Introduction
Study area
Sampling and analytical procedure
Rainwater and groundwater sampling and monitoring
Chemical and isotopic measurements
Results
Isotopic composition of meteoric waters
Station | ID | Month | Precipitation (mm) | δ18O [‰] | δ2H [‰] | 3H [TU] |
---|---|---|---|---|---|---|
Dakar-Yoff | DKYSI | June July August | 10.5 42.6 149.6 | −4.34 | −25.6 | 2.1 |
DKYS2 | September October | 220.8 6.4 | −7.33 | −48.5 | 2.4 | |
Dakar-Hann | DKHS1 | July August | 45.5 113 | −5.37 | −33.4 | 2.4 |
DKHS2 | September October | 115.5 13.5 | −6.89 | −44.5 | 2.8 | |
Bel–Air | BELS1 | July August | 65.4 134.6 | −4.58 | −27.1 | 2.4 |
BELS2 | September October | 106.7 7.8 | −6.24 | −39.8 | 1.9 | |
Thiaroye | THARS1 | July August | 278 154 | −4.75 | −30.5 | 2.0 |
THARS2 | September October | 143.0 10.0 | −5.76 | −36.5 | 1.9 | |
Guediawaye | GUEDS1 | August | 78.5 | −4.49 | −27.6 | 2.6 |
GUEDS2 | September | 166.5 | −6.50 | −43.9 | 2.5 | |
Mbao | MBAOS1 | July August | 76.2 175.6 | −4.81 | −28.8 | 2.0 |
MBAOS2 | September | 30.6 | −6.39 | −40.9 | 1.5 | |
Bambilor | BAMBS1 | July August | 65.9 147.3 | −3.93 | −25.4 | 2.2 |
BAMBS2 | September October | 18.0 6.0 | −7.08 | −47.3 | 2.7 | |
Kayar | KAYS1 | July August | 58.0 160.0 | −4.84 | −30.8 | 2.0 |
KAYS2 | September | 109.0 | −7.62 | −51.4 | 2.3 |
Isotopic composition of groundwaters
Well No. | Well ID | Well type | Site | Depth [m] | T [°C] | pH | EC [μS/cm] | δ18O [‰] | δ2H[‰] | 3H [TU] |
---|---|---|---|---|---|---|---|---|---|---|
1 | P02 | DW | Déni B. Ndao | 8.49 | 26.1 | 5.82 | 2,530 | −3.31 | −26.6 | 2.5 |
2 | P109 | DW | Santhiane | 12.27 | 25.9 | 7.1 | 108 | −4.51 | −36.3 | 2.4 |
3 | P128 | DW | Wayambame | 9.20 | 27.6 | 6.9 | 720 | −5.09 | −38.1 | 4.8 |
4 | P202 | DW | Kounoun | 5.75 | 24.4 | 6.62 | 4,770 | −3.27 | −28.4 | 2.1 |
5 | P209 | DW | Bayakh | 14.56 | 24.8 | 7.04 | 665 | −4.64 | −34.6 | <0.8 |
6 | P210 | DW | Dar. B. Sylla | 8.71 | 26.6 | 5,73 | 238 | −4.16 | −31.6 | 4.3 |
7 | P215 | DW | Golam | 7 | 25,6 | 6.52 | 739 | −4.64 | −34.6 | 5.1 |
8 | P232 | DW | Kaniack | 6.86 | 26.8 | 6.20 | 305 | −4.49 | −33.2 | 2.5 |
9 | P234 | DW | Kayar | 1.51 | 26.7 | 7.40 | 2,000 | −3.47 | −26.7 | 3.5 |
