The Lake Chad Basin Commission (LCBC) undertook the setting up of the regional data base (RDB) in 2012. This RDB is the outcome of the MoU signed by the LCBC Commissioners in 2008 during the 54th ordinary session of the Council of Ministers held in Abuja (Nigeria) on the data sharing among the member countries. The RDB is organised around the environmental and socio-economic information system of the Lacbo (SIEL), which is a dissemination platform of the data via the LCBC website (Intranet/Internet).
The search of data on the pollution of the surface and ground waters started in Chad, which is the pilot site of the project. It is included in the management of the sanitary and chemical risks and constitutes an activity of the Basin Observatory of the Lake Chad Basin (Lacbo), which led to the definition of a five-year action plan of which the major objectives are as follows:
Objective 1 : Acquire the basic agricultural chemical data, the flood hazards and sanitary risks based on the first quantified data;
Objective 2 : Carry on and finalise the diagnoses of the structures, which present the major risks prior to the definition and achievement of the necessary works ;
Objective 3 : Define and set up a network of the measurement of the quality of waters. Acquire the data and assess the quality of the waters in the study zone.
The list of the structures which cause pollution and nuisance is available in the report entitled « Review report for the updating of the instruments instituting the Tax on the Protection of the Environment in Chad - (Sub-component: pollution and nuisance), 1st version issued in August 2012 ».
In 2012, there were many similar structures in Chad. The most affected regions include N’Djamena, the Eastern and Western Logone, the Mayo Kebi and the Tandjilé.
Most of the polluting structures are located in N’Djamena. The Middle Chari follows as compared the national figure.
In addition, the distribution of these industries at the national level highlights the importance of several regions located upstream the Logone River and Middle Chari. Regarding the aquatic environments, one notices that the pollution potential appears at the upstream level of the Logone river and the middle level of the Chari river.
All the data available on the surface waters present heavy pollutions in the Chari River, the surroundings of N’Djamena and the Lake Chad. The WHO reference values are exceeded for potable water and relate to all the heavy metals. This outlines the impact of the industrial waste and the one of the small-scale companies as well as the lack of the waste water treatment structure prior to its inflow into the river. The situation is similar to what is recorded in the cities of Moundou and Sarh, which are other industrial centres . The waste does not contain metal items in these cities as compared to N’Djamena.
Generally, the lab tests revealed the nitrate concentrations of which values are high ranging between 14 and 58 mg/l while the natural value is close to 10 mg/l. These values express the enrichment of the environment in both nitrates and phosphates. This can turn the environment into an eutrophication.
The pollutions do not decrease at the downstream level of N’Djamena up to the mouth of Lake Chad. The environment is enriched during the rainy season due to the interflow of the urban areas. This enrichment of the environment amounts to +84% and +144% with respect to the dry season.
Regarding the bacteriological pollution, it is more visible on the linear line Guelendeng, Farcha and Douguia where fecal coliforms abound.
The situation of the surface waters in N’Djamena could be worrying. According to some studies (UNDP, 2000), the tests conducted on the fish in the Chari delta indicate that the mercury and the organochlorine pesticides have a low concentration as compared to the values of the WHO. No hazard was identified for the human health. Conversely, no information is available regarding the concentrations on water and the sediments.
The information available on the ground water mainly come from the data base of the BGR/LCBC Project as part of the German cooperation on the sustainable management of the water resources of the Lake Chad Basin, which conducted tests on close to 300 wells or boreholes. The test took into account the additional data derived from the thesis of Edith Kadjangaba about the city of N’Djamena.
The pollution of the ground water in the country is mainly attributed to the animals and the lack of specific measures with respect to all kinds of soilings. The wells meant for animals are also used by the local populations.
The background is the cause of the excess of the cations, the sodium, the sulphates, the iron and manganese. They have an impact at the organoleptic level (taste, smell, flavour) and not on the health (or in a subsidiary manner due to the laxative effect of the sulphates).
