Browsing by Author "Rathnayake, U. S."

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    Hydrological assessment of flow in Uma Oya, Sri Lanka
    (Uva Wellassa University of Sri Lanka, 2015) Rathnayake, U. S.
    A current meter is usually used in river flow measurements. However, if someone is interested in obtaining the temporal variation of a particular river, it may not be the easiest method in the world to use a current meter (i.e. daily) to measure the flow rate. In such events, the stage measurements can be taken and then, they can be converted to the flow rates (USGS, 2014). One can use the stage-discharge relationship to find the corresponding flow rate (Mortuza et al., 2011; Raj and Azeez, 2009; Gupta and Chakrapani, 2005). However, this method still requires some flow measurements to produce the stage-discharge relationship. Therefore, a current meter should be there to measure the velocities and then, to calculate the flow rates. In case of absence of a current meter, one has to think another way of obtaining the flow hydrograph. This paper presents a simple approach in obtaining the flow hydrograph for a river in Sri Lanka: Uma Oya. Uma Oya catchment is being modeled and this study shows some preliminary results. The detailed flow hydrograph for Uma Oya for a longer period is being developed for the frequency analysis. The developed flow hydrograph is being used to model the Uma Oya catchment in Sri Lanka. Uma Oya catchment The catchment of Uma Oya upper watershed was found to be around 750 km (Dam safety and Water resources planning project component report, 2010; Dissanayake et al., 2010). However, a detailed catchment analysis is being carried out and the catchment areas will be listed in the future publications. Since it is in upcountry of Sri Lanka, steep slopes are quite frequent along the river. It has even reached about 1900 m MSL (Dissanayake et al., 2010). The catchment is basically a green catchment. Natural forests, tea estates, paddy fields and potato farming lands are commonly seen in the catchment (Dam safety and Water resources planning project component report, 2010; Dissanayake et al., 2010). Natural forests cover the highest elevations. Then, tea estates, potato farms and other vegetable and paddy fields cover the lower elevations. Uma Oya is one of the main tributaries in Mahaweli River. It flows into the Rantambe reservoir (refer Figure 4). The upper catchment is hardly conserved from soil erosion; therefore, a significant amount of sediment flows into the reservoir. Sediment deposition can be visually evidenced in the Rantembe reservoir. Therefore, the reservoir faces the reduction of its water holding capacity and then, the reduction of electric generation capacity. In addition, Uma Oya catchment is one of the rainy catchments in the country. Therefore, it has a wealthy sediment flow.