STATSGO2-soil data

Step 1: Get soil data

Download state data from here: [1]

Download county or survey level data from here: [2]

Both sources should include a) tabular data b) spatial data c) Microsoft Access template

State data is spatially coarser than county or survey level data

Step 2: Install Soil Data Viewer

You need 1) Install ArcGIS 9.2 or later for soil data viewer 5.2 on a Windows XP system 2) Install soil data viewer version 5.2 [3]

Step 3: Prepare Access database

1) Open Access template 2) Enable macros 3) Type in full path name to tabular data 4) Import should run automatically

Step 4: Working with Soil Data Viewer in ArcGIS

1) Open ArcGIS - View > Toolbars > Soil Data Viewer Tools 2) Click on the Soil Data Viewer button 3) Browse to Access database 4) Choose the soil data layer to connect to the database

Soil data viewer online user guide is here: [4]

Step 5: Karl's method for estimating soil properties using SDV

Definitions:

a) Dominant Condition (DCD)

b) Dominant Component (DCP)

c) Weighted Average (WA)

d) All Layers (ACP)

1) Soil Physical Properties: Surface Texture

Useful for a) naming the soil .def file b) understanding depth to soil restrictive layer c) understanding ksat at surface

2) Soil Qualities and Features: Depth to Any Restrictive Layer

a) Generate Depth DCD, DCP, WA, ACP using both < and > for tie break rule with no cutoff (8 scenarios)

b) Compare these to summer Landsat imagery and use expert judgment to determine the most accurate layer

c) Depth To Any Restrictive Layer results for Silver Fork

• ACP, > 127,143,153 - not much spatial variability, bedrock not represented
• ACP, < 0 - basically junk
• WA - tie break doesn't matter, 17 for texture un-weathered bedrock
• DCP - tie break doesn't matter, very shallow in upper basin
• DCD, > zeros where surface texture is bedrock, 77,127,201
• DCD, < zeros where surface texture is bedrock, 77,127,201 but shallower than DCD, > (obviously)

3) Soil Physical Properties: Saturated Hydraulic Conductivity (RHESSys requires Ksat at surface and decay with depth)

a) Generate Depth DCD, DCP, WA, ACP for ALL LAYERS using both slowest and fastest for tie break rule with no cutoff (8 scenarios)

b) All Layers Ksat results for American Silver Fork

• DCD - tie break doesn't matter, portions with surface texture bedrock have no data. Range is 91 um/s, 29 um/s 18 um/s
• DCP - tie break doesn't matter, large portions of upper basin have no data. Range is 91 um/s to 28 um/s for lower
• WA - tie break doesn't matter, Ksat is 60 um/s in upper basin and 26 um/s in lower basin. More spatial variability than ACP >
• ACP < - Ksat is too slow
• ACP > - Ksat is 91 um/s in upper basin and 28 um/s in lower basin. Less spatial variability than WA

c) 50 cm layer results for American Silver Fork (note 50cm increment chosen from b above - coarser might be appropriate for lower basin)

4) Soil Physical Properties: %Clay,%Sand,%Silt (used in RHESSys only for carbon cycling)

a) Focus is not on carbon cycling - simplify and use WA, lower and upper were the same for all 3 variable Clay - range is 2.7% to 12.7% Sand - range is 66.3% to 80.4% Silt - range is 15.9% to 24.1%