Université Félix Houphouët-Boigny d'Abidjan-Cocody, Unité de Formation et de Recherche des Sciences de la Terre et des Ressources Minières (UFR-STRM), Laboratoire des Sciences et Techniques de l'Eau et de l'Environnement (LSTEE), 22 Bp: 582 Abidjan 22, Côte d'Ivoire
The Rainfall-related phenomena affect the hydroelectric dams functioning and productivity. In Côte d'Ivoire the trans boundary Bia River basin, hydroelectric amenagements of Ayamé 1 and 2, is no exception. Flooding has caused extensive damage in recent years to these two (2) amenagements. However, the rains nature that caused these events is statistically unknown. This study objective is to identify the rainfall events nature in the Bia basin. The statistical modelling approach has been adopted. The daily rainfall from 1941 to 2000 and rainfall higher threshold than 100 mm from 2001 to 2015 available at the Aboisso, Adiaké, Bianouan, Ayamé and Agnibilékro stations has been used.The results show that the minimum threshold for abnormal rainfall in the Bia basin is 103 mm. The rains nature identification between 2001 and 2015 reveals, eight (08) rainfall events with an occurrence probability greater than 6 years are observed. These events are consisted of four (4) abnormal rains, three (03) very abnormal rains and one (1) exceptional rainfall observed during the years 2004, 2007, 2009 and 2015.
Extreme flow events have had a significant impact on populations and their activities in recent decades. To reduce the impacts associated with their advent a analysis between extreme hydrological phenomena and climate variability is necessary. However, qualitative data accessing difficulties and explanatory variable definition of extremes hydrological phenomena limit extreme flows rate studies. This study proposes the analysis the variability of the floods and the low flows at the Bianouan hydrometric station. Thus, five (5) floods characteristics variables (QCX5, QXJA, F90p, F95p and F99p) and three (3) for, the low flows (VCN10, QJNA and F10p) were extracted daily flows from the Bianouan hydrometric station from 1 January1962 to 31 December 2005. The variability of these extremes has been studied by the trend analysis (linear regression) and of the stationarity (Pettitt and Hubert tests). The results show that for flood variables the negative trend is very significant and ruptures are observed in 1980. For low flow variables the negative trend is significant and the ruptures are observed in 1981. From this study, we can deduce that the ruptures observed in the rains and flows average in the end 1960s and early 1970s have affected later the extreme flows around the 1980s.
The water resources of the Volta watershed in Côte d'Ivoire are often destined for human consumption and the development of agro-pastoral or industrial activities. This study aims to characterize climate variability and its consequences and to analyze the dynamics of land-use on the water resources of this basin, from hydrological models and GIS. Since the rainfall decline, observed during the years 1963 to 1970, several periods of drought have been observed and have caused the disappearance of plant species, some water bodies and some areas of groundwater recharge. The determined rainfall during the period 1936 to 2002 is 1102.86mm with only a surplus of 87.30mm of which 5.68% is destined for surface runoff and 2.23% for groundwater recharge. The flow rate of rivers from 1990 to 1993 is 1.39m3.s-1 with a drying up coefficient of 6.95.10-2 j-1 and a mobilized water volume by aquifers of only 0.028km3. These parameters determine a low hydraulic potential of the basin. Dominated by tree savannah or shrubby savannah (81.17%) in 1990, the degradation of the vegetation cover of the basin has had adverse effects on water resources. However, until the year 2000, the regeneration of gallery forest and dense tree savannah (from 8.48% to 16.01%) will favor the reconstitution of some water bodies. Thus, for an effective rehabilitation of the environment, it will be necessary to reinforce the strategic plans for adaptation to climate variability.
The surface water resources in the region of Bonoua are subject to strong anthropogenic pressures created by the development and expansion of agricultural activities and also by the agro-industrial and domestic activities. This impacts the available quantities of these resources that fluctuate throughout the year. Similarly, their quality is thereby also changed. Regarding the quality of these resources how can occur at a given time of year? This concern led in this study to assess the overall quality of surface waters of Bonoua region during the rainy season. It is based on the exploitation of data from a water sampling campaign conducted in July 2014. The data were processed with the Evaluation System of Quality of Waters, referred to as "SEQ-Eau" for determining the overall water quality. The (ACPN) has also been applied to the data for the identification of phenomena causing water pollution. The results show that in general the surface waters in the region are Bonoua of "average quality" to 92.86% and "poor" at 7.14%. The responsible alteration of this deterioration in the quality of surface water is the "acidification" parameter, which contributes to 64%. Alterations "temperature" and "organic and oxidizable materials" expressed as COD and BOD 5 incidentally involved in this deterioration in the respective proportions of 14 % and 22 %. The phenomena causing water pollution is anthropogenic. They are mainly from discharges of domestic and industrial waste water and the use of chemical fertilizers in the plantations. This evaluation of the quality of surface water in the region of Bonoua is a first draft that should be complemented by other studies covering aspects such as pesticides and microbiology for better management.
