Extenuating the parameters using HEC-HMS hydrological model for ungauged catchment in the central Omo-Gibe Basin of Ethiopia          下载免费PDF全文

Demisse Habtamu Semunigus  Ayalew Abebe Temesgen  Ayana Melkamu Teshome  Lohani Tarun Kumar 《地下水科学与工程》2021,9(4):317-325

Characteristics of ungauged catchments can be studied from the hydrological model parameters of gauged catchments. In this research, discharge prediction was carried out in ungauged catchments using HEC-HMS in the central Omo-Gibe basin. Linear regression, spatial proximity, area ratio, and sub-basin mean were amalgamated for regionalization. The regional model parameters of the gauged catchment and physical characteristics of ungauged catchments were collated together to develop the equations to predict discharge from ungauged catchments. From the sensitivity analysis, crop coefficient (CC), storage coefficient (R), constant rate (CR), and time of concentration (TC) are found to be more sensitive than others. The model efficiency was evaluated using Nash–Sutcliffe Efficiency (N_SE) which was greater than 0.75, varying between ?10% and +10% and the coefficient of determination (R²) was approximated to be 0.8 during the calibration and validation period. The model parameters in ungauged catchments were determined using the regional model (linear regression), sub-basin mean, area ratio, and spatial proximity methods, and the discharge was simulated using the HEC-HMS model. Linear regression was used in the prediction where p-value ≤ 0.1, determination coefficient (R²) = 0.91 for crop coefficient (CC) and 0.99 for maximum deficit (MD). Constant rate (CR), maximum storage (MS), initial storage (IS), storage coefficient (R), and time of concentration (TC) were obtained. The result is that an average of 30 m³/s and 15 m³/s as the maximum monthly simulated flow for ungauged sub-catchments, i.e. Denchiya and Mansa of the main river basin .  相似文献   

Discussion of the Technical Note “Seismic Passive Earth Thrust on Retaining Walls with Cohesive Backfills using Pseudo-Dynamic Approach” by A.H. Shafiee, A. Eskandarinejad, M. Jahanandish: Geotechnical and Geological Engineering, DOI 10.1007/s10706-010-9327-3     

Sanjay Kumar Shukla 《Geotechnical and Geological Engineering》2010,28(6):929-930

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Bearing capacity of strip foundations reinforced with geogrid sheets by using upper bound finite‐element limit analysis     

Jyant Kumar  Jagdish Prasad Sahoo 《国际地质力学数值与分析法杂志》2013,37(18):3258-3277

By using the upper bound finite‐elements limit analysis, with an inclusion of single and two horizontal layers of reinforcements, the ultimate bearing capacity has been computed for a rigid strip footing placed over (i) fully granular, (ii) cohesive‐frictional, and (iii) fully cohesive soils. It is assumed that (i) the reinforcements are structurally strong so that no axial tension failure can occur, (ii) the reinforcement sheets have negligible resistance to bending, and (iii) the shear failure can take place between the reinforcement and soil mass. It is expected that the different approximations on which the analysis has been based would generally remain applicable for reinforcements in the form of geogrid sheets. A method has been proposed to incorporate the effect of the reinforcement in the analysis. The efficiency factors, η_c and η_γ, to be multiplied with N_c and N_γ , for finding the bearing capacity of reinforced foundations, have been established. The results have been obtained (i) for different values of ? in case of fully granular and cohesive‐frictional soils, and (ii) for different rates at which the cohesion increases with depth for a fully cohesive soil. The optimum positions of the reinforcements' layers have also been determined. The effect of the reinforcements' length on the results has also been analyzed. As compared to cohesive soils, the granular soils, especially with higher values of ?, cause a much greater increase in the bearing capacity. The results compare reasonably well with the available theoretical and experimental data from literature. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

Erratum to: Seismicity of Gujarat     

B. K. Rastogi  Santosh Kumar  Sandeep Kumar Aggrawal 《Natural Hazards》2012,62(3):1347-1348

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Fluoride enrichment in aquifers of the Thar Desert: controlling factors and its geochemical modelling     

Chander Kumar Singh  Rina Kumari  Neha Singh  Javed Mallick  Saumitra Mukherjee 《水文研究》2013,27(17):2462-2474

The groundwater is the only source of drinking water in the Jaisalmer district of Rajasthan, India. The study area is a part of the Thar Desert. It has low and scattered population and no industries; hence, the possibility of anthropogenic input of fluoride is almost negligible. Thus, the enrichment of fluoride is only possible due to geochemical processes taking place in the groundwater of the region. A total of 100 groundwater samples, 34 samples from Jaisalmer and 66 samples from the Pokharan administrative blocks, were collected. It was observed that the concentration of fluoride ranged from 0.08 mg/l to 4.56 mg/l in the groundwater of Jaisalmer and from 0.56 mg/l to 6.60 mg/l in the samples of the Pokharan block. The alkaline condition (average pH, 7.7 ± 0.22 and 8.01 ± 0.25 in Jaisalmer and the Pokharan administrative block, respectively) in the region favours fluorite dissolution. Ion exchange, dissolution of calcite, semi‐arid climate, alkaline conditions and weathering are responsible for fluoride enrichment in the groundwater of the study area. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

