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Groundwater Management of the Iullemeden Aquifer System.

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Presentation on theme: "Groundwater Management of the Iullemeden Aquifer System."— Presentation transcript:


2 Groundwater Management of the Iullemeden Aquifer System

3 Contents Geometry and boundary conditions of model Recharge estimation Discharges Piezometry Water balance Conclusions

4 Iullemmeden Basin

5 Geometry and Boundary Conditions Sokoto Niamey Kano Nguru Maiduguri LAKE TCHAD Massif de lAïr Adrar des Iforas Detroit Soudanaise Rift Oriental Gao Tombouctou Cristallin Rock Primary Argiles dIrhazer Ci -Ch Marin Cretaceous Ct B A

6 Primary Argiles dIrhazer - Serie Izegouandane Continental intercalaire - Continental hamadien Marine and Lacustrine Upper Cretaceous Continental Terminal ( Greigert,1979) Paleocene - Ypresian Iullemmeden aquifer system West of Massif de lAïr

7 123456789 11 12 13 14 15 16 17 18 19 Term IV Term V Calcaires et argiles à Libycoceras ismaeli TermVI-VII Argiles sableuses Sables à Cocodriliens Paleocene (Sokoto Group) Upper sandstones and mudstones Lower sandstones and mudstones Term III Term I Mosasaurus shalesTerm II Calc. à Neobilites Calc. à Nigecigeras Série Calc. Blancs Série Marnes et Calcaires Upper Cretaceous Marine and Lacustrine Formations / Paleocene - Ypresian Rima Group

8 Gundumi - Illo Rima Ci -Ch Sokoto Terms IV and V Terms VI and VII GwanduCt1 Ct2 Ct3Gwandu Terms I to III [Cr6-5] to [Cr7] NigeriaNiger / Mali Ct1 Ct2 Ct3 Lower sedimentary complex Model

9 Boundary Conditions Sokoto Niamey Kano Nguru Maiduguri LAKE TCHAD Massif de lAïr Detroit Soudanaise Adrar des Iforas Rift Oriental Gao Tombouctou Cristallin Rock Primary Argiles dIrhazer Ci -Ch Marine Cretaceous Ct Agades Zinder Taouardeï Anefis Greigert,1961 Greigert and Pougnet,1967 Greigert,1979 Ogilbee andAnderson, 1965/1973 Oteze, 1976 Radier,1959 Pallas, 1971

10 Bottom of lower sedimentary complex

11 Top of lower sedimentary complex

12 Top of CT1 (blue)

13 Top of CT2 (orange)

14 Top of CT3 (yellow)

15 Recharge Single most important figure for sustainable management. Water balance methods and Darcy formula notoriously inaccurate (factor of 10) Environmental tracers can often be better (factor of 2-3) Tracers used: Tritium, Tritium- 3 He, CFC (Freons), SF 6, Chloride Remote sensing info combined with groundwater flow and transport models allow to test hypotheses on recharge mechanisms (areal and concentrated recharge) Use of precipitation and evapotranspiration maps obtained with RS methods can help at delineating zones

16 Sampling for CFC in groundwater (Niger)


18 Tritium Concentration in Rainwater

19 u = L/ delay L Principle of Age Dating With Tracers Result: Pore velocity With porosity we obtain specific flux q = nu With area we obtain total flux Q = qA

20 Evapotranspiration for the 5th March 1992 calculated from NOAA-AVHRR using SEBAL mm/d

21 Precipitation map from METEOSAT (Example 1-10 June 1995) mm/10d 0° – 10° East 10° – 20° North

22 Tritium corrected to 1985 related to depth to the water table 0


24 Tritium in wells (1967-2000)

25 NDVI from Landsat TM of Feb. 1986

26 NDVI Spot image 30.9.96

27 Survey of Mares (from satellite image)

28 Survey of Mares (ground truth /satellite)





33 Population Distribution in the Iullemmeden or more Inhabitants/km 2 Estimated water consumption 50 l/person/day

34 Vertical Distribution of Abstractions by Wells

35 Discharge by Evapotranspiration Potential ET –2000 mm/a Digital terrain model Extinction depth for evapotranspiration –up to 50 m Evaporation by vapour transport (Coudrain-Ribstein) –E = 71.7 z -1.49 (E in mm/a, z in m) –in Iullemmeden basin negligible

36 Piezometry of CI (observed)

37 Piezometry of CT1 (observed)

38 Piezometry of CT2 (observed)


40 Piezometry of CI (computed)

41 Piezometry of CT1 (computed)

42 Piezometry of CT2 (computed)

43 Groundwater balance (first rough estimate from model) - 50 m 3 /s + 70 m 3 /s - 10 m 3 /s

44 Conclusions 1 Model concept available due to previous work Mechanisms of recharge can only be identified in more local studies, generalization to the total area requires related remote sensing data Distributed input data such as discharges rely heavily on proxi data such as population maps, soil maps and remote sensing data Accuracy of model fluxes still has to verified. In this task environmental tracers are useful

45 Conclusions 2 Presently overexploitation has not yet started New technology can help to do a better job in resource assessment than has been possible in the past Besides the donor driven activities in Niger which lead to a large number of new wells a strategic consideration of the whole is necessary

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