Zonation Approach Research Articles

Capturing neutral and adaptive genetic diversity for conservation in a highly structured tree species.

Preserving intraspecific genetic diversity is essential for long-term forest sustainability in a climate change scenario. Despite that, genetic information is largely neglected in conservation planning, and how conservation units should be defined is still heatedly debated. Here, we use maritime pine (Pinus pinaster Ait.), an outcrossing long-lived tree with a highly fragmented distribution in the Mediterranean biodiversity hotspot, to prove the importance of accounting for genetic variation, of both neutral molecular markers and quantitative traits, to define useful conservation units. Six gene pools associated to distinct evolutionary histories were identified within the species using 12 microsatellites and 266 single nucleotide polymorphisms (SNPs). In addition, height and survival standing variation, their genetic control, and plasticity were assessed in a multisite clonal common garden experiment (16 544 trees). We found high levels of quantitative genetic differentiation within previously defined neutral gene pools. Subsequent cluster analysis and post hoc trait distribution comparisons allowed us to define 10 genetically homogeneous population groups with high evolutionary potential. They constitute the minimum number of units to be represented in a maritime pine dynamic conservation program. Our results uphold that the identification of conservation units below the species level should account for key neutral and adaptive components of genetic diversity, especially in species with strong population structure and complex evolutionary histories. The environmental zonation approach currently used by the pan-European genetic conservation strategy for forest trees would be largely improved by gradually integrating molecular and quantitative trait information, as data become available.

Generalized field-development optimization with well-control zonation

Of concern in the development of oil fields is the problem of determining the optimal locations of wells and the optimal controls to place on the wells. Extraction of hydrocarbon resources from petroleum reservoirs in a cost-effective manner requires that the producers and injectors be placed at optimal locations and that optimal controls be imposed on the wells. While the optimization of well locations and well controls plays an important role in ensuring that the net present value of the project is maximized, optimization of other factors such as well type and number of wells also plays important roles in increasing the profitability of investments. Until very recently, improving the net worth of hydrocarbon assets has been focused primarily on optimizing the well locations or well controls, mostly manually. In recent times, automatic optimization using either gradient-based algorithms or stochastic (global) optimization algorithms has become increasingly popular. A well-control zonation (WCZ) approach to estimating optimal well locations, well rates, well type, and well number is proposed. Our approach uses a set of well coordinates and a set of well-control variables as the optimization parameters. However, one of the well-control variables has its search range extended to cover three parts, one part denoting the region where the well is an injector, a second part denoting the region where there is no well, and a third part denoting the region where the well is a producer. By this, the optimization algorithm is able to match every member in the set of well coordinates to three possibilities within the search space of well controls: an injector, a no-well situation, or a producer. The optimization was performed using differential evolution, and two sample applications were presented to show the effectiveness of the method. Results obtained show that the method is able to reduce the number of optimization variables needed and also to identify simultaneously, optimal well locations, optimal well controls, optimal well type, and the optimum number of wells. Also, comparison of results with the mixed integer nonlinear linear programming (MINLP) approach shows that the WCZ approach mostly outperformed the MINLP approach.

Identifying multiscale zonation and assessing the relative importance of polygon geomorphology on carbon fluxes in an Arctic tundra ecosystem

AbstractWe develop a multiscale zonation approach to characterize the spatial variability of Arctic polygonal ground geomorphology and to assess the relative controls of these elements on land surface and subsurface properties and carbon fluxes. Working within an ice wedge polygonal region near Barrow, Alaska, we consider two scales of zonation: polygon features (troughs, centers, and rims of polygons) that are nested within different polygon types (high, flat, and low centered). In this study, we first delineated polygons using a digital elevation map and clustered the polygons into four types along two transects, using geophysical and kite‐based landscape‐imaging data sets. We extrapolated those data‐defined polygon types to all the polygons over the study site, using the polygon statistics extracted from the digital elevation map. Based on the point measurements, we characterized the distribution of vegetation, hydrological, thermal, and geochemical properties, as well as carbon fluxes, all as a function of polygon types and polygon features. Results show that nested polygon geomorphic zonation—polygon types and polygon features—can be used to represent distinct distributions of carbon fluxes and associated properties, as well as covariability among those properties. Importantly, the results indicate that polygon types have more power to explain the variations in those properties than polygon features. The approach is expected to be useful for improved system understanding, site characterization, and parameterization of numerical models aimed at predicting ecosystem feedbacks to the climate.

