Impacts of climate and land use changes on the hydrological and erosion processes of two contrasting Mediterranean catchments

Abstract

27The impacts of climate and land use changes on streamflow and sediment export were evaluated 28 for a humid (São Lourenço) and a dry (Guadalupe) Mediterranean catchment, using the SWAT 29 model. SWAT was able to produce viable streamflow and sediment export simulations for both 30 catchments, which provided a baseline for investigating climate and land use changes under the 31 A1B and B1 emission scenarios for 2071-2100. Compared to the baseline scenario , 32climate change scenarios showed a decrease in annual rainfall for both catchments (humid: -12%; 33 dry: -8%), together with strong increases in rainfall during winter. Land use changes were derived 34 from a socio-economic storyline in which traditional agriculture is replaced by more profitable land 35 uses (i.e. corn and commercial forestry at the humid site; sunflower at the dry site). Climate change 36 projections showed a decrease in streamflow for both catchments, whereas sediments export 37 decreased only for the São Lourenço catchment. Land use changes resulted in an increase in 38 streamflow, but the erosive response differed between catchments. The combination of climate 39 and land use change scenarios led to a reduction in streamflow for both catchments, suggesting a 40 domain of the climatic response. As for sediments, contrasting results were observed for the humid 41 (A1B: -29%; B1: -22%) and dry catchment (A1B: +222%; B1: +5%), which is mainly due to differences 42 in the present-day and forecasted vegetation types. The results highlight the importance of climate-43 induced land-use change impacts, which could be similar to or more severe than the direct impacts 44 of climate change alone. 45 46 47

Determining the hydrological responses to climate variability and land use/cover change in the Loess Plateau with the Budyko framework

“…Various methods have been developed to isolate hydrological impacts of land use/cover change from those of climate change (Wang et al, 2013;Wang, 2014;Ahn and Merwade, 2014), which can be classified into following types: (i) paired catchment approach (Brown et al, 2005); (ii) empirically statistical methods (Wei and Zhang, 2010;Zhang et al, 2011); (iii) physically-based hydrological models (Wang et al, 2013;López-Moreno et al, 2014;Serpa et al, 2015;Buendia et al, 2016); (iv) elasticity or sensitivity based method (Schaake, 1990;Sankarasubramanian et al, 2001;Arora, 2002;Roderick and Farquhar, 2011); (v) eco-hydrological approach (Tomer and Schilling, 2009);and (vi) decomposition method (Wang and Hejazi, 2011).…”

“…These methods require long time series of data and generally lack physical meanings. The calibrated physically-based hydrological models such as SWAT (Shi et al, 2013;Serpa et al, 2015), MIKESHE (Wang et al, 2013), RHESSys (López-Moreno et al, 2014) and TETIS (Buendia et al, 2016) are run with one variable parameter while others remain fixed to detect the impacts of climate and land use changes on hydrological responses under various scenarios. Such hydrological models are useful for estimating the effects of climate change and site-specific changes in vegetation on streamflow over different time scales, but they are usually characterized by complicated model structures, large number of input data sets, time consuming and uncertainty in model calibration and validation.…”

Potential Impact of Climate Change on Suspended Sediment Yield in NW Spain: A Case Study on the Corbeira Catchment

“…Climate change projections for the Iberian Peninsula indicate a decreasing trend in annual mean rainfall and an increase in heavy rainfalls [9,10], although there are divergences depending on the model and the greenhouse gas emission scenario used. The impact of the expected climate change on river regimes in the Iberian Peninsula has been estimated by several scientists [11][12][13][14][15][16], but the impact of changes on soil erosion and sediment yield at catchment scale has received less attention.…”

“…Most of the studies have focused primarily on medium and large Mediterranean basins in which soil erosion gives rise to serious problems [11,16,17]. It might be expected that sediment yield would decrease with streamflow, although this does not always happen [18].…”

“…No study has looked at the possible impact of climate change on suspended sediment yield in Galicia (northwest Spain), an area where rainfall is potentially highly erosive and episodic events may lead to short-term issues affecting water quality, owing to high concentrations of sediment, phosphorus and metals from agricultural land carried in runoff [25][26][27][28]. Climate change might contribute to increased soil erosion in this area because of the projected higher frequency of heavy rainfall in autumn and the increase in temperature (2-3 • C) [29], which would lead to a decrease in crop growth, thereby exposing the soil and leading to enhanced soil erosion as has been reported in other areas of the Iberian Peninsula [11,16]. This underlines the need to quantify soil erosion and sediment yield in the area and to improve the knowledge on the interaction between the two processes as a basis for developing catchment management models in the region, in order to implement management practices to preserve soils, promote rational uses of the land and prevent erosion.…”