Coastal springs discharging along the coastline of the Hualālai region from Kīholo and Keauhou aquifers were sampled to determine water quality and chemical characteristics of the groundwater. Stable isotopes of water were used to determine recharge origin and possible subsurface water flow lines. Specifically, as shown in previous studies there is a predictable relationship between ð¹⁸O of water and precipitation elevation, a relationship that allows distinguishing recharge from the slopes of Hualalai (<2500 m) and Mauna Kea and Mauna Loa (>2500 m). Cluster analysis was used to identify similarities and differences between stable isotope signatures within and between aquifers. According to this analysis, coastal springs group according to similarities in recharge elevation and resulting possible flow patterns.  The distribution and extent of these groups is illustrated on Figure 1 with different groups assigned a different color for easy identification. The major conclusions of this analysis are that groundwater in multiple groups of coastal springs have to originate beyond aquifer boundaries and that coastal springs in the Keauhou aquifer cannot be explained by recharge solely in the basal lens suggesting water contribution from the high-level aquifer.

A new generation of SGD Sniffer, an autonomous SGD monitor, has been developed to document SGD in fishponds and anchialine pools. Understanding the magnitude and trends in groundwater discharge to these coastal ecosystems is vital for their better management and preservation. Optimal salinity and nutrient distribution in ponds are maintained by the interplay between groundwater discharge and seawater intrusion (driven by tides & seasonal water level fluctuations). Using long-term groundwater flow observations we can determine baseline and extreme (wet/dry season and high/low sea level) conditions to understand natural variability and thresholds of minimum groundwater flow required for keeping salinity and nutrient fluxes within optimal limits.  Another parameter that this research provides is the amount of nitrogen delivered by SGD to coastal systems. Nitrogen has both natural and man-made sources and amounts beyond an optimal level have detrimental effects on native groundwater dependent ecosystems.