Integrating demographic and meteorological data in urban ecology: a case study of container‐breeding mosquitoes in temperate Argentina

Cities are unique ecosystems emerging and growing worldwide due to ongoing urbanising trends. The urban–rural gradient is an excellent setting to evaluate the effect of urbanisation on the distribution of species, a matter of public health concern in the case of disease vectors. Despite this, such distributions are affected by other co‐occurring variables, mainly meteorological, that may be confounded by the urbanisation gradient due to the urban heat island effect and maritime climatological conditions in the case of coastal cities. To aid in the design of ecological studies within the urban–rural transition zone, a mapping protocol was designed and applied to Buenos Aires City and its surroundings. Based on road density and district‐level population counts, a detailed (1 km2 pixel) urbanisation map was obtained which, combined with a temperature map, rendered a final urbanisation × temperature product with six classes. The resulting zonation was tested by modelling the distribution of the vector mosquitoes Aedes aegypti and Culex pipiens in artificial containers. The selected model explained the occurrence of mosquitoes 59% better than chance as a function of the urbanisation × temperature categories and the natural lighting condition of the container. This novel zonation approach allows partitioning of environmental heterogeneity prior to the selection of study sites to avoid confounding gradients and provides multiple advantages, such as making comparisons across cities easier, extrapolating the results of site‐scale experiments and identifying priority areas for control measures.

Is high-resolution inverse characterization of heterogeneous river bed hydraulic conductivities needed and possible?

Abstract. River–aquifer exchange fluxes influence local and regional water balances and affect groundwater and river water quality and quantity. Unfortunately, river–aquifer exchange fluxes tend to be strongly spatially variable, and it is an open research question to which degree river bed heterogeneity has to be represented in a model in order to achieve reliable estimates of river–aquifer exchange fluxes. This research question is addressed in this paper with the help of synthetic simulation experiments, which mimic the Limmat aquifer in Zurich (Switzerland), where river–aquifer exchange fluxes and groundwater management activities play an important role. The solution of the unsaturated–saturated subsurface hydrological flow problem including river–aquifer interaction is calculated for ten different synthetic realities where the strongly heterogeneous river bed hydraulic conductivities (L) are perfectly known. Hydraulic head data (100 in the default scenario) are sampled from the synthetic realities. In subsequent data assimilation experiments, where L is unknown now, the hydraulic head data are used as conditioning information, with the help of the ensemble Kalman filter (EnKF). For each of the ten synthetic realities, four different ensembles of L are tested in the experiments with EnKF; one ensemble estimates high-resolution L fields with different L values for each element, and the other three ensembles estimate effective L values for 5, 3 or 2 zones. The calibration of higher-resolution L fields (i.e. fully heterogeneous or 5 zones) gives better results than the calibration of L for only 3 or 2 zones in terms of reproduction of states, stream–aquifer exchange fluxes and parameters. Effective L for a limited number of zones cannot always reproduce the true states and fluxes well and results in biased estimates of net exchange fluxes between aquifer and stream. Also in case only 10 head data are used for conditioning, the high-resolution characterization of L fields with EnKF is still feasible. For less heterogeneous river bed hydraulic conductivities, a high-resolution characterization of L is less important. When uncertainties in the hydraulic parameters of the aquifer are also regarded in the assimilation, the errors in state and flux predictions increase, but the ensemble with a high spatial resolution for L still outperforms the ensembles with effective L values. We conclude that for strongly heterogeneous river beds the commonly applied simplified representation of the streambed, with spatially homogeneous parameters or constant parameters for a few zones, might yield significant biases in the characterization of the water balance. For strongly heterogeneous river beds, we suggest adopting a stochastic field approach to model the spatially heterogeneous river beds geostatistically. The paper illustrates that EnKF is able to calibrate such heterogeneous streambeds on the basis of hydraulic head measurements, outperforming zonation approaches.

