Mapping the Rio Grande Basin
New management tool aids irrigation districts
By Danielle Supercinski
GIS-based maps of 30 Rio Grande Basin irrigation districts in Texas completed during the spring 2005, will serve as an indispensable tool for planning future projects and managing districts’ day-to-day operations.
Quality paper maps are just one of the byproducts of the of the GIS efforts.
“We began the (GIS-based) mapping effort as part of a regional water planning study to determine potential water savings that result from district modernization and rehabilitation,” said Guy Fipps, Extension agricultural engineer and director of the Irrigation Technology Center. “These maps allowed us to extrapolate water savings test results from a small number of canals to the entire region, and to produce reasonable estimates of water savings.”
It took years to assemble the basic attribute data (canal sizes and conditions, for example) on the water distribution networks needed to produce these maps. This information is currently helping districts to decide which canal segments are in need of rehabilitation or have high water loss, and are suitable for replacement with a combination of synthetic liners and pipelines.
“These maps are indispensable for this purpose,” Fipps said. “The districts estimate that to date these projects have saved about 50,000 acre-feet per year of water that otherwise would have been lost, with many more rehabilitation projects to be done.”
Features that are displayed on these maps include: district boundaries, canals that are colored by lined or unlined, pipelines, siphons, reservoirs, resacas, river pumping stations, district to district diversion points, roads, and aerial photographs. Some maps also include the Rio Grande River and Arroyo Colorado systems.
Irrigation districts also use these maps to determine exact “water account” of field boundaries and areas, and for the formal process of excluding land from the district as it urbanizes.
“In recent years, more districts have been using the GIS and maps for day-to-day management decisions, maintenance scheduling, on-farm water delivery strategies and optimization, and for rehabilitation planning,” Fipps said. “We have also implemented a technical training and assistance program for districts to develop their own ‘in-house’ capabilities to update the maps in the future.”
The general public may even have an interest in these maps to determine exact locations of district facilities and to see how these may impact their property. Many organizations, including environmental and wildlife interests, use these maps as part of their conservation and public education programs.
A lot of steps are involved in creating such useful maps.
Irrigation district maps, such as this Hidalgo County map, can be obtained for 30 Rio Grande counties displaying district boundaries, lined and unlined canals, pipelines, reservoirs, and resacas, to name a few.
The first step required assistance from the irrigation districts to locate old paper maps that could be used as a beginning guide. Aerial photographs of districts became the basis of all maps produced. These aerial photographs were developed by the U.S. Geological Survey and have resolutions of about one meter and exact locations of canals and other features are clearly visible, Fipps said. Then, in many cases, field inspections and explorations were conducted using GPS surveying equipment to verify the locations.
“Since the GIS mapping began it has allowed us to study districts in ways that would have been impossible without the GIS,” said Eric Leigh, Extension Associate in biological and agricultural engineering. “The GIS maps are not only lines on a sheet of paper, but a wealth of information, storing any and all attributes for each section in a database.”
There are two specific GIS components that were useful for this purpose.
“One allows you to actually draw the map,” Fipps said. “The difference between GIS and other drawing software, such as AutoCAD, is that each point on the GIS corresponds to the exact location expressed in latitude and longitudinal coordinates. Thus, this map or ‘layer’ can be combined with any other layers.”
For example, roads in Texas are available in GIS, which can then be combined with these district maps.
“The second feature of GIS that is useful is being able to link ‘attribute’ data with other map features and display these when printing out the map or making a map image,” Fipps said.
The mapping of irrigation districts began in 1996 as part of the GIS development program. This is the fourth major map release completed since 1998.
These irrigation district maps can be ordered online using the order form posted on the IDEA Web site at http://idea.tamu.edu/gismaps.php. There are several options to choose from, including the district, type of paper and size. Custom maps are another option. Districts with GIS capabilities can receive a copy of the shape files at no charge. A pdf version is also available.
Three sets of additional maps have been published and can be found on the IDEA Web site as well. These maps include U.S. Congressional District Maps, Municipal Water Supply Network of districts and regional scale maps.
Current project staff includes Guy Fipps, Eric Leigh, David Flahive and Askar Karimov. Funding for the mapping has been provided through the Efficient Irrigation for Water Conservation in the Rio Grande Basin project for the past 5 years.
Photos courtesy of Guy Fipps, Eric Leigh and Askar Karimov
