Recharge systems for protecting and enhancing groundwate

786
TOPIC 7
Sustainability of managing recharge systems / MAR strategies
The hydrographic basins in the study area are of high potentiality of flash flooding and short time interval between
the beginning of rise and peak discharge. The flash floods in the study area are expected in future seasonal rainfall.
Floods hazard mitigation
The industrial projects and settlements at basins outlets are threatened by flash floods. (e.g. Economic area at North
West Gulf of Suez, tourist projects & the main desert highways).
For this sake, precautionary measures should be taken into account to prohibit or at least minimize the flood damage
with the concomitant increase in seepage/runoff ratio. The following is a brief description and discussion of the
flood damage mitigation measurements (Figure 5).
1. Wadi South Hagul basin
This basin occupies a rather circular shape with an area of about 56.1 km 2 . The basin drains low terraces with
low slope ratio. The high flash flood events in Wadi South Hagul occurred in 1988, 1990, 1991 and 1998 with
runoff rates of 0.47, 0.43, 0.40, and 0.35 millions m 3 /h and a volume of water accumulation of about 0.36, 0.62,
0.39 and 0.35 millions m 3 . The water seepage rate is 0.08 x 10 6 m 3 /h, which gives good chance for a large part
of flood water to percolate through the surface soil to the under ground. W. South Hagul have high surface area
of soil (about 100%) (Figure 3), the runoff water can be exploited by the construction of small boulder detention
dams (Grigg and Helmeg, 1975); to replenish the groundwater aquifers (Figures 5 and 6).
2. Wadi Hammtih basin
This basin is of the fifth order; it has an area of about 207 km 2 and drains G. Attaqa high tableland. It is of hexagonal
shape and has high difference of elevation between the upstream and downstream. The trunk of W. Hammtih
flows easterly to south southeasterly towards the Gulf of Suez. Massive Eocene Limestone with only small outcrops
of Miocene dominates the lithology of its floor, whereas the Quaternary deposits (variable soil) expose near
the mouth (Abu El Nasr, 1979). The seepage and surface runoff relationship shows the high water accumulation
in Wadi Hammtih of about 0.24, 0.57, 1.36, 1.46, 1.78 and 2.22 millions m 3 in 1997, 1992, 1988, 1991, 1998,
and 1990, respectively. Wadi Hammtih is characterized by high runoff rate when it is compared with the seepage
rate (0.17 x 10 6 m 3 /h). (Figure 5) shows the possibilities of the floods in all last seasons in the period from 1978
to 1998 (Figure 5). To protect those leading tributaries, detention dams should be constructed to increase the
seepage/runoff ratio (Figure 6).
3. Wadi Hagul basin
Wadi Hagul is hexagonal to circular in shape. It is of fifth order and has an area of about 293 km 2 . Rugged mountainous
relief (up to 450– 900 m) and sharp slope on the main stream characterize the basin.
The main trunk flows to Gulf of Suez at the southeast. Wadi Hagul also is characterized by low seepage rate
and the base floor is composed of Pliocene clays and limy mud. High flooding episode of 3.25 x 10 6 m 3 occurred
in 1990 with runoff of rate 2.25 x 10 6 m 3 /h, where the seepage rate is 0.71 x 10 6 m 3 /h (Figure 5). This in turn
increases the flash floods potentiality with the low groundwater replenishment. Construction of artificial dykes,
dams and open lakes is an urgent demand for storing water (Figure 6). This water will recover the deficiency in
groundwater.
4. Wadi Badaa basin
This basin has an area of about 658 km2 and high percentage of soil area of about 24.31% of its total area
ISMAR 2005 ■ AQUIFER RECHARGE ■ 5th International Symposium ■ 10 –16 June 2005, Berlin