There are many proposed methods for remotely sensing meltwater depth on glaciers and ice sheets. Methods using multispectral imagery calculate depth based on the reflectance of water pixels, often in the red and green bands. Many of these methods have been shown to work well for lake depth, but they do not provide basin bathymetry. The most reliable method to calculate both depth and bathymetry uses ICESat-2 photon returns from the air-water and water-ice interfaces. However, ICESat-2 is limited by its narrow beam width and 91-day repeat cycle. Here, I propose a novel method for extracting both depth and bathymetry from paired WorldView imagery and corresponding digital elevation models (DEMs), whereby the optical depth is subtracted from the DEM water surface to calculate bathymetry. Focusing on Petermann Glacier, I show that corresponding WorldView multispectral imagery and ArcticDEM strip products can be used to augment the spatial coverage and temporal resolution of ICESat-2 for calculating supraglacial water depth and basin bathymetry. I find that a physically based dual-channel model using the blue and green bands, paired with the corresponding DEM, provides the most accurate depth and bathymetry estimates (RMSE = 0.54 m) when compared to ICESat-2 derived depths. This novel method has the potential to vastly improve our ability to monitor supraglacial hydrology and meltwater storage vs. export, which could in turn inform us about the stability of ice shelves, such as Petermann, in both Greenland and Antarctica as the climate continues to warm.