Application of eco-hydrological models to evaluate the effect of vegetation cover changes on water balance at different scales in a context of climate change

In arid and semiarid areas, water is a crucial and limited resource and its management is a challenge to assure the development of the human societies. The vegetation can have an influence on the water in quantitative terms. It determines the magnitude of interception and evapotranspiration, which results in deep drainage and runoff variations. Hydrological models allow the water balance estimation under different vegetation cover and climate scenarios, which can help improving water resources management. The main objective of this study is to assess the likely effects of vegetation cover changes on water balance in a context of climate change. To meet this objective, we used “HYDROBAL” (Eco-Hydrological model) and “DISRUN” (a distributed Eco-Hydrological model) models to simulate water balance, at different scales, in four study areas (Aguilas, Ventós, Cabeço, and Confrides) located along a climate gradient in the province of Alicante, SE Spain. HYDROBAL was used to simulate the water balance at plot and at watershed scales, while DISRUN was used to simulate a distributed balance at landscape scale. New vegetation scenarios were created at the three different scales and observed and projected climate data were used. Firstly, to assess the impact of climate change on water balance at plot scale, we analyzed the climatic conditions over two periods: the observed period 1953-2012 and the projected period 2006-2099 (under two climate change scenarios RCP4.5 and RCP8.5, from the nine Coupled Model Intercomparison Projects, Phase 5 (CMIP5)). Then, using HYDROBAL model we estimated water balance under different vegetation scenarios over the two-study period. We used R software to establish the possible combinations of vegetation cover change with an increment of 20 per cent. Then we calculated water balance at the watershed scale by extrapolation of plots results under different scenarios over the two-study period. Afterwards, using DISRUN model, we estimated the water balance and aquifer recharge at landscape scale according to different scenarios of vegetation cover changes induced by wildfire and restoration during two hydrological years (wet and dry year), and determine the best scenarios that can substitute the current vegetation cover of a small aquifer in the semiarid area (Ventós) of Southeastern Spain. The main results of this study were (i) the climate change has negative effects on water balance in the four study areas, (ii)The negative impact of climate change are supposed to continue and will be more serious, (iii) the interception rates is higher for small rainfall events (less than 20mm), (iv) At different scale, the vegetation density has an inverse relationship with all component of water balance where Pine cover has a great impact than the shrub cover, (v) Substituting Pine by Shrub will be a good intervention to mitigate the effect of climate change on Mediterranean ecosystems. In the northern study areas, a reduction of 20 per cent or 30 per cent of Pine covers will compensate the water losses expected under the climate change scenarios. However, in the southern areas, a reduction of up to 60 per cent of Pine covers is required to mitigate the effect of climate change in these environments. The results of this study can be used to predict and reduce the effect of climate change and to make plans of management and post-fire restoration that improve water balance