  We consider the management of sloping, long and thin, coastal aquifers. We
first develop a simple mathematical model, based on Darcy flow for porous
media, which gives the water table height, and the flow velocity as a function
of the underground seepage rate, the recharge rates and the extraction rates,
neglecting sea water intrusion. We then validate the model with recent data
from the Germasogeia aquifer which caters for most of the water demand in the
area of Limassol, Cyprus. The data is provided over a three year period by the
Cyprus Water Development Department (WDD), the governmental department managing
the aquifer. Furthermore, based on our model, we subsequently develop an
optimised recharge strategy and identify the optimal recharge rates for a
desired extracted water volume while the water table height is maintained at
the acceptable level. We study several scenarios of practical interest and we
find that we can achieve considerable water savings, compared to the current
empirical strategy followed by WDD. Additionally, we model the transport of
pollutants in the aquifer in the case of accidental leakage, using an
advection-diffusion equation. We find that in the case of an undetected and
unhindered contamination (worst case scenario) the aquifer would get polluted
in about three years. Also, we find that double recharge rates flush the
pollutant out of the aquifer faster. Finally, to incorporate the possibility of
sea water intrusion, which can render aquifers unusable, we develop a new,
transient two-dimensional model of groundwater flow based on the Darcy-Brinkman
equations, and determine the position of the water table and the
seawater-freshwater interface for conditions of drought, moderate rainfall and
flooding. The validation of the new seawater intrusion modelling approach has
been carried out via comparison with a widely-accepted code.
