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Über dieses Buch

This book offers a unique collection of inter- and multidisciplinary studies on river systems. Rivers have been the prime source of sustenance since the advent of civilization and river systems often form the basis for agriculture, transport, water, and land for domestic, commercial, and industrial activities, fostering economic prosperity. A river basin is a basic geographical and climatological unit within which the vagaries of natural processes act and manifest themselves at different spatio-temporal scales. Even if compared side-by-side, no two river basins respond to natural processes in the same way and thus, it has long been recognized that each river basin is unique. Hence, any developmental activity or conservation effort has to be designed and implemented to match each unique river basin. With the burgeoning population and increasing dependency on natural resources, understanding and maintaining river systems has become increasingly important. This book provides a varied reference work on and unprecedented guidelines for conducting and implementing research on river basins, and for managing their ecological development.

Inhaltsverzeichnis

Frontmatter

Land Use Dynamics and Environmental Management of River Basins with Emphasis on Deltaic Ecosystems: Need for Integrated Study Based Development and Nourishment Programs and Institutionalizing the Management Strategies

The deltaic systems maintain a delicate equilibrium with the litho, hydro, bio and atmospheric processes and provide sustenance to the biosphere. Located at the receptive end, the lower reaches of the river basins

a la

deltas are fragile ecosystems and are susceptible to the changes in the upstream regions. These ecosystems survive at the mercy of processes not only in their vicinity, but also the processes that act at the catchments of the river systems. With the growing population and economic development, they are under multiple pressures emanating from anthropogenic activities. Unlike the natural processes, the anthropogenic interventions with the deltaic ecosystems are highly complex and varied. These range from modification of physical surface characteristics, introduction of physical, chemical and biological pollutants from point and non-point sources, in the name of developmental activities including but not limited to urbanization, commercial, industrial, recreational and agricultural endeavors, culture, geopolitics, racism, quality of life, economic might, and mismanagement and unsustainable rates of exploitation of natural resources. All these could be comprehensively termed into conversion of natural land cover into land use. In this paper, an attempt is made to enlist the human endeavors that convert the natural land cover into anthropogenic land use and resultant adverse impacts and irreversible reactions. These are then summed up into a scheme of comprehensive study for integrated management. A plea is also made to institutionalize the management practices for effective implementation and sustainable development.

Mu. Ramkumar, K. Kumaraswamy, R. Mohanraj

Spatio-temporal Analysis of Rainfall Distribution and Variability in the Twentieth Century, Over the Cauvery Basin, South India

Knowledge on the spatial variability and temporal trends of mean rainfall is essential for efficient management of water resource and agriculture. We have analyzed the rainfall data of the Cauvery river basin, a larger river basin in Southern India which plays a significant role in agricultural development and consequently in the overall growth of Karnataka, Tamil Nadu, Pondicherry and some parts of Kerala. The analysis includes distribution, variability and trends in rainfall over the Cauvery basin during twentieth century (1901–2002). The impact of climate change on temporal and spatial patterns of rainfall over smaller spatial scales is clearly noticed in this analysis. It is also observed that the coefficient of variation shows significant fluctuations during the winter than other seasons. Long term changes in rainfall have been determined by. Significant decreasing trend in the winter rainfall and increasing trend in the post-monsoon season with insignificant levels have been inferred based on the Mann-Kendall rank statistics and linear trend. Overall, insignificant decrease in annual rainfall over the Cauvery river basin has observed during twentieth century.

Sawant Sushant, K. Balasubramani, K. Kumaraswamy

Selection of Suitable General Circulation Model Precipitation and Application of Bias Correction Methods: A Case Study from the Western Thailand

The General Circulation Models (GCMs) precipitations are generally characterized by the biases and low spatial resolution. These two are the major limiting factors for direct application of GCMs scenarios in the studies of climate change impact assessment. Based on 17 experiments over the two river basins of the western Thailand, Six GCMs were analyzed for their ability to simulate the magnitude and spatial variability of current precipitation. Monthly precipitation scenarios from six GCMs (17 experiments) are downloaded from the IPCC data centre. Three bias-correction techniques namely, scaling, empirical-gamma and gamma-gamma transformations were applied on a daily scale of 9 years (1991–1999) to improve the quality of the selected ECHAM4/OPYC SRES A2 and B2 precipitation for the Mae Ping and Mae Klong River Basins in the Western Thailand. All the three bias correction methods have been compared with observed precipitation based on statistical parameters. Gamma-gamma transformation method is found to be effective in correcting the rainfall frequency and intensity simultaneously as compared to other methods. The bias corrected daily precipitation is useful in studies related to climate change and water resources management at basin level.

Devesh Sharma

Hydrological Regime Responses to Climate Change for the 2020s and 2050s Periods in the Elbow River Watershed in Southern Alberta, Canada

The Elbow River watershed, located in southern Alberta, drains approximately 1,235 km

2

area, and supplies the Glenmore Reservoir that provides water to nearly half of Calgary, a fast growing city of 1.1 million inhabitants. The watershed is characterized by a complex hydrological regime and is typical of snow dominated basins, with a spring freshet driven by snow melt and rainfall in late spring and early summer. This context creates favorable conditions for springtime flooding, which resulted in extensive damage in 2005 and 2013. Therefore, understanding how future climate changes might influence the watershed hydrological regime is critical. This research was conducted to investigate the hydrological regime responses of the watershed to climate change for the period of 2020s (2011–2040) and 2050s (2041–2070), relative to 1961–1990. The physically-based, distributed MIKE SHE/MIKE 11 model was used to simulate hydrological processes based on a warmer and drier (CCSRNIES A1FI) climate scenario. Results reveal that the average annual overland flow, baseflow, and river flow will decrease over the next 60 years and that this decrease combined with a drastic increase in evapotranspiration might increase water scarcity. Peak flows will increase in the winter and early-mid spring while decreasing in the summer and early fall. This enhances the risk of flooding in the spring, especially in the month of April which exhibits a significant increase in rainfall coinciding with the highest increase in spring freshet.

