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A 4.5 km section of the River Dan in northern Israel was sampled at intervals of 6 weeks, between April 1983-March 1984, using standardized mesh bags. The river is characterized by extremely stable temperature and other physical and chemical conditions. The effects of a water diversion project 2400 m from the spring were investigated.

The relationships between fauna and depth, current velocity and distance from the spring sources were evaluated. Of 48 common taxa analyzed, 27 showed relativity to the distance from the sources, 18 to current velocity and 12 to depth. The lowest density of invertebrates, but the highest number of taxa and highest variety of species were found at the spring sources. The sampling site immediately downstream from the water diversion project was characterized by intermediate densities, lowest varieties of species and highest evenness of distribution.

Results are compared with the predictions of the Intermediate Disturbance Hypothesis; but the influence of invertebrate drift caused this hypothesis to be inapplicable to lotic waters. Invertebrate drift is in addition suggested as an important factor governing the structure of the fauna at the spring sources.