10 | P213 | DW | K. Ab. Ndoye | 4.36 | 28 | 5.90 | 3,169 | −4.77 | −31.6 | – |
11 | P221 | DW | Diender | 10.72 | 27.3 | 6.79 | 826 | −3.89 | −33.5 | – |
12 | P235 | DW | Bambilor | 5.07 | 24.5 | 7.29 | 3,180 | −3.87 | −29.5 | 2.1 |
13 | P2–10 | PZ | Gouy Guewel | 8.77 | 28.9 | 6.90 | 1,993 | −4,4 | −33.5 | 1.1 |
14 | P2–7 | PZ | Tivao. Peulh | 7.58 | 27.8 | 7.87 | 584 | −3,58 | −28.2 | 2.4 |
15 | P2–9 | PZ | Niaga Peulh | 4.40 | 23.8 | 7.95 | 556 | −2.21 | −25.2 | 2.1 |
16 | P2–5 | PZ | Corn. Guedia | 4.55 | 30.6 | 7.42 | 1,465 | −1.51 | −18,9 | 2.3 |
17 | P2–6 | PZ | Boune | 3.27 | 26 | 6.46 | 1,497 | −5.08 | −33.2 | 2.1 |
18 | P2–3 | PZ | Crois. Bethio | 13.59 | 29 | 8.21 | 690 | −4.76 | −37 | 3.5 |
19 | P2–2 | PZ | Cambérène | 5.58 | 30.2 | 6.90 | 1,784 | −4.35 | −37 | 2.5 |
20 | P2–8 | PZ | Tivao. Peulh | 5.59 | 26.1 | 7.90 | 649 | −4.40 | −34.7 | <1.2 |
21 | P3–4 | PZ | Malika | 0.76 | 27.7 | 9.92 | 198 | −5.65 | −38.2 | – |
22 | P19 | DW | Warouwaye | 3.71 | 27.8 | 5.46 | 738 | −4.67 | −31.8 | – |
23 | PS4 | PZ | S. Mame Gor | 6.97 | 24.2 | 5.56 | 608 | −2.34 | −26.7 | 2.3 |
24 | PS5 | PZ | Mbawane | 4.96 | 24.2 | 7.97 | 418 | −3.37 | −30.1 | 2.0 |
25 | PS6 | PZ | S. Mame Gor | 4.12 | 25.4 | 6.30 | 236 | −2.91 | −29.7 | 3.8 |
26 | PS7 | PZ | Kayar | 1,69 | 31 | 7.55 | 607 | −2.93 | −30.6 | 5 |
27 | PS10 | PZ | Gouy Guewel | 4.82 | 24.6 | 6.02 | 363 | −2.78 | −32.4 | 5.3 |
28 | PS11 | PZ | Gorom I | 5.26 | 25.4 | 5.13 | 861 | −2.81 | −28.3 | 3.1 |
29 | P1(Techno) | PZ | Technopole | 1.31 | 22.9 | 6.80 | 1,772 | −2.13 | −22.3 | 1.5 |
30 | P3–1 | PZ | Thiaroyes/mer | 2.22 | 26.4 | 6.62 | 1,060 | −4.67 | −32.8 | 1.3 |
31 | P3–2 | PZ | C. M. Thiar | 1.2 | 24.7 | 6.31 | 1,797 | −3.46 | −28.8 | 3.0 |
32 | Pts 58 | DW | Mbeubeuss | 3.70 | 25.9 | 5.2 | 1,766 | −4.24 | −33.7 | 2.3 |
33 | P21 | PZ | Yeumbeul | 3.98 | 28 | 3.89 | 2,890 | −4.10 | 32.6 | 2.2 |
34 | Pz 4 | PZ | Pikine | 0.87 | 24.7 | 6.03 | 2,850 | −4.06 | −32.7 | 3.0 |
35 | Pts 58 bis | DW | Mbeubeuss | 9.73 | 26.8 | 5.52 | 556 | −3.89 | −33.3 | 2.9 |
36 | F17 | BH | Thiaroye | 0.57 | 29.6 | 4.88 | 1,687 | −4.64 | −33.8 | 2.6 |
