The Effects of Polluted River Water to the Riverside Groundwater , Case in Niger River in Koulikoro

Ground water demand is increasing in many African nations due to a number of factors. The growth of population, climate change, increase pollution of rivers, and insufficient number of purifying stations and waste water treatment (or almost nonexistent) have pushed to the water authorities for exploitation of underground water. These underground /groundwater have a relationship with surface water. Then what can be the effects of polluted River to its riverside groundwater? To explore the answer of this question and for the prevention sustainable and a better integrated management of water resources, we will do in-depth study on “the relationship between river water and riverside ground”. In Koulikoro region the results of this research show that Surface waters have poor bacteriological quality, the amount of total coliforms is very high, and accordingly Niger River’s waters are not allowed for consumption without treatment. However the river water can be safely used for laundry, bath, sports and recreation. Generally the Groundwater quality is good despite increased salinity has been observed sporadically. We found also that for the entire region of Koulikoro the average infiltration rate is less than 19.8% of the gross rainfall.


The Problem Statement
Water is a precious natural resource in the world and without it life cannot exist.According to the latest assessment report of new age international publishers, there is about 97.2% to global water resources in the world is salt mainly in oceans and 2.8% is only available as fresh water.Out of this 2.8% of fresh water, about 2.2% is available as surface water (glaciers, icecaps, lakes, and an others forms) and 0.6% is groundwater.Groundwater is a huge resource but limited.
Groundwater demand in many African nations is greatly increasing due to a number of factors: the growth of population, climate change, increased pollution of rivers, and insufficient number of purifying station and wastewater treatment.Inadequate sanitation has led waterborne diarrheal and other enteric illnesses to become the leading cause of death on the continent, accounting for over 40% of all child deaths in the Sub-Saharan region (McMurray, 2007).Groundwater is also one of our most important sources of water for irrigation.

Exploration of Importance Problem
At one time, groundwater purity and availability were taken for granted, and it was a hidden resource; but over the past few years, it is undeniably true that polluted water is becoming the biggest threat to human live.For better management of fresh water resources, it is necessary for water scientists to understanding the effects of polluted river water to the riverside groundwater.This will raise the question of understanding the interaction between river water (surface water) and groundwater.In other words, understanding what can be the consequences of polluted River to riverside groundwater.However, it's very difficult to observe and measure the interaction.Thus we have to understand three phenomena to know: Infiltration, percolation and interflow.
Infiltration is movement of water into and through soil.The percolation is described as being the properties related to the connectivity of large numbers of objects which individually have some spatial extent, and for which their spatial relationships are relevant and statistically prescribed.The three basic assortments that percolation theory came are: bond, site, and continuum.In hydrology, interflow is the lateral movement of water in the unsaturated zone that returns to the surface or enters a stream prior to becoming groundwater.

Objectives
The major scope of this research will cover to the following.
To characterize the aquifer system in Koulikoro region.
To investigate and advice to riparian populations on groundwater related issues.And also regarding potential water problems.
To create an analytical studies of aquifers in order to lay the foundations of sustainable and rational management of water resources in Koulikoro region of Mali.

Description of the Study Area
The region of Koulikoro is bordered by the Islamic Republic of Mauritania to the north, the region of Kayes to the west, by Guinea and to the region of Sikasso to the south, and by the region of Segou to the east.With an area of 90,210 km2, or 7.2% of the Mali's territory, Koulikoro Region is divided into seven (7) largest cities "cercles" (Table 1).The region is situated entirely within the tropical zone.In the region, there are four types of climates: the north Guinean climate, the south Sudanese climate, the North Sudanese climate and the South Sahelian climate, with alternating during the year a rainy season (May to October) and a dry season (November to April).The average annual rainfall is between 700 to 1200 mm in a normal year.The average temperatures are between 26 and 33 °C.
Koulikoro has a large river system which includes the Niger River with a long of 250 km; The Baoule, the Bagoe, the Baninfing, Sankarani and Bani with 120, 90, 70, 40 and 20 km long respectively.The Niger, Baoule and Sankarani are permanent streams.The 2012/2013 hydrological year has been marked by the maximum flow of about 199 occurred on 21st May 2013 and the minimum flow of 149 which occurred on 29th May 2013 with a year mean volume of 179.The total flow volume at Koulikoro, from 1st June 2012 to 30th April 2013 was about 35.68 Km 3 (http://nigerhycos.abn.neJanuary 13, 2014 07:05PM ).The region also has ponds and lakes.Koulikoro water resources come mainly from the rains that are only meteoric waters which the region enjoys.According to PIRT (Projet Inventaire des Ressources Terrestres) the different types of soils in Koulikoro are characterized in their majority by their poverty, their acidity and their structural instability.Table 2 below gives the soils and their characteristics.
Koulikoro is a major trade and industrial town on the Niger River and provides opportunities for navigation.

Results
We found (Figure 7).water from aquifer resources and more than 60% in Koulikoro region.We realized that: the information on the residence time of water in groundwater aquifer is necessary in the field of drinking water supply especially for risk analysis in cases of pollution and for the analysis of ecosystems.It is a commonplace that ecosystems depend on groundwater, vice versa.We know that the isotopic parameters of a stream vary very little.We have also rendered account that the knowledge of water balance is very important, which can be determined and managed by meteorological, hydraulic and hydrological studies.Those will take into account all the elements of the balance (rainfall, Evapotranspiration, runoff, infiltration, recharge and discharge).
In the closest flooding area to the River, the aquifer Continental terminal/Quaternary recharges by River would have estimated of order of 100,000 (Anonym, 1990).An area of 510 located a few km from koulikoroba (specified surface by the arrow Figure 1) the aquifer recharges by River would have estimated of order of 500 .

Figure
Figure 2. P Figure

Table 1 .
Areas and populations

Table 2 .
Soils and their characteristics 2.1 DescriptionTo achieve our goals, we have developed a survey based on the documentation and on the collection of data.Some of our data were obtained from the Sigma 2 database.The Sigma 2 (Geographic Information System of Mali)