The base of Damagaram Mounio, study area, outcrops in the eastern part of the Zinder region. In this zone, discontinuous aquifers are located in fractured, fissured and/or altered horizons of Precambrian granitoid and metamorphic formations and young fissured granites. They are essentially captured by fodder whose very high failure rates can exceed 50%. In addition, the flow rates of positive fodder are less than 2 m3/h for more than 85% of them. Thus, the problem of water resources is acute. In this densely populated area, this lack of water for the population’s food is aggravated by the levels of certain chemical parameters, including nitrates in particular, which greatly exceed the drinking water standards for human consumption, hence the present study. the main objective of which is to determine the origins of nitrates in the groundwater resources of the area. The methodological approach based on the sampling of hydraulic structures capturing the aquifers of the basement, the analysis of the physico-chemical and isotopic parameters of the waters of several boreholes, the determination characteristics of nitrates, led to several interesting results. Thus, the isotopic contents of Nitrogen 15 (15N), obtained in the groundwater of the area, varying from 0 to 7.2, thus showing that these nitrates could come from the nature of the soil (quagmire around the points) and chemical fertilizers, ureas and fertilizers used in the study area. This study has shown that in the basement area of ​​Damagaram Mounio, nitrates have a superficial origin. The nitrate contents of the waters of the Damagaram Mounio basement aquifers vary from 0.22 to 313.3 mg/L, with an average of 72.23 mg/L, and a standard deviation of 62.23. Thus, 32% of the modern structures sampled have nitrate levels above the acceptable limit value for drinking water set at 50 mg/L, according to the standards of the World Health Organization (WHO); these waters are unfit for human consumption. The spatial distribution of nitrate levels in groundwater in the area showed that these are more accentuated between the towns of Damagaram Takaya and Birni Kazoé, which are characterized by values ​​above 100 mg/l. Furthermore, the relationship between nitrate levels and electrical conductivity values ​​of water showed that the mineralization of groundwater in the area is controlled by nitrate ions.