evaluated for use in electric vehicles. We then assess the plausibility of these models.

The battery technology literature is reviewed, with an emphasis on key elements that limit extreme fast charging. Key gaps in existing elements of the technology are presented as well as developmental needs. Among these needs are advanced models and methods to detect and prevent lithium plating; new positive-electrode materials which are less prone to stress-induced failure; better electrode designs to accommodate very rapid diffusion in and out of the electrode; measure temperature distributions during fast charge to enable/validate models; and develop thermal management and pack designs to accommodate the higher operating voltage.

While LiNixMnyCo1−x−yO2 (NMC) is one of the most widely used cathode materials for lithium-ion batteries (LIBs), the composition of NMC is evolving to Ni-rich NMC to achieve higher lithium capacity that fulfills the constant demand for LIBs with ever-higher energy densities. The change in the composition of NMC affects electrochemical features and electrode cross-talk, which explains the performance change during cycling. In this study, we introduce various NMC materials (LiNi0.5Mn0.3Co0.2O2, LiNi0.6Mn0.2Co0.2O2 and LiNi0.8Mn0.1Co0.1O2) to reveal how the NMC composition affects electrode cross-talk. The study reveals that NMC composition strongly affects transition metal dissolution; dissolution of manganese linearly decreases as its stoichiometric ratio in NMC decreases, while dissolution of nickel is only prominent in LiNi0.8Mn0.1Co0.1O2. Aged electrolyte samples are characterized with high-performance liquid chromatography, and two electrolyte decomposition species, C8H16O5 and C9H18O5, are identified across all samples.

Two testing protocols, QC/T 743 and those used by the U.S. Advanced Battery Consortium (USABC), were compared using cells based on LiFePO 4 /graphite chemistry. Differences in the protocols directly affected the data and the performance decline mechanisms deduced from the data. In all cases, the rate of capacity fade was linear with time. Overall, the testing protocols produced very similar data when the testing conditions and metrics used to define performance were similar. The choice of depth of discharge and pulse width had a direct effect on the apparent rate of resistance increased and estimated cell life. At greater percent depth of discharge (%DOD) and pulse width, the estimated life was shorter that at lower %DOD and shorter pulse width. This indicates that cells which were at the end of life based on the USABC protocol were not at end of life based on the QC/T 743 protocol by a large margin.

An extensive precipitation database has been developed over the past 35 years with the first records starting in January 1962 and going through September 1996 from the Reynolds Creek Experimental Watershed located near the north end of the Owyhee Mountains in southwest Idaho. Precipitation ranges from 236 mm on the lowest elevations at the north end of the watershed to 1123 mm at the southwest corner of the watershed. There are continuous 35 year records available for 12 sites, 20–32 year records available for 8 sites, 10–19 year records available for 25 sites, and 4–9 year records for 8 sites for a total of 53 sites. All of these data have been stored as breakpoint and hourly records in the U.S. Department of Agriculture, Agricultural Research Service, Northwest Watershed Research Center database. These breakpoint and hourly data are available from the anonymous ftp site: ftp.nwrc.ars.usda.gov.

Recent upgrades to the MODTRAN atmospheric radiation code improve the accuracy of its radiance predictions, especially in the presence of clouds and thick aerosols, and for multiple scattering in regions of strong molecular line absorption. The current public-released version of MODTRAN (MODTRAN3.7) features a generalized specification of cloud properties, while the current research version of MODTRAN (MODTRAN4) implements a correlated-k (CK) approach for more accurate calculation of multiply scattered radiance. Comparisons to cloud measurements demonstrate the viability of the CK approach. The impact of these upgrades on predictions for AVIRIS viewing scenarios is discussed for both clear and clouded skies; the CK approach provides refined predictions for AVIRIS nadir and near-nadir viewing.

