Constraining modern and historical recharge from bore hydrographs, ³H, ¹⁴C, and chloride concentrations: Applications to dual-porosity aquifers in dryland salinity areas, Murray Basin, Australia

Water table fluctuations and renewal rates based on ³H and ¹⁴C concentrations in bores screened within 5 m of the water table were used to estimate recharge rates in five dryland salinity areas in northern Victoria, Australia. Given the resolution of each technique both methods yield broadly similar results of 4-90 mm/yr (up to 14% of modern rainfall) that reflect the recharge rates following land clearing over the last 200 years. Deeper bores show mixing of modern recharge with older water flowing laterally through the aquifers. Recharge estimates based on Cl concentrations are up to two orders of magnitude lower (