[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.

Run of river (RoR) hydropower systems, despite being one of the most cost-effective and environmentally benign energy technologies, have the disadvantage that production is not constant because it is subject to a high variability in precipitation and snow cover. In addition, the management of RoR plants has to comply with some particular operating conditions, but also with some environmental flow requirements. This work presents the assessment of the main inputs included in a climate service, historical local data and the seasonal forecast of water inflow to RoR plants, which are used to predict the operability and the expected energy production. The analysis is presented through the application in a pilot RoR system located in the south of Spain, in a semi-arid Mediterranean area impacted by snow, where seasonal forecasting is especially challenging. The results show the high interannual variability of the operation in this kind of facilities. The outcomes indicate that seasonal climate forecast information would improve the prediction of observed river streamflow by 7.4% in reliability and 3.2% in sharpness compared to the current operational forecast based on historical data. The climate forecasts thus provide valuable information for the exploitation of available water resources, which generates a significant value for the operation of the plant and the energy production market.

Abstract. Risk assessment for water resource planning must deal with the uncertainty associated with excess/scarcity situations and their costs. The projected actions for increasing water security usually involve an indirect "call-effect": the territory occupation/water use is increased following the achieved protection. In this work, flood and water demand in a mountainous semi-arid watershed in southern Spain are assessed by means of the stochastic simulation of extremes, when this human factor is/is not considered. The results show how not including this call-effect induced an underestimation of flood risk after protecting the floodplain of between 35 and 78 % in a 35-year planning horizon. Similarly, the pursued water availability of a new reservoir resulted in a 10-year scarcity risk increase up to 38 % when the trend of expanding the irrigated area was included in the simulations. These results highlight the need for including this interaction in the decision-making assessment.

Abstract. Regulation by reservoirs affects both the freshwater regime and the sediment delivery at the area downstream, and may have a significant impact on water quality in the final transitional water bodies. Spain is one the countries with more water storage capacity by reservoirs in the world. Dense reservoir networks can be found in most of the hydrographic basins, especially in the central and southern regions. The spatial redistribution of the seasonal and annual water storage in reservoirs for irrigation and urban supply, mainly, has resulted in significant changes of water flow and sediment load regimes, together with a fostered development of soil and water uses, with environmental impacts downstream and higher vulnerability of these areas to the sea level rise and drought occurrence. This work shows these effects in the Guadalquivir and the Ebro River basins, two of the largest regulated areas in Spain. The results show a 71 % decrease of the annual freshwater input to the Guadalquivir River estuary during 1930-2014, an increase of 420 % of the irrigated area upstream the estuary, and suspended sediment loads up to 1000 % the initial levels. In the Ebro River delta, the annual water yield has decreased over a 30 % but, on the contrary, the big reservoirs are located in the main stream, and the sediment load has decreased a 99 %, resulting in a delta coastal regression up to 10 m per year and the massive presence of macrophytes in the lower river. Adaptive actions proposed to face these impacts in a sea level rise scenario are also analyzed.

Abstract. Spain is one of the world's countries with a large number of reservoirs per inhabitant. This intense regulation of the fluvial network during the 20th century has resulted in a decrease in flood events, a higher availability of water resources, and a high development of the irrigated crop area, even in the drier regions. For decades, flood perception was reduced since the development of reservoirs protected the floodplains of river; this resulted in later occupation of soil by urban, agricultural and industrial uses. In recent years, an increasing perception of flood events is observed, associated to the higher damage associated to extreme events in the now occupied areas, especially in coastal watersheds. This work shows the change on flood risk in the coastal areas of three hydrographic basins in Andalusia (South Spain) during the reservoir expansion period: the Guadalete, Guadalquivir and Guadalhorce river basins. The results differentiate the impact of the regulation level on both the cumulative distribution functions of the fluvial discharge near the river mouth, for different time scales, and the associated damage related to the enhanced soil occupation during this period. The different impact on the final medium and long term flood risk is also assessed in terms of the storage capacity per unit area throughout the basins, the effective annual runoff/precipitation index, the frequency of sea storms, and the human factor (change in social perception of floods), for different intervals in the flood extreme regime. The implications for adaptation actions is also assessed.