Adam M. Milewski

Assessment and Comparison of TMPA Satellite Precipitation Products in Varying Climatic and Topographic Regimes in Morocco

TRMM Multi-satellite Precipitation Analysis (TMPA) satellite precipitation products have been utilized to quantify, forecast, or understand precipitation patterns, climate change, hydrologic models, and drought in numerous scientific investigations. The TMPA products recently went through a series of algorithm developments to enhance the accuracy and reliability of high-quality precipitation measurements, particularly in low rainfall environments and complex terrain. In this study, we evaluated four TMPA products (3B42: V6, V7temp, V7, RTV7) against 125 rain gauges in Northern Morocco to assess the accuracy of TMPA products in various regimes, examine the performance metrics of new algorithm developments, and assess the impact of the processing error in 2012. Results show that the research products outperform the real-time products in all environments within Morocco, and the newest algorithm development (3B42 V7) outperforms the previous version (V6), particularly in low rainfall and high-elevation environments. TMPA products continue to overestimate precipitation in arid environments and underestimate it in high-elevation areas. Lastly, the temporary processing error resulted in little bias except in arid environments. These results corroborate findings from previous studies, provide scientific data for the Middle East, highlight the difficulty of using TMPA products in varying conditions, and present preliminary research for future algorithm development for the GPM mission.

Integration of GRACE (Gravity Recovery and Climate Experiment) data with traditional data sets for a better understanding of the time-dependent water partitioning in African watersheds

Monthly (71 months) Gravity Recovery and Climate Experiment (GRACE) gravity field solutions acquired over North and Central Africa (August 2002–July 2008) were destriped, smoothed (250 km; Gaussian), and converted to equivalent water thickness. These data were analyzed in a geographic information system environment together with relevant data sets (e.g., topography, geology, remote sensing) to assess the utility of GRACE for monitoring elements of hydrologic systems on local scales. The following were observed over the Niger, Congo, and Nile Basins: (1) large persistent anomalies (standard deviation, SD > 10 cm) on SD images over periods of 2–7 yr; (2) anomalous areas originate at mountainous source areas that receive high precipitation, extend downslope toward mountain foothills, and often continue along main channels, wetlands, or lakes that drain these areas; (3) time-series analyses over anomalous areas showed that seasonal mass variation lags behind seasonal precipitation; and (4) seasonal mass variations showed progressive shift in phase and decrease in amplitude with distance from the mountainous source areas. Results indicate that (1) the observed temporal mass variations are largely controlled by elements of the hydrologic cycle (e.g., runoff, infiltration, groundwater flow) and have not been obscured by noise, as previously thought; and (2) it is possible to use GRACE to investigate the temporal local responses of a much larger suite of hydrologic systems (watersheds, lakes, rivers, and marshes) and domains (source areas and lowlands) within watersheds and subbasins worldwide.

Red Sea rifting controls on aquifer distribution: Constraints from geochemical, geophysical, and remote sensing data

Highly productive wells in the Central Eastern Desert of Egypt are tapping groundwater in subsided blocks of Jurassic to Cretaceous sandstone (Taref Formation of the Nubian Sandstone Group) and Oligocene to Miocene sandstone (Nakheil Formation), now occurring beneath the Red Sea coastal plain and within the proximal basement complex. Aquifer development is related to Red Sea rifting: (1) rifting was accommodated by vertical extensional displacement on preexisting NW-SE– to N-S–trending faults forming a complex array of half-grabens and asymmetric horsts; and (2) subsided blocks escaped erosion accompanying the Red Sea–related uplift. Subsided blocks were identifi ed and verifi ed using satellite data, geologic maps, and fi eld and geophysical investigations. Interpretations of very low frequency (VLF) measurements suggest the faults acted as conduits for ascending groundwater from the subsided aquifers. Stable isotopic compositions (δD: –19.3‰ to –53.9‰; δ 18 O: –2.7‰ to –7.1‰) of groundwater samples from these aquifers are interpreted as mixtures of fossil (up to 70%) and modern (up to 65%) precipitation. Groundwater volumes in subsided blocks are large; within the Central Eastern Desert basement complex alone, they are estimated at 3 × 10 9 m 3 and 10 × 10 9 m 3 for the

Assessment of the Vulnerabilities of the Nubian Sandstone Fossil Aquifer, North Africa

Integrated studies (hydrogeology, geochemistry, remote sensing, geographic information systems, geophysics, and hydrologic modeling) were conducted to investigate the hydrologic setting of the Nubian Sandstone Fossil Aquifer of northeast Africa and to assess the response of the system to climatic and anthropic forcing parameters. Results indicate: ( 1 ) the Nubian Aquifer System is formed of discrete subbasins ( 2 ) Paleo and modern-recharge areas were delineated and recharge from modern precipitation and from Lake Nasser were simulated ( 3 ), previously unrecognized natural discharge locations were identified,and (AbuZeid and Hefny 1992) analysis of temporal gravity solutions indicated declining water supplies in Egypt. Recommendations for sustainable management of the Aquifer include: ( 1 ) construction of local retention structures in areas of relatively high precipitation, ( 2 ) channeling excess Lake Nasser water across the western plateau to recharge the aquifer, and ( 3 ) construction of transient numerical flow models to account for our observations and represent the Nubian Aquifer complex flow system

RESDEM, a tool for integrating temporal remote sensing data for use in hydrogeologic investigations

