Impact of Climate Change on Water Resources in Eastern Africa

Climate change is causing great impact on water resources in Eastern Africa, and there is need to establish and implement effective adaptation and mitigation measures. According to IPCC, less rainfall during the months that are already dry could increase drought as well as precipitation, and this has great impact on both permanent and seasonal water resources. Increased sea surface temperature as a result of climate change could lead to increased drought cases in Eastern African and entire equatorial region. Climate change will also result in annual flow reduction in various river resources available within the region such as the Nile River. IPCC predicts that rainfall will decrease in the already arid areas of the Horn of Africa and that drought and desertification will become more widespread, and as a result, there will be an increased scarcity of freshwater even as groundwater aquifers are being mined. Wetland areas are also being used to obtain water for humans and livestock and as additional cultivation and grazing land. This chapter reviews the climate change impacts on water resources within the Eastern Africa Region. The climate change impacts on different water resources such as Ewao Ngiro have been highlighted and projection of future climate change on water resources examined. Stream flow for Ewaso Ngiro was found to have a significant increasing trend in 2030s of RCP4.5 and non-significant decreasing trend in stream flow in 2060s for RCP4.5.

Groundwater quality assessment for irrigation use in the Godavari delta region of east coast India using IRWQI and GIS

The present work was carried out in the deltaic region of the river Godavari in Coastal Andhra Pradesh of Southern India to evaluate the status of groundwater quality for irrigation. Groundwater is predominantly used in these productive agricultural fields. Saline water intrusion in fresh groundwater aquifers was recorded in the study area which is mainly due to the excess withdrawal of groundwater. A total of 80 groundwater samples were analyzed for various physical and chemical parameters using standard chemical procedures. The groundwater mainly represents sodium-chloride type which exhibits the mixing of fresh water with the saline water. The high correlation between Na+-Cl− and Mg2+-HCO3− explained that the intermixing of aquifer waters and the leaching of secondary salts. The mechanisms of groundwater have been shown mainly evaporation-fractional crystallization process. The irrigation water quality index was calculated by using different quality indices such as Na%, SAR, RSBC, PI, MH, KR, PS, Cl−:HCO3−, Mg2+:Ca2+, and Na+:Ca2+ to estimate the suitability of groundwater quality for irrigation. Spatial distribution maps were prepared using raster interpolation in GIS. The assessment revealed that the areas covering 67.6% of electrical conductivity, 100% of total dissolved solids, 57.5% of percent sodium, 21.3% of residual sodium bicarbonate, 66.3% of permeable index, 16.3% of magnesium hazard, 65% of Kelly's ratio, 100% of potential salinity were required severe to moderate restrictions. Overall, the groundwater in the study region showed potential salinity due to geogenic and anthropogenic activities thus it must be monitored for sustainable agriculture.

Late Holocene environmental change in Celestun Lagoon, Yucatan, Mexico

Epikarst estuary response to hydroclimate change remains poorly understood, despite the well-studied link between climate and karst groundwater aquifers. The influence of sea-level rise and coastal geomorphic change on these estuaries obscures climate signals, thus requiring careful development of paleoenvironmental histories to interpret the paleoclimate archives. We used foraminifera assemblages, carbon stable isotope ratios (δ13C) and carbon:nitrogen (C:N) mass ratios of organic matter in sediment cores to infer environmental changes over the past 5300 years in Celestun Lagoon, Yucatan, Mexico. Specimens (> 125 µm) from modern core top sediments revealed three assemblages: (1) a brackish mangrove assemblage of agglutinated Miliammina and Ammotium taxa and hyaline Haynesina (2) an inner-shelf marine assemblage of Bolivina, Hanzawaia, and Rosalina, and (3) a brackish assemblage dominated by Ammonia and Elphidium. Assemblages changed along the lagoon channel in response to changes in salinity and vegetation, i.e. seagrass and mangrove. In addition to these three foraminifera assemblages, lagoon sediments deposited since 5300 cal yr BP are comprised of two more assemblages, defined by Archaias and Laevipeneroplis, which indicate marine Thalassia seagrasses, and Trichohyalus, which indicates restricted inland mangrove ponds. Our data suggest that Celestun Lagoon displayed four phases of development: (1) an inland mangrove pond (5300 BP) (2) a shallow unprotected coastline with marine seagrass and barrier island initiation (4900 BP) (3) a protected brackish lagoon (3000 BP), and (4) a protected lagoon surrounded by mangroves (1700 BP). Stratigraphic (temporal) changes in core assemblages resemble spatial differences in communities across the modern lagoon, from the southern marine sector to the northern brackish region. Similar temporal patterns have been reported from other Yucatan Peninsula lagoons and from cenotes (Nichupte, Aktun Ha), suggesting a regional coastal response to sea level rise and climate change, including geomorphic controls (longshore drift) on lagoon salinity, as observed today. Holocene barrier island development progressively protected the northwest Yucatan Peninsula coastline, reducing mixing between seawater and rain-fed submarine groundwater discharge. Superimposed on this geomorphic signal, assemblage changes that are observed reflect the most severe regional wet and dry climate episodes, which coincide with paleoclimate records from lowland lake archives (Chichancanab, Salpeten). Our results emphasize the need to consider coastal geomorphic evolution when using epikarst estuary and lagoon sediment archives for paleoclimate reconstruction and provide evidence of hydroclimate changes on the Yucatan Peninsula.

