METHODOLOGY AND PRACTICAL IMPLEMENTATION STUDY THE CURRENT STATE OF DRAINAGE SYSTEMS IN VOLYN REGION (ON THE EXAMPLE THE OKONSKA DRAINAGE SYSTEM)
Authors: Fesiuk Vasyl , Netrobchuk Iryna , Fedin Ivan 
Published: August 2023

The article proposes a methodology for studying the current state of drainage systems using remote sensing methods and conducts a practical assessment of the current state of one of the typical drainage systems of Volyn region, namely the Okonska drainage system.  The Okonska drainage system is a typical drainage system in Volyn region. It is quite large. Its area is 3130 hectares, including 1405 hectares drained by the pottery drainage. Therefore, a representative site in the east of the Okonska system, which surrounds the village of Kukly in a semicircle from the north, west and south, was selected for a detailed study. This section was put into operation in 1977. It consists of 9 reclamation canals and 52 drainage collectors with a total length of 41.45 km. Hayfields account for 42% of the structure of drained land in the study area, and pastures account for 67%. Arable land accounts for only 25%. That is, the scientifically-based requirements for the use of the system's land are mainly as hayfields and pastures with minimal ploughing and crop rotation. A detailed analysis of the current state of use of the drainage system's lands using remote sensing was carried out. It was found that currently, within a representative area, 45.8% of the land is not used in accordance with the designers' recommendations. This is most often due to ploughing of hayfields and pastures. However, some fields (No. 1-3, 12) also have this tendency: according to the designers' recommendations, they should be completely ploughed. However, flooding and waterlogging of certain parts of the fields cause them to be withdrawn from active cultivation, naturally becoming alkaline and overgrown with sparse shrubs. This is due to insufficiently effective field drainage, when excess water is not fully drained from the fields during spring floods. Only three fields have met the recommendations: fields 5, 14, 15. These fields are designated as pastures and hayfields. Their relief is complicated by numerous negative relief forms (saucer-shaped depressions). They are regularly flooded and constantly waterlogged, overgrown with sparse shrubs. Ploughing these fields is currently impossible or impractical. On all other fields, the designers' recommendations are partially or completely violated. Fields 13 (6.17%) and 6 (16.04%) have the lowest proportion of land use contrary to the project. These are partially ploughed pastures used as vegetable gardens. The worst situation is with the use of fields 8 and 11. These hayfields have been completely ploughed up. There are widespread deflationary areas in strips, and there are no mosses or overgrown shrubs.  The current state of use of drained land has negative consequences: reduction of the area of agricultural land suitable for use, especially arable land, spread of unfavorable exogenous processes (flooding, rewetting, deflation, overgrowth of areas), depletion of peat soil horizons, excessive anthropogenic load, which causes soil degradation, pollution of surface runoff due to excessive ploughing, noncompliance with coastal protection zones, formation of illegal landfills, and changes in the carbon cycle.

Keywords: reclamation, drainage reclamation, reclamation system, hydrotechnical structures, current state of use of drainage system lands, measures to improve the system's functioning and increase environmental safety.