Papers by Aondover Tarhule
InTech eBooks, Jan 18, 2012
Developing countries face unique vulnerability and adaptation challenges related to climate varia... more Developing countries face unique vulnerability and adaptation challenges related to climate variability and change as a result of being, on the one hand, more exposed and sensitive, and on the other hand, having less adaptive capacity for dealing with it World Bank, 2010). Also widely accepted is the urgent need for adaptation to combat what the Inter Governmental Panel on Climate Change (IPCC) sees as the most likely climate change impacts in the developing world. These include; "reduced crop yields in tropical areas leading to increased risk of hunger, spread of climate sensitive diseases such as malaria, and an increased risk of extinction of 20-30 percent of all plant and animal species." The report continues, "by 2020, up to 250 million people in Africa could be exposed to greater risk of water stress. Over the course of this century, millions of people living in the catchment areas of the Himalayas and Andes face increased risk of floods as glaciers retreat followed by drought and water scarcity as the once extensive glaciers on these mountain ranges disappear. Sea level rise will lead to inundation of coasts worldwide ...people living with the constant threat of tropical cyclones now face increased severity and possibly increased frequency of these events with all associated risks to life and livelihoods" (UNFCC, 2007, p. 5). In the face of such dire consequences, developing countries especially and international organizations, led most prominently by the UNFCCC (United Nations Framework Convention on Climate Change; see ), have been hard at work in an attempt to design feasible climate change adaptation policies and actions. The nexus of these efforts between the developing countries and the UNFCCC is a mechanism called NAPA (National Adaptation Programmes of Actions), which were instituted by Decision 5 at the 7 th Conference of Parties (CoP) held in Marrakesh, Morocco, in 2001. These efforts have galvanized political action and provided much needed guidance to developing countries on how to plan for adaptation to predicted climate change impacts. Even more importantly, they have also provided funding mechanisms and commitments from developed countries to help the least developed countries (UNFCC Article 4/3-5) implement adaptation strategies. Despite such seemingly impressive progress, a number of critical issues related to adaptation remain to be resolved if we are to move beyond the rhetoric of broad scale policy www.intechopen.com Climate Variability -Some Aspects, Challenges and Prospects Climate change is expected to impact developing countries more severely because developing countries are more vulnerable. But what is vulnerability and why are developing countries more vulnerable than their developed counterparts? The IPCC (2007, p. 89) defines vulnerability as "the degree to which a system is susceptible to, and unable to cope with, adverse effects of climate change, including climate variability and extremes.
Damaging Rainfall and Flooding: The Other Sahel Hazards
Climatic Change, Oct 1, 2005
... Sahel residents attribute these floods to five major causes including both natural andanthrop... more ... Sahel residents attribute these floods to five major causes including both natural andanthropogenic, but they view ... total annual rainfall amounts from the drought conditions of the past three decades, (ii) rapid population growth, especially in the major urban centers and its ...
The Future of Water
Elsevier eBooks, 2017
Abstract Water is the driver of nature and its availability and quality often constitute a limit ... more Abstract Water is the driver of nature and its availability and quality often constitute a limit on economic development and human welfare. Because of this primacy, the task of providing water in sufficient quantity and acceptable quality to the world's human population while assuring its availability for future needs constitutes one of the preeminent challenges of the 21st century. As the chapters in this book show, the challenges are numerous and widely cited. Globally, around 750 million people, most living in developing countries, lack access to safe drinking water, 2.5 billion lack adequate sanitation, and 842,000 people still die annually because of diarrhea from contaminated water sources [World Health Organization/UNICEF Joint Monitoring Program (WHO/JMP), 2015]. These challenges are real and tragic, and ongoing efforts, such as the Strategic Development Goals of the United Nations Development Program, must be sustained until they are resolved. This chapter examines three questions likely to confront future water resources management, namely: Should water resources managers attempt to satisfy demand for water or curtail it? What is the economic status and value of water? What is the risk of future megadroughts caused by climate change? Question one is addressed by reviewing the changing paradigms in water resources management, especially the emerging concept of water soft path. To address question two, we examine the contested economic proposition of the uniqueness of water. Finally, question three is reviewed through the risk of future megadroughts as well as the real life experiment of the current California drought. These questions are illustrative of both the scope and complexity of future water resources challenges.
