Land use connections to demand management

Heejun ChangDepartment of GeographyPortland State University

April 9, 2019

Urban Water Demand Roundtable, Phoenix

Objectives

• Identify how land use change is associated with single family residential (SFR) water demand

• Assess landscape and sociodemographic factors affecting SFR water use change at the census block group scale

• Compare aspatial and spatial model performance for explaining the variation in SFR water use

Population growth in the PDX metro area

Source: New Geography

Study area: Portland

Sociodemography

Factors affecting residential water use

Land cover

% vegetation% developed areas

Water use

New areas builtBldg densityProperty value

Building

IncomeEducationEthnic group

New SFR lots developed, 2005-2011

New SFR lots developed per CBG

Change in SFR water use, 2005-2011

Δ Average bldg. Area % Forest Area

Δ in Hispanic pop Δ in Income

Comparison of OLS with spatial regression

y = β0 + Xβ + ε ε = λWε + ξ

ε = random error termλ = autoregressive coefficientW = spatial weight matrixξ = white noise

Xi

Xj

Yi

Yj

ei

ej

Explanatory variable OLS Spatial

Δ Total bldg. Area 1.93* -0.01

Δ Average bldg. Area -2.14** -1.80*

% Forest in 2011 -3.30*** -2.16**

% Low density develop 4.38*** 2.99***

Δ Hispanic population 5.81*** 3.57***

Δ Income -2.38** -0.82

R2 0.21 0.53

*Statistically significant at the 10% level

**Statistically significant at the 5% level

***Statistically significant at the 5% level

Conclusions• Increasing new larger, low density SFR development is

associated with increasing water demand.

• Higher proportion of green space in the neighborhood is negatively related to increasing SFR water demand.

• Change in ethnic group and income further explain the variation of additional SFR water demand.

• Considering spatial dependence improves the power of explaining variations in SFR water demand change.

Acknowledgements

Hossein Parandvash & Emma Brenneman

Queations??? Contact Heejun Chang changh@pdx.edu