Search

Renewable energy sources are essential to reduce the negative impacts on the environment caused by burning fossil fuels. Using solar photovoltaic installations in recent years means that decision-makers must consider infrastructure renewal decisions. An expenditure framework to achieve the optimal renovation period of photovoltaic modules is proposed here from an economic standpoint. This approach includes not only the investment and maintenance costs but also energy and emissions savings. A sensitivity analysis was carried out using a case study in south-eastern Spain, achieving that the optimal renovation period ranges between 17.0 and 24.7 years. Many factors are studied to identify those with the greatest influence on this indicator. Installing a solar power system is always a profitable choice considering that the installation lifetime is 25 years. Neglecting the influence of these limits may cause potential savings not fully exploited., CRUE-CSIC, Springer Nature, research project "DESENREDA" through the 2021 call "Estancias de movilidad en el extranjero Jose Castillejo" of the Ministerio de Universidades CAS21/00085, project "Hi-Edu Carbon" Erasmus Plus Programme, Key Action KA22021, action type 2021-1-SK01-KA220-HED-000023274

Ain Sefra is part of the Ksour Mountains and it's situated in southwestern Algeria, where the climate is arid. The study area is progressively facing regression and degradation exacerbated by climate change. These trends point to a significant acceleration of desertification and drought and the loss of production systems that play a critical social, ecological, and economic role in the region. To better understand the natural hazard of dryness in Ain Sefra and the impact of climate change, we used various drought indices and remote sensing data. Hence, analyzing precipitation records from 1965 to 2021, through several drought indices, droughts were identified as a recurring phenomenon. Moreover, the frequency of successive dry years is relatively high. There were three most extended continuous dry periods. The first phase lasted seven years from 1980 to 1987, the second twelve years from 1994 to 2006, and the third nine years from 2012 to 2021. Calculation of the Modified Soil-Adjusted Vegetation Index (MSAVI) for five multidate satellite images allowed us to follow the evolution of land use elements in this region from 1977 to 2017. Indeed, the study of these multi-temporal images reveals a considerable growth of sands, moving towards the north and northeast of the zone during the last decades. The combination of drought indices and remote sensing seems to be most promising; whose results are valuable tools for guidance and decision support to local and regional authorities. Ain Sefr, en las montañas Ksour, está situada en el suroeste de Argelia, donde el clima es árido. El área de estudio se enfrenta progresivamente a la regresión y degradación exacerbada por el cambio climático. Estas tendencias apuntan a una aceleración significativa de la desertificación y la sequía y a la pérdida de sistemas de producción que desempeñan un papel social, ecológico y económico crítico en la región. Para comprender mejor el peligro natural de la sequía en Ain Sefra y el impacto del cambio climático, se varios índices de sequía y datos de teledetección. Al analizar los registros de precipitación desde 1965 hasta 2021, a través de varios índices de sequía, se identificaron las sequías como un fenómeno recurrente. Además, la frecuencia de años secos sucesivos es relativamente alta. Hubo tres períodos secos continuos más prolongados. La primera fase duró siete años, de 1980 a 1987, la segunda doce años, de 1994 a 2006, y la tercera nueve años, de 2012 a 2021. El cálculo del Índice de Vegetación Ajustado al Suelo Modificado (MSAVI) para cinco imágenes satelitales multifecha nos permitió seguir la evolución de los elementos de uso del suelo en esta región desde 1977 hasta 2017. De hecho, el estudio de estas imágenes multitemporales revela un crecimiento considerable de arenas, moviéndose hacia el norte y noreste de la zona durante las últimas décadas. La combinación de índices de sequía y sensores remotos parece ser muy prometedores, pues sus resultados son valiosas herramientas de orientación y apoyo a la decisión de los entes locales y regionales. Financial support to perform this study was provided partially by the University Center Salhi Ahmed Naama (Argelia). Antonio Jodar-Abellan acknowledges financial support received form the XTREME Spanish National Project (Ref: PID2019-109381RB-I00/AEI/10.13039/501100011033).

