Abstract:Mediterranean aquifers are frequently subject to the joint effect of intensive exploitation and low recharge values. Besides, groundwater is the only available water resource in many Mediterranean regions. Groundwater recharge studies are therefore necessary to underpin water management practices. This manuscript presents a methodology to estimate groundwater recharge in a small limestone aquifer of southeastern Spain. The HYDROBAL model is used to calculate daily soil water balances on the basis of hydrological and soil data as well as on vegetation cover. Deep drainage model outputs are converted into water table variations using a lumped model add-on. The adjustment between observed and calculated water table levels is in the order of r 2 = 0.87. This correlation coefficient suggests that HYDROBAL is a useful tool to estimate groundwater recharge in the region. In addition, differences in groundwater recharge rates are observed for dry, average and wet years. Estimated recharge rates range between 0% and 18% of the mean annual rainfall, which corresponds to a net recharge of 0 to 59 mm year À1 . Recharge rates increase proportionally with precipitation (r 2 = 0.90).

Please cite this article as: Touhami, I., Chirino, E., Andreu, J.M., Sánchez, J.R., Moutahir, H., Bellot, J., Assessment of climate change impacts on soil water balance and aquifer recharge in a semiarid region in south east Spain, Hydrology (2015), doi: http://dx.doi.org/10. 1016/j.jhydrol.2015.05.012 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. Climate change forecasts in a semiarid region are of much interest to academics, managers 31 and governments. A significant decrease in annual precipitation and an increase in mean 32 annual air temperature are expected; consequently, changes in the soil water balance and 33 groundwater recharge to aquifers are expected as a response to climate change forecasts. In 34 this context, our study aimed to assess the impact of climate changes on the soil water balance 35 and natural groundwater recharge in a semiarid area (Ventós-Castellar aquifer, SE, Spain). To 36 this end, we selected Global Climate Model HadCM3 after comparing it with two other 37 models (ECHAM4 and CGCM2). The HadCM3 model climate data (air temperature and 38 precipitation in two emission scenarios: A2-high and B2-low; 2011-2099) were coupled to a 39 HYDROBAL hydrological model to determine the soil water balance. The HYDROBAL 40 model results showed that climate change will have a significant impact on the soil water 41 balance in the study area, especially on groundwater recharge during the latter period. In both 42 the A2-high and B2-low scenarios, the selected years to run the HYDROBAL model showed 43 a decrease in water balance components (Precipitation, actual evapotranspiration, aquifer 44 recharge and runoff) in relation to the baseline period . Over the projected period 45 (2011-2099), we expect fewer rainfall events (>15 mm), which promote aquifer recharge, 46 longer dry summer seasons and, consequently, reduced average annual recharge that ranged 47 from 3-17%; 10-49 mm, if compared to the baseline period. The methodology developed in 48 the present study can be beneficial for assessing the impact of predicted climate change on 49 groundwater recharge, and can help managers and planners to devise strategies for the 50 efficient use and conservation of freshwater resources. 51 52 Journal of

Groundwater resources are typically the main fresh water source in arid and semi-arid regions. Natural recharge of aquifers is mainly based on precipitation; however, only heavy precipitation events (HPEs) are expected to produce appreciable aquifer recharge in these environments. In this work, we used daily precipitation and monthly water level time series from different locations over a Mediterranean region of Southeastern Spain to identify the critical threshold value to define HPEs that lead to appreciable aquifer recharge in this region. Wavelet and trend analyses were used to study the changes in the temporal distribution of the chosen HPEs (=20¿mm¿day-1) over the observed period 1953–2012 and its projected evolution by using 18 downscaled climate projections over the projected period 2040–2099. The used precipitation time series were grouped in 10 clusters according to similarities between them assessed by using Pearson correlations. Results showed that the critical HPE threshold for the study area is 20¿mm¿day-1. Wavelet analysis showed that observed significant seasonal and annual peaks in global wavelet spectrum in the first sub-period (1953–1982) are no longer significant in the second sub-period (1983–2012) in the major part of the ten clusters. This change is because of the reduction of the mean HPEs number, which showed a negative trend over the observed period in nine clusters and was significant in five of them. However, the mean size of HPEs showed a positive trend in six clusters. A similar tendency of change is expected over the projected period. The expected reduction of the mean HPEs number is two times higher under the high climate scenario (RCP8.5) than under the moderate scenario (RCP4.5). The mean size of these events is expected to increase under the two scenarios. The groundwater availability will be affected by the reduction of HPE number which will increase the length of no aquifer recharge periods (NARP) accentuating the groundwater drought in the region. Copyright © 2016 John Wiley & Sons, Ltd.Peer ReviewedPostprint (published version