Biologically relevant scales in large mammal management policies

The African elephant is an important keystone species that may have significant effects on ecosystem structure and eco-tourism revenues. In Kruger National Park (KNP), South Africa, where elephant populations have been increasing, management have adopted a zonation approach, with zones identified for specific and measurable management interventions to control elephant populations, or to reduce conflict with humans. Localised culling is one proposed management intervention. The zones, partly derived from static annual elephant distribution surveys, are intended to encompass only localised effects on elephant within that zone, assuming no effect into adjacent undisturbed zones, or into contiguous neighbouring landholdings outside KNP. We deployed 17 GPS/GSM collars on free-roaming elephant herds within KNP to assess their seasonal home-range use and size and daily movement paths. These temporally robust movement metrics were analyzed against the Park’s elephant management zones, partly derived from sporadic telemetry fixes and static distribution counts. Multiple daily and seasonal spatial shifts by elephant across neighbouring zones, including into adjacent reserves, rendered the principle of exclusive zoning at this management scale incorrect. The KNP management zones and proposed management actions are not biologically relevant to elephant, or appropriate for managing the ecological or human-wildlife impact of elephant, resulting in spatial and temporal scale mismatches. We predict that the intended management actions, specifically culling, and its resultant intended consequences (immigration, reduced vegetation impact and reduced growth due to disturbance) is not localised to the target zone, and, because it is season specific, is at risk of targeting transient non-resident elephant whilst missing resident elephant that have crossed into other zones. This scale mismatch may have a ripple effect outside the target zone, causing serious ecological risks, especially given the documented long-term negative effects of management disturbance on elephant. We further quantify this scale mismatch into four categories based on percentages of the following factors: the proportion of sampled population affected, the seasonal zone occupancy (the proportion of locations per zone per season) and number of zone crossings, and the governance of management units (consistency of management interventions imposed across zones). This generates a prediction of the risk of this exclusive zoning and its consequences. We suggest a new approach, whereby, known elephant intensity of use at local scales is adaptively managed for specific management objectives. However, management must occur within a known and contained zone of influence defined by elephant behaviour derived from resident movement studies, as opposed to broad scale zonation at the population or park level.

Zoning Abrupt Environmental Pollution Risk in a Mega-city

Major abrupt environmental pollution accidents can cause huge socio-economic losses and seriously damage the environment. Zoning of abrupt environmental pollution risk can greatly aid decision-making and governance, with a view to preventing and mitigating such pollution accidents in a typical mega-city. The present paper proposes a risk system for environmental pollution accidents, which comprises an index system and a quantitative risk assessment model of environmental risk zonation. The system is based on data on past abrupt environmental pollution accidents, regional environmental risk theories, and natural disaster risk theories. An Abrupt Environmental Pollution Risk Zonation (AEPRZ) approach, applicable to a large area, is proposed, which involves the selection of appropriate zonation principles, units, and indexes for the measurement and classification of environmental risk, amending the zonation, and then mapping risk zonation with GIS tools. The AEPRZ approach is applied to the risk zonation of environmental pollution accidents in Minhang District, Shanghai, China, which was divided into four zones according to high, medium, low, and very low degrees of risk. In each zone, each of the socio-economic, hazard, vulnerability, and overall risk factors is assigned a specific degree of risk, thus providing a basis for the implementation of control measures as part of environmental risk prevention management.

サンゴ礁裾礁における空間構造把握のための自然地理的ユニットの設定―与論島東部サンゴ礁を例に―

The spatial structures of a 101-103 m scale on coral reefs were understood by reading aerial photographs and investigating the topography of the fringing reef at the eastern part of Yoron Island, Ryukyu Islands. This study set a new physiographic unit (PGU) at the coral reefs as well as studied zonation. PGU has the following characteristics. (1) In an aerial photo, a linear pattern comprising micro-landform arrangements is recognized on the reef flat; (2) Seawater flowing beyond the reef crest from the open sea and entering the moat before returning to the open sea through a breakout in the reef crest or a channel flowing parallel to the shoreline constitute a very common pattern in the research area; (3) The series of currents observed in the area constitute a water system resembling a drainage water system on land and 4 systems were arranged at the eastern part of Yoron Island ; (4) The movement of seawater is controlled by landforms such as reef crests, channels and lands (a cape), which might qualify as borders of PGUs ; (5) Movements controlled by such landforms are dominant, and tend to be longer in terms of time. In this study, a physiographic unit is defined as follows. (1) A unit that is distinguishable from other adjacent areas by its geomorphological borders ; (2) And, a unit that is distinguishable from other adjacent areas when referring to the movement systems of seawater and materials.The notion of spatial structures of coral reefs of a 101-103 meter scale was substantiated by this research using the overlapping zonation approach known here as PGU on reef flats. The spatial structure makes a frame of the coral reef ecosystem. Therefore, setting a PGU is thought to be effective for application to coral reef conservation.