A new computer model, SHARC, has been developed by the Air Force for calculating high-altitude atmospheric IR radiance and transmittance spectra with a resolution of better than 1/cm. Comprehensive coverage of the 2 to 40 microns (250/cm to 5,000/cm) wavelength region is provided for arbitrary lines of sight in the 50-300 km altitude regime. SHARC accounts for the deviation from local thermodynamic equilibrium (LTE) in vibrational state populations by explicitly modeling the detailed production, loss, and energy transfer process among the important molecular vibrational states. The calculated vibrational populations are found to be similar to those obtained from other non-LTE codes. The radiation transport algorithm is based on a single-line equivalent width approximation along with a statistical correction for line overlap. This approach is reasonably accurate for most applications and is roughly two orders of magnitude faster than the traditional LBL methods which explicitly integrate over individual line shapes. In addition to quiescent atmospheric processes, this model calculates the auroral production and excitation of CO2, NO, and NO(+) in localized regions of the atmosphere. Illustrative comparisons of SHARC predictions to other models and to data from the CIRRIS, SPIRE and FWI field experiments are presented. Non-local thermodynamic equilibrium, Infrared radiation, Computer code, Vibrational and rotational levels, Limb radiance.

A new very narrow band model (VNBM) approach has been developed and incorporated into the MODTRAN atmospheric transmittance–radiance code. The VNBM includes a computational spectral resolution of 1 cm−1, a single-line Voigt equivalent width formalism that is based on the Rodgers–Williams approximation and accounts for the finite spectral width of the interval, explicit consideration of line tails, a statistical line overlap correction, a new sublayer integration approach that treats the effect of the sublayer temperature gradient on the path radiance, and the Curtis–Godson (CG) approximation for inhomogeneous paths. A modified procedure for determining the line density parameter 1/d is introduced, which reduces its magnitude. This results in a partial correction of the VNBM tendency to overestimate the interval equivalent widths. The standard two parameter CG approximation is used for H2O and CO2, while the Goody three parameter CG approximation is used for O3. Atmospheric flux and cooling rate p...

Lithium-ion batteries are rapidly being adopted for transportation applications, ranging from hybrid- to full-electric vehicles. To assure that the automotive battery can meet the demands of these applications, the US Advanced Battery Consortium has established test manuals and performance targets for each application [1-3]. These manuals use accelerated tests to gather needed performance degradation information in a limited amount of time. Models are then developed from these data that relate performance decline to the magnitude and duration of the stress. Isothermal aging stresses the battery under a simple set of conditions and can be used to elucidate the underlying degradation mechanisms. It is then generally assumed that a cumulative degradation model of aging under non-isothermal conditions would be a linear combination of the isothermal results. However, this approach may not directly predict the non-isothermal behavior. A model based on degradation rates may be a better predictor. In theory, integrating the rate-based model over the temperature path can then express the cumulative degradation. The results of this investigation will be discussed. The work at Argonne National Laboratory was performed under the auspices of the U.S Department of Energy (DOE), Office of Vehicle Technologies, under Contract No. DE-AC02-06CH11357. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000. The efforts at Idaho National Laboratory and at Lawrence Berkeley National Laboratory were performed under Contract Numbers DE-AC07-05ID14517 and DE-AC03-76SF00098, respectively. This article issue has been created by UChicago Argonne, LLC, Operator of Argonne National Laboratory (Argonne). Argonne, a DOE Office of Science Laboratory, is operated under Contract No. DE-AC02-06CH11357. The U.S. Government retains for itself, and others acting on its behalf, a paid-up, nonexclusive, irrevocable, worldwide license in said article to reproduce, prepare derivative works, distribute copies to the public, and perform publicly and display publicly, by or on behalf of the Government. References FreedomCAR Battery Test Manual for Power-Assist Hybrid Electric Vehicles, DOE/ID-11069, October 2003. Battery Test Manual for Plug-In Hybrid Electric Vehicles, Rev. 3, INL/EXT-14-32849, September 2014. Battery Test Manual for Electric Vehicles, INL/EXT-15-34184, Rev. 3, June 2015

