Long-term streamflow reconstruction of The Medjerda River, Tunisia, from tree rings

Le résumé fourni par la source

Short instrumental discharge data limit our understanding of long-term hydrological variability in North African river basins. The Medjerda River, Tunisia's most important watercourse, has discharge data dating back only to the 1950s, making effective water resource management challenging in an area already stressed by climate unpredictability and severe droughts. We present a tree-ring-based reconstruction of Medjerda River discharge, 1876–2009, from a set of 7 Pinus halepensis tree-ring chronologies. An observed natural flow discharge series, to calibrate the reconstruction model, is generated from precipitation and temperature data with the aid of a web-based dendrohydrology platform. The reconstruction, calibrated over 1934–2009, explains 54 % of discharge variability and captures key hydroclimatic trends over yearly and decadal timescales. Single-year record highs and lows in reconstructed discharge occurred in the 2000s, but the largest departures in the smoothed (5-year) data occurred in the 1880s and 1940s. The reconstruction highlights the importance of considering longer time horizons for planning water resources in the Medjerda Basin, as well as the value of tree-ring data in conjunction with a water balance model for hydrologic reconstruction in basins with short or highly distorted gauged flow records. For the Medjerda Basin, results highlight the need for expanded tree-ring collections to achieve a longer reconstruction horizon. Improvement in the reconstruction signal for wet years is another pressing need. • Initial reconstruction of the Medjerda River discharge in Tunisia based on tree rings. • Extends hydrological records to 1876 CE by utilizing 7 screened site chronologies. • Reconstruction accounts for 54 % of the discharge variance in the calibration period • Multi-year periods of low discharge and high discharge are identified. • Long-term view facilitates sustainable water management in semi-arid basins.

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