Faculty Publications
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Item Natural and anthropogenic factors controlling the dissolved organic carbon concentrations and fluxes in a large tropical river, India(2006) Balakrishna, K.; Kumar, I.A.; Srinikethan, G.; Mugeraya, G.Carbon studies in tropical rivers have gained significance since it was realized that a significant chunk of anthropogenic CO2 emitted into the atmosphere returns to the biosphere, that is eventually transported by the river and locked up in coastal sediments for a few thousand years. Carbon studies are also significant because dissolved organic carbon (DOC) is known to complex the toxic trace metals in the river and carry them in the dissolved form. For the first time, this work has made an attempt to study the variations in DOC concentrations in space and time for a period of 19 months, and estimate their fluxes in the largest peninsular Indian river, the Godavari at Rajahmundry. Anthropogenic influence on DOC concentrations possibly from the number of bathing ghats along the banks and domestic sewage discharge into the river are evident during the pre-monsoon of 2004 and 2005. The rise in DOC concentrations at the onset of monsoon could be due to the contributions from flood plains and soils from the river catchment. Spatial variations highlighted that the DOC concentrations in the river are affected more by the anthropogenic discharges in the downstream than in the upstream. The discharge weighted DOC concentrations in the Godavari river is 3-12 times lower than Ganga-Brahmaputra, Indus and major Chinese rivers. The total carbon fluxes from the Godavari into the Bay of Bengal is insignificant (0.5%) compared to the total carbon discharges by major rivers of the world into oceans. © Springer Science+Business Media, Inc. 2006.Item Evaluation of water quality index for drinking purposes for river Netravathi, Mangalore, South India(2008) Avvannavar, S.M.; Shrihari, S.An attempt has been made to develop water quality index (WQI), using six water quality parameters Dissolved oxygen (DO), Biochemical oxygen Demand (BOD), Most Probable Number (MPN), Turbidity, Total Dissolved Solids (TDS) and pH measured at eight different stations along the river basin. Rating curves were drawn based on the tolerance limits of inland waters and health point of view. Bhargava WQI method and Harmonic Mean WQI method were used to find overall WQI along the stretch of the river basin. Five point rating scale was used to classify water quality in each of the study areas. It was found that the water quality of Netravathi varied from Excellent to Marginal range by Bhargava WQI method and Excellent to Poor range by Harmonic Mean WQI method. It was observed that the impact of human activity was severe on most of the parameters. The MPN values exceeded the tolerable limits at almost all the stations. It was observed that the main cause of deterioration in water quality was due to the lack of proper sanitation, unprotected river sites and high anthropogenic activities. © Springer Science+Business Media B.V. 2007.Item Conjunctive use in India's Varada River Basin(American Water Works Association cs-journals@wiley.com, 2009) Ramesh, H.; Mahesha, A.The use of groundwater in conjunction with surface water resources has gained prominence in regions experiencing scarce or uneven distribution of water. In the Varada River Basin in Karnataka, India, for example, an optimization model was developed for the conjunctive use of surface water and groundwater resources because of the increasing demand on agricultural and domestic sectors of this area's water supply. Monsoon rains, which occur only six months a year, predominantly control the basin's agricultural activities. However, the area has an immense need for efficient use of available water resources during the rest of the year. The model, based on linear programming, optimizes the allocation of groundwater and surface water subject to hydraulic and stream flow constraints. The model incorporates policy scenarios that add to the sustainability of the system. The developed conjunctive-use model is simple but effective in computing the optimal use of the Varada basin's water resources.Item Effect of climate change on Netravathi riverflow(2010) Shetkar, R.V.; Mahesha, A.The adequacy of freshwater resources for future is difficult to assess due to complex and rapidly changing environmental and social parameters. There is uncertainty with respect to the prediction of climate change and its effect on planning and management of water resources. Higher temperature and reduced precipitation would lead to larger deficiencies in the supply and demand for water. This might cause deterioration in the quality of freshwater adding strain on the already fragile balance between supply and demand. Although the effect of climate change on water resources is uncertain and site specific, the perception is that it will result into increased extreme events and hence increased risk of flooding and droughts. This