Rainfall forecasting for operation of Laos’ Nam Ngiep 1 hydropower plant

Date: 2017-2020

What was done?

An analogue rainfall forecasting model which integrates numerical weather prediction (NWP) and satellite data was developed and deployed operationally to support the operation of the Nam Ngiep 1 hydropower plant in Laos. The forecasting system provides 1-hour rainfall forecasts during the first 48h, and 3-hour rainfall forecasts thereafter and up to 7 days into the future. This work was undertaken as sub-contractors for Artelia Group.

Modelling and implementation details:

In the proposed precipitation model, global NWP is the driving force and post-processing techniques are used to improve the quality of and downscale NWP outputs for catchment-scale applications. The NWP product adopted in the precipitation model was the GFS, which was found to outperform NVGEM.

Two post-processing techniques were considered and evaluated, namely frequency distribution matching and analogue downscaling, with the former displaying an overall superior performance. Different satellite products were tested for use as reference for real-time calibration of the post-processing routines. These included IMERG Early, GSMaP and GSMaP now. Ultimately, IMERG was adopted on grounds of quality.

The Delft-FEWS platform was adopted for operational deployment of the rainfall forecasting system in 2019. Training on the use of the operational system was delivered to staff members of the Nam Ngiep 1 Power Company, who are now in charge of its operation.