The Zarqa River is the second largest tributary of the lower Jordan River, after the Yarmouk River. It is the third largest river in the region by annual discharge, and its watershed encompasses the most densely populated areas east of the Jordan River. It rises in springs near Amman, and flows through a deep and broad valley (which is identified with the biblical Jabbok River) into the Jordan, at an elevation 1,090 meters (3,580 ft) lower.
The river is heavily polluted and its restoration is one of the top priorities for the Jordanian Ministry of the Environment. Geologically, the Zarqa river is about 30 million years old. At the river's origin is 'Ain Ghazal, a major archaeological site that dates back to the Neolithic period. Archeological finds along the course of the river indicate the area was rich in flora and fauna in the past.
The Zarqa river is well known for its amber deposits that date back to the Hauterivian of the lower Cretaceous (135 m.y.). A remarkable flora and fauna was reported from this amber reflecting a tropical paleoenvironmental prevailing conditions during the time of resin deposition (Kaddumi, 2005; 2007). The modern Arabic name, Zarqa , means "the blue river". The Hebrew name Jabbok derives from the word "baqoq", which means "to flow" or "pour out".
The headwaters of the Zarqa begin just northeast of Amman, rising from a spring named Ain Ghazal ("Gazelle spring"). The river flows to the north before heading west. Rising on the eastern side of the mountains of Gilead, it runs a course of about 105 kilometers (65 mi) in a wild and deep ravine before flowing into the Jordan River between Gennesaret and the Dead Sea, at a point 1,090 meters (3,576 ft) below its origin. At its higher reaches, the river banks are mostly steep and canyon-like. Near Ain Ghazal, two tributary wadis join the river, and it opens up into a shallow basin.It forms the border between the Jordanian administrative regions of Irbid and Al Balqa.
The new Jerash Bridge crosses the Zarqa upstream of King Talal reservoir, on the road from Amman to Jerash. The bridge is the site of a gauging station where flow measurements are continuously taken. In the city of Zarqa, several bridges, vehicular and pedestrian, cross the river. The earliest of these was built by the Chechen founders of the city. Current bridges include the Zawahreh Bridge, a vehicular bridge connecting Baha' al-Din Street with al-Zuhur Street and the another connecting Baha' al-Din Street with King Talal Street. Two pedestrian bridges connect al-Zuhur Street and Baha' al-Din Street, and Wasfi al-Tal Street and Petra Street.
The geological origins of the Zarqa river are about 30 million years old, when the Jordan Rift Valley was formed. A ripple effect of its formation was the creation of side-wadis. The Zarqa river carved into the western edge of one of these side wadis.The earliest exposed formations in the area date from the Triassic and early Jurassic periods, and have been named Zerqa and Kurnub formations. The rock formations are marine sediments, remnants of the prehistoric Tethys Sea, which used to cover the area running roughly east - west, halfway across the present Dead Sea. Along the Zarqa, we find crystalline limestone alternating with shale. The next layer is a 20-30 meter high layer of gypsum, argillaceous marly lime, shales and iron-rich stone and sandstone. This layer is rich in fossils.The Zarqa valley was an important passageway connecting the Eastern Desert with the Jordan Valley.
Archaeological finds of charcoaled remains indicate that poplar and tamarix used to grow along the banks of the Zarqa, with forests of wild oak growing on the hillsides.Today, tamarix thickets are still widespread in the floodplains, and the banks are cultivated with fruit orchards and vegetable fields. Along the course of Zarqa river, water is pumped directly and used to irrigate crops of leafy vegetables such as parsley, spinach, cabbage, cauliflower and lettuce, as well as potatoes. Olive trees are also found along the river's banks.Tulips grow on many hillsides of the river,while in the springs area and the watercourse, water vegetation is found.Natural pine forests grow in the King Talal Dam area.Along the upstream banks, where the river runs wild, one finds the common reed, oleander and Typha species.Since the waters of the Zarqa are highly contaminated, with high levels of organic matter and various chemical compounds (especially detergents and dyes), the use of Zarqa water for irrigation has significantly altered the biodiversity of the natural flora, and caused the disappearance of the majority of fresh water species.
In prehistoric times, the area was rich with fauna, and 45 distinct animal species have been identified, half of them wild animals. Domesticated goats were the most common, and gazelles were the most frequently occurring wild animal species. Today, the area is still home to a diverse population of birds and mammals, and some of the breeding species found do not breed anywhere else in Jordan.Among the bird species found are the European Roller, Desert Lark, Dead Sea Sparrow, Desert Finch and Blue-cheeked Bee-eater. The King Talal dam has created a lake which is a habitat for migratory waterfowl and various fish species. Notable birds found in the lake area include the Little Bittern, Cattle Egrets, Grey Herons, White Storks, Common Teal and Eurasian Coot. The lake's waters sustain stock of fish, some of which is indigenous species and some introduced species. The most common are Tilapia. Migratory birds also winter in the man-made pools which make up the Kherbit Al-Samra Sewage Treatment Plant, located in a broad depression close to Wadi Dhulayl, the main tributary of the Zarqa River. As many as 6,000 White Storks have been spotted roosting there. Mammals found in the area include the Common Otter (Lutra lutra), and the Persian Squirrel (Sciurus anomalus).The otter is considered a threatened species.
'Ain Ghazal, the origin of the spring the feeds the Zarqa river, is a major archaeological site, dating back to the Neolithic period. It was continuously occupied for more than two thousand years, and the earliest finds date to 7200 BCE.'Ain Ghazal is one of the earliest known human settlements with evidence of domesticated animals. With a population of around 3,000 at its height, it was also one of the largest prehistoric population centers in the Near East, with about five time the population of neighboring Jericho. During a 1982 survey of the Zarqa valley, a number Early Iron Age sites were discovered, concentrated along the banks of the Zerqa and its tributaries.