For the past 15 years, leaders in Hydro GIS meet on Sunday at Esri’s User Conference to showcase GIS solutions for water resources, such as Arc Hydro, and Arc Hydro Groundwater. The workshop has historically been an event where the leading academics in hydro research come together with GIS users in the water resources industry to show and tell about hydro projects and solutions.
This year we continued that tradition with presentations about new developments and future directions for Arc Hydro and Arc Hydro Groundwater, partner presentations by KISTERS and Groundswell Technologies, as well as exciting uses of the software for water resources, and presentations about where hydro GIS is headed. In addition, this year the Mapping Center Team unveiled many new hydro-related offerings, such as the Hydro Basemap, the High Water Map, and a number of hydro-related soil maps.
Overall, the day was full of exciting new products and solutions, and left the audience with a clear idea of what to look forward to in the coming years, not only from Esri, but from the Hydro Community as a whole. If you missed the meeting this year, be sure to attend next year, because registration is FREE and it’s a great way to stay in the loop, or as a forum to showcase your own work and solutions with GIS and Water Resources. If you would like to be on the meeting invite list for next year, please contact Esri’s Global Water/Wastewater, Water Resources Industry Manager, Lori Armstrong (firstname.lastname@example.org). And, a special thanks goes out to Dewberry for providing breakfast!
Attendees of this year’s Water Resources Workshop.
All of the presentations from the Workshop are available in the Hydro Resource Center Education Gallery.
Hydro Resource Center Education Gallery content from the 2011 Esri User Conference.
Topping off the week of water, the Water/Wastewater/Water Resources Pool Party that occurs every Wednesday of the User Conference at the Hilton Bayfront was again one of the best evening gatherings of the week. Live music and dancing, great food and beverages, and even better company made this event a great networking opportunity to find others in the water community, share your experiences, and make new water friends!
Here are some pictures of the fun event:
We hope to see you at the Water Resources Workshop and Water/Wastewater Party next year!
Thank you to all our UC sponsors.
Special thanks to Caitlin Scopel for providing this post. Questions for Caitlin: email@example.com
Developing an Inventory of Groundwater Resources for the Saguenay-Lac-Saint-Jean region, Quebec (Canada)
A methodology based on a combination of “RDBMS (Relational Database Management System) – ArcGIS – Arc Hydro Groundwater (AHGW)” technologies is illustrated using data from an on-going project aimed at developing an inventory of the groundwater resources of the Saguenay-Lac-Saint-Jean region, Quebec (Canada).
The implementation of a spatial database has been mandated by the Quebec Ministry of Sustainable Development and Parks (MDDEP) for the Saguenay-Lac-Saint-Jean region (SLSJ) of the province of Quebec in Canada. This provincial project, known as PACES (“Programme d’Acquisition des Connaissances sur les Eaux Souterraines”), is being conducted in partnership with the regional municipal counties (MRC), the MDDEP, the City of Saguenay and the “Université du Québec à Chicoutimi (UQAC)”. The spatial database is intended to provide a regional picture of groundwater resources in terms of both their quantity and quality. This work involves the compilation of existing hydrogeological data as well as the collection of new data to complete existing information gaps. The final objective of the database implementation consists of characterizing regional aquifers and understanding associated groundwater flow systems. This provincial-scale project should improve our knowledge of regional hydrogeology and provide decision-makers with additional information for the sustainable management of groundwater resources. In order to illustrate the methodology of 3D hydrostructural subsurface modeling with AHGW, Chesnaux et al. (2011), selected a 225 km2 region centered on the municipality of Shipshaw in the SLSJ region. The Shipshaw area was selected for its large number (261) of boreholes available in the region.
Location and digital elevation model (DEM) of the Saguenay-Lac-St-Jean region of Quebec and location of the Shipshaw study area (after Chesnaux et al., 2011).
The AHGW Geodatabase
An AHGW database has been created using the Arc Hydro Groundwater data model template, which was customized for the project. The main table is called Wells and corresponds to the Borehole central table of the geodatabase, which actually locates the wells. This table is associated with the BoreholeLog table which corresponds to the stratigraphy table of the geodatabase. The other relevant table of the AHGW database is entitled HydrogeologicUnit and lists the geological nature of the subsurface materials, their identifier, their definition and their code. This table corresponds to the facies code of the stratigraphy table of the geodatabase. Other tables of AHGW are output tables derived from the AHGW geomodeling results (BoreLine, SectionLine, BorePoint, GeoSection, GeoRaster and GeoVolume).
