Flood Forecast for BAS Friday, 16 August 2019

Rainfall Distribution

The hourly rainfall forecast data was produced with WRF numerical weather model for the three days lead time over the EN region in general and over upper Baro sub-catchments in particular as presented in the hyetograph below. Based on the forecast, the estimated rainfall on 16th of August, 2019 was about 12mm per hour rainfall and for the next two days will be expected. Cumulative daily rainfall for 16th, 17th and 18th August 2019 are expected to reach 97, 112 and 62mm respectively.

Therefore, this expected increase in rainfall accumulation may likely trigger flooding in BAS sub-basin and central parts of South Sudan (See the spatial rainfall distribution maps below).

Nile Basin Initiative Dessie Road Eastern Nile Technical Regional Office Eastern Nile Flood Season Monitoring Program Addis-Ababa, Ethiopia, Email: [email protected] P.o.Box 27173-10000 Website: http://entro.nilebasin.org/ Flood Forecast for BAS Friday, 16 August 2019 From the estimated runoff, flood inudation maps corresponding to maximum water at Gambela and Itang gauging stations were generated for flood prone areas in Gambela and Itang as shown in the figures below.

Estimated Water levels

The estimated water levels based on the relation of the estimated Baro river runoff at Gambela gauge station using hydrological model, HEC-HMS, for the next three days lead time, from 16th to 18th of August, 2019.

Continuous increase in water levels at Gambela gauging stations are expected, reaching maximum of 5.83m on 18th August 2019. Therefore grater chances of higher flooding is expected in Gambella and its surroundings.

For Itang, also increasing water levels are expected, reaching maximum of 6.31m on 18th August 2019. Hence higher risk of flooding is expected in Itang and its surroundings.

Date Estimated Baro River @Gambela Gauge Station Baro River @Itang Gauge Station runoff (m3/s) Estimated Relative water levels(m) from: Estimated Relative water levels(m) from: water 3.5 4.5 5.5 water 3.5 4.5 5.5 levels (m) Low flood Moderate High Flood levels (m) Low flood Moderate High Flood level flood levels levels level flood levels levels 944.40 4.67 1.17 0.17 -0.83 5.21 1.71 0.71 -0.29 16-Aug-19 1181.00 4.97 1.47 0.47 -0.53 5.37 1.87 0.87 -0.13 17-Aug-19 1292.80 5.13 1.63 0.63 -0.37 5.51 2.01 1.01 0.01 18-Aug-19