The purpose of this paper is to document the climate characteristics of the Global Forecast System (GFS), which is an atmospheric general circulation model developed at the Central Weather Bureau ...(CWB), Taiwan. This paper documents the winter (December-February) and summer (June-August) climate characteristics of simulated hydrological processes and atmospheric circulation from a 2-year control simulation conducted with the GFS using an annually repeating prescribed sea surface temperature climatology.
A expansão da área florestal produz alterações ao nível dos ecossistemas em geral e à sustentabilidade dos recursos naturais em particular. Neste trabalho apresentam-se resultados sobre a implicação ...das florestas de Eucalipto e de Pinheiro sobre os recursos hídricos, nomeadamente sobre os processos hídricos e hidroquímicos. São ainda apresentadas taxas de erosão para vários usos florestais do solo. Uma particular atenção será dada às consequências de dois dos acontecimentos recorrentes mais catastróficos na floresta portuguesa: os fogos florestais e as lavragens no sentido do maior declive da vertente.
Diese Arbeit soll die Zusammenhänge von hydrologischen Rahmenbedingungen und Massenbewegungen besser erforschen, damit in Zukunft verbesserte Vorhersagen des Versagenszeitpunktes möglich werden. Das ...Untersuchungsgebiet besteht aus einem ca. 2 km langen und 500 m breiten Hang mit einem maximalen Höhenunterschied von ca. 400 m. Das dort vorkommende Festgestein besteht im Wesentlichen aus Mergelstein. Die vergangenen Eiszeiten haben dieses Gestein überarbeitet und Grundmoränenablagerungen auf dem Hang zurückgelassen. Diese wurden in den letzen 10.000 Jahren von Hangschutt, der aus den benachbarten Steilhängen stammt, überlagert. Der Hangschutt ist sehr verwitterungsanfällig, die Kalkkristalle lösen sich und wandeln den Hangschutt in lehmiges Material. Bewegungsmessungen an der Oberfläche zeigen, dass sich der Hang mit ca. 10 cm im Jahr talabwärts bewegt. Diese Bewegungen werden sehr wahrscheinlich durch kleine ruckartige Ereignisse in ca. 8 m Tiefe ausgelöst. Ziel der Untersuchungen war, den Wasserhaushalt des Hanges so gut wie möglich zu erfassen und mit Computermodellen abzubilden. Dabei spielt die Heterogenität der pedologischen Eigenschaften einen wesentliche Rolle, als Eingangsparameter für die Modelle.Grundwasserstandsmessungen in 5,5 m Tiefe auf dem Hang zeigen schnelle Reaktionen des Grundwasserspiegels nach Niederschlagsereignissen. Das Wasser dieser Ereignisse kann aber aufgrund des Lehms, der nur eine geringe Wasserdurchlässigkeit für Wasser besitzt, nicht in den tieferen Untergrund gelangen, sondern fließt fast vollständig an der Oberfläche ab. Dahingegen führt ein schnelles Versickern von Wasser in an den Hang anschließenden Steilhängen zu einem schnellen Grundwasseranstieg, der aufgrund eines gespannten Grundwasserleiters den Druck in die Hangrutschung weitergibt. Dort wird ein Überdruck aufgebaut, der sehr wahrscheinlich die Bewegungen auslöst. Die vorliegende Arbeit ist eine detaillierte Herangehensweise um Erkenntnisse aus der Hyrologie für die Bestimmung des Wasserhaushaltes von Massenbewegungen heranzuziehen.
The objective of this thesis is to improve the knowledge of control mechanisms of hydrological induced mass movements. To this end, detailed hydrological process studies and physically-based hydrological modelling were applied. The study site is a hillslope in the Dornbirn Ache valley near Bregenz, Austria. This so called Heumös slope features a deep-seated translational shear zone and surface near creep movements of up to 10 cm a year. The Cretaceous marlstones of the Austrian Helveticum have a high susceptibility for weathering and might form clay-rich cohesive sediments. In addition, glacial and post-glacial processes formed an unstable hillslope. High yearly precipitation depths of about 2100 mm and rainstorms with both high intensities and precipitation depths govern surface and subsurface hydrological processes. Pressure propagation induced in hydrological active areas influences laterally the groundwater reactions of the moving mass. A complex three-dimensional subsurface pressure system is the cause for fast groundwater reactions despite low hydraulic conductivities. To understand hillslope scale variability, hydrotopes representing specific dominating processes were mapped using vegetation association distribution and soil core analysis. Detailed small-scale soil investigations followed to refine the understanding of these hydrotopes. A perceptional model was developed from the hydrotope distribution and was corroborated by these detailed investigations. The moving hillslope is dominated by surface-runoff generation. Infiltration and deep percolation of water is inhibited through clay-rich gleysols; the yearly average soil moisture is close to saturation. Steep slopes adjacent to the moving hillslope are far more active concerning infiltration, preferential flow and groundwater fluctuations. Spring discharge observations at the toe of the steep slopes are in close relation to groundwater table observations on the moving hillslope body. Evidence of pressure propagation from the steep slopes towards the hillslope body is gathered by comparison of dominating structures and processes. The application of the physically-based hydrological model CATFLOW substantiates the idea of pressure propagation as a key process for groundwater reactions and as a possible trigger for movement in the hillslope.
