Infiltration change assessment in different vegetation types (Case study: Aleshtar watershed, Lorestan provience)

Infiltration of water into the soil is a pant water supply key process. It has also an essential role in controlling surface runoff and groundwater. The objective of this study is to investigate and model the infiltration rate in different vegetation types (Annual Grass- Astragalus rhodoseminus, Astragalus ecbatanus- Euphorbia denticulata, Quercus brantii, Annual Grass). Infiltration rate was measured by double ring infiltrometer (DRI). Three samples were taken from each vegetation type, and infiltration indices and some soil characteristics were measured. One-way ANOVA was used to test the changes in infiltration indices and soil characteristics of different vegetation types and the Pearson correlation coefficient was used to test the relationships between infiltration rates and soil parameters. The performance of Kostiakov, Philip, Horton, Soil Conservation Service (SCS) and modified Green–Ampt models were evaluated by statistical criteria such as Nash-Sutcliffe (NS), efficiency coefficient (EF), root-mean-square error (RMSE), etc. The results showed that silty soil is not similar in different vegetation types. Although the infiltration did not show a significant difference in the vegetation types, the average infiltration rate in the Astragalus ecbatanus- Euphorbia denticulata type was equal to 14.4 cm/h, as the highest and the lowest value was observed in the Annual Grass-Astragalus rhodoseminus type with 6.25 cm/h, so that the former is 2.3 times larger than latter. Correlation results showed that infiltration has the highest relationship with porosity. The modeling result suggests that the modified Green–Ampt has a very high performance for estimating the infiltration rate in Annual Grass- Astragalus rhodoseminus, Astragalus ecbatanus- Euphorbia denticulata, Quercus brantii, annual Grass types with EF of 0.976, 0.945, 0.886, and 0.927, respectively. The results indicate that the infiltration varies in the different vegetation types that should be considered in the management of ground water rechage.