This research is a contribution of indirect analyses to classic geological and structural mapping. The principles of this analysis is to combine structural streams and structural directions in the goal to find structural building of streams network. Streams were numerized under Arcview and the data of each stream was done. Frequency graphics of number and total length of streams on Strahler classification were built and interpreted with “lois des rivières”. Recognition of Structural directions was done by the building of Prud’homme main valleys and Howard drainage anomalies.
Structural streams have affected by at least point 5 in hierarchy. They are held by N30°, N60°, N130°, N160° orientations. This methodology can be applied at all ivoirian drainage system due to their tree buliding. The main valley is host by N60° direction. Others valleys are holding by N30° N130° et EO. in the landscape, structural directions are sitting as drainage anomalies as directions deviations and linear streams. These directions are well knowed in ivoirian precambrian structural context.
Daily rainfalls as they reach a certain threshold, induce severe flooding in some township of Abidjan district during the largest rainy season. This paper focuses on defining and identifying of heavy daily rainfall threshold linked in flooding over the Abidjan district.
The heavy rainfall maximum and critical occurrence period ascertainment has been possible thanks to the likelihood occurrence (from 0 to 100%). Identifying heavy rainfall threshold related to flooding-causing started with classification and definition of precipitation recorded from 2012 to 2014 over all stations of Abidjan district with the percentile. Then, using the rainfall total sliding window technic helped finding a threshold amount inducing severe flooding.
The critical period rainfall and flooding occurrence (likelihood occurrence of 75%) start from May 27th to June 22th. Rainfall total sliding and past flooding analysis revealed a threshold amount precipitation around 100 mm. Henceforth, this threshold could helped forecaster offices by issuing advisories and warnings for flooding when precipitation expected, at any location of Abidjan district, is near or exceeds the amount of 100 mm.
This study realized at Bondoukou region in north-eastern of Cote d'Ivoire. It aims to analyze hydrodynamic properties of fissured aquifers with a view to improve drinking water supply at this region. Methodology applied for this study started by mapping of fractures networks from treatment of Landsat 7 satellite images with directional filters. After that, it was established relationship among the parameters of groundwater capture and their relation with fracturing and nature of rock formation. Geostatistical analysis of specific capacity of wells from corrected last step drawdown closed the methodology. Use of remote sensing led to map 5000 fractures responsible of water-bearing-layers inside bedrocks. Productive fractures are met between 30 and 60 meters under the ground with these principals directions: NE-SW, NW-SE and E-W. Great yields are also met at weathering between 15 to 45 meters. Approximately 83, 41% of arrival water occurred in the first 30 meters of the basement. Porphyroid granodiorit produced water more than other rocks formations. Variogram structuring of Log (Q/s) revealed that this hydrodynamic parameter can be considered as a regionalized variable with a range equals to 7,36 km. This is a proof of best connectivity of fractures networks identified. Estimation of specific capacities at the whole studied area was made by kriging. All results obtained through this study contribute to best comprehension of hydrodynamic properties of aquifer at North-east of C
The workshop of the interdepartmental committee responsible for managing household waste in Abidjan (Ivory Coast) in 2007 showed that the landfill site should be chosen out of the coastal sedimentary basin to protect the groundwater of the Continental Terminal aquifer against pollution. Indeed, this aquifer provides the potable water to Abidjan populations and also assures uniformity of the price of water by the water company of the Ivory Coast. But, given the groundwater flow and the possibility of transfer of fluid between the discontinuous and continuous aquifers, is it possible that an activity taking place outside the coastal sedimentary basin of C
In Ivory Coast, the phenomenon of decline of water drilling is found in rural and urban areas in the crystalline and crystallophyllian basement. The sub-prefecture of the department Angoda Toumodi does not rest (55%). Although several factors such as the condition of equipment, operating conditions, power conditions, the lithological conditions, problems of monitoring of hydraulic and quality parameters, etc., may partly explain this phenomenon, a fundamental question needs to be asked: drilling decline is it not related to a bad implementation of drilling? Thus, this study aims to analyze the productivity of water wells in operation, implemented by the method geomorphic from geophysical measurements. The study area is sub-prefecture of Angoda which lies between longitudes 5
The climate variability has affected pejoratively the groundwater recharge in Soubre area. Thus, the simulation of surface flows is an answer to the problematic of water supply in the area. The aim of this study is the simulation of surface flows in Debo catchment by estimating flood flows. The methodology is based on the application of morphological transfer function (MTF) of DEMIURGE software (Digital Elevation Model In Urgency). It consisted of the determination of fractal parameters related to water systems, the estimation of maximum flow at the outlet, the study of the sensitivity of the simulated hydrographs based on the simulation time step. The results show that the reference time is t = 20 minutes. For simulation times different from t = 20 minutes, the geomorphologic pulse histograms (GPH) do not fit the times transfer frequency histogram. The specific flow at the outlet of the catchment is 3.394 m3.s-1 for a rise time of 31.33 hours under the assumption of a uniform effective rainfall of 1 mm. The maximum flows simulated evolve with the rainfall blade and the rushed water. For a blade of 188.08 mm past, the maximum flow rate is at least 634.111 m3.s-1. For a rise time of 33 h 20 minutes, the volumes assessed are estimated at 1.06.108 m3.
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