Intrinsic Resilience in Levant Water-Based Infrastructures ^†

Abstract

This paper surveys the historical indigenous water-harvesting and water-supply systems in the Levant, focusing on Syrian lands, where they are numerous and well-preserved. It also deals with the important hydraulic works recently carried out to exploit the area in terms of agriculture to preserve, supply and collect water. Furthermore, the paper’s scope is to evaluate the feasibility of rehabilitating ancient hydraulic structures, either by maintaining the old systems or by implementing new projects.

1. Introduction

The complexity of ancient water distribution systems management in the dry areas of Syria is increasing due to the joint effect of abnormal water consumption due to climate changes and the natural deterioration of the asset. The scarcity of water is a major constraint to sustainable development in dry areas. The securing of a livelihood for the people living in these areas depends upon their ability to access water. It is no wonder, therefore, that people living in these areas have developed long-past ingenious methods for obtaining dependable supplies of fresh water from long distances in order to meet their domestic and agricultural needs.

Historical hydraulic structures have been partially replaced by modern hydraulic ones. Old indigenous water-harvesting and water-supply systems are still widely distributed around the Syrian grazing area, where the mean annual rainfall is less than 200 mm, and the agro-pastoral system covers over 60% of the territories [1]. The majority of these structures are well-preserved but not in use any longer. One important characteristic of indigenous historical techniques is that they are sustainable and environmentally friendly.

Modern hydraulic structures were developed in order to fully exploit the area in terms of agriculture by regulating the flow of rivers, avoiding winter floods and guaranteeing the quantity of water necessary for irrigation and producing electrical energy.

2. Environmentally Friendly Water Devices

The historical water-harvesting and water-supply systems in Syria are underground and open channels, reservoirs and water wheels.

The underground channels are qanawāt and fujjarāt. They were introduced into Syria in the sixth century B.C. by the Persians when Syria was incorporated as a province within their empire [2]. The qanawāt are subterranean tunnels that tap the groundwater and direct the water to human settlements and agricultural lands by using gravity. Underground water, coming from natural sources or rain, flows into the qanāt, which has a slight slope and arrives outside. Water flows out, by means of gravity, without pumping or the aid of any mechanical device [3]. If the surface of the groundwater drops due to the lack of replenishment or recharge, the outflow rate of the qanat decreases proportionally. Therefore, the qanat does not force more water out of the aquifer than the latter can safely yield, clearly demonstrating that sustainability is integral to such indigenous and environmentally friendly techniques [4]. The fujjarāt are underground channels which differ from the qanawat because they carry water from a natural source to an underground basin. From there, water is raised by a water wheel [5]. Some vertical shafts are dug into a hill and connect the channel to the surface. They were employed both as air shafts and for access to the underground level. The fujjarāt, like most qanawāt, are no longer in use, owing to a drop in the water tables of these regions and a lack of maintenance. They are located throughout Syria, and examples may be found, for instance, at Palmyra, in the areas of Dayr al-Zūr, Homs and Ḥamā.

Open channels are carved, slightly sloping stone canals that transport water from a reservoir to agricultural areas. Because gravity was the sole source of power-conducting water, the reservoir normally had to be higher than the land area to which the water was transported. These channels were 20 to 40 cm wide [6]. Their cross-section can be trapezoidal, rectangular or triangular. They were numerous across Southern Syria. Significant examples are the channels at Tyre and Qalamun. Some of these channels are still used for agricultural purposes. However, many structures are not in working order, as they were damaged by modern hydraulic structures, which eradicated most of them.

Reservoirs are of different types. The khazzānāt are open, stone-walled reservoirs which receive water from nearby springs through channels dug under the surface of the ground. Built to provide water to both people and animals, these reservoirs are still in use today in Bosra al-Sham and Suweidah. The birak are large water-storage tanks open to the sky into which rainwater is channeled [7]. The walls of these basins are constructed of smooth stones. In the middle of the construction is an elevated outlet (above the level of the pool bed), which allows water to be withdrawn and transported to villages and farms. This type was widely used in Southern Syria [6]. One of the best preserved birak is the birka al-Hajj at Bosra (Figure 1). The ābār rūmānī are parallelepiped wells dug underground and have a narrow intake at the top. They are usually built on mountain slopes where small streams meet. The interior walls of the cisterns are often strengthened by an impermeable layer of cement, which is often smooth. Examples may be found at Ḥoms, Ḥamā, Dayr al-zūr and Aleppo. Their size differs from place to place and is often related to the nature of the rock formations in the area. These wells are often in a poor state of repair due to the accumulation of deposits resulting from erosion [6].

