Development of Hydrometric Sensor Networks in Formerly Ungauged Watersheds: Lessons from Namal Valley, Mianwali

Measurement of hydrological variables in rain-fed catchments is crucial for any decision support to mitigate flood risk. This paper describes our efforts in installation of a hydrometric sensor network in the Namal watershed area in Mianwali, Pakistan. Since the valley is formerly ungauged, minimal historic on-site data exists. Our network is composed of two devices, one to measure rainfall and another to measure stream level. For sensor placement and interpolation, past satellite data is used to obtain the spatial covariances of the rainfall process. The sensor nodes are placed so as to maximize the mutual information between gauged and ungauged locations. Kriging is applied to obtain the average spatial estimate for rainfall in the watershed. A level sensor on the dam reports the variation in the reservoir water level whereas another set of level sensors is used to evaluate lag times for flows in a major tributary. Results suggest that the data adequately captures the reservoir response to rainfall. Furthermore, we find that stream level measurements in the upper catchment can produce lead times sufficiently long enough to lower the damage caused by flash flooding in the Monsoon period.