Abstract: In order to find the leaking laws of seasonal Dagu River in Shandong Province, some typical test sited were established in the upper and middle reaches of the Dagu River, and the field infiltration experiments were conduced based on the theory of water movement in vadose zone. Capacities of infiltration in riverbed in different vadose zones were studied. The results show that the infiltration process in the dry riverbed could be divided into two stages, i.e. the unstable infiltration and stable infiltration; the infiltration in the riverbed was affected by the hydraulic properties of vadose zone, and the infiltration rate in the upper reaches was higher than that in the middle reaches. The stable infiltration rates in the upper and middle reaches were 0.028 and 0.023 cm/s respectively. The process of unstable infiltration varied in a range of 1.5-2.0 hours, the proportion of infiltration was low in the total leakage, and it was gradually decreased with the time. Therefore, it is feasible to calculate the total leakage by using the stable infiltration rate in riverbed in flood season.

Key words: seasonal channel, infiltration, vadose zone, water movement, Dagu River