Latitudinal variation of air sea fluxes in the western Indian ocean during austral summer and fall     

M. R. Ramesh Kumar  L. V. Gangadhara Rao 《Boundary-Layer Meteorology》1989,48(1-2):99-107

Daily and zonal (latitudinal belt) averages of heat and momentum fluxes were computed using bulk aerodynamic formulae, from the meteorological parameters measured onboard M. S. Thuleland during the sixth Indian scientific expedition to Antarctica (26th November, 1986 to 22nd March, 1987). Both estimates showed significant variations, the momentum flux showing the largest variation. The maximum values of sensible and latent heat fluxes were observed over the 30°–40° S and 10°–20° S zones during the southern summer and fall respectively while the minimum values of latent heat flux were observed in the 60°–70° S zone for both seasons. The sensible heat flux minimum was observed in the 50°°60° S and 60°–70° S zones for summer and fall, respectively. Higher momentum flux values over the 40°–50° S zone in summer shifted to the 50°–60° S zone during fall.  相似文献   

Surface heat budget of a polynya in the coastal waters off Queen Maud Land, Antarctica, during austral summer     

M.R. Ramesh Kumar  Y. Sadhuram 《Continental Shelf Research》1989,9(12)

The daily surface heat budget of a polynya in the coastal waters off Queen Maud Land, Antarctica is studied for the period from 23 December 1986 to February 1987 using the surface meteorological data collected on board the Swedish vessel M.S. Thuleland.The incoming solar radiation was found to be the most important component in the surface heat budget; its mean value for the study period was found to be about 209 W m⁻². The latent and sensible heat fluxes were found in opposition and nearly balancing each other out. The average net heat gain over the polynya, for the study period, was 141 W m⁻². From the mean heat storage values obtained from the temperature profiles, the heat gain at the surface is seen to be almost lost through advection and other interior physical processes in the top 50 m layer of the water column. This is reflected in sea surface temperature which was almost steady during the study period.  相似文献   

Long-Term variability of the indian summer monsoon and related parameters     

G. B. Pant  K. Rupa Kumar  B. Parthasarathy  H. P. Borgaonkar 《大气科学进展》1988,5(4):469-481

The long-term variability of the Indian summer monsoon rain-fall and related regional and global param-eters are studied. The cubic spline is used as a digital filter to smooth the high frequency signals in the time series of the various parameters. The length of the data series varies from 95 to 115 years during the period 1871-1985. The parameters studied within the monsoon system are: (a) monsoon rainfall of the country as a whole; (b) number of break-monsoon days during July and August; (c) number of storms/ depressions in Bay of Bengal and Arabian Sea during summer monsoon season; and (d) dates of onset of summer monsoon over South Kerala Coast. The parameters studied outside the monsoon system are: (a) the Wright’s Southern Oscillation Index (June-July-August); (b) the January mean Northern Hemi-spheric surface air temperature anomaly; and (c) the East-equatorial Pacific sea surface temperature anomaly.In order to examine the variability under various degrees of the smoothing, the series are filtered with splines of 50% variance reduction frequency of one cycle per 10, 20 and 30 years. It is observed that the smoothed time series of the parameters within the monsoon system comprise a common slowly varying com-ponent in an episodic manner distinctly showing the excess and deficient rainfall epochs. The change of intercorrelations between the time series with increasing degree of smoothing throws some light on the time scales of the dominant interactions. The relation between Southern Oscillation and East equatorial Pacific sea surface temperature and the Indian summer monsoon seems to be dominant on the interannual scale. The low frequency variations are found to have significantly contributed to the instability of the correlations of monsoon rainfall with parameters outside the monsoon system.  相似文献   

Some results of night-time scintillations at low latitude     

Sushil Kumar  S K Vijay  A K Gwal 《Journal of Earth System Science》1993,102(2):307-312

Ionospheric scintillation observations of VHF radio signals from FLEETSAT satellite (73°E longitude) at Bhopal from January 1990 to December 1990 have been used to study the characteristic variations of scintillation activity. It is found that scintillation occurrence is essentially a night-time phenomenon and day-time scintillations are very rare. Annual average nocturnal variation of percentage occurrence of scintillations shows maximum at around 2100–2200 hours LT. Seasonally, scintillations are most prominent during equinoxes and least during summer. Geomagnetic disturbances tend to decrease the occurrence of scintillations in the pre-midnight period.  相似文献   

A probability-weighted moment test to assess simple scaling     

Praveen Kumar  Peter Guttarp  Efi Foufoula-Georgiou 《Stochastic Environmental Research and Risk Assessment (SERRA)》1994,8(3):173-183

We present a statistically robust approach based on probability weighted moments to assess the presence of simple scaling in geophysical processes. The proposed approach is different from current approaches which rely on estimation of high order moments. High order moments of simple scaling processes (distributions) may not have theoretically defined values and consequently, their empirical estimates are highly variable and do not converge with increasing sample size. They are, therefore, not an appropriate tool for inference. On the other hand we show that the probability weighted moments of such processes (distributions) do exist and, hence, their empirical estimates are more robust. These moments, therefore, provide an appropriate tool for inferring the presence of scaling. We illustrate this using simulated Levystable processes and then draw inference on the nature of scaling in fluctuations of a spatial rainfall process.  相似文献