1. by Audrey H. Sawyer, Cédric H. David, and James S. Famiglietti
Continental patterns of submarine groundwater discharge reveal coastal vulnerabilities
by Audrey H. Sawyer, Cédric H. David, and James S. Famiglietti
Science
Volume ():aag1058
August 4, 2016
Copyright © 2016, American Association for the Advancement of Science

2. Fig. 1 SGD estimates from this study and the literature.
SGD estimates from this study and the literature. Our SGD values correlate well with local estimates (12) but are generally lower. Circles are from seepage meters, squares are from water budget analysis, and triangles are from multiple methods. Filled symbols indicate fresh SGD estimates. Open circles indicate total (fresh and saline) SGD. We calculated total SGD rates from our fresh rates using the relation SGDtotal = 1.1 SGDfresh m2/y (14, 30).
Audrey H. Sawyer et al. Science 2016;science.aag1058
Copyright © 2016, American Association for the Advancement of Science

3. Fig. 2 Map of fresh SGD rates along the contiguous United States coast.
Map of fresh SGD rates along the contiguous United States coast. On the West Coast, fresh SGD increases from south to north with net precipitation (Net P) while drainage length (DL) remains consistent (top plot). The shape of recharge zones (cartoon inset) dictates local variability. Recharge zone a has shorter DL, while zone b has longer DL. Fresh SGD is calculated from the product of infiltrating precipitation (I) and DL (DL=A/L, where A is recharge zone area and L is coastal length). Non-infiltrating runoff (R) does not contribute to fresh SGD. Expanded view of Cape Cod, Massachusetts shows coastal recharge zones colored by rate of fresh SGD.
Audrey H. Sawyer et al. Science 2016;science.aag1058
Copyright © 2016, American Association for the Advancement of Science

4. Fig. 3 Coastal vulnerability map.
Coastal vulnerability map. Vulnerability to offshore contamination (dark blue) is identified where the rate of fresh SGD is above average (420 m2/y) and developed or agricultural land use is above average (27.7%). Vulnerability to saltwater intrusion (pink) is identified where low fresh SGD or high groundwater extraction may cause complete saltwater invasion. Light blue coastlines are vulnerable to both offshore contamination and saltwater intrusion. Inset shows histogram of fresh SGD rates for the contiguous United States.
Audrey H. Sawyer et al. Science 2016;science.aag1058
Copyright © 2016, American Association for the Advancement of Science