AHGW geodatabase structure used for the project.
Application of Tools to Create Maps/Cross Sections/3D Subsurface Models
The development of a 3D subsurface model included four main steps: borehole classification, creation of 2D cross sections, creation of 3D GeoSections from the 2D cross sections, and the creation of a 3D model including GeoRasters and GeoVolumes.
The borehole editor tool available in the AHGW toolset allows for visualization of a borehole stratigraphy. Each hydrogeological unit encountered within the borehole is assigned a unique hydrogeologic unit identifier (HGUID) observed between a top and bottom elevation of the unit intercepted by the borehole. An original aspect of using AHGW is the concept of BoreLines. Indeed, the borehole data are stored linearly instead of punctually. Each 3D well feature is divided into segments (borelines); to each segment an HGUID identifier is assigned in order to identify the geological unit. BoreLines are created from the BoreholeLog table that presents borehole stratigraphy observed within each borehole.
Editing and visualizing stratigraphy of boreholes using the AHGW borehole editor.
Creation of 2D Cross Sections
An appealing aspect of AHGW is the development of cross sections extracted from the borehole information. A variety of tools included in AHGW allow for building cross sections in ArcMap. The construction of cross sections begins when the user draws a line on the map corresponding to the trace of the required cross section. Then, through the application of a buffer the user can select in the vicinity of the line the particular boreholes needed to be considered for developing the cross section. AHGW creates finally a panel on which the BoreLines corresponding to the selected boreholes are projected. Additional information such as a DEM and outcrops may also be added to the cross section. Using editing tools, the user may create cross section panels by manually interpolating the different geological layers identified in BoreLines.
Steps to create 2D cross sections. From left to right: sketching a section line, adding borehole and outcrop information to the cross section data frame, and sketching cross section panels.
Creation of 3D GeoSections from 2D Cross Sections
A cross section is a 2D representation; however with AHGW it is possible to transform several cross sections into 3D features (GeoSections) that can be viewed in ArcScene. A set of GeoSections can form a fence diagram. From the fence diagram we can assign a HorizonID (numbering system for layers) to each geological unit in each Geosection, an essential step for creating a Geovolumes (see next step).
3D GeoSections created by transforming 2D cross section panels to 3D features.
Creating a 3D Model Including GeoRasters and GeoVolumes
A GeoVolume is a 3D feature for representing volumes within the subsurface. In order to create GeoVolumes, GeoRasters must first be created. A GeoRaster corresponds to the top surface of each identified geological layer; it is a raster surface for representing the top and bottom of hydrogeologic units. GeoRasters are created by interpolating points (BorePoints) derived from borehole stratigraphy and additional points sampled along GeoSection features. These points are created along a GeoSection at the top and bottom elevations of each layer and
characterize the geological unit with the HorizonID. In this example, Inverse Distance Weight (IDW) was applied to interpolate between the BorePoints and create a set of GeoRasters. This approach yielded the best results for our study area. Note that other interpolation options are also available within ArcGIS and may be evaluated independently based on the resulting outcomes. The GeoRasters are linked to a RasterCatalog which is used for storing, indexing and attributing the interpolated rasters. The RasterCatalog associates the identifier of a raster and the identifier of the geological unit. Using the AHGW tools one can automatically create GeoVolumes from GeoRasters.
Steps for creating a 3D subsurface model. From right to left: A set of GeoSections forms a fence diagram (these were created by transforming the 2D cross sections to 3D), GeoRasters are interpolated from the bore data and the additional points sampled along the cross sections, and GeoVolumes are created from the GeoRasters.
A procedure using AHGW for the development of a hydrogeological model has been applied to identify aquifers and reconstruct their boundaries based on the geodatabase and 3D models. The construction of 3D models should help to better predict the extension and thickness of groundwater reservoirs, i.e. groundwater resources availability. Note that the accuracy of the 3D models depends on the amount, the nature and the quality of the information extracted from the geodatabase for incorporation into these models. A greater amount of available data permits more reliable predictions of groundwater resources and greater confidence for the modeler.
