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L. J. TISON 《水文科学杂志》2013,58(1):5-8
Abstract A simple method is used to study the response of runoff in the Sahel to climate change. The statistical characteristics of rainfall are calculated over the western part of the Sahel for the period 1961–1990, using the BADOPLU network. Daily rainfall is simulated using a Markov process with Weibull distribution for rainfall depths. Runoff is modelled using a conceptual SCS model and the curve numbers are calculated for West Africa. Climate change is provided by simulations using the Arpège GCM (Scenario A1B), and a perturbation method is used on the parameters which describe the rainfall. Changes in rainfall are assumed to occur through increases in frequency, not intensity. Using Arpège, runoff is mainly found to increase, in depth and in number of events, by the end of the 21st century. Changes in evaporation and land use are not included in the analysis. The impact of this 21st century potential climate change (rainfall) on the runoff is found to be of the same magnitude as the impact of changes in land use. 相似文献
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Abstract In the Southwestern intermountain and high plains areas, precipitation is seasonal, with the major part of the rainfall occurring in the summer. Most winter precipitation occurs as low-intensity rain or snow along slow-moving cold fronts. Most summer precipitation occurs as short-duration, high-intensity thunderstorms from purely convective buildup or from convective cells developing along a weak fast-moving cold front. Almost all runoff occurs from the summer convective storms. Since runoff-producing precipitation is of primary interest at the Southwest Watershed Research Center, Agricultural Research Service, Tucson, Arizona, the convective storms have been most thoroughly analyzed. Duration, intensity, areal extent, movement, character, and return frequencies for varying volumes and intensities of these convective storms are analyzed from records from dense networks of recording rain gages in four study areas in Arizona and New Mexico. The primary study areas are the 58-square-mile Walnut Gulch Experimental Watershed at Tombstone, Arizona, and the 67-squaremile Alamogordo Creek Watershed near Santa Rosa, New Mexico. Three “record” storms of differing character occurring in 1960 and 1961 on Alamogordo Creek Watershed and one “record” storm in 1961 on the Wlanut Gulch Watershed are analyzed and compared in detail. 相似文献
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W. H. Ward 《水文科学杂志》2013,58(1):85-101
AbstractA new method is presented to generate stationary multi-site hydrological time series. The proposed method can handle flexible time-step length, and it can be applied to both continuous and intermittent input series. The algorithm is a departure from standard decomposition models and the Box-Jenkins approach. It relies instead on the recent advances in statistical science that deal with generation of correlated random variables with arbitrary statistical distribution functions. The proposed method has been tested on 11 historic weekly input series, of which the first seven contain flow data and the last four have precipitation data. The article contains an extensive review of the results.Editor D. KoutsoyiannisCitation Ilich, N., 2014. An effective three-step algorithm for multi-site generation of stochastic weekly hydrological time series. Hydrological Sciences Journal, 59 (1), 85–98. 相似文献
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SUMMARY Basing their studies on an extended Reynolds principle of similarity, the authors present in this paper a thorough theoretical investigation of the turbulent flow in pipes. Making appropriate assumptions regarding the distribution of the turbulent apparent viscosity over the entire pipe diameter, the well-known discharge formulas, i. e. the resistance laws, of Prandtl-V. Kármán for the hydraulically smooth and the hydraulically rough region, and of Colebrook for the transition region—the accuracy of these being well established by measurements—can be clearly shown to be correct. Thus it is also possible to determine the velocity distribution in the region near the wall for the hydraulically smooth region and the transition region, as well as for the hydraulically rough region. The concept, that the flow with a fully developed roughness effect begins when the laminar boundary layer at the wall disappears can be seen to be in close agreement with the asssumptions made. The limits which were established for the hydraulically rough region and the transition region correspond well with the curve plotted by PRANDTL and the boundary curve of Rouse. 相似文献
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Gordon E. KOBERG 《水文科学杂志》2013,58(3):37-40
Abstract By means of the energy-budget method, measurements of evaporation losses from four reservoirs on Salt River, Ariz., were determined to range from 57.5 to 69.9 inches for the 12-month period April 1958 to March 1959. Water is withdrawn from Roosevelt Lake at considerable depth and released through three run-of-the-river reservoirs. Because the water released from Roosevelt Lake is cold, evaporation losses from the downstream reservoirs are considerably lower than those from Roosevelt Lake. Evaporation pan coefficients computed for the various reservoirs ranged from 0.53 to 0.65. A base evaporation rate was computed for each reservoir as the evaporation rate that would have occurred had there been no change in energy storage and the net advected energy equalled zero during the year. 相似文献