Clouds and cloud fields introduce important backscattering, obscuration, shadowing and radiative trapping effects in visible-NIR(near-infrared)-SWIR(short-wavelength infrared) hyperspectral imagery of the ground, especially in off-nadir (slant) viewing geometries where cloud thickness effects reduce the cloud-free line of sight (CFLOS). An investigation of these effects was conducted using monochromatic, multispectral and hyperspectral scene simulations performed with the Spectral Sciences, Inc. MCScene Monte Carlo code. Cloud fields were obtained from the Cloud Scene Simulation Model (CSSM) of Cianciolo and Raffensberger. The simulations took advantage of a data-fusion-based noise-removal method that enabled a dramatic reduction in computation time. Illumination levels at the sunlit ground showed enhancements of up to ~50% due to cloud scattering. Illumination in the cloud shadows was 20% of the full solar illumination or greater, with cloud optical depths of up to 10. Most of this illumination arises from solar scattering off the cloud tops and sides; however, a significant part can be ascribed to radiative trapping between the ground and the clouds, as represented by a local atmospheric spherical albedo. A simulation of a hyperspectral scene with cloud shadows was found to reproduce shadowing effects found in real data. Deeper shadowing is observed with increasing wavelength and in water-band regions, consistent with a previous analysis of cloud shadows in real imagery. The MCScene calculations also predict shadow enhancements of column water vapor retrievals from atmospheric correction/compensation codes, also in accord with field observations. CFLOS fractions were calculated as a function of off-nadir viewing angle and were found to be very accurately represented by a semi-empirical analytical function of both angle and cloud cover.

Many communities have implemented systems of care in an effort to better coordinate and integrate mental health and other social services for children and youths, while simultaneously managing existing funding sources more effectively. Systems of care represent a fundamentally different way of delivering mental health services and accordingly require new approaches for both developing and sustaining collaboration. This article examines obstacles to collaboration and addresses key factors required to build and sustain collaboration.

The Moderate Spectral Atmospheric Radiance and Transfer (MOSART) computer program calculates atmospheric transmission and radiation in the ultraviolet region through the microwave spectral regions (0.2 microns to infinity or 0 - 50,000 cm per sec. The spectral resolution is variable from a value of 2 cm per sec. upward in increments of 1 cm per sec. It contains features which have been extracted from the MODTRAN code developed by the Geophysics Division (PL/GPOS) of the Air Force Phillips Laboratory and the APART code developed by Photon Research Associates (PRA). Because of the requirement that MOSART be compatible with various codes used in the SSGM (Strategic Scene Generation Model), the overall structure of this version of MOSART closely follows that of APART. However, MOSART contains all the MODTRAN atmospheric features and is easily used for that code's usual point-to-point calculations. This volume provides the user with information describing the installation of MOSART. The other volumes describe running the code (Vol. II), technical discussion (Vol. III), and the structure of MOSART (Vol. IV). To provide users with on-line assistance, this volume is available in a series of 'html' files that can be viewed using the MOSART Input Builder or the MOSAIC Software. (AN)

MODTRAN2' is the most recent version of MODTRAJP, the Moderate Resolution Atmospheric Radiance and Transmittance Model, officially released by the Geophysics Directorate, Phillips Laboratory, in early 1993. It encompasses all the capabilities of LOWTRAN 73, the historic 20 cni' resolution (full width at half maximum, FWHM) radiance code, but incorporates a much more sensitive molecular band model with 2 ciii' resolution. The band model is based directly upon the HITRAN4 spectral parameters, including both temperature and pressure (line shape) dependencies. Because the band model parameters and their applications to transmittance calculations have been independently developed using equivalent width "binning" procedures, validation against full Voigtline-by-line calculations (eg. FASCODEb) is important. Extensive spectral comparisons have shown excellent agreement. In addition, simple timing runs of MODTRAN vs. FASCOD3P (released in 1992) show an improvement of more than a factor of 100 for a typical 500 cm spectral interval and comparable vertical layering. It has been previously established that not only is MODTRAN an excellent band model for "full path" calculations (that is, radiance and/or transmittance from point A to point B), but it replicates layer-specific quantities to a very high degree of accuracy6. Such layer quantities, derived from ratios and differences of longer path MODTRAN calculations from point A to adjacent layer boundaries, can be used to provide inversion algorithm weighting functions or similarly formulated quantities. One of the most exciting new applications is the rapid calculation of reliable IR cooling rates7, including species, altitude, and spectral distinctions, as well as the standard integrated quantities. Comparisons with prior line-by-line cooling rate calculations'9 are excellent, and the techniques can be extended to incorporate global climatoIogies°.

