Evaluation Determining of Hydraulic Conductivity Methods (Case Study: Mashhad Area)

Soil hydraulic conductivity (K) is an important parameter in designing drainage systems and estimating water flow in soils. Where water table is close to crop water root zone, saturated K is commonly determined by using Ernest auger hole, double auger hole and piezometer methods. For determining K above water table, methods such as pumping to hole, Golf permeameter and inverse auger hole are available, where the latter is the mostcommon. Under laboratory conditions, constant and falling head methods are used. The purpose of this research was to determine K values of different soils in Mashhad area using inverse auger hole method and compare the results with laboratory findings. Moreover, the result of these two methods was then compared with estimations made via Rosetta and Rtec computer models. The results indicated that K obtained by using auger hole method was about 1.50 times higher than the values derived from pumping to hole laboratory method. And K values of laboratory was half of pumping to hole method values and computer models of Rosetta and Retc K estimated K that 68%, 165% biger than K of pumping to hole method. Rosetta model also showed close estimations with pumping to hole method and the same difference minerals was considered in the model. However, when only the soil textural class was used in Rosetta and Retc models, the results showed considerable difference with measured values in the field.