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Water scarcity will increase in the world in the coming decades due to climate change, especially in areas that currently already have water scarcity, such as the Mediterranean area. In these areas, to guarantee water resources, systems' sustainability is necessary to improve demand management and the development of non-conventional resources, such as treated wastewater reuse or seawater desalination. These non-conventional resources are highly energy-consuming; so, reducing energy costs is a key element in developing their use in different sectors, including agriculture. Combining photovoltaic solar energy with seawater desalination by reverse osmosis will reduce the cost of producing water to below 0.36 EUR/m3; so, this resource can be attractive for agriculture, as demonstrated in this work. The arrangement of bifacial solar modules in horizontal single-axis tracking systems increases the energy amount generated from the sun in one hour or more, improving the facility's efficiency and reducing the desalinated water cost. The greater distance between the solar module lines, with a ground coverage ratio (GCR) = 0.3, makes for a better environmental integration of the facility and allows the development of agrovoltaic strategies, such as native flora planting and pollinator colonization. [ABSTRACT FROM AUTHOR]

Aquifers are ubiquitous, and their water is easy to obtain with low extraction costs. On many occasions, these characteristics lead to overexploitation due to important water level declines, reduction of river base flows, enhanced seawater intrusion, and wetland affection. The forecasted increase in water demands and global warming will impact the future availability of water resources. Conjunctive use of surface and subsurface waters can help in mitigating these impacts. There are two main conjunctive use strategies: artificial recharge (AR) and alternate conjunctive use (ACU). AR stores waters that are not to be used directly in aquifers. ACU utilizes groundwater in dry periods, while surface waters are preferred in wet ones; this allows the increase of water supply with lower dam storage, economic gains, and environmental advantages. Efficient conjunctive use can prevent soil salinization and waterlogging problems in semiarid countries due to excessive recharge from irrigation return flows or other origins. Groundwater is a neglected and generally misused resource to maintain environmental conditions. When considering the solution to a water resources problem, groundwater should always be part of the design as an alternative or a complementary resource. Aquifers have large inertia, and changes in their volumes are only noticeable after years of observations. Unfortunately, groundwater observation networks are much poorer than surface ones, something that should be changed if groundwater is to come to the rescue in these times of climate change. Human and material resources should be made available to monitor, control, analyze, and forecast groundwater. [ABSTRACT FROM AUTHOR]

The biomonitoring methods implemented by water authorities are mostly developed for perennial rivers, and do not apply to temporary rivers (TRs). We propose a new classification for TRs to better assess their ecological status. It arises from the LIFE+ TRivers project, which was conducted in the Catalan and the Júcar Mediterranean river basin districts (RBD). The European Water Framework Directive (WFD) provided two systems to set river types (systems A or B from Annex II), which have been officially used by water authorities across Europe to set "national river types" (NRTs). However, essential hydrological variables for TRs are largely omitted. NRTs established according to the WFD were compared with TR categories obtained by using a rainfall-runoff model, "natural flows prescribed regimes" (NFPRs), and with "aquatic phases regimes" (APRs) calculated by using TREHS software. The biological quality indices currently used in Spain, based on macroinvertebrates and diatoms (IBMWP, IMMI-T, and IPS), were compared with a "general degradation" gradient in order to analyze the two TR river classification procedures (NFPR and APR). The results showed that NRTs did not properly classify TRs, and that the APR classification identified ecologically meaningful categories, especially those related to stagnant phases. Four "management temporary river categories" based on APRs are proposed to be used for water managers to properly assess the ecological status of TRs. [ABSTRACT FROM AUTHOR]