Hydrological responses in equatorial watersheds indicated by Principal Components Analysis (PCA) – study case in Atrato River Basin (Colombia)

ABSTRACT The Atrato river basin is located in the Pacific fringe of Colombia, region with one of the highest precipitation rates in the world. The main purpose of this study is to determine the dominant processes in the hydrological responses along 17 sub-basins within the basin using principal component analysis. Watersheds located at the headwater presented a fast or medium response to the precipitation events, while higher flow homogeneity was observed in watersheds located at the lower portions of the basin. Three principal components were responsible for explaining 85.18% of the total variance. The component PC1 revealed the largest contributions for low flow behavior, being associated to precipitation, characteristic discharge values, compactness index, soil coverage and soil coarse textures. The component PC2 was assigned to the geological variables, fine and average texture soil and the average basin slope. Finally, the component PC3 has shown to be related to high flow patterns (maximum characteristic discharge values Q5 and Q1), igneous rocks and length of the basin. Highest specific discharge was associated to alluvial deposits and forest cover, whereas the slope was considered determinant for the run-off generation.

Discharge Patterns of Hypoglossal Motoneurons During Fictive Breathing, Coughing, and Swallowing

We performed a series of experiments to study the intracellular activity of 58 hypoglossal motoneurons (HMs) in decerebrate, paralyzed, and ventilated cats. Changes in membrane potentials (MP) and discharge activities were evaluated during fictive breathing (FB), swallowing (FS), and coughing (FC). FS and FC were elicited by electrical stimulation of the superior laryngeal nerves. FB, FS, and FC all exhibited characteristic discharge patterns of the phrenic, abdominal, pharyngeal branch of the vagus, and hypoglossal nerves. Thirty-nine HMs displayed respiratory modulation, and 19 were nonrespiratory modulated. Nine HMs did not exhibit MP changes during FB, FS, and FC. During FS, 49 HMs exhibited MP changes consisting of depolarization, hyperpolarization or hyperpolarization-depolarization. HMs involved in FS were either respiratory modulated ( n= 38) or not ( n = 11). Only 20 HMs displayed MP changes and/or discharge activity during FC. All but two HMs fired during the expiratory phase of FC or at the end of this reflex. All HMs involved in FC ( n = 20) were also modulated during both FB and FS. Our results suggest that the XII nucleus is functionally divided into common and distinct subsets of HMs based on their spontaneous activities and responses observed during FS and FC. The changes in MP and discharge frequencies observed during the three behaviors also suggest that HMs are driven by specific premotor neurons during FS, whereas a common premotor pathway is involved during FB and FC.

Glacial-Hydrological Investigations at the Vernagtferner Glacier as a Basis for a Discharge Model

The report gives a review on the glacial-hydrological work carried out since 1974 in the project “Runoff within and from glaciers” of Sonderforschungs-bereich 81 of the Technical University Munich with the aim of creating a deterministic discharge model. Since 1974 the runoff of Vernagtferner glacier has been recorded at the gauge station “Pegelstation Vernagtbach” (catchment area 11.44 km2, mean altitude 3,125 m a.s.l., 81% glaciated). The discharge hydrographs for the years 1974-1980 are discussed and characteristic time intervals with characteristic discharge components are pointed out. Using the different discharge patterns exhibited by different parts of the glacier, a spatial classification for the discharge formation is given, and the different hydraulic conditions are described. The mathematical model which is proposed uses four parallel linear reservoirs for which the storage constants were determined by former experiments. For a fortnight period with dry and sunny weather the discharge is calculated with the energy balance on the glacier surface as input data.