Mohamed Ahmed

Texas A&M University – Corpus Christi · Department of Physical and Environmental Sciences

Temporal gaps within the Gravity Recovery and Climate Experiment (GRACE) (gap: 20 months), between GRACE and GRACE Follow-On (GRACE-FO) missions (gap: 11 months), and within GRACE-FO record (gap: 2 months) make it difficult to analyze and interpret spatiotemporal variability in GRACE- and GRACE-FO-derived terrestrial water storage (TWSGRACE) time s...

Groundwater resources in the Kingdom of Saudi Arabia (KSA) have high levels of natural radioactivity. Within the northwestern KSA, gross alpha (α) and gross beta (β) levels exceed national and international drinking-water limits. In this study, we developed and used an automated machine learning (AML) approach to quantify relationships between gros...

The availability and quality of limited groundwater resources in Egypt are negatively affected by both natural and anthropogenic forces. It is crucial to understand the recharge sources and mechanisms of country-scale aquifers in order to develop sustainable management scenarios for these groundwater resources. In this study, we compiled all histor...

With the increasing vulnerability of groundwater resources, especially in coastal regions, there is a growing need to monitor changes in groundwater storage (GWS). Estimations of GWS have been conducted extensively at regional to global scales using GRACE and GRACE-FO observations. The major goal of this study was to evaluate the applicability of u...

A multidisciplinary study was conducted to investigate the environmental and economic impact of the Grand Ethiopian Renaissance Dam (GERD). Focusing on Egypt, we estimate projected losses in Egypt’s annual water allocation from the Blue Nile under the 3, 7, and 10-year GERD reservoir filling scenarios, which are part of an array of scenarios curren...

Land subsidence and sea level rise are well-known, ongoing problems that are negatively im-pacting the entire Texas coast. Although ground-based monitoring techniques using long-term global navigation satellite systems (GNSS) records provide accurate subsidence rates, they are labor intensive, expensive, time-consuming, and spatially limited. In th...

The Coastal Bend of Texas has been subject to land subsidence due to the excessive withdrawal of groundwater, oil, natural gas resources, and presence of growth faults, as well as the compaction of Quaternary alluvium. As subsidence poses problems to all coastal communities, infrastructure, and wetland habitats, it is important to determine the rat...

Morocco is blessed by a large reserve of freshwater resources that is being used in an unsustainable manner. In this study, we use a large suite of remote-sensing observations, land surface models, and field measurements to assess the sustainability of groundwater resources in Morocco and their responses to natural and anthropogenic interventions o...

More than one third of the world's population lives in coastal areas. Coastal communities, however, are extremely vulnerable to natural forces such as flooding, hurricanes, tsunamis, and sea level rise. Barrier systems provide a first line of defense for coastal communities by absorbing much of the force of hurricanes and storms and reducing wave e...

A geophysical test site (GTS) contains subsurface targets of known materials, orientations, and depths. GTSs offer unique opportunities for geophysical research, training, and educational activities. They provide platforms to investigate the penetration and resolution of different geophysical techniques for characterizing the shallow subsurface. GT...

The Nile River stretches from south to north throughout the Nile River Basin (NRB) in Northeast Africa. Ethiopia, where the Blue Nile originates, has begun the construction of the Grand Ethiopian Renaissance Dam (GERD), which will be used to generate electricity. However, the impact of the GERD on land deformation caused by significant water reloca...

Terrestrial water storage (TWS) data derived from past Gravity Recovery and Climate Experiment (GRACE; April 2002–June 2017) and current GRACE-Follow On (GRACE-FO; June 2018–present) missions provide insights into mass transport within, and between, different Earth’s systems. In 2017 Earth Science Decadal Survey, a future gravity mission (GRACE-II;...

Over the years, many oil and gas wells have been abandoned, without proper plugging, around homes, farms, industrial sites, and urban areas. These abandoned wells are becoming potential groundwater contamination sources that could leak hydrocarbon to the subsurface aquifer units. When screened to multiple aquifer units, abandoned wells may also all...