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Estimating groundwater recharge is essential to ensure the sustainable use of groundwater resources, particularly in arid and semi-arid regions. Soil water balances have been frequently advocated as valuable tools to estimate groundwater recharge. This article compares the performance of three soil water balance models (Hydrobal, Visual Balan v2.0 and Thornthwaite) in the Ventós-Castellar aquifer, Spain. The models were used to simulate wet and dry years. Recharge estimates were transformed into water table fluctuations by means of a lumped groundwater model. These, in turn, were calibrated against piezometric data. Overall, the Hydrobal model shows the best fit between observed and calculated levels (r 2 = 0.84), highlighting the role of soil moisture and vegetation in recharge processes.Key words groundwater recharge; soil water balance; lumped groundwater model; karst aquifers; semi-arid region; Alicante, Spain Performances comparées de modèles de bilan hydrique des sols pour le calcul de la recharge d'aquifères en conditions semi-arides Résumé L'estimation de la recharge des eaux souterraines est essentielle pour permettre l'utilisation durable des ressources en eaux souterraines, en particulier dans les régions arides et semi-arides. Les bilans hydriques des sols ont souvent été recommandés comme de précieux outils pour estimer la recharge des eaux souterraines. Cet article compare les performances des trois modèles de bilan hydrique du sol (Hydrobal, Visual Balan v2.0 et Thornthwaite) sur l'aquifère de Ventós-Castellar, en Espagne. Nous avons appliqué les modèles de simulation sur des années humides et sèches. Les estimations de la recharge ont été transformées en fluctuations du niveau de la nappe au moyen d'un modèle global d'eau souterraine. Ces fluctuations ont été calées à leur tour par rapport aux données piézométriques. Globalement, le modèle Hydrobal donne le meilleur ajustement entre les niveaux observés et calculés (r 2 = 0,84), mettant en évidence le rôle de l'humidité des sols et de la végétation dans les processus de recharge.Mots clefs recharge des eaux souterraines ; bilan hydrique du sol ; modèle global d'eau souterraine ; aquifères karstiques ; région semi-aride ; Alicante ; Espagne

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Forests provide many environmental services, especially those related to the water cycle. In semiarid areas where water is a limiting factor for ecosystem functioning, forested areas can have a strong impact on ground water recharge. In these areas, proper knowledge of forests' water balance is necessary to promote management practices that may ensure ecosystem properties and environmental services like water or carbon fixation. In this article, we review several ecohydrology topics within the framework of Mediterranean water-limited environments in two representative ecosystems: Kermes oak (Quercus ilex L.) and Aleppo pine (Pinus halepensis Mill.) forests. Both are the commonest species in countries that surround the Western Mediterranean Basin. We analysed the Blue and Green water components, i.e., green water is the water demand of forests, represented by evapotranspiration and interception; while blue water is the part of the balance involving runoff and deep percolation, which can be regarded as water directly usable by society. In general, different studies conducted in Mediterranean areas have pointed out that the water balances of Q. ilex and P. halepensis forests have low values for the Blue to Green water (B/G) ratios. Adaptive forest management like forest thinning can compensate for these ratios. Thinning has demonstrated to reduce losses by interception, but at same time, it can also increase individual tree transpiration and evaporation rates. However, these practices lead to higher B/G ratios when considering the whole stand. In future global change scenarios, in which drought conditions are expected to intensify, management practices can improve the water balance in these ecosystems by minimizing the risk of plant mortality and species replacement due to intense competence by water resources.

Land Surface Phenology (LSP) metrics are increasingly being used as indicators of climate change impacts in ecosystems. For this purpose, it is necessary to use methods that can be applied to large areas with different types of vegetation, including vulnerable semiarid ecosystems that exhibit high spatial variability and low signal-to-noise ratio in seasonality. In this work, we evaluated the use of hidden Markov models (HMM) to extract phenological parameters from Moderate Resolution Imaging Spectroradiometer (MODIS) derived Normalized Difference Vegetation Index (NDVI). We analyzed NDVI time-series data for the period 2000–2018 across a range of land cover types in Southeast Spain, including rice croplands, shrublands, mixed pine forests, and semiarid steppes. Start of Season (SOS) and End of Season (EOS) metrics derived from HMM were compared with those obtained using well-established smoothing methods. When a clear and consistent seasonal variation was present, as was the case in the rice croplands, and when adjusting average curves, the smoothing methods performed as well as expected, with HMM providing consistent results. When spatial variability was high and seasonality was less clearly defined, as in the semiarid shrublands and steppe, the performance of the smoothing methods degraded. In these cases, the results from HMM were also less consistent, yet they were able to provide pixel-wise estimations of the metrics even when comparison methods did not.