37 | F19 | BH | Thiaroye | 5.34 | 28.6 | 4.83 | 2,100 | −4.71 | −33.9 | 2.1 |
38 | F22 | BH | Thiaroye | 0.21 | 29.1 | 5.12 | 1,956 | −4.72 | −35.0 | 2.2 |
39 | P120 | DW | Wayabam | 7.31 | 27 | 6.2 | 634 | −4.41 | −33.7 | 2.8 |
40 | PS1 | PZ | Sangalkam | 7.35 | 26.2 | 6.7 | 141 | −3.83 | −32.1 | 4.1 |
Well No. | Well ID | Well type | Site | Depth [m] | T [°C] | pH | EC [μS/cm | δ18O [‰] | δ2H [‰] |
---|---|---|---|---|---|---|---|---|---|
1 | P02 | DW | Déni B. Ndao | 4.74 | 28.6 | 8.0 | 2,660 | −3.60 | −26.4 |
2 | P109 | DW | Santhiane | 6.95 | 28.0 | 8.4 | 690 | −4.64 | −34.6 |
3 | P128 | DW | Wayambame | 9.97 | 28.9 | 8.2 | 690 | −5.21 | −37.0 |
4 | P202 | DW | Kounoun | 1.60 | 31.0 | 6.6 | 2,130 | −3.70 | −28.6 |
5 | P209 | DW | Bayakh | 14.81 | 30.1 | 8.0 | 830 | −4.79 | −32.7 |
6 | P210 | DW | Dar. B. Sylla | 9.21 | 29.6 | 8.0 | 448 | −3.77 | −31.0 |
7b | P215bis | DW | Golam | 6.08 | 32.0 | 8.4 | 321 | −4.63 | −34.6 |
8 | P232 | DW | Kaniack | 6.86 | 24.5 | 6.6 | 1,112 | −4.35 | −32.5 |
9b | P234bis | DW | Kayar | 1.65 | 29.2 | 8.6 | 1,980 | −4.38 | −27.2 |
13 | P2–10 | PZ | Gouy Guewel | 9.55 | 29.2 | 8.5 | 1,670 | −5.21 | −34.6 |
15 | P2–9 | PZ | Niaga Peulh | 4.98 | 29.6 | 8.9 | 1,460 | −4.50 | −32.2 |
17 | P2–6 | PZ | Boune | 2.25 | 29 | 8.0 | 3,850 | −3.82 | −28.3 |
23 | PS4 | PZ | S. Mame Gor | 3.90 | 32.9 | 6.7 | 1,260 | −4.73 | −33.7 |
24 | PS5 | PZ | Mbawane | 1.92 | 29.8 | 8.6 | 409 | −4.60 | −32.9 |
27 | PS10 | PZ | Gouy Guewel | 4.20 | 29.7 | 8.3 | 664 | −4.70 | −33.7 |
28 | PS11 | PZ | Gorom I | 4.30 | 29.4 | 5.2 | 230 | −5.18 | −34.4 |
30 | P3–1 | PZ | Thiaroyes/mer | 1.32 | 28.1 | 8.7 | 2,290 | −0.63 | −12.1 |
32 | Pts 58 | DW | Mbeubeuss | 3.50 | 28.3 | 7.2 | 2,540 | −4.28 | −29.9 |
35 | Pts 58 bis | DW | Mbeubeuss | 3.70 | 29.0 | 8.0 | 1,440 | −2.61 | −21.2 |
37 | F19 | BH | Thiaroye | 1.40 | 29.0 | 7.5 | 2,430 | −4.83 | −31.7 |
38 | F22 | BH | Thiaroye | 1.50 | 28.6 | 7.0 | 2,680 | −4.11 | −33.3 |
39 | P120 | DW | Wayambame | 8.20 | 28.6 | 8.0 | 1,820 | −4.99 | −34.6 |
40 | PS1 | PZ | Sangalkam | 4.50 | 29.3 | 8.4 | 1,540 | −4.98 | −34.6 |
48 | F21 | BH | Thiaroye | 2.46 | 29.6 | 6.7 | 2,700 | −4.62 | −32.8 |
