Hydrogeology and water resources

Libya is known for its extensive global groundwater basin of fossil water. This resource is stored in the Nubian Sandstone Aquifer System (NSAS), one of the world’s largest underground water sources. The aquifer stretches across North Africa, covering parts of Libya, Egypt, Sudan, and Chad. The NSAS is estimated to hold around 150,000 cubic kilometers of water, with Libya possessing the largest share (Salem and Pallas Reference Salem and Pallas2004). Groundwater storage in Africa relies on effective porosity and saturated aquifer thickness. Panel (a) shows a map of groundwater storage, expressed as water depth in millimeters, compared with modern annual recharge (Doll and Fiedler Reference Döll and Fiedler2008). Panel (b) displays the volume of groundwater storage for each country, with error bars derived from recalculating storage using the full ranges of effective porosity and aquifer thickness (Fig. 3), instead of relying only on the best estimate. The annual renewable freshwater availability (FAO 2022), a common metric in water scarcity assessments, is also included for comparison.

Figure 3.

A. Groundwater storage in Africa is based on effective porosity and B. saturated aquifer thickness (Doll and Fiedler Reference Döll and Fiedler2008).

As a transboundary basin, the NSAS crosses several countries. This raises issues related to the fair use and management of the aquifer’s resources. The United Nations stresses the importance of international cooperation to ensure sustainable management and fair resource sharing. Libya depends heavily on its fossil water, especially for agriculture, a vital part of its economy. However, excessive use of these resources has raised concerns about depletion and the potential effects on future generations. Recently, efforts have focused on shifting towards more sustainable water sources, such as desalination and wastewater reuse (Fig. 4), (Global Water Intelligence 2016 and FAO AQUASTAT 2022). Overall, the NSAS is a vital resource for Libya and its neighbouring countries, and its sustainable management requires cooperation and careful planning to ensure equitable use and preservation for future generations.

Figure 4.

Water resources as a percentage of total by country (FAO AQUASTAT 2022).

Renewable water resources

Libya’s total renewable water resources amount to 105 cubic metres per capita per year (m³/c/yr)(287 litres per capita per day – lpcd), ranking it as the eighth lowest in the Middle East and North Africa (MENA) region (among 20 countries). This is lower than the MENA average (283 m³/c/yr) and global levels (3,247 m³/c/yr) (FAO 2022; UNICEF 2022).

The availability of less than 500 m³/c/yr of renewable water resources indicates absolute water scarcity according to the Falkenmark Water Stress Index. Total renewable water resources per capita decreased by 11 percent between 2007 and 2018 (FAO 2022). Libya’s total internal renewable water resources equal its total renewable water resources, since it receives no renewable water resources from neighbouring countries (FAO 2022). Fig 5., from the FAO country profile for Libya (2016), illustrates the total water withdrawal per percentage in Libya.

Figure 5.

Water withdrawal by percentage in Libya.

Transboundary waters

Libya possesses no renewable surface water resources originating from neighbouring countries, resulting in a dependency ratio of 0 percent (FAO 2022). However, several transboundary aquifer basins exist, including the North-Western Sahara Aquifer System (NWSAS), which covers Libya with a total area of 1,280,000 km2 (Algeria, Libya and Tunisia); the System Aquifer of Djeffara covers Tunisia and Libya with over 16,627 km2; and the Nubian Sandstone Aquifer System (NSAS) covers Chad, Libya and Sudan with an area of over 2,890,000 km2 (MacDonald et al. Reference MacDonald, Bonsor, Dochartaigh and Taylor2012; IGRAC 2022) (Fig. 6).

Figure 6.

Libyan Transboundary Aquifer Systems.

Water consumption

Libya’s total water consumption per capita is 873 m³/c/yr (2392 lpcd), ranking it fourth highest in the MENA region, with per capita consumption exceeding the MENA average (889 lpcd) and the global level (784 lpcd) (FAO 2022; AQUASTAT 2016) (Fig. 7). Agricultural consumption accounts for 1,990 lpcd, ranking fourth highest in the MENA region and exceeding the MENA and global levels of 691 lpcd and 477 lpcd, respectively (FAO 2022).