A steady state redox zone approach for modeling the transport and degradation of xenobiotic organic compounds from a landfill site

A redox zonation approach is used as a framework for obtaining biodegradation rate constants of xenobiotic compounds in a landfill plume (Grindsted, Denmark). The aquifer is physically heterogeneous in terms of a complex zonation of different geological units close to the landfill and biogeochemically heterogeneous in terms of a specified redox zonation. First-order degradation rates of six organic compounds (benzene, toluene, ethylbenzene, o-xylene, m/ p-xylene, and naphthalene) were calculated in the methanogenic/sulfate- and Fe-reducing zones. The numerical simulations show that all compounds are anaerobically biodegraded, but at very different rates. High rates of biodegradation of most of the compounds (except benzene) were found in the Fe-reducing zone. These rates generally agree with previously published rates. Only o-xylene and toluene were significantly biodegraded in the methanogenic/sulfate-reducing environment. All rates in this redox zone are generally much lower than previously published rates.

The generation of USDA-equivalent extreme minimum temperature models and a comparison with Canada’s plant hardiness zones

Hardiness zones are widely used in North America to support the trade of plants and recommendations on local use of perennial plant species. In Canada, two zonation approaches are in use, a made-in-Canada model that integrates seven climate variables and the United States Department of Agriculture’s (USDA) extreme minimum temperature map/model. In this paper we develop and present several extreme minimum temperature models for the 1961–1990 and 1971–2000 climate normal periods and annual models for the winter seasons of 1961 through 2000. These models are similar in nature to the USDA plant hardiness model/map. We compare these models with a recent update of the Canadian plant hardiness zones developed with the same mathematical interpolation techniques (thin plate smoothing splines). Individual Canadian zones typically span five to nine USDA equivalent sub-zones in total, although most of the area (>75%) of each zone generally spans 3–4 USDA sub-zones. We note that there is no simple transformation of one zonation approach to the other, but values for both systems can now be obtained for any location in Canada using an internet mapping tool. Over the period of 1961–2000 extreme minimum temperature has been trending upward in most provinces. These trends may be affecting plants in some locations, but a lack of survival and/or hardiness data is a significant impediment to assessing this. Variation in extreme minimum temperature over the 1961 to 2000 period was greatest in western North America, particularly interior British Columbia. Key words: Climate mapping and trends, spatial analysis, ANUSPLIN

Phytomass, LAI, and NDVI in northern Alaska: Relationships to summer warmth, soil pH, plant functional types, and extrapolation to the circumpolar Arctic

We examined the effects of summer warmth on leaf area index (LAI), total aboveground phytomass (TAP), and normalized difference vegetation index (NDVI) across the Arctic bioclimate zone in Alaska and extrapolated our results to the circumpolar Arctic. Phytomass, LAI, and within homogeneous areas of vegetation on acidic and nonacidic soils were regressed against the total summer warmth index (SWI) at 12 climate stations in northern Alaska (SWI = sum of mean monthly temperatures greater than 0°C). SWI varies from 9°C at Barrow to 37°C at Happy Valley. A 5°C increase in the SWI is correlated with about a 120 g m−2 increase in the aboveground phytomass for zonal vegetation on acidic sites and about 60 g m−2 on nonacidic sites. Shrubs account for most of the increase on acidic substrates, whereas mosses account for most of the increase on nonacidic soils. LAI is positively correlated with SWI on acidic sites but not on nonacidic sites. The NDVI is positively correlated with SWI on both acidic and nonacidic soils, but the NDVI on nonacidic parent material is consistently lower than the NDVI on acidic substrates. Extrapolation to the whole Arctic using a five‐subzone zonation approach to stratify the circumpolar NDVI and phytomass data showed that 60% of the aboveground phytomass is concentrated in the low‐shrub tundra (subzone 5), whereas the high Arctic (subzones 1–3) has only 9% of the total. Estimated phytomass densities in subzones 1–5 are 47, 256, 102, 454, and 791 g m−2, respectively. Climate warming will likely result in increased phytomass, LAI, and NDVI on zonal sites. These changes will be most noticeable in acidic areas with abundant shrub phytomass.

