Farouk El-Baz’s research while affiliated with Boston University and other places

For socioeconomic development in arid regions, there is an increasing need for groundwater resources due to rapid population expansion. It is necessary to apply innovative approaches for managing the sustainability of groundwater resources. Thus, remote sensing, geologic, climatic, and hydrologic data are integrated through the GIS-based frequency ratio and overlay analysis for assessing the spatial distribution of groundwater potential zones (GWPZs) of Wadi Al Hamdh, Saudi Arabia. Twelve factors controlling groundwater’s existence and infiltration were identified, normalized using the frequency ratio technique and combined through GIS techniques. To accomplish this, 313 well locations in the study area were used for training (70%) and 137 well locations were utilized for validation (30%). Using receiver operating characteristic (ROC) curves and field data, the model predictions were validated and showed very good performance (AUC: 0.893). The five zones on the GWPZs map correspond to 2.24, 5.81, 13.39, 53.90, and 24.65% of the entire area. These are: excellent, good, moderate, low, and very low perspectivity. As a good example, the applied approaches provided very good results that are significant to planning and sustainable development as well as managing groundwater resources in arid regions.

Groundwater exploration has been following many approaches and different tools are used to identify define clues on terrain surface that evidence groundwater accumulation and flow. Sometimes positive results are reached, but this is not always the case and in many other cases the dug boreholes are found empty or with little amount of groundwater. Therefore, it is necessary to adopt a credible approach for groundwater exploration where hydrogeologists rely on during preliminary surveys. Recently, the development of remote sensing techniques enabled following successful approaches. In particular, satellite images are processed to enabling identifying signatures for groundwater storage and flow. The most significant among these signatures are the linear features, to so-called lineaments which can be observed on satellite images. These signatures often reflect fracture system and other types of rock deformation, where the latter constitute a major controlling hydrogeological elements that must be taken into account. This study has been initiated to deduce an empirical relationship between the characteristics of lineaments and the location of boreholes with their productivity. Three main lineaments properties were analyzed using Landsat 7 ETM+ images and GIS techniques. These are the lineaments frequency, density and fault lineaments. The obtained lineament maps were overlapped with the location of water wells in 90 sites from different regions of Lebanon. It was resulted that there is clear relationship between the proximity of fault lineaments and water well with considerable productive. Therefore, this relationship can be adopted in groundwater exploration, notably in a terrain with intensive rock deformations like the case of Lebanon.KeywordsInfiltrationGroundwater pumpingFissuresSpace techniquesLebanon

Stream flow into the sea, as plumes, is a widespread hydrologic phenomenon in many coastal zones. These plumes have different hydrologic regime between watercourses and this is controlled by rainfall rate and patterns, as well as by the morphometric and geometric properties of drainage systems. In order to compare the mechanism of water input/output, that is, precipitation amounts in a drainage system versus streamflow outlets into the sea, times series datasets must be primarily prepared. In this regards, remotely sensed data can fulfill this comparison by accounting the temporal records and short-term retrieval time after an event. This study aims at investigating the use of remote sensing datasets in assessing diverse hydrologic characteristics of streamflow into the sea where ten Lebanese coastal rivers were used. Therefore, the Tropical Rainfall Mapping Mission (TRMM) microwave datasets and Moderate Resolution Imaging Spectro-radiometer (MODIS-Terra) images were used. Rainfall data retrieved from TRMM was compared with the available ground measurements from the in-situ gauges. Therefore, comparison has be applied between the areal extent of freshwater plumes and the measured river discharge from flow-meters. The results showed that both have a variance between 0.71 and 1.30 which stems from variable inland slopes and rainfall patterns. The lag time and residence times of plumes in the seawater were calculated and then compared for the streamflow of all investigated rivers. The resulted lag times (rainfall versus appurtenance into the sea) ranges between 1 and 4 days, while the residence time of plumes sustains between 3 and 8 days. The year 2002 was selected for the study, and this was based on data availability from space-borne and field measurements. The applied methodology proved to be reliable and cost effective and it can be adopted to different time periods for the Lebanese rivers, especially when streamflow data are lacking.KeywordsCoastal riverRunoffSlopeSpace techniquesLebanon

At present, in addition to several thousands of satellites for various applications, there are more than 900,000 pieces from 1 to 10 cm in Earth-orbit. This has been estimated by the European Space Agency (ESA). Furthermore, as time passes, these satellites represent debris. Such accumulated debris threaten the daily uses of space-based applications satellites and future missions. The potential danger would persist unless the international space community considers the risks and join forces to mitigate the danger. Today, only ideas have been proposed by the various space agencies without taking much action. Each of these ideas deals with a specific size of debris. Thus, this paper proposes an integrated design to remedy the situation. It is a satellite with robotic arms, electromagnetic mesh and onboard radar to detect, collect, shred and sort most of the debris larger than 1 cm. This material can, thus, be used as a source of raw material in a novel "made in space program." It can be used as row material for 3d printers for metal and non-metals needed for the maintenance of the International Space Station (ISS) and other equipment of future space missions. This proposal is a premiere design and a start of a pilot model. Also proposed here is a recommendation for a sustainable financing model that can be established by space agencies by assigning a tariff for each future space flight. The tariff value could be determined based on, the extent of the mission's lifetime, the size of the satellite, and the purpose of the mission.

