Dear Aicha El Alaoui, 

You can obtain a lot of environmental and economic macrodata from FAO and also from Africa Water Atlas.

-Africa Water Atlas

http://www.zaragoza.es/contenidos/medioambiente/onu/340-eng.pdf

-FAO Environmental and economic datasets

http://faostat3.fao.org/home/E

I do not know any database about specificly about water pollution however you can find some valuable information in following book: Groundwater Pollution in Africa, specifically in Chapter 7 where Jovanovic carries out an review about pesticide pollution in groundwater.

https://books.google.com.sv/books?id=C8_TFAP8bhoC&printsec=frontcover#v=onepage&q&f=false

I hope this information will be useful,

Best regards from El Salvador,

Alex Ribó

https://books.google.com.sv/books?id=C8_TFAP8bhoC&printsec=frontcover#v=onepage&q&f=false

http://faostat3.fao.org/home/E

http://www.unep.org/pdf/africa_water_atlas.pdf

Thank you very much. very useful

Dear Alaoui,

It is interesting to here that you want to study the nexus of economic growth & environment. You can get some data on environment by login into FAOSTAT. You will get data on Agri-environment indicators as well as emissions. I hope this helps. I wish you well in your study.

Regards,

Dennis Olila