Ecosystem services and equity: How do drinking water supply reservoirs shift local demographics?

Background/Question/Methods

Sustainable cities need infrastructure to supply ecosystem services, such as clean drinking water, to their populations.  Development of this infrastructure has social consequences that must be weighed alongside any ecological and economic effects.  A significant amount of research has documented that locally unwanted waste infrastructure is usually sited near communities of lower socioeconomic status and tends to perpetuate that status.  Reservoirs, similarly, tend to be sited in communities of lower socioeconomic status, but their long-term effects on the status of neighboring communities have received little attention.  We hypothesized that the demographics of populations around reservoirs, once created, shift from lower to higher socioeconomic status.

We used U.S. Census data to determine how demographics in populations neighboring North Carolina municipal water supply reservoirs vary through time and with increasing distance from the reservoirs.  We identified all municipal water supply reservoirs in North Carolina and re-aggregated Census data on race and income to four bands around the reservoirs: 0 – 0.5, 0.5 – 1, 1 – 3, and 3 – 5 miles These bands are based on North Carolina water quality regulations and buffer radii commonly used in demographic studies.  The percentage of the population that was White was calculated for each band for 1960, 1970, 1980, 1990, and 2000.  Per capita income was calculated for each band for 1980, 1990, and 2000. 

Results/Conclusions

Preliminary results indicate that higher-income individuals and Whites become a larger percentage of populations living within 0.5 mile of reservoirs through time, and that higher-income individuals and Whites are over-represented in that band as compared to the other bands and the state as a whole.  Thus, reservoirs appear to create enduring localized demographic shifts that may signal an inequity in the way we deliver clean water.  More generally, choices we make in how we deliver ecosystem services are likely to have equity implications that should be examined.  Our analysis approach can be applied to other infrastructure, such as sub/urban roads, greenways, and parks, to generate information for policymakers’ use in assessing and addressing the infrastructure's social effects.