الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
 |  | from | 16 |  |  |
| | | from | 16 | | |
Abstract
Water scarcity in Sinai is a major problem, which hamper most developmental activities. South Sinai arid region is characterized by relatively heavy rainfall storms, which cause flash floods with high velocities, low duration, even with some catastrophic events. When flash floods occur, the usual practice is to dispose the flood water into the Sea without any benefit, except for a small portion that can be stored in the existing reservoirs.
The study area is located in southwestern part of Sinai Peninsula and is represented by Wadi Fierran and Wadi El-Aawag watersheds. These watersheds are promising areas in water potentialities, where they receive large amounts of rainfall through different times. They are promising areas for urban and agricultural expansions.
This work comprises a particular approach involving the integration of geographic information system (GIS), remote sensing (RS), watershed modeling (WMS) and weighted spatial probability modeling (WSPM) to identify the suitable sites for increasing the possibilities of groundwater recharge by runoff water. Geological, hydrogeological, hydrochemical, climatological and geomorphological studies were investigated through the present work to understand how to control flash flood and use its water in maximizing groundwater recharge possibilities and to mitigate flash flood hazards in the study area.
A detailed hydro-morphometric analysis was performed for Wadi Fierran and W. El-Aawag watersheds to throw lights on the potential areas suitable for the runoff water harvesting (RWH), which will have its own bearing on the groundwater recharge. The sub-watershed boundaries and hydro-morphometric parameters were delineated using the ASTER DEM and Spot-4 satellite image mosaic by the WMS 8.0© Software. Morphological characterization was carried out through the measurement of linear, areal and relief aspects illustrated their correspondence with the hydrologic behavior of the sub-watersheds. W. Fierran is classified into twenty three sub-watersheds, whereas W. El-Aawag is subdivided into twelve sub-watersheds.
The multi-criteria decision support system (MCDSS) was conducted inside the ArcGIS 10.1© software to produce WSPM models for determining the potential sites for the RWH. The harvested runoff water was managed to increase the groundwater recharge possibilities. The model was constructed by spatially integrating eight thematic layers of: volume of annual flood (VAF), maximum flow distance (MFD), overland flow distance (OFD), drainage density (DD) and/or drainage frequency (DF), basin slope (BS), basin area (BA), basin infiltration number (IF) and basin length (BL).
Three WSPMs scenarios were generated, where the model was running three times by using criteria of: (1) equal weights, (2) weights proposed by the authors’ and (3) weights justified by the sensitivity analysis. The performed WSPMs segregated each watershed into five potential classes for the RWH potentiality, which are graded from the very low to very high. Based on the justified WSPMs maps (scenario 3) of W. Fierran and W. El-Aawag the major areas categorized as of high and very high RWH potentiality constitute about 49.93% (887.74 km2), 45.74% (896.82 km2), of the total watersheds’ areas, respectively. By comparing scenario 3 with scenarios 1 & 2, a good correlation among the three scenarios was noticeable in the two studied watersheds. where the high-very high RWH potentiality classes for scenarios 1 & 2 are dominating W. Fierran and constitute 66 % and 77 % of its total area, respectively. In W. El-Aawag, these classes constitute 42% and 57 % of its total area, respectively. Accordingly, the performed WSPMs with justified weights have proven a high reliability in their results.
The present work applied an adopted strategy for determining the water/land use priority areas for development. This strategy was achieved depending on the implementation of effective RWH techniques in conjunction with the available groundwater. Accordingly, WSPM map of water/land use priority areas was produced for each watershed. This map classified each watershed into five classes ranging from the very high to very low. The most promising areas for development included the high and very high water/land use priority classes. These classes were classified into four priority areas according to their relative location to the planned RWH systems and the constructed or proposed utilities (i.e. dams, cisterns, or groundwater wells). Accordingly, the promising areas for development in W. Feirran and W. El-Aawag watersheds have total areas of 710.08 and 925.09 km2, respectively.
Determination of how much sustainable the groundwater in El-Qaa Plain area (downstream of El-Aawag watershed) for the future developmental plans was performed by a mathematical flow model (MODFLOW). The model had been run through different scenarios to determine the optimum groundwater safe yield and for the establishment of new developmental activities in El-Qaa Plain area.
The hydrochemical fingerprints and stable environmental isotopes (18O and 2H) of some selected groundwater wells in the study area were examined to understand the groundwater recharge mechanism and possibilities. The results of isotopic and hydrochemical features suggest that most of the groundwater at the study area results from mixing between recent recharge from rainfall and runoff water, in addition to the old paleo-water precipitated during the previous wet climate periods. The significant recent recharge for the groundwater aquifer systems cope with the future requirements of developmental activities.
A system of cisterns, retardation and storage dams, in addition to recharge pits is proposed to control runoff water in the promising sub-watersheds. This system is very important to enhance recharging to the existing aquifers in the study area. Additionally, and based on the conducted mathematical flow model and RWH assessment, three proposed ideal rural villages in El-Qaa Plain area with three proposed groundwater well fields were introduced.