Simulated Mass Balance Research Articles

An economic evaluation of biological conversion of wheat straw to butanol: A biofuel

A cost estimation study was performed for a biological butanol production plant with a capacity of 150×106kg butanol/year. Wheat straw (WS) was used as a feedstock. In addition to butanol, acetone (78.05×106kg/year) and ethanol (28.54×106kg/year) would also be produced. The total capital cost for this plant was $193.07×106. This exercise was based in part on data generated in our laboratory and in part on data obtained from literature. The design, mass balance, and energy balance simulations were performed using SuperPro Designer (Version 8.5003, 2012). For butanol production wheat straw would be pretreated with dilute (1% v/v) sulfuric acid at 121°C for 1h followed by separate hydrolysis (using enzymes), fermentation and recovery. Enzyme cost for wheat straw hydrolysis was adapted from literature ($0.16/kg butanol). Utilities which included steam/high pressure steam, cooling/chilling water, and electricity represented the major cost of the operation (49.18%) followed by raw materials (26.81%). Based on batch fermentation of wheat straw hydrolysate and distillative recovery of acetone butanol ethanol (ABE), butanol production cost was estimated to be $1.30/kg for a grass-rooted/green-field plant. Application of a membrane recovery process could reduce this price to $1.00/kg for a plant annexed to an existing distillery.

Assessment of Groundwater Quality Based on Matter Element Extension Model

The basic theory and calculating processes of matter element extension method are discussed in detail. Mass balance simulation is used to study the changes of groundwater chemistry. Results show that calcite and dolomite are oversaturated, while gypsum, fluorite, and halite are unsaturated in the simulation path; so calcite precipitates, while gypsum, fluorite, halite, and dolomite dissolve. The changing tendency of Ca2+/Na+ is apparent. Because of the dissolution and precipitation of minerals, the content of each ion changes. Parameters of groundwater are basically within the permissible limits and meet the requirement of drinking water standards. By comparing the evaluation results obtained from matter element extension method, osculating value method based on entropy weight, and principal component analysis method, it is proved that matter element extension is an effective and reasonable method for groundwater quality assessment. The converting tendency of groundwater quality is judged based on the extension indexes; this characteristic is unique of matter element extension method.

Verification of model simulated mass balance, flow fields and tabular calving events of the Antarctic ice sheet against remotely sensed observations

The Antarctic ice sheet (AIS) has the greatest potential for global sea level rise. This study simulates AIS ice creeping, sliding, tabular calving, and estimates the total mass balances, using a recently developed, advanced ice dynamics model, known as SEGMENT-Ice. SEGMENT-Ice is written in a spherical Earth coordinate system. Because the AIS contains the South Pole, a projection transfer is performed to displace the pole outside of the simulation domain. The AIS also has complex ice-water-granular material-bedrock configurations, requiring sophisticated lateral and basal boundary conditions. Because of the prevalence of ice shelves, a ‘girder yield’ type calving scheme is activated. The simulations of present surface ice flow velocities compare favorably with InSAR measurements, for various ice-water-bedrock configurations. The estimated ice mass loss rate during 2003–2009 agrees with GRACE measurements and provides more spatial details not represented by the latter. The model estimated calving frequencies of the peripheral ice shelves from 1996 (roughly when the 5-km digital elevation and thickness data for the shelves were collected) to 2009 compare well with archived scatterometer images. SEGMENT-Ice’s unique, non-local systematic calving scheme is found to be relevant for tabular calving. However, the exact timing of calving and of iceberg sizes cannot be simulated accurately at present. A projection of the future mass change of the AIS is made, with SEGMENT-Ice forced by atmospheric conditions from three different coupled general circulation models. The entire AIS is estimated to be losing mass steadily at a rate of ~120 km3/a at present and this rate possibly may double by year 2100.

