In arid and semiarid regions, water is the most important of the natural resources, because it controls the maintenance of life and economic development. Sometimes, groundwater is the only source of water in those regions. The amount of groundwater depends on the replenishment that is a complex function of the climatic regime, nature of the soil and substrata, vegetation cover, and depth to groundwater level. In this connection, the infiltration process in the arid to hyperarid part of a sand desert in Saudi Arabia was studied. Soil moisture was monitored using the time domain reflectometry (TDR) technique and different types of flexible TDR rod and Taupe cable sensors to finally estimate infiltration amounts. Monitoring of soil moisture shows that seasonal fluctuations of moisture content profiles within the unsaturated zone are correlated well with the local climatic conditions.