Date of Award
Doctor of Philosophy
Dr. Mohamed Sultan
Dr. William Sauck
Dr. Michelle Kominz
Dr. John Wahr
An integrated (space-borne and land-based gravity, aeromagnetic, GIS, and remote sensing) approach was developed, tested, and applied to investigate the following on regional scales (Africa) or local scales (El Qaa Plain, Sinai): (1) assess the capability of GRACE data (04/2002 to 08/2011) for monitoring elements of hydrologic systems on the sub-basin level (Task 1); (2) address the nature and the controlling factors (e.g., climatic and/or human pressure-related) affecting the inter-annual GRACE-derived Terrestrial Water Storage (TWS) trends over a large suite of hydrologic systems and domains in (Africa) (Task 2); and (3) identify the structural, geologic and hydrologic settings as well as quantify the characteristics (e.g., geometry, volume of water, depletion rates) of the El Qaa Plain aquifer (Task 3).
Findings (1-7) for Tasks 1 & 2 include: (1) observed temporal mass variations are largely controlled by elements of the hydrologic cycle; (2) large sectors of Africa are undergoing statistically significant variations (+36 mm/yr to –16 mm/yr) due to natural and man-made causes; (3) warming of the tropical Atlantic ocean intensified Atlantic monsoons and increased precipitation and TWS over western and central Africa’s coastal plains, proximal mountainous source areas, and inland areas, whereas warming in the central Indian Ocean decreased precipitation and TWS over eastern and southern Africa; (4) the high frequency of negative phases of the North Atlantic Oscillation (NAO) increased precipitation and TWS over northwest Africa; (5) deforestation in the Congo Basin decreased TWS in that area; (6) the construction of dams increased TWS in upstream Nile Valley countries; (7) consideration should be given to using GRACE TWS data as an alternative, viable index for measuring temporal and spatial variations in aridity. Findings (8 – 10) pertaining to structural, geologic and hydrologic settings and characteristics of El Qaa Plain (Task 3) include: (8) delineation of two connected sub-basins (average length: 48 km; average width: 16 km; maximum thickness: 3.75 km); (9) volume of water in storage was estimated at 40 to 56 km3; and (10) aquifers are being depleted through natural discharge and extraction at a rate of 19 x 106 m3/yr.
Ahmed Ahmed, Mohamed El Sayed, "Integrated Approach for Hydrogeologic Investigations in Africa: Inferences from Space-Borne and Land-Based Gravity, Aeromagnetic, GIS, and Remote Sensing Data" (2012). Dissertations. 94.