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Recession curves contain information on storage properties and different types of media such as porous, fractured, cracked lithologies and karst. Recession curve analysis provides a function that quantitatively describes the temporal discharge decay and expresses the drained volume between specific time limits (Hall 1968). This analysis also allows estimating the hydrological significance of the discharge function parameters and the hydrological properties of the aquifer. In this study, we analyze data from perennial springs in the Judean Mountains and from others in the Galilee Mountains, northern Israel. All the springs drain perched carbonate aquifers. Eight of the studied springs discharge from a karst dolomite sequence, whereas one flows out from a fractured, slumped block of chalk. We show that all the recession curves can be well fitted by a function that consists of two exponential terms with exponential coefficients alpha1 and alpha2. These coefficients are approximately constant for each spring, reflecting the hydraulic conductivity of different media through which the ground water flows to the spring. The highest coefficient represents the fast flow, probably through cracks, or quickflow, whereas the lower one reflects the slow flow through the porous medium, or baseflow. The comparison of recession curves from different springs and different years leads to the conclusion that the main factors that affect the recession curve exponential coefficients are the aquifer lithology and the geometry of the water conduits therein. In normal years of rainy winter and dry summer, alpha1 is constant in time. However, when the dry period is longer than usual because of a dry winter, alpha1 slightly decreases with time.

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Tomatoes, cucumbers and sweet peppers (capsicums) were grown in hydroponic systems in which the nutrient solutions were recirculated. The EC of the nutrient solution was maintained at values of 2.5, 3.7 or 5.2 dS m-1 (25 degrees C) in the different treatments. In some of the treatments, the EC values mentioned were achieved by addition of nutrients, and in others by addition of a combination of nutrients and NaCl. Yields of all 3 crops were adversely affected by increased EC values. Most fruit quality characteristics, on the contrary, were favourably affected. However, the incidence of blossom-end rot in tomatoes and capsicums increased at higher EC values. For capsicums, this was especially the case with NaCl addition. Apart from that, only slight specific NaCl effects were noticed. Salinity threshold values for the different crops lay between 2.3 and 3.5 dS m-1 and salinity yield decrease values ranged from 2.3 to 7.6% for each dS m-1. The absorption of Na and Cl differed with crop and with the Na and Cl concentration. (Abstract retrieved from CAB Abstracts by CABI’s permission)

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The composition of groundwater reclaimed from tertiary soil aquifer treatment systems reflects the dynamic processes taking place in the subsurface, between the infiltration basin and the production wells. At the end of year 2000, following more than a decade of operation, high Mn concentrations (2 micromol L(-1) < or = Mn < or = 40 micromol L(-1)) appeared in the reclaimed effluents of the Dan Region Sewage Reclamation Project (Shafdan), Israel. A mass balance indicates that the high Mn excess originated from the aquifer rocks, most likely following reduction of sedimentary Mn-oxides under suboxic conditions. The subsequent adsorption of the Mn2+ results in a slow Mn2+ front that advances in the direction of groundwater flow only when all the Mn2+ exchangeable sites are saturated. A retardation factor obtained from two independent estimates based on a simple reduction-adsorption-advection model yields a value of about 10. This explains the delayed appearance of the high Mn concentrations at a distance of only -500 m from the infiltration basin.