A possible application of the 3D subsurface models developed using the AHGW tools is the creation of input data for groundwater flow and transport codes. For example, the 3D hydrostructural models obtained with ArcGIS/AHGW could be exported to a groundwater flow and transport code in order to simulate and predict groundwater flow and groundwater contaminant propagation in the subsurface. However, this application requires further tool development as it is not currently available as an existing AHGW tool.
This project is funded by the Programme d’acquisition de connaissances sur les eaux souterraines du Québec (PACES), with contribution by the Ministère du Développement durable, de l’Environnement et des Parcs, UQAC, Conférence régionale des élus du SLSJ, Ville de Saguenay and the four Municipalités régionales de comté of the SLSJ region. Funding from the Fonds québécois de recherche sur la nature et les technologies (FQRNT) and the Fondation de l’UQAC (FUQAC) are also acknowledged.
For more information on the Arc Hydro
Groundwater tools visit the Aquaveo website.
Chesnaux, R., Lambert, M., Fillastre, U., Walter, J., Hay, M, Rouleau, A., Daigneault, R., Germaneau, D., Moisan, A. 2011. Building a geodatabase for mapping hydrogeological features and 3D modeling of groundwater systems: Application to the Saguenay-Lac-St-Jean Region, Canada, Computers & Geosciences, DOI: 10.1016/j.cageo.2011.04.013.
Special thanks to Dr. Romain Chesnaux for providing this post. Questions for Romain: Romain_Chesnaux@uqac.ca
Almost 10 years of drought in Australia highlighted the need for better management of water resources, which led to the development of a National Water Initiative (NWI) that was signed in 2004. The NWI plan acknowledged the importance of managing groundwater and surface water conjunctively as a ‘whole water cycle’, including a number of areas where development of knowledge, plans, and information systems are required. To support the NWI requirements, a National Groundwater Data and Information Systems workshop was held in Melbourne in December, 2008. One of the outcomes of this workshop was the conception of a National Groundwater Information System (NGIS). The Water Division of the Australian Bureau of Meteorology (BoM) took the lead role in managing the NGIS project.
The first design of the system was done by Australian consulting companies Sinclair Knight Merz (SKM) and Continuum Consulting. The Arc Hydro Groundwater (AHGW) data model was selected as the base for the NGIS design. The AHGW design was extended where necessary to meet key NGIS functional requirements. A step-wise approach was taken in the design and implementation of the NGIS. Initially, a “core” geodatabase focusing on representing boreholes and borehole-related data was designed in detail. This core data model serves as a starting point for implementation.
The core geodatabase design focuses on representing boreholes and related vertical information such as borehole stratigraphy and well construction. The geodatabase includes a Borehole point feature class which represents the location and attributes of a bore. Vertical information (lithology, hydrostratigraphy, and well construction) are stored in tabular format, where there is a separate table for each type of vertical information. The tabular information includes attributes for storing top and bottom elevations for each segment along the bore. These can be stored as depth along the borehole or as absolute (e.g. meters above mean sea level) top and bottom elevations. In addition, the core design includes 3D line feature classes which enable visualizing the vertical information in ArcScene or ArcGlobe. The core design also includes a table for defining hydrogeologic units for the project and a polygon feature class for representing administrative boundaries of groundwater management zones.
Core geodatabase design for Australia’s National Groundwater Information System project.
For the implementation of the data model BoM selected the Arc Hydro Groundwater toolset developed by Aquaveo, LLC. The tools enable users to:
- Use the import wizards to easily import data into the geodatabase
- Sketch geologic and hydrogeologic cross sections
- Prepare water level and water quality maps
- Develop 3D subsurface models
A set of case studies were prepared for testing the core data model with local Australian datasets. The first example shows boreholes in the Musgrave prescribed wells area located in South Australia. The vertical borehole data is stored in the BoreholeLog table, and can be visualized and edited using a borehole editor available in the AHGW tools.
Boreholes in the Musgrave prescribed wells area. Vertical information along the bores is visualized and edited using a borehole editor available in the AHGW tools.
The vertical information can also be visualized as 3D features that are created using the Create BoreLines tool available in the AHGW toolset. The 3D features can be visualized in ArcScene as shown in the figure below.
3D BoreLine features representing the stratigraphy along bores in the Musgrave prescribed wells area.
Water level and water quality data can also be related to the bores, which allows for spatially mapping the measurements. AHGW and standard ArcGIS tools are used together to build a workflow for creating water level maps. The following figure shows an example of a workflow that summarizes measurements for specified time periods, interpolates the values to create a raster, and adds the raster to a raster catalog and indexes it with a “time stamp”. Animation tools can then be applied to animate changes in water levels over time. A detailed description of this process can be found in a previous post.
