Earth-tide-induced fluctuations in the salinity of an inland river, New South Wales, Australia: a short-term study.

Wybong Creek discharges salts into the agriculturally and industrially important Hunter River in New South Wales, Australia. Abrupt increases in salinity occur periodically in the mid-Wybong Creek catchment. In order to understand the processes which cause these abrupt increases, changes in surface and groundwater were investigated. It is shown that salinity increases can be attributed to highly discrete groundwater discharge directly into the river from below. Hourly electrical conductivity data measured in the river showed regular, diurnal electrical conductivity fluctuations of up to 350 µS cm-1. These fluctuations could not be attributed to barometric pressure, temperature, or evapotranspiration. Instead, a similar periodicity in surface water electrical conductivity and groundwater height in nearby groundwater wells was found. Fluctuations were of similar periodicity to the orthotides which cause fluctuations in surface water height and are induced by Earth tides. The geology in the mid-catchment area indicates conditions are optimal for Earth tides to impact groundwater. The reporting of orthotidal changes in water chemistry in this article is believed to be the first of its kind in the scientific literature, with the large fluctuations noted having important implications for water monitoring and management in the catchment. Further research investigating Earth-tide-induced phases of groundwater heights will better constrain the relationships between surface water chemistry and groundwater height.

Can Coarse Woody Debris Be Used for Carbon Storage in Open Grazed Woodlands?

Carbon dioxide off-setting policy in the agricultural sector is focused on manipulating the terrestrial carbon cycle by reafforestation and increasing the retention of carbon within agricultural soils. We quantified the amount of carbon stored in the living and dead biomass and the surface soils of a previously grazed woodland ecosystem. We demonstrate that modification of coarse woody debris management could potentially store 8 to 15 t C ha. This large carbon pool raises the prospect that appropriate management of temperate woodlands to retain coarse woody debris and increase its volume into the future could achieve increased landscape carbon storage.