Water erosion in mountainous areas is a major problem, especially on steep slopes exposed to intense precipitation. This paper presents the analysis of the topsoil loss using the SWAT (Soil and Water Assessment Tool) model. The SWAT model is a deterministic catchment model with a daily time step. It was designed to anticipate changes taking place in the catchment area, such as climate change and changes in land use and development, including the quantity and quality of water resources, soil erosion and agricultural production. In addition to hydrological and environmental aspects, the SWAT model is used to address socio-economic and demographic issues, such as water supply and food production. This program is integrated with QGIS software. The results were evaluated using the following statistical coefficients: determination (R2), Nash-Sutcliff model efficiency (NS), and percentage deviation index (PBIAS). An assessment of modelling results was made in terms of their variation according to different land cover scenarios. In the case of the scenario with no change in use, the average annual loss of topsoil (average upland sediment yield) was found to be 14.3 Mg∙ha-1. The maximum upland sediment yield was 94.6 Mg∙ha-1. On the other hand, there is an accumulation of soil material in the lower part of the catchment (in-stream sediment change), on average 13.27 Mg∙ha-1 per year.
The intensive agricultural use of the land affects both quantity and quality of river water in the catchment area. Such impact is visible also in the Szreniawa River catchment in the Małopolskie Voivodeship. The combination of intensive plowing and soil susceptibility to water erosion are the main causes of soil and nutrients depletion during the heavy rainfall. The aim of the study is to determine changes in the water quality in the Szreniawa River catchment compared to the agriculture use and precipitation level. The quality of surface water has been analysed in the river catchment area in three sampling points. The concentration of the total suspended soils in the samples collected after heavy rainfall in August 2017 reached a value of 837 mg·dm–3. The average concentrations of N-NO3 in the years of 2016–2019 ranged from 0.16 to 13.46 mg·dm–3, with the highest values in the summer (up to 13.46 mg·dm–3). The concentration of N-NH4 and P-PO4 in the Szreniawa water was affected by precipitation. The highest value of average concentration of N-NH4 3.00 mg·dm–3 was recorded in the autumn of 2019 in the middle section of the river. The highest value of P-PO4 0.90 mg·dm–3 was recorded in the autumn of 2019 mostly due to water erosion of the loess areas. Erosion has been caused by the short-term heavy rainfall. As a result, suspended solids, soluble and insoluble phosphorus compounds leaked to the river.
Research was conducted in selected points of the Szreniawa River basin (area 712 km2) located in the Miechowska Upland and the Proszowice Plateau. In the years 2016–2017 water samples from the Szreniawa River were taken monthly and the concentration of suspended solids was determined by filtration. The concentration of biogenic components NO3-N, NH4-N and PO4-P was determined by a colorimetric method, using an automatic flow analyser. The average concentration of suspended solids ranged from 192 to 390 mg∙dm–3 (with minimum values of 5–20 mg∙dm–3 and maximum 837–3937 mg∙dm–3) at individual points. There was an upward trend between the content of suspended solids and the concentration of biogenic components. An extremely high concentration of suspended solids happened during storm-like precipitation at the end of June 2017 and amounted to 3937.2 mg∙dm–3. The concentration of biogenic components was also highest in this period and amounted to 2.50 mg∙dm–3 of NO3-N, 0.49 mg∙dm–3 of NH4-N and 1.18 mg∙dm–3 of PO4-P. At low precipitation the concentration of suspended solids was also low (5.0 mg∙dm–3). A similar pattern was observed for the concentration of biogenic components which was 0.39 mg∙dm–3 of NO3-N, 0.17 mg∙dm–3 of PO4-P and 0.08 mg∙dm-3 of NH4-N.
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Badania prowadzono w wybranych punktach na terenie zlewni Szreniawy (o powierzchni 712 km2), położonej na wyżynie Miechowskiej i Płaskowyżu Proszowickim. W latach 2016–2017 pobierano w cyklu miesięcznym próbki wody z rzeki Szreniawy i oznaczano w nich ilości zawiesiny glebowej (metodą filtracji) oraz stężenie N-NO3, N-NH4 i P-PO4 – metodą kolorymetryczną, za pomocą automatycznego analizatora przepływowego. Średnia zawartość zawiesiny glebowej wynosiła od 192 do 390 mg∙dm–3 (min. 5–20, max 837–3937). Stwierdzono rosnący trend zależności między zawartością zawiesiny glebowej a stężeniem składników biogennych. Przykładem ekstremalnie dużej zawartości zawiesiny glebowej był koniec czerwca 2017 r., gdy po opadach o charakterze nawałnicowym wynosiła ona aż 3937,2 mg∙dm–3. Wtedy też stężenie składników biogennych było największe i kształtowało się na poziomie 12,50 mg∙dm–3 N-NO3, 0,49 mg∙dm–3 N-NH4 oraz 1,18 mg∙dm–3 P-PO4. W przypadku niewielkich opadów zawartość zawiesiny glebowej była mała i wynosiła 5,0 mg∙dm–3, a stężenie N-NO3 wynosiło 0,39 mg∙dm–3, P-PO4 – 0,17 mg∙dm–3 i N-NH4 – 0,08 mg∙dm–3.
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