This paper describes the development of a new version of the SHARC code, SHARC-3, which includes the ability to simulate changing atmospheric conditions along the line-of-sight (LOS) paths being calculated. SHARC has been developed by the U.S. Air Force for the rapid and accurate calculation of upper atmospheric IR radiance and transmittance spectra with a resolution of better than 1 cm-1 in the 2 to 40 micrometers (250 to 5,000 cm-1) wavelength region for arbitrary LOSs in the 50 - 300 km altitude regime. SHARC accounts for the production, loss, and energy transfer processes among the molecular vibrational states important to this spectral region. Auroral production and excitation of CO2, NO, and NO+ are included in addition to quiescent atmospheric processes. Calculated vibrational temperatures are found to be similar to results from other non-LTE codes, and SHARC's equivalent-width spectral algorithm provides very good agreement with much more time-consuming `exact' line-by-line methods. Calculations and data comparisons illustrating the features of SHARC-3 are presented.

This paper presents a methodology for the development of software for classifying power system disturbances by type from the transient waveform signature. The implementation of classification capability in future transient recorders will enable such features as selective storage of transient data (to better utilize limited storage media) and automated reporting of disturbances to central control facilities. The wavelet transform provides an effective and efficient means of decomposing voltage and current signals of power system transients to detectable and discriminant features. Similarities of power system transients to wide-band signals in other domains, the simultaneous presence of a resonant frequency, its harmonics, and impulse (high-frequency, time-localized) components, make this technique extendible to other classification systems. The classification algorithm uses statistical pattern recognition on features derived from the extreme representation of the transient waveform after processing the transient waveform by a non-orthogonal, quadratic spline wavelet. Training and classification testing use simulated waveforms of a 200 mile, three-phase transmission line produced by the Electromagnetic Transients Program (EMTP). A simple Bayesian classifier identifies an unknown transient waveform as a capacitor switching or fault transient, and locates the point of disturbance from one of two possible locations on the transmission line. Due to the effectiveness of the wavelet transform preprocessing, the classification system currently performs at 100 percent accuracy on four transient classes.© (1994) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

MODTRAN2 (1992) is the most recent version of MODTRAN, the Moderate Resolution Atmospheric Radiance and Transmittance Model, first released by the Geophysics Directorate, Phillips Laboratory, in 1990. It encompasses all the capabilities of LOWTRAN 7, the historic 20 cm-1 resolution radiance code, but incorporates a much more sensitive molecular band model with 2 cm-1 resolution. For inversion algorithm applications, MODTRAN2 must prove to be sufficiently accurate when calculating layer- specific perturbations. First steps in establishing this capability have recently been accomplished. DREV (Defence Research Establishment Valcartier, Canada), in conjunction with the Geophysics Directorate, has taken measurements with a surface-based Bomem interferometer (approximately 1 cm-1 resolution), with full supporting sonde profiles (z, T, p, and relative humidity). This suggests that the derivative matrices, typically required for inversion algorithms, may be readily (and rapidly) calculated using MODTRAN whenever its spectral resolution is adequate.© (1993) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Computer-Aided Design (CAD) systems can and should support and enhance the product development process. Unfortunately, the benefits delivered by current systems have not met users’ expectations. We believe that CAD systems should be designed to minimize the cognitive complexity facing the engineer; CAD systems should be easy to use and should help the engineer manage design-related complexity. A series of propositions are developed which refine these ideas. To evaluate the central propositions, we constructed a prototype CAD system for the design of blanked and bent sheet metal parts. The user of the system is provided with a hand-held input device which interprets actions of the user’s hands as production operations on a CAD representation of the part. The user creates sheet metal parts by bending, stretching, pushing, and moving the input device. The system was demonstrated to engineers, engineering managers, and researchers, who provided ideas for future enhancements. Reactions to the demonstrations of the system have helped evaluate the concepts behind the system. Although we have used sheet metal as an example domain, we believe these ideas can be applied in other design contexts.

High resolution band-model parameters are presented for the 4.3 μm CO 2 band from 200 to 3000°K. Comparisons are made to experimental data covering this same temperature range. The band model predictions and data are shown to be in good agreement. Application of the band model parameters to plume emission and atmospheric absorption calculations in the CO 2 fundamental band head region (2380–2400 cm -1 ) is discussed. Line-by-line and band-model plume signature predictions are compared for an aircraft and a rocket plume over 0, 0.5, and 5 km atmospheric paths. The line-by-line and band-model predictions for the 0 and 0.5 km paths are in good agreement. For the 5 km path, the band-model overestimates the atmospheric transmission by a factor of two. The reason for this overprediction is discussed and a correction is presented which improves the accuracy of the band-model transmission calculations.

