Tree-Ring Evidence of Increasing Drought Risks over the Past Five
Centuries amidst Projected Flood Intensification in the Kabul River
Basin (Afghanistan and Pakistan)
Abstract
Increased flood risks have been projected in the Kabul River Basin, but
with large uncertainties. To place future changes in a long-term
perspective, we produce a 501-year precipitation reconstruction for the
basin using seven tree-ring chronologies of Cedrus deodara,
Picea smithiana, and Pinus gerardiana from the Hindukush
Mountains, a monsoon-shadow area. The reconstruction proves robust over
rigorous cross-validations (R2 = 0.62, RE = 0.61, CE =
0.53). The full reconstruction (1517–2018) shows heterogeneous changes
in the precipitation distribution: there is a weak increasing trend in
the median annual precipitation, no apparent trend in the 50-year
maximum precipitation, and, importantly, a steadily decreasing trend in
50-year minimum precipitation. In other words, our reconstruction shows
that drought risks have been increasing over the past five centuries.
Drought risks, compounded with projected flood intensification, pose
significant threats for the transboundary river. Future water management
decisions should factor in past long-term climate variability.