Figure 7.

Water withdrawals, by source, as a percentage of total withdrawals, by country (AQUASTAT 2016).

Industrial consumption is 115 lpcd, ranking fifth highest in the MENA region and exceeding MENA and global levels of 28 lpcd and 60 lpcd, respectively (FAO 2022). According to the Voluntary National Review (VNR 2020), average municipal consumption is 415 lpcd, exceeding both the MENA and global levels of 125 lpcd and 160 lpcd, respectively. Higher rates have been recorded in many locations, such as Greater Tripoli (450 lpcd) (VNR 2020). Agricultural consumption accounts for 83.1 percent of total freshwater resources and ranks fourth highest in the MENA region, exceeding the MENA (77.9 percent) and global (1.9 percent) levels (FAO 2022). Domestic water demand is projected to increase by 39.5 percent between 2010 and 2030 (Table 2).

Table 2

AQUASTAT indicators on water resources for Libya

Water use efficiency

For Libya, water use efficiency for the industry, irrigation and service sectors is 59 US$/m³, 0.02 US$/m³ and 12 US$/m³, respectively. Water use efficiency for the agricultural and service sectors is below the MENA and global levels (AQUASTAT, FAO 2022). More than 82.5 percent of the total water budget is used for irrigation (Fig. 4) (FAO country profile book, Libya 2016).

Water stress and related concepts

Water stress describes the challenges or limitations in meeting the water needs of both people and the environment. Unlike the narrower focus of water scarcity, water stress encompasses various physical factors such as water scarcity, quality, environmental needs and access. The Water Stress Index (WSI), introduced by Falkenmark in 1974, measures the ratio of total freshwater used by major sectors to the total renewable freshwater resources, after accounting for necessary environmental flows. It is calculated using the following formula:

\begin{equation*}\text{WSI }(\% ) = \frac{\text{TFWW}}{\text{TRWR} - \text{EFR}} \times 100\end{equation*}

(TFWW) = 5.7X10⁹ m³, (TRWR) = 0.7X10⁹ m³, (EFR)=1.3X10⁹ m³

\begin{equation*}\text{RWS in Libya } (\% )= \frac{\text{TFWW}}{\text{TRWR} - \text{EFR}} \times 100 = 817.14 (\% ) \end{equation*}

Where TFWW = 5.7X109 m³, TRWR = 0.7X109 m³ and EFR = 1.3X109 m³.

The resulting WSI for Libya is = 817.14%

Water risk involves the chance that a business or organization may face negative impacts due to water-related issues. Different sectors and organizations often view this risk in various ways, even when dealing with similar levels of water scarcity or stress. Common factors such as water scarcity, pollution, poor governance, insufficient infrastructure and climate change create risks across multiple sectors. According to data from the World Bank and AQUASTAT (2022), Libya ranks the worst in terms of unsustainable water use, showing the highest percentage of water resources being withdrawn unsustainably (see Fig. 5).

Groundwater depletion and infrastructure challenges

Groundwater is a crucial water source for many regions, but when too much is extracted, it can run out, leading to serious water shortages. This measure looks at how fast groundwater levels are dropping in Libya. Also, the quality and availability of water heavily depend on infrastructure such as dams, reservoirs, irrigation systems and wastewater treatment plants. The effectiveness of these facilities plays a big role in how well a region manages its water.

Reasons behind water depletion

In Libya, water shortages are also linked to how much wastewater is safely treated – the country lags behind other nations in this area, according to UN Water and WHO reports from 2021. Many factors contribute to this problem, including overusing groundwater, climate change and deforestation. Other issues such as pollution, seawater intrusion, high water demand, poor water storage, reduced rainfall and urban growth all make the situation worse. As water demand keeps rising, Libya faces increasing depletion, which threatens both the environment and the people who depend on it.