Sedimentology and Evolution of the Fluvial-Deltaic System: A Modern Depositional Model Analog from the Red Sea Coastal Region, Saudi Arabia

Siliciclastic sediments represent important lithological unit of the Red Sea coastal plain. Their subsurface equivalents are important targets of groundwater aquifer and hydrocarbon reservoirs in the region. The lithofacies of the modern fluvial deltaic system has several distinct geomorphic units and sub-environments such as alluvial, fluvial, delta plain, aeolian, intertidal, coastal sabkha and eustuarine sediments. This study intends to characterize the lithofacies and the depositional environments and to produce an integrated facies model for this modern fluvial-deltaic system. The study might provide a valuable modern analog to several important subsurface Neogene formations that act as important hydrocarbon reservoirs and groundwater aquifers. The study integrates information and data obtained from landsats, maps and detailed field observation and measurements of facies analysis of the fluvial and deltaic along traveses from the Arabian Shield to the Red Sea coast. The lithofacies sediment analysis revealed four main lithofacies associations namely lithofacies A,B,C ad D. Lithoacies Associations A, which represents the oldest unit is dominated by coarse gravel with minor sands facies. While the lithofacies B is dominated byfine gravel and sand lithofacies, occasionally pebbly, vary from horizontal, planar to massive sands with minor laminated to massive silts and mud facies. The lithofacies in A and B show lateral proximal to distal variation as well as characteristic vertical stacking patterns. The Facies Association A and B indicates a change in fluvial depositional styles from gravelly alluvial fans to gravelly sandy fluvial systems. The lithofacies association C represents the recent fluvial system which consists of minor gravel lag deposits associated maily with various sand lithofacies of planner, horizontal and massive sand associated with massive and limainted sand and mud lithofacies. The lithofacies Association D is dominated with Barchan sand dunes local interfigger with muddy iinterdunes and sand sheets. Lithofacies D occupies rather more distal geomporphic position of the fluvial deltaic system that is adjace to coastal sabkha. The lithofacies associations described here document the evolution and development of the coastal plain sediments through space and time under various autocyclic and allocyclic controls. This included the tectonics and structural development associated with the Red Sea rifting and opening since the Oligocene – Miocene time. Others controls include the evolution of the Arabian shield (provenance) and the coastal plain through space and time as controlled by tectonics, sediment supply, climate and locally by autocyclic environmental This study might be beneficial for understanding the controls and stratigraphic evolution of the Red Sea region and will be of great value for reservoir and aquifer characterization, development and management. This modern analog model can also help in providing geological baseline information that would be beneficial for understanding similar ancient fluvial deltaic sediments. The study might provide guides and leads to understand the subsurface facies, stratigraphic architecture and heterogeneity of any potential groundwater aquifers and hydrocarbon reservoirs.