Hydrology Research, Jan 31, 2013
The conversion of land from existing uses to biofuel cultivation is expected to increase given co... more The conversion of land from existing uses to biofuel cultivation is expected to increase given concerns about the sustainability of fossil fuel supplies. Nonetheless, research into the environmental impacts of biofuel crops, primarily the hydrological impacts of their cultivation, is in its infancy. To investigate such issues, the response of a 1,649 km 2 semiarid basin to the incremental substitution of the widely discussed biofuel candidate switchgrass (Panicum virgatum L.) for native land uses was modeled using the Soil and Water Assessment Tool (SWAT). Median discharges decreased by 5.6-20.6% during the spring and by 6.4-31.2% during the summer, depending on the quantity of acreage converted. These were driven by an increased spring and summer evapotranspiration of 3.4-32.0% and 1.5-18.9%, respectively, depending on the quantity of switchgrass biomass produced. The substitution of switchgrass also resulted in larger quantities of water stress days than in baseline scenarios. The authors encourage the exploration of alternative biofuel crops in semiarid areas to mitigate such negative impacts.
Spatiotemporal dynamics of Terrestrial Water Storage Trends in the Nile River Basin
AGU Fall Meeting Abstracts, Dec 1, 2019
Potential Water Availability Index (PWAI): A New Water Vulnerability Index for Africa Based on GRACE Data
African rainfall variability: science and society
The Sahel-Soudano zone that spans North Africa, from Senegal to Ethiopia, has experienced pronoun... more The Sahel-Soudano zone that spans North Africa, from Senegal to Ethiopia, has experienced pronounced climatic variability (and conflicts) for millennia. This home to 250 million people—one quarter of Africa’s population—is a fragile transition zone in environmental and human terms. From south-to-north, rainfall decreases from around 30 inches per year on average to essentially nothing. Back-to-back contrasting rain years (deficits in 2011, floods in 2012) left over 18 million people in the West African Sahel threatened by food shortages between 2012 and 2013, highlighting yet again the strong the dependence between livelihoods on rainfall in the region. Ironically (tragically, even), the stakeholders within the Sahel have less access to, and therefore use less, instrumental rainfall information for planning and management than almost anywhere else in the world. Furthermore, short-term weather and seasonal climate forecasting have limited skill for West Africa. Whilst many of the Nat...
Comparison of decadal water storage trends from common GRACE releases (RL05, RL06) using spatial diagnostics and a modified triple collocation approach
Journal of Hydrology X, 2021
Scientific Reports, 2019
GRACE Terrestrial Water Storage (TWS) provides unique and unprecedented perspectives about freshw... more GRACE Terrestrial Water Storage (TWS) provides unique and unprecedented perspectives about freshwater availability and change globally. However, GRACE-TWS records are relatively short for long-term hydroclimatic variability studies, dating back to April 2002. In this paper, we made use of Noah Land Surface Model (LSM), and El Niño–Southern Oscillation (ENSO) data in an autoregressive model with exogenous variables (ARX) to reconstruct a 66-year record of TWS for nine major transboundary river basins (TRBs) in Africa. Model performance was evaluated using standard indicators, including the Nash Sutcliffe Efficiency criteria, cumulative density frequency, standardized residuals plots, and model uncertainty bounds. Temporally, the reconstruction results were evaluated for trend, cycles, and mode of variability against ancillary data from the WaterGAP Model (WGHM-TWS) and GPCC-based precipitation anomalies. The temporal pattern reveals good agreement between the reconstructed TWS, WGHM-...