Babak Farjad, Anil Gupta, Danielle J. Marceau

Climate Effects on Recharge and Evolution of Natural Water Resources in middle-latitude Watersheds Under Arid Climate

This paper analyzes the physico-chemical characteristics of natural waters in middle-latitude drainage systems of central Asia, including the climatic, lithological and geomorphological conditions in which water flows and resides. This analysis allowed the identification of the geological evolution and recharge mechanism of the water resources in an arid environment. The studied waters at various sites are different in mineralization but similar to the majority of large rivers on earth, which are typically alkaline. However, no Cl-dominated water type occurs in the study area, indicating that these natural waters are still at an early stage of evolution. The regolith and geomorphological parameters controlling ground-surface temperature may play a large role in rock weathering regime and so in the geological evolution of water. Three main morphological and hydrological units are reflected in water physico-chemistry: the montane areas (recharge area) with silicate and carbonate weathering, the piedmonts and sedimentary platform (runoff area) with carbonate weathering, and the desert plains (discharge area) with evaporite dissolution. Climate influences the salinization of natural waters substantially. Direct recharge from seasonal snow and meltwater and infiltration of rainfall into the ground are thought to be significant recharge processes for natural waters in the study area, while recharge from potential deep groundwater may be much less important. The chemistry of lakes is generally consistent with those of large lakes in the world, but the enrichment of the ions in the lakes has been caused mainly by evaporation, rather than through the quality of the recharged water.

Bingqi Zhu, Jingjie Yu, Patrick Rioual, Yan Gao, Yichi Zhang, Heigang Xiong

Factors Influencing the Runoff Trend in a Medium Sized River Basin in the Western Ghats, India

The present study examines the trends in the annual runoff of a tropical river basin Bharathapuzha, a medium sized river in southern India under the influences of anthropogenic pressures and climate change. The examination of the temporal trends in the rainfall, temperature and river runoff was done using historical datasets. It was supplemented with the data on the land use/land cover (LU/LC) change in the basin based on the LANDSAT TM data. By using a multiple regression model, the influential factors determining the river discharge were identified. The results show that while the rainfall influences the runoff positively, new water bodies, dams and other diversions in the fluvial setup in the basin influence the river runoff negatively.

P. P. Nikhil Raj, P. A. Azeez

Morphometric Analysis for Prioritization of Watersheds in the Mullayar River Basin, South India

The Mullayar River is one of the tributaries of the Periyar River, south India. Morphological features and linear and aerial morphometric parameters of the Mullayar River Basin (MRB), located in the Kerala State, India were studied with the help of Geographic Information System and utilizing the Survey of India (SOI) topographic sheets of 1:50,000 scale. The results show that this basin contains 5th order drainage network and drainage pattern mainly of sub-dendritic to dendritic type. It is observed that the drainage density is low indicative of highly permeable soil structure and thick vegetative cover. The circularity ratio value reveals that the basin is highly elongated and is covered by highly permeable homogenous geologic materials.

R. Jaganathan, K. Annaidasan, D. Surendran, P. Balakrishnan

Assessment of the Water Resource of the Yodo River Basin in Japan Using a Distributed Hydrological Model Coupled with WRF Model

The Yodo River basin provides water resource to the highly populated areas of Kinki, Japan. Similar to other river basins located elsewhere, the Yodo River basin is also vulnerable to negative impacts of climate change. Since accurate prediction of extreme events is essential for assessing the impact of climate change, any integrated monitoring and prediction system should be based on the hydrometeorological system. For this goal, dynamic downscaling of the meteorological data by using coupled mesoscale hydrometeorological modeling approach to simulate the local and regional effects on water resources of the basin, has been attempted. Coupled model consisting of WRF mesoscale meteorological model and distributed hydrological model, along with a simplified dam model, at high-resolution was used to simulate the response of the Yodo River basin to atmospheric forcings in one-way coupling mode. The distributed hydrological model is shown to be capable of simulating the basin hydrology of the Yodo River basin by replacing the atmospheric forcings from observation station data with the high-resolution gridded hydrometeorological variables from WRF mesoscale meteorological model.

K. L. Shrestha, A. Kondo

Remote Sensing—A Fast And Reliable Tool to Map the Morphodynamics of the River Systems for Environmental Management

River is a dynamic morphometric agent which shapes literally earth’s entire surface except the dry deserts and the ice-capped Polar Regions. The morphological variations in the river basins are under the influences of an ensemble of variables including, but not limited to, the precipitation, runoff, slope, soil, and many other processes including tectonics, sedimentation, oceanography and anthropogenic intervention. As the rivers provide sustenance to the fauna and flora including the human race, understanding the river systems is essential from the ecological and economic points of view. The river systems interact with and maintain a delicate equilibrium with the lithosphere–hydrosphere–atmosphere, which make understanding the fluvial dynamics a necessity. The ever-increasing pressures from the anthropogenic interventions, under the climate change scenarios make this task critical for sustainable management which in turn requires extensive data inputs on a spatio-temporal scale. However, the very dynamic nature of the river systems poses constraints on the data acquisition and subsequent analysis. In this paper, we attempt demonstrate the utility of remote sensing and GIS as tools for fast and reliable analysis of morphodynamics of rivers for environmental management.

