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River Geochemistry

River Geochemistry

 

River Geochemistry

K.P. Thrivikramaji

Department of Geology

University of Kerala

Kariyavattom – 695 581

Final Report Submitted To the Chairman,

State Committee On Science,

Technology and Environment.

Government of Kerala

Trivandrum April 1989.

 

 

 

 

 

Contents

Abstract

Acknowledgements

Introduction

            Modification

            State of the art

            State of the art in Kerala

            Summary

River basins

            Introduction

            Physiography

            Geology of the basins

            Fate of eroded soil

            Summary

Description of Rivers

            Vamanapuram Ar

            Ithykara Ar

            Kallada Ar

            Achankovil Ar

Previous work

            Definition of sediment load

            Accuracy of measurements

            Erosion rates

            Problems with estimates

Sample collection

            Sampling device

            Procedure

            Estimation of suspended load

            Estimation of dissolved load

            Mineralogy of suspended load

            Concentration of suspended load

            Relation between the various categories of loads

Summary

Recommendation

Reference

 

 

 

 

 

 

 

River Geochemistry

Abstract

River Geochemistry deals with the study of the chemistry of the dissolved constituents of water. This study is very relevant now as the humanity is more dependent on such limited resources like the surface water and underground water these days than any time in the past. The knowledge of dissolved salts in water is a pre-requisite for making any decision on the proposed or potential use of water for any specific industrial, irrigational or domestic purposes.

Secondly, another important reason to have knowledge of the content and concentration of dissolved salts in water, arises out of the utility of such data on studies relating to the rates of denudation of the rocks and sediments exposed on the surface of the earth. Such data are used in conjunction with the suspended load concentration, in the computation of denudation/erosion rates of river basins. The bed load of any stream is bound to the slowest moving load down-river and it constitutes only a minor fraction of the total load.

Studies on the spatial and temporal variations of the load flux through the river channels are considered highly useful by geologists, geochemists, geomorphologists and environmental scientists. The appreciation of water chemistry and soil chemistry are essential in tracing the pathways of elements through the plant and animal kingdoms. In fact, elements that are present in the tissues of plants and animals can easily and up in human tissues, when such vegetables and meat are consumed.

The suspended/dissolved loads of rivers are highly variable with season and from place to place in the river. Many of the toxic elements may ‘ride piggy back’ on suspended particles, and thus may be deposited in the channel or flood plain, to be resuspended in the stream flow at a later date.

It is proposed that studies on the geochemistry of river water, of the soils etc. should be undertaken to map the distribution and concentration of elements that are useful or harmful to man as well as animals and plants. It should be followed up by preparation of an atlas with plates displaying the distribution of such elements, for consultation by the planners and engineers concerned with the welfare and public health.

Acknowledgements

The idea of research on River Geochemistry occurred to me, when I developed more than adequate interest in the field of Environmental Geology. Dr.V. Subramonian, Jawaharlal Nehru University, was perhaps an immediate source of inspiration to launch this study.

I thank chairman and members of the State Committee on Science, Technology and Environment for generously supporting this research with adequate funding. I must also admit that I had delayed the submission of this report for reasons beyond my control.

The XRD analysis of suspended load reported here were carried out in the Patrice Lumumba Peoples Friendship University, Moscow, while I was visiting that University under a Indo-Soviet Cultural Exchange Programme in the summer of 1986.

The Chief Engineer, Central water Commission, Southern Region, Hyderabad, very generously agreed to share the discharge data. The field staff of the Central Water Commission, at Ayilam, Ayur, Pattazhi and Thumbamon co-operated with me during the field visits with lot of curiosity and at times with profuse humour.

The university of Kerala and the Department of Geology wholeheartedly supported my activities related to this investigation. I thank Dr. G. Prema of the Department of Geology for supervising the analytical work and at times for taking up the analytical work herself.

Department of Geology                                                                         Dr. K.P. Thrivikramaji,

        Kariavattom                                                                                  Principal Investigator.

        April, 1989

INtroduction

            The pair of words – River Geochemistry – is equally well-known to geologists and geochemists. Truly, River Geochemistry is a branch of Applied Environmental Geo-chemistry. The study of suspended and dissolved loads of river water is the main theme of investigation. At times the geochemical studies aimed to characterize the elemental distribution of the bedload of rivers and the sediment samples of the flood plain are also included under river geochemistry. The study of the abundance and variation of various chemical elements in sediment and water of the fluvial system or streams has attracted many investigators from the very early days of Geochemistry. However, in the post-war period like other branches of sciences and geology, Geochemistry also received a fillip. Moreover several new dimensions were added to the application of the results of such studies.