On the right, a model for automating the process of creating water level maps. On the left, a water level map for the Musgrave prescribed well area.
The examples using local datasets were also used in a set of training classes. Four 3-day training sessions were held in Sydney (luckily we did have time for sightseeing – here are some pictures in front of the famous opera house and with some local kangaroos), Melbourne, and Canberra to help BoM and the jurisdictions staff with implementing the NGIS data model and getting familiar with the AHGW tools.
BoM and jurisdiction staff learning to create 3D subsurface models and implement the NGIS data model.
Users of the NGIS are currently implementing the core geodatabase with borehole data from the different jurisdictions. This data will then be collated to provide a continuous layer of bores and borehole information across Australia. In the next phases of the NGIS project, the core geodatabase will be expanded to include additional groundwater datasets. Hopefully, over time the NGIS will include a wide array of groundwater datasets that will support better analysis and management of groundwater resources across Australia.
Special thanks to Gil Strassberg for providing this post. Questions for Gil: firstname.lastname@example.org
The Geospatial Hydrologic Modeling System (GeoHMS) and River Analysis System (GeoRAS) are geospatial toolkits developed by Esri and the Hydrologic Engineering Center (HEC), an organization within the US Army Corps of Engineers, to aid engineers and hydrologists with limited GIS experience.
The toolkits work in ArcGIS to generate inputs for the Hydrologic Engineering Center’s Hydrologic Modeling System (HEC-HMS) and River Analysis System (HEC-RAS). The GeoHMS and GeoRAS downloads provide a set of procedures, tools, and utilities necessary to prepare, process, and visualize your geospatial data for input into HEC-HMS and HEC-RAS.
In addition, GeoRAS can process HEC-RAS outputs, perform one-dimensional steady and unsteady flow river hydraulics calculations, sediment transport – mobile bed modeling, and water temperature analysis.
HEC is currently working to update GeoHMS and GeoRAS for ArcGIS 10, and they released a statement on their download site announcing the tools availability in “Summer 2011.” It is now officially Summer 2011, which means the tools may become available at any time. So, check back to the Hydro Blog and the HEC download site often for the announcement of GeoHMS and GeoRAS for ArcGIS 10!
Special thanks to Caitlin Scopel for providing this post. Questions for Caitlin: CScopel@esri.com.
Of interest to its hydro customers, Esri has web-enabled four more hydro-related soil maps of the United States from the NRCS SSURGO dataset. The source of the data for these maps is the Map Unit Aggregate Attribute table or MUAGGATT.
The new maps released are as follows:
Ponding Frequency – Presence*
The percentage of the map unit that is subject to water being ponded on the soil surface, expressed as one of four classes; 0-14%, 15-49%, 50-74% or 75-100%.
The shallowest depth to a wet soil layer (water table) at any time during the year expressed as centimeters from the soil surface, for components whose composition in the map unit is equal to or exceeds 15%.
The shallowest depth to a wet soil layer (water table) during the months of April through June expressed in centimeters from the soil surface for components whose composition in the map unit is equal to or exceeds 15%.
The distance from the soil surface to the top of a bedrock layer, expressed as a shallowest depth of components whose composition in the map unit is equal to or exceeds 15%.
In addition to the new maps, some changes were made to the cartography
on the previously released maps entitled Drainage Class-Dominant
Condition and Drainage Class-Wettest. In these webmaps, the new color
scheme has been improved to allow for an easier comparison of soil
drainage characteristics. With the new scheme it is now much easier to
read whether soil drains too much or too little (according to NRCS’
existing classification scheme), and how much or how little in
comparison to neighboring soils.
*These maps are ready to use, but are still beta products at the moment. They will undergo further review, so keep in mind that map colors and the contents page are subject to change. The data is in the same state it was since being provided by the NRCS. So, the data itself is not subject to change, only the cartography and the web medium.
Special thanks to Michael Dangermond for providing the post. Questions for Michael: MDangermond@esri.com.
In last week’s post, Creating and Animating Water Level Maps with Arc Hydro Groundwater – Part 1, we showed how to automate the process of creating and animating water level maps using a combination of standard ArcGIS tools and a few of the Arc Hydro Groundwater (AHGW) tools. We also provided an animation of water levels for the Edwards Aquifer in Texas. One of the interesting features of this animation is the animated water levels shown along a cross section of the aquifer.