Validation and testing of the FAO AquaCrop model under different levels of nitrogen fertilizer on rainfed maize in Nigeria, West Africa
Agricultural and Forest Meteorology, 2017
The objectives of this study were to evaluate AquaCrop’s ability to simulate the cumulative grain... more The objectives of this study were to evaluate AquaCrop’s ability to simulate the cumulative grain yield of rainfed maize for different soil fertility levels in the northern Guinea Savanna zone of Nigeria. Seven years (2007–2013) of field experimental data on maize grown under rainfed condition at the Institute for Agricultural Research were used to calibrate (2007 data set) and validate (2008–2013 data set) AquaCrop. We assessed the agreement between model simulated and actual maize yields using correlation coefficient, R2, and the index of agreement, d, as well as the NRMSE. R2 values ranged from 0.82 to 0.99 while values of d ranged from 0.6 to 0.88, indicating a moderate poor agreement to very good agreement. The NRMSE varied between 8% (indicating “excellent” agreement) and 17% (good agreement). On the other hand, in percentage terms the differences between actual and simulated yield range from +19% to −30%. Of the 19 treatments evaluated, 13(68%) are within 10% of each other, generally considered very good, three (16%) are within 20%, considered acceptable; and 3 (16%) are >20%, considered poor. Furthermore, simulated yields systematically over-estimate observed yields a not uncommon result that suggests the need for additional calibration. The grain and biomass yields evaluation results were consistent with other validation studies of the model.
Adaptations to the dynamics of rural water supply from natural sources: A village example in semi-arid Nigeria
Mitigation and Adaptation Strategies for Global Change, Sep 1, 2002
... Rainfall is markedly seasonal, with the rainy season beginning in May and ending in October. ... more ... Rainfall is markedly seasonal, with the rainy season beginning in May and ending in October. Most of the rainfall is generated by the storms and disturbances associated with the Inter-Tropical Discontinuity (or ITD) which lingers over the region at this time (Omotosho 1990). ...
Resistance Tomographic Imaging, Digital Mapping, and Immersion Visualization of Evaporite Karst in Western Oklahoma (Final Report)
Oklahoma Water Resources Research Institute, 2002
Journal of Geography and Earth Sciences, 2015
The Niger River Basin (NRB) in West Africa is drought-prone. This study evaluates and compares th... more The Niger River Basin (NRB) in West Africa is drought-prone. This study evaluates and compares the performance of three drought indices in the Upper Niger subwatershed, two of which drought managers in the region are already used to, the Standardized Rainfall Anomaly Index (SAI) and Bhalme and Mooley Drought Index (BMDI). The third one is the Standardized Precipitation Index (SPI). A time series of the three indices were derived using 52 years growing season monthly station rainfall (April-October), regionalized into areal rainfall. The calculated statistical relationships of the indices provides diagnostics for their performance evaluation based on six decision criteria, whose weightings were determined using pairwise comparison of the Analytic Hierarchy Process (AHP) approach. Two-parameter gamma distribution is the best fit and most suitable for transformation of rainfall distribution in the region. SPI requiring equiprobablity transformation of the data, satisfied the normality assumption, whereas it was violated by others. The three drought indices showed similar temporal trends in all the time scales, with the historical extreme climatic anomalies in the basin well captured. Results further showed that SPI, which is more robust and sensitive to dryness, identified 42 and 17 moderate and extreme drought events respectively, against 35 and 7 captured by the SAI and BMDI that are less robust. In this paper, we find that SPI ranked first among other meteorological drought index in the Niger River basin, having the highest priority weight of 0.6123, with the inconsistency in the pairwise comparison with the tolerable limit (i.e. CR < 0.1).