V. Thirukumaran, Mu. Ramkumar

Spatio-temporal Analysis of Magnetic Mineral Content as a Tool to Understand the Morphodynamics and Evolutionary History of the Godavari Delta, India: Implications on the Environmental Management of Deltaic Coastal Zones

The fluvial delta acts as a unified system wherein the changes in one part of the system affect the other regions and create unique signatures of such events in terms of geomorphic and sediment textural, mineralogical, geochemical and other characteristics in the ensuing deposits. The spatio-temporal variations of the governing factors of the system introduce proportionate changes, which are normally inferred as sub-environments of a delta. An ability to understand the ongoing dynamics in the sub-environments through sensitive parameters of the sediments and developing a capability to interpret the ancient dynamics would be valuable for application of similar technique in other deltaic systems for environmental management. Magnetic mineral contents of the surface samples and vibracore stations collected from the Godavari delta, India were estimated and analyzed for their spatio-temporal variations together with geomorphologic and other characteristics. The magnetic mineral content showed a general increase from inland to coastline and is at its maximum along the river courses. It is concluded that the concentration of magnetic minerals is controlled by erosion and size sorting within a deltaic system and vary according to the spatio-temporal differences of energy conditions in time and space. As each sub-environment within a deltaic system has unique energy conditions, these primary differences reflect in the sediment characteristics and in the magnetic mineral content. Visualizing these differences on a spatio-temporal scale has helped in inferring paleoshorelines and paleochannels in the study area and reconstruct the evolutionary history of the Modern Godavari Delta. Collation of these inferences together with information on neotectonics, geomorphology and land use characteristics suggested that the Godavari delta faces multiple and multi-dimensional natural and anthropogenic environmental threats and urgent mitigation and environmental management programs need to be undertaken based on multi-disciplinary and comprehensive studies.

Mu. Ramkumar

GIS Based Quantitative Geomorphic Analysis of Fluvial System and Implications on the Effectiveness of River Basin Environmental Management

Rivers are sensitive to changes in tectonic deformation, and adjust themselves on different scales of time periods depending on the physical properties of the host rocks and climatic effects. The resultant changes are exhibited by the geomorphic indices and landform assemblages within a river basin. This paper presents the results of integrated quantitative geomorphic analysis conducted for understanding the prevalent tectonic activities in a medium sized drainage basin, the Thoppaiyar sub-basin, India. The major part of the study area is covered by gneisses and granites. The sub-basin is divided into fourteen fourth order micro basins (FOMBs) for quantitative geomorphic analysis. Prior to quantitative analysis, longitudinal river profile and channel morphology were studied. The channel morphology includes cross sections, width-to-depth ratio, entrenchment ratio, bank height ratio were measured during field investigation. Various geomorphic indices namely, the basin shape index (Bs), drainage basin asymmetry factor (Af), hypsometric integral (Hi), hypsometric curve (Hc), valley floor width-to-height ratio (Vf), transverse topographic symmetry (T) and stream length gradient index (SL) were derived using topographic maps and SRTM satellite data. The spatial distributions of these parameters were represented as thematic layers using. The results obtained from these indices were combined by ArcGIS 9.3 software to generate an index of relative active tectonics (I

RAT

) in the sub-basin. It indicated the prevalence of differences among the FOMBs and an overall relatively low tectonic activity in the Thoppaiyar sub-basin.

A. Venkatesan, A. Jothibasu, S. Anbazhagan

Spatio-Temporal Variations of Erosion-Deposition in the Brahmaputra River, Majuli—Kaziranga Sector, Assam: Implications on Flood Management and Flow Mitigation

Erosion-deposition activities of the Brahmaputra River channel within a stretch from Majuli to Kaziranga, Assam, India have been evaluated in the light of associated geomorphic and anthropogenic features. The results indicate that the mass failure, fluvial entrainment and sub aerial weathering and weakening play major roles over the depositional-erosional activities of the river channel. The mass failures result due to the heterogeneities of bank material. Shear failure of uneven nature and flowage (liquefaction) of the sediments are observed within the studied stretch of the Brahmaputra River channel. The transitory nature of channel configuration with time exhibited by node point generation and migration were also found to be associated with extensive lateral bank erosion processes, resulting in widening of the channel. Based on these observations, the critical areas of erosion-deposition were identified and accordingly, time-dependent flow and flood mitigation measures have to be undertaken.

P. Kotoky, D. Bezbaruah, J. N. Sarma

Mechanisms and Spatio-temporal Variations of Meandering and Erosion-Deposition Statistics of the Dhansiri River, Assam

The highly meandered Dhansiri River, a south bank tributary of the mighty Brahmaputra bears significant geomorphologic importance. Spanning the period 1914–2000, a stretch of the Dhansiri River channel from Dhansirimukh to Nowakota Kachari was studied with an objective to understand the erosion-deposition activities operating within the channel. Owing to its location on an alluvial plain, the river shows conspicuous migration characteristics. It has also imparted unique fluvial landscape in the study area. The river channel within the period under observation has migrated to the tune of 2.85 km towards south at Dhansirimukh in conjunction with the southward migration of the mighty Brahmaputra River channel. The study has revealed a total average annual erosion and deposition covering the entire period were 1.32 and 1.27 km

2

/year respectively. The total average rate of erosion and deposition per kilometer length of the river were 0.006375 and 0.00625 km

2

/km respectively. Increasing rate of erosion since the year 1914, comparatively higher erosion along the west bank than the right bank have also been observed. The areas around Butalikhowa, Golaghat and Kuruabahi have under gone severe erosion posing a threat to the population in the vicinity.