Simulating melt, runoff and refreezing on Nordenskiöldbreen, Svalbard, using a coupled snow and energy balance model

Abstract. A distributed energy balance model is coupled to a multi-layer snow model in order to study the mass balance evolution and the impact of refreezing on the mass budget of Nordenskiöldbreen, Svalbard. The model is forced with output from the regional climate model RACMO and meteorological data from Svalbard Airport. Extensive calibration and initialisation are performed to increase the model accuracy. For the period 1989–2010, we find a mean net mass balance of −0.39 m w.e. a−1. Refreezing contributes on average 0.27 m w.e. a−1 to the mass budget and is most pronounced in the accumulation zone. The simulated mass balance, radiative fluxes and subsurface profiles are validated against observations and are generally in good agreement. Climate sensitivity experiments reveal a non-linear, seasonally dependent response of the mass balance, refreezing and runoff to changes in temperature and precipitation. It is shown that including seasonality in climate change, with less pronounced summer warming, reduces the sensitivity of the mass balance and equilibrium line altitude (ELA) estimates in a future climate. The amount of refreezing is shown to be rather insensitive to changes in climate.

Impact of model resolution on simulated wind, drifting snow and surface mass balance in Terre Adélie, East Antarctica

AbstractThis paper presents the impact of model resolution on the simulated wind speed, drifting snow climate and surface mass balance (SMB) of Terre Adélie and its surroundings, East Antarctica. We compare regional climate model simulations at 27 and 5.5 km resolution for the year 2009. The wind speed maxima in Terre Adélie and the narrow glacial valleys of Victoria Land are better represented at 5.5 km resolution, because the topography is better resolved. Drifting snow sublimation is >100 mm a-1 in regions with high wind speeds. Our results indicate a strong feedback between topography, wind gradients and drifting snow erosion. As a result, SMB shows much more local spatial variability at 5.5 km resolution that is controlled by drifting snow erosion, whereas the large-scale SMB gradient is largely determined by precipitation. Drifting snow processes lead to ablation in the narrow glacial valleys of Victoria Land. The integrated SMB equals 86 Gt. Although wind climate, drifting snow processes and SMB variability are better represented at 5.5 km, the area-integrated SMB is not significantly different between the simulations at 27 and 5.5 km. A horizontal resolution of 27 km is sufficient to realistically simulate ice-sheet wide SMB.

The value of glacier mass balance, satellite snow cover images, and hourly discharge for improving the performance of a physically based distributed hydrological model

Physically based hydrological models describe natural processes more accurately than conceptual models but require extensive data sets to produce accurate results. To identify the value of different data sets for improving the performance of the distributed hydrological model TOPKAPI we combine a multivariable validation technique with Monte Carlo simulations. The study is carried out in the snow and ice‐dominated Rhonegletscher basin, as these types of mountainous basins are generally the most critical with respect to data availability and sensitivity to climate fluctuations. Each observational data set is used individually and in combination with the other data sets to determine a subset of best parameter combinations out of 10,000 Monte Carlos runs performed with randomly generated parameter sets. We validate model results against discharge, glacier mass balance, and satellite snow cover images for a 14 year time period (1994–2007). While the use of all data sets combined provides the best overall model performance (defined by the concurrent best agreement of simulated discharge, snow cover and mass balance with their respective measurements), the use of one or two variables for constraining the model results in poorer performance. Using only one data set for constraining the model glacier mass balance proved to be the most efficient observation leading to the best overall model performance. Our main result is that a combination of discharge and satellite snow cover images is best for improving model performance, since the volumetric information of discharge data and the spatial information of snow cover images are complementary.

