An-Najah Staff

Zimar stream has become since the 1950's as a sewage drain. The stream extends over 27 km from the west of Nablus city to Tulkarem city in the northwestern of West Bank. There are lost opportunities for streams’ water beneficial use, and nature conservation principals have been severely violated for the Zimar watershed, in addition to public health and biodiversity threats. This paper was prepared to predict the water quality of the Zimar’s stream under current and proposed future conditions under different scenarios. Dissolved Oxygen was taken as the main quality parameter, and depending on steady state solutions of Streeter-Phelps’ equation. QUAL2Kw model was used to predict the behavior of the stream. Water samples were collected, and field measurements were conducted for eight different critical locations along the stream, and during the wet and dry seasons of 2011–2012. Several scenarios were simulated, taking in consideration the influences of the underconstruction  wastewater treatment plant in the western area of Nablus city, proposing additional wastewater treatment plant at Anabta village, and proposing constructing of three artificial weirs. It was found that the stream has significant self-purification capacity as the dissolved oxygen concentration doubled from Nablus city to Anabta village; midway to Tulkarem. The Biological oxygen demand between those two points decreased to values up to 11% from the original value. This paper supports proposed solutions of the stream to improve its water quality, provide water for agricultural irrigation and enhance aesthetic views in the catchment, these are beyond the protection of public health and the environment.