Assessing Water Resources Access of Nouhao Sub-Basin, Burkina Faso

Water resource access in the Nouhao sub-basin, assessed based on the availability of drinking water mobilization facilities, the availability of water for uses and the quality of drinking water, revealed that in 2017 the basin was covered by 1249 modern water point, main drinking water sources. On average, the sub-basin shows a ratio of 271 users per drinking water point. Communal level shows some disparity with Bittou recording the highest number of people per drinking water point, i.e., around 537. Water that can be captured in the entire sub-basin meets only 42% of the total water needs from the three mains uses: irrigation, domestic consumption and livestock. The highest demander among these uses is Irrigation with 75% of the need, i.e., approximately 12,859,995 m3. Water in 33% drinking sources of this sub basin is of poor quality. Arsenic, one of the quality parameters studied, is found in some communes of the sub-basin. 11% of the water points in Bissiga are arsenic polluted making this commune the most arsenic contaminated location. The vulnerability maps deducted from lack of water for uses;lack of drinking water works and poor water quality shows so, the exposure level of the sub-basin’ communes to some potential risks related to low water resources access.

Assessment of Climate Change’s Impacts on River Flows in the Songwe Sub-Basin

River flow in the Songwe sub-basin is predicted to alter due to climate change, which would have an impact on aquatic habitats, infrastructure, and people’s way of life. Therefore, the influence of climate change should be taken into account when making decisions about the sustainable management of water resources in the sub-basin. This study looked into how river discharge would react to climate change in the future. By contrasting hydrological characteristics simulated under historical climate (1981-2010) with projected climate (2011-2040, 2041-2070, and 2071-2100) under two emission scenarios, the effects of climate change on river flow were evaluated (RCP 4.5 and RCP 8.5). The ensemble average of four CORDEX regional climate models was built to address the issue of uncertainty introduced by the climate models. The SWAT model was force-calibrated using the results from the generated ensemble average for the RCP 4.5 and RCP 8.5 emission scenarios in order to mimic the river flow during past (1981-2010) and future (2011-2100) events. The increase in river flows for the Songwe sub-basin is predicted to be largest during the rainy season by both the RCP 4.5 and RCP 8.5 scenarios. Under RCP 8.5, the abrupt decrease in river flow is anticipated to reach its maximum in March 2037, when the discharge will be 44.84 m3/sec, and in March 2027, when the discharge will be 48 m3/sec. The extreme surge in river flow will peak, according to the RCA4, in February 2023, in April 2083 under RCP 4.5, and, according to the CCLM4 and RCA4, in November 2027 and November 2046, respectively. The expected decrease and increase in river flow throughout both the dry and wet seasons may have an impact on the management of the sub-water basin’s resources, biodiversity, and hydraulic structures. The right adaptations and mitigation strategies should be adopted in order to lessen the negative consequences of climate change on precipitation, temperature, and river flow in the sub-basin.

Analysing the relationship between drought and soil erosion using vegetation health index and RUSLE models in Godavari middle sub-basin,India

Drought is a natural phenomenon posing severe implications for soil,groundwater and agricultural yield.It has been recognized as one of the most pervasive global change drivers to affect the soil.Soil being a weakly renewable resource takes a long time to form,but it takes no time to degrade.However,the response of soil to drought conditions as soil loss is not manifested in the existing literature.Thus,this study makes a concerted effort to analyze the relationship between drought conditions and soil erosion in the middle sub-basin of the Godavari River in India.MODIS remote sensing data was utilized for driving drought indices during 2000-2019.Firstly,we constricted Temperature condition index(TCI)and Vegetation Condition Index(VCI)from Land Surface Temperature(LST)and Enhanced Vegetation Index(EVI)derived from MODIS data.TCI and VCI were then integrated to determine the Vegetation Health Index(VHI).Revised Universal Soil Loss Equation(RUSLE)was utilized for estimating soil loss.The relationship between drought condition and vegetation was ascertained using the Pearson correlation.Most of the northern and southern watersheds experienced severe drought condition in the sub-basin during2000-2019.The mean frequency of the drought occurrence was 7.95 months.The average soil erosion in the sub-basin was estimated to be 9.88 t ha^(-1)year^(-1).A positive relationship was observed between drought indices and soil erosion values(r value being 0.35).However,wide variations were observed in the distribution of spatial correlation.Among various factors,the slope length and steepness were found to be the main drivers of soil erosion in the sub-basin.Thus,the study calls for policy measures to lessen the impact of drought and soil erosion.

