The consultant made observations in three test pits dug at different areas, in order to study their general behaviour, seepage rates and fish seed incursion by tidal influx.
Pit No. 1 (Fig. 5)
A good intertidal pit could be made in an old stone and concrete structure located at the rocky shore south east of Aqaba Hotel. This pit was at a low level and used to get submerged during high water phases. During low tide periods no seepage of water took place as the wall was well sealed with stones and concrete. Thus regular observations could be made in the same. Few juveniles of perches, limpets and small gastropods were collected from this pit on different occasions, at the turn of the high tide phases. However, the number of organisms collected was not appreciable, varying between 2 and 12. The perches collected were in the length range of 16–20 mm.
Fit Ho, 2 (Fig. 6)
The second pit was made initially at the mid-intertidal region on the beach of Palm Beach Hotel (Sector 1), but it was completely filled with sand in 5 days of spring high waters. Subsequently the site was shifted upwards so that sea water would enter only during the spring high tides. The sides of the pit were lined with stones and regular observations could be made in the same for two months.
An interesting condition observed in this pit was that during moderate high and low water phases the water inside was almost fresh, evidently being drained in from the sub-surface spring water reported to be present in the area. The water level in the pit fluctuated in relation to the level of sea water. During spring high waters, the pit water changed into highly brackish due to influx of sea water (Pig. 7). Detailed salinity measurements could not be made due to lack of facilities.
As could be expected in the sandy soil, the rate of seepage was very high, the intensity varying with the tidal level of sea water. The temperature of water in the pit showed fluctuations, but generally within reasonable limits, except when the water level was very low and when the sand became very hot during the latter half of May 1973. The temperature readings taken on a typical sunny day in April 1973 are given in Table 6.
No fish seed could be collected from this pit. However, plankton samples collected immediately after high tide influx of sea water showed the presence of a few copepods, amphipods and bivalve larvae.
Pit No. 3
The third test pit was made in a longitudinal depression on the beach at the Police Club compound in Yamaniyah. The sides of this pit were lined with cement concrete slabs readily available at the site. Regular observations were possible in this pit for about one month, after which it was filled up with sand as a result of unusually high waves in the sea. Subsequently a smaller pit was made at the same place in which observations were continued for five days. Further studies were not possible here due to erosion of the land between the sea and the pit.
The water in this test pit was very saline and the level fluctuated according to the sea level, indicating thereby that the seepage rate was very high.
Table 6
TEMPERATURE FLUCTUATIONS IN THE SEA AND TEST PIT OH A SUNNY DAY
| Mean temp. (° C) | ||||
| Time (hr) | Tidal phase | Air | Sea water | Water in pit |
| 06.00 | High water | 23 | 20.5 | 21.5 |
| 06.30 | " | 23 | 20.5 | 21.5 |
| 07 00 | " | 23.5 | 20.5 | 21.5 |
| 07.30 | " | 23.5 | 21 | 22 |
| 08 00 | Max. high water | 23.5 | 21 | 22.5 |
| 08 30 | Early low water | 24 | 21.5 | 23 |
| 09 00 | Low water | 25.5 | 21.5 | 23 |
| 09 30 | " | 26 | 21.5 | 23 |
| 10 00 | " | 28 | 22 | 23.5 |
| 10 30 | " | 28 | 22.5 | 23 |
| 11 00 | " | 29 | 22.5 | 23 |
| 11 30 | " | 30 | 22.5 | 24 |
| 12 00 | " | 29 | 23 | 24.5 |
| 12 30 | " | 28 | 23 | 25 |
| 13 00 | " | 27 | 23.5 | 25 |
| 13 30 | " | 28 | 23.5 | 25.5 |
| 14 00 | Max. low water | 28.5 | 23 | 26 |
| 14 30 | Early high water | 28.5 | 23 | 27 |
| 15 00 | High water | 29 | 23.5 | 27 |
| 15 30 | " | 28 | 23.5 | 26.5 |
| 16 00 | " | 28 | 23 | 26 |
| 16 30 | " | 26 | 23 | 25 |
| 17 00 | " | 26 | 23 | 24 |
| 17 30 | " | 25 | 23 | 24 |
Plankton samples collected from the longitudinal pit after high tide phase showed a concentration of algae and copepods. Three postlarvae of shrimps and seven juveniles of perches were collected from this pit on a single day.
Observations in a test pond
A shallow pond already dug at the Yamaniyah Police Club was made available for making observations, The bottom of this pond was at a higher level than that of Pit No. 3 and hence water used to remain in the same only during spring high water periods. Since further digging of the pond was not possible due to presence of rocks, a small pit was made at the bottom (Fig. 8) in which water used to be retained except during periods of very low water level in the sea. The water in the pond and pit was always saline. These observations showed that by increasing the depth of the pond sufficiently, water would be retained during all tidal phases.
