Elaboration of tracing irrigation farms using GIS.

The methodology is applied for reducing non-essential irrigation and spill outside of the main rice irrigation period on the Usangu Rice Plain in Tanzania. The downstream National Park is during the low flow season most vurnerable for zero flow in the river

Comparison of 10m resolution images resampled to 5m, with sporadic high resolution images of the weir results in a solid analysis. The conclusions of the remote sensing is counter checked with videos from social media of swimming youth at the weir. The drying of the overflow is associated with out-of-irrigation-season diversion of all low flow in the river, estimated at 2 cumecs. As long as zero flow is still common in the downstream Natural Park there is adequate reason to reduce non-essntial abstraction and spill and monitor the overflow of the weir during the critical low flow period,