Modeling suspended sediment transport and assessing the impacts of climate change in a karstic Mediterranean watershed

S D Nerantzaki; G V Giannakis; D Efstathiou; N P Nikolaidis; I Α Sibetheros; G P Karatzas; I Zacharias

doi:10.1016/j.scitotenv.2015.07.092

Modeling suspended sediment transport and assessing the impacts of climate change in a karstic Mediterranean watershed

Sci Total Environ. 2015 Dec 15:538:288-97. doi: 10.1016/j.scitotenv.2015.07.092. Epub 2015 Aug 24.

Authors

S D Nerantzaki¹, G V Giannakis¹, D Efstathiou¹, N P Nikolaidis¹, I Α Sibetheros², G P Karatzas¹, I Zacharias³

Affiliations

¹ Technical University of Crete, Department of Environmental Engineering, University Campus, 73100 Chania, Greece.
² TEI - Athens, Department of Civil Infrastructure Engineering, Agiou Spyridonos, 12210 Aigaleo, Greece.
³ University of Patras, Department of Environmental and Natural Resources Management, 26504 Rio Patras, Greece.

PMID: 26311584
DOI: 10.1016/j.scitotenv.2015.07.092

Abstract

Mediterranean semi-arid watersheds are characterized by a climate type with long periods of drought and infrequent but high-intensity rainfalls. These factors lead to the formation of temporary flow tributaries which present flashy hydrographs with response times ranging from minutes to hours and high erosion rates with significant sediment transport. Modeling of suspended sediment concentration in such watersheds is of utmost importance due to flash flood phenomena, during which, large quantities of sediments and pollutants are carried downstream. The aim of this study is to develop a modeling framework for suspended sediment transport in a karstic watershed and assess the impact of climate change on flow, soil erosion and sediment transport in a hydrologically complex and intensively managed Mediterranean watershed. The Soil and Water Assessment Tool (SWAT) model was coupled with a karstic flow and suspended sediment model in order to simulate the hydrology and sediment yield of the karstic springs and the whole watershed. Both daily flow data (2005-2014) and monthly sediment concentration data (2011-2014) were used for model calibration. The results showed good agreement between observed and modeled values for both flow and sediment concentration. Flash flood events account for 63-70% of the annual sediment export depending on a wet or dry year. Simulation results for a set of IPCC "A1B" climate change scenarios suggested that major decreases in surface flow (69.6%) and in the flow of the springs (76.5%) take place between the 2010-2049 and 2050-2090 time periods. An assessment of the future ecological flows revealed that the frequency of minimum flow events increases over the years. The trend of surface sediment export during these periods is also decreasing (54.5%) but the difference is not statistically significant due to the variability of the sediment. On the other hand, sediment originating from the springs is not affected significantly by climate change.

Keywords: Climate change; Karstic springs; Mediterranean watershed; SWAT model; Suspended sediment modeling.

Publication types

Research Support, Non-U.S. Gov't

MeSH terms

Climate Change*
Environmental Monitoring / methods*
Geologic Sediments / analysis*
Hydrology
Mediterranean Region
Models, Theoretical*
Rivers / chemistry*
Water Pollutants / analysis*
Water Supply / statistics & numerical data

Substances

Water Pollutants