Land deformation is a well-known problem affecting the coastlines worldwide. In South Texas, large amounts of hydrocarbon and groundwater extraction put this community at a higher risk of land deformation, especially compounded with sea level rise. Much of the area is comprised of rural countryside and small towns, so conventional methods of tracki...

Terrestrial water storage (TWS) data derived from past Gravity Recovery and Climate Experiment (GRACE; April 2002–June 2017) and current GRACE-Follow On (GRACE-FO; June 2018–present) missions provide insights into mass transport within, and between, different Earth’s systems (e.g., atmosphere, oceans, groundwater, and ice sheets). However, there ar...

Assessment of the flash flood hazard in arid regions is a serious challenge, especially as the climate changes. The Kingdom of Saudi Arabia lies in one of the most arid regions of the world and is known for recurring flash floods in many basins, particularly in the southwest. Many dams have been constructed in some basins; however, flash floods som...

Achieving sustainability for the groundwater resources is more crucial and challenging in northern Africa than in any other part of the globe. We integrated temporal (April 2002–September 2019) terrestrial water storage (TWS) data derived from the Gravity Recovery and Climate Experiment (GRACE; April 2002–June 2017) and GRACE-Follow On (GRACE-FO; J...

Monitoring temporal variations in groundwater levels provides a key to sustainable freshwater resource utilization and management, sustainable land use, and sustainable crop acreage, yield, and production. This study used ground penetrating radar (GPR) to monitor temporal variations in groundwater levels in urban areas, and to define the factors th...

This chapter documented the history of the geological research in Egypt. It exhibits the ancient literature written and complied on the geology of Egypt including Hume’s book and Geology of Egypt books of Rushdi Said that were issued in 1962 and 1990. In addition to literature, the chapter covers the history of geological mapping in Egypt and also...

The freshwater resources in Africa are vulnerable to natural variabilities as well as anthropogenic interventions. In this study, temporal (April 2002–June 2017) Gravity Recovery and Climate Experiment (GRACE) data are integrated, in a geographic information system environment, with rainfall, temperature, evapotranspiration, and altimetry remote se...

The GRACE-derived terrestrial water storage (TWS) provides measurements of the mass exchange and transport between continents, oceans, and ice sheets. In this study, a statistical approach was used to forecast TWS data using 10 major African watersheds as test sites. The forecasted TWS was then used to predict drought events in the examined African...

Gravity Recovery and Climate Experiment (GRACE) data, along with readily available remote sensing datasets and the outputs of land-surface and climate models, are used to monitor spatiotemporal variabilities in the groundwater resources of the Red Sea Coastal Aquifer (RSCA) system in Saudi Arabia; to investigate their responses to climate projectio...

An integrated approach was developed to assess the sustainability, origin, age, evolution, and groundwater potential of large fossil aquifers using the Mega Aquifer System (MAS) (area: 2 × 106 km2) in the Arabian Peninsula as a test site. A two-step exercise was adopted, the sustainability of the MAS was first investigated through the analysis of G...

There is a general agreement that deep aquifers experience significant lag time in their response to climatic variations. Analysis of Temporal Gravity Recovery and Climate Experiment (GRACE), Soil Moisture and Ocean Salinity mission (SMOS), satellite altimetry, stable isotopic composition of groundwater, and precipitation and static global geopoten...

The availability and the future of freshwater resources are major challenges in the Middle East, and a vital issue for the Kingdom of Saudi Arabia. Temporal Gravity Recovery and Climate Experiment (GRACE) data along with other datasets are employed to monitor the spatiotemporal trends in freshwater availability over the Red Sea Hills, and to examin...

The arid and semi-arid regions of the world are facing limited freshwater resources, minimal amounts of rainfall, and increasing population pressure and water demands. These resources, often groundwater, are vulnerable to both natural variability and anthropogenic interventions. Here, we develop and apply an integrated approach using geophysical, g...

