Long-Term Dynamics of Nitrogen and Phosphorus Concentrations in Subsoil Water in Ivankovo Reservoir Drainage Basin
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ORATION OF THE VOLGA
Long-Term Dynamics of Nitrogen and Phosphorus Concentrations in Subsoil Water in Ivankovo Reservoir Drainage Basin N. V. Kirpichnikovaa, *, E. E. Lapinaa, and V. V. Kudryashovaa aWater
Problems Institute, Russian Academy of Sciences, Moscow, 119333 Russia *e-mail: [email protected]
Received February 13, 2020; revised February 13, 2020; accepted March 8, 2020
Abstract—The article presents the results of summer dry-season areal surveys of subsoil water chemistry in the drainage basin of the Ivankovo Reservoir in the Volga segment from Tver City to Dubna City over period 1981–2019. The zone of subsoil water pollution by nutrients has shifted from the anthropogenic landscapes of agricultural fields to residential areas: horticultural and cottage settlements. Local zones of subsoil water pollution by nutrients still persist under fertilized fields and large cattle farms. The long-term dynamics of the major diffuse pollution sources and the regime of nutrients in the Ivankovo Reservoir are discussed. Keywords: nutrients, eutrophication, cottage settlements, subsoil waters DOI: 10.1134/S0097807820050103
INTRODUCTION Studies of the effect of pollution sources on the state of subsoil water in the drainage basin of the Ivankovo Reservoir have been carried out since the late 1970s. Since the early 1980s, the status of the Ivankovo Reservoir has been defined as eutrophic [7]; therefore, studying all sources of nutrients entering the river network and the water body, as well as the possible ways of their transformation, is still an important scientific problem. The nutrient runoff has been always regarded in the context of surface runoff formation in typical fragments of the drainage basin, and this runoff is very rarely studied as transit through subsoil water. The main objective of these studies was to analyze the dynamics of nutrient load due to diffuse pollution sources and the spatial variations of subsoil water chemistry. THE SIGNIFICANCE OF THE PROBLEM AND CHARACTERISTIC OF THE OBJECT The study area is the southeastern part of the Ivankovo Reservoir drainage basin within Konakovo raion from Tver City to Dubna City. The Ivankovo Reservoir water area is 327 km2, its length is 127 km, and shoreline length is 520 km; its active storage capacity is 1.12 km2, and the total drainage area is 41000 km2. The reservoir is the main source of drinking water supply to Moscow. Up to 82.1% of the annual river runoff in the drainage basin pass during spring flood, the autumn low-
water season accounts for 13.5% of river runoff, and winter runoff amounts to 4.4% of the annual runoff volume. Note that the share of the annual subsoil water runoff in dry years can be 15–20% [4]. The discharge of groundwater into the Ivankovo Reservoir is largest during winter low-water season when water drawdown is taking place [4, 10]. The climate in the region is moderately continental, the normal monthly temperature of the warmest month is +17.8, and that of the coldest month is ‒9.8°С, the normal annual precipitation is 654 mm (over
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