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Author: search.filters.author.Dwarakish, G.S.Subject: search.filters.subject.Runoff

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    Changes in hydrology and coastal sedimentation by dams—a case study
    (2009) Abdu Rahiman, K.U.; Dwarakish, G.S.; Kawal, B.M.
    The sustainability of coasts depends on intermittent deliveries of sediments from rivers and streams. This fluvial sediment delivery has been greatly reduced by dams, which prevent the sediment from reaching the coast and nourishing the beaches naturally. Dams alter the downstream flow system of rivers. River hydrology were mainly affected by dams, through changes in the frequency, magnitude and timing of flows, ultimately creating a hydrologic system differing significantly from the pre- impoundment natural flow system. This paper describes the effects of 15 dams in Periyar river basin, Kerala, on river hydrology and sedimentation in Cochin coast. Hydrological, river sedimentation and reservoir sedimentation analyses of Periyar river were carried out using rainfall, discharge and sediment load data collected from India Meteorological Department (IMD), Central Water Commission (CWC) and Kerala State Electricity Board (KSEB). The results show that the net runoff of Periyar river is reduced by 41 % mainly because of the impoundment of dams. The net sediment transport of Periyar river towards Cochin coast during the 25 year period was also estimated. The total quantity of sediment trapped in all the reservoirs in Periyar river was calculated, by using Brune's curves. The results showed a distinct reduction in sediment load in Periyar river mainly due to the interference of dams. The total amount of sediment trapped in all the reservoirs in Periyar river up to 2006 is estimated as 205 million tons, which is nearly 27 times the total sediment load transported by Periyar river towards Cochin coast (7.545 million tons), during the 25 year period (1978 to 2002). © 2009 Taylor & Francis Group, LLC.
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    Hydrological effects of land use /land cover changes on stream flow at Gilgel Abay River Basin, Upper Blue Nile, Ethiopia
    (CAFET INNOVA Technical Society 1-2-18/103, Mohini Mansion, Gagan Mahal Road, Domalguda, Hyderabad 500029, 2016) Mulu, A.; Dwarakish, G.S.
    Water is the most important resource for the survival of living things and it is the most essential resource associated with land use/ land cover (LU/LC) changes. Therefore, it is very important to make evaluations of the expected impact on the hydrology and water resources due to expected changes. The main objective of this study is to assess the hydrological effect of land use/ land cover changes on stream flow at GilgelAbay river basin using Precipitation Runoff Modeling System (PRMS) model. System inputs are daily time-series values of precipitation, minimum and maximum air temperature, and parameter files which are generated from GIS Weasel. To identify effect of changes in LU/LC, vegetation type and vegetation density on stream flow, LU/LC, vegetation type and vegetation density data from 1990-2000 and 2001-2010 years were considered. This different period LU/LC, vegetation type and vegetation density with soil data and DEM were given to GIS Weasel to generate different parameters for PRMS model. These generated parameters together with time series data (daily minimum and maximum air temperature, daily precipitation and daily stream flow) feed to PRMS model to simulate stream flow for the years 1993-2000 and 2001-2008. From the time series data, climate changes (daily maximum and minimum temperature and daily precipitations) were kept the same as baseline period (1993-2000). The stream flow of 2001-2008 compared with baseline period (1993-2000) and the effect of LU/LC, vegetation type and vegetation density was identified using calibrated and simulated PRMS model. Hence, as LU/LC, vegetation type and vegetation density changed from 1993-2000 period to 2001-2010 period, stream flow increased from 7.8% (128.4 Mm3) to 25.3% (432 Mm3) and ET decreased from 4.2% (75 Mm3) to 20% (524 Mm3) from baseline period. For the whole simulation periods (2001-2008) stream flow increased by 10.9% (784 Mm3), but ET decreased 6.7% (43 Mm3) related to baseline periods. © 2016 CAFET-INNOVA TECHNICAL SOCIETY. All rights reserved.