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Preprocessing using GIS for Environmental Modeling

Preprocessing using GIS for Environmental Modeling. 　Introduction 　GIS and Environmental modeling: Preprocessing using GIS includes: 　－　Integration of many different data types 　－　Set up of the conceptual model for the modeling tasks GIS data type for modeling

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Preprocessing using GIS for Environmental Modeling

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  1. Preprocessing using GIS for Environmental Modeling • 　Introduction • 　GIS and Environmental modeling: • Preprocessing using GIS includes: • 　－　Integration of many different data types • 　－　Set up of the conceptual model for the modeling tasks • GIS data type for modeling • GIS Interface with GeoSys • Interpolation • Mapping

  2. Maintaining and Editing GIS data Collecting GIS data Analyzing GIS data Presenting GIS data General information: The GIS Workflow GIS is a powerful set of tools for collecting, storing, transforming and displaying spatial data from the real world. GIS provides a means of representing the real world by using integrated layers of constituent spatial information. The Data required for hydrogeological applications are complex; information from the fields of geology, hydrology, geomorphology, soil science, climatology, land use and topography are needed. Those information can be represented in GIS as objects, such as points, lines, and areas. There are six core activities of GIS that can be applied in geoscience application: data organization, data visualization, spatial data query, integration of diverse data type, data analysis and prediction.

  3. GIS and Environmental Modeling, continued… GIS has been particularly important for Environment modeling (EM) applications for data collection, data organization, and distribution of hydrogeological data and construction of maps. EM simulates the function of environmental process. Such simulation requires data about the system within which the process occurs. GIS can serve as a common data and analysis framework for the EM. The tools in GIS, such as the database management, spatial analysis and graphical display can help to reduce the time and cost spent on the preprocessing and postprocessing part in the EM and make the model more accurate than before.

  4. GIS and Environmental Modeling Linking GIS and EM software combines the functionality of two independently designed software modules and links them through common files has been quite successful over last two decades. In such combinations, GIS usually performs functions that can be characterized as preprocessing or postprocessing. Preprocessing includes coordinate transformation and projection change, resampling and conversion between data models and structures, clipping to fit study areas, and analysis. Postprocessing includes cartographic and visual display, simple spatial analysis of results, verification.

  5. How the GIS could help in the preprocessing part? There are two major aspects: First: common data structure The EM often maintain data of many sources, such as data from geology, geophysics, geochemistry, hydrology and so on, and GIS is an invaluable tool for integration of many different data types. The required data for modeling purpose can be prepared in GIS as layer models. Layers can be represented in two ways: in vector format as points, lines, polygons and in raster format as pixels. The ability to store hydrogeological information in a common understandable structure combined with the capabilities of GIS software will facilitate the integration of applications and models.

  6. Second: construct the conceptual model The construction of any representation of a real system requires the development of a conceptual model. The purpose of building a conceptual model is to simplify the field problem and organize the associated field data. The closer the conceptual model approximates the field situation, the more accurate is the numerical model. In GIS, this conceptual model rests first on the representation of geographic features within a spatial domain by data connected to layers of points, lines, polygons, or grids, cells. Then new data are created by processing the existing data layers based on the GIS functions. The first step in formulating the conceptual model is to define the area of interest, i.e., to identify the boundaries of the model. By using the georeferenced GIS map, the boundary could be exactly extracted. In addition to that, we also need to identify the boundary condition, initial condition, source sink term, distribution of material properties.

  7. Thematic Data preparation in GIS • -study area domain • -hydrological units • Wadis and springs • -faults • -wells • -water level contour map • -boundary conditions • Initial conditins • Source sink term • distribution of material properties

  8. GIS Data Types for Modeling, continued… • Within GIS, one can create a continuous space or a discrete space model. Vector GIS is a discrete space model in which the data layers contain an arrangement of points, lines or areas. Each point, line or area is an individual entity described by a data record. There are several vector data which can be used for the modeling purposes. • Vector data - discrete space model: • Point Data: Pumping wells(ST); Boreholes; Wells for BC and IC • Polyline Data: Delineation of source term; Representation of faults; Localization of boundary conditions and initial conditions • Surface Data: Areal distribution of initial conditions; Localization of boundary conditions; Areal distribution of material properties • Volume Data: part of GIS restrictions - no full 3D functionality; Volume data construct 3D structural model using GIS integration method

  9. GIS Data Types for Modeling • In addition to vector GIS, raster model or continuous space model are represented by a surface over the analysis domain whose horizontal plane is subdivided into regular areas, usually rectangular cells. The most common raster model used in EM are digital elevation model and digital terrain model. • Raster data – continuous space model: • Digital Elevation Model (DEM): regularly spaced grid of elevation points • DEM is used to create a topographical surface for the modeling area. • Digital Terrain Model (DTM) : A DTM is a digital file consisting of terrain elevations for ground positions at regularly spaced horizontal intervals. DTM may be used in the same way as DEM to generate the topographical surface of a modeling area. • Lithological Layer Data: for the generation of a 3D subsurface model

  10. Interpolation Normally, for the generation of a 3D subsurface model, lithological information of each geological layer is required. Observation wells (boreholes) are used to get the geometric information of some locations, but because of the data limitation for both subsurface and surface layer; interpolation tools are used to estimate between known points. a regular raster is created from sparse and irregular data using available interpolation techniques in GIS: inverse distance weighted, spline, kriging, and natural neighbors. Especially for the subsurface modeling, the data from the underground study is always limited. So, using these interpolation tool results in more trendy information underground. The data can saved in two ASCII formats: Surfer - .dat ArcGIS -.asc

  11. Mapping: Surface mapping is the process of making the mesh conforms to stratigraphic irregularities, i.e. thickness and orientation of the mesh slices can be deformed. Different data types can be used; grid files created with Surfer(.dat)or grid files created with ArcGIS, which uses a (.ASC) extension. For example one example from the brand case study, and there are 10 DAT files for 10 rows from uppermost to lowermost: upperboundary.dat, surface2.dat, surface3.dat, surface4.dat, surface5.dat, surface6.dat, surface7.dat, surface8.dat, surface9.dat, surface10.dat For example, the nodes of prism elements with Z coordinates equals 0.0 will be mapped using the data given in upperboundary.dat. After mapping, based on the domain (created from volumes which are defined from surfaces), the 9 layers will be mapping into the corresponding vertical height.

  12. Material properties: From the geological formation of the modeling domain, a layer subsurface conceptual model is build. For each layer, they have different material group distribution. The following GIS thematic map is prepared for the material properties for one of those nine layers in brand case. Each color means one material group:

  13. Source Term Excel file ST ArcGIS BC Boundary Condition Shp2GLI Interface: Shp2GLI MAT Material Properties Initial Condition GeoSys IC MshObj Point Polyline Surface Volume Domain GeoObj ELE Topologic Objects Geometric Objects NOD Integration of GIS and GeoSys/RockFlow: We take ArcGIS as GIS software. Shape file is a well-known spatial data format which allows data sharing among application

  14. GIS Interface: After importing the GIS layers through the interface, the 2D Geo-objects in GeoSys such as point, polyline,and surface together with an extenal database file could be used not only for locating source term, boundary condition, material properties, initial condition but also as the input file for creating finite element meshes, such as nodes and elements.

  15. Number Case Study Features 1 2D Tübingen groundwater model 2 Flow and Heat Transport Model in the Zarqa Ma’in – Jiza Areas in Central Jordan 3 Groundwater Model for the Jericho Plain Area of Palestine / Lower Jordan Rift Valley 4 3D Groundwater Model in Brand Area examples:

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