ASSESSING SOIL ERODABILITY FACTOR FOR RUSLE2 IN BAHLUIEȚ CATCHMENT, EASTERN ROMANIA

Abstract

In Romania, there is a lack of methodology for soil erosion estimation, in the sense that although a soil loss estimation equation similar with USLE is used, the factor estimation is not comprehensively covered. That is why we have turned to RUSLE2 methodology to compute soil erodability factor (K) for Bahluieț catchment (Eastern Romania). We have used a soil profile and soil unit legacy database for estimating K values from granulometry sand, silt and clay values. We tested the two equations proposed by the RUSLE2 methodology, but we have chosen to use the values from only one of them, because for the other the estimated value were incomprehensibly high. For comparison, we have used also an estimation made by the EUROSOIL JRC and based on the same equation for which the estimation failed. The majority of the soils from the study area are from the clay loam, sandy clay loam, sandy loam and loamy texture classes. The mean K factor value is 0.0181, corresponding to soils with low erodability. The K values stretch from 0.01 to 0.03, the majority of the soils in the study area having K values in the range between 0.01 and 0.022. We observed a spatial pattern in K values distribution which is explained by the lithology of the study area, the central, southern and eastern areas having bigger soil erodability, because of the loamy texture, while western areas have a sandy loam texture, which give lower soil erodability values. Our result is lower than the estimation of EUROSOIL JRC modelling, which for our study area has a mean of 0.043, and the majority of values falling in the 0.026-0.054 range. Our opinion is that these values are too big, since the texture of the soils is clayey to sandy loam. This conclusion seems to be sustained also by the soil erosion values and sediment yields obtained using our estimated K values, which are consistent with the soil losses and sediment yields reported in the study area, conclusion which cannot be drawn for the estimation of EUROSOIL JRC data (which will give overestimated soil erosion and sediment yield values).