Climate Change Induced Vulnerability of Smallholder Farmers: Agroecology-Based Analysis in the Muger Sub-Basin of the Upper Blue-Nile Basin of Ethiopia

Ethiopia is also frequently identified as a country that is highly vulnerable to climate variability and change. The potential adverse effects of climate change on Ethiopia’s agricultural sector are a major concern, particularly given the country’s dependence on agricultural production, which is sensitive to climate change and variability. This problem calls the need to understand agroecology based vulnerability to climate change and variability to better adapt to climate risks and promote strategies for local communities so as to enhance food security. The objective of this study is to estimate and compare the level of vulnerability of smallholder farmers’ to climate change and variability from three agroecology representing Muger River sub-Basin of the upper Blue Nile basin using Livelihood Vulnerability Index. The research used quantitative and qualitative data collected through Focussed Group Discussions, key informant interviews and a questionnaire survey of 442 sampled households across three different agro-ecologies in the sub-basin. The results reveal that along with the different agro-ecological zone, households and communities experienced different degrees of climate vulnerability. These differences are largely explained by differences in exposure, sensitivity and adaptive capacity of smallholder farmers. The livelihood vulnerability analysis reveals that Kolla agroecology exhibits relatively low adaptive capacity, higher sensitivity and higher exposure to climate change and variability that is deemed to be the most vulnerable agroecology. These contributing factors to a vulnerability in Kolla agroecology are largely influenced by assets, livelihood diversification, innovation, infrastructure, socio-demographic factors, social capital, agriculture, food security, and natural disasters and climate variability. The result furthermore shows that Dega agroecology has least vulnerable owing to its higher adaptive capacity. These results suggest that designing agroecology based resilience-building adaptation strategies is crucial to reduce the vulnerability of smallholder farmers to climate change and variability.

3D Modelling from New and Existing Gravity Data of an Intrusive Body in the Northern Part of Kribi-Campo Sub-Basin in Cameroon

A new gravity survey was carried out in the northern part of the onshore Kribi- Campo sub-basin in Cameroon. The data were incorporated to the existing ones and then analyzed and modeled in order to elucidate the subsurface structure of the area. The area is characterized in its north-western part by considerably high positive anomalies indicative of the presence of a dense intrusive body. We find, 1) from the analysis of the gravity residual anomaly map, the high positive anomalies observed are the signature of a shallow dense structure;2) from the multi-scale analysis of the maxima of the horizontal gradient, the structure is confined between depths of 0.5 km and 5 km;3) from the quantitative interpretation of residual anomalies by spectral analysis, the depth to the upper surface of the intrusive body is not uniform, the average depth of the bottom is h1 = 3.6 km and the depths to particular sections of the roof of the intrusion are h2 = 1.6 km and h3 = 0.5 km;4) and the 3D modeling gives results that are suggestive of the presence of contacts between rocks of different densities at different depths and a dense intrusive igneous body in the upper crust of the Kribi zone. From the 3D model the dense intrusive igneous block is surrounded by sedimentary formations to the south-west and metamorphic formations to the north-east. Both formations have a density of about 2.74 g/cm3. The near surface portions of this igneous block lie at a depth range of 0.5 km to 1.5 km while its lower surface has a depth range of 3.6 km to 5.2 km. The shape of the edges and the bottom of the intrusive body are suggestive of the fact that it forms part of a broader structure underlying the Kribi-Campo sub-basin with a great influence on the sedimentary cover.

Geochemistry of Cretaceous Mudrocks and Sandstones from Douala Sub-Basin, Kumba Area, South West Cameroon: Constraints on Provenance, Source Rock Weathering, Paleo-Oxidation Conditions and Tectonic Environment

