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Ahydrogeological characterization of the Ezousas alluvial aquifer, located in SW Cyprus, has been conducted to assess its suitability for groundwater recharge with 5 Mm 3  a −1 of chlorinated disinfected tertiary treated sewage effluent from the Paphos Municipality Wastewater Treatment Plant. We present results from a 3 year field study conducted to establish the regional groundwater regime and to define the aquifer hydrology. New drillings at selected locations were made to provide reliable information about the aquifer dimensions and boundaries. Pumping and constant-head permeability tests were used to estimate the key hydraulic properties of the aquifer system. The storage capacity was assessed to be 4.2 Mm 3 . The bedrock of the aquifer, in its approach to the sea, was found to be some 40 m below sea level, thus indicating the potential for seawater intrusion. A monitoring programme consisting of recording piezometric heads and electrical conductivities was used to observe the position of the seawater–freshwater interface, so that rates of abstraction and recharge could be determined, to maintain a stable interface. The quality of the treated sewage effluent, and of native and abstracted groundwater, was continuously assessed in terms of salinity, heavy metals, persistent organic compounds and microbiota, to optimize the quality of the downstream groundwater used for local irrigation.

Two Integrated Surface water - Groundwater flow Models (ISGMs) have been developed at the National Technical University of Athens (NTUA), Greece and Cardiff University (CU), UK to investigate surface water-groundwater interactions. The models are based on physical processes and are capable of describing more accurately the recharge and discharge flow paths between surface and ground waters. The NTUA ISGM consists of a 3-D surface water flow sub-model (FLOW-3DL) and a 3-D saturated groundwater flow sub-model. The CU ISGM is based on the 2-D surface water model DIVAST, which has been extended to include 2-D saturated groundwater flow. Both models use the finite difference method and orthogonal grids. The momentum and mass conservation equations are the governing equations for both surface and groundwater flows. The ISGMs have been applied to two simple cases and their results have been compared to computations using only surface water models (FLOW-3DL and DIVAST) to demonstrate the need to use ISGMs for accurate and satisfactory calculations. Furthermore, the results of the two ISGMs are compared for a channel, which fully penetrates an aquifer. The two ISGMs show a similar behaviour; the NTUA ISGM exhibits a slightly slower response of the aquifer water levels to the water level changes in the channel than the CU ISGM.

Managed Aquifer Recharge (MAR) is becoming an increasingly attractive water management option, especially in semiarid areas. Nevertheless, field studies on the fate and transport of priority substances, heavy metals and pharmaceutical products within the recharged aquifer are rare. Based on the above, the objective of this project is to study the hydrological conditions of the coastal aquifer of Ezousa (Cyprus) and its ability to attenuate pollutants. The Ezousa riverbed is a locally important aquifer used for a MAR project where treated effluent from the Paphos Waste Water Treatment Plant is recharged into the aquifer through a number of artificial ponds along the riverbed. Additionally, groundwater is pumped for irrigation purposes from wells located nearby. The hydrological conditions of the area are unique due to the construction of the Kannaviou dam in 2005 that reduced natural recharge of the Ezousa aquifer significantly, inducing the saltwater intrusion phenomenon. A three-dimensional finite element model of the area was constructed using the FEFLOW software to simulate the groundwater flow conditions and transport of Phosphorous and cooper in the subsurface from the recharge process. The model was calibrated using hydraulic head and chemical data for the time period of 2002-2011. The groundwater model was coupled with a geochemical model PHREEQC attempting to evaluate nitrate and Copper processes. Inverse modeling calculation was used to determine sets of moles transfers of phases that are attributed to the water composition change in groundwater between the mixture of natural groundwater and reclaimed wastewater and the final water composition.

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