The urban heat commons: vegetation cooling services in Metropolitan Phoenix

Resource System
Watershed and associated topography
Resource Units
Vegetation, including trees and grasses
Location
Metropolitan Phoenix

The case of urban vegetation cooling service at Metropolitan Phoenix, Arizona, USA is an addition to the original Common-Pool Resource (CPR) database. This case was created in 2013 by Yujia Zhang at Arizona State University. Metropolitan Phoenix is one of the fastest growing regions in the southwest U.S. In contrast to its rapid urban expansion, this area possesses inadequate natural resources and faces unique challenges of sustainable development. The commons dilemma in this case is to balance the tradeoffs between heat mitigation and water consumption by optimal design and efficient irrigation of urban green space. 

Urban vegetation cooling service at Metropolitan Phoenix
Resource System

The vegetation cooling service provided by urban public and private green space. e.g. parks, golf course, residential yards, etc.

Water for irrigation to maintain the green space.The Phoenix region has four primary sources of water:
1.local rivers in the Salt-Verde watersheds,
2.water from the Colorado River,
3.groundwater of Phoenix active management area,
4.effluent.

Resource Users

Residents of the Metropolitan Phoenix region, nearly 4 million in year 2010.

Public Infrastructure Providers

PIP of urban green space:
Various government agencies at multiple levels: Arizona Community Tree Council, Arizona State Forestry Division, Arizona Department of Water Resources, The Maricopa Association of Governments, city councils, city department of parks and recreation. In addition, commercial property owners, building developers,Homeowner’s Associations (HOAs), and individual homeowner.

PIP of water supply, deliver and treatment:
Over 100 public and private providers deliver water to customers. Major public agencies are the Salt River Project, Central Arizona Project, and the Arizona Department of Water Resources.

Public Infrastructure

Urban public and private green space

PI of water: A network of eight canals totaling 2092 km, with connections to above ground ditches and underground pipes for direct irrigation purposes and for potable uses through treatment plants. There are in total 97 water treatment plants.

Relationship 1

Socioeconomic status affect resident's access to vegetation cooling service.

Relationship 2

Water authorities offer financial incentives to home owner who convert lawn to xeriscaping.

Relationship 3

Government agencies are responsible for planting, maintenance and irrigation of vegetation in public green space. They also set regulations and rules to monitor the usage of public green space.
Private and commercial land owners are responsible for planting, maintenance and irrigation of private green space according to the corresponding standards.

Relationship 4

Trees can lower temperature more effectively than turf grass.
Conversion from lawn and oasis to xeriscaping, adoption of water efficiency technologies converse water.
Outdated appliances and infrastructure increase water loss.

Relationship 5
(none specified)
Relationship 6

At present, resource user only pay part of the water infrastructure cost. The rest is paid by federal or state tax funds.

Exogenous Drivers 7 (Resource System)

Future drought and uncertainty on climate change may cause severe water shortage and elevate the temperature of this region.

Exogenous Drivers 7 (Public Infrastructure)
(none specified)
Exogenous Drivers 8 (Resource Users)

Rapid population growth will increase municipal water demand and cause urban expansion. Urban expansion may aggravate the magnitude and intensity of urban heat island.

Exogenous Drivers 8 (Public Infrastructure Providers)
(none specified)
Human Infrastructure, Private and Human-Made (Resource Users)
(none specified)
Human Infrastructure, Private and Human-Made (Public Infrastructure Providers)
(none specified)