Geochemical data of fifteen Cretaceous sediment samples from Kumba area in the Douala sub-basin are presented to determine the provenance, source rock weathering, tectonic setting and paleo-oxidation conditions of the depositional setting of these rocks. For this purpose, the whole-rocks were analyzed for their major and trace element, including rare earth elements (REEs), contents by ICP-AES and ICP-MS methods respectively. On the basis of their major element composition, the rocks have been classified mainly as Fe-shale, shale, arkose and Fe-sandstone. For the provenance, the plot of Zr vs. TiO2, Y/Ni vs. Cr/V, TiO2 vs. Al2O3 diagrams, high LREE/HREE ratios (5.84 to 20.91) and negative and positive Eu anomalies (Eu/Eu*= 0.87 to 1.62) suggest that the studied rocks were mainly derived from felsic igneous rocks with lesser contribution of mafic components. The higher values of paleo-weathering indices such as Plagioclase Index of Alteration (PIA) and Chemical Index of Weathering (CIW), ranging from 79.63 to 99.90 and 87.57 to 99.92 respectively, suggest that the sediments and their potential source rocks experienced intense weathering. Whereas the variable Chemical Index of Alteration (CIA) values (63.01 to 99.50) coupled with high content of K2O (up to 7.5) in most samples could be indicative of K-addition diagenetic processes. The A-CN-K plot also suggests a possible K-addition. The redox conditions during the sedimentation were suboxic to oxic as evidenced by the Ce anomalies of 0.88 to 1.03. This is also confirmed by the values of Ni/Co (less than 7), U/Th (less than 1.25) and Cu/Zn (mostly less than 1). Tectonic discrimination diagrams (e.g., SiO2-K2O/Na2O and Th-Sc-Zr/10) show that these rocks were deposited mainly in an active continental margin setting, and in various tectonic environments. This reflects probably the recycling effect experienced by the samples studied.

Mineralogic Characterization and Petroleum Potential of Clays (Shales) of the N’Kappa Formation (Paléocene-Eocene) in the Douala Sedimentary Sub-basin (South-West Cameroon)

The aim of this research work was to report a facies analysis of the N’Kappa formation, identified the clay minerals present in those facies and evaluate their oil potential. For that to be done, Lithostratigraphic descriptions were performed on three natural outcrops chosen in three different localities of the northern border of Douala sedimentary basin. Ten shaly samples were then collected on those outcrops and submit to X ray diffraction and Rock-Eval pyrolysis. Lithologically, the N’Kappa formation is made up of dark to grey shales and fine to coarse sandtones. The mineralogic content of the shales is made up of Kaolinite, dickite, low quartz and vaterite. Those shaly facies present high amount of immature organic matter (average TOC content around 2%). The petroleum potential is fair to poor (average S2 for all the samples around 3.33 mg HC/g of rock) though some samples (M1 and M2) presenting a good petroleum potential up to 6.62 kg HC/t of rock and 6.44 kg HC/t of rock respectively. They have undergone a low degree of diagenesis (early to burying diagenesis). This is evidenced by the predominance of kaolinite and dickite, low quartz and vaterite which are minerals stable at low temperature.

Thermal structure about southwest sub-basin of South China Sea

There are some factors,such as the topographic relief,sedimentary thickness and thermal conductivity, magmatic activity and thermal cooling,influencing the seafloor heat flow and the evolution of lithosphere structure in southwest sub-basin(SWSB),South China Sea.On the base of the geological structure characteristic of SWSB this paper will discuss some other factors including thermal anomaly area,dike produced by magma intrusion and lithosphere relief,by modeling and calculating.Calculating results indicate partial areas where temperature is higher than vicinity in the lithosphere,which we call thermal anomaly here containing thermal anomaly area and dike in this paper,could decrease heat flow below,increase above,and gradually increase to two sides;heat flow in upwelling parts of lithosphere is usually higher than sinking parts,and in the middle is of a gradual transition.

Evolution of Authigenic Minerals and Porosity in the Deep Formation of Paleogene of Jiyang Sub-basin

The clastic rocks in the depth of 2800-6000 m of the Paleogene in Jiyang sub-basin had undergone the middle diagenesis and late diagenesis.The reservoirs in main areas of the sub-basin developed 2-6 secondary pores zones.The reservoirs in the stage A of middle diagenesis of Bonan fault zone in Zhanhua depression and of the gentle slope belt of Chezhen depression are controlled by the acidic diagenetic medium and developed one secondary pores zone in each diagenetic sub-stage respectively.The contents ofautogenic quartz,pyrite and kaolinite are quite high in these reservoirs.The reservoirs’

Determination of Structural and Geometrical Parameters of the Kribi-Campo Sedimentary Sub-Basin Using Gravity Data

