Rivers In Israel Research Articles

Accelerating Technology Transfer by Means of ATTA (Advanced Technologies in Traditional Agriculture)

Over the past 20 years a rapid adoption process of agricultural technology has taken place in the Jiftlik Valley, west of the Jordan River in Israel. Vegetable production has increased more than tenfold and net income of most of the farmers has increased by an even greater factor, thanks to the improved quality of the produce. This dramatic change can be attributed to the innovativeness and full participation of the farmers. At the start of the technology transfer process the study population was characterized by two socio- economic features: a traditional but stable social structure, and the existence of a continuous market demand for the high-value crops it produced. Against this background the main elements contributing to the development were: (a) suitable agricultural technology; (b) the physical support system, e.g., credit and infrastructure; (c) a balance of privately and publicly supplied extension services; and (d) backing in the form of appropriate intervention by the government.

Indices of hydrological drought in Israel

Indices of drought are formulated and examined on annual volumes of streamflow in Israel. Drought is defined as a severe shortage in the appearance of natural waters with respect to normal for place and time. The term severe shortage means here a deep, continuous and widely extended shortage. For reasons of generality, the normal and the shortage are described here by the mean and the standard deviation of the recorded data. In the examination, a deep shortage is considered to be the case when the annual volume of the streamflow is lower than the mean by at least one standard deviation. A continuous shortage is the case when the annual volumes are lower than the mean for at least four successive years. A widely extended shortage is the case when a deep or a continuous shortage extends over the entire region under consideration. The examination covers 14 rivers in Israel for which approximately homogeneous records are available for at least 30 years. The mean annual volume of flow in these rivers is from 0.85 to 399 × 10 6 m 3, and the coefficient of variation is between 0.3 and 3.2. The examination reveals that within the time span of the available records there have occurred two events of an extended deep shortage and two events of an extended continuous shortage. The two kinds of extended shortage did not coincide, but they occurred shortly one after the other. According to our terminology, no drought occurred in Israel within the time of the available hydrological records.

Relationship between water pollution and the flora of two coastal rivers of Israel

Changes in the vegetation of two coastal rivers in Israel were studied in relation to increasing pollution. Pollution levels were defined mainly in terms of ammonium content, presence of detergents and dissolved oxygen concentration at various depths and at various times of the day. It was found that species diversity was greatest in the clean-water sections of the rivers and decreased considerably with increasing pollution. No floating-leaved or submerged species were found in the polluted sections; these and some other species were exclusive to the clean-water sections. On the other hand, none of the hygrophyte species was exclusive to polluted sections. The distribution of several plant species across the rivers and the river banks was noted and it appears that although tolerant species can grow partly submerged in clean water, they avoid direct contact with polluted water.

The effects of various components of water pollution on the behaviour of some aquatic macrophytes of the coastal rivers of Israel

Seven aquatic macrophytes, with an exclusive distribution in clean sections of two coastal rivers in Israel, were transplanted into polluted sites in the same rivers. Five species died shortly afterwards, whereas two survived uninjured. Three “clean water” species ( Nymphaea caerulea, Ludwigia stolonifera and Scirpus litoralis) were treated with several water pollution factors. Detergents caused severe damage to all plants, whereas ammonium caused a temporary damage only in Nymphaea. Other factors, like anaerobiosis and increased levels of nitrate and phosphate had no effect on the plants. It is assumed that the present content of detergents in most polluted sections of the two rivers constitutes the main limiting factor for many hydrophytes and hygrophytes which occur in the non-polluted sections. The possible use of certain aquatic macrophytes as indicators for varying levels of pollution is discussed.

Aspects of trace metal contamination in the coastal rivers of Israel

Nine trace elements of biological concern: Cr, Co, Cu, Cd, Ni, Pb, Hg, Zn and Ag were investigated in the sediments of the most important coastal steams in Israel. All of these are subjected to some degree of domestic and/or industrial sewage input with the consequent liability of contamination by trace metals. The Ayyalon, Gadura, Qishon and locally the Hadera rivers contain sediments exhibiting severe pollution effects. There is a danger of infiltration through the soils into the groundwaters as well as exposing nearshore fauna to sediments contaminated by possibly toxic trace metals. The other rivers bear smaller levels of trace metals; however, an increase of the Pb and the Zn levels occurs near major highways.