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Contém referências bibliográficas
Contém referências bibliográficas
Disponível na Biblioteca da ESACB na cota C30-25725TFCRNA.
Relatório do Trabalho de Fim de Curso de Engenharia das Ciências Agrárias – Ramo Agrícola.
Adequate planning of soil and water conservation requires understanding and prediction of the interactions between soil, climate and management scenarios. These interactions have been investigated over the last decades by means of modelling tools. Some of the most widely used models, namely KINEROS, WEPP, SWAT, and AnnAGNPS have been compared in terms of interfaces, processes, data and parameter requirements, to describe their application domain. Some applicative cases are also added to evidence the importance of rainfall regimes, processes scale, land typologies and management for soil and water conservation modelling, to support the needs of farmers, researchers, extension services and land planners. In general, there is evidence of a large number of parameters to satisfy common users' perception of reliability on simulation results, while they are all good teaching and research tools.
Agricultural land degradation is a global problem affecting food production and other ecosystem services worldwide such as water regulation. It is driven by unsustainable land use and management practices (e.g. intensive tillage, overuse of agrochemicals) and can be aggravated by future climate change. Land degradation is particularly problematic in arid and semi-arid areas of southern Europe, and distinct soil degradation processes impair agricultural areas in Portugal and Greece. This chapter aims to improve understanding of various degradation processes affecting agricultural land, including soil erosion, compaction, contamination, and salinity and sodicity. It summarises the scientific literature on the current status of these degradation processes in agricultural areas of Portugal and Greece and their main causes and consequences. Moreover, it provides examples of best management practices implemented to mitigate agricultural land degradation. Some degradation processes are relatively well documented (e.g. erosion), while knowledge of the spatial extent of others such as soil compaction is still limited. A better understanding of soil degradation processes and of the counter-impacts of improved agricultural management practices is critical to support decision-making and ensure long-term fertility and productivity, thereby maintaining the sustainability of agriculture.
Hydrological signatures are indices that help to describe the behavior of catchments. These indices can also be used to transfer information from gauged to ungauged catchments. In this study, different approaches were evaluated to determine volumetric runoff coefficients in 18 small/medium experimental gauged catchments of the Iberian Peninsula and to fit runoff calculations based on precipitation data for gauged and ungauged catchments. Using data derived from 1962 events, rainfall-runoff relationships were characterized and compared in order to evaluate the various hydrological response patterns. Volumetric runoff coefficients and cumulative runoff and precipitation ratios of the events that generated runoff (Rcum) minimized the root mean square error. A linear fit for the estimation of Rcum in ungauged catchments was based on mean annual precipitation, rates of infiltration, the fraction of forest-land use, and the catchment channel length. Despite high catchment heterogeneity, Rcum resulted in a suitable parameter to evaluate hydrological variability in rural gauged and ungauged catchments. In 50% of the catchments, the precipitation
accounted for less than 50% of the runoff variation. Annual precipitation, antecedent rainfall, and base flow did not have a high significance in rainfall-runoff relationships, which illustrates the heterogeneity of hydrological responses. Our results highlight the need for signature characterizations of small/medium rural catchments because they are the sources of runoff and sediment discharge into rivers, and it is more economical and efficient to take action to mitigate runoff in rural locations.