Vegetation development and introduction of agriculture to Saaremaa Island, Estonia: the human response to shore displacement

Three pollen profiles from Saaremaa Island (West Estonian Archipelago) record vegetation history from the early Holocene up to the present, and land-use history since the late Mesolithic. A new numerical zonation approach for distinguishing between human and climatic impacts in the pollen record in boreal forest is suggested. Zonation and correlation of the studied profiles suggests four pollen-assemblage zones, regarded as regionally significant. Land uplift, in interaction with a milder climate and easily cultivated soils, facilitated by changing economy, has been the most important factor during the colonization and management of coastal areas. Human impact on Saaremaa Island may be divided into four main phases: (a) Mesolithic and Early Neolithic forest disturbance by hunter-gathering people; (b) forest clearances, pastoral farming and first attempts of cereal cultivation by Neolithic people; (c) more regular cultivation with introduction of slash-and-burn agriculture since the Late Neolithic; (d) permanent field cultivation since the Migration Period/Viking Age.

Conditioning to dynamic data: an improved zonation approach

An optimization method for incorporating dynamic data into reservoir modelling is presented. It integrates a very typical feature of the zonation approach that is based upon dividing the reservoir model into subregions. Solving the optimization problem consists of adjusting the subregion pattern so that the reservoir model duplicates the observed dynamic behaviour. Unlike the traditional approach, permeabilities in subregions are not constant, but show spatial variations. A variogram model that is the same for all the subregions describes this variability. The suggested method allows for optimization of permeability distributions within the subregions while preserving the second-order statistics for the whole reservoir model as well as the spatial continuity between subregions. It remains as flexible as the traditional zonation approach although it can handle complex structures.

Agroecological zones and the assessment of crop production potential

The rapidly growing world population puts considerable pressure on the scarce natural resources, and there is an urgent need to develop more efficient and sustainable agricultural production systems to feed the growing population. This should be based on an initial assessment of the physical and biological potential of natural resources, which can vary greatly. The agroecological zonation (AEZ) approach presents a useful preliminary evaluation of this potential, and ensures that representation is maintained at an appropriate biogeographic scale for regional sustainable development planning. The principal AEZs of the world, as described by the Technical Advisory Committee of the Consultative Group on International Agricultural Research, are presented along with their extent and characteristics. Net primary productivity of terrestrial vegetation can be assessed from weather data, and it varies from 1 t dry matter ha −1 yr −1 in high latitude zones and dry regions to 29 t ha −1 yr −1 in tropical wet regions, depending on the climatic conditions. To assess the crop production potential, length of the growing period zones, a concept introduced by the UN Food and Agriculture Organization, is very useful as it describes an area within which rainfall and temperature conditions are suitable for crop growth for a given number of days in the year. These data, combined with the information on soils and known requirements of different food crops, can be used to assess the potential crop productivity. Some perspectives on AEZs and crop production potential are presented by describing the manner in which production potential can be integrated with present constraints. Efforts to intensify production should place emphasis on methods appropriate to the socio-economic conditions in a given AEZ, and on promotion of conservation-effective and sustainable production systems to meet the food, fodder and fuel needs for the future.