One of the biggest causes of water loss is the overuse of groundwater. Although groundwater – especially ancient, fossil water – is a valuable resource, it is often tapped faster than it can replenish itself. This leads to the shrinking of underground water reserves, which interferes with farming, industry and daily life. Climate change is also making things worse by changing rainfall patterns and increasing evaporation, which leads to droughts and water shortages. Deforestation adds to the problem since trees are vital for maintaining the water cycle. Without enough trees, soil erosion happens and the land loses its ability to hold onto water, creating a vicious cycle of depletion and environmental degradation.

Groundwater contamination and septic tank impacts

Groundwater contamination occurs when pollutants enter and accumulate in groundwater, the water located beneath the Earth’s surface in porous rocks or soil. Contamination sources can be natural or human and include industrial waste, agricultural chemicals, sewage and other chemicals. In Fig 9. Libya has the lowest wastewater flow and treatment coverage in the region, according to WHO (2021), Fig. 8.

Figure 8.

Wastewater flow and treatment by countries UN Water and WHO (2021).

Figure 9.

Impact of septic system on groundwater quality (US EPA 2001).

Common causes of groundwater contamination include:

leaking underground storage tanks;

improper disposal of hazardous waste;

agricultural activities (pesticide and fertilizer use), landfills, and waste disposal sites;

industrial activities (manufacturing and mining operations).

Groundwater contamination has severe consequences for both human health and the environment. Contaminated groundwater can cause illnesses, such as cancer, and other health problems if consumed or used for domestic purposes. It also harms ecosystems, including lakes, rivers, and wetlands, and endangers aquatic and terrestrial wildlife.

Poorly designed septic tanks significantly impact groundwater pollution (US EPA 2001) (Fig. 9). Septic tanks treat wastewater in areas not connected to public sewer systems and in areas with unplanned construction, like most Libyan cities. These tanks separate solid waste from liquid waste, allowing the liquid to seep into the soil for further treatment.

In Libya, the situation is compounded by the lack of a thick soil profile and the high diffusivity of sandy soil, which facilitates flow in porous media. However, if a septic tank is not designed properly or maintained adequately, it can lead to groundwater pollution.

This occurs when liquid waste from the septic tank leaches into the surrounding soil, contaminating the groundwater. Factors contributing to poor septic tank design include inadequate sizing, improper location, or lack of maintenance. For instance, an undersized septic tank can become overloaded, causing backups or leaks. Locating a tank too close to a well or in an area with a shallow water table also elevates contamination risks.

Lack of maintenance can cause solid waste to accumulate in the tank, leading to blockages and system failure if the tank is not pumped regularly. This can result in untreated wastewater entering the surrounding soil and groundwater.

Overall, poorly designed septic tanks have substantial impacts on groundwater pollution. To prevent contamination, septic tanks must be designed properly, located appropriately, and maintained regularly, in addition to regular inspections and maintenance to ensure the system functions correctly and is connected to the main public sanitation network.

Mass transport in groundwater and the threat of seawater intrusion

Mass transport in groundwater is all about how different substances – such as pollutants, chemicals, or nutrients – move through underground water systems. Groundwater, which is stored beneath the Earth’s surface in porous rocks or soil, moves through processes such as diffusion (where molecules spread from areas of high to low concentration), advection (the movement of water and dissolved substances driven by pressure differences) and dispersion (the spreading of substances because of the unevenness in underground formations) (Freeze and Cherry Reference Freeze and Cherry1990; Yu and Li Reference Yu and Li2019). Contaminants like pesticides, fertilizers, hydrocarbons, and industrial chemicals can hitch a ride with groundwater, and their movement can have serious consequences for both the environment and public health.

It is really important to understand how these substances travel underground. This knowledge helps us to keep an eye on water quality, track down pollution sources, and take action to prevent or reduce contamination.

Another major concern, especially along coastlines, is seawater intrusion. This occurs when heavy groundwater pumping from wells near the coast (see Fig. 10) creates a cone of depression underground. This depression pulls salty seawater from the Mediterranean Sea into the freshwater aquifers, leading to contamination (USGS 2006). When seawater mixes with freshwater, it turns the water salty and undrinkable, making it unsuitable for human use and agriculture. It also affects ecosystems because many local plants and animals are adapted to freshwater environments and cannot survive in saltier conditions.

