Nile flood peaks may jump this century
A basin-wide hydrology model driven by 30 CMIP6 climates projects much larger 50- and 200-year Nile floods at Dongola by 2100.
Source
Nile basin flow regimes under 21<sup>st</sup> century climate variability
Study at a glance
- Design
- Computational / modelling — SWAT+ Nile hydrology forced by bias-corrected CMIP6 members under SSP2-4.5 and SSP5-8.5
- N
- N=30 · 30 CMIP6 climates (high/median/low members per SSP run through SWAT+)
- Population
- Nile basin streamflow regimes at Dongola under 21st-century climate scenarios
- Outcome
- Projected increases in 50- and 200-year flood peaks by 2100
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Nile flood peaks may jump this century
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What hydrology model and spatial setup were used?
The delineation of watersheds, stream networks, and hydrological response units (HRUs) within the QSWAT+ model resulted in 34 subbasins and 234 HRUs, each representing unique combinations of land use, soil, and slope (Fig.
What were calibration and validation periods?
The calibration period spanned from 1984 to 1991, and the validation period from 1992 to 1997.
What they did
The authors calibrated SWAT+ (34 subbasins, 234 HRUs) to 1984–1997 gauges, bias-corrected NEX-GDDP CMIP6 rain with QQM, then ran high/median/low members of SSP2-4.5 and SSP5-8.5 through 2100 and fitted log-Pearson III flood peaks.
What they found
Historical 50- and 200-year peaks are 13,400 and 14,900 m³/s. Median SSP2-4.5 raises them to 21,800 and 24,100 m³/s; SSP5-8.5 exceeds 24,700 and 27,400 m³/s. Extreme streamflow intensity rises 49–63% (SSP2-4.5) and 73–85% (SSP5-8.5). A historical 100-year flood (~14,200 m³/s) occurs about every 4 years (SSP2-4.5) or 2.75 years (SSP5-8.5). Mean AMS rain rises ~29% and ~41%.
The limits
What it doesn't show
SWAT+ was calibrated on a short 1984–1997 window and does not fully resolve GERD operations. CMIP6 still disagrees on the sign of mean Nile rain. Extreme-value fits have wide 5th–95th percentile bands. Lake Nasser operations can still divert floods.
Key terms
- SWAT+
- A watershed hydrology model that routes rainfall through soils and channels to streamflow.
- Dongola station
- A key Nile gauge in northern Sudan used as the basin-outlet evaluation point.
- Log-Pearson Type III (LP3)
- A frequency distribution fitted to annual maximum streamflow to estimate return-period floods.
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Historical 50-year Nile peak at Dongola is about:
Common questions
Is the basin getting wetter already?
GRACE TWS rose 0.24 cm/yr (2002–2017) and 2.4 cm/yr (2018–2024), consistent with wetter recent decades.
Why pick three GCMs per SSP?
Highest, median, and lowest annual-max precipitation members span the 30-model envelope without running all 30 through SWAT+.
Does this include sea-level rise?
No: it is a river-flood hydrology study at Dongola, far upstream of the delta.
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