Remote sensing and GIS approaches have provided valuable information on modeling water resources, particularly in arid regions. The Sahara of North Africa, which is one of the driest regions on Earth, experienced several pluvial conditions in the past that could have stored significant amounts of groundwater. Thus, harvesting the stored water by revealing the groundwater prospective zones (GWPZs) is highly important to water security and the management of water resources which are necessary for sustainable development in such regions. The Shuttle Radar Topography Mission (SRTM) digital elevation model (DEM), Advanced Land Observing Satellite (ALOS)/Phased Array type L-band Synthetic Aperture Radar (PALSAR), Tropical Rainfall Measuring Mission (TRMM), and Landsat-8 OLI data have all successfully revealed the geologic, geomorphic, climatic, and hydrologic features of Wadi El-Tarfa east of Egypt’s Nile River. The fusion of eleven predictive GIS maps including lithology, radar intensity, lineament density, altitude, slope, depressions, curvature, topographic wetness index (TWI), drainage density, runoff, and rainfall data, after being ranked and normalized through the GIS-based analytic hierarchy process (AHP) and weighted overlay methods, allowed the GWPZs to be demarcated. The resulting GWPZs map was divided into five classes: very high, high, moderate, low, and very low potentiality, which cover about 10.32, 24.98, 30.47, 24.02, and 10.20% of the entire basin area, respectively. Landsat-8 and its derived NDVI that was acquired on 15 March 2014, after the storm of 8–9 March 2014, along with existing well locations validated the GWPZs map. The overall results showed that an integrated approach of multi-criteria through a GIS-based AHP has the capability of modeling groundwater resources in arid regions. Additionally, probing areas of GWPZs is helpful to planners and decision-makers dealing with the development of arid regions.

The Qena Bend of the Nile River, named after Qena town in Upper Egypt, is considered a remarkable geomorphological feature in southern Egypt. It is unique and its geodynamic formation is still not fully understood. This study addresses the relationship between the bend geometry and the structural setting of the underlying basement complex using remotely sensed and aeromagnetic data. The hillshade and drainage extraction algorithms were applied to the digital elevation model (DEM) of the Shuttle Radar Topography Mission (SRTM) to define the lineaments dissecting the limestone plateaus and control the Nile Valley cliffs. Moreover, the Interferometry Synthetic Aperture Radar (InSAR) coherence image was derived from two Sentinel-1 images to delineate and/or confirm the structures, which underlie and control the sand dunes movement. In addition, various edge-detection derivatives were applied on the reduced-to-pole (RTP) aeromagnetic anomaly to define the basement structures. The results showed the derived surface and subsurface structures are controlled by the NW–SE and NE–SW trends of the Suez–Red Sea, Aqaba–Dead Sea, and Qena–Safaga Shear Zone. The RTP anomaly reveals a strong NE–SW positive anomaly zone coinciding with the bend. The magnetic 2D forward modelling and 3D depth inversion suggest the basement consists of granitic rocks (0.02 – 0.033 cgs) and the positive anomaly below the bend probably attributes to a major uplift at a depth of 750 m. This uplift broke the plateau forming NE–SW-oriented weak structural zones along which the bend was developed.

Today, as estimated by the U.S. Space Surveillance Network, there are 14,000 pieces of debris larger than 10 cm in Earth-orbit. That is in addition to thousands of satellites for various applications. As time passes, these satellites represent debris that might represent dangerous space waste. Such accumulated items orbit the Earth at very high speed and might threaten the daily uses of space-based applications, such as satellites that are needed for weather forecasting, telecommunications, and global positioning systems (GPS). In addition, this might negatively affect future missions -- unless the international space community considers the risks and joins forces to mitigate them. Today, only ideas have been proposed by the various space agencies without taking much action. Each proposed idea deals with a specific size of debris. This paper proposes an integrated approach to collect most of the debris to be recycled for use as a source of raw material in construction equipment, which are used in maintenance of the International Space Station (ISS) and other equipment needed by future space missions and spacecraft. Furthermore, this proposal might solve the problem of the lack of space in the ISS, which served as home to numerous astronauts for more two decades. The proposed design could be implemented through cooperative programs by the world’s space agencies. Because few countries represent the main source of this space wastes, it is here proposed that a financing source would be established by assigning a tariff for each future space flight, as a percentage of the cost of each mission. For example, fees could be determined based on; the extent of the mission’s lifetime, the size and weight of the satellites, and the purpose of the mission.

