AbstractEstimate is made for the possible reduction of nutrient export from the drainage basins of tributaries of the Kuibyshev Reservoir through the introduction of the best available technologies of agricultural production. The activity of more than eight hundreds of agricultural enterprises in the reservoir drainage basin was analyzed. Different types of underlying surface were classified with the use of space photographs. Mathematical simulation was used to calculate first the distributed agricultural nitrogen and phosphorus load onto the drainage basin and next the export of nutrients with river runoff into the reservoir either under current conditions or after the introduction of the best available technologies (BAT) to agricultural production. The simulations show that, under the conditions of medium water abundance, the total export from the drainage basins of the Sviyaga, Kazanka, Mesha, and Bol’shoi Cheremshan will decrease by about 367 t N/year and 12 t P/year after the introduction of BAT into the agricultural practice. The application of nitrogen and phosphorus into the soil as components of mineral and organic fertilizers in most administrative territories of the region under consideration was found to be less than the nutrient demand of agricultural crops, resulting in the gradual depletion of such elements in soils and a decrease in the risk of their migration into water bodies.