Task

• Delineate the watershed boundaries of the eight ARS gauged watersheds on the SRER.

Study area

Locations of the eight gaged watersheds relative to the Eddy Covariance Flux Towers and the PAG 2011 LiDAR township and range section tiles.

Methods

• Located watersheds using shape files for gage locations from the Santa Rita Experimental Range GIS archive.
  

  • Loaded PAG 2011 LiDAR township and range section tiles as a .KMZ to also help identify location (see embedded Google.Map above).

  Use the 2011 PAG aerial LiDAR data over the watersheds to generate bare earth surface models
• Compare outputs from AGWA (ArcGIS) and SAGA-GIS.
• Created text scripts for the *.LAS tiles:

Lower
D:\SRER\PAG_2011\LAS\18S14E15_LDRY11.las
D:\SRER\PAG_2011\LAS\18S14E16_LDRY11.las
D:\SRER\PAG_2011\LAS\18S14E21_LDRY11.las
D:\SRER\PAG_2011\LAS\18S14E22_LDRY11.las
Upper
D:\SRER\PAG_2011\LAS\18S15E31_LDRY11.las
D:\SRER\PAG_2011\LAS\18S15E36_LDRY11.las
D:\SRER\PAG_2011\LAS\19S14E01_LDRY11.las
D:\SRER\PAG_2011\LAS\19S15E06_LDRY11.las

• In USFS FUSION (McGaughey 2013) I merged the LAS files into a single tile to reduce the likelihood of seam lines

  • LAS uses class = 2 for Bare Earth surface models, so I use a switch to only use those points:

MergeData /index /class:2 D:\SRER\PAG_2011\LAS\upper.txt D:\SRER\PAG_2011\LAS\upper.las
MergeData /index /class:2 D:\SRER\PAG_2011\LAS\lower.txt D:\SRER\PAG_2011\LAS\lower.las

• I then batch scripted the GridSurfaceCreate command to generate bare earth layers for all the PAG 2005, 2008, and 2011 LiDAR tiles (*.LAS) using classified bare-earth returns (class = 2) only. 

GridSurfaceCreate /median:3 /smooth:3 /minimum D:\SRER\PAG_2011\upper.dtm 2 f f 2 0 2 2 D:\SRER\PAG_2011\LAS\upper.las
DTM2ASCII D:\SRER\PAG_2011\upper.dtm
GridSurfaceCreate /median:3 /smooth:3 /minimum D:\SRER\PAG_2011\lower.dtm 2 f f 2 0 2 2 D:\SRER\PAG_2011\LAS\lower.las

D:\SRER\PAG_2011\lower.dtm

Complete description of the GridSurfaceCreate parameters are given in the FUSION manual. Previously, I compared surfaces produced at 2 feet that were re-sampled to 9.8425 feet or 3 meter resolution (using the MergeDTM command). I found the 3x3 nearest neighbor median and smooth switch caused blurring of erosion and deposition edges along stream channels. The 2ft merged to 9.8425ft surface did not have this issue because the 3x3 filter ran on a 6x6 foot area retained higher definition edges. 

Watershed delineation in AGWA

Following the standard AGWA procedure I delineated the upper and lower watersheds. 

1. Load DEM (in UTM coordinates) into ArcGIS
2. Save Project MXD
3. Open AGWA Tools
4. Set AWGA working directory
   1. AGWA Tools > Other Options > AGWA Preferences
   2. Set Home Directory, Temporary Files, and Workspace
5. Delineate Watersheds
   1. AGWA Tools > Delineation Options > Delineate Watersheds

Watershed_5.kmz

Watershed_6.kmz

Watershed_7.kmz

Watershed_8.kmz

channels_6.kmz

channels_7_8.kmz

Watershed delineation in SAGA

Loaded ASC file into SAGA-GIS using the Import/Export GDAL: Import Raster function (GDAL File formats)

Ran Terrain Analysis - Preprocessing: Fill Sinks (Wang & Liu 2006), default parameter settings.

Alternative method: Planchon, O. & F. Darboux (2001): A fast, simple and versatile algorithm to fill the depressions of digital elevation models. Catena 46: 159-176.

Ran Catchment Area (Mass-Flux Method)

Ran SAGA Wetness Index

Ran Terrain Analysis - Channels: Strahler Order

 Ran SAGA Basic Terrain Analysis

The outputs of the Basic Terrain Analysis include:

• After the bare earth layer was created as an ASC it was loaded into QGIS 10.1 w/ GRASS 6.4.3.
• Created a color hillshade relief using QGIS Raster>Topography>Relief 
• The units were converted to meters using the Raster Calculator function in QGIS.
• The Projection for the PAG LiDAR data is in either ESPG:2223 or ESPG:102649

• The layer was then reprojected into UTM coordinates in QGIS using a GDAL Warp command:

  gdalwarp -overwrite -s_srs EPSG:2223 -t_srs EPSG:2956 -tr 3 3 -r bilinear -of GTiff I:/SAGU/DEM/3m/rincon_crk_3m_stpln.tif J:/SAGU/DEM/3m/rincon_crk_3m_utm.tif

• NOTE: Setup LASTools in QGIS: http://rapidlasso.com/2014/05/23/first-ever-lidar-processing-model-in-qgis/

References

Wang, L. & H. Liu (2006): An efficient method for identifying and filling surface depressions in digital elevation models for hydrologic analysis and modelling. International Journal of Geographical Information Science, Vol. 20, No. 2: 193-213.

Example from Vivoni et al. 2014 of guaged watersheds on the SRER