Climate, 2015
The Abdus Salam International Center for Theoretical Physics (ICTP) version 4.4 Regional Climate ... more The Abdus Salam International Center for Theoretical Physics (ICTP) version 4.4 Regional Climate Model (RegCM4) is used to investigate the rainfall response to cooler/warmer sea surface temperature anomaly (SSTA) forcing in the Indian and Atlantic Oceans. The effect of SSTA forcing in a specific ocean basin is identified by ensemble, averaging 10 individual simulations in which a constant or linearly zonally varying SSTA is prescribed in individual basins while specifying the 1971-2000 monthly varying climatological sea surface temperature (SST) across the remaining model domain. The nonlinear rainfall response to SSTA amplitude also is investigated by separately specifying +1K, +2K, and +4K SSTA forcing in the Atlantic and Indian Oceans. The simulation results show that warm SSTs over the entire Indian Ocean produce drier conditions across the larger Blue Nile catchment, whereas warming ≥ +2K generates large positive rainfall anomalies exceeding 10 mm• day -1 over drought prone regions of Northeastern Ethiopia. However, the June-September rainy season tends to be wetter (drier) when the SST warming (cooling) is limited to either the Northern or Southern Indian Ocean. Wet rainy seasons generally are characterized by deepening of the monsoon trough, east of 40°E, intensification of the Mascarene high, strengthening of the Somali low level jet and the tropical easterly jet, enhanced zonal and meridional vertically integrated moisture fluxes, and steeply vertically decreasing moist static energy. The opposite conditions hold for dry monsoon seasons.
Climate Variability - Regional and Thematic Patterns
Journal of Earth System Science, 2011
This paper uses Visual MODFLOW to simulate potential impacts of anthropogenic pumping and recharg... more This paper uses Visual MODFLOW to simulate potential impacts of anthropogenic pumping and recharge variability on an alluvial aquifer in semi-arid northwestern Oklahoma. Groundwater withdrawal from the aquifer is projected to increase by more than 50% (relative to 1990) by the year 2050. In contrast, climate projections indicate declining regional precipitation over the next several decades, creating a potential problem of demand and supply. The following scenarios were simulated: (1) projected groundwater withdrawal, (2) a severe drought, (3) a prolonged wet period, and (4) a human adjustment scenario, which assumes future improvements in water conservation measures. Results indicate that the combined impacts of anthropogenic pumping and droughts would create drawdown of greater than 12 m in the aquifer. Spatially, however, areas of severe drawdown will be localized around large-capacity well clusters. The worst impacts of both pumping and droughts will be on stream-aquifer interaction. For example, the projected aquifer pumpage would lead to a total streamflow loss of 40%, creating losing stream system regionally. Similarly, a severe drought would lead to a total streamflow loss of >80%. A post-audit of the model was also carried out to evaluate model performance. By simulating various stress scenarios on the alluvial aquifer, this study provides important information for evaluating management options for alluvial aquifers.
Hydrology Research, 2014
The conversion of land from existing uses to biofuel cultivation is expected to increase given co... more The conversion of land from existing uses to biofuel cultivation is expected to increase given concerns about the sustainability of fossil fuel supplies. Nonetheless, research into the environmental impacts of biofuel crops, primarily the hydrological impacts of their cultivation, is in its infancy. To investigate such issues, the response of a 1,649 km 2 semiarid basin to the incremental substitution of the widely discussed biofuel candidate switchgrass (Panicum virgatum L.) for native land uses was modeled using the Soil and Water Assessment Tool (SWAT). Median discharges decreased by 5.6-20.6% during the spring and by 6.4-31.2% during the summer, depending on the quantity of acreage converted. These were driven by an increased spring and summer evapotranspiration of 3.4-32.0% and 1.5-18.9%, respectively, depending on the quantity of switchgrass biomass produced. The substitution of switchgrass also resulted in larger quantities of water stress days than in baseline scenarios. The authors encourage the exploration of alternative biofuel crops in semiarid areas to mitigate such negative impacts.