P. Kotoky, M. K. Dutta

Sand Mining, Channel Bar Dynamics and Sediment Textural Properties of the Kaveri River, South India: Implications on Flooding Hazard and Sustainability of the Natural Fluvial System

The Kaveri River, the fourth largest river in India, undergoes the onslaught of urbanization and extensive construction activities within, along and adjoining its channel. In addition to its dwindling natural flow due to the failing monsoonal supply, and constructions of major, medium and minor dams, the extensive mining of sand from its channel bed causes severe stress on its natural fluvial processes. Reduction of carrying capacity of the channel, extensive vertical accretion of sediments within the channel, development of channel-in-channel physiography, and alteration of stream configuration and textural parameters of the stream bed sediments have contributed towards deterioration of the environmental integrity of this important river and exacerbated the flood hazard in the adjoining regions. This paper is an attempt to document the deterioration of natural fluvial dynamics due to the anthropogenic intervention and lack of required data for proper understanding for environmental management and sustenance of the fluvial system. The textural and geomorphic characteristics and the mechanism of mid-channel bar formation and stabilization documented through this study suggest that the whole of the river channel of the Kaveri River behaves like a braided bar/flood plain, which means the prevalence of slow abandonment of the fluvial processes, that could only be observed in the flood plain region of mature and or old stage of a river and/or in the event of shifting of channel course. Occurrence of such characteristics at the upper deltaic region and the observation that the channel area gets converted into mid-channel bars (in terms of textural-geomorphic traits), at a rate of 1.08 km

2

/year warrant immediate measures for the restoration of natural fluvial processes.

Mu. Ramkumar, K. Kumaraswamy, R. Arthur James, M. Suresh, T. Sugantha, L. Jayaraj, A. Mathiyalagan, M. Saraswathi, J. Shyamala

Hydro-Geomorphology and Hydrogeology of the Pennar River Basin, India: Implications on Basin Scale Surface and Ground Water Resource Management

The Pennar river basin covering an area about 58,479 km

2

has been studied to delineate the landforms, structural features, and hydro-geomorphic units, ground water level variations, fluctuations and recharge. The landforms are classified into denudational, fluvio-denudational, fluvial, aeolian and coastal categories. Hydro-geomorphologically, the deltaic plains and fluvial plains are grouped under excellent ground water potential, irrigated plains other than fluvial and deltaic plains as good ground water potential, wash plains, valley fills, piedmont plains and creep built plains as fair ground water potential, shallow and moderately weathered pediment plains as poor ground water potential and slope zones of hilly terrain as run-off zones. The Pennar Basin consists of Archean unclassified granitic terrain in the western and southern parts of the basin followed by Proterozoic formations consisting of shales, quartzites and limestone in the central parts of the basin and Quaternary and Holocene sediments in the eastern side. Hydro-geologically the ground water potential is high in the weathered, fissured, fractured and faulted zones of the basin. The ground water potential in the Archean granitic terrain is very poor. The ground water potential in Quaternary and Recent sedimentary formations is good. Thus, the study of land forms in terms of their causative agents, associated lithological and hydrogeological characteristics and categorizing them into hydro-geomorphic units helps to evaluate and manage water resources efficiently.

M. Sambasiva Rao, G. Rambabu

Geochemical Perspectives on River Water of the Tropical Basins, Southwestern India

The Southwestern part of Peninsular India is one among the shield terrains experiencing extreme geological, geomorphological and climatic gradients. Many small rivers originate in the western slope of Western Ghats and flow towards the Arabian Sea. The moisture from the Arabian Sea carried by the southwesterly winds forms the primary source of water for these rivers. These west flowing rivers exhibit characteristic water chemistry distinct from that of the east flowing rivers and the rivers draining the Deccan traps. The lithological heterogeneity and the intensity of weathering have significant effect on the river water as observed by the difference in water chemistry between the Deccan, East flowing and West flowing rivers. The geomorphological settings of the Western Ghats (which brings-in the rainfall over its western slope) induce higher surface runoff which has significant effect on the weathering process and thus, on the water chemistry. However, the slope of the terrain has minimal effect on the chemistry of water in this region. The weathering of sedimentary formations in the plains leads to elevated fluxes of silica and radiogenic strontium. The weathering of bedrock forms the main source of trace elements to the river water in this region. The abundance of trace elements in monsoon dominated terrain is controlled primarily by the discharge. However, the secondary processes namely, redox reactions and oxidative scavenging of surface reactive metals by the oxyhydroxides of Fe and Mn appears to have significant role in determining the geochemical abundance. Unlike the tropical river basins of Africa and South America where the organic carbon complexation plays a vital role in dissolved metal abundance, in the rivers of Southwestern India, the control of organic complexation on the dissolved metal chemistry varies widely between rivers. This could be due to variable abundance of labile fraction of organic carbon in these rivers. The secondary geochemical processes lead to the enrichment of metals in sedimentary phase. However, the enrichments of these metals are within the permissible limits. From the pollution point of view, the metal contaminant studies in these river basins need to consider the rigorous fluvial geochemical redistribution of metals between particulate and dissolved phases to minimize the erroneous attribution of metal sources. The metal isotope tracing of pollution sources could be useful for accurate determination of pollution sources.

