Groundwater Quality Origin Mechanism,and Exploitation In The Niger Basin Under Climate Change And Pollution Impact

Groundwater is a vital livelihood resource for economic and social development,and it is generally the primary water drinking resources for the population living in the region.The population growth rate is increasing by 3%per year,so is the demand on the groundwater,but this is affecting its quality and quantity.The degradation of groundwater quality is due to human activities and the lack of environmental protection policies.Currently,uncontrolled increasing urbanization,industrial activities,agriculture,and mining production are hurting water reserves in the study region.Agriculture activities taking place within the region are used in the agricultural field a considerable amount of mineral fertilizers and pesticides that can seep into the groundwater.Also,mining operating and uncontrolled traditional gold panning is a new booming industry within the area recently,and that constitutes a real ecological disaster and a challenge for the environmentalists.These activities produce significant recyclable and non-recyclable wastes without any treatment and remediation plan.Groundwater contamination by some of these heavy metals such as lead,cadmium,cyanide,chromium,mercury,and arsenic have been reported in many mining operation areas.In addition to multi-source pollution comes the most significant threat from climate change.Groundwater reserves are substantial,but the current climatic conditions do not allow a complete reconstitution of extracted water for different purposes.The observation boreholes in the region show an increasing groundwater depletion trend in the recent decade that can be one of the indexes and consequences of climate change.The present study discusses groundwater vulnerability using the DRASTIC model to assess the potential areas of groundwater pollution.The nitrate validates groundwater vulnerability from domestic waste,sewer leakage,liquid waste,solid waste,and other municipal wastes and agriculture pollution.In addition to classic validation by nitrate that considers only the anthropogenic pollution,this study used heavy metal which coming from mining and industrial activities.The research aims to determine groundwater pollution origins,mineralization process,and availability under climate change and pollution challenges for better management.The study assesses groundwater types by using the classical hydrochemical method combining with multivariate statistic methods.These approaches indicate that the majority of samples is Ca2+-Mg²⁺-HCO3-and Na+-HCO3-type depending on the different aquifers and constitute by fresh groundwater.Mg2+and Ca2+may react with HCO3-precipitating as calcite and dolomite,and the bicarbonate type presence in groundwater suggests that it is young water.The NaHCO3 groundwater type derived mainly from the ion exchange process.NaHCO3 type indicates paleo-marine depositional environment or passing through paleo marine channels and the calcium of standard Ca-HCO3-groundwater type exchanges with the sodium.The interactions water rock is characterizing the groundwater that indicates the chemical alteration of the rock-forming minerals influencing its quality by a dissolution.The?2H and?18O stable isotopes show the evaporation importance in the basin and recharge with recent rain.Multivariate statistical methods,notably PCA and HCA,confirm affinities between the aquifers and identify three main clusters grouped into two water types.The research also assesses the potential areas of groundwater pollution by using a DRASTIC model used in for the first time in this vast region facing to multi-source pollution combines with the climate change impact.The GIS is using in the model considers assessing the groundwater vulnerability by superimposing different spatially referenced hydrogeological parameters that are affecting groundwater contamination.About 500samples for nitrate among the study area and thirty?30?water samples from the mining region were collected and examined for determining the heavy metal presences in the groundwater.The results exhibit that 6.43%the area is of very high vulnerability,52.12%is of high vulnerability,36.89%is of moderate,4.57%is of low,and 0.004%is of very low.The sensibility analysis in the region indicates the depth of the water table,the recharge condition,and the impact of the vadose zone are the most critical environmental factors controlling vulnerability.Nitrate concentration is higher than the international standard in the region,and the results indicate the maximum value of 94.71 mg/L on the very high vulnerability class,92.65mg/l on the high vulnerability class,and 72.77 mg/l on the moderate vulnerability class.Besides,310 placers and two operates mining is located on the high vulnerability area then one hundred nine?109?and three operate mining on the very high vulnerability area.The heavy metal is using to appreciate their impact on groundwater and the result indicate that lead level with a maximum value of 0.702 mg/L,chromium with 0.0588 mg/L and arsenic with 0.54 mg/L is above the global standard?WHO's?,and cadmium with 0.0013 mg/L and cyanide with 0.006 mg/L are below this international standard.This research will discuss groundwater exploitation based on the hypothesis of exploitation and water need per province yearly,highlighting their availability to support the supplying for a different purpose.Groundwater exploitation is not quantified in most villages and towns in the study area and therefore,does not have a strong exploitation record.The hypothesis of exploitation and water requirements for different purposes based on the person and livestock's need per day according to the supplying system number,productivity,and pumping time.The model of groundwater flow is used to estimate water budget in the region and the hydrogeology of the area consists of two mains type of superimposed aquifer systems that are:the sedimentary-inter-granular&fracture aquifer and the unconsolidated aquifer.These two aquifer systems have a hydraulic connection through a fractures system that allows considering the model as a single layer.Few works have been done in the area,and some of the hydrodynamic parameters are not available or poorly appreciated.Aquifer's main natural outlet is represented by the permanent rivers crossing the region,their semi-permanent streams and swampy lowlands.The evapotranspiration in areas where the water table is close to the surface represents the second natural outlet in the water balance of the aquifer system.Groundwater extensive exploitation would require the development of a strategy that considers the qualitative and anthropogenic aspects.This research is an essential tool in groundwater monitoring that can be useful to assist planners,decision-makers,managers,and local officials in water supply for different uses.Policymakers can also use hydrochemical characteristics to develop integrated water resource management policies.