Using Optical Remote Sensing and Radar Altimeter Data for Lake Volume Estimation of Manchar Lake, Pakistan

Lakes are a chief source of fresh water. Variation in water volume in lakes provide crucial information about climatic changes and water resources for sustainable water management practices. Continuous monitoring of lake water resources is required particularly with regards to the growing challenges for water resource management. For that purpose, satellite based optical remote sensing imagery and radar altimetry data can be combined for the monitoring the volume of inland water bodies. Optical remote sensing provides information about the area extent of inland water bodies, and the variations in water surface height can be extracted from radar altimetry data. The study area for this research study is Manchar Lake, which is one of the largest sources of fresh water in Pakistan. Time series data of Sentinel-2 are analyzed to calculate water surface area extent using Normalized Difference Water Index (NDWI), and in parallel Sentinel-3 altimetry data for measurements of water surface height was used. Through linear interpolation, identical dates were set up for area extent data to the surface height data. Furthermore, regression analysis was used to develop a relationship between water surface height and water surface area. In this way Heron’s formula to calculate the volume of a pyramidal frustum was used by sorting radar altimetry data in ascending order and the corresponding optical remote sensing data to estimate the volume variations of the lake. The analysis of the results shows also the seasonal and yearly variation in area extent of inland water bodies and water level anomaly.