Groundwater has recently become a main resource for domestic water and irrigation in Lebanon. During the last two decades, surface water and shallow groundwater have been severely exhausted to meet water demand. This study seeks to understand the groundwater flow/storage regime and the mechanism of water loss into the sea using a geospatial approach. Landsat thermal satellite images from years 2013–2015 are used to detect freshwater seeps in the coastal waters of Lebanon to analyse their distribution, time of occurrence and origin. The analysis is supplemented with data from the Tropical Rainfall Measuring Mission (TRMM), geological maps, the SRTM Digital Elevation Model (DEM), and springs’ location maps. A groundwater potentiality map is constructed to understand points of surface water entry into the ground, areas of accumulation and water transport pathways. Results show dominant thermal plumes off-shore adjacent to Akkar District and Batroun city. The former relates to direct rainfall and the latter to rainfall and snowmelt on land. No surface drainage is associated with either plume. Both plumes project 8–13 km from inland along fault alignments. These faults act as conduits to channel rainwater and snowmelt from the surrounding mountains before seeping into the sea. It is thus feasible to capture the water lost this way for farming and domestic uses. The study presents an integrative geospatial approach that can be extended and applied throughout the coastal Middle East and North Africa Region to assess freshwater seeps into the sea.

Despite the fact that the Sahara is considered the most arid region on Earth, it has witnessed prolonged fluvial and aeolian depositional history, and might harbor substantial fresh groundwater resources. Its ancient fluvial surfaces are, however, often concealed by aeolian deposits, inhibiting the discovery and mapping of potential groundwater recharge areas. However, recent advances in synthetic aperture radar (SAR) imaging offer a novel approach for detecting partially hidden and dynamic landscape features. Interferometry SAR coherence change detection (CCD) is a fairly recent technique that allows the mapping of very slight surface changes between multidate SAR images. Thus, this work explores the use of the CCD method to investigate the fluvial and aeolian morphodynamics along two paleochannels in Egypt. The results show that during wetter climates, runoff caused the erosion of solid rocks and the rounding of sand-sized grains, which were subsequently deposited in depressions further downstream. As an alternating dry climate prevailed, the sand deposits were reshaped into migrating linear dunes. These highly dynamic features are depicted on the CCD image with very low coherence values close to 0 (high change), while the deposits within the associated ephemeral wadis show low to moderate coherence values ranging from 0.2 to 0.4 (high to moderate change), and the country rocks show a relative absence of change with high coherence values close to 1. These linear dunes crossed their parent’s stream courses and dammed the runoff to form lakes during rainy seasons. Part of the dammed surface water would have infiltrated the ground to recharge the permeable wadi deposits. The alternation of fluvial and aeolian depositional environments produced unique hydromorphometrically trapped lakes that are very rare in arid regions, but of great interest because of their significance to groundwater recharge.

Several fresh-water carbonate deposits (tufa and travertine) were formed at different elevations within the Kurkur paleolake, 50 km west of Aswan, Egypt. Such paleolake was unique and confined in sag between the cuesta and the capping platform of Sin El-Kaddabaa Plateau. This work aims at integrating the remote sensing data together with the chemical and petrographic analyses to map and characterize these tufa and travertine deposits to define their paleo-depositional environment. A DEM with 2.5 m spatial resolution was generated from two ALOS/PRISM images to show geomorphological and hydrological parameters. In addition, full-polarimetric SAR data were used to investigate the scattering response of these tufa and travertine deposits. These deposits show a volume scattering response, with an increase in the pedestal height of the co- and cross-polarized signatures. The tufa and travertine deposits range from Pleistocene (older upper level) to Recent (younger lower level). The young tufa is hard, light brown porous and thinly-laminated, while the old tufa is generally coarse crystalline and consists of columnar pseudo denderitic calcite crystals. The travertine displays a stromatolitic fabric, where thin dark micritic algal laminae alternate with relatively thick calcitic bands (∼1 cm). Conducted XRD and chemical analyses reveal that these tufa and travertine are entirely composed of low magnesium calcite, with traces of quartz (<2%). Moreover, the δ¹³C and δ¹⁸O values suggest that the old tufa have been developed during warm pluvial periods, while the younger ones were precipitated in drier periods. Two hypotheses were introduced to explain the changes in the hydrological regime of Kurkur paleolake; the first proposes a hydrological breaching due to water overflow on the lake's low periphery areas that led to their desiccation (where the tufa and travertine were deposited) and the second is the possible integration into the regional drainage networks of the area presently occupied by Lake Nasser.