Water Resources in San Diego County

Columbia Water Center’s Aquanaut research interns collected data on water usage for San Diego County from 1949 through 2013 to address questions about water consumption, groundwater elevation levels, drought vulnerability, green infrastructure, and utility rates. As the 8th largest city in the United States and the second largest city in California, the City of San Diego has a unique relationship to water with a moderate coastal climate that extends inland to desert. Water stress indices developed in this study confirm the relationship of San Diego’s dependence on imported water to growing water demands given insufficient local supply.

San_Diego_NDI

The daily water deficit is defined as the difference between the daily water demand and the daily renewable water supply. The maximum accumulated deficit in a given year divided by the average annual rainfall across the historical period is the Normalized Deficit Index (“NDI”) for that year. Similarly the Normalized Deficit Cumulated (“NDC”) is the maximum accumulated deficit for all 61 years divided by the average annual rainfall.

Residential water rates for customers in San Diego County have increased significantly over the past decade while the total water sales made by the utilities have decreased. Pricing water rates is difficult since San Diego is dependent on many external factors including transportation of water into the county from other parts of California.

San_Diego_PEND

Price Elasticity of Normalized* Demand (En) between surveys from 2002-2012
*Amount of Total Sold Water is normalized over the Total Population Served prior to finding the Elasticity

 

San Diego County has 2000 wells located in clusters throughout the outer rims of the county. Rivers and creeks are densest in the central areas. It has low annual precipitation and no treatment facilities for storm water runoff so beach closings occur due to contaminated runoff. The majority of water consumed is imported from northern California and other states. Overuse of local groundwater has resulted in saltwater intrusion as fresh water levels decline.

Slopes of linear fit for the 68 wells with at least 20 years of data

Slopes of linear fit for the 68 wells with at least 20 years of data

 

San Diego’s Transportation and Storm Water Department focuses primarily on urban runoff mitigation and reducing Total Maximum Daily Loads (TMDL) of effluents that run into the bay, river and ocean. Through their Think Blue program the department educates and engages the public by attending community events and meetings. Green infrastructure tools utilized in this project include swales, planters, catch basins and an inlet to the Chollas Creek. Rerouting the runoff from the roads into the basin reduces the amount of accumulated pollutants on impervious surfaces and have yielded a reduction in pollutants of as much as 87% in similar projects.

 

To see the full report:

Christine (Hui) Wen, Mary Williams, Christopher Economides, and Nelson Dove. 2014. San Diego County: Assessment of water resources, green infrastructure, and utility rates. A Columbia Water Center Whitepaper in conjunction with Veolia Water North America.


Advisors: Naresh Devineni, Tess Russo, and Upmanu Lall