G. P. Gurumurthy, M. Tripti

Hydrogeochemical Drivers and Processes Controlling Solute Chemistry of Two Mountain River Basins of Contrasting Climates in the Southern Western Ghats, India

Water samples were collected from two mountain rivers of contrasting climates, viz., humid, Muthirapuzha River Basin (MRB) and semi-arid, Pambar River Basin (PRB) during monsoon (MON), post-monsoon (POM) and pre-monsoon (PRM) seasons, and were analyzed to understand the spatio-temporal variability as well as the sources and processes controlling hydrogeochemistry. In MRB and PRB, Ca

2+

and Mg

2+

dominate the cations, while Cl

dominates the anions in MRB and HCO

3

dominates the anions in PRB. PRB shows an elevated level of ionic abundance and higher degree of mineralization, due to multiple factors such as semi-aridity, discharge dominated by groundwater, lithological variations and the influences of carbonates and soil evaporites. However, K

+

, Cl

and H

4

SiO

4

are relatively higher in MRB, implying significance of both anthropogenic activities and intense silicate weathering. The Ca

2+

+ Mg

2+

/HCO

3

ratios in MRB are also relatively larger than PRB, suggesting high intensity of anthropogenic influences in MRB. Downstream variation of hydrogeochemistry implies a general decreasing trend in MRB, which is attributed to dilution due to high discharge, whereas hydrogeochemistry of PRB shows an increasing downstream trend, by which, the significance of semi-arid climate of the downstream tracts of the basin is implied. Both MRB and PRB show temporal variability in hydrogeochemical attributes implying the role of monsoon rainfall determining stream water composition. The Na

+

-normalized Ca

2+

versus Na

+

-normalized HCO

3

plots suggest the control exercised by mixing between silicate and carbonate end members in both the basins. However, in PRB, dissolution of soil evaporites during MON and POM is evident by relatively lower Ca

2+

/Na

+

ratios. The Ca

2+

+ Mg

2+

/Na

+

+ K

+

ratios in MRB and PRB during MON (mean = 1.96 and 2.23 in MRB and PRB respectively), POM (mean = 3.29 and 2.41) and PRM (mean = 5.74 and 4.40) also suggest sources other than silicate weathering. Relative enrichment of Cl

(with respect to Na

+

) indicates multiple sources for Cl

(i.e., anthropogenic as well as atmospheric). Even though there are significant differences in water types between MRB and PRB, most of the waters of both the basins are considered to be “transitional”. Relatively higher

p

CO

2

in stream waters (compared to atmosphere) is observed and the phenomenon is attributed to the influent nature of the stream discharge (i.e., contributed by groundwater which is significantly enriched in CO

2

) and the slower rate of re-equilibration (i.e., solubility vs. release of CO

2

) with atmosphere. Hence, evidently the hydrogeochemical composition of MRB and PRB is jointly controlled by weathering of silicate and carbonate minerals as well as anthropogenic activities and is influenced by climatic seasonality. The spatio-temporal variability of hydrogeochemical attributes of MRB and PRB is mainly due to the variations in climate, lithology, hydrologic pathways and degree of various anthropogenic activities.

Jobin Thomas, Sabu Joseph, K. P. Thrivikramji

Assessment of Water Availability in Chennai Basin under Present and Future Climate Scenarios

Climate change may significantly impact the hydrological processes of a watershed system and lead to water scarcity or increased flooding. It may also cause serious problems to humans including loss of biodiversity and risks to the ecosystem. Quantifying and understanding the hydrological response to a changing climate are necessary for water resource management and formulation of adaptive strategies. In this study, changes in water balance components of the Chennai Basin under present and future climate scenarios had been assessed using Soil and Water Assessment Tool (SWAT). High resolution climate outputs (0.25° × 0.25°) from PRECIS regional climate model for present (1961–1990 BL), mid-century (2041–2070 MC) and end-century (2071–2098 EC) under the IPCC SRES A1B emission scenario were used to assess the hydrological changes in the Chennai Basin. The study had determined the present and future water availability in space and time without incorporating any man-made changes like dams, diversions etc. The results indicated a decrease of precipitation in future scenarios as a result decrease of total water yield and ground water flow component in mid-century and end-century. Though both of these scenarios showed decreases in water balance components, the decrease in end-century would be lesser than the mid-century. In the season-wise analysis, the ET would be increased in winter and post monsoon seasons. Water yield had shown decrease in all the seasons of the mid-century scenario and increase during the EC winter and summer seasons.

J. Anushiya, A. Ramachandran

A Review on the Riverine Carbon Sources, Fluxes and Perturbations

Carbon is transported from the land to the oceans via rivers and groundwater. The transfer of organic matter from the land to the oceans via fluvial systems is a key link in the global carbon cycle. Rivers also provide a key link in the geological scale carbon cycle. Nevertheless, an appreciation of their roles is yet to be made. Even when their roles are included, data are drawn only from selected large rivers, often neglecting the small mountainous rivers. Previous studies have demonstrated that, the tropic rivers, especially located in Asian region play crucial role in regulating the global carbon budgets. Superimposed on the natural sources and fluxes, the anthropogenically-induced fluxes, primarily emanating from reduced sediment and discharge (as a result of constructions of dams and reservoirs), and enhanced detrital organic matter (as a result of increased surface flow due to land use change) introduce perturbations.

Sumi Handique

GIS-Based Modified SINTACS Model for Assessing Groundwater Vulnerability to Pollution in Vellore District (Part of Palar River Basin), Tamil Nadu, India

Though traditionally considered to be less vulnerable to pollution than surface water, the groundwater resources face multiple sources of contamination during the recent times. In this paper, we employed modified SINTACS (Normal and Severe) model over a region known for thick clusters of leather processing industries, and dependence of domestic and industrial water supply on groundwater resources. Several parameters including, depth to groundwater, effective infiltration, unsaturated zone attenuation capacity, soil attenuation capacity, hydrogeological characteristics of the aquifer, hydraulic conductivity and topographical slope were spatially evaluated and subjected to overlay analysis after assigning appropriate ratings and weights to identify the different vulnerability levels in the study area. The results show that, the groundwater vulnerability to pollution is very high on the eastern part of the study area, under the influences of gentle slope, alluvial soil and higher permeability. In addition, scattered occurrences of vulnerable zones aligned along the river course are also identified.