Selection of Prediction Methods for Thermophysical Properties for Process Modeling and Product Design of Biodiesel Manufacturing

To optimize biodiesel manufacturing, many reported studies have built simulation models to quantify the relationship between operating conditions and process performance. For mass and energy balance simulations, it is essential to know the four fundamental thermophysical properties of the feed oil: liquid density (ρL), vapor pressure (Pvap), liquid heat capacity (CPL), and heat of vaporization (ΔHvap). Additionally, to characterize the fuel qualities, it is critical to develop quantitative correlations to predict three biodiesel properties, namely, viscosity, cetane number, and flash point. Also, to ensure the operability of biodiesel in cold weather, one needs to quantitatively predict three low-temperature flow properties: cloud point (CP), pour point (PP), and cold filter plugging point (CFPP). This article presents the results from a comprehensive evaluation of the methods for predicting these four essential feed oil properties and six key biodiesel fuel properties. We compare the predictions to reported experimental data and recommend the appropriate prediction methods for each property based on accuracy, consistency, and generality. Of particular significance are (1) our presentation of simple and accurate methods for predicting the six key fuel properties based on the number of carbon atoms and the number of double bonds or the composition of total unsaturated fatty acid methyl esters (FAMEs) and (2) our posting of the Excel spreadsheets for implementing all of the evaluated accurate prediction methods on our group Web site (www.design.che.vt.edu) for the reader to download without charge.

Possibilistic uncertainty analysis of a conceptual model of snowmelt runoff

Abstract. This study presents the analysis of predictive uncertainty of a conceptual type snowmelt runoff model. The method applied uses possibilistic rather than probabilistic calculus for the evaluation of predictive uncertainty. Possibility theory is an information theory meant to model uncertainties caused by imprecise or incomplete knowledge about a real system rather than by randomness. A snow dominated catchment in the Chilean Andes is used as case study. Predictive uncertainty arising from parameter uncertainties of the watershed model is assessed. Model performance is evaluated according to several criteria, in order to define the possibility distribution of the parameter vector. The plausibility of the simulated glacier mass balance and snow cover are used for further constraining the model representations. Possibility distributions of the discharge estimates and prediction uncertainty bounds are subsequently derived. The results of the study indicate that the use of additional information allows a reduction of predictive uncertainty. In particular, the assessment of the simulated glacier mass balance and snow cover helps to reduce the width of the uncertainty bounds without a significant increment in the number of unbounded observations.

Runoff and mass-balance simulations from the Greenland Ice Sheet at Kangerlussuaq (Søndre Strømfjord) in a 30-year perspective, 1979–2008

Abstract. This study provides insights into surface mass-balance (SMB) and runoff exiting the Watson River drainage basin, Kangerlussuaq, West Greenland during a 30 year period (1978/1979–2007/2008) when the climate experienced increasing temperatures and precipitation. The 30-year simulations quantify the terrestrial freshwater output from part of the Greenland Ice Sheet (GrIS) and the land between the GrIS and the ocean, in the context of global warming and increasing GrIS surface melt. We used a snow-evolution modeling system (SnowModel) to simulate the winter accumulation and summer ablation processes, including runoff and SMB, of the ice sheet: indicating that the simulated equilibrium line altitude (ELA) was in accordance with independent observations. To a large extent, the SMB fluctuations could be explained by changes in net precipitation (precipitation minus evaporation and sublimation), with 8 out of 30 years having negative SMB, mainly because of relatively low annual net precipitation. The overall trend in net precipitation and runoff increased significantly, while SMB increased insignificantly throughout the simulation period, leading to enhanced precipitation of 0.59 km3 w.eq. (or ~60%), runoff of 0.43 km3 w.eq. (or ~55%), and SMB of 0.16 km3 w.eq. (or ~85%). Runoff rose on average from 0.80 km3 w.eq. in 1978/1979 to 1.23 km3 w.eq. in 2007/2008. The GrIS satellite-derived melt-extent increased significantly, and the melting intensification occurred simultaneously with the increase in local Kangerlussuaq runoff, indicating that satellite data can be used as a proxy (r2=0.64) for runoff from the Kangerlussuaq drainage area.