Egypt is currently seeking additional freshwater resources to support national reclamation projects based mainly on the Nubian aquifer groundwater resources. In this study, temporal (April 2002 to June 2016) Gravity Recovery and Climate Experiment (GRACE) derived terrestrial water storage (TWSGRACE) along with other relevant datasets were used to m...

An integrated research approach (remote sensing, field, geophysics) was conducted to investigate the structural control on groundwater flow in large aquifers using the Nubian Sandstone Aquifer System (NSAS) of NE Africa as a test site. The aquifer extends over 2.2 x 106 km2 in Egypt, Libya, Chad, and Sudan and consists of thick (> 3 kms), water-bea...

Data from the Gravity Recovery and Climate Experiment (GRACE) and outputs of the CLM4.5 model were used to estimate recharge and depletion rates for large aquifers, investigate the connectivity of an aquifer's subbasins, and identify barriers and preferred pathways for groundwater flow within an aquifer system. The Nubian Sandstone Aqui-fer System...

Freshwater resources in the arid Arabian Peninsula, especially transboundary aquifers shared by Saudi Arabia, Jordan, and Iraq, are of critical environmental and geopolitical significance. Monthly Gravity Recovery and Climate Experiment (GRACE) satellite-derived gravity field solutions acquired over the expansive Saq transboundary aquifer system we...

The North China Plain contains 65% of the country’s agricultural land and 24% of its fresh water resources. Monthly (January 2003 to December 2012) Gravity Recovery and Climate Experiment (GRACE) data were used to quantify anthropogenic impacts on groundwater depletion rates in the northern China region; areas include the North China Plain and surr...

Remote sensing data sets are providing opportunities to investigate aquifers in arid and semi-arid areas worldwide including the following: (1) hydrologic setting and aquifer connectivity, (2) distribution of structures in the surface and subsurface, (3) structural control (e.g., impediments and preferred pathways) on groundwater accumulation and f...

An integrated research approach (remote sensing, field, geophysics) was conducted to investigate the response of large aquifers to dry and wet periods, using the less studied Nubian Sandstone Aquifer System (NSAS) of NE Africa as a test site. The aquifer extends over 2.2 x 106 km2 in Egypt, Libya, Chad, and Sudan and consists of thick (> 3 km), wat...

Data from the Gravity Recovery and Climate Experiment (GRACE) and outputs of the CLM4.5 model were used to estimate recharge and depletion rates for large aquifers, investigate the connectivity of an aquifer's subbasins, and identify barriers and preferred pathways for groundwater flow within an aquifer system. The Nubian Sandstone Aqui-fer System...

The Jazan city in the Jazan Province of the Kingdom of Saudi Arabia is a vibrant and rapidly growing economic center and port. The old city of Jazan is centered over a salt dome (diaper) that crops out over an area, 3-4 km wide and 20 to 40 m above surroundings. The intrusion of the diaper into the overlying cap rock causes uneven surfaces, comprom...

The Gravity Recovery and Climate Experiment (GRACE), along with other relevant field and remote sensing datasets, was used to assess the performance of two land surface models (LSMs: CLM4.5-SP and GLDAS-Noah) over the African continent and improve the outputs of the CLM4.5-SP model. Spatial and temporal analysis of monthly (January 2003 to December...

The wet climatic periods in the Quaternary in north Africa and in Arabia were traditionally attributed to intensification of paleo-monsoons during interglacial periods and progressive northward migration of monsoonal front. In N Africa, the monsoonal model could not account for: (1) progressive W to E depletion (Morocco: -20 to -40‰; ; Libya: -70 t...

Assessment, monitoring, and development of the fresh water resources in the Arabian Peninsula (AP) are critical for the sustenance of the AP’s growing population and water consumption. Monthly (04/2002-11/2014) Gravity Recovery and Climate Experiment (GRACE) data along with other relevant climatic, geologic, hydrogeologic, and remote sensing datase...

The Nubian Sandstone Aquifer System (NSAS), one of the largest (area: ~2×106 km2) groundwater systems worldwide, is formed of three major sub-basins: Kufra (Libya, NE Chad and NW Sudan), Dakhla (Egypt), and N. Sudan Platform (Sudan). To determine the mean residence time of water in the aquifer, the connectivity of its sub-basins and the groundwater...