Rapid expansion of oil palm (Elaeis guineensis Jacq.) cultivation in Southeast Asia raises environmental concerns about deforestation and greenhouse gas emissions. However, less attention was paid to ...the possible perturbation of hydrological functions and water quality degradation. This work aimed to review (i) the agricultural practices commonly used in oil palm plantations, which potentially impact hydrological processes and water quality and (ii) the hydrological changes and associated nutrient fluxes from plantations. Although many experimental trials provide clear recommendations for water and fertilizer management, we found that few studies investigated the agricultural practices actually followed by planters. Our review of hydrological studies in oil palm plantations showed that the main hydrological changes occurred during the first years after land clearing and seemed to dissipate with plant growth, as low nutrient losses were generally reported from plantations. However, most of those studies were carried out at the plot scale and often focus on one hydrological process at a single plantation age. So, there is insufficient information to evaluate the spatiotemporal fluctuations in nutrient losses throughout the entire lifespan of a plantation. Furthermore, few studies provided an integrated view at the watershed scale of the agricultural practices and hydrological processes that contribute to nutrient losses from oil palm plantations and the consequences for surface and groundwater quality. Future research efforts need to understand and assess the potential of oil palm plantations to change hydrological functions and related nutrient fluxes, considering agricultural practices and assessing water quality at the watershed scale.
Water erosion is the major threat to soil and water conservation in the steep lands of the tropics. Besides surface erosion on gentle to moderate slopes, mass movements are common on steep slopes. In ...addition to the negative effects on productivity and crop production risks, in many tropical regions, offsite effects of sedimentation, floodings and landslides are also rooted in accelerated soil erosion. The prediction of water erosion by direct measurements in erosion plots, or by using empirical models has not generally given satisfactory results in the tropics, specially when mass movements are the potential erosion processes. Modeling the surface soil hydrological processes, under the prevailing conditions of climate, use, management and cropping in two selected sites of Venezuela, resulted in fairly accurate simulations of both the soil surface and landslide erosion processes and their main effects. The model SOMORE, used for such simulation, is based on easily available climate and soil input parameters, and produces as the main output the soil moisture regime in a daily basis, including the average soil moisture at root depth, and the water losses by surface and subsurface runoff, and by internal drainage. The output of the model is used as the basis for the selection, with a probabilistic approach, of the best alternatives of use and management of soil and water resources for each combination of soils, climate and topography.
The adverse impacts of invading alien organisms are widely recognized as one of the major threats to biodiversity and are receiving growing recognition as a major socioeconomic threat. The ...hydrological impacts of alien plants have received less attention, despite growing evidence of their significance. The wide range in plant growth forms and physiology among invading species suggests that estimation of the hydrological impacts could be difficult. The concept of limits to evaporation was developed to help organize our general scientific understanding of the hydrological implications of changes in vegetation. It provides a way of reducing this complexity to the factors most likely to be the major determinants of evaporation from vegetation in a given situation. It distinguishes between physical factors (1) availability of energy from solar radiation and advection, (2) availability of soil moisture at landscape and habitat scales, and (3) raindrop size, and biological factors (4) plant size, including height and rooting depth, and (5) plant physiology, including seasonality of the leaves and drought tolerance. Studies of the hydrological impacts of vegetation change invasion show that changes in vegetation structure and seasonality can have significant impacts on water resources at both habitat and landscape scales. Invasions can also have significant impacts where the invaded habitat has more water available within the rooting depth than adjacent areas.
This paper argues that community based wildlife management in the Okavango Delta needs to be analysed and understood within the broader political, ecological and economic trends affecting Botswana as ...a whole. A range of issues, including global economics, competing land use strategies, tenure regimes, global climate change, village economics and settlement patterns, the role of donor agencies and the economic and political transformation of Botswana society in the last thirty years, all impact on the prospects for Community Based Wildlife Management. Some key assumptions (such as the current geographical basis for defining communities) upon which Community Based Wildlife Management has been based need further discussion and debate.
A radial basis function (RBF) neural network (NN) is proposed to develop a rainfall-runoff model for three-hour-ahead flood forecasting. For faster training speed, the RBF NN employs a hybrid ...two-stage learning scheme. During the first stage, unsupervised learning, fuzzy min-max clustering is introduced to determine the characteristics of the nonlinear RBFs. In the second stage, supervised learning, multivariate linear regression is used to determine the weights between the hidden and output layers. The rainfall-runoff relation can be considered as a linear combination of some nonlinear RBFs. Rainfall and runoff events of the Lanyoung River collected during typhoons are used to train, validate,and test the network. The results show that the RBF NN can be considered a suitable technique for predicting flood flow.
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