Publications
NIBIOs employees contribute to several hundred scientific articles and research reports every year. You can browse or search in our collection which contains references and links to these publications as well as other research and dissemination activities. The collection is continously updated with new and historical material.
2016
Abstract
We investigate a set of long-term (several decades) time series for the runoff at river gauges at daily resolution. They are monitored by the Agencia Nacional de Aguas, and time series provided by the Operador Nacional do Sistema Elétrico, Brazil. A total of 150 time series was obtained, with an average length of 73 years. Both long-term trends as well as the influence of extreme events on the dynamical behaviour are analyzed. We use Horizontal Visibility Graphs (HVGs) to determine the individual temporal networks for the time series, and extract their degree distributions. Statistical and information-theoretic properties of these distributions are calculated: robust estimators of skewness and kurtosis, the maximum degree occurring in the time series, the Shannon entropy, permutation complexity and Fisher Information. For the latter, we also compare the information measures obtained from the degree distributions to those using the original time series directly, to investigate the impact of graph construction on the dynamical properties as reflected in these measures. Focus is on one hand on universal properties of the HVG, common to all runoff series, and on site-specific aspects on the other. We show that a specific pretreatment of the time series conventional in hydrology, the elimination of seasonality by a separate z-transformation for each calendar day, is highly detrimental to the nonlinear behaviour. It changes long-term correlations and the overall dynamic towards more random behaviour. Analysis based on the transformed data easily leads to spurious results, and bear a high risk of misinterpretation.
Authors
Stein Michael TomterAbstract
No abstract has been registered
Abstract
No abstract has been registered
Abstract
No abstract has been registered
Authors
Oskar PuschmannAbstract
No abstract has been registered
Authors
Stein Michael TomterAbstract
No abstract has been registered
Lecture – Norwegian policy and practice regarding mitigation measures in agriculture
Inga Greipsland
Authors
Inga GreipslandAbstract
No abstract has been registered
Authors
Inga GreipslandAbstract
Norway has adopted the Water Framework directive and intends to achieve good ecological status in all water bodies by 2021. The environmental condition of Norwegian rivers and lakes are good compared to those in most other countries in Europe. A preliminary survey of the status of all Norwegian water bodies shows that around 50 % probably will meet the EU objectives/requirements for the freshwater environment, while around a quarter are at risk with regards to the requirements (Snellingen Bye et al., 2010). For the remaining water bodies, data are not available or their status is uncertain. Agriculture has been identified as the third most important factor influencing the status of Norwegian fresh water bodies.
Authors
Adam ParuchAbstract
No abstract has been registered
Abstract
No abstract has been registered