Radar interferometric techniques including Persistent Scatterer (PS), Small BAseline Subset (SBAS), and two and three pass (differential interferometry) methods were applied to Synthetic Aperture Radar (SAR) datasets. These include the European Space Agency (ESA) ERS-1, ERS-2, Environmental satellite (Envisat), and Phased Array type L-band Syntheti...

Recent land subsidence incidences in the Kingdom of Saudi Arabia (KSA) resulted in loss in life and property. In this study, an integrated approach is adopted to accomplish the following: (1) map the spatial distribution of areas that are witnessing land subsidence, (2) quantify the rates of land subsidence, and (3) identify the factors causing the...

Jazan City is a growing (in size and population) industrial city in the Jazan Province and an important port on the Red Sea coastline of Saudi Arabia. Parts of the city are built on sabkha deposits and others on a salt plateau (diaper) that intrudes overlying sedimentary sequences. Both areas are reported to experience various degrees of ground def...

Structural control on the groundwater flow in arid regions is still poorly understood. Understanding the distribution of structural discontinuities (i.e. faults, joints and shear zones), their cross cutting relationships, and their relation with the regional hydraulic gradient are critical for deciphering the complexity of water resources distribut...

We applied Persistent scatterer interferometry (PSInSAR) to assess land deformation (subsidence and uplift) across the entire Nile delta and its surroundings and to identify possible causes of the observed deformation. For the purpose of the present study, 100 Envisat Advanced Synthetic Aperture Radar (ASAR; level 0) scenes that were acquired along...

We adopted a statistical approach that could potentially advance GRACE’s applications and benefits to the GRACE user community at large. The proposed methodology accomplishes the following: (1) fills gaps in GRACE temporal records, (2) minimizes the lag in GRACE data release time by providing near-real time reliable estimates of GRACE data, and (3)...

The Gravity Recovery and Climate Experiment (GRACE), along with other relevant field and remote sensing datasets, was used to evaluate the performance of two land surface models (LSMs): CLM4.5-SP and GLDAS-Noah over varying hydrologic and climatic settings in Africa (e.g., arid, semiarid, tropical, subtropical, and Mediterranean). Spatial and tempo...

Red Sea and Gulf of Suez rift systems were largely accommodated by extensional faults that formed a complex array of half grabens and asymmetric horsts. Those rift-related basins are of extreme importance for groundwater exploration in Egypt. Gravity and magnetic data were used to investigate the hydrogeologic and structural settings, areal distrib...

An integrated [very low frequency (VLF) electromagnetic, magnetic, remote sensing, field, and geographic information system (GIS)] study was conducted over the basement complex in southern Sinai (Feiran watershed) for a better understanding of the structural controls on the groundwater flow. The increase in satellite-based radar backscattering valu...

Efforts are made to investigate the spatial and temporal climate change–related variations in precipitation as well as the nature of the factors controlling these variations over the Arabian Peninsula (AP). The Climate Prediction Centers (CPC) Merged Analysis of Precipitation (CMAP) temporal (January 1979 to November 2011) data was used to investig...

One of the largest watersheds in the Kingdome of Saudi Arabia is Almadinah watershed with an area: ~108,000 km2. The partitioning of precipitation into runoff, recharge, and evaporation over the Almadinah watershed is estimated using the Soil Water Assessment Tool (SWAT). The rainfall inputs for SWAT model were extracted from the Tropical Rainfall...

Assessment and development of freshwater resources remain the main and the only key to sustain the Kingdome of Saudi Arabia growing population and increasing water consumption. An integrated (remote sensing, GIS, and modeling) approach was applied to spatially delineate the recharge areas of, and model the precipitation of precipitation over, the A...

The Nubian Sandstone Aquifer System (NSAS) is shared by Egypt, Libya, Chad and Sudanand is one of the largest (area: ~ 2 × 106 km2) groundwater systems in the world. Despite its importance to the population of these countries, major hydrological parameters such as modern recharge and extraction rates remain poorly investigated given: (1) the large...

