Because of the geological history of the Kingdom, large groundwater resources were formed many thousands of years ago. The Kingdom’s vast fossil or “non-renewable” groundwater resources are stored in a thick sequence of sedimentary aquifers that cover the entire eastern part of the country (the Arabian Shelf). The part of these water resources that is within reach of present-day extraction technology and that is not brackish or saline is called the “exploitable groundwater resources”. The sum of exploitable groundwater stored in all aquifers has been estimated at 2360 BCM. This figure shows a volume of water stored deep underground that is generally non-renewable in terms of precipitation recharge. Only a small portion of the rainfall infiltrates and reaches some of the primary and secondary aquifers. Estimates put the total amount of annual recharge at about 3 BCM.

There are 8 principal aquifer groups and 5 secondary aquifers with some local significance. Principal aquifers on the other hand are very extensive, some of them reaching from the northern boundary southwards into the Rub al Khali desert, and eastwards from the central area of the Peninsula to the Arabian Gulf. In the Eastern region several aquifers are present on top of each other, often separated by less permeable geological formations that slow down interactions between aquifers but do not stop them.  

Today more than 80% of the country’s water demand is met through groundwater withdrawals, servicing principally the agriculture sector. The remaining portion of the demand was met with surface water and desalinated water as well as a small contribution from treated
 

Municipalities demand more potable water every year as a result of population growth, continuous economic development and greater urbanization. The demand for water is concentrated in a few large urban areas accounting for almost half of the total population. The other half is dispersed all over the territory in hundreds of medium and small size towns and villages with varying levels of service.

In 2012, about 2,527 mcm of water were distributed through the municipal networks and water tankers to households and commercial units to meet a growing demand

The water source varies throughout the territory. Desalinated water is prevalent along the coasts, surface water in the south-west region and groundwater elsewhere. Nearly 61 percent of the water supply comes from  desalination. The remaining 39 percent comes mostly from groundwater and a small portion from reservoirs (surface water). The contribution of treated sewage for irrigation of urban green spaces is still small.

In 2012, close to 1,545 mcm of desalinated water was supplied by public and private plants to major urban areas. The contribution of desalinated water to public supply has been increasing every year when compared to other sources (6 to 8 percent in the last two years). Percentages of desalinated water versus other sources supplied on each province are indicated in the following figure. Most notable are the Makkah figures, where public supply is based 100 percent on desalinated water. Two other provinces, Asir and Madinah, also rank very high in consumption of desalinated water, with  87 and 86 percent, respectively. 
 

With around 4M m3/day of desalination capacity, Saudi Arabia is the largest desalination market in the world. These numbers grew significantly with the addition of Ras Al Khair (MSF part) and will grow further once Yanbu 3 (550K m3/day) is commissioned.

RO technology comprises half of the total desalination capacity, mostly for commercial or industrial uses, and in small units. MSF and MED technologies account for the other half of the desalination capacity and are mostly used in large plants (>100,000 m³/day). Some of these are cogeneration plants and are mainly installed by SWCC.

Large plants are dominant in the Kingdom, and while most are installed by SWCC, some are Independent Water and Power Producers (IWPPs).

Feed water for desalination plants consists mostly of seawater (~75%), with a strong emphasis on brackish water as well. 

SWCC operates the water transmission system in the Kingdom which consist of several interrelated pipelines reservoirs and pumping stations

The transmission network consists of a number of major systems, the network is around 7,175 km long, with pipelines varying in diameter between 8 and 80 inches

To ensure continued and consistent water flow in the system across large distances and changing topologies in the country, 56 pumping stations are strategically positioned across the network as well as 285 storage tanks, with a storage capacity of 12.6M m3

• NWC, currently in charge of water supply and sanitation in the cities of Riyadh, Jeddah, Mecca and Taif (in partnership with foreign private operators)
• Regional directorates under the governance of MEWA

• District cooling
• Construction, Mining & Industrial
• Agriculture
• Irrigation and Landscaping