Time of concentration (TC) of surface flow in watersheds depends on the coupled response of hillslopes and stream networks. The important point in this background is to study the effects of the geometry and the shape of complex hillslopes on the time of concentration considering the degree of flow convergence (convergent, parallel or divergent) as well as the profile curvature (concave, straight or convex). In this research, the shape factor of complex hillslopes as introduced by Agnese et al. (2007) is generalized and linked to the TC. A new model for calculating TC of complex hillslopes is presented, which depends on the plan shape, the type and degree of profile curvature, the Manning roughness coefficient, the flow regime, the length, the average slope, and the excess rainfall intensity. The presented model was compared to that proposed by Singh and Agiralioglu (1981a,b) and Agiralioglu (1985). Moreover, the results of laboratory experiments on the travel time of surface flow of complex hillslopes were used to calibrate the model. The results showed that TC for convergent hillslopes is nearly double those of parallel and divergent ones. TC in convex hillslopes was very close to that in straight and concave hillslopes. While the effect of convergence on TC is considerable, the curvature effect confirmed insignificant. Finally, in convergent hillslopes, TC increases with the degree of convergence, but in divergent hillslopes, it decreases as degree of divergence increases.
Time sensitivity seems to affect our intuitive evaluation of the reasonable risk of fallibility in testimonies. All things being equal, we tend to be less demanding in accepting time sensitive testimonies as opposed to time insensitive testimonies. This paper considers this intuitive response to testimonies as a strategy of acceptance. It argues that the intuitive strategy, which takes time sensitivity into account, is epistemically superior to two adjacent strategies that do not: the undemanding strategy adopted by non-reductionists and the cautious strategy adopted by reductionists. The paper demonstrates that in adopting the intuitive strategy of acceptance, one is likely to form more true beliefs and fewer false beliefs. Also, in following the intuitive strategy, the listener will be fulfilling his epistemic duties more efficiently.
The main intent of this paper is to present a review on the application of time series analysis techniques in hydrology and climatology. An overview of various statistical tests for detecting and estimating the hydrologic time series characteristics (i.e., homogeneity, stationarity, trend, periodicity, and persistence) is presented, together with their merits and demerits followed by comprehensive reviews of past studies (both basic and applied), and future research directions. The present review revealed that the climatologic time series of precipitation, air temperature, evapotranspiration and climatic change, and the hydrologic time series of streamflow and surface water quality have received a great deal of attention worldwide. Although the application areas of time series analysis techniques are expanding with growing concerns about climate change and global warming, their application is still very limited in groundwater hydrology as well as for non-traditional hydrologic time series. It is also apparent from this review that the detection of trend and stationarity by parametric and/or nonparametric tests has been a major focus in the past. Multiple comparison tests lack appreciation by the researchers for testing homogeneity in the hydrologic and climatologic time series. Furthermore, most studies have ignored the importance of testing periodicity and persistence in the time series, which are equally important properties of hydrologic and climatologic time series. Based on the comprehensive review, future research needs for time series studies in hydrology and climatology are discussed. and Príspevok prináša prehľad aplikácií techník analýzy časových radov v hydrológii a klimatológii. Uvádza prehľad rôznych štatistických testov na zistenie charakteristík týchto radov (napr. homogenity, stacionarity, trendov, periodicity a perzistencie), spolu s ich prednosťami a nedostatkami. Ďalej je uvedený tiež celkový prehľad uskutočnených štúdií (základných aj aplikovaných) a smery výskumu pre budúcnosť. Súčasný prehľad naznačuje celosvetové sústredenie pozornosti na časové súbory klimatologických dát zrážok, teploty vzduchu, evapotranspirácie a zmien klímy, a tiež hydrologických dát prietokov a kvality povrchových vôd. Aj keď so zvýšením záujmu o zmenu klímy a globálne otepľovanie sa oblasti použitia techník analýzy časových radov rozširujú, ich aplikácie v oblasti hydrológie podzemných vôd a ďalších nie celkom tradičných hydrologických údajov sú veľmi obmedzené. Tento prehľad tiež uvádza, že v minulosti sa vyskytli snahy o sústredenie úsilia na postihnutie trendov a stacionarity radov použitím parametrických a/alebo neparametrických testov. Mnohí výskumníci dostatočne neoceňujú viacnásobné porovnávacie testy (multiple comparison tests) homogenity hydrologických a klimatických časových radov. Okrem toho vo väčšine štúdií sú zanedbané dôležité testy periodicity a perzistencie hydrologických radov. Tieto sú ich rovnako dôležité charakteristiky. Na základe všeobecného prehľadu príspevok tiež pojednáva o potrebe ďalšieho výskumu časových radov v hydrológii a klimatológii.