Rivers of Lebanon: Significant Water Resources under Threats

*Amin Shaban*

#### **Abstract**

Lebanon is known by tremendous water resources, and this has been often viewed from the considerable number of rivers (i.e. 14 rivers). These rivers are characterized by small catchments and short length. The estimated average annual discharge from these rivers is approximately 2800 million m<sup>3</sup> . Due to the sloping terrain of Lebanon; however, it was estimated that more than 75% of water from rivers is unexploited it mainly outlets into the sea. The majority of water use from the Lebanese rivers implies domestic, agriculture, as well as some other rivers are used for hydro-power generation where they contribute by about 20% of electricity needed for Lebanon. Lately, and added to water pollution, there is abrupt decline in the discharge from these rivers estimated to more than 60% of their average annual discharge. This unfavorable situation is attributed, in addition to the changing climate, to the anthropogenic interference is the most affecting one and it is represented by over pumping from these rivers and form the recharge zone for groundwater and springs that feed these rivers. This chapter aims at introducing a discussion on the existed challenges on the Lebanese rivers and the proposed and their impact.

**Keywords:** stream flow, over pumping, climate change, pollution, dams

#### **1. Introduction**

Rivers in Lebanon are usually considered as the most significant water resources, as well as they are one of the known heritage sites and distinguished landscape. They show dense networks since there are 14 rivers located in the area of 10,452 km2 . Therefore, the estimated total annual discharge is about 3452 million m3 where there is about 20% of this discharge goes into the Transboundary Rivers, therefore, the net discharge from the Lebanese rivers is approximately 2800 million m3 /year.

The average annual discharge from these rivers is about 247 million m<sup>3</sup> , which is low enough if compared with international rivers, as an example, this volume of water is equivalent to the discharge from the Nile River in one day. There is also an argument about the exact number of rivers in Lebanon notably that not all of the 14 rivers, which are discharging water all year long as it was the case in the past, and this gives the first indicator about the current bad status on these rivers. Thus, the adoption of this number (i.e. 14) has been derived from the morphometric characterization basis and catchment shapes of the existing perennial watercourses, even though this conflicts with their hydrology where water flow is now almost intermittent.

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#### *Hydrology*

There is remarkable hydrologic feature that characterizes the Lebanese rivers where all of them are almost controlled by the rugged topography, and then distributed within the three geomorphological units of Lebanon (i.e. Mount-Lebanon, Bekaa Plain and the Anti-Lebanon). Hence, Lebanon with its small area represents as a regional hydrologic junction where water flows into three regional directions. These are regional flows: 1) northward to comprise a tributary of the Orates River Flow System, 2) southward forming a major tributary for Jordan River Flow System and 3) eastward where the Lebanese Coastal Rivers System flow to the Mediterranean Sea [1].

towards the sea within the Lebanese territory. The fourth river (i.e. Hasbani-Wazzani River) is originated from Jabal Hermoun and then spans southward comprising the highest channel slope (40 m/km) of the four rivers. Except the Litani River, the other three rivers are Transboundary water resources.

Elaborating the dimensions and mapping of drainage systems, including the catchment and the streams inside, is usually applied as a primary phase for detailed hydrological analysis and surface water assessment. Therefore, the geometric and morphometric analysis are utmost significant in watershed management to presume, for example, site suitability for surface water accumulation and harvesting,

Drainage systems of Lebanon including rivers were extracted directly from the stereoscopic satellite images (i.e. SRTM DEM) where digital elevation models were generated by magnifying the pixel details, and then slopes were extracted to determine flow directions and then stream delineation. Therefore, the digital extraction of drainage systems enabled calculating a number of geometric and morphometric

Geometric measurements represent the calculations of the variables for the boundary of watershed (or catchment), and this will be totally separated from the properties of the streams (primary or secondary) included in the catchment. In this view, catchments with relatively large areas are usually subdivided into sub-

For Lebanon, the area of rivers catchments is small and averaging about 250 km<sup>2</sup> for the coastal rivers if excluding the Litani River, which is an inner-coastal river. Hence, the largest area belongs to this river (i.e. Litani) and the smallest one belongs

1.Basin maximum length (B*l*): This represents the maximum straight length of the catchment where it extends almost parallel to the primary watercourse,

BL is a function of water arrival time to reach the outlet, and thus it controls the time of leakage, evaporation, and transpiration **Table 1** shows the

2.Basin width (B*w*): The ratio of length of a catchment to its width significantly affects water flow to the outlet, thus when the difference between the length and width of a catchment is relatively low, that means the flow will be more regular and takes more time than it when this difference is high. For Lebanon,

3.Elongation Index (E*i*): This represents the ratio between the diameter of the circle with the same area (A) as the catchment, and the distance between the maximum two points (B*l*) in the catchment [3]. It is expressed by the formula:

*Ei* <sup>¼</sup> <sup>2</sup>√*<sup>A</sup>*

*Bl*√*<sup>π</sup>* (1)

agricultural projects, dams' construction, hydro-power sites, etc.

catchments, which is dependent of the purpose of study applied.

and it reflects the topographic orientation of a catchment

maximum length of catchments of the Lebanese rivers

the B*<sup>w</sup>* of rivers catchments are shown in **Table 1**.

**2. Watersheds of the Lebanese Rivers**

*DOI: http://dx.doi.org/10.5772/intechopen.94152*

*Rivers of Lebanon: Significant Water Resources under Threats*

**2.1 Geometry of the Lebanese rivers**

to Siniq River (**Figure 1** and **Table 1**).

measurements.

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Rivers in Lebanon have diverse orientations of distribution on terrain surfaces, and more specifically they are characterized by different flow directions and dimensions. Therefore, these rivers can be classified as follows:


**Figure 1.** *Rivers of Lebanon [1].*

towards the sea within the Lebanese territory. The fourth river (i.e. Hasbani-Wazzani River) is originated from Jabal Hermoun and then spans southward comprising the highest channel slope (40 m/km) of the four rivers. Except the Litani River, the other three rivers are Transboundary water resources.
