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Irrigation in the West, visualized with National Hydrography Dataset

· 3 min read
Alex G Rice
Alex G Rice
Geodata rambler and developer, aka guidorice

In the United States there is a clear pattern of human settlement where to the East, there is more than 30 inches of rainfall and so crops can be grown without irrigation, and to the West, irrigation is required. This post is an exploration of population density, precipitation rates, and the National Hydrography Dataset (NHD)...

Average annual precipitation​

us precipitation inches
Attribution: United States Department of the Interior nepes, Public domain, via Wikimedia Commons

Population density​

I added the blue dotted line to hilite the pattern going from Wisconsin down to Texas.

us population density
Attribution: SEDACMaps, The Trustees of Columbia University in the City of New York: CC BY 4.0 , via Wikimedia Commons

Acequias, canals, and ditches in the West​

In the West, human settlements were only possible where water exists and agriculture was possible. Acequias, irrigation ditches and canals are the technology that makes this possible.

An acequia is a community-operated watercourse used in Spain and former Spanish colonies in the Americas for irrigation. Acequias are found in parts of Spain, the Andes, northern Mexico, and the modern-day American Southwest (northern New Mexico and southern Colorado). source: Wikipedia.

Visualize irrigation with the NHD​

Here are some screen captures of the Southwest US and also the Grand Valley in Colorado. The patterns of irrigation development are correlated with the population density map (above).

Southwest US irrigation​

Southwest us
Map data sourced from the National Hydrography Dataset (NHD), U.S. Geological Survey, ©OpenStreetMap contributors

Grand Valley, Colorado irrigation​

Grand valley CO
Map data sourced from the National Hydrography Dataset (NHD), U.S. Geological Survey, ©OpenStreetMap contributors

Technical approach​

  1. Researched the NHD and found download options

  2. Downloaded with curl and unzipped the national NHD file

curl -O https://prd-tnm.s3.amazonaws.com/StagedProducts/Hydrography/NHDPlusHR/National/GDB/NHDPlus_H_National_Release_1_GDB.zip
unzip NHDPlus_H_National_Release_1_GDB.zip

Contained in the zip archive is a 99GB geopackage file: NHD_H_National_GPKG.gpkg.

  1. Explored the features and attributes in QGIS. The dataset has many layers and feature codes. For this quick exploration, I focused on the layer NHDFlowLine and the feature code 33600:"Canal/Ditch".

  2. Used GDAL/OGR to efficiently filter on the fcode attribute, producing a new geopackage file: canal-ditch.gpkg.

ogr2ogr canal-ditch.gpkg NHD_H_National_GPKG.gpkg \
    -sql "SELECT * FROM NHDFlowline WHERE fcode = 33600"
  1. In a new QGIS project, add an OpenStreetMap XYZ Tiles layer, and the canal-ditch.gpkg geopackage.

I hope you enjoyed this ramble through a population map, precipitation map, and finally the NHD dataset.

edits
  • 2024-09-21 Fix attribution for population density map