Water wheels were used to lift and convey water from rivers and wells. The devices which are associated with the fujjarāt are norias and sāqiyas. Thus, they were probably introduced into Syria when this type of fujjāra entered the country in the sixth century B.C. [3]. They mark the type of installation moved by animals to raise water from streams or the underground to irrigate fields or to supply water for small structures. They are composed of a machine which is moved using animal power, which turns a horizontal cogwheel made of wood and then a vertical cogwheel. The latter transmits the rotation to the main wheel of the structure, which is a vertical wheel partially submerged in the water or inserted into a well (Figure 2). Around the rim of the main wheel there are some buckets which fill up when they reach the water. Raised water is poured into a tank, and from the tank, water passes directly into the distribution channels to irrigate fields and gardens. The installation is a “noria” if the vertical cogwheel and the wheel with buckets are situated in the same cavity because they are connected to each other by a short axle. The installation is a “sāqiya” if the vertical cogwheel and the wheel with buckets are connected by a long axle and are inserted into two different cavities. The horizontal axle can be underground or elevated. A further type of water wheel is the hydraulic noria, which raises water by using the power of a river and has been employed to irrigate fields, owing to the great power provided by the river. Hydraulic norias are employed where the level of the river is considerably lower than the level at the bank of that river. They are composed of a vertical wheel made of wood and an aqueduct made of stone. The base of the wheel is submerged in the river and turns because of the current. Water is carried to the top of the wheel through compartments or pots placed on the periphery of the rim and is poured into the channel on the top of the aqueduct and directed to irrigate fields. In Syria, these devices first appeared during the Roman times, between 60–50 B.C. and the early third century A.D., but the exact place is still uncertain [3]. Most hydraulic norias are located along the Orontes river, where some examples are still in working order, and along the Euphrates and Khabūr rivers.

3. Sustainability in Water Supply Systems

As a consequence of technological progress and the increasing need for water, modern hydraulic structures have replaced the old hydraulic structures. The use of traditional water-supply systems has gradually declined in Syria. Many structures have stopped working, and most have been abandoned and are considerably deteriorated. Modern hydraulic structures include the construction of reservoirs created by the new dams built along the rivers, which normally fill during the winter and are used for irrigation in the summer when the dam is opened, and water enters the river (Figure 3). When the river is sufficiently filled by the reservoirs created by the dams, electrical pumps raise and pour water into a network of artificial canals to irrigate the fields (Figure 4). It is also possible to find that modern hydraulic pumps for irrigation are placed close to the old hydraulic norias in order to exploit better the quantity of water available in the area.

There is a consensus, however, that either the restoration or rehabilitation would enhance the resilience of the ecosystem and help provide socio-economic support to the dependent communities [8]. Several assessments of the Syrian water-supply systems show that it would be more economically and environmentally desirable to improve the efficiency of the existing systems than to construct new ones [9]. To implement irrigation systems and thus cope with the increasing need for water, the Syrian government is laying out several projects aimed at maintaining some of the old systems, such as the ābār, which is considered one of the main water resources for the Syrian steppe, and is also implementing new projects in order to use surface runoff water and reduce the annual water consumption [6]. These projects could mainly consist of exploiting the surface water coming from rivers and springs by installing new devices, such as sprinklers or drip irrigation, and constructing new line canals from the headwork to the farms. Underground water could be exploited by the rehabilitation and re-employment of old wells, in which measuring devices would be installed, and the water subsequently canalized to reach the fields for irrigation. Water wheels are not expected to be re-employed. The wells associated with animal-powered machines provide a limited quantity of water compared to the other ancient water-harvesting systems. Regarding the hydraulic norias, a re-employment for their original purpose would be difficult, not only because the big hydraulic structures built in the river valleys have reduced the level of the river but also because, owing to the deteriorating state of most installations, any restoration aimed at reactivating them would mean reconstructing, in many cases, entire aqueducts or demolishing recent constructions abutting the remains of aqueducts. In addition, a re-employment of the hydraulic norias for their original purpose could diminish their cultural value, as they could be seen mainly as utilitarian structures. Otherwise, rehabilitating water wheels, in terms of historical heritage, would contribute greatly to the knowledge of these traditional ecosystems, which maintain a significant position in the history and culture of Syria [3].

4. Conclusions

Water resources in dry environments are becoming scarcer, especially under the changing climate conditions. In response, ancient knowledge of rainwater-harvesting systems and water-supply systems is still relevant, especially in dry environments. Some approaches to restoring the degraded ecosystems that are suitable for rehabilitation are slow to show significant and satisfactory results. Nonetheless, some old practices and technologies may not be feasible for the present and future. In particular, by evaluating the feasibility of renovating hydraulic norias as a sustainable system, as well as an expression of historical and cultural heritage, it has been noted that a re-employment of these ecosystems for their original purpose would present considerable difficulties, despite the advantages that they could provide.