In order to produce a more detailed structural and geometrical information, and determine sediments thickness along the Kribi-Campo sub-basin, statistical spectral analysis and horizontal gradient analysis of residual anomalies coupled with the Euler deconvolution approach were applied on the gravity data in the area. The results obtained from the 2D spectral analysis on anomaly grids gave a depth to the basement rocks of the basin from 0.60 km to 3.93 km. This represents the thickness of the sedimentary formations overlying the basement. The interpretation of the spectral analysis results indicated that the potential hydrocarbon field areas are situated between Kribi and Lolabe and at Campo given that those areas have the highest sedimentary thicknesses values. From the analysis of the horizontal gradient, deep faults mainly striking SW-NE have been traced and a structural map of the area has been produced. By applying the Euler deconvolution method to the gravity data, information about the depth and trend of the main subsurface structures have been obtained.

Structural Architecture for Development of Marginal Extensional Sub-Basins in the Red Sea Active Rift Zone

This paper presents a robust kinematic model that describes northern Red Sea and Gulf of Suez rifting and the development of marginal extensional half-graben sub-basins (ESB). A combination of Landsat Enhanced Thematic Mapper Plus (ETM+) and structural data was used to provide model constraints on the development of rift segments and ESB in the active rift zones. Structural analysis shows rotation and change in strike of rift-bounding faults. The model describes the northern Red Sea region as a poly-phase rift system initiated by late Oligocene (30 - 24 Ma) orthogonal rifting and the development of marginal ESB (now inland ESB), followed by oblique rifting and flank uplift during the early Miocene (24 - 18 Ma). The oblique rifting fragmented the rift depression into segments separated by oblique-slip accommodation within reactivated Pan-African (ca. 600 Ma) fracture zones, resulting in the development of antithetic faults and an en-echelon distribution of inland ESB. The current phase of rifting was instigated by the development of the Dead Sea Transform in response to increased northeasterly extension during the middle Miocene (ca. 18 Ma). The model explains the widening of the Red Sea rift during the last phase more than the Gulf of Suez rift by developing more antithetic faults and formation of offshore ESB, and deepening the rift depression.

Evidence of Some Major Structures Underlying the Douala Sedimentary Sub-Basin: West African Coastal Basin

Gravity data have been processed in the Douala sedimentary sub-basin in a section consisting of a set of 116 gravity data points located between latitudes 3°03'N and 4°06'N and longitudes 9°00'E and 10°00'E. The established Bouguer anomaly fields and the Residual anomaly fields, extracted by upward continuation at an optimum height of 30 km, were both characterized by considerably high positive anomalies. These anomalies showed many ring-like positive gravity anomaly contour lines in the study region. Gravity gradients were analysed using the multi-scale horizontal derivative of the vertical derivative (MSHDVD) method, and this excluded the existence of fault lines across this region. Amplitude spectrum was used to estimate the potential field source at a depth of about 4.8 km. The ideal body theory capable of handling sparse data contaminated with noise was applied along a 50.2 km WWS-EEN profile to determine a density contrast of 0.266 g/cm3. Using these results as constraints, 2.5 D modelling carried out along this profile presented two major blocks with density contrast of 0.266 g/cm3. The first block is probably an intrusive igneous body with a density of about 2.77 g/cm3 , having an average thickness of about 26 km with its top and base lying at depths of about 4.25 km and 30.25 km respectively. The second block is likely a pillar of igneous material, located at a depth of about 10.77 km with a density of about 2.77 g/cm3 whose base goes deep down beyond the crust-mantle boundary. These results support previous findings that there are similarities between the Douala sedimentary sub-basin and the coastal sedimentary basin of Mauritania-Senegal and thus foster the suggestions of a more extensive movement that would have affected the whole of the West African coast.

Gravity Model for an Anomalous Body Located in the NW Portion of the Douala Sedimentary Sub-Basin, Cameroon (Central Africa)

