The Alexander River drains a large area covering 550km2 and therefore conducts great quantities of water in the winter. Its channel was narrow in the past, and the flooding created large areas of marshland all over the Hefer Valley. These swamps were drained in the 1930s, in the early days of Jewish inhabitation of the valley. In those days the river contained a great diversity of aquatic plants.
In the 1960s, part of the river channel in the Sharon was widened in order to prevent flooding in winter. Nevertheless, here and there, close to the river, there are still a few small, stubborn springs left from the former swamps, which flow in small canals these days, surrounded by reeds and canes, directly to the channel of the Alexander River.
Some people attribute the name of the river to Alexander Yanai, the Hasmonean king, who conquered foreign cities in the region. In any case, it was not inconvenient for those who named the river that the lower part of the river, the part near the estuary, was called Wadi Iskander, in Arabic, after Iskander Abu Zabura, who “protected” the rafts that transported watermelons on the river to the port near Michmoret in the late nineteenth century.
After the establishment of the State of Israel, the Alexander River saw hard times. The pollution and waste thrown into it turned its channel into a fetid sewage canal. A major source of pollution was the effluents that flowed from the Nablus streambed, the main tributary of the Alexander.