Deep desert aquifers as an archive for Mid- to Late Pleistocene hydroclimate: An example from the southeastern Mediterranean.

Many efforts have been made to illuminate the nature of past hydroclimates in semi-arid and arid regions, where current and future shifts in water availability have enormous consequences on human subsistence. Deep desert aquifers, where groundwater is stored for prolonged periods, might serve as a direct record of major paleo-recharge events. To date, groundwater-based paleoclimate reconstructions have mainly focused on a relatively narrow timescale (up to ∼40 kyr), limited by the relatively short half-life of the widely used radiocarbon (5.

Metabolic adaptations underpin high productivity rates in relict subsurface water.

Groundwater aquifers are ecological hotspots with diverse microbes essential for biogeochemical cycles. Their ecophysiology has seldom been studied on a basin scale. In particular, our knowledge of chemosynthesis in the deep aquifers where temperatures reach 60 °C, is limited.

Controls on the Cl/Cl input ratio of paleo-groundwater in arid environments: New evidence from Kr/Kr data.

Measurements of the long-lived Kr and Cl radioisotopes in groundwater from the Negev Desert (Israel) were used to assess the Cl/Cl input ratios and Cl contents for paleorecharge into the Nubian Sandstone Aquifer (NSA). The reconstructed Cl content of the recharge flux was on the order of 300-400 mg/L. An initial Cl/Cl ratio of 50 × 10 was assessed for the groundwater replenishment in the Negev Desert since the late Pleistocene, in agreement with the Cl/Cl ratios in recent local rainwater.

Correlating fracture trends and hydraulic head using semivariogram cloud analysis.

Fracture trends (defined as kilometer-scale linear features interpolated between field observations of fractures along their strikes) often have a dominant orientation. Finding a correlation between this orientation and hydraulic data could shed light on their hydraulic influence. A significant correlation between head residuals from first-order regional drift and the orientation of 2- to 4-km-long fracture trends was found in a study site in the Negev, Israel, using the semivariogram cloud analysis.

Particle transport in unsaturated fractured chalk under arid conditions.

A series of field and laboratory experiments were conducted to study the mechanisms of particle detachment and transport from fractures in vadose chalk. Experiments of intermittent flow events along fracture surfaces were carried out in the laboratory. In the field, water was percolated from land surface via a discrete fracture into a compartmental sampler installed inside a horizontal corehole located I m below the surface.