K. Rutharvel Murthy, S. Dhanakumar, P. Sundararaj, R. Mohanraj, K. Kumaraswamy

Natural and Anthropogenic Determinants of Freshwater Ecosystem Deterioration: An Environmental Forensic Study of the Langat River Basin, Malaysia

Freshwater ecosystems face numerous threats that challenge the local authorities’ ability on tackling down the water security (quantity and quality) issues and their management. The quality of surface water is an essential component of the natural environment and is considered as the main factor for controlling ecosystem health and potential hazard to the surrounding environment. The Langat River Basin in Selangor, Malaysia is exposed to natural and anthropogenic activities. A forensic investigation via the use of geostatistical and geochemical approaches and different standard criteria revealed two sources controlling the evolution of Langat River Basin water chemistry: (i) anthropogenic (agricultural and industrial activities) and (ii) natural processes (seawater intrusion and geological weathering). In addition, the suitability of river water for various purposes was determined based on the application of selected indicators and indices. The findings serve as an essential platform for the protection of water resources.

Ahmad Zaharin Aris, Wan Ying Lim, Ley Juen Looi

Phosphorous Fractionation in Surface Sediments of the Cauvery Delta Region, Southeast India

Phosphorus is both a nutrient and a key factor responsible for eutrophication of freshwater ecosystem. Knowledge on geochemical forms of phosphorous is one among the proxies to monitor the quality of an aquatic ecosystem. Channel-bed sediment samples were collected from the Cauvery River in delta region, fractionated into five namely, exchangeable P, Fe-P, Al-P, Ca-P and Residual-P and were studied. Total phosphorous concentration of ranged between 360 and 1,070 mg/kg. The mean values of P fractions are: HCl-P (68 %), NaOH-P (12 %) and NH

4

Cl-P (8 %). Among the phosphorous fractions studied, HCl extractable P recorded as a dominating chemical form. It implies P had a preferential association with Ca. The pH of the river sediments varied from 7.37 to 8.69 implying alkaline nature. Total Organic Carbon (TOC) and Organic Matter (OM) of the sediments showed ranges of 0.04–1.0 % and 0.14–3.45 %, respectively. Total Nitrogen (TN) of the sediment samples was in the range between 0.08 and 0.20 %. The C/P and N/P ratios ranged 1.65–78.67 and 1.33–6.69, respectively.

S. Dhanakumar, K. Rutharvel Murthy, R. Mohanraj, K. Kumaraswamy, S. Pattabhi

Water Pollution in the Vicinity of Stanley Reservoir by Point and Non-point Sources, Cauvery Basin, India

Surface and groundwater samples were collected from the Stanley reservoir and its vicinity for two seasons (pre-monsoon and monsoon) and analyzed for physico-chemical characteristics. Variations between surface and groundwater and between pre monsoon and monsoon samples could be discerned through the studied parameters, signifying the roles of rainfall, and solute processes. Superimposed on these natural phenomena, elevated levels of chemical oxygen demand and biological oxygen demand indicative of high organic load in surface water and higher Cl and F contents in surface and groundwater as a result of anthropogenic inputs were observed. These results signify that, despite the dilutions from rainfall and potential percolation from large reservoir, the anthropogenic perturbations, mainly emanating from point and non-point sources contaminate the surface and groundwater resources.

R. Jayakumar, S. Dhanakumar, K. Kalaiselvi, M. Palanivel

Environmental Integrity of the Tamiraparani River Basin, South India

Monitoring the surface run-off and physicochemical parameters of a river on a regular basis provides valuable information on the eco-hydrologic conditions of the river basin. The resultant data provide valuable insights into spatial and temporal variation on water quality, considered as a measure of the health of a river. The physicochemical characteristics of any aquatic ecosystem and the nature and distribution of its biota are directly related to and influenced by each other and controlled by a multiplicity of natural regulatory mechanisms. The River Tamiraparani, a perennial river in southern India was studied for comprehensive environmental issues. The major ion chemistry and nutrients of the studied samples show seasonal and spatial variations, under the predominant influence of geogenic (natural weathering) and to certain extent, lesser influence of anthropogenic sources. Application of various geochemical indices (SAR, RSC, PI, PS and Na %) and plots revealed that, a majority of the samples (90 %) are within the permissible limits of the domestic and agricultural usages. The occurrences of organochlorine compounds in the studied samples suggest influx from agricultural activities.

R. Arthur James, R. Purvaja, R. Ramesh

Changes in Water Quality Characteristics and Pollutant Sources Along a Major River Basin in Canada

Temporal and spatial variations of water quality along the Bow River (Alberta, Canada) were investigated using monthly water quality data (chloride, sulphate, nitrate, sodium, and conductivity) collected from 2004 to 2011. Non-point and point (notably three wastewater treatment plants) pollutant loads were characterized along the river. The river was divided into three reaches, namely, the Upper river reach, the Calgary reach, and the Downstream river reach, based on the distribution of point pollutant sources and geographic conditions. A mass balance approach and statistical analyses were employed to analyze water quality. The results demonstrated that the point sources, Calgary’s three wastewater treatment plants (WWTPs), are largely responsible for the observed spatial and temporal trends in the investigated quality parameters. However, the contribution of non-point sources appears to vary along the river, which might be related to the flow pathways taken by non-point pollutants discharging into the river and the geochemical characteristics of the groundwater within the alluvial aquifer that is hydraulically connected to the river. Apart from the identified point and non-point sources, the effects of other processes such as biological reactions need to be further ascertained and quantified for a better assessment of pollutant loads, in particular nutrients. Further understanding of these issues will allow a more accurate quantification of pollutant loads and consequently, better knowledge for formulating reliable water quality management strategies.