Figure 10.

Seawater intrusion (USGS 2006).

To prevent seawater from invading freshwater supplies, careful management is essential. This might include reducing the amount of water pumped, increasing the natural recharge of aquifers or using alternative water sources such as desalination or recycled water. Proper management of groundwater is especially critical in coastal areas to protect these vital resources for future generations.

Saltwater intrusion and Sabkha regions

Sabkha regions are flat, arid coastal plains characterized by the accumulation of evaporite minerals like salt and gypsum. These regions often have high water tables, which can lead to the intrusion of brine water and saltwater into groundwater resources, degrading water quality in Wahat areas such as Jalu and Ojela and Taourgha, where water quality ranges from brackish to saltwater.

Brine water, with high concentrations of dissolved salts (typically more than 35,000 parts per million – ppm) (Reid, G.W. Reference Reid1974), has a significant negative impact on groundwater aquifers when it enters the system. One of the primary negative impacts is the contamination of the groundwater supply. Brine water intrusion increases groundwater salinity, rendering it unsuitable for drinking or agricultural use.

Additionally, brine water can carry heavy metals or radioactive isotopes, further degrading groundwater quality. However, brine water is a significant disaster in the Libyan Sahara Desert, especially near oil fields and concessions, as disposal of oil-water extracts from wells during oil extraction creates large exposed lagoons, sometimes exceeding thousands of square kilometres. This type of brine water carries many isotopes, heavy and trace elements and hydrocarbons. These toxic components undergo deep percolation and diffuse through porous media into the main fossil water basin system. Overall, the impact of brine water on a groundwater aquifer depends on factors such as the type and concentration of salts, the geology of the aquifer, and the hydrological conditions of the area, Fig 11.

Figure 11.

Brine water ponds in Zelten oil fields, Libya.

Understanding water scarcity

Water scarcity is about whether there is enough water to meet the needs of people and ecosystems in a particular area. It is usually measured by comparing how much water people use versus how much water is actually available. This is a straightforward, objective fact that we can measure consistently across different regions and over time.

To help visualize this, Figure 12 (adapted from Falkenmark Reference Falkenmark1989) shows different levels of water competition. Each cube represents 1 million cubic metres of water available each year in land-based water sources, and each dot shows 100 people who rely on that water. When we calculate the Water Scarcity Index (WSI), Table 3 (Damkjaer, S. and Taylor, R. Reference Damkjaer and Taylor2017), we take the total water flow and divide it by the number of people competing for it.

Figure 12.

Water stress index (Falkenmark Reference Falkenmark1989).

Table 3

Water stress index (Damkjaer, S., Taylor, Reference Damkjaer and Taylor2017)

^a flow unit in the column for inverted WSI is equal to 10⁶ m³ to get contemporary WSI, one flow unit must be divided by the number of people competing for this water

So, a higher WSI indicates more water available per person, while a lower WSI suggests water is running out or is under heavy demand.

Types of water scarcity

Water scarcity is not the same everywhere – there are different kinds, each with its own causes and challenges.

Physical water scarcity

This happens when a region simply does not have enough water to meet the needs of its people because of natural factors such as low rainfall, high evaporation, or limited access to freshwater sources. For example, arid areas such as parts of Libya or semi-arid northern regions often face this challenge. In fact, Libya is classified as an entirely dry land (Fig. 13), which highlights how severe its water scarcity is on a national scale, according to the water stress index (FAO AQUASTAT 2014).

Figure 13.

Water scarcity map (FAO AQUASTAT 2014; Damkjaer and Taylor Reference Damkjaer and Taylor2017).

Economic water scarcity

Here, water is technically available, but it is too expensive or difficult for people to access because of poor infrastructure, high energy costs, or limited financial resources. Developing countries often experience this kind of scarcity. Libya, with its fragile infrastructure, is a good example of economic water scarcity – water exists but is hard to reach or afford.

