| Abstract | Hidrauličke značajke tla utječu direktno na tok vode i transport tvari u nesaturiranoj zoni tla te predstavljaju temelj za provedbu numeričkih simulacija i procjenu prognostičkih modela. Na terenu (lokacija Jazbina, Zagreb, tip tla pseudoglej obronačni) su se prikupili porušeni uzorci tla te su se odredile fizikalno kemijske karakteristike tla (tekstura, sadržaj organske tvari, pH, električna vodljivost EC). Procjena hidrauličkih parametara tla provedena je u laboratoriju na neporušenim uzorcima tla volumena 250 cm3 pomoću HYPROP automatiziranog sutava koji se temelji na evaporacijskoj metodi. Uzorci su se prikupljali iz površinskog sloja u 3 ponavljanja na vrhu padine (SFL 1) i dnu padine (SFL 2). HYPROP i WP4C uređajima, dobiveni su podaci o sadržaju vode, vodnom potencijalu te hidrauličkoj vodljivosti tla. Na temelju prethodno dobivenih podataka pomoću HYPROP-FIT programa dobivene su krivulje hidrauličke vodljivosti i retencijske krivulje tla. Za evaluaciju retencijskih krivulja tla korištena su četiri različita modela: Brooks Coreyev (BC), Fredlund Xingov (FX), Kosugiev (K) i van Genuchtenov model (VG). Vrijednost hidrauličke vodljivosti Ks za lokaciju SFL 1 kretala se od 0,2 cm/dan (BC model) do: 1,89 cm/dan (FX model). Hidraulička vodljivost za lokaciju SFL 2 kretala se od 0,00470 cm/dan (BC model) do 28,7 cm/dan (FX model) što ukazuje na velike razlike između dobivenih vrijednosti korištenih modela. Najmanja vrijednost hidrauličke vodljivosti za obje lokacije dobivena je BC modelom te najveća vrijednost dobivena je FX modelom. Najveću pogrešku modela RMSE za lokaciju SFL1 pokazao je BC model čija je vrijednost pogreške za RMSE_TH iznosila 0,0164 i 0,2980 za RMSE_K. Najmanju vrijednost pogreške za lokaciju SFL 1 pokazao je model VG čija je vrijednost pogreške RMSE_TH iznosila 0,0103 i za RMSE_K 0,2169 što ukazuje na najveću pouzdanost od sva četiri korištena modela. Za lokaciju SFL 2 vrijednosti RMSE pogreške značajno su varirale između modela, a najmanju pogrešku pokazao je FX model pri čemu je RMSE_TH iznosio 0,0077 i RMSE_K je iznosio 0,3062. Najveću pogrešku RMSE za lokaciju SFL 2 pokazao je BC model čija je vrijednost RMSE_TH iznosila 0,0159 te za RMSE_K vrijednost 0,4671, čime je i na ovoj lokaciji BC model pokazao najmanju pouzdanost. Rezultati ukazuju na relativno ujednačene rezultate retencijskih značajki tla primjenom različitih modela i izgled samih retencijskih krivulja uz izražene razlike u procjeni pojedinih parametara što može dovesti do velikih razlika prilikom primjene numeričkog modeliranja toka vode i transporta tvari u tlu. |
| Abstract (english) | Soil hydraulic properties directly affect the water flow and solute transport in the soil vadose zone and represent the basis for the implementation of numerical simulations and the application of prognostic models. Disturbed soil samples were collected in the field (Jazbina, Zagreb, soil type: pseudogley on hillslope) and the physical-chemical characteristics of the soil (texture, organic matter content, pH, electrical conductivity EC) were determined. Evaluation of hydraulic soil parameters was performed in the laboratory on undisturbed soil samples with a volume of 250 cm3 using a HYPROP automated system based on the evaporation method. Samples were collected from the surface layer in 3 replicates at the top of the slope (SFL 1) and the bottom of the slope (SFL 2). With the HYPROP and WP4C devices, water content, water potential and hydraulic conductivity of the soil were determined. Based on previously obtained data, the hydraulic conductivity curves and soil water retention curves were reproduced using the HYPROP-FIT program. Four different models were used to evaluate soil retention curves: Brooks Corey (BC), Frendlund Xing (FX), Kosugi (K) and van Genuchten model (VG). The value of hydraulic conductivity Ks for the SFL 1 location ranged from 0.2 cm/day (BC model) to 1.89 cm/day (FX model). The hydraulic conductivity for the SFL 2 site ranged from 0.00470 cm/day (BC model) to 28.7 cm/day (FX model) indicating large differences between the obtained values of the models used. The lowest value of hydraulic conductivity for both locations was obtained by the BC model and the highest value was obtained by the FX model. The largest RMSE model error for the SFL1 location was shown by the BC model whose error value for RMSE_TH was 0.0164 and 0.2980 for RMSE_K. The lowest error value for the SFL 1 location was shown by the VG model whose error value RMSE_TH was 0.0103 and for RMSE_K 0.2169 which indicates the highest reliability of all four models used. For the SFL 2 location, the RMSE error varied significantly for each model and the lowest error value was shown by the FX model where RMSE_TH was 0.0077 and RMSE_K was 0.3062. The largest RMSE error for the SFL 2 location was shown by the BC model whose value RMSE_TH was 0.0159 and for the RMSE_K value 0.4671, which showed the lowest reliability at this location as well. The results indicate relatively uniform results of soil hydraulic parameters using different models and the shape of the retention curves themselves with pronounced differences in the assessment of individual parameters, which can lead to large differences in the application of numerical modeling for water flow and solute transport. |