The dramatic increase in space-borne sensors over the past two decades is presenting unique opportunities for new and enhanced applications in various scientific disciplines. Using these data sets, hydrogeologists can now address and understand the partitioning of water systems on regional and global scales, yet such applications present mounting challenges in data retrieval, assimilation, and analysis for scientists attempting to process relevant large temporal remote sensing data sets (e.g., TRMM, SSM/I, AVHRR, MODIS, QuikSCAT, and AMSR-E). We describe solutions to these problems through the development of an interactive data language (IDL)-based computer program, the remote sensing data extraction model (RESDEM) for integrated processing and analysis of a suite of remote sensing data sets. RESDEM imports, calibrates, and georeferences scenes, and subsets global data sets for the purpose of extracting and verifying precipitation over areas and time periods of interest. Verification of precipitation events is accomplished by integrating other long-term satellite based data sets. The modules in RESDEM process data for cloud detection and others for detecting changes in soil moisture, vegetative water capacity and vegetation intensity following targeted precipitation events. Using the arid Sinai Peninsula (SP; area: 61,000km^2) and the Eastern Desert (ED; area: 220,000km^2) of Egypt as test sites, we demonstrate how RESDEM outputs (verified precipitation events) are now enabling regional scale applications of continuous (1998-2006) rainfall-runoff and groundwater recharge computations.

The groundwater risk index: Development and application in the Middle East and North Africa region

Overreliance on predominantly non-renewable groundwater resources and their subsequent depletion has given rise to adverse environmental, political, economic, and social effects. The high costs of groundwater depletion are exacerbated by the notable absence of tools designed to identify and diagnose areas at risk of groundwater degradation. In this study, a Groundwater Risk Index (GRI) was developed as a distributed composite index to assess and evaluate groundwater depletion risk by combining different environmental and socioeconomic datasets and models. GRI is designed to be used by end-users (e.g. governments, NGOs) as a multicriteria diagnostic tool to identify and determine the probability and severity of an entity experiencing the adverse effects of groundwater mining. Annual GRI results indicate that groundwater risk is highly dependent on governance and food security. Surprisingly, groundwater storage reserves were indeterminate of groundwater risk. Given the centrality of agricultural production in groundwater consumptive use, MENA countries are recommended to mitigate groundwater depletion by establishing reliable and secure virtual water transfers (agricultural trade) to achieve food security, as opposed to unsustainably exploiting finite water resources for short-term food sufficiency. The GRIs design choices, including adopting an equal weighting scheme and a linear additive aggregation approach, promote structural flexibility that enables the modification, application, and implementation of the index in other semi- to hyper-arid regions with a high level of dependency on groundwater resources.

Integrated solutions for hydrologic investigations in arid lands

Hydrological assessment studies across vast regions of the arid world are often hindered by the inaccessibility of these areas and the paucity of data sets, as well as the high expenses and diffi culties entailed in acquiring these data sets, their unpublished nature, and their varying scales, projections, and datum. Using the Eastern Desert (ED) of Egypt (225,000 km 2 ) and the Sinai Peninsula (61,000 km 2 ) as test sites, we demonstrate practical and cost-effective integrated (geochemistry, geophysics, and modeling) solutions that utilize web-based geographic information system (GIS) (http://www.esrs .wmich.edu/webmap) technologies and take advantage of readily available global remote sensing data sets. Adopted methodologies allowed: (1) development of conceptual models for hydrogeologic settings conducive to groundwater entrapment and augmentation, including groundwater in fractured basement aquifers, groundwater impounded by dike swarms crosscutting alluvial aquifers, and groundwater residing in alluvial aquifers associated with ascending deep-seated fossil waters; (2) selection of criteria to identify and validate the preferred distribution of each of these aquifer types and usage of the selected criteria and observations from the GIS data sets to identify, test, and refi ne potential well locations; and (3) construction and calibration of hydrologic models to estimate average annual recharge over the major watersheds in the Sinai (463 ◊ 10 6 m 3 /yr) and ED (171 ◊ 10 6 m 3 /yr) and the average modern contributions to Nubian fossil aquifers (Sinai: 13 ◊ 10 6 m 3 /yr), and to model the partitioning of precipitation as a function of precipitation amounts. The successful application of the integrated and cost-effective methodologies developed for the study areas should invite similar applications in arid regions elsewhere.

Consistency of precipitation products over the Arabian Peninsula and interactions with soil moisture and water storage

ABSTRACT The regional-scale consistency between four precipitation products from the GPCC, TRMM, WM, and CMORPH datasets over the Arabian Peninsula was assessed. Their macroscale relationships were inter-compared with soil moisture and total water storage (TWS) estimates from AMSR-E and GRACE. The consistency analysis was studied with multivariate statistical hypothesis testing and Pearson correlation metrics for the period from January 2000 to December 2010. The products and GRACE estimates were assessed over a representative sub-domain (United Arab Emirates) with available in situ well observations. Next, geographically temporally weighted regression (GTWR) was employed to examine the interdependencies among the peninsula’s hydrological components. The results showed GPCC-TRMM recording the highest correlation (0.85) with insignificant mean differences over more than 90% of the peninsula. The highest GTWR predictive performance of TWS (R2 = 0.84) was achieved with TRMM forcing, which indicates its potential to monitor changes in TWS over the arid peninsular region.