Modelling the Hydro‐Sedimentary Dynamics of a Mediterranean Semiarid Ungauged Watershed Beyond the Instrumental Period

Abstract

AbstractThe development of reliable tools to quantify long‐term sediment budgets is critical to establish adequate environmental and management policies in semiarid Mediterranean regions. In this study, we apply a multidisciplinary methodology to estimate water and sediment yields in ungauged Mediterranean watersheds over a period of scarce instrumental data (i.e. second half of 19th and first half of 20th centuries). Runoff and precipitation reconstructions have been obtained using an integrative approach involving synoptic reanalysis models, regional climatic datasets, historical archives and palaeoflood proxies from natural archives. The resulting hydrological reconstruction has been implemented on a hydro‐sedimentary distributed model (i.e. TETIS) to understand the hydro‐sedimentary dynamics in the studied watershed. We highlight that, in our study area, regional‐data (instrumental, historical and sedimentary) based models show higher accuracy in the sediment yield and runoff reconstruction than synoptic reanalysis climate models. The modelled sedimentary dynamics for the studied period respond to a complex interplay between human activities and climate variability. During the 19th century deforestation and grazing activities combined with higher frequency on extreme runoff events resulted in higher runoff and sediment yield in the period 1863–1900. Over the 20th century, reduced precipitation and land abandonment led to a decrease in erosion rates and sediment yield although increased in 1945–1960 coinciding with a period of higher frequency of heavy rainfalls. This hydrological response to climate and human activities in the study watershed improves our understanding of plausible future trends of environmental degradation in small Mediterranean watersheds under different land use and climate change scenarios.This article includes supporting information which features an explanation of GILMCLIM downscaling model, The precipitation series resulting from the reanalysis data (Figure S1), an analysis of the different precipitation series used (Table S1) and an extensive explanation of how the relation between Puentes and Valdeinfierno reservoirs was considered. Copyright © 2016 John Wiley & Sons, Ltd.