In today’s post we will cover how the cross section was created and water levels added to it.
Step 1 – Create a new section line
The first step in the process is to sketch a cross section of interest. We store the cross section in the SectionLine feature class (part of the AHGW data model) and give it a unique identifier and name (the unique identifier of the section line will later be used to reference any cross section features related to the section). Also, a vertical exaggeration is assigned to the section line (in this case a value of 20 was used); this value will be used to vertically scale features when creating the cross section. The following figure shows section line A-A’ sketched from East to West across the Edwards Aquifer boundary. A set of wells with hydrostratigraphy data are also shown. Data from these wells will be added to the cross section.
Section Line A-A’ and wells with hydrostratigraphy information. Notice the HydroID (unique identifier), SName (section name), and vertical exaggeration attributes assigned to the section line.
Step 2 – Borehole information
Borehole hydrostratigraphy data was imported into the BoreholeLog table. This table stores vertical borehole data, in this case data describing the hydrogeologic units along the bores. Each item in the table represents an interval along a borehole. The WellID references a Well feature which gives the XY location and the TopElev and BottomElev give the vertical dimension of the interval. Material, HGUID, and HGUCode provide descriptive information of the strata and the hydrogeologic units.
BoreholeLog table for storing vertical information along boreholes.
Step 3 – Creating a new cross section data frame and feature classes
Using the XS2D Wizard available as part of the AHGW tools, we created a new data frame and a set of feature classes for displaying information along section A-A’. The new feature classes that were created include (notice that all cross section feature classes get a XS2D prefix to indicate they are part of a cross section) features representing grid lines, panel dividers, and borehole stratigraphy.
We also used the Transform Raster To XS2D Line tool available in Subsurface Analyst to add a line representing the surface terrain from a DEM.
Data frame for representing cross section A-A’. Red lines represent panel dividers (point along a section line where the cross section changes direction), the colored thick lines represent hydrostratigraphy at bores along the cross section, and the brown line represents the land surface.
Step 4 – Adding water levels to the cross section
In Part 1, we demonstrated how to create and animate a set of rasters representing the water levels at different time periods. To add water levels from the rasters to the cross section we batch processed the Transform Raster To XS2D Line tool.
- takes as input SectionLine features and raster datasets,
- reads values from the raster along the section lines at a specified sampling distance,
- and then applies a transformation such that the raster data can be displayed in the cross section data frame.
Lines representing water levels along the cross section were derived using the Transform Raster To XS2D Line tool.
The result is a set of line features that represent the raster data. In our case each line represents the interpolated water levels for a given time period. We added a Tstime field to the output line features and added a time stamp so the water level lines can be animated over time in coordination with other datasets (points, rasters, and contours) in the plan view data frame. The following figure shows the derived water level lines for all time steps displayed in the cross section data frame.
Line features representing the water table at different times. The lines can be animated in coordination with other datasets describing water levels (points, rasters, and contours).
If you haven’t see the final animation yet, take a look at the final result.
One of the common mapping tasks in groundwater projects is creating water level maps. In many cases, a set of maps is created to show the changes in water levels over time. Using the ArcHydro Groundwater (AHGW) tools it’s easy to automate the process of creating water level maps in ArcGIS. Last year, at the American Water Resources Association (AWRA) Spring Specialty Conference we (Aquaveo) showed a demo of creating and animating water level maps using a test case of the Edwards Aquifer in Central Texas. We got a number of inquiries from users about this process and how they can implement it with their data. So, in this post we will cover the main steps in a workflow for creating water level maps and animating them.
Here are the steps we followed to create the animation:
Step 1 – Summarize water levels
Water level measurements taken at wells were summarized over a given time period (for example, to calculate the average water level for a given month). The summary values are related to a map location (usually by adding the X and Y coordinates of a well) to create a new set of points holding the summarized time series.
To automate this process, we used the Make Time Series Statistics tool available as part of the AHGW tools. The tool inputs include a set of well features and related water level measurements stored in a table. The output from this tool is a set of point features with an attribute representing the calculated statistic (e.g. average water level).
On the left, a set of wells and related water level measurements. On the right, averaged water levels for the winter 1990 period. The average values were derived using the Make Time Series Statistics tool available as part of the AHGW tools.
