Water-Energy Balance in an Arid Climate

Understanding the link between water and energy use.

Climate change and population growth has made tenuous the sustainability and security of urban water supply across the globe. Traditional urban planning has tended to look at water and energy as independent of one another, today however, cities in arid regions look to great distances to secure enough water to support their expanding growth.  When one considers that movement and distribution of water across expansive ranges is dependent upon low-cost energy and that large volumes of water are required in power generation, then it is clear these two resources are unmistakably linked. These issues call attention to critical tradeoffs associated with managing water in complex urban systems.

Choosing to alleviate rising temperatures solely through energy-intensive means only quickens the rate at which temperatures rise.  In the arid southwest and arid cities throughout the world we must learn to manage the compromise between cooling with irrigated surface and securing the water that enables such interventions.

Direct solar radiation falling on the vertical facade of a typical building causes a warming of the environment as some of this heat is then reflected into and then trapped underneath the surrounding canopy layer.  A proposed building form composed of terraced green decks reduces solar radiation while enhance environmental cooling through evapotranspiration.  This building model breaks up the horizontal plane at roof level influencing air flow characteristics in a way that enhances air exchange.

The compact form promotes a more efficient use of land and resources and decreases automobile dependences through a mixed-use neighborhood close to multiple alternative transportation options

Phoenix_watercolor

In arid regions, such as Phoenix, concerns over the impact of climate change on availale water resources means that the allocation and management of water is one of the largest considerations in developing landscape amenities.  Changes in the structure of the natural and built environment have created environmental disparity between neighborhoods with respect to the degree of services they provide, so that families living near lush irrigated lawns and abundantly vegetated parks receive more services than those located farther away.

Efforts to increase vegetative cover should focus on localities with the least amount of plant cover, where more appreciable gains in cooling can be achieved with minimal additional water input.  Furthermore, we must plan our cites to reduce vulnerability to extreme drought by breaking our reliance on carbon based transportation options and reduce factors that compound Urban Heat Island effect such as low density sprawl.

There exists a correlation between low-density patterns of land use and enhanced surface temperatures in cities suggesting that urban sprawl could be a significant contributing factor to the increase and intensity of heat waves in cities.  A 2010 study revealed that the rate of increase in extreme heat events is higher in sprawling than in more compact metropolitan regions and found this association true independent of climate zone, metropolitan size or rate of growth (Stone et al. 2010). These findings challenge earlier assumptions that density itself is a leading cause of urban heat island and lead to a more complex understanding of how urban forms and urban configurations influence heat gains within the urban environment.

A proposed network of canopied, pedestrian-only routes in the narrow alleys between buildins (shown above in blue) helps to foster a a reduced dependency on personal automobile transportation.  These pedestrian walks will act as links between larger alternative transportation options such as the city metro and rapid transit lines (shown above in color).

Advertisements

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Google+ photo

You are commenting using your Google+ account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

w

Connecting to %s