We present a multi-satellite constrained water budget approach that combines SWOT Ka-radar altimeter and ICESat-2 ATL13 photon counting lidar measurements. The work presented here was conducted on the world’s largest gravity fed irrigation scheme located in Sudan which has an area of approximately 8,800 km². The SWOT River SP v2.0 product provided Blue Nile boundary water surface elevation (WSE) values at 76 satellite passes (November 2023 – December 2024). ICESat-2 ATL13 v007 provided canal interior WSE values along 79 different canal reaches at 17 satellite passes (April 2023 – November 2024). For a total of 185 proximity matched pairs, sensor coherency analysis yielded R = 0.989, RMSE = 3.63 m and a systematic bias of +1.33 m — a value that can be physically interpreted as the hydraulic gradient that drives gravity fed flow, not a result of some type of calibration error. To further constrain the annual water balance, evaporation / transpiration (MODIS MOD16A2 GF), groundwater storage (Grace FO) and climate-based precipitation (CHIRPS V2.0) were incorporated into the model. Additionally, our modeled irrigation delivery amount for 2024 was estimated to range from 787 – 837 mm/yr, which falls within previously published estimates for Gezira irrigation records of 5 – 8 km^3/yr. A novel canal conveyance efficiency index derived from the temporal stability of ATL13 WSE revealed a mean efficiency value of 0.33 +/- 0.24 with no statistical significance found related to channel width (R = 0.20, p = 0.45), indicating management factors may play a larger role than physical limitations associated with channel infrastructure design. Ultimately, this research established a replicable and publicly accessible methodology for estimating irrigation of water budgets in areas that lack sufficient remote sensing coverage due to either data scarcity or regional conflict.
Data and code
All data and analysis scripts are openly available on Zenodo: https://doi.org/10.5281/zenodo.19490894
Submitted to Advances in Space Research; currently in editor review.
Author: Shobha Mourya Dumpati, FGS, FRGS
Leave a Reply