Assessing Residential Water Supply Demand Changes
for the City of Long Beach Under Climate Change Scenarios
City of Long Beach Climate Resiliency AssessmentLoyola Marymount
UniversityJeremy S. Pal
Brianna R. PaganChengyu Gao
March 2016
Introduction• Part of City of Long Beach Climate Resiliency
Assessment Report• Proposed by Mayor Robert Garcia in his January 2015
State of the City address• This study focuses on:• Local water demand changes• Residential irrigation• Drought analysis in the past and future
• Time frame: 1966-2005, 2011-2050
Population Changes•Population growth from census data:•0.01% growth from 2000 to 2010•0.46% growth from 2010 to 2015
•Average change of 0.16% is used for population projection
2015 2020 2025 2030 2035 2040 2045 2050455,000
460,000
465,000
470,000
475,000
480,000
485,000
490,000
495,000
500,000
505,000
Long Beach City Population Growth vs. Year
Year
Popu
latio
n
Outdoor Irrigation Demand Quantification• Basic Model – runoff calculation
• Data Sources:• California Irrigation Management Information System (CIMIS)
(1990-2015)• Ten coupled atmosphere-ocean global climate models
(GCMs) (1966-2005)• Projection:• Representative Concentration Pathway 8.5 (RCP 8.5) (2011-2
050)• Parameters:• Precipitation, evaporation, temperature
Residential Landscape Area Estimate• Residential homes are broken into three categories:• Single Family Homes• Duplexes• Multiple Family Homes
• Geographic Information System (GIS) is used to find the total parcel area of residential homes• Zoning data dictionary is provided by the Long Beach city
website• Residential landscape area is estimated by random
sampling of 100 homes
Single-Family Homes
Duplexes Multiple-Family Homes
Total Parcel Area (ft2) 400,000,000 65,000,000 83,000,000Number of Parcels 56,000 10,000 6,300
Average Parcel Area (ft2) 7,300 6,200 13,000Average Landscape Size
(ft2)2,100 2,000 1,600
Fraction of Landscape Area to Average Parcel
Area
28.4% 31.7% 8.5%
Total Rooftop Area (ft2) 120,000,000 26,000,000 28,000,000Number of Rooftops 72,000 15,000 10,000
Finalizing Quantification• Model Correction include parameters below:• Crop Coefficient (Kc)• Effective Evapotranspiration (ET0)• Effective Precipitation (Pe)• Storm Water Capture (SWC)
• Corrections return effective runoff (Runoffe)• The annual residential irrigation demand (ID):
Total Demand Change Estimate• Water consumption of Long Beach in 2014:• 112 gallons per capita per day (GPCD)
• After city’s water conservation effort, it is estimated that the water consumption will likely be reduced to 100 GPCD• Water consumption will be fixed at 100 GPCD in the
projected period of 2030-2050• Population growth is incorporated in the projection
Conclusion• Further reduction beyond Long Beach Water
Department’s (LBWD) 100 GPCD goal will be difficult to achieve• Population growth has the potential to exceed further
GPCD reduction, resulting a net increase in water usage• Storm water capture (i.e. equipping rain barrels with
residents) will not significantly impact water demand• Large scale drought tolerant conversions could save
Long Beach an additional 2030 acre-feet per year under a warmer climate
Top Related