Diversity analysis of water sources, uses, and flows from source to use in the USA.

Diversifying a system can reduce risk from- and increase resilience to perturbation. For this reason, the concept of diversity has been used in many different fields but its use in analyzing engineering infrastructure has been limited. In particular, the diversity of water sources and uses and the diversity of how sources are connected to uses (flow) have never been analyzed. In addition, the relationships between diversity and economic efficiency of water systems remain uncertain. In this study, we addressed these topics by conceptualizing and quantifying water source, use, and flow diversity in the USA. Water source and water use data were collected from the US Geological Survey for 2000, 2005, and 2010. Diversity was calculated with the Shannon Weaver Index. The overall mean water use diversity by state was 0.79 ± 0.31 (N = 150) and increased from 0.63 ± 0.31 in 2000 to 0.89 ± 0.28 by 2010, reflecting overall decreases in high-use categories, like thermonuclear power, and relative increases in already low domestic use. In contrast, source diversity showed no change over time, with an overall state mean of 0.82 ± 0.28 (N = 150) but varying between states largely due to differences in geographic and climatic factors influencing regional water sources. Water flow diversity also showed no change over time, averaging 1.00 ± 0.43 (N = 150), higher than both source and use diversity. The mean water use efficiency for all states over the study period was 52 ± 60 $/m of water and was positively and strongly related to both source and use diversity. Thus, the USA water system diversity is sensitive to factors logically expected to influence both source and use, and directly affects water use efficiency.