We present an analysis of four meson charge-exchange reactions (${\ensuremath{\pi}}^{\ensuremath{-}}p\ensuremath{\rightarrow}{\ensuremath{\pi}}^{0}n,{\ensuremath{\pi}}^{\ensuremath{-}}p\ensuremath{\rightarrow}{\ensuremath{\eta}}^{0}n,{K}^{\ensuremath{-}}p\ensuremath{\rightarrow}{\overline{K}}^{0}n, \mathrm{and} {K}^{+}n\ensuremath{\rightarrow}{K}^{0}p$) within the context of our Regge-pole-cut model based on the Durand-Van Hove model. Quite good fits to all differential cross sections and polarizations are obtained. Predictions for the $\mathrm{KN}$ charge-exchange polarizations are also presented.

The one-particle distribution function in the wee-$x$ region is derived in the diffractive-excitation model. The result describes very well the "isotropy" and "Bose-Einstein" distribution of the 11.8-GeV/c ${K}^{+}p$ data on inclusive reactions in that region. There is no need for the postulation of "blackbody radiation." It is shown that the phenomenon should disappear at asymptotic energies.

Gage catch from two standard weighing recording rain gages (Belfort model 5-780), one with a modified Alter windshield and one with a rigid Alter type windshield, were compared for 89 storms with wind speeds ranging from 4 to 32 mph (6.4 to 51.5 km/h) and temperatures ranging from 14° to 69°F (−10° to 21°C). The differences between gage catches were statistically significant at the 1% level for wind speeds of 12 to 16 mph (19.3 to 25.7 km/h) and for temperatures of 23°F (−5°C) or less. Since on the average the windshields do not produce significantly different catches, either windshield can be used to compute actual precipitation by using the Hamon dual gage approach.

The methodology for calculating aircraft infrared radiation is developed by expressing the signature in its component parts and then modeling each in terms of a few parameters. The basic signature components are: exhaust plume molecular emissions, airframe thermal emissions, various exposed engine hot parts, and scattered ambient radiation (e.g., earth-shine, sunshine and skyshine). When calculating sensor irradiances for systems studies, the close relationship between the aircraft signature and environmental conditions must be considered. This is illustrated with scene contrast signature calculations for several different observer viewing angles and background types.

The development and evaluation of algorithms to detect targets against cloud backgrounds requires a comprehensive understanding of the clutter properties such as the radiance distributions, textures, edge effects, etc. A number of measurement programs are collecting data for this purpose. However they are limited by the vast amounts of data required, and their limited resources for obtaining the data. This paper will describe and show results from a first principles infrared cloud scene radiance model. The work is sponsored by the Naval Surface Warfare Center (NSWC) through a Small Business Innovative Research Program (SBIR) to support IRAMMP (Infrared Analysis Modeling and Measurement Program -- formerly BMAP) as part of the Navy's Infrared Search and Track effort. The model is designed to handle arbitrary viewing geometries, atmospheric conditions, and sensor parameters. The output is a two dimensional (n x m pixels) scene radiance map which can be used by system designers, data takers, and analysts.

Clouds are an important source of variations in the IR background radiation was detected by satellite surveillance systems, because clouds absorb and scatter solar radiation and have a blackbody temperature different from that of the earth's surface. In the present study, a model which describes the scattering, absorption, and emission of radiation by atmospheric water or ice clouds is synthesized from previous works on the scattering of solar radiation. The cloud model is combined with the LOWTRAN atmospheric transmission model and is used to predict the apparent spectral radiance from scenes containing clouds as detected by a downward-looking observer. The effects of solar scatter, thermal emission, transmitted upwelling radiation, and atmospheric attenuation are included. Calculations using the model have been compared with infrared cloud data from several sources, including radiometer data from the BAMM (balloon Altitude Mosaic Measurements) Program. These analyses suggest that low altitude cumulus clouds are not an important source of background signal variations in the 2.7-3.1 micrometer region. The BAMM data and model calculations indicate that high altitude cirrus clouds can cause large spatial variations in the background signal in this wavelength region, due to enhanced solar scatter in the wings of the water vapor absorption bands.