paper aims at assessing the trends of temperature, precipitation and river flow for the Netravathi river, a tropical river of south India. The river water utilization at present is less than 1% of the average annual flow. The river flow is neither controlled nor altered due to manmade structures hence may be considered as natural flow. From the analysis, it is important to note that the temperature is rising and there is declining trend in precipitation and stream flow during the study period of 30 years (1971 to 2001). Also, the low flow frequency analysis shows an upward trend. Similar analyses carried out for the number of days of flow peaks above a threshold value indicate that the high flow frequency trend is declining and the magnitude of these high flow events is also decreasing. The outcome of the present study indicates a definitive, decreasing trend in the river flow due to climate change and a forecasting mechanism may be essential in the future for the sustainable development of the available water resources. © 2010 CAFET-INNOVA TECHNICAL SOCIETY. All rights reserved.Item On numerical modelling of waves, currents and sediment movement around Gurupur-Netravathi river mouth(2010) Radheshyam, B.; Rao, S.; Shirlal, K.G.This paper presents an overview of the investigations that were carried out to understand the coastal process along Bengre and Ullal at the Gurupur-Netravathi River mouth in the west coast of India. This river inlet was facing problems of migration and siltation since several decades and therefore two rubble mound breakwaters were constructed during the year 1994 as an intervention to maintain the inlet mouth. After the construction of these river training jetties, the inlet was stabilized, but severe erosion has been taking place along the Ullal spit on the south side of southern breakwater, since 1996 and heavy accretion on the North of Northern Breakwater along Bengre spit, which is now almost stabilized. This study has been undertaken to understand the hydrodynamics along the beaches adjoining the river mouth. For the present study, various field data was collected for the post monsoon season of 2006. The hydrodynamic (HD), Parabolic mild slope (PMS) and Sediment transport (ST) modules of MIKE-21 software were used to understand the hydrodynamics of the study area. Before the model was made use, it was first validated by using field data to understand the hydrodynamics of the area. Since the field data is of limited duration, data collected from the NMPT wave buoy for an entire year was used for the model simulation. From the studies it was confirmed that current direction and sediment movement follow a similar pattern in monsoon and pre-monsoon and a different pattern during post-monsoon. It is observed that the main cause of erosion is due to direct action of waves on the adjoining beaches of the coast and the beaches in the study area are generally in dynamic equilibrium with a small amount of erosion at Ullal. © 2010 CAFET-INNOVA TECHNICAL SOCIETY. All rights reserved.Item Global water quality indices for river Gurpur, Karnataka State, India(2010) Rajagopal, B.; Shrihari, S.; Dwarakish, G.S.Three water quality indices viz. Drinking Water Quality Index (DWQI), Health Water Quality Index (HWQI) and Acceptability Water Quality Index (AWQI) were developed by United Nations Environment Programme (UNEP) under the Global Environment Monitoring System (GEMS)/Water for global comparison of quality of water sources. In this paper these three global water quality indices were determined for River Gurpur, in Karnataka state of India. Gurpur is one of the important west flowing rivers of India and is the source for industrial needs of fast developing Mangalore city. River water samples were collected from Gurpur River at Gurpur Bridge on National Highway -13 near Mangalore monthly from November 2006 to October 2007. The samples were analyzed for sixteen physico-chemical and bacteriological parameters. The global water quality indices determined for river Gurpur can be designated as 'Fair' during the study period. The seasonal variation in global water quality indices ranged from 'Marginal' to 'Excellent'. © 2010 CAFET-INNOVA TECHNICAL SOCIETY. All rights reserved.Item Tropical, Seasonal River Basin Development: Hydrogeological Analysis(2011) Shetkar, R.V.; Mahesha, A.This study presents a hydrogeological analysis of a humid tropical, seasonal river in the context of climate change, increasing demand for water, and uneven distribution of rainfall. We investigate the Netravathi basin, a tropical river basin of south India. The climate change effect on the basin was evident in terms of increasing trend in temperature by about 0.7°C/100 years and decreasing trend in the river flow during the monsoon by about 0.8% of average annual flow per year using the Mann-Kendall trend test. Even though rainfall was found to be decreasing, no significant trend could be established. From the trend analysis of the river flow, it was found that there is an overall