Water samples were collected from drillings, different sources and wells belonging to the plioquaternary and turonian aquifers in the study region and the piezometric map of the Essaouira synclinal basin (Morocco) was prepared. Electric conductivity as well as 18O, 2H and 3H concentrations of water samples were measured. A meteoric local line was determined and compared with the world meteoric line. The radiocarbon ages of the studied aquifers were evaluated. Recharge of the main aquifers in the study region was investigated. It has been shown by this study that the recharge rate of the deep turonian aquifer is too low, which may cause a shortage of water supply to the Essaouira city and its surrounding region. Based on the study, it is suggested that the Moroccan authorities, considering the drought in the region during the past few years, must envisage building small dams on the Ksob river for a better management of floodwaters, which are presently let into the Atlantic ocean.
Population
growth and climate change, resulting in long periods of drought,
are forcing many countries throughout the world to intensively
increase the exploitation of their water sources for domestic,
agricultural (irrigation) and industrial purposes. Due to
the scarcity of surface waters, people mainly exploit underground
water reservoirs. Hence, it is necessary to study and characterize
these water reservoirs to avoid any excess exploitation. All
waters have fingerprints of naturally occurring isotopes that
provide information about their origin. Among the most powerful
fingerprinting tools are the ratios of stable isotopes of
hydrogen-deuterium to hydrogen (2H/1H)
and of oxygen 18 to oxygen 16 (18O/16O)
(Bourg et al., 2001; D'Alessandro et al., 2004).
Naturally occurring radioactive isotopes provide information
about the age of groundwaters, which refers to the last time
the water was in contact with the atmosphere. In the present
work, stable and radioactive isotopes are used for characterizing
water resources in the arid and semi-arid coastal zone of
Essaouira (Morocco).
The
region studied, called Essaouira synclinal zone, belongs to
the Essaouira basin (Bahir et al., 2000). It has a
surface area of about 300 km² and is bordered by the
Ksob River in the north, Tidzi River in the south, Tidzi diapir
in the east and Atlantic Ocean in the west. This
region is less fractured and characterized by low hills with
a less dense hydrographic network. |
