In this study, abstraction, desalination and recharge method and SEAWAT numerical model are used to investigate seawater intrusion repulsion in a hypothetical two-dimensional coastal aquifer to understand the relation of seawater intrusion with abstraction, desalination and recharge parameters (i.e. abstraction/recharge rate, wells distance and depth). Abstraction, desalination and recharge consists of abstraction and desalination of brackish water and recharge of desalinated water. The results of different defined scenarios showed that increase of recharge rate has a significant effect on the seawater intrusion mitigation (e.g. more than 80% variation in saline water volume) while the increase of abstraction rate does not have specific impact on seawater recession (e.g. less than 3% variation in toe position). The method efficiency in reducing seawater intrusion is increased when freshwater is recharged by well at outside of saltwater wedge and close to its toe position. Moreover, it is shown that the abstraction, desalination and recharge performance has slightly improved when the recharge and extraction wells are placed deeper into aquifer and close to aquifer bottom (almost 15% for all characteristics of salt wedge). Ultimately, dilution of saline water with recharged freshwater will widen the mixing zone but as salt wedge recedes toward the sea simultaneously, the mixing zone thickness cannot follow the steady reduction trend.

Synthetic aperture radar (SAR) reveals a valuable contribution to ship detection due to its all-weather and all-illumination sensing capabilities. In this paper, a new polarimetric SAR (PolSAR) ship detector is proposed that jointly exploits sub-look scattering properties of point-like scatterers (i.e. ships) and polarimetric information. The detector, which is physically based on the concepts of coherent scatterers and polarimetric signatures, consists of four main steps: first, polarimetric signatures are extracted for each sub-look image; then, the correlation coefficient (CC) between the sub-look images is calculated for varying polarization bases; ship detection is performed by setting a threshold on the resulting CC image and finally, morphological filters are applied to delineate the contour of the detected ships and automatically generate the number of targets detected. The exploitation of polarimetric information through the polarimetric signatures, on one side provides more discriminative information about target and makes the detector more robust and accurate, on the other side, it increases the computation time. The detector’s performance is verified against actual L- and C-band PolSAR datasets. Experimental results demonstrate that the proposed detector outperforms state-of-the-art ones and it results in an area under the receiver operating characteristic (ROC) curve that ranges between 0.93 and 0.95.

Prediction of seawater intrusion (SWI) will increase the proper planning for withdrawal of groundwater, and it will help the freshwater management in the future. Since heterogeneous aquifers are more widespread than homogeneous one, this study aims to use the density-dependent SEAWAT code to investigate the influence of different combinations of hydraulic conductivity (K) on SWI. The effects of numbers and arrangement of layers with different K are examined on (a) toe position, (b) freshwater–seawater mixing zone thickness (W_t) and (c) leakage from adjacent layers in a steady-state condition. For this purpose, numerous scenarios with different K were simulated and analyzed. The results of horizontally layered aquifers showed that the streamlines are broken on boundary of layers. It was observed that when K is decreased, especially at the middle layer, the refraction angle is increased and consequently W_t is increased. The W_t in vertically layered cases was less than horizontally layered aquifers because of less streamline breakage. Also, random arrangement of K directs the saline flow to higher permeability zones. Thus, the SWI extent in this type of aquifer was more tangible than other types. Because of the difference in hydraulic head at layer borders, the seepage rate significantly increases nearby toe position and the dominant direction is upward. However, in the steady-state condition, the type of flow did not differ significantly for boundary cells of layers at the vicinity of toe position.