Compare the Changes of Groundwater Type and Microbial Community in Four Shallow Aquifers Affected by Seawater Intrusion in the East Coastal of Pearl River Delta

Seawater intrusion has become a serious natural disaster in coastal regions around the world. Four shallow groundwater aquifers of Pearl River were sampled to study the changes of groundwater types and microbial communities caused by seawater intrusion. Seawater intrusion caused significantly increased cations (Na+, K+, Ca2+, Mg2+) and anions (Cl-, SO42-, HCO3-), and the groundwater type turned from HCO3-Ca to Cl•HCO3-Na•Ca and Cl•SO4-Na•Mg. The composition and diversity of groundwater geochemistry changes. Gammaproteobacteria species and Alphaproteobacteria species are dominant species, and the salinity of groundwater is the main environment factor that affect the relative abundance. The α-diversity of microbial community in three types groundwater are significantly different (P = 0.002，R2 = 0.959). The correlation between species in class level with different ions were also observed. Aeromonadales, Vibrionales, Alteromonadales and Oceanospirillales have a significant positive correlation with Cl-, SO42-, Na+ and Mg2+ (P < 0.05) in Cl•SO4-Na•Mg type, while in Cl•HCO3-Na•Ca type groundwater, Vibrionales and Oceanospirillales have positive correlations with Cl-, Na+, Ca2+, but negative correlations with HCO3-. Aeromonadales and Alteromonadales are opposite of this. The results demonstrate that groundwater type is the main factors influence the correlation between species and environments, other geophysical factors have weak influence. This shift of shallow groundwater type and microbial community under seawater intrusion were studied for the first time, it is momentous for forward exploration of groundwater microbial ecology in the coastal area under the background of seawater intrusion.

Advancements in Techniques for Complex Plug and Abandonment Using Survey Management and Magnetic Ranging Methods

Complex plug and abandonments are required when it is not possible to permanently seal a wellbore utilizing conventional methods. This paper will provide an overview of advanced survey management techniques and their application to complex wellbore abandonment operations. The overview will include the utilization of technologies including active magnetic ranging, gyroscopic and magnetic surveys, and advanced survey correction algorithms. The economic benefits due to the successful outcomes will be shown as well as the mitigation of potential environmental hazards to groundwater aquifers. The described methods have been proven in real-world scenarios, where complex technical challenges necessitate the requirement of a complex abandonment. Two case studies will be presented; one operation where the target well suffered from a restriction in the casing that prevented access to the reservoir, and another where a wellbore was found during civil construction activities in an unexpected position and created a high-risk challenge due to the potential for reservoir gases and liquids leaking uncontrolled into the construction zone. The application of these techniques in abandoning complex wellbores that are unable to be plugged by conventional means provides the industry with solutions to the technically challenging problem of wellbore abandonments when physical access to the wellbore is not possible. These techniques provide economical and low-risk solutions to operators in both onshore and offshore decommissioning activities.

A Hotspot of Arid Zone Subterranean Biodiversity: The Robe Valley in Western Australia

Knowledge of subterranean fauna has mostly been derived from caves and streambeds, which are relatively easily accessed. In contrast, subterranean fauna inhabiting regional groundwater aquifers or the vadose zone (between surface soil layers and the watertable) is difficult to sample. Here we provide species lists for a globally significant subterranean fauna hotspot in the Robe Valley of the Pilbara region, Western Australia. This fauna was collected from up to 50 m below ground level using mining exploration drill holes and monitoring wells. Altogether, 123 subterranean species were collected over a distance of 17 km, comprising 65 troglofauna and 58 stygofauna species. Of these, 61 species were troglobionts and 48 stygobionts. The troglofauna occurs in small voids and fissures in mesas comprised mostly of an iron ore formation, while the stygofauna occurs in the alluvium of a river floodplain. The richness of the Robe Valley is not a localized aberration, but rather reflects the richness of the arid Pilbara region. While legislation in Western Australia has recognized the importance of subterranean fauna, mining is occurring in the Robe Valley hotspot with conditions of environmental approval that are designed to ensure species persistence.