Improved Reservoir Characterization Using Automatic History Matching Procedures

Abstract The primary task in reservoir history matching is the estimation of reservoir parameters such as porosities and permeabilities so that the model predictions match as closely as possible the field measurements. In actual practice, prior estimates of the most probable values of the parameters are usually available. Bayesian estimation was used to incorporate this prior information into a 3-D 3-Phase reservoir simulator with automatic history matching capabilities. In addition, minimum and maximum constraints were imposed on the parameter values. A case study is presented where the postulated reservoir model is quite different from the actual reservoir. It is shown how parameter estimates obtained by automatic history matching may be used to help modify the postulated model These included changes to reservoir boundaries and detection of impermeable barriers within the reservoir. Estimates of predicted in-place hydrocarbon volumes were also compared with actual values. The final reservoir description is shown to be a significant improvement over the initial postulated model. Introduction In the history matching phase of a reservoir simulation study, the problem is to develop a grid cell model that represents the geological structure of the underground reservoir and to specify the distribution of reservoir parameters such as porosity and permeability so that the model predictions match the observed field data. We(1) have recently developed an efficient three-dimensional three-phase reservoir simulator with automatic history matching capability. Using an industry standard problem to generate artificial observation data, it was shown that the model was able to restore the original value of the permeability and porosity. We have also demonstrated how the model can be used to provide quantitative estimates of the reliability of the calculated parameters, and thus to identify the zones that have a significant effect on the match of the field data(2). The postulated grid cell models used in the evaluation of the automatic history matching procedure were identical to the actual models used to generate the artificial observation data through random noise was added to represent measurement errors in the field. However, in an actual field study, the postulated grid cell model may not accurately represent the reservoir description since the geological interpretation of seismic data and well samples may be in error. In addition, the variation in rock properties will be such that the postulated grid cell model will not have enough detail to represent it. Several researchers(3, 4) have attempted to use very fine grids with hundreds of thousands of cells to model reservoir heterogeneities. Unfortunately, with current computer hardware and numerical techniques, it is still not possible to use many thousands of parameter to describe the variation in porosity and permeability in reservoir rock both areally and vertically. We have to resort to a zonation approach whereby the reservoir is divided into a relatively small number of zones In each of which the parameters have constant values that have to be estimated. The size, shape and arrangement of these zones in tile postulated model will definitely be quite different than the true reservoir distribution.

Assessing Human Disturbance of Breeding Bald Eagles with Classification Tree Models

We recorded 4,188 events of human activity and associated bald eagle (Haliaeetus leucocephalus) response in the vicinity of 13 central Arizona nest sites during 1983-85. A hierarchical classification of 9 dependent and 3 independent parameters was developed to quantify pedestrian, aquatic, vehicle, noise (gunshot/sonic boom), and aircraft disturbance groups. Type and frequency of response varied inversely with the distance from an eagle to the disturbance. Bald eagles were more often flushed from perches than nests and were most easily disturbed when foraging. Pedestrian was the most disturbing human activity, whereas aircraft was the least. We developed classification tree (CART) models for pooled and group disturbances to evaluate response severity and to formulate disturbance-specific management criteria. Response frequencies and critical distances for pooled disturbance were 64% at 583 m. Frequencies, distances, and the influence of secondary characteristics varied among disturbance groups. The CART models ranked distance to disturbance as the most important classifier of eagle response, followed in decreasing order of discriminatory value by duration of disturbance, visibility, number of units per event, position relative to affected eagle, and sound. This procedure offers improved specificity in human disturbance assessment. J. WILDL. MANAGE. 55(3):500-511 The variable effects of human activity on the reproductive performance of bald eagles (Grier 1969, Fraser 1985) imply a threshold for detrimental impact between pristine isolation and outright destruction. Because that threshold can be highly variable and often subtle, its determination is difficult and requires controlled experimentation (Grier and Fyfe 1987). Yet, experimental disturbance research on bald eagles is limited, with major emphasis on flushing distances and frequencies (Stalmaster and Newman 1978, Knight and Knight 1984, Fraser et al. 1985). Distance has been the primary mechanism of protection in traditional breeding bald eagle management, with distance guidelines typically applied unilaterally to all disturbance types. Management concepts to protect nesting bald eagles have evolved from concentric-circle buffer zones at nest sites (Mathisen 1968), through single territory zonation (Mathisen et al. 1977, U.S. Fish Wildl. Serv. 1981), to a multiple territory, regional approach (e.g., F. B. Isaacs and G. Silovsky, Bald Eagle Manage. on the Fremont Natl. For., U.S. For. Serv., Lakeview, Oreg., 1981). These distance-oriented zonation approaches also have included temporal control and audio/visual buffering guidelines. Because of the complex, multivariate nature of disturbance thresholds, site-specific management guidelines have been consistently recommended. Various aspects of disturbance (i.e., distance, noise, timing, position, visibility) have been mentioned or specifically addressed in previous bald eagle research (Grubb 1980, Hansen et al. 1980, Andrew and Mosher 1982). Knight and Knight (1984) postulated that flight distances licited by different types of disturbances during different bald eagle behaviors could be used to develop zones for restricting human activities. However, simultaneous identification and analysis of an inclusive range of dependent and independent factors inherent in disturbance management are lacking. We present a hierarchical scheme for evaluating potentially disturbing human activity. With data collected following that scheme, we develop disturbance-specific, quantitative models for predicting bald eagle response frequencies and for formulating management criteria. Although we do not present a disturbance threshold for detrimental impacts on reproductive performance, we intend these techniques to be a step toward that goal by being more specific in assessing disturbance. We thank the 71 Forest Service volunteers and the many professional personnel of the Tonto, Prescott, and Coconino national forests whose dedication and field assistance during 1983-85