Modeling the surface mass balance of a high Arctic glacier using the ERA‐40 reanalysis

Investigating glacier mass balance via the use of numerical models provides an important insight into glacier‐climate interactions and allows for the assessment of future changes in sea level and local water resources. The application of mass balance models to unmonitored regions has previously been inhibited by the inadequate spatial coverage of local meteorological observations. One way to overcome this problem is through the use of climate reanalysis products. In this paper we evaluate the ability of the European Centre for Medium‐Range Forecasts ERA‐40 reanalysis to drive a surface mass balance model of Midre Lovénbreen, northwest Spitsbergen, Svalbard. The ERA‐40 reanalysis is validated and bias‐corrected against long‐term observations from two nearby in situ weather stations. The model is calibrated over the period of mass balance observations (1968–2001) using a downhill simplex parameter optimization technique to minimize the error between observed and simulated mass balances. The calibrated model is then used to extend the mass balance record of Midre Lovénbreen back to the beginning of the reanalysis in 1958. Overall, the ERA‐40 reanalysis is found to correspond sufficiently well with surface observations to be used for mass balance modeling. When driven using the ERA‐40 reanalysis, the calibrated surface mass balance model performs very well. The area‐averaged cumulative errors for winter, summer, and net balances are all very small over the period 1968–2001 (<0.3 m water equivalent (w.e.)). For the centerline stakes the correlation coefficients between observed and modeled net, winter, and summer balances are 0.83, 0.84, and 0.77, respectively. Using the hindcasted mass balances, a mean cumulative mass loss of −17.8 ± 3.7 m w.e. is estimated over the 44 year period 1958–2001.

Forcing a Distributed Glacier Mass Balance Model with the Regional Climate Model REMO. Part I: Climate Model Evaluation

Abstract A coupling interface between the regional climate model REMO and a distributed glacier mass balance model is presented in a series of two papers. The first part describes and evaluates the reanalysis-driven regional climate simulation that is used to force a mass balance model for two glaciers of the Swiss mass balance network. The detailed validation of near-surface air temperature, precipitation, and global radiation for the European Alps shows that the basic spatial and temporal patterns of all three parameters are reproduced by REMO. Compared to the Climatic Research Unit (CRU) dataset, the Alpine mean temperature is underestimated by 0.34°C. Annual precipitation shows a positive bias of 17% (30%) with respect to the uncorrected gridded ALP-IMP (CRU) dataset. A number of important and systematic model biases arise in high-elevation regions, namely, a negative temperature bias in winter, a bias of seasonal precipitation (positive or negative, depending on gridbox altitude and season), and an underestimation of springtime and overestimation of summertime global radiation. These can be expected to have a strong effect on the simulated glacier mass balance. It is recommended to account for these shortcomings by applying correction procedures before using the RCM output for subsequent mass balance modeling. Despite the obvious model deficiencies in high-elevation regions, the new interface broadens the scope of application of glacier mass balance models and will allow for a straightforward assessment of future climate change impacts.

The Influence of Air Temperature Inversions on Snowmelt and Glacier Mass Balance Simulations, Ammassalik Island, Southeast Greenland

Abstract In many applications, a realistic description of air temperature inversions is essential for accurate snow and glacier ice melt, and glacier mass-balance simulations. A physically based snow evolution modeling system (SnowModel) was used to simulate 8 yr (1998/99–2005/06) of snow accumulation and snow and glacier ice ablation from numerous small coastal marginal glaciers on the SW part of Ammassalik Island in SE Greenland. These glaciers are regularly influenced by inversions and sea breezes associated with the adjacent relatively low temperature and frequently ice-choked fjords and ocean. To account for the influence of these inversions on the spatiotemporal variation of air temperature and snow and glacier melt rates, temperature inversion routines were added to MircoMet, the meteorological distribution submodel used in SnowModel. The inversions were observed and modeled to occur during 84% of the simulation period. Modeled inversions were defined not to occur during days with strong winds and high precipitation rates because of the potential of inversion breakup. Field observations showed inversions to extend from sea level to approximately 300 m MSL, and this inversion level was prescribed in the model simulations. Simulations with and without the inversion routines were compared. The inversion model produced air temperature distributions with warmer lower-elevation areas and cooler higher-elevation areas than without inversion routines because of the use of cold sea-breeze-based temperature data from underneath the inversion. This yielded an up to 2 weeks earlier snowmelt in the lower areas and up to 1–3 weeks later snowmelt in the higher-elevation areas of the simulation domain. Averaged mean annual modeled surface mass balance for all glaciers (mainly located above the inversion layer) was −720 ± 620 mm w.eq. yr−1 (w.eq. is water equivalent) for inversion simulations, and −880 ± 620 mm w.eq. yr−1 without the inversion routines, a difference of 160 mm w.eq. yr−1. The annual glacier loss for the two simulations was 50.7 × 106 and 64.4 × 106 m3 yr−1 for all glaciers—a difference of ∼21%. The average equilibrium line altitude (ELA) for all glaciers in the simulation domain was located at 875 and 900 m MSL for simulations with or without inversion routines, respectively.