Modifications to the atmospheric transmission and radiation code LOWTRAN5 are presented which include (1) an increase in the spectral resolution from 20 to 5 cm(-1), (2) the addition of temperature-dependent molecular absorption coefficients, (3) the use of a multiparameter Doppler-Lorentz band model for calculation of molecular transmittance, and (4) the use of the Curtis-Godson approximation for multilayered paths. Comparisons of predictions using the LOWTRAN5 5-cm(-1) band model option to measured transmittance and radiance data are also presented.

High resolution measurements of atmospheric transmission of sunlight from space to altitudes of 12.2 km, 8.53 km, and 5.48 km made over Johnston Island are reported. The spectral region covered is 4.0-5.3 microm. Comparisons of the measured transmission with theoretically synthesized transmission curves are presented. It is shown that the sharp spectral features due to molecular line-by-line absorption can be predicted accurately while the modeling of the continuum absorption features needs further development. A discussion of the current models for CO(2) and N(2) continuum absorption is presented. An alternative mechanism is proposed for continuum absorption, which is based on the spectral properties of atmospheric van der Waals molecular complexes such as CO(2).N(2) and N(2).N(2) dimers.

The soil profile is an important water storage reservoir within the hydrologic cycle. An understanding of the factors affecting daily soil water status is necessary to increase or modify vegetation or water yields. Many mathematical simulation models have been developed to assess soil water status, but none were found that were specifically developed for use on Western rangelands. The purpose of this report was to test soil water models that appeared to be sufftciently general for adaption to rangeland conditions, to determine if they could provide adequate results, and the level of sophistication required. The 2 models selected for evaluation were the Ekalaka Rangeland Hydrology and Yield Model (ERHYM) developed for use during the growing season on grasslands of the northern Great Phtms,and the Soil-Plant-Air-Water model (SPAW), which was developed for use with cultivated crops in the Midwest. Results indicated that both models could be adapted to produce adequate soil water information under rangeland conditions of southwestern Idaho. Overall, the somewhat simpler ERHYM model produced results more closely aligned to observed values than did SPAW. The lack of a snow accumulation and melt routine in SPAW (which could be added) appeared to be the main source of observed differences. These differences were a function of timing rather than a difference in total soil water at the end of each year, where results for the 2 models were very similar. The soil profile is one of the most important water storage reservoirs within the hydrologic cycle. In arid regions, available soil water seldom exists for more than a few months at a time, because it is rapidly extracted by plant transpiration and soil evaporation. Therefore, very little water ever percolates below plant rooting depth. In more humid regions, the magnitude of infiltrated water may be more than adequate for plant needs, and excess water may percolate into ground water reservoirs. An understanding of the factors affecting the day-today soil water status is important when attempting to increase or modify vegetation or water yields. The time distribution of soil water within the root zone is a complex interaction of many variables related to present and historical climate, plants, and parent soil materials. Hildreth ( 1976,1978) indicated that many mathematical simulations or computer models have been developed to assess soil water status. However, most of these models were developed to satisfy a particular need (i.e., spring wheat yield predictions in the northern Great Plains)and may not represent other crops or locations. None of the models were specifically developed for use on Western rangelands. The objective of this study was to determine if existing models with soil water accounting procedures included, representing different levels of complexity and data requirements, could be adapted to particular Western rangeland conditions. Two models were selected for evaluation based on the following criteria: (1) models appeared to be general enough to be adaptable to range conditions; (2) models had been tested against field data (even though for cultivated crops); and (3) documentation was readily available. The models selected were the ERHYM (Ekalaka Rangeland Hydrology and Yield Model) developed by Wight and Neff Authors are hydrologist and hydrologic technician. respectively. Northwest Watershed Research Center, USDA-ARS. 270 South Orchard, Boise, Ida. 83705. Manuscript accepted February 29, 1984. JOURNAL OF RANGE MANAGEMENT 37(6), November 1984 Table 1. Input requirements for running SPAW and ERHYM soil water balance models. SPAW Model ERHYM Model Initial soil water (or default option) Daily precipitation Daily runoff or SCS curve number Daily pan evaporation Monthly pan coefficient Avg. annual pan evaporation Layer thickness A time interval A soil pressure for tolerance parameter Soil water evaporation parameter Soil freezing dates Root distribution Canopy cover curve Canopy susceptibility to water stress Phenology curve Phenology susceptibility to water stress Moisture-stress curves (as provided) Planting & harvest dates Initial soil water Daily precipitation SCS curve number Daily max & min temperature Daily solar radiation