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Analysis of Drought and Wet-Events Using SWSI-Based Severity-Duration-Frequency (SDF) Curves for the Upper Tana River Basin, Kenya
Raphael Muli Wambua,
Benedict Mwavu Mutua,
James Messo Raude
Issue:
Volume 6, Issue 2, June 2018
Pages:
43-52
Received:
3 May 2018
Accepted:
22 May 2018
Published:
12 June 2018
Abstract: Drought and wet-event patterns in the Upper Tana River basin have significantly been changing due to variation of climatic and human-induced factors. This paper presents the analysis of drought and wet-events using Severity-Duration-Frequency (SDF) curves for the Upper Tana River basin, Kenya based on Surface Water Supply Index (SWSI). The extreme value EV1 (Gumbel) frequency distribution function was used to formulate SDF curves. The developed SDF curves were used to develop isoseverity maps for the basin. From the results, the event-probability show that likelihood of drought events increased linearly with increase in magnitude of SWSI while the return period of drought events increased exponentially with decrease in magnitude of SWSI. The findings show that the probability and magnitude, the return period and magnitude of drought have linear and exponential regression coefficients of 0.984 and 0.980 respectively. On the other hand the probability of wet-period events decreased linearly with increase in magnitude of SWSI while the return period of the events increased exponentially with increase in magnitude of SWSI with regression coefficients of the linear and exponential functions of 0.804 and 0.881 respectively. This indicates that both the drought and wet-events probability and magnitude, and the return period and magnitude have a strong correlation. Spatially, it was found that generally the river basin exhibit an increasing pattern in cumulative SWSI in south-eastern areas than the north-eastern and generally a more increase in extreme wet-events than droughts in the basin. The developed (SDF) curves are critical for design of hydrologic, hydraulic and water resources supply systems while the spatial event-patterns can be incorporated in prioritized mitigation of extreme events.
Abstract: Drought and wet-event patterns in the Upper Tana River basin have significantly been changing due to variation of climatic and human-induced factors. This paper presents the analysis of drought and wet-events using Severity-Duration-Frequency (SDF) curves for the Upper Tana River basin, Kenya based on Surface Water Supply Index (SWSI). The extreme ...
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Spatial Flow and Outflow Distribution in the Una Basin
Issue:
Volume 6, Issue 2, June 2018
Pages:
53-60
Received:
27 April 2018
Accepted:
17 May 2018
Published:
4 July 2018
Abstract: The need and importance of studying the water regime in higher and mountainous areas, as well as hypsometric zoning are extremely large in regional and spatial planning. The aspect of spatial regionalization has enabled the understanding of the distribution of water in the basin itself. Based on that, a wider picture of the state of this distribution was obtained in some regional units. Getting involved in solving issues related to gaining values of the river regime’s certain elements by hypsometric zones in the Una basin, the basic parameter which it was started from, was determining the value of precipitation amount. For assessment of flow and specific outflow and height, the relation has been applied: precipitation – elevation – area of hypsometric zones – evapotranspiration. Depending on the area they occupy, in the structure of specific outflows and flows, one can clearly distinguish three zones, up to 400 m altitude, the second hypsometric zone from 400 m up to 1400 m, and the third zone above 1400 m altitude. To determine the water height distribution, there have been used the hypsography of the basin and regional specific outflow dependence on average elevation of the basin. Processing all parameters relevant for studying in this paper is done in the ArcGIS software package. The obtained results of this research are very important and can be applied for the needs of agriculture, water management, urbanism and tourism of this part of Bosnia and Herzegovina.
Abstract: The need and importance of studying the water regime in higher and mountainous areas, as well as hypsometric zoning are extremely large in regional and spatial planning. The aspect of spatial regionalization has enabled the understanding of the distribution of water in the basin itself. Based on that, a wider picture of the state of this distributi...
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Ouémé River Catchment SWAT Model at Bonou Outlet: Model Performance, Predictive Uncertainty and Multi-Site Validation
Berenger Arcadius Sêgnonnan Dègan,
Eric Adéchina Alamou,
Yèkambèssoun N’Tcha M’Po,
Abel Afouda
Issue:
Volume 6, Issue 2, June 2018
Pages:
61-77
Received:
23 July 2018
Accepted:
10 August 2018
Published:
5 September 2018
Abstract: In a soudano-guinean climate context, the Ouémé River Basin is simulated using the semi-distributed hydrological model SWAT to understand the rainfall-runoff process on this basin and also to assess this model performance on West Africa large areas basins at daily and monthly time steps. The inputs data consist of climatic data and rain gauge discharge records. The inputs records are long-term times series for the period 1979-2010, while the considered land use is just for the year 2003. After calibration and validation of the model, spatial calibration is also performed to appreciate this other feature of the model. It gives such acceptable and disputable results. Six (06) hypotheses have been emitted to analyze this performance loss. It comes out that hypothesis H5 results perform better both in calibration and validation. This hypothesis used data for the period 1993-2010 with 1993-2004 for calibration and 2005-2010 for validation; and considered the missing data in discharge records without any completion. Considering the internal rain gauge outlet performance for this hypothesis, the best is retained and the corresponded project is realized for each individual subbasin to see how best the model could simulate discharge for the Bétérou, Kaboua and Atchérigbé individual subbasins. Hypothesis H1; an assumption which considers missing discharge with data time period of 1982-2010 with 1982-1996 for calibration and 1997-2010 for validation; is the best for Bétérou and Kaboua, whereas H5 is better for Atchérigbé subbasin. Uncertainty analysis and Global Sensitivity Analysis were performed to appreciate what are this process occurring in the basin and how these results could be validated. A last comparison effort is performed with 10km rainfall grid for climatic rainfall data at the global catchment outlet; this approach does not improve results, while at internal outlet some improvements are observed.
Abstract: In a soudano-guinean climate context, the Ouémé River Basin is simulated using the semi-distributed hydrological model SWAT to understand the rainfall-runoff process on this basin and also to assess this model performance on West Africa large areas basins at daily and monthly time steps. The inputs data consist of climatic data and rain gauge disch...
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