Recharge systems for protecting and enhancing groundwate

872
TOPIC 7
Sustainability of managing recharge systems / Arid zones water management
HYDROGEOCHEMICAL ASPECTS
Hydrogeochemical aspects of parts of the concerned aquifers are discussed through the hydrochemical analyses of
twenty three groundwater samples as well as two samples representing rainwater and Red Sea water (Table 3). They
reflect the following results :
1. Groundwater salinity : The groundwater salinity ranges from 438 mg/l (No. 6) to 10,409 mg/l (No. 15) indicating
a wide variation in quality from fresh to saline in the fractured basement rock aquifer (Hem, 1989). On the
other hand, the groundwater salinity varies from 459 mg/l (No. 19) to 1,292 mg/l (Nos. 20 and 21), reflecting
fresh to brackish water in the Nubia Sandstone aquifer (as they are closer to the watershed area).
2. Groundwater chemical types : The groundwater in the fractured basement aquifer is characterized by Na >
Ca(Mg) > Mg(Ca) / Cl > SO4(HCO3) > HCO3(SO4) ionic proportion. So, the groundwater chemical type is mainly
Cl–Na (Fig. 16), On the other hand, the ionic proportion; Na > Mg > Ca / HCO 3 (Cl) > Cl (HCO 3 ) > SO 4 characterises
the Nubia sandstone aquifer. Consequently, two chemical water types are recognized. The first type
HCO 3 –Na (Nos. 19 and 21), while the second type Cl–Na is detected at Abu Saafa area (Nos. 20 and 22), indicating
the final phase of groundwater metasomatism.
3. Salinity-major components relationships : The relation between salinity (TDS) and major components were
statistically illustrated (Figs. 8 and 9). According to these diagrams, a positive correlation between salinity
and concentration of ions is evident, since the increasing of major constituents leads to the increasing of total
Table 3. The hydrochemical analyses data (2004)
No. Water point pH TDS Units Ca Mg Na K CO3 HCO3 SO4 Cl
1 EL Gahelia well 8.10 438 Ppm 9.80 45.24 95 12 7.62 312.5 15 98
2 Eqat-a well 8.35 2368 Ppm 58.80 107.20 660 27 72.39 418.30 590 644
3 Eqat-b well 7.87 1600 Ppm 47.04 111.90 385 21 22.90 511.30 370 386.40
4 EL Beida-a well 7.18 2244 Ppm 135.20 69.54 600 10 Nil 230.12 200 1115
5 EL Beida-b well 7.13 8586 Ppm 594.10 290.10 2100 13 Nil 275 1100 4352
6 Madi well 7.95 511 Ppm 46.20 18.10 120 9 Nil 335 50 100.50
7 Meisah well 7.83 2750 Ppm 219.50 19.05 680 19 11.43 352.5 600 1024.80
8 Gomidlum well 7.12 4330 Ppm 712.10 160 550 15 Nil 49.70 950 1918
9 Aquamatra well 7.30 1111 Ppm 58.20 40.10 290 15 Nil 296 180 380.11
10 Mahareka well 7.87 1080 Ppm 113.68 38.10 220 10 3.81 143.30 135 448
11 Shoshab well 8.39 2980 Ppm 58.80 71.44 1000 7 15.24 267.30 140 1554
12 Sararah well 7.85 6967 Ppm 529.20 202.40 1700 23 15.24 286.60 1750 2604
13 Salalat Osar well 8.00 1096 Ppm 54.9 38.10 310 12 19.05 367.90 100 378
14 Sararat well 8.00 4776 Ppm 548.8 202.4 975 8 26.67 197.5 495 2422
15 Okak well 7.75 10409 Ppm 901.6 476.30 2400 7 11.43 205.30 800 5712
16 Eremit well 7.85 8537 Ppm 352.8 261.95 2500 6 15.24 344.70 100 5129.40
17 Frokeit-a well 7.30 1246 Ppm 40.50 63.17 350 11 Nil 288.14 150 488.14
18 Frokeit-b well 7.12 4786 Ppm 812.40 200 610 19 Nil 69.80 1100 2010
19 Ain Abraq 8.10 459 Ppm 54.88 35.72 75 8 3.81 351.40 15 91.10
20 Abu Saafa- a 7.10 1223 Ppm 44.10 65.12 310 12 Nil 310 100 537.10
21 Abu Saafa-b 7.30 1292 Ppm 27.25 22.40 430 11 Nil 599.10 230 272.10
22 Abu Saafa-c 7.11 1219 Ppm 88.15 67.14 250 14 Nil 265.10 230 438.10
23 EL Dif well 7.10 591 Ppm 59.20 44.12 100 17 Nil 365 40 148.50
- Rain water 7.86 155 ppm 10 9 21 2 Nil 63 14 31
- Sea water 7.96 38120 ppm 439 1343 12000 380 18 137 2300 21568
Note: TDS in mg/l.
ISMAR 2005 ■ AQUIFER RECHARGE ■ 5th International Symposium ■ 10 –16 June 2005, Berlin