Representing glaciers in a regional climate model

A glacier parameterization scheme has been developed and implemented into the regional climate model REMO. The new scheme interactively simulates the mass balance as well as changes of the areal extent of glaciers on a subgrid scale. The temporal evolution and the general magnitude of the simulated glacier mass balance in the European Alps are in good accordance with observations for the period 1958–1980, but the strong mass loss towards the end of the twentieth century is systematically underestimated. The simulated decrease of glacier area in the Alps between 1958 and 2003 ranges from −17.1 to −23.6%. The results indicate that observed glacier mass balances can be approximately reproduced within a regional climate model based on simplified concepts of glacier-climate interaction. However, realistic results can only be achieved by explicitly accounting for the subgrid variability of atmospheric parameters within a climate model grid box.

Deterministic Analysis and Upscaling of Bromide Transport in a Heterogeneous Vadose Zone

Conservative solute transport experiments were conducted at a field plot and on an undisturbed soil core from the same site. The hydraulic and solute transport properties were extensively characterized so that the data could be analyzed from a deterministic perspective. To investigate the influence of scale and conceptual model on solute transport in the relatively homogeneous upper soil profile of the field site, breakthrough curves that were collected at different depths in the undisturbed column and in the field experiments were compared and analyzed. The mobile‐immobile model provided a physically realistic description of the column data that was largely independent of the transport distance, and upscaling from the undisturbed core to the field plot was relatively successful. Mean and variance of the Br− travel times were controlled by plot‐scale variability in soil water content and heterogeneity, which was overcome by averaging the concentration values from four locations at the same depth and time, and analyzing the Br− transport behavior as a one‐dimensional process. Differences between the measured and simulated mass balances, average concentration, and the variations in concentration were predicted reasonably well across depth and time. Although prediction of the exact concentration information at a given point was not achieved, this study demonstrates that area‐average Br− transport in a heterogeneous vadose zone can be deterministically quantified.

SNOWMIP2: An Evaluation of Forest Snow Process Simulations

The Northern Hemisphere has large areas that are forested and seasonally snow covered. Compared with open areas, forest canopies strongly influence interactions between the atmosphere and snow on the ground by sheltering the snow from wind and solar radiation and by intercepting falling snow; these influences have important consequences for the meteorology, hydrology, and ecology of forests. Many of the land surface models used in meteorological and hydrological forecasting now include representations of canopy snow processes, but these have not been widely tested in comparison with observations. Phase 2 of the Snow Model Intercomparison Project (SnowMIP2) was therefore designed as an intercomparison of surface mass and energy balance simulations for snow in forested areas. Model forcing and calibration data for sites with paired forested and open plots were supplied to modeling groups. Participants in 11 countries contributed output from 33 models, and the results are published here for sites in Canada, the United States, and Switzerland. On average, the models perform fairly well in simulating snow accumulation and ablation, although there is a wide intermodal spread and a tendency to underestimate differences in snow mass between open and forested areas. Most models capture the large differences in surface albedos and temperatures between forest canopies and open snow well. There is, however, a strong tendency for models to underestimate soil temperature under snow, particularly for forest sites, and this would have large consequences for simulations of runoff and biological processes in the soil.