Gravity studies have been carried out in the Douala sub-basin which is a sedimentary basin located both onshore and offshore on the South coast of Cameroon between latitudes 3°03'N and 4°06'N and longitudes 9°00' and 10°00'E, covering a total surface area of 12,805 km2. On its onshore portion, the Douala sub-basin has a trapezoic shape and covers a total surface area of about 6955 km2 while the offshore part covers an area of about 5850 km2. Gravity data used in this study are constituted of 912 gravity data points located between longitudes 8°10.2' to 10°59.4'E and latitudes 2°30.6' to 4°59.4'N and the study area is located to the NW section of the onshore portion of the Douala sub-basin. This study area is characterised by considerably high positive anomalies attaining peak values of about 104.1 mGals at longitude 9°9.9' and latitude 4°1.1' with contour lines which are mostly oriented in the NNE direction. Residual anomalies were extracted by upward continuation of the Bouguer anomaly field at an optimum height of 30 km. This residual field and those obtained by the separation of polynomial of order 4 had a very high correlation coefficient factor of 0.979. The multi-scale horizontal derivative of the vertical derivative (MSHDVD) method was applied on the extracted residual anomalies for the delimitation of possible contacts in the source while the amplitude spectrum was used to estimate the depth to the top of the potential field source. The MSHDVD method did not delimite any clear cut contacts in the source but the amplitude spectrum estimated the potential field source at a depth of about 4.8 km. The ideal body theory was used to determine the density contrast along a 65 km NW-SE profile yielding a value of 0.266 g/cm3. 2.5D modelling aimed at bringing out the underlying structural layout of this study area presents a source body which is very probably an intrusive igneous block surrounded by sedimentary formations and having a density of 2.77 g/cm3 at a depth of about 5.88 km below the surface and an average thickness of about 26.95 km.

Geological,Mineralogical and Geochemical Studies of Pyrite Deposits in the Eastern Part of Douala Sub-Basin(Cameroon,Central Africa)

Pyrite deposit of pK27, Douala sub-basin (Cameroon, Central Africa) was studied in a tropical forest setting physically and using X-ray diffraction and X-ray fluorescence spectrometry (XRF) in order to characterize the mineralization for his industrial utilization. The sedimentary materials from the pyrite deposit were grouped into five (05) main lithofacies, including four claystone facies and one conglomeratic facies. The mineralization occurs along the low slopes of valleys in?light grey claystone facies situated on the bottom of outcrops with 80 to 200 cm thickness. The?particle size distribution of clayey materials host rocks shows that they are essentially constituted of clay and silts fractions. However, their Sorting index (So) more than 4.5 corresponds to poorly sorted sediments and the torrential type;whereas their Coefficient of asymmetry (A) more than 1?indicates that the sorting is carried out towards fine particles. Macroscopically, pyrite in these?materials is in crumbly and consolidated piles with aggregate pyrites in oolithic concretions, and?globular, cubic, octaedric, massive and fossiliferous forms. The mineralogical compositions of?these clayey materials indicate that they are essentially kaolinitic and illitic, followed by goethite, quartz, pyrite, halloysite, anatase and rutile with hematite as accessory minerals. Pyrite in sand fractions is associated with kyanite, grenat, rutile, diopside, muscovite and tourmaline the minerals which?recognize the regional metamorphism. However, the specific chemical signature of SO3content?high in clayey materials and abundant (50.86% - 57.64% SO3) in pyrite is characteristic of the pK27 pyritic formations in the eastern part of Douala sub-basin. Moreover, the Co:Ni ratios of pyrites approximately 0.25 to 0.8 are characteristic of sedimentary pyrites and also suggest an anoxic environment.

Analysis of Rainfall Variability on the Groundwater Levels of Wells in the Nouaho Basin in East-Central Burkina Faso

Sahelian countries are confronted with a lack of reliable data on water and climate allowing them to understand the effects of climate variability. To address this situation, with the support of Water Aid, we have collected rainfall data and groundwater level in wells from 2012 to 2018 with help of local populations. Their contribution made it possible to cover a wider geographical area and to obtain the data necessary to analyze the climate variability on a small and large scale in the sub-basin of the Nouhao. The data collected are well correlated with those collected from the rain gauges of the national meteorological agency in the region of Fada N’Gourma. From 2012 to 2018, August appears to be the rainiest month. It recorded, alone, 1/3 of the average annual rainfall. The depletion of surface water tables is faster after the rainy season. The static level of the water table in the crystalline subsoil also depletes and replenishes at night after the peak water collection time, which is between noon and 8 p.m. These few years of measuring rainfall and groundwater fluctuations have shown that the correlation between rainfall and groundwater level is clearly established. Nevertheless this needs to be more investigated during a longer period to confirm the robustness of the method. On the other hand, the approach to securing water resources based on community monitoring of water resources gives good results in accordance with the National Meteorological Agency and the Directorate of water resources, however, caution recommends continuing measurements over a few decades to confirm its robustness for this aspect too.

