Mapping groundwater discharge to a coastal lagoon using combined spatial airborne thermal imaging, radon (Rn-222) and multiple physicochemical variables

• Coastal lagoons are significant wetland environments found on coastlines throughout the world. Groundwater seepage may be a key component of lagoon water balances, though only a few studies have investigated large (>100 km(2)) coastal lagoons. In this study, we combined airborne thermal infrared imagery with continuous measurements of radon (Rn-222-a natural groundwater tracer), conductivity, water temperature and dissolved oxygen to map groundwater seepage to a large coastal lagoon in New Zealand. We found evidence of seepage along the margins of the lagoon but not away from the margins. Our findings confirmed previously known seepage zones and identified new potential locations of groundwater inflow. Both point source and diffuse seepage occurred on the western and northwestern margins of the lagoon and parallel to the barrier between the lagoon and sea. These observations imply geologic controls on seepage. The combination of remote sensing and in-situ radon measurements allowed us to effectively map groundwater discharge areas across the entire lagoon. Combined, broad-scale qualitative methods built confidence in our interpretation of groundwater discharge locations in a large, dynamic coastal lagoon.

Subject headings

NATURVETENSKAP  -- Geovetenskap och miljövetenskap -- Oceanografi, hydrologi och vattenresurser (hsv//swe)

NATURAL SCIENCES  -- Earth and Related Environmental Sciences -- Oceanography, Hydrology and Water Resources (hsv//eng)

Keyword

airborne thermal imaging

coastal hydrology

groundwater

groundwater

discharge to lagoons

groundwater-surface water interaction

lagoon

radon

spatial distribution of groundwater discharge

sediment-water interface

radium isotopes

continuous monitor

nutrient

inputs

seepage

temperature

salinity

recirculation

contamination

dependence

Water Resources

Publication and Content Type

ref (subject category)

art (subject category)