6 research outputs found
Assessment of regional bestâfit probability density function of annual maximum rainfall using CFSR precipitation data
The upper Cross River basin (UCRB) fits a true description of a data scarce watershed in respect of
climatic data. This paper seeks to determine the bestâfit probability density function (PDF) of annual
maximum rainfall for the UCRB using the Climate Forecast System Reanalysis (CFSR) precipitation data.
Also, to evaluate the performance of the Intergovernmental Panel on Climate Change (IPCC) Coupled
Model Interâcomparison Project (CMIP3) Fourth Assessment Report (AR4) Global Circulation Models
(GCMs) in simulating the monthly precipitation in the UCRB considering 1979â2014 data. For the
determination of the bestâfit PDF, the models under review included the generalized extreme value
(GEV), normal, gamma, Weibull and logânormal (LN) distributions. Twentyâfour weather station datasets
were obtained and subjected to frequency distribution analysis on per station basis, and subsequently
fitted to the respective PDFs. Also, simulated monthly precipitation data obtained from 16 AR4 GCMs,
for weather station p6191, were subjected to frequency distribution analysis. The results showed the
percentages of bestâfit to worstâfit PDFs, considering the total number of stations, as follows: 54.17%,
45.83%, 37.50%, 45.83%, and 50%/50%. These percentages corresponded to GEV, Weibull, gamma,
gamma, and LN/normal, respectively. The comparison of the predicted and observed values using the
Chiâsquare goodnessâofâfit test revealed that the GEV PDF is the bestâfit model for the UCRB. The
correlation coefficient values further corroborated the correctness of the test. The PDF of the observed
data (weather station p6191) and the simulations of the 16 GCMs computed using monthly rainfall
datasets were compared using a mean square error (MSE) dependent skill score. The result from this
study suggested that the CGCM3.1 (T47) and MRIâCGCM2.3.2 provide the best representations of
precipitation, considering about 36 years trend for station p6191. The results have no influence on how
well the models perform in other geographical locations
Development of storm hydrographs for three rivers within drainage network in Kwara state, Nigeria using Snyder's method
This paper presents the development of unit and storm hydrographs for Rivers Moro, Asa and Oyun catchment. Snyder's method was used to develop the unit hydrographs; while the SCS Curve Number method was used to estimate excess rainfall values from rainfall depth of different return periods. The design storm hydrographs corresponding to.the excess rainfall values were determined based on the unit hydrograph ordinates established through convolution. The design storm hydrograph obtain~d for Moro River catchment based on 5-yr, 20~yr~ 50-yr, 100-yr and 200-yr return period ranged between 245.29m3/s and 685.84m3/s. That of Asa River catchment varied from 301.34m3/s to 846.46m3/s and the design storm hydrograph flows obtained for Oyun River catchment varied from 257 .29m3/s to 723.56m3/s. The design storm hydrograph flows obtained can be recommended for sizing hydraulic structures within Kwara State drainage network.Keywords: Unit hydrograph, stonn hydrograph, storm duration, River catchment and recurrence interva