First description of scleractinian corals from the Santa Marta and Snow Hill Island(Gamma Member) formations, Upper Cretaceous, James Ross Island, Antarctica

Antarctic corals are known from the Upper Cretaceous Santa Marta Formation(Santonian–early Campanian)and Gamma Member(late Campanian)of Snow Hill Island Formation(late Campanian–early Maastrichtian)but they have not so far been taxonomically described.We describe three corals taxa based on 29 specimens collected in 2007 and 2016 on James Ross Island(northeast of the Antarctic Peninsula).They represent the first formal record of scleractinian corals from the Santa Marta Formation,identified as Caryophylliidae indet.and Gamma Member of Snow Hill Island Formation,identified as Astreopora sp.and Fungiacyathus deltoidophorus.The family Caryophylliidae and the genus Astreopora were not restricted to the Weddellian Biogeographic Province but the species Fungiacyathus deltoidophorus was endemic to Antarctica during the Cretaceous.The genus Fungiacyathus and the family Caryophylliidae thrive in Antarctica until the present day.Fungiacyathus occurred in shallower environments during the late Campanian than today.No specimens related to Astreopora have yet to be found in Antarctica after the late Campanian.This can be explained by the capacity of Fungiacyathus and Caryophyllidae to endure cold waters,since they are asymbiotic corals.The symbiotic Astreopora sp.,due to its sensitivity to low temperatures,became extinct in this continent as soon as the Antarctic waters began to cool,around the Campanian/Maastrichtian.The presence of Astreopora sp.in Gamma Member of Snow Hill Island Formation may represents the first occurrence of this genus in Antarctica and the oldest record of this genus in the Southern Hemisphere.

Geochemical,mineralogical and sedimentological analyses of reworked sediments(new)in the syn-to post-rift Middle Cretaceous-Quaternary detrital deposits from western Atlantic margin of Cameroon:evidence from sedimentation-erosion alternation in the cont

Reworked detrital sediments were discovered in the syn-rift to post-rift Cretaceous to Quaternary(Pleistocene)detrital deposits of the Douala coastal sub-basin in the eastern margin of the South Atlantic Ocean at West Cameroon.This contribution presents the geochemical,mineralogical,and sedimentological data to constrain the origin of these reworked sediments.The investigated samples are characterized by the high values of Plagioclase Index of Alteration(PIA,97.83–99.90),Chemical Index of Alteration(CIA,71.9–99.08),and Chemical Index of Weathering(CIW,98.67–99.90).Data gleaned from these indices suggest that the reworked sediments and their potential source rocks experienced severe weathering.The A-CN-K plot along with the mineralogical indicates a probably post-depositional K-enrichment.The high light rare earth elements(LREE)/heavy rare earth elements(HREE)ratios(15.82–79.13)suggest that the reworked were mainly derived from felsic igneous rocks.This interpretation is further confirmed by the Zr versus TiO2,TiO2/Al2O3,Th/Co versus La/Sc,and La/Th versus Th/Yb plots,which indicate felsic igneous and silicic source rocks.Meanwhile,the high variability of LREE/HREE ratios(15.82–79.13)and the positive Eu anomalies(1.10–1.32)of studied samples could indicate a little contribution of mafic source rocks.Analysis of the distribution of the heavy minerals(e.g.tourmaline,aluminum silicate,and rutile)revealed that these felsic and silicic source rocks are mainly granite and gneiss,probably belonging to the Nyong Group and the Western part of the Neoproterozoic Yaounde Group.The morphoscopic analyses of the host rocks(very angular to angular shapes)have revealed that the reworked sediments have proximal to subproximal onshore origins,probably from former sedimentary deposits,as is indicated by variation of their color.The tectonic discriminant diagram indicates the Oceanic Island Arc and Active Continental Margin which are inconsistent with the geological history of the Douala coastal sub-basin and could be explained by the recycling effect experienced by studied sediments which have been deposited in the coastal plain to the fluvial environment in the Low System Track context.