Re-engineering the eastern Lake Erie littoral food web: The trophic function of non-indigenous Ponto-Caspian species

The trophic roles of key Ponto-Caspian invaders (quagga mussels Dreissena bugensis, amphipods Echinogammarus ischnus and round goby Apollonia melanostomus) within the littoral food web of eastern Lake Erie were quantified using stable isotopes (δ 13C, δ 15N). A dual stable isotope parameter search with a mass balance component was used to assess the isotopic importance of quagga mussels and amphipods as dietary items to two size classes of round goby. The utility of the mass balance simulation was also evaluated as a tool to approximate isotopic contributions of feasible prey and identify gaps incurred by “missing” prey items not included in the sampling. The mass balance dietary simulation, confirmed by stomach content data, indicated that isotopically important prey to small round goby (< 11.2 cm) were chironomids and Ponto-Caspian amphipods, while large round goby (≥ 11.2 cm) showed strong preference for quagga mussels. The dietary mass balance simulation output also supported the isotopic importance of round goby to the somatic growth of smallmouth bass, rock bass and freshwater drum. The isotopic mass balance output for yellow perch was more ambiguous, which may be in line with their known broadly omnivorous diet. The white bass output was in line with published data indicating increasing consumption of round goby for this species, while the brown trout output strongly favoured alewife isotopic contributions. However for white perch and walleye, the mass balance simulations were not in line with their known published diets in Lake Erie, probably due to a lack of key prey items in the sample set (e.g. zooplankton for white perch and shiner species for walleye). As expected, the Ponto-Caspian species have integrated themselves into the littoral food webs, and the “quagga mussel–round goby–smallmouth bass” food chain forms one of the key components within the trophodynamics of Lake Erie.

Mass balance simulation and principal components analysis applied to groundwater resources: Essaouira basin (Morocco)

The water resources of the Essaouira coastal basin (west of Marrakesh) are characteristic of a semi-arid climate and are severely impacted by the climate in terms of quantity and quality. Considering the importance of the Essaouira aquifer in the groundwater supply of a vast region (nearly 1,200 km2), a research study was conducted in order to better understand groundwater evolution in this aquifer system. It is a coastal aquifer located on the Atlantic coastline, southern Morocco, and salinization problems have been reported. Covering the Palaeozoic bedrock, the sedimentary series range from the Triassic to the Quaternary. Besides the possibility of seawater intrusion problems, the geological structures delineate a syncline bordered by the Tidzi diapir (of Triassic age) outcropping to the east and south. This is a recharge area for the aquifer, whereas the main groundwater flow direction is from SE to NW towards the Atlantic Ocean. In spite of the occurrence of calcareous and dolomitic levels, all waters in the Essaouira basin are of the Na–Cl-type. Based on a range of experimental methodologies, combined with PCA and geochemical modelling, it was possible to identify the mineralization processes occurring in the groundwater system, and the importance of the water–rock interaction in the water chemistry. Scenarios were tested using a simple mass balance model through the PHREEQC programme. The reaction path was assumed to be such that waters observed at shallow depths evolved to more mineralized waters. An important contribution of water–rock interaction in groundwater mineralization was found, corroborating the influence of preferential recharge from the Tidzi diapir in the water’s signature. Anthropogenic contamination was also identified and could lead to serious problems with groundwater degradation in the near future, in a country with scarce water resources.