Step 2 – Interpolate to create water level surfaces
In this example we used the Inverse Distance Weighted (IDW) tool in the Spatial Analyst toolbox, but you will need to define the interpolation method for your project. We also loaded the created raster into a Raster Catalog so it can be indexed with the time stamp (this enables us later to easily animate the rasters in sync with other datasets). To automate the process of loading and indexing the rasters into a Raster Catalog we used the Add to Raster Series tool, available as part of the AHGW tools.
Water level rasters are created by interpolating the summary statistics created in Step 1. The rasters created are loaded into a Raster Catalog and indexed with the appropriate time stamp using the Add to Raster Series tool.
Step 3 – Derive Contours
Water level contours derived from the rasters using the Create Contour tool.
Step 4 – Create a single feature class for water level points and contours
In order to animate all the datasets (points, rasters, and contours) it is easier to create a single feature class for each data type. This was a two step process:
- Add a TsTime field to the points and contour feature classes and populate this field with the appropriate date for the feature class. For example, points and contours representing the winter of 1990 were given a TsTime = 1/1/1990. You can batch process the Add Field and Calculate Field tools to streamline this task.
- Use the Append tool to upload points and contours into one feature class (one for contours and one for points).
Step 5 – Animate
Once we have all the datasets prepared, it is easy to animate the maps. We used the Animation toolbar, so we are able to animate two data frames at once (notice the animated cross section is in a second data frame). if you are
only animating one data frame you can use the Time Slider Window available in ArcGIS 10. Here are the main steps in setting up the animation:
- Go to each layer you want to animate (points, contours, raster catalog) and enable time for that layer. Set the appropriate Time Field and the Time Stamp Interval.
Setting the layer properties to enable time.
- In the Animation toolbar, select Animation > Create Time Animation. This will create a new Time Animation Track. You should get a message that confirms that a new track was created.
Creating a new Time Animation track.
- Repeat steps 1 and 2 for any other data frame you want to animate. In our example we have a cross section on which we animate water level changes along the cross section.
At the end of this process we have two animation tracks, one for each data frame, which can be animated simultaneously. You can open the Time View tab to see the tracks and use the slider within the time view to animate the map.
Multiple animation tracks viewed in the Animation Manager.
You can now use the animation controls to show the change in water levels over time.
Using Model Builder it is easy to automate the process presented in Steps 1-3. We put together a model that runs the Make Time Series Statistics, IDW, Create Contour, and Add to Raster Series tools in one step. This will enable you to quickly process your data and also document your workflow. While constructing the model you might consider defining Environment Settings such as the Extent and Mask for the raster analysis.
Model to automate the creation of water level maps.
The animation shown includes a cross section data frame with lines representing the water levels along the cross section. In our next post (Part 2) we will show how the cross section was created and water level lines added to it.
Esri has web-enabled four soil maps of the United States based upon the NRCS SSURGO dataset. They will be served directly to the ArcGIS system, and their content nodes may be retrieved from arcgis.com or within arcmap itself in version 10. The first maps to be enabled will be from the MUAGGATT attribute table provided in the NRCS SSURGO dataset encapsulating their recommended map unit aggregations. All SSURGO based web maps are enormous in size, they cover the entire United States at once at the planning scale of 1:24:000. At the moment they are being served by the amazon cloud where they may be used in your maps and applications immediately.
The four soil maps are:
In this web map, infiltration rates are grouped into some very broad class estimates. You may use dominant hydrologic group as a basic input to estimate runoff potential in a watershed. A full explanation of the hydrologic group codes may be found on its arcgis.com service page.
This web map indicates some very basic facts about the presence of hydric soils in a soil map unit, whether the soil map unit is made up of all hydric or part hydric soils, or if the map unit is not made of hydric soils at all.
These web maps show drainage class for each soil map unit. There are two drainage class maps based upon two methods of computing the class. The first method shows drainage class by the wettest soil component in the soil map unit, and the second shows drainage class by the most dominant component in each map unit. You may want to use one or the other in modeling depending on what you are trying to simulate in your model.
These soil maps are only the beginning for Esri. Stay tuned to the mapping center and the hydro blog for more hydro related soil maps which will probe deeper into the SSURGO datasets with increasing sophistication.
Special thanks to Michael Dangermond for providing the post. Questions for Michael: MDangermond@esri.com