declining trend with longer scarcity periods. In addition, the trends of magnitude and frequency of high flows are declining. Even though the region receives an average annual rainfall of about 3,930 mm, it has nonuniform distribution with most of the rainfall confining to a few months of a year. In view of this, the region suffers from a prolonged dry period during February to May. The projected domestic water demand of the region for the next 25 years is estimated to be increasing from the present 0.09 mm3 to 0.25 mm3 per day because of rapid urbanization and industrialization. The purpose of this investigation is to highlight the effects of climate change and uneven distribution of rainfall in the river basin. This may assist in proper planning of the basin through strategies such as river water harvesting, which is investigated in the companion paper. Because the Netravathi River is a seasonal and tidal river, and saltwater intrusion along the river during the summer months is affecting the development of the basin. It was found that the river water is affected up to distance of about 22,000 m from the Arabian sea and the wells on the banks of the river are found to be highly vulnerable to saltwater intrusion during the summer period (March to May). © 2011 American Society of Civil Engineers.Item Tropical, Seasonal River Basin Development through a Series of Vented Dams(2011) Shetkar, R.V.; Mahesha, A.Tropical rivers are predominantly seasonal in nature, and managing water resources during the deficit period is becoming more difficult because of the rapidly increasing demand for water. The present investigation focuses on harvesting Netravathi River water in the southern Indian peninsula through a series of vented dams with an estimated storage capacity of 102 Mm3 for use during the deficit period. A brief hydraulic design of a vented dam at a specific location is presented. The spacing and capacity of these reservoirs were worked out on the basis of the dam height and the river characteristics. The proposed vented dams are seasonal dams, and the closure of the vents will be decided on the flow available (i.e., 95% dependable flow), the storage capacity, and the minimum water release required for the downstream ecosystem. The appropriate time to start storing water in the vented dams was estimated to be in the month of November, and the entire process of storing water in the vented dams may last for about 41 days. An operational protocol for the storing process is presented. The investigations of aquifer parameters were performed by using electrical resistivity, pumping, and soil tests. The results indicated that the aquifer is shallow, unconfined in nature, and had a depth ranging from 18 to 30 m and hydraulic conductivity ranging from 62.6 to 406 m/day. A multiple regression model developed to assess the groundwater recharge in the adjoining well fields indicated that water table fluctuations may be 30% of reservoir level fluctuations. Because the river is also tidal in nature, a saltwater exclusion dam is proposed at the lower reaches of the river to prevent the entry of saltwater along the river during the summer period. © 2011 American Society of Civil Engineers.Item Neotectonic evolution of Coastal Rivers of Mangalore, Karavali Karnataka, India(2011) Ravindra, B.M.; Venkat Reddy, D.The geomorphic evolution of Mangalore is intimately influenced by Neo-tectonic activities that affected the West Coast and peninsular India that led to the upliftment of Sahyadri Range. Mangalore pediplain has preserved signatures of (1) An older cycle of River system that existed prior to the rise of Sahyadri and (2) Several phases of migration paths of the West flowing Sahyadri Rivers, reflecting geomorphic changes in the pediplain in response to the tectonic strains generated during the rise of the Sahyadri range and northward drift of the Indian subcontinent. The compressional stress derived from the phenomenon of Sea floor spreading is manifested in the Karavali pediplain, in the form of EW and NNW intersecting transform faults that activate periodically and trigger microseismic disturbances severe sea erosions or landslides under adverse hydrological conditions. Similarly under the regime of compressional stress, the Mangalore pediplain evinces evidences of sequential development of anticlinal upwarps that broke into horsts and grabens separated by escarpments. The Holocene fluvial evolution of Mangalore consisted of migration of the two Rivers in opposite directions with progressive passage of time in the Holocene. Fluvial geomorphology of Mangalore has also preserved evidences that substantiate shifting of trans-peninsular Mulki - Pulicat Ridge Axis from its original position northwards. The ongoing structural disturbances and micro-seismic and allied recent neo-tectonic activities imply that the processes responsible for the creation of the Sahyadri range have not died down yet and are very much in attendance even today. © 2011 CAFET-INNOVA TECHNICAL SOCIETY. All rights reserved.