Institutional water scarcity

This type occurs when laws, policies, or regulations block or limit access to water. For instance, conflicts over water rights, unfair distribution systems,or policies that do not favour equitable access can create institutional barriers. A map of Africa (2014) based on the water stress index shows how institutional issues can make water access uneven across the continent. In Libya, the Man-Made River (MMR, Fig. 13) – a massive underground pipeline system – has helped provide water from southern aquifers to coastal cities like Tripoli and Benghazi, covering up to 1,600 km and supplying about 70 percent of the country’s freshwater. While the project has addressed some immediate needs, it has also caused problems, including population displacement, inefficient water usage, environmental damage and even land subsidence due to excessive pumping. Many southern residents have moved to coastal cities, creating overcrowding.

Additionally, overpumping has led to groundwater depletion, drying up oases and damaging agriculture.

There is also a lack of awareness among Libyans about water conservation and responsible usage.

Social water scarcity

This occurs when certain groups cannot access water because of social or economic reasons –poverty, discrimination or unfair resource distribution. In conflict areas like war-torn Libya, vulnerable populations such as women, children and indigenous communities often face the worst.During Libya’s second civil war (2014–2020), the country’s water infrastructure, including the MMR, was severely neglected. In 2019 over 100 wells were dismantled and in 2020 armed groups seized control of a key water station, cutting off water to more than two million people, especially in Tripoli and nearby towns. Each type of water scarcity presents its own challenges and requires tailored solutions to ensure everyone’s access to clean, safe water.

Water scarcity indicators

Water scarcity indicators are crucial because this is a serious issue in Libya, particularly given its location in arid to semi-arid regions. Key indicators include:

• • Water Stress Index (WSI): this indicator measures the ratio of water withdrawals to renewable water resources in a given region. A ratio greater than 1 signifies that the region is experiencing water stress.

• • National-Scale Per Capita Freshwater Availability: this measures national-scale per capita freshwater availability in African countries using data from the year 2014 (FAO AQUASTAT; Damkjaer and Taylor Reference Damkjaer and Taylor2017).

Causes of water scarcity in Libya

Water scarcity in any country is driven by multifaceted and interlinked factors. This section analyses Libya’s complex context by presenting key drivers within the commonly accepted global framework on water scarcity.

Virtual water and water footprint

Virtual water is the hidden amount of water used to produce goods and services – such as the water needed to grow crops or manufacture products – that consumers usually do not see. The water footprint measures how much water an individual, organization or country uses to produce the goods and services they consume. Both concepts are essential tools in tackling global water shortages. Countries with limited water resources can reduce pressure by importing water-intensive products from countries that have plenty of water.

However, relying too much on virtual water imports makes nations vulnerable to changes in global markets and water availability elsewhere (Mekonnen Reference Mekonnen and Hoekstra2011) and (Allan Reference Allan2011), Fig. 14. By calculating the water footprint of products and activities, individuals, companies and governments can make smarter, more sustainable choices – such as reducing unnecessary water use. It also helps policymakers understand where and how water is being used across different sectors, so they can create better strategies to conserve this vital resource.

Figure 14.

Water footprint for dairy products (Mekonnen Reference Mekonnen and Hoekstra2011).

Recommendations

• • Diversify water sources by investing more in desalination plants along the coast and establishing wider wastewater reuse programmes. Support for research and development of innovative water harvesting and storage methods should be a priority.

• • Develop new technologies that enable safe and efficient groundwater storage, minimizing leaks and reducing depletion. Ongoing research is essential to discover better techniques.

• • Plant more trees, especially native, drought-resistant species. Trees help increase groundwater levels and prevent soil erosion, creating a healthier water cycle. Launch community-based afforestation projects and involve local residents in planting trees. Education efforts on the vital role of forests for water conservation are also key.

• • Use the concepts of virtual water and water footprint to help manage water resources better. By importing water-heavy products from water-rich regions, Libya can save its limited local water supply for essential needs. Consider creating policies that encourage importing water-intensive goods from countries with abundant water.

• • Implementing economic tools such as tariffs and subsidies can also stimulate the local production of products that require less water.