49 | F30 | BH | Thiaroye | 1.94 | 30.0 | 8.6 | 1,130 | −2.22 | −17.6 |
50 | F31 | BH | Thiaroye | 2.04 | 30.6 | 8.3 | 2,660 | −4.07 | −25.9 |
51 | PTS/PD5 | DW | K. Massar | 3.90 | 28.7 | 8.1 | 2,010 | −3.30 | −28.6 |
52 | PTS3 | DW | K. Massar | 1.10 | 28.7 | 8.5 | 2,280 | −3.47 | −28.2 |
53 | PTS4 | DW | K. Massar | 1.80 | 27.8 | 8.7 | 1,560 | −4.21 | −31.8 |
54 | PTS9 | DW | Yeumbeul N. | 3.80 | 29.0 | 7.7 | 2,020 | −3.10 | −24.3 |
55 | PD1 | MP | M. Gounass | – | 31.5 | 8.4 | 970 | −5.04 | −31.3 |
56 | PD2 | MP | M. Gounass | – | 30.0 | 7.9 | 2,720 | −3.58 | −24.5 |
57 | PD3 | MP | Yeumbeul S. | – | 29.4 | 8.1 | 2,570 | −3.18 | −22.4 |
58 | PTS14 | DW | Yeumbeul S. | 3.00 | 30.3 | 7.9 | 2,080 | −4.04 | −29.8 |
59 | PTS2 | DW | Djiddah T. K. | 1.40 | 29.6 | 8.3 | 3,090 | −3.00 | −24.0 |
60 | PTS01 | DW | Tivaouane P. | 6.20 | 29.2 | 9.1 | 660 | −4.76 | −32.2 |
62 | PTS8 | DW | Yeumbeul N. | 2.60 | 29.6 | 8.8 | 3,260 | −1.64 | −18.4 |
63 | PTS5 | DW | Keur Massar | 4.80 | 28.1 | 7.8 | 2,040 | −1.20 | −14.6 |
64 | PD6 | MP | Malika | – | 30.1 | 7.8 | 1,780 | −0.39 | −10.1 |
65 | PTS10 | DW | Sicab Mbao | 0.80 | 27.7 | 8.6 | 3,140 | −0.82 | −11.5 |
66 | PTS12 | DW | Sicab Mbao | −1.30 | 30.2 | 8.5 | 2,280 | −0.97 | −14.4 |
67 | PTS15 | DW | Mbao | 0.50 | 30.6 | 9.7 | 2,530 | −0.79 | −10.6 |
68 | PTS16 | DW | Mbao | 1.10 | 30.0 | 8.8 | 1,061 | −1.82 | −19.9 |
Observed hydrological responses to monsoonal rainfall
Discussion
Tracing the origin of rainfall generating groundwater recharge
Tracing groundwater flow
Equation |
n
| Data range (‰) | Mean composition (‰) | Spatial distribution | ||
---|---|---|---|---|---|---|
Min (δ18O, δ2H) | Max (δ18O, δ2H) | δ18O | δ2H | |||
δ2H = 4.85 · δ18O –10.65 | 27 | (−5.35, −37.2) | (−0.82, −11.50) | −3.86 | −28.9 | South-western part: peri-urban groundwater |
δ2H = 3.95 · δ18O –15.36 | 14 | (−5.21, −38.1) | (−2.21, −25.2) | −4.37 | −32.6 | Northern coastal zone |
δ2H = 2.82 · δ18O –20.37 | 24 | (−4.01, −33.7) | (−0.34, −10.10) | −2.88 | −25.0 | Niayes zones |
δ2H = 2.90 · δ18O –19.12 | 19 | (−5.18, −36.3) | (−2.78, −26.40) | −4.12 | −31.8 | South–north eastern part |