Indus river water level monitoring using satellite radar altimetry

Satellite altimetry-based monitoring of water bodies is an advanced and cost-effective approach, mainly for regions where gauge density is low, as is the case of the Indus River in Pakistan. In this study, the potential of modern radar altimetry for inland waters was studied for measuring the Indus River water levels. For this purpose, two locations were selected near the Guddu and Sukkur Barrages on the lower Indus River, where Sentinel 3A tracks are available along with gauge data. Time series gauge data were used to validate altimetry derived water heights. An excellent fit of the two datasets (with correlations higher than 0.9) is found for both locations except a few points where altimetry heights deviate from ground observed heights. One of the possible reasons for this deviation may be the difference between the data acquiring time of the two datasets. Any barrage operation between this lag time may lead to changes in the gauge data. To overcome this problem, three-day moving averages of the gauge data were used that substantially improved the results (RMSD and ubRMSE lowered to less than 45 cm). The validation of satellite-derived water heights will lead to the possibility of observing river level changes on different segments of the river system. Other than the two at the Guddu and Sukkur barrages, 16 more Sentinel 3A and 3B tracks along the lower Indus River are available. These locations are the altimetry river monitoring virtual stations supplementing the low-frequency gauging network of the River.