Laboratory Experiments to Evaluate the Effectiveness of Persulfate to Oxidize BTEX in Saline Environment and at Elevated Temperature Using Stable Isotopes

In this study, batch experiments were carried out to investigate the effectiveness of persulfate (PS) as an oxidant agent to remediate benzene, toluene, ethylbenzene, and xylenes (BTEX) in saline environments and at high water temperatures (30°C). This hydrological setting is quite common in contaminated groundwater aquifers in Middle Eastern countries. In general, increasing the system temperature from 10 to 30°C greatly enhanced the effectiveness of PS, and resulted in a faster oxidation rate for the target contaminants. When PS was added to the reactor at 30 °C, the targeted contaminants were almost completely oxidized over a 98-day reaction period. During the chemical oxidation of the BTEX, carbon and hydrogen isotope fractionations were monitored and utilized as potential proof of contaminant degradation. The calculated carbon-enrichment values were −1.9‰ for benzene, −1.5‰ for ethylbenzene and toluene, −0.4‰ for ρ,m-xylene, and -1.4‰ for o-xylene, while the hydrogen enrichment values were −9.5‰, -6.8‰, −2.1‰, −6.9‰, and −9.1‰, respectively. In comparison with other processes, the hydrogen and carbon isotope fractionations during the chemical oxidation by PS were smaller than the isotope fractionations resulting from sulfate reduction and denitrification. This observation demonstrates the differences in the transformation pathways and isotope fractionations when compounds undergo chemical oxidation or biodegradation. The distinct trend observed on the dual isotope plot (Δδ13C vs. Δδ2H) suggests that compound-specific isotope analysis can be utilized to monitor the chemical oxidation of BTEX by PS, and to distinguish treatment zones where PS and biodegradation technologies are applied simultaneously.

Genetic Mapping Reveals Novel Exotic and Elite QTL Alleles for Salinity Tolerance in Barley

Soil salinity is one of the constraints of crop production in Egypt. The aims of this study were to identify genomic regions associated with grain weight and its related traits along with their salinity tolerance indices and to identify the most salinity tolerant and high-yielding genotypes. Therefore, we evaluated an advanced backcross mapping population of barley in newly reclaimed soil under two salinity levels of groundwater aquifers in South of Sinai, Egypt. We detected significant QTL associated with grain weight related attributes and the salinity tolerance index (STI) distributed throughout the whole genome of barley, which can be used to enhance salinity tolerance. Moreover, the markers bPb-3739 (4H, 96.3 cM), AF043094A (5H, 156 cM), bPb-8161 (7H, 2.22 cM), and bPb-5260 (7H, 115.6 cM), were the most important identified genomic regions corresponding to vernalization, dwarfing and dehydrin genes, which are correlated with salinity tolerance. Additionally, the doubled haploid lines SI001, SI043, SI044, SI028, SI242, SI035, and SI005 had the highest STI values based on yield average. The present study demonstrated that wild and elite barley do harbor novel valuable alleles, which can enrich the genetic basis of cultivated barley and improve quantitative agronomic traits under salinity conditions.

HYDROGEOCHEMISTRY AND GROUNDWATER QUALITY ASSESSMENT IN AZINTAN, NORTHWESTERN LIBYA

The groundwater aquifers in Azintan, northwestern Libya suffer from an acute shortage of water. The groundwater was evaluated to determine its suitability for drinking and irrigation purposes from major two aquifers in north and south of Azintan area. This study carried out to assess the groundwater quality and to identify major affecting variables. Twelve samples from the two aquifers were collected. The two aquifers were collected and analyzed for total dissolved , 2+ , Mg 2+ solid (TDS), electrical conductivity (EC), pH, Ca . The results show - and HCO3 2- , CO3 2- , SO4 - , Cl + , K+ Na that, the groundwater in many places is dominated by . Two - and HCO3 2- , SO4 - higher concentrations of Cl water types were recognized in this region are Cl-SO4- Na-Ca and Cl-SO4-Na. Gibbs and Piper method, as well as the hardness, soluble sodium percentage and the permeability index all have been used to assess the diagram quality of the groundwater of aquifers. Further, the multiple correlations and Cluster Analysis of groundwater quality parameters were carried out for further classification and interpretation of the groundwater quality. Finally, water qualities in the study area are compared with Libyan standards and WHO guidelines of drinking water and irrigation purposes.