Amman governorate has an area of about 7,579 km2 and about 4,007,000 inhabitants (Perdew 2014, Department of Statistics 2014). The population in Amman governorate has been increasing dramatically in the last 40 years. The population growth rate is at 5.8%. In addition to this growth, there is a continuous flux of migrations and refugees from neighboring countries like Palestine, the Arabian Gulf area, Iraq, and Syria which accelerates the urban expansion (Potter et al. 2009, Odeh et al. 2017). However, in 1921 Amman was generated as the capital city of Trans-jordan and has about 5,000 inhabitants whom are mostly from Circassian, Syrian origin and the surrounded cities such as Irbid and Al-Salt. During 1961–1979 the population has increased from 215,000 inhabitants to 777,800 by the population growth, second Palestinian refugee migration, and the Civil War in Lebanon. The first and the second gulf war in the 1990’s forced more refugee waves to migrate to Jordan in general and to Amman specifically and the population becomes 851,000, and 1,017,000 inhabitants respectively. In 2014 the population of Amman become 1,698,000 after the migration of Syrians due to the civil war.
Urban area expanding because of inhabitants increasing is a common process in the capital cities such as Amman (Schneider et al 1973, Butler 2000,). However, previous studies show that urban expanding in Amman due to the population growth has increased the urbanized area from about 147 km2 in the year 1987 to 237 km2 in 2014 that means the urbanized area increased by almost 61% over the last three decades. During these decades urban expanding was at a high-rate stage during 1987–1997 and at a steady-rate stage during 1997–2007, and 2007–2014 (Al-Bilbisi 2019, Al-Bakri et al. 2013).
Geographically, Amman governorate is in the northwest of Jordan (Fig. 1). It is bounded from the east by Saudi Arabia and from the west by the Palestinian National Authority. Topographically, It has a significant variation in altitude, which ranges between (-143 m below sea level (absl.) – 1100 m absl.). It has different landforms (Fig. 2) which is influenced by the underlining geological features (Odeh et al. 2015). However, such a change in altitude and large spatial expansion combined led Amman to be influenced by the three common climatic zones in Jordan (The Jordan Valley, The Mountain Heights Plateau, and The Desert or Badai region (Potter et al. 2009, Perdew 2014). In general, northwest of Jordan is closer to the Mediterranean Sea where most of the atmospheric troughs comes and hence has more rainfall events, while the highlands are commonly the areas which receive the greatest amount of rainfall in general (Salameh and Bannayan 1993). However, The climate in Amman governorate is subtropical arid, with cold winter (November – April) in the northwest due to the high altitude l that reaches up to 1100 m, and sunny in the summer (June – September) that is slightly hot and is controlled by the adjustment desert area (Salameh and Bannayan 1993, Potter et al. 2009, Perdew 2014). Due to the topographic variation climate is changing spatially. The western highlands of the governorate are close to the Mediterranean Sea and thus affected by that climatic zone while the eastern part is close to the Arabian Desert and is affected by this climatic zone too (Berndtsson and Larson 1987, Bouraoui et al. 1999).
In our study, we selected rainfall pattern as a primary climatic indicator (Fig. 3) to simplify understanding the climatic patterns in the Amman Governorate. The rainfall patterns are integral to the quantity and quality of water resources (Salameh and Bannayan 1993 and Odeh et al. 2017, BGR 2017). The greatest rainfall pattern values (about 500 mm) are concentrated on the northwest and therefore most of its water resources are allocated in that area while the lowest values about 0 mm is in the south east of the study area (Salameh and Bannayan 1993, Potter et al. 2009).
Amman gets its water from both surface water and groundwater for agriculture, domestic, and industrial purposes. Both surface water and groundwater in Amman are solely fed by rainfall. The bank full discharge of the river and the recharge of groundwater is accounted for primarily by the receiving rain (Berndtsson and Larson 1987, Bouraoui et al. 1999, Saraf et al. 2004). However, the water resources of Amman mostly located in the northwest as a result of rainy climatic zones that prevailed in that area due to the geographic location (nearest area to the Mediterranean Sea) and landforms (mountainous area) where urbanization and population expansion is taking place (Salameh and Bannayan 1993, BGR 2017, Odeh et al. 2017).
From geological perspective, Amman is situated in a faulted zone because of the adjustment to the regional Dead Sea transform fault. The faults are mostly strike-slip faults that generate a conduits between the aquifers (Odeh et al. 2019). However, the rock units that are cropped out in the study area belong to three geologic periods which are form the oldest to youngest: pre-Cambrian, Cretaceous, and Tertiary. These rock units could be further classified into five hydrogeological units (Bender 1974, Odeh et al. 2017 ) as follows (Fig. 4):
1) Lower aquifer that consists of sandstone
2) Lower aquiclude that it consists of marl
3) Upper aquifer that consists of Limestone
4) Upper aquiclude that it consists of marl
5) Shallow aquifer that is consisted of chalk and limestone
However, the groundwater recharge of these aquifers are mostly allocated within the population and urbanization-expanding zone.
There are tens of water researches that carried on water resources on Jordan but there are no one them that correlated the effect urbanization expanding on the water resources of Amman. Therefore, the objective of this research is to investigate the effect of the urbanization expansion on the surface and groundwater resources of Amman. Such a study would enhance a sustainable water resources management by generating a spatial plan that recommends where the urban expansion must move to and where water resources enhancement project such water harvesting needs could carried out.