کامران چپی

Monitoring has been widely used for studying natural phenomena; however, it has some weaknesses. The user has to perform monitoring during long times; it is a hard task specifically when the study area is located far; and it is expensive. Therefore, scientists have been looking for new alternatives to use in order to facilitate monitoring natural processes in remote areas. Analog and digital sensors, as appropriate tools, have been used for various aspects of hydrological studies and environmental engineering during the last decades in remote forest areas (Vivoni and Camilli, 2003; Hart and Martinez, 2006; Freiberger et al., 2007); however, few studies have applied sensors for runoff generating areas monitoring in watersheds. Zollweg (1996) successfully designed and tested a non-automated saturation sensor applicable for delineation of surface saturation areas in variable source area studies. Srinivasan et al. (2000 and 2002) automated the sensors designed by Zollweg (1996) and successfully calibrated and validated them for the purpose of identification of runoff generating areas in a 26-ha watershed in east-central Pennsylvania. Chaubey et al. (2006) and Leh et al. (2008) successfuJly used automated surface and subsurface sensors designed by Srinivasan et al. (2000 and 2002) for identification of critical source areas of a 1250-ha watershed in Arkansas. Sen et al. (2008) have recently used a paired surface and subsurface runoff sensors to delineate variable source areas in a small pasture watershed in Alabama. The above-mentioned sensors do not have the capability of measuring the depth of surface runoff over different time intervals to be able to monitor the variabil·ity of flow with time at various points of the watersheds. Therefore, alternative approaches are needed to study the spatial and temporal variability ofhydrologic response of variable source areas in the remote watersheds. Recent advances in computer technology, wireless communications, and digital el