Evaluating the impacts of climate change and switchgrass production on a semiarid basin
Hydrological Processes, 2014
Climate and land use changes greatly modify hydrologic regimes. In this paper, we modelled the im... more Climate and land use changes greatly modify hydrologic regimes. In this paper, we modelled the impacts of biofuel cultivation in the US Great Plains on a 1061‐km2 watershed using the Soil and Water Assessment Tool (SWAT) hydrologic model. The model was calibrated to monthly discharges spanning 2002–2010 and for the winter, spring, and summer seasons. SWAT was then run for a climate‐change‐only scenario using downscaled precipitation and a projected temperature for 16 general circulation model (GCM) runs associated with the Intergovernmental Panel on Climate Change Special Report on Emission Scenarios A2 scenario spanning 2040–2050. SWAT was also run on a climate change plus land use change scenario in which Alamo switchgrass (Panicum virgatum L.) replaced native range grasses, winter wheat, and rye (89% of the basin). For the climate‐change‐only scenario, the GCMs agreed on a monthly temperature increase of 1–2 °C by the 2042–2050 period, but they disagreed on the direction of change in precipitation. For this scenario, decreases in surface runoff during all three seasons and increases in spring and summer evapotranspiration (eT) were driven predominantly by precipitation. Increased summer temperatures also significantly contributed to changes in eT. With the addition of switchgrass, changes in surface runoff are amplified during the winter and summer, and changes in eT are amplified during all three seasons. Depending on the GCM utilized, either climate change or land use change (switchgrass cultivation) was the dominant driver of change in surface runoff while switchgrass cultivation was the major driver of changes in eT. Copyright © 2014 John Wiley & Sons, Ltd.
Hydrogeology Journal, 2007
Visual MODFLOW, a numerical groundwater flow model, was used to evaluate the impacts of groundwat... more Visual MODFLOW, a numerical groundwater flow model, was used to evaluate the impacts of groundwater exploitation on streamflow depletion in the Alluvium and Terrace aquifer of the Beaver-North Canadian River (BNCR) in northwestern Oklahoma, USA. Water demand in semi-arid northwestern Oklahoma is projected to increase by 53% during the next five decades, driven primarily by irrigation, public water supply, and agricultural demand. Using MODFLOW's streamflow routing package, pumping-induced changes in baseflow and stream leakage were analyzed to estimate streamflow depletion in the BNCR system. Simulation results indicate groundwater pumping has reduced baseflow to streams by approximately 29% and has also increased stream leakage into the aquifer by 18% for a net streamflow loss of 47%. The magnitude and intensity of streamflow depletion, however, varies for different stream segments, ranging from 0 to 20,804 m 3 /d. The method provides a framework for isolating and quantifying impacts of aquifer pumping on stream function in semiarid alluvial environments. Résumé Visual MODFLOW, un modèle numérique d'écoulement des eaux souterraines, a été utilisé pour évaluer les impacts de l'exploitation de l'eau souterraine sur la réduction du régime de la rivière dans un aquifère d'alluvions et de terrasse de la Rivière canadienne Beaver-North (BNCR) au nord-ouest de l'Oklahoma, aux USA.
Groundwater Monitoring & Remediation, 2006
Leachate plume emanating from an old unlined municipal landfill site near the city of Norman, Okl... more Leachate plume emanating from an old unlined municipal landfill site near the city of Norman, Oklahoma, is discharging into the underlying alluvial aquifer. Subsurface imaging techniques, electrical resistivity tomography and electrical conductivity (EC) logging, were used on the site to detect and map the position of the leachate plume. Anomalous EC zones, delineated with the two methods, correlated with the occurrence of the plume detected by water chemistry analyses from multilevel monitoring wells. Specific conductance, a potential indicator of leachate contamination, ranged from 1861 to 7710 μS/cm in contaminated zones and from 465 to 2180 μS/cm in uncontaminated ground water. Results are in agreement with those from earlier studies that the leachate plume emerges from the landfill along preferential pathways. Additionally, there are indications that the leading edge of the plume has migrated, at least, 200 m away from the landfill in the direction of ground water flow.
Uploads
Papers by Aondover Tarhule