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[en] This study investigates the long-term trends in precipitation, runoff and runoff coefficient in major urban watersheds in the United States. The seasonal Mann–Kendall trend test was performed on monthly precipitation, runoff and runoff coefficient data from 1950 to 2009 obtained from 62 urban watersheds covering 21 major urban centers in the United States. The results indicate that only five out of 21 urban centers in the United States showed an uptrend in precipitation. Twelve urban centers showed an uptrend in runoff coefficient. However, six urban centers did not show any trend in runoff coefficient, and three urban centers showed a significant downtrend. The highest rate of change in precipitation, runoff and runoff coefficient was observed in the Houston urban watershed. Based on the results obtained, we also attributed plausible causes for the trends. Our analysis indicated that while a human only influence is observed in most of the urban watersheds, a combined climate and human influence is observed in the central United States. (letter)
[en] Artificial radionuclides from a variety of sources exist in drainage basin soils. Erosive processes result in their re-distribution and eventual removal from catchments. Existing data relating to removal rates and response times of run-off to single radionuclide inputs are summarised and the possible reasons for varying rates are examined. (author)
[en] The objective of this study is modeling runoff by hydrological, distributed physically based Model, KINEROS2. This model has allowed after calibration to analyze and simulate the hydrological behavior of the watershed Ghezala .The Watershed Ghezala is located in north of Tunisia, in the governorate of Bizerte. It belongs to the bioclimatic mild winter. It covers an area of 4723h, at this watershed; the dominating slop is between 8and 15 pour cent which covers the almost area of the watershed. Dominant type of soil is Calcareous brown guy covering almost 54 pour cent of its total area; Land cover is characterized by the dominance of grain covering 73 pour cent of watershed area. KINEROS2 requires the division of the watershed into plain and channels cascading from upstream to downstream taking into consideration of flow, the geology and land cover of the watershed. During the calibration observed and simulated hydrographs, it must be based on the more sensitive parameters of the model: K (saturated hydraulic conductivity) G (net effective capillary conductivity) and n (parameter Mannig). The calibration's result shows that the error does not exceed, 1pour cent for liquid peak flows of flood hydrographs observed and simulated, 17pour cent for the volume of raw observed and simulated. Thus, the analysis of the hydrological behavior of the watershed studied through the hydrological response to a solicitation (intensity of rain: rain), simulates flood by applying the KINEROS2 model and observing the quantity of water flowing at the outflow of the system (flood hydrograph or rainfall).
[en] Seven tree-ring chronologies are used to reconstruct Teberda River (Northern Caucasus, Russia) smoothed runoff for May, July and August. Six chronologies were developed from Pinus sylvestris and one from Abies nordmanniana. Tree growth is significantly, but weakly, correlated with maximum temperatures (negatively) and relative humidity (positively) during summer. All possible combinations of seven predictors were tried to get the best result on the cross-validation. Two of three reconstructions showed high wavelet coherence with instrumental data on decadal timescales and were analysed for spectrum stability. Minima of moving trends at the end of the reconstructions along with weakening of decadal cycles may be a marker of significant change of Teberda River hydrological regime during the second half of the 20th century.
[en] Several hypotheses claim that more extremes in climatic and hydrologic phenomena are anticipated. In order to verify such hypotheses it is inevitable to examine the past periods by thoroughly analyzing historical data. In the present study, the annual maximum runoff volumes with t-day durations were calculated for a 130-year series of mean daily discharge of Danube River at Bratislava gauge (Slovakia). Statistical methods were used to clarify how the maximum runoff volumes of the Danube River changed over two historical periods (1876-1940 and 1941-2005). The conclusion is that the runoff volume regime during floods has not changed significantly during the last 130 years.
[en] The perception of water as a resource differ depending on the society and the prevailing environment. In areas where water is scarce, it's necessity for sustaining basic life process is obvious and hence it's value is perceived to be very high and the quality of drinking water available for humans and animals takes top priority. It is therefore necessary to improve water maintenance by adopting strategies that include; improve awareness of water resource management at all levels of the society, change of attitude towards water resources, account for water use by evaluating efficiency, assess water and degradation process among others