Nutrient dynamics in Mediterranean temporary streams: A case study in Pardiela catchment (Degebe River, Portugal)

Most of the streams in the Mediterranean region are temporary, following predictable seasonal of flooding and drying, with a transition from lotic conditions to shallow lentic conditions. The goal of our study was to assess the nitrogen and phosphorus dynamics in channel-bed processes of temporary streams between floods. Results show that, during winter, temperatures ranged between 9.5 and 11.2 °C and oxygen concentration ranged from 8.0 to 9.5 mg L⁻¹, whereas, during summer, temperatures varied between 21.2 and 26.8 °C and oxygen between 1.2 and 5.3 mg L⁻¹, with oxygen depletion in the pools during the night. The nitrate concentrations were far more abundant during winter (February), while ammonium concentration increased after stream fragmentation into pools (especially in July when oxygen depletion conditions favoured ammonification). Results on sediment profiles showed that the most active sediment layers for NH₄-N are the top 2–3 cm, corresponding to the sediment depositional sites of the stream. Phosphate concentrations had larger variability, yet concentrations decreased from winter to spring and increased again in summer, when the shallow water pools were formed. Sediment profiles at the sediment depositional sites showed that PO₄-P was more dynamic in the first 6 cm.

In Mediterranean temporary streams, nutrient dynamics vary seasonally, as the system transits from lotic conditions to shallow lentic conditions, evidencing the regeneration of nutrients from organic and inorganic matter during the flow cessation period.     

Lateral heterogeneities in the upper and mid-mantle conductivity in Argentina

Regional studies of Sq variations measured at five permanent observatories in Argentina were performed to estimate the distribution of the electrical conductivity of the upper and mid-mantle, reaching a depth of approximately 800 km. After separating the total field into its parts of external and internal origin, the in duced field was modeled, applying two-dimensional techniques. Additionally, induction arrows and an equivalent apparent resistivity curve were calculated A north-south heterogeneity was detected, showing an increase of the conductivity of the shallower layers north of the profile, which may be related to the presence of high volcanic activity in the area.Also at CONICET (Consejo Nacional de Investigaciones Científicas y Técnicas).     

Water reservoirs and the risk of accidental flood occurrence. Case study: Stanca–Costesti reservoir and the historical floods of the Prut river in the period July–August 2008, Romania

In the summer of 2008 the Prut river recorded a historical flow of 7140 m³/s at its entrance into Romania. This flow was the highest ever recorded of any Romanian river. The high value was generated by high amounts of rainfall recorded first on the territory of Ukraine and then in Romania. Unfortunately, there were some discrepancies between the data transmitted and intercepted from the Meteorology National Agency and Hydrology and Water Management National Agency. This is why the amount of precipitation which fell over the territory of Ukraine could not be monitored in time and punctually. Nor could the high flood wave moving rapidly from the upper basin to the lower basin. The high flow of the upper Prut caused the accumulation of an immense quantity of water in the Stanca–Costesti reservoir. Under the conditions of precipitation occurring in the lower river basin as well, the levels reached the flood quota and the reservoir reached the maximum accepted capacity, with 0·1% insurance. The release of supplementary water quantities from the reservoir would have produced catastrophic floods downstream. Keeping the water in the reservoir could have broken it and the flooding, through backwater eddies, or the riverbank settlements. In such a case, it would have produced the greatest tragedy in the hydrological history of Europe. The most significant damage was produced upstream of the barrage, next to the localities of Radauti Prut and Baranca–Hudesti, as well as in the area of the reservoir, as a result of the phenomenon known as ‘remuu’, or backwater eddies. The floods of the Prut river occurred between the end of July and the end of August. Copyright © 2011 John Wiley & Sons, Ltd.     

Stepwise selection of functional covariates in forecasting peak levels of olive pollen

High levels of airborne olive pollen represent a problem for a large proportion of the population because of the many allergies it causes. Many attempts have been made to forecast the concentration of airborne olive pollen, using methods such as time series, linear regression, neural networks, a combination of fuzzy systems and neural networks, and functional models. This paper presents a functional logistic regression model used to study the relationship between olive pollen concentration and different climatic factors, and on this basis to predict the probability of high (and possibly extreme) levels of airborne pollen, selecting the best subset of functional climatic variables by means of a stepwise method based on the conditional likelihood ratio test.     

The shape of the seismic response interaction diagram: The effect of combination rules in response spectrum analysis

This paper deals with the construction of seismic response interaction diagrams that show the correlation of multiple responses and are important to determine the critical combination of modal responses. Many design problems, such as column design under combined axial force and bending moments, fall into this category. We address general modal and multicomponent combination rules and study their effect on the shape of the response interaction diagrams, thus extending previous work done for quadratic combination rules. Special attention is given to multilinear combination rules which lead to polyhedral shapes. Having developed efficient methods to deal with polyhedral shapes, we explore the idea of adopting a multilinear modal combination rule to compose with a multicomponent percentage rule.     

A concerted research effort to advance the hydrological understanding of tropical páramos

Páramos, a neotropical alpine grassland-peatland biome of the northern Andes and Central America, play an essential role in regional and global cycles of water, carbon, and nutrients. They act as water towers, delivering water and ecosystem services from the high mountains down to the Pacific, Caribbean, and Amazon regions. Páramos are also widely recognized as a biodiversity and climate change hot spots, yet they are threatened by anthropogenic activities and environmental changes. Despite their importance for water security and carbon storage, and their vulnerability to human activities, only three decades ago, páramos were severely understudied. Increasing awareness of the need for hydrological evidence to guide sustainable management of páramos prompted action for generating data and for filling long-standing knowledge gaps. This has led to a remarkably successful increase in scientific knowledge, induced by a strong interaction between the scientific, policy, and (local) management communities. A combination of well-established and innovative approaches has been applied to data collection, processing, and analysis. In this review, we provide a short overview of the historical development of research and state of knowledge of the hydrometeorology, flux dynamics, anthropogenic impacts, and the influence of extreme events in páramos. We then present emerging technologies for hydrology and water resources research and management applied to páramos. We discuss how converging science and policy efforts have leveraged traditional and new observational techniques to generate an evidence base that can support the sustainable management of páramos. We conclude that this co-evolution of science and policy was able to successfully cover different spatial and temporal scales. Lastly, we outline future research directions to showcase how sustainable long-term data collection can foster the responsible conservation of páramos water towers.