The Nubian Sandstone Aquifer System (NSAS) is shared by Egypt, Libya, Chad and Sudanand is one of the largest (area: ~ 2 × 106 km2) groundwater systems in the world. Despite its importance to the population of these countries, major hydrological parameters such as modern recharge and extraction rates remain poorly investigated given: (1) the large...

The River Nile is the main source of fresh water in Egypt. Most of Egypt’s River Nile water (>85%) originates as precipitation over the Ethiopian highlands and is channeled by the Blue Nile. The construction (years: 2011 to 2017) of the Renaissance Dam (reservoir capacity: 70 x 109m3) on the Blue Nile poses an extreme threat to Egypt’s population....

Numerous land subsidence events have been recently reported from central and northern parts of the Kingdom of Saudi Arabia in Hail, Al Qassim, Al Jowf, and Buraydah Provinces. In some cases, these incidences resulted in losses in life and property. In this study, an integrated (field, geologic, remote sensing) approach is applied to accomplish the...

Africa, the second-driest continent in the world after Australia, is one of the most vulnerable continents to climate change. Understanding the impacts of climatic and anthropogenic factors on Africa’s hydrologic systems is vital for the assessment and utilization of Africa’s water resources. In this study, we utilize the Gravity Recovery and Clima...

The Rub Al Khali (RAK), encompasses one of the World's largest (area: 650,000 km2) aquifer systems, the Rub Al Khali Aquifer System (RAKAS) of the Arabian Peninsula. In this study, we develop and apply an integrated and cost-effective approach, involving geophysical, geochemical, isotopic, field, and remote sensing investigations to understand the...

The Arabian Peninsula (AP), like many places around the world, is apparently witnessing the impacts (amount, patterns, and frequency of precipitation) of global warming. Precipitation over the AP is largely controlled by two main wind regimes, the winter (October to March) northerlies or northwesterlies, hereafter referred to as westerlies, and the...

In arid and semiarid regions of the world, the demand for freshwater resources is increasing due to increasing populations and the scarcity of freshwater supplies. This chapter utilizes the Gravity Recovery and Climate Experiment (GRACE) data in conjunction with other readily available remote sensing data sets, as well as field and geochemical data...

Study region: Mojave Desert, USA. Study focus: An integrated (near-surface geophysics, remote sensing, isotopic analyses) study was conducted in the Mojave River Basin and Morongo Groundwater Basin to investigate potential effects that the Helendale Fault [HF] and basement uplifts might have on groundwater flow in the Mojave Desert. New hydrologica...

The Nubian Sandstone Aquifer System (NSAS) is the largest groundwater aquifer in the Sahara spanning the political boundaries of four countries in north-eastern Africa; Egypt, Sudan, Libya, and Chad. The NSAS represents as a potential water resource for future development programs in these countries. Thickness of the aquifer ranges from tens of met...

We integrated (in a Geographic Information System [GIS] environment) observations from remote sensing data (Gravity Recovery and Climate Experiment [GRACE], Environmental Satellite [Envisat], Tropical Rainfall Measuring Mission [TRMM], Landsat Thematic Mapper [TM], Google Earth images) with geophysical (Very Low Frequency [VLF], Vertical Electrical...

We utilize the Gravity Recovery and Climate Experiment (GRACE) and land surface models (LSM: GLDAS and CLM4.5) in conjunction with other readily-available datasets for monitoring the spatial and temporal trends in Terrestrial Water Storage (TWS) over a time period of 10 years (01/2003–12/2012) and to investigate the nature of, and the factors contr...

An integrated approach using the GRACE, outputs of the CLM4.5 model, remote sensing, geological, and geochemical data were used to quantify the recharge and depletion rates of the Nubian Sandstone Aquifer System (NSAS) over the past 10 years (2003–2012). The adopted approach includes: (1) extraction of recharge rates over the NSAS outcrops in Sudan...