ESTIMATION OF DIFFUSE RUNOFF COMING INTO THE UPPER VOLGA BASIN WITH DRAINAGE WATER CONTAINING BIOGENIC SUBSTANCES
JOURNAL OF MECHANICS OF CONTINUA AND MATHEMATICAL SCIENCES
The paper contains an assessment of the possible coming of polluting biogenic substances into the water bodies of the Upper Volga basin from the functioning reclaimed lands, the area of which is 961.12 thousand hectares or 44% of the total reclaimed land in the region. Drainage systems are located mainly on the floodplain lands of the tributaries of the Volga river, from which the surface and drainage runoff are uncontrollably discharged into the river network, which causes significant damage
... the water bodies of the basin. The calculation of surface runoff is made on the basis of the natural reclamation zoning of the territory, which made it possible to identify homogeneous reclamation subzones and provinces characterized by the same type of the surface runoff formation. To calculate the content of biogenic substances in the drainage runoff, a justification of its volume was made depending on the amount of precipitation, the discharge of flood waters and drainage parameters. Assessment of pollution of diffuse runoff was performed using empirical dependencies for each biogenic substance and its form in the soil: nitrogen, phosphorus and potassium. The calculation took into account the content of this biogenic element in the soil, its rate of application with mineral and organic fertilizers, solubility and transition into mobile forms, the washout of the absorbed substance by solid runoff and of the dissolved substance with the surface runoff, as well as absorption of biogenic elements by agricultural plants during the growing season. It was shown that nitrogen and potassium compounds play the main role in the pollution of both surface and drainage waters, the amount of which is 98% of the total amount of pollution, while phosphorus compounds have a lesser impact. The total annual volume of surface runoff in the Upper Volga basin for average long-term conditions is estimated at 216,698 thousand m 3 , drainage water -1,564,436 thousand m 3 , which is 7.3 times more. The washout of biogenic pollutants approximately amounted to 12.32 thousand tons/year, of which the main share of 8.08 thousand 553 tons/year (65%) falls on drainage waters, which requires the development of protective measures to reduce and clean the drainage runoff.