Using free online PAG mapping tool to see tree canopy, water flow, and more in your neighborhood

My community of Tucson, Arizona just experienced the hottest August on record.

Tucson is also the third fastest warming city in the U.S.. Such warming is happening around the world due to the local heat-island effect and global climate change. But we can help address both by growing carbon-sequestering air conditioners in the form of multi-use native vegetation that can reduce urban temperatures by over 10˚ F degrees in its shade.

The more we harvest, rather than drain, rainwater and stormwater to freely irrigate that vegetation; the larger and healthier it grows, resulting in magnified cooling. This cooling is not just from shade, but is also due to the evaporative cooling effect of the transpiring vegetation. Thus, the more we can hold on to rain when it falls (within water-harvesting earthworks or rain gardens), and extend its availability long into the hot, dry times—the more powerful the cooling effect of the associated vegetation.

Mapping tools can quickly show us stormwater flows, where we are doing well with vegetation, where we can do better, and the result of efforts over time.

The following describes a Pima Association of Governments (PAG) mapping tool that is only for Pima County, Arizona. But other counties and municipalities may have similar mapping tools.

1. Online go to the PAG Green Infrastructure Prioritization Tool map ( and plug in your address. Then expand the view to include your entire neighborhood.
If the map is not working for you, try viewing it on a different web browser.

2. Click on/open the Legend (lower left corner of screen). Once the legend is open, click on/choose the boxes for the following layers to be added to the map (figure 1):

• Drainage Pathways – then its Flowline sub-box

• Percent Tree Canopy Cover by Census Block

• Washes 

This image shows my neighborhood Dunbar/Spring in the center, the red dot signifies my property at the NW corner of 9th Ave and University Blvd. Speedway Blvd is near the top of the image, I-10 highway to the left. The varying degrees of green signify different percentages of tree cover by block (data is from the year 2008, so we need new data to see how we are doing presently-and see if we are improving or getting worse compared to past data). In 2008 tree cover on my block was 22%. Better than some, but we could do a lot better (thus we keep planting more stormwater, trees, and understory plants). Blue signifies waterways, drainages.

3. Within the legend, click on the Regional Surface Temperature layer

This will show you the hotter and cooler areas based on year 2008 data.

The more yellow to orange—the hotter the temperatures.

The more green to blue—the lower the temperatures.

Here you can see that I also turned on the Regional Surface Temperature layer—again the data is from 2008. The more yellow to orange—the hotter the area. The more green to blue—the cooler the area. It is much hotter where tree cover is lacking. Thus we can see where we need to focus more plantings and we’d also benefit from a reduction in hardscape such as pavement.


Here I zoomed in for a closer look at my part of the neighborhood. In this view the Regional Surface Temperature layer is off.

In this zoomed in view the Regional Surface Temperature layer is on. Again, see how areas with fewer trees are much hotter (more yellow in color).

4. Within the legend, click on the Regional Land Use Land Cover layer

This will show you various hardscapes from which stormwater runs off, vegetated areas that could harvest that runoff, and unpaved areas that could be planted with stormwater and vegetation.

In this view, the Regional Land Use Land Cover layer is on. Hardscapes from which water runs off are highlighted: buildings in pinkish red, roads in dark grey, impervious pavement such as sidewalks and asphalt parking lots in grey. Vegetation is highlighted in green. We have some areas with good vegetative cover. Other areas in yellow or orange are unpaved and lacking in vegetation. Plenty more planting can be done – even in the parking lots and such.

5. Take a screen shots of the map for your records..
On my Mac computer I do this by pressing the Command, Shift, and “4” keys simultaneously. A plus symbol then appears on my screen. With my mouse or trackpad, I move the plus symbol to the perimeter of the area I want to capture in the screenshot. I then click and hold, a rectangle appears which I can expand or shrink as I move my cursor.  When I release the click on my mouse or trackpad, the screen shot is taken.

6. Request PAG to fund and upload Percent Tree Canopy Cover data and Regional Surface Temperature data at least every ten years to the mapping tool.
Since the data currently available on the mapping tool is from 2008, it would be great to have updates at least every 10 years to be able to compare, see how we are doing, and the effects of ongoing work.