Extenuating the parameters using HEC-HMS hydrological model for ungauged catchment in the central Omo-Gibe Basin of Ethiopia

Characteristics of ungauged catchments can be studied from the hydrological model parameters of gauged catchments.In this research,discharge prediction was carried out in ungauged catchments using HEC-HMS in the central Omo-Gibe basin.Linear regression,spatial proximity,area ratio,and sub-basin mean were amalgamated for regionalization.The regional model parameters of the gauged catchment and physical characteristics of ungauged catchments were collated together to develop the equations to predict discharge from ungauged catchments.From the sensitivity analysis,crop coefficient(CC),storage coefficient(R),constant rate(CR),and time of concentration(TC)are found to be more sensitive than others.The model efficiency was evaluated using Nash-Sutcliffe Efficiency(N_(SE))which was greater than 0.75,varying between−10%and+10%and the coefficient of determination(R^(2))was approximated to be 0.8 during the calibration and validation period.The model parameters in ungauged catchments were determined using the regional model(linear regression),sub-basin mean,area ratio,and spatial proximity methods,and the discharge was simulated using the HEC-HMS model.Linear regression was used in the prediction where p-value≤0.1,determination coefficient(R2)=0.91 for crop coefficient(CC)and 0.99 for maximum deficit(MD).Constant rate(CR),maximum storage(MS),initial storage(IS),storage coefficient(R),and time of concentration(TC)were obtained.The result is that an average of 30 m^(3)/s and 15 m^(3)/s as the maximum monthly simulated flow for ungauged sub-catchments,i.e.Denchiya and Mansa of the main river basin.

Well-Based Quantitative Reservoir Characterization of Eocene Sokor-1 Formation, Termit Basin, Niger

The Eocene Sokor1 Formation is proven oil reservoir rocks in the Termit sub-basin. These sandstone intervals are deeply buried, highly heterogeneous in character and characterized by Low Contrast Low Resistivity (LCLR) log responses. Petrophysical and quantitative well-based rock physics interpretations were integrated for property estimations, fluid and lithology typing in reservoir characterization. Six (6) reservoir sandstone intervals were identified, delineated and correlated across five (5) wells. The estimated petrophysical properties showed that the Eocene Sokor1 sandstones have averagely good reservoir properties with sand_5 interval exhibiting exceptional reservoir properties. Vp/Vs vs. AI and μρ vs. λρ elastic cross-plots color coded with reservoir properties (Vsh and Φ), show distinct and well separated data clusters signifying hydrocarbon bearing sandstones, brine sandstones and shales/mudstones in the 3D crossplot planes with varying seismic elastic property values in each well thereby, enhancing reservoir characterization and providing information’s about the burial history, reservoir quality and property distribution in the sub-basin. The analysis suggests that, although the reservoir interval has averagely good petrophysical properties in all wells, the seismic elastic crossplots show that these properties are much better distributed in wells 2 and 3 than in wells 4, 5 and 9. Therefore, sand_5 reservoir interval in wells 2 and 3 is likely to be more hydrocarbon bearing and productive than wells 4, 5 and 9 in the sub-basin.

Alleviating Water Scarcity in the Central Rift Valley Lakes through an Inter-Basin Water Transfer, Ethiopia

Demand for fresh water, as one of the major natural resources, is increasing rapidly with increasing development and environmental degradation. The continued abstraction of water from Lake Ziway and its main feeder rivers Meki and Katar for irrigation indicates that the water demand may soon exceed the supply. To illustrate disparities in spatial distribution of water resources, the Upper Awash sub-basin, which shares a water-divide with the CRVL sub-basin, has large flow volumes particularly in the rainy season and suffers with seasonal flooding. The rationale behind regaining the water in CRVL relies on this non-uniform spatial distribution of fresh water, calling for a balance between water surplus and deficit regions. For this reason, Inter Basin Water Transfer (IBWT) is suggested as a viable option to augment utilizable water resources of the Upper Awash sub-basin to reduce the significant pressure on the water supply of the rapidly developing urban and irrigation areas in the CRVL sub-basin. A water evaluation and planning (WEAP) model was used to quantify the amount of surplus water in the donor basin, when examining the hydrological dynamics of the basins. Furthermore, optimal flow diversion scenarios were generated by maintaining two baseline scenario constraints. The estimated surplus water in the rainy season is expected to contribute 18 million cubic meters (mcm), 88 mcm and 192 mcm in months June, July and August respectively under average conditions. The optimal amount of diverted water could potentially stabilize the environmental degradation of Lake Ziway and Lake Abijata by compensating for development-driven abstraction and surface water evaporation respectively.