Temperature and Melt Modeling on the Prince of Wales Ice Field, Canadian High Arctic

Abstract Near-surface temperature variability and net annual mass balance were monitored from May 2001 to April 2003 in a network of 25 sites on the Prince of Wales Ice Field, Ellesmere Island, Canada. The observational array spanned an area of 180 km by 120 km and ranged from 130 to 2010 m in altitude. Hourly, daily, and monthly average temperatures from the spatial array provide a record of mesoscale temperature variability on the ice field. The authors examine seasonal variations in the variance of monthly and daily temperature: free parameters in positive-degree-day melt models that are presently in use for modeling of glacier mass balance. An analysis of parameter space reveals that daily and seasonal temperature variability are suppressed in summer months (over a melting snow–ice surface), an effect that is important to include in melt modeling. In addition, average annual vertical gradients in near-surface temperature were −3.7°C km−1 in the 2-yr record, steepening to −4.4°C km−1 in the summer months. These gradients are less than the adiabatic lapse rates that are commonly adopted for extrapolation of sea level temperature to higher altitudes, with significant implications for modeling of snow and ice melt. Mass balance simulations for the ice field illustrate the sensitivity of melt models to different lapse rate and temperature parameterizations.

Methods for estimating CO2 storage in saline reservoirs

Abstract Methods for estimating subsurface volumes in porous and permeable geologic formations are routinely applied in oil and gas, ground water, underground natural gas storage, and UIC disposal evaluations. In general, these methods can be divided into two categories: static and dynamic. The static models require only rock and fluid properties, while the dynamic methods require information about active injection, e.g. injection volumes and reservoir pressures. The static models are volumetric and compressibility; the dynamic models are decline curve analyses, mass (or volumetric) balance, and reservoir simulation. The volumetric method requires a simple geometric description of the formation that includes formation height and area, porosity, and some type of factor that reflects the pore volume that CO2 can occupy. The compressibility method relates the change in pore pressure to the change in water and pore volume. Pore pressure will increase as CO2 is injected. This causes a decrease in water volume and an increase in pore volume. The sum of these changes can accommodate space for CO2 storage. This is primarily an issue for closed reservoirs. For active CO2 injection, in addition to the static methods, dynamic methods can be used. Some geologic formations will incur flat or constant injection rates with variable injection pressure, while other formations will have decreasing injection rate with constant injection pressure. This is primarily due to surface operations and the outer boundary condition of the reservoir (closed or open). A decreasing injection rate trend can be analyzed and extrapolated to an uneconomic injection rate to infer the ultimate storage capacity of an active injection well. Mass or volumetric balance can be used to estimate subsurface injected volumes using cumulative injection volume as a function of pore pressure. Based on the geologic unit, combinations of parameters are used to allow straight line projections of the observed trends to make forecasts of the ultimate storage capacity. Injection zone flow simulation models can be used pre- or post injection, require the most input data and can accommodate a very rigorously defined geologic model. Storage estimates can be made readily from simulation for various development scenarios that include completion interval, well-type, injection rates, and multiple injection well spacing. The data requirements, assumptions and limitations for each of these methods are reviewed. Advantages and disadvantages of applying each method to basin-scale and specific site-scale storage estimates are discussed.

Reconstruction of the annual balance of Vadret da Morteratsch, Switzerland, since 1865

AbstractWe have reconstructed the annual balance of Vadret da Morteratsch, Engadine, Switzerland, with a two-dimensional energy-balance model for the period 1865–2005. The model takes into account a parameterization of the surface energy fluxes, an albedo that decreases exponentially with snow depth as well as the shading effect of the surrounding mountains. The model was first calibrated with a 5 year record of annual balance measurements made at 20 different sites on the glacier between 2001 and 2006 using meteorological data from surrounding weather stations as input. To force the model for the period starting in 1865, we employed monthly temperature and precipitation records from nearby valley stations. The model reproduces the observed annual balance reasonably well, except for the lower part during the warmest years. Most crucial to the results is the altitudinal precipitation gradient, but this factor is hard to quantify from the limited precipitation data at high elevations. The simulation shows an almost continuous mass loss since 1865, with short interruptions around 1920, 1935 and 1980. A trend towards a more negative annual balance can be observed since the beginning of the 1980s. The simulated cumulative mass balance for the entire period 1865–2005 was found to be –46mw.e.