The case of the nitrogenous matters is worrying. There are 42 wells in which the 50 mg/l of nitrates is exceeded. This excess can be very important. Regarding the nitrites, 72 wells present an excess of 0.2 mg/l, which is harmful to the health in case of long term exhibition, or the frequent consumption of this water. 10 wells have nitrites concentrations above 3 mg/l, this limit is harmful to health.
As regards the Bore, the exceeding of the limit of 0.5 mg/l applies to 23 wells. The exceedings of the most strict norm (0.001 mg/l) are related to the background and do not have any impact on the health.
The nitrogen degradation applies mainly on the open wells. The fecal matters (notably of animal origin) can use the water from the well thus polluting it.
In the city of N’Djamena, the data available apply to the metallic trace elements following the thesis of E. Kadjangaba (« Hydrochemical and isotopical study of the non-saturated system – water table in the urban zone of N’Djamena : impact of the pollution », 2007). These data are similar to those of BGR/LCBC. The exceedings with respect to the WHO and EU values are also attributed to the background.
In terms of bacteriology, the data derived from the « Analysis Report of the waters of the South ofn Chad, N’Djamena and its surroundings » (Nambatingar Ngaram », 2007). All the water samples of the Chadian Utilities Company (STEE) do not contain coliforms and fecal streptococcus. So. The treatment is effective.
There are contaminations in the other distribution sites such as most of the wells and two-third of the pump water. The water treatment which is done before its channeling to the pumps is not effective as three tests reveal the contamination of the water from the pumps.
Apart from the clients who use the distribution network , most of the people consume the contaminated waters. This applies to the populations of Douguia and Guélendeng who drink water from the wells and the rivers . This is the cause of most water borne diseases in this area.
Regarding the wells and the pumps, the contaminations can be attributed to the inflow and infiltration of human and animal faeces , waste water and germs in the water table, etc….)
As way forward, the setting up of the network is required to assess the evolutiuon of the quality of water and its control in line with the Water Security as defined in the Water Charter of the Lake Chad basin.
.To compare the water stations and assess the upstream-downstream evolutions, it is advisable to have some monitoring parameters. The degradations recorded led to the monitoring of the following parameters :
Physical chemistry : pH or potential in hydrogen ions, temperature, conductivity, MES : suspensive matters, DBO / DBO5, biochemistry demand in oxygen, O2 : dissolved oxygen, COT : Total organic carbon, DCO : Chemical demand in oxygen, Nitrates, Phosphates, Nitrites
Metalic trace elements
Search of the elements which are needed to assess the quality with respect to the WHO standards, or: manganese, aluminium, arsenic, bore, baryum, cadmium, chromium, copper, nickel, lead, zinc, uranium, molybdenum.
Microbiology: search of bacillus (Escherichia coli, aeruginosa, perfringens, coliform bacteria, number of colonies at 22°C and 37°C).
potentially, search of parasites : bilharziosis, onchocerciasis, dracunculiasis…
The research should target the following active matters :
The noxious active matters which do not match those which are mostly used: Profenofos, Carbendazime, 2.4 D, Carbofuran, Endrine, Lindane. We can add Carbosulfan and Endosulfan.
The active matters which are slightly noxious : Cypermethrine, Glyphosate, Diuron and Atrazine.
These researches should apply to the surface waters and sediments.
The location of the polluting pressure leads to the proposal of a minimum of 16 stations distributed on the Chari-Logone.
|Upstream Mondou||Monitoring of the polluting matter at the upstream of the basin and Moundou|
Intermediary Station: evolution of the parameters.
Monitoring of the agricultural pollution
|Logone Birni||Intermediary Station : evolution of the parameters|
|Upstream N'Djamena||« quality point » upstream N’Djamena|
|Upstream Sarh||Monitoring of the polluting matter at the upstream of the basin and Sarh|
|Bousso||Intermediary Station : evolution of the parameters|
Intermediary Station : evolution of the parameters.
|Upatream N'Djamena||« quality point » upstream N’Djamena|
|Centre of N'Djamena||Monitoring of the polluting matter in N’Djamena|
|Douguia||Monitoring of the evolution of the polluting matter at the downstream level of N’Djamena|
|Lake||Monitoring of the lake : 3 or 4 stations to be scheduled|