Researchers collected groundwater
samples to analyse them on a monthly basis for three years. They found out that
seawater intrusion is directly related to the pumping period. Also, it is weakly
linked to the rainfall. Many
researchers studied the coastal karstic aquifers in Crete and Greece.
Karterakis and many other researchers used the classical linear programing and the
heuristic optimization mythologies in order to study the groundwater management
problem in Crete aquifer in 2007. In order to study the effect of active pumping wells on
the evolution of the seawater intrusion front along the coastline, researchers
conducted a sensitivity analysis. A researchers called Koukadaki among his
colleagues estimated the hydraulic conductivity from field measurements of
electrical conductivity near the city of Heraklio in Crete in 2007. There are several ways to obtain
the hydraulic heads. Yet, researchers chose the estimated hydraulic
conductivities. Researchers
used the GhydenHerzberg equation after the calibration in order to locate the
freshwater/saltwater interface. The researchers Shammas and Thunvik used a three dimensional
numerical model for the flow and the solute transport for the management of the
Salalah aquifer in 2009. In order to predict the possible future demand of
groundwater supply for the next 15 years, predictive simulation of the aquifer
was conducted under some transient condition.

 

Researchers conducted many
experiments in order to find out that the best scenario for predicting the
groundwater levels and groundwater salinity for the year 2020. A researcher
called Datta utilized a 3D, transient, density dependent finite element model,
FEMWATER, for modelling of two Mandals which are administrative units in
Nellore District, Andhara Pradesh, India in 2009.

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In order to evaluate the
effect of different pumping strategies for controlling the seawater intrusion,
they used the above mentioned model. Researchers found out that a well-planned
pumping strategy can adjust the seawater intrusion process and the spatial and
temporal concentration distribution. There are several conditions in order to control the
seawater intrusion in coastal aquifers such as maintaining a seaward hydraulic
gradient and enabling a proportion of the fresh-water to flow into the sea.

The risks of seawater
intrusion leads to limit the development of coastal aquifer for water
supply.  The acceptable ultimate landward
extent of the seawater intrusion and the allowable discharge of freshwater to
the sea dominates the management of the coastal aquifer.

Many researchers have
investigated the problem of pumping optimization using many simulation
techniques. Gordon and some other researchers used a combined scheme of
groundwater simulation models and optimization methods in 2000. There are
different objective functions and groups of constraints have been applied based
on the problem. Some
researchers called Cheng and Mantoglou wanted to maximize the total pumping
rate in 2000 and 2003. However, Das and Datta hoped to minimize the salinity of
pumped water in 1999. Other
researchers called Emch, Yeh and Gordon included the pumping cost in the
objective function in 1998 and 2000. Maximizing the objective function
subjected to many constraints which are normally calculated through governing
differential equations is the crucial purpose of any optimization problem.

There are physical processes
which govern seawater intrusion in the coastal aquifers. These processes are
well understood. There are different methods to develop the governing equations
of flow and salinity transport in coastal aquifers and solving them numerically
(Huyacorn et al. 1987; Sherif et al. 1988; Andersen et al. 1988; Essaid 1990;
Bear et al. 1999; Gambolati et al. 1999; Oude 2001).

There is a common approach
for simulation of seawater intrusion in coastal aquifers. It is based on the
sharp interface approximation and the Ghyben– Herzberg relation (Essaid 1990;
Bear et al. 1999; Essaid 1999). Researchers like Emch and Yeh, Cheng, Ouazar,
Cheng and Mantoglou in 1998, 1999, 2000 and 2003 presented many coastal aquifer
management models based on the sharp interface approximation.

There are complicated seawater
intrusion models which consider the transport processes which takes place in the
mixing zone (Das and Datta 1999; Gordon et al. 2000).

Moreover, the numerical
groundwater flow and the solute transport models can be used to estimate the
hydraulic parameters (e.g. Ebraheem et al. 2002, 2003; Sefelnasr 2007); and
predict the aquifer responses for the different pumping scenarios and climate
conditions (e.g. Sherif and Singh 1999; Gossel et al. 2004, 2008). These type of models can be used
 to simulate the fluctuations of the
seawater-freshwater interface and the transition zone as a result for the
groundwater pumping, groundwater evaporation, salt dissolution in coastal
Sabkhas, climatic change, etc. (Sherif and Singh 1996; Kacimov and Sherif 2006;
Kacimov et al. 2006, 2009, Sherif and Kacimov 2005).

 

 

 

Werner among other
researchers presented a fundamental evaluation for the coastal aquifer
management paradigms. They used the published coastal aquifer case studies and
a simple evaluation of the Uley South coastal aquifer, South Australia in 2011.
In order to minimize the risk of coastal groundwater degradation and to
underpin the strategies for future aquifer management and better operation,
there are trigger-level and flux-based approaches be adopted conjunctively

 

Abd-Elhamid and Javadi
presented a cost effective method in order to control the seawater intrusion in
the coastal aquifers in 2011. The methodology includes an abstraction of the saline
water and the recharging to the aquifer after the desalination.

In order to develop the
simulation of fluid flow, solute transport and simulate seawater intrusion, A
coupled transient density-dependent finite element model. The model was
integrated with an optimization model in order to examine the three scenarios
to control seawater intrusion which includes abstraction, recharge and a
combination system.

 

The results were illustrated
as the following:-

First of all, the combined
system performed clearly better than using the abstraction or recharging wells
alone since it had the least cost and the least salt concentration in the
aquifer. The main
purpose of the paper is to simulate the seawater intrusion phenomenon in the
coastal aquifer of Wadi Ham, UAE and analyse the impact of the different
scenarios of the groundwater pumping as it has been discussed throughout the
paper. The summary
of the best scenario and model for simulating the seawater intrusion phenomenon
in the coastal aquifer and the groundwater pumping is found below. Firstly, the
MODFLOW is employed to simulate the groundwater flow in the aquifer.  Secondly, the calibration model and the
verification model were performed before using the MT3D to simulate the
seawater intrusion, analyses its current level and explains the effects of
several pumping scenarios. All simulations were conducted in a two-dimensional
horizontal view. Thus, the impact of density variation on flow and solute
transport is ignored. The results contribute to a better groundwater management
in Wadi Ham coastal aquifer and other similar aquifers located in arid regions.