Evaluation of Spatial changes in Soil infiltration Using Experimental and Geostatistical Methods in coastal plain of Behshahr-Galugah

Infiltration plays an important role in surface and subsurface hydrology and is a key factor in the whole rain fall-run off equations. This research was carried out Behshahr- Galugah coastal plain. With attention to most agricultural crops of region are grown in this plain and the importance of water permeability in soils, permeability studies in this area seem necessary. 10 km × 8 km grid was used to sample with the grid cell size is 1000 m2. Measuring water infiltration was performed using a single cylindrical ring considering infiltration height of 1 cm and variable time. After the measurements, the infiltration rate of the soil was estimated using both Horton and Kostiakov equations and was compared to the observed values. For selection of an appropriate model evaluation criteria including RMSE, RE and NSS for each equation were used. The values of these criteria for Horton equation were 5.55, 24.61 and 0.98 and for Kostiakov equation were equal to 8.5, 64.14 and 096, respectively. The results showed that the Horton equation has more accuracy in estimation of infiltration to Kostiakov equation compared with observed values in this region. Also investigation of spatial variability of permeability rate with GS version 5 software was showed that semivariogram of variable was isotropic and there was strong spatial dependence between water permeability.