Reservoir History Matching by Bayesian Estimation

Abstract The estimation of reservoir properties is inherently an underdetermined problem (one having a nonunique solution) because of the large number of unknown parameters relative to the available data. parameters relative to the available data. The common zonation approach to reducing the number of parameters introduces considerable modeling error by insisting that reservoir properties are uniform within each zone and by assigning the boundaries of these zones more or less arbitrarily. In this paper, Bayesian estimation theory is applied to history matching as an alternative to zonation. By using a priori statistical information on the unknown parameters, the problem becomes statistically better determined. Bayesian estimation and zonation are applied to the problem of porosity and permeability estimation in a one-dimensional, permeability estimation in a one-dimensional, one-phase reservoir. Introduction The estimation of parameters such as porosity and permeability in a reservoir model using well production and pressure data is commonly referred production and pressure data is commonly referred to as history matching. Although an inhomogeneous reservoir is in principle specified by an infinite number of parameters, a computational reservoir model can only contain a finite number. The most detailed description is obtained by allowing porosity and permeability to vary independently at each block of the spatial grid used in the finite-difference solution. While minimizing the modeling error, this approach entails a great deal of uncertainty because of the large number of unknowns compared with the limited data available. Thus, in a given problem, many different sets of property estimates problem, many different sets of property estimates may provide satisfactory and essentially indistinquishable data fits. Some of these parameter estimates can be grossly in error with respect to the actual properties, and as a result can lead to erroneous prediction of future reservoir behavior. To reduce the statistical uncertainty one must either decrease the number of unknowns or utilize additional information. A commonly used procedure for reducing the number of unknown parameters is zonation; the reservoir is divided into a small number of zones, in each of which the properties are treated as uniform. A modeling error is thus introduced through the assumption of uniform properties within each zone and through the more or less arbitrary assignment of the zone boundaries. As the number of zones is decreased, the error due to statistical uncertainty decreases while the modeling error increases. The total error passes through a minimum at some intermediate number of zones. The specification of this optimum level of description, which has been briefly considered in past work, will be treated in detail in a future report. An alternative to decreasing the statistical uncertainty by reducing the number of unknown parameters is the utilization of additional parameters is the utilization of additional information. This information need not be limited to measurements on the reservoir under study, but can be based on prior geological information about property variability in reservoirs of the same type. property variability in reservoirs of the same type. This paper examines this alternative method of reducing statistical uncertainty. The prior geological information is utilized by a formulation akin to classical Bayesian estimation. The Bayesian estimation is illustrated and is compared with the zonation approach for the case of a hypothetical, one-dimensional reservoir with variable porosity and permeability. The numerical simulations are used to investigate questions such as the optimum number of parameters in zonation and the effect of erroneous prior statistics in Bayesian estimation, and to compare the two methods. Considerable attention is also given to computational aspects such as convergence rate and computer time required by two of the most commonly used minimization algorithms, Marquardt's and the conjugate gradient. NATURE OF PRIOR GEOLOGICAL INFORMATION The application of probabilistic models in geology is the subject of a recent review. SPEJ P. 337