By Eva Mena Gil (EMUASA)
Part of the precipitation that falls (in the form of rain, snow or hail) flows over the land surface forming streams and rivers, which constitutes surface runoff. Another part infiltrates into the ground, filling pores and fissures: when these become saturated, the water flows by gravity into springs, rivers or seas, giving rise to groundwater runoff. Surface water and groundwater are closely related, as it is very common for groundwater to surface in springs and fountains to follow a surface course, while in other cases surface water infiltrates, becoming part of the groundwater.
Surface water infiltrates the ground through pores and cracks in the soil, until it reaches a certain depth where all the hollows are filled with water. This zone is called the zone of saturation or water table. The water table is defined as the surface that takes the points where the water pressure and atmospheric pressure are equal. In general, the water table has a relief like that of the surface, although it is softer and can even rise to the surface to form free water reservoirs.
Groundwater is located below the water table, saturating the pores of the soil, also known as the saturation zone. The water in transit in the coarser interstices (pores and crevices) of the soil is called gravitational water, usually located in the zone of saturation.
Above the water table, soil pores may contain air or water, called the aeration zone. The aeration zone contains hygroscopic water (adhering in a thin layer around the soil grains) and capillary water, also located in the smaller pores. Capillary water causes capillary tension in the saturated zone in the vicinity of the water table and partially saturated above.
Water in the ground can be at rest or in motion:
In the case of the city of Murcia, the river Segura, which passes through the city, causes the water table to be very high (less than 10 meters high), and this has consequences in the communities of neighbors where they have to install drainage pumps to eliminate the water that is generated in the garages. At present, this dewatered water from the garages is pumped and discharged to the sewage system, with the corresponding cost for the community of neighbors. Water from the phreatic is not polluted water, it is not wastewater and can be treated to obtain reclaimed water and give it other much more sustainable and environmentally correct uses.
Aguas de Murcia aims to promote the idea of using water from the phreatic by making a separate network or taking these drains from buildings before being discharged to sewerage and to use them for irrigation of parks and gardens. LIFE Conquer is one of the first steps towards this direction. This project, co-funded by the European Union, aims to promote the circular economy by developing a system for reusing groundwater infiltrated in residential areas, maintaining the necessary nutrients and eliminating salinity, for irrigation purposes in the city of Murcia.
Learn more about LIFE Conquer.