Jianxun He, M. Cathryn Ryan, Caterina Valeo

Assessment of Groundwater Quality in the Amaravathi River Basin, South India

Sustainable water management in a river basin requires knowledge on the water availability in the basin and current and future demands. The problems of water quality have become more important than the quantity and any sustainable management program must take into account the availability and suitability of water resources for various purposes. Being a solvent and depleted in major and trace ions, water is susceptible to contamination by a variety of sources including, but not limited to, rocks, soil, effluents, and sewage with which it comes into contact. In this study, attempt is made to evaluate the status of ground water quality and its effect on human health, irrigation and environment and domestic purposes. Water samples were collected from 53 locations distributed in Karur, Erode and Thiruppur districts in the year 2011 during both pre-monsoon and post-monsoon seasons. Water quality parameters namely, pH, Total Dissolved Solids (TDS), Total Hardness (TH) and Chlorides were analyzed and were interpreted using geospatial techniques. The results were evaluated in the context of human health, irrigation, domestic effects. It is revealed by the study that the groundwater in the Amaravathi River basin is affected by effluents from textile industries, irrigation return flows and domestic sewage, in addition to the natural geogenic contaminants.

K. Narmada, G. Bhaskaran, K. Gobinath

Microbial Biodiversity of Selected Major River Basins of India

Indian subcontinent is one of the richest regions in terms of biodiversity. River and its watersheds are the nurseries and habitats for biodiversity, including the microorganisms. In this paper, the biodiversity and ecological significance of four major Indian river basins namely, the Ganges, the Cauvery, the Krishna and the Godavari are reviewed with special emphasis on microorganisms. Through this review we demonstrate that recording and detecting the microbial biodiversity and ecology of river basins would help in the formulation and implementation of appropriate conservation and management strategies in the river ecosystems. It has also shown that, the Ganges river basin is the major microbial diversity region, consisting of nearly 0.5−2.0 × 10

6

cfu/ml followed by the Cauvery river basin (0.33−2.6 × 10

5

cfu/ml), Krishna and Godavari basins >0.1−1.0 × 10

4

cfu/ml.

Ramasamy Balagurunathan, Thanganvel Shanmugasundaram

Application of Diatom-Based Indices for Monitoring Environmental Quality of Riverine Ecosystems: A Review

Diatoms are a large and diverse group of single-celled algae. Diatom-based indices are increasingly becoming important tools for assessment of environmental conditions in aquatic systems. Diatoms have long been lauded for their use as powerful and reliable environmental indicators. The objective of this paper is to review and explain the application of diatoms in environmental studies of river aquatic system. Review of Diatom Research in India and abroad shows that the diatom study and its applications are at nascent stage when compared to their utilization in Australia, Canada, United States and Brazil. The occurrences of Diatoms in surface waters especially in major rivers of the world are yet to be recorded. However, the review of Diatom Research provides considerable scope and applications in understanding and monitoring of environments. From the analysis of diatoms in surface waters of India, we conclude that the diatom studies can be best used in environmental assessments of water-quality of ecosystem.

R. Venkatachalapathy, P. Karthikeyan

Ecohydrology of Lotic Systems in Uttara Kannada, Central Western Ghats, India

The Western Ghats is the primary catchment for most of the rivers in peninsular India. Pristine forests in this region are rich in biodiversity but are under environmental stress due to unplanned developmental activities. This has given rise to concerns about land use/land cover changes with the realization that the land processes influence the climate. Rapid and unscientific land-use changes undermine the hydrological conditions, and deteriorate all the components in the hydrological regime. The developmental programs, based on ad-hocdecisions, are posing serious challenges to the conservation of fragile ecosystems. Considerable changes in the structure and composition of land use and land cover in the region have been very obvious during the last four decades. Pressure on land for agriculture, vulnerability of degraded ecosystems, the vagaries of high intensity rainfall and consequent occurrences of accelerated erosion and landslides, lack of integrated and coordinated land use planning become some of the reasons for rapid depletion of natural resource base. These changes have adversely affected the hydrological regime of river basins, resulting in diminished river/stream flows. This necessitates conservation of ecosystems in order to sustain their biodiversity, hydrology and ecology. In this situation, for resolving present problems and to avoid any future crisis, a comprehensive assessment of land use changes, its spatial distribution and its impact on hydrological regime were carried out. Accordingly, appropriate remedial methods have been explored for the sustainable utilization of the land and water resources in the catchment. The current research, focusing on five rivers located in the central Western Ghats, monitors water quality along with that of diatoms, land use in the catchment and threats faced by these ecosystems.

T. V. Ramachandra, M. D. Subash Chandran, N. V. Joshi, B. Karthick, Vishnu D. Mukri

Relationships Among Subaquatic Environment and Leaf/Palinomorph Assemblages of the Quaternary Mogi-Guaçú River Alluvial Plain, SP, Brazil

Environmental features of the Mogi-Guaçú River fluvial plain located in the northeast portion of the São Paulo State, Brazil as characterized by the dynamics of subaquatic environment, the current pollen rain and climatic analysis of leaf morphologies in selected meander bends. As the area forms a transition between the Cerrado (Wood Savanna) and Mata Atlântica (Atlantic Forest), located in the Ecological Station of Mogi-Guaçú (EEcMG), in the municipality of Mogi-Guaçú, district of Martinho Prado Jr. (between 22° 10′S and 22° 18′S and 47° 08′W and 47° 11′W), the present environmental study involves helped improving the knowledge about the origin and evolution of the Cerrado and Mata Atlântica, and the dynamics of the Quaternary plains that sustain this river ecosystem.

