Previous surveys and excavations at the site have shown that the citadel was built by the Umayyad caliph ‘Abd al-Malak (685–705 CE) in the late seventh century CE, on the remains of a Byzantine settlement. The compound was part of a system of coastal defenses in Filastin (Palestine/Israel) that was intended to prevent Byzantine raids from the sea. The system included a series of ribāts (citadels and fortresses) and mahrases (coastal towers) that maintained visual contact with each other and could signal danger and call for reinforcements from the district capital of Ramla (Masarwa 2006). The citadel was apparently destroyed in an earthquake that struck in 1033 CE and subsequently deserted. In the Crusader period, it was renovated and reoccupied, and its name was changed to Castel Broar. It was finally abandoned following the expulsion of the Crusaders from the country in 1290 CE. Later nomads used the buildings for temporary shelter. Remains of the citadel’s walls that were built of dressed kurkar stones enclosed a rectangular area (c. 40 × 60 m), were preserved at the site. Two stories of storerooms and other rooms were built within the citadel walls. The structure had two entrances: a land-gate in the east and a sea-gate in the west. Round towers were constructed in the western corners of the citadel and on either side of the gates in the east and west. The towers in the eastern corners were square. Two wells were discovered in the northern and southern parts of the citadel’s courtyard. Four steps ascended to a platform (height c. 1 m) that was built above the southern well (L515). Two marble columns that were probably in secondary use stood next to the platform; they were apparently used to support a pumping installation. A reservoir dug south of the well was filled with rainwater conveyed in ceramic gutters. The well shaft was previously excavated down to the water table (HA-ESI 112:101*–103*; Fig. 2).
Reconstruction of Ancient Sea Levels on the Basis of Ancient Wells
Sea level is one of the indicators of global climate change. Generally speaking, the sea level drops during cold periods, and during hot periods the glaciers melt, their water flows to the oceans and the sea level rises. A relative sea level at each coastal site is an adjusted calculation of the average sea level and vertical movements of the land. The relative tectonic stability and the low rhythm isostacy of the country’s coastal strip make it possible to associate the changes in the relative sea level with changes in the volume of water that have their origins in global and regional factors. Y. Nir of the Geological Survey of Israel developed a method whereby it is possible to draw conclusions regarding ancient sea levels on the basis of the depth of wells located up to 100 m from the shoreline, in a strip where the fresh groundwater floats on the saline groundwater due to differences in density. Ancient wells were dug to a depth that allowed for a delicate balance between maintaining a minimal height (40 ± 5 cm) so as to immerse a vessel for drawing water during the driest periods and the salinization of the well with seawater.
Measurements and Finds
The round well (diam. c. 1.1 m) was built of twenty-eight kurkar stone courses. Slots (depth c. 5 cm, width c. 10 cm; Fig. 3) were hewn opposite each other in each of its courses for the entire length of the shaft. The wellhead was 5.2 m above the MSL, and the bottom course was 28 cm below the MSL. At the bottom of the shaft were several potsherds, most of which were non-diagnostic, including a shoulder of a saqiye jar that is dated to the Early Islamic period and was discovered underneath one of the stones in the bottom course. A layer of flat beach-rock was discovered on the bottom of the well. 
The well was presumably dug when the ribāt was constructed during the reign of the caliph ‘Abd al-Malak. The citadel required a large quantity of drinking water for the people and animals that resided within it and in its immediate surroundings. The uniformity in the construction of the well’s shaft shows that its original depth was preserved and it does not appear to have been renovated over the years. The opposing slots that run the length of the shaft served as tracks for a saqiye pumping installation that was assembled on top of the marble columns. The layer of beach-rock was placed at the bottom of the well so as to improve the quality of the water and reduce turbidity, i.e., muddying the water with sand during pumping. Presumably, the water drawn from the well was conveyed through a pool where the sand could settle and then flowed to the reservoir to its south. During low tide the level of the groundwater was probably lower than the pumping threshold; hence the saqiye installation was operated during high tide, to fill the reservoir south of the well.

Masarwa, Y. 2006. From a Word of God to Archaeological Monuments: A Historical-Archaeological Study of the Umayyad Ribāts of Palestine. Ph.D. Dissertation. Princeton University.
Nachlieli D. 2008. Ashdod Yam. In E. Stern, H. Geva and A. Paris, eds. The New Encyclopedia of Archaeological Excavations in the Holy Land 5, Supplementary Volume. Jerusalem. Pp. 1575–1576.