The phenomenon of aeolian sand deposit constitutes a major problem in the region of Ksour Mountains in Algeria, which causes serious social and economic problems. To assess the textural properties of sands, and to investigate the origin of aeolian sand deposit in the study area, eleven (11) samples were collected from the sands of Ain Sefra. Then the granulometry, calcimetry and morphoscopy of the samples were studied. Granulometric testing of samples from 11 locations showed that sand size was very fine to fine grained, with a mean grain value of 226.5 μm. It sort ranged from 1.22 to 1.90, indicating well sorting the sands and skewness values ranging from-0.4 to 0.66, being mainly negative with an average of -0.06, indicating symmetrical to fine skewed values. The values of kurtosis ranges from 0.79 to 1.5, with an average of 0.93, where 64 percent of samples are Mesokurtotic and 36 percent of samples are Platikurtotic. Calcimetric results show a very low percentage of carbonate, which ranges from 1.85 % to 7.4 % and illustrate a very low content of fine fraction and organic matter. The preliminary examinations of the sands in our study area by morphoscopy showed that 73 percent of sand are in RM category, 19 percent in the rounded and shiny (EL) category. In comparison, 08 percent are represented by the fresh and angular (NU) category. The outcome of various experimentation led to the conclusion that the aeolian sand deposit in the study area, are linked to the wind transport from the Moroccan territory such as Chott Tigri, Oued Maader, the corridor between Figuig, Bouarfa and Massa Daraa, which are the dominant sources of sands in the region of the study area. Therefore, the study better understands the origin of sands and their characteristics in this part of the Ksour Mountains.

This research was funded partially by the Central University of Ecuador and by the projects RESERVOIR (PRIMA programme supported by the European Union under grant agreement no. 1924) and BBVA2021-Leonardo2 along with local companies (projects Comunidad Regantes 220-I and Comunidad Regantes 1-20T). Antonio Jodar-Abellan acknowledges financial support received from the project BBVA2021-Leonardo2. In the same way, this work has been conducted within the Catedra del Agua of the University of Alicante (catedradelaguaua.org). Moreover, authors acknowledge the reviewers of the manuscript whose comments contributed greatly to improve this paper., Non-planned agricultural land abandonment is affecting natural hydrological processes. This is especially relevant in vulnerable arid karstic watersheds, where water resources are scarce but vital for sustaining natural ecosystems and human settlements.However, studies assessing the spatiotemporal evolution of the hydrological responses considering land-use changes and precipitation cycles for long periods are rare in karstic environments. In this research, we selected a representative karstic watershed in a Mediterranean semiarid domain, since in this belt, karst environments are prone to land degradation processes due to human impacts. Geographic Information Systems-based tools and hydrological modeling considering daily time steps were combined with temporal analysis of climate variables (wavelet analysis) to demonstrate possible interactions and vulnerable responses. Observed daily flow data were used to calibrate/ validate these hydrological models by applying statistic indicators such as the NSE efficiency and a selfdeveloped index (the ANSE index). This new index could enhance goodness-of-fit measurements obtained with traditional statistics during the model optimization. We hypothesize that this is key to adding new inputs to this research line. Our results revealed that: i) changes in the type of sclerophyllous vegetation (Quercus calliprinos, ilex, rotundifolia, suber, etc.) from 81.5% during the initial stage (1990) to natural grasslands by 81.6% (2018); and, ii) decreases in agricultural areas (crops) by approximately 60% and their transformation into coniferous forests, rock outcrops, sparsely natural grasslands, etc. in the same period. Consequently, increases in the curve number (CN) rateswere identified as a result of land abandonment. As a result, an increase in peak flow events jointlywith a relevant decrease of the average flow rates (water scarcity) in the watershed was predicted by the HEC-HMS model and verified through the observed data. This research provides useful information about the effects of anthropogenic changes in the hydrodynamic behaviour of karstic watersheds andwater resource impacts, especially key in water-scarce areas that depict important hazards for the water supply of related populations and natural ecosystems., Central University of Ecuador, European Commission 1924, Comunidad de Madrid 220-I, Catedra del Agua of the University of Alicante