Fresia Ricardi-Branco, Sueli Yoshinaga Pereira, Melina Mara Souza, Francisco Santiago, Paulo Ricardo Brum Pereira, Fabio C. Branco, Victor Ribeiro, Karen Molina

Diatom Indices and Water Quality Index of the Cauvery River, India: Implications on the Suitability of Bio-Indicators for Environmental Impact Assessment

Physico-chemical properties of water are routinely utilized for understanding environmental quality. Diatoms are used as bio-indicators to assess the water quality of surface waters. Independent assessments of environmental quality of the surface waters from the Cauvery River were made and the resultant quality-indicators were assessed in the light of national river water quality standards. Occurrences of sixty (60) species belonging to 21 genera are recorded from the Cauvery River. Water samples were analyzed for various physico-chemical parameters, viz., pH, Electrical Conductivity (μS/cm), Dissolved solid (mg/l), Biochemical Oxygen Demand (BOD) (mg/l), Calcium (Ca) (mg/l), Magnesium (Mg) (mg/l), Sodium (Na) (mg/l), Potassium (K) (mg/l), Chloride (Cl) (mg/l), Bicarbonate (HCO

3

) (mg/l) and Sulphate (SO

4

) (mg/l). These physico-chemical parameters formed the basis of computing the Water Quality Index. The results of the present study on diatom assemblages in the Cauvery River revealed moderate pollution at Siluvampalayam and Koneripatti and high levels of pollution at Peramachipalayam, Kottampatty, Sanyasipatti and Bhavani. The Water Quality Index revealed pristine nature of the Cauvery River water in upstream regions that became unsuitable for human consumption downstream of Bhavani Town. The values of DO and BOD levels indicated absence of major organic pollution. Comparative validation of the physico-chemistry and bio-indicators suggested sensitive nature of the Diatom indices to environmental variables and thus the diatom indices can be a reliable tool for environmental impact assessment.

R. Venkatachalapathy, P. Karthikeyan

Species Diversity and Functional Assemblages of Bird Fauna along the Riverine Habitats of Tiruchirappalli, India

Riverine ecosystems have complex relationship with human since time immemorial and play an integral role in the socio-economy of a region. However, many riverine habitats, particularly within urban centers in the developing countries are subjected to overexploitation that affects the natural ecological processes and functions of rivers. Such perturbations in riverine habitats are often linked to biodiversity loss. Birds discharge crucial ecosystem services and are closely associated to wetlands and rivers for their survival. This study attempts to document the bird diversity and their community assemblages along the riverine habitats in relation to urban effects, vegetative attributes, seasonal parameters and other anthropogenic pressures. The study finds that bird diversity and species richness were higher in the rural landscape and gradually decreased towards the urban region. A total of 120 bird species consisting of two ‘Near Threatened’ were recorded along the riverine habitats of the River Cauvery. Few species (

Egretta garzetta

and

Phalacrocorax niger

), were found to be densely populated and adapted to the urban environment while few others declined. Salient features of the results include: seasonality did not affect the variability of the riverine species and the difference in composition of birds during the wet and dry seasons were insignificant. While the factors namely, tree cover, tree height, and number of trees were found to be positively correlated, the anthropogenic factors namely, extent of built up land, noise levels and vehicular traffic contributed negatively towards bird diversity. Among the various riverine stretches/study sites, the Kallanni region recorded highest species richness and diversity. The most important conservation measure would be to declare Kallanai an important bird reserve and the agricultural farmlands on either sides of river Cauvery at Kallanai be declared as ‘High Nature Value’ (HNV) wetlands/farmlands to protect the overall biodiversity.

Manjula Menon, M. Prashanthi Devi, V. Nandagopalan, R. Mohanraj

Ecologically Sound Mosquito Vector Control in River Basins

Human population growth and resultant environmental modifications across all the landscapes of the Earth, new interactions between human species and the natural processes have emerged, that promote new epidemiological patterns of vector-borne diseases. Among all the vectors that spread epidemics among the humans, mosquitoes stand second to none. Over the decades, several methods have been developed, for protection against mosquito borne diseases albeit with varying rates. No one mosquito-control strategy fits all situations, and management of mosquitoes should be addressed on a case-by-case basis that identifies local and regional differences in mosquito species, geographic setting, and watershed context. Further, socio-economic, environmental and epidemiological factors will determine the choice of vector management strategies. A majority of these methods attempt killing both adult and immature stages of mosquito vector. Currently, mosquito vector control is mainly based on insecticides, but its sustainability has been undermined by the development of resistance and growing concerns about the long-term environmental impact of insecticides. In addition to the environmental damage, anthropogenic activities have created extensive breeding sites for the vectors, especially the mosquitoes. Mosquitoes usually breed in places close to the banks of rivers and creeks where there is protection from currents by obstacles, protruding roots, plants etc. Source reduction is usually the most effective, eco-friendly and economical approach for mosquito control technique which is accomplished by eliminating mosquito breeding sites. This paper provides information of ecologically sound mosquito vector control methods particularly in and near river channels. Usually, it is presumed that the stagnant regions of river channels and adjacent locations are the preferred regions of mosquito production. However, river channel with healthy biodiversity with a diverse community of predators that prey on immature stages of mosquito often produce few to no mosquitoes. Hence, detailed knowledge of the sites in and near the river channels, and promoting and preserving biodiversity in the river basins are necessary for cost-effective, eco-friendly vector control measure. Further, basic research is recommended to better define the cost-effectiveness of the various tools and management options used currently for the management of mosquito vectors particularly in and near the river channels.

Tapan Kumar Barik
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