[1] This paper presents an experimental analysis of the salinity distribution, the salt balance, and the variation of the saline intrusion in comparison to the freshwater discharge in the Guadalquivir estuary, which is a mesotidal system regulated and normally subjected to extremely low river flows. In such low-flow conditions, it is positive, well-mixed, and tidally dominated. The estuary is also characterized by a nonstationary, effective longitudinal dispersion coefficient, whose probability density becomes increasingly narrower and whose mean value is higher further upstream. The tidal-averaged salt flux is controlled by the following mechanisms (in order of importance): the nontidal transport, the Stokes transport, and the tidal pumping induced by the covariance between the current and salinity. These three factors account for more than 98% of the flux variation. In high river-flow conditions, the subtidal response and recovery of the estuary to changes in the river flow is analyzed. The increase in the tidal-averaged salinity during the first 2 weeks of the post-riverflood recovery in the middle and upper sections of the estuary is found to be linear in time. During that time, the celerity of the salt intrusion front was 4 cm/s. The 2 psu isohaline salt intrusion X 2 exhibits a complex dependence on the river flow Q d , including the effects of human interventions in the estuary. Three regimes are identified for the intrusion: X 2 = 57.02. 1

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The operation feasibility of small hydropower plants in mountainous sites is subjected to the run-of-river flow, which is also dependent on a high variability in precipitation and snow cover. Moreover, the management of this kind of system has to be performed with some particular operation conditions of the plant (e.g., turbine minimum and maximum discharge) but also some environmental flow requirements. In this context, a technological climate service is conceived in a tight connection with end users, perfectly answering the needs of the management of small hydropower systems in a pilot area, and providing a forecast of the river streamflow together with other operation data. This paper presents an overview of the service but also a set of lessons learnt related to the features, requirements, and considerations to bear in mind from the point of view of climate service developers. In addition, the outcomes give insight into how this kind of service could change the traditional management (normally based on past experience), providing a probability range of the future river flow based on future weather scenarios according to the range of future weather possibilities. This highlights the utility of the co-generation process to implement climate services for water and energy fields but also that seasonal climate forecasting could improve the business as usual of this kind of facility.Energies 2020, 13, 1827 2 of 15 that is subject to RoR flow, which in turn is highly variable depending on the duration of rainfall and snow cover. Since RoR plants usually have a small or non-existent storage facility that allows for very short-term water storage, the hydropower plant does not have enough water to continue operating when the inflow falls below the turbine's minimum discharge value. Another drawback of these systems is that when the inflows are extremely high and the turbine capacity is exceeded, the water will be wasted (spill) and will become a lost opportunity for generation [4].Europe is the market leader in small-scale hydropower technology, with Spain, Italy, France, Germany, and Sweden being the main producers [5]. However, the potential of RoR plants has not yet been fully explored and exploited, so there is interesting scope for the development of this technology and its optimization [5]. Management has to be done with some particular plant operating conditions but also with some environmental requirements. In this context, decision makers need to have information on the flow in the river in the short and medium term. If they could forecast the energy that will be produced in the following months, they could better adjust market prices and plan maintenance or other energy resources when the water availability falls below the minimum operating flow.Although some forecasting models already exist in the area of small-scale hydropower production [6-9], there is still a gap in linking forecasting with decision support systems. In most cases, water system managers usually make decisions based on historical statistica...

Abstract. Estuaries are complex systems in which long water quality data series are not always available at the proper scale. Data proceeding from several water quality networks, with different measuring frequencies (monthly, weekly and 15 min) and different numbers of sampling points, were compared throughout the main channel of the Guadalquivir estuary. Higher frequency of turbidity sampling in the upper estuary is required. In the lower estuary, sampling points help to find out the ETM, and higher frequency sampling of EC is required because of the effect of the tidal and river components. This could be a feedback for the implementation of monitoring networks in estuaries.