            The knowledge of the chemical elements and their distribution in the atmosphere, hydrosphere and lithesphere are essential for the understanding of their dispersion, pathways and geochemical evolution of the earth. For example such knowledge is essential for speculations on the formation of igneous rocks and magmas, metamorphic rocks and various sedimentary rocks as well as various ore and mineral deposits. Geochemical studies (of the stable and unstable isotopes) have also helped in predicting the temperature of formation of rocks and mineral deposits, and in dating of rock formations. The chemistry of hydrosphere i.e., of lake waters is equally important in that it helps in the speculations and modeling of the primordial ocean water, evolution of characteristics of water through the geologic time and the concentrations of the various solutes in the past and present day water. Geologists very ritualistically follow the dictum of uniformitarianism and therefore, assume that the various geological processes taking place today are identical to those that took place in the geologic past. Under these are included the processes of erosion and deposition, However, it is fair to assume that some processes like erosion, transportation and deposition do not follow strictly the principles of uniformitarianism. Certainly, there are bound to be differences in the rates of these processes between the present and the past.

            The atmospheric chemistry is concerned with the chemistry of gases contained in the atmosphere, of the chemistry of the particular matter held in the air, and of the abundances fluxes and exchanges between the atmosphere and hydrosphere of these gases. The evolution of the composition of the atmosphere is reflected in very ancient sediments on the one hand and later modern sediments on the other.

Modification

            With the exception of the degradation of rocks through processes of weathering, the modification of the lithospheric composition is little since the formation of the rocks. But the magnitude of changes of chemistry of hydrosphere and that of the atmosphere are far more in space and time. IN fact such modifications are partly a function of the human actions like deforestation, crop farming, fertilizer application, release of untreated effluents from factories and chemical industries, etc. Such point specific and region specific pollutants enter the pathways of natural elements and tend to modify and alter the processes, products, and characteristics of the hydrosphere and atmosphere. Sometimes such changes are detrimental to the polluter, the human.

            The acid rain and green house effect are two of the excellent examples of the consequences of human modification of portions of atmosphere and hydrosphere. Acid rain due to the dissolution of man made gases of atmospheres in rain drops, causes defoliation of many members of the plant kingdom, stunning of growth of trees, and sometimes leading to ultimate destruction. The acid rain water further descends to the ground and reacts with the soil minerals, leading to their modification. The entry of acid rain water into the surface water bodies like lakes and streams or into the aquifers are considered equally dangerous, in the long run. The water of the surface water bodies becomes inhospitable to the plants and animals that thrive in there. The acid stream water once reaches the ocean, the ultimate sink, will further modify the chemistry of the sea water and trigger off a chain of reactions. The modification of quality of ground water is also of very serious consequences.

            Equally detrimental is the consequences of release of green house gases to atmosphere by burning of fossil fuels. The abundance of such gases in the atmosphere prevents the escape of long wave length heat radiation at night time to the outer atmosphere and results in the gradual warming up of the lower atmosphere leading to the melting of glaciers, ice sheets etc., and consequent rise in the mean sea level. Several sea level rise scenarios have been proposed by Hoffman (1984). However, one point, the scientific community agrees up on, is the inescapable trap of a higher sea level. The property, the land of the littoral states of the various continents are to bear the maximum brunt of the rising sea level.

            The pollution of aquifers also takes place by the pipe-lines carrying various types oil, petroleum products and so on. Any leakage in the conduits will gradually release the liquid that it carries into the vadose zone and from there it will join the aquifer. Supposedly a great potential for the pollution of the aquifer exists in below the ground gasoline and diesel storage tanks of the filling stations. These storage tanks invariably are made of mild steel. According to one estimate any such MS plate tank, even if kept under ground is bound to develop leakage in a matter of 15 to 25 years. The leakage will go unnoticed most of the time as these tanks are out of sight and hence are not readily available for inspection. Secondly any shortage between the input into the tank and output at the sale end, would be assigned to ‘faulty’ metering. Further, most of the measuring systems in the outlets are tampered with and hence the leakage if any, will be ignored by the dealership. Any such inadvertent entry of gasoline into the aquifers are of grave consequences. The very low content of gasoline in ground water can be very lethal in the long run. It is also known that the detection of gasoline content in the ground water are pretty complex and expensive. Such point specific pollutants are easy for detection as well as for control. Unfortunately any aquifer that is contaminated like this will take more than a millennium for rectification, leading to the abandonment of the aquifer as the only possible recourse.

State of The Art

            The river geochemical studies are in vogue in one form or other in many countries of the world. India too is no exception. Before surveying the Indian context the world situation will be surveyed. Geochemical studies of the earth material were undertaken by geologists and geochemists for various reasons, including the detection of geochemical anomalies useful in the detection of mineral deposits. All the national surveys, either have groups or divisions working in the field of exploration geochemistry. When people became increasingly aware of the deterioration of water quality of lakes, streams and reservoirs spontaneous attention was paid to the monitoring/characterization of such suspected water bodies. The incorporation of water resources wing in the National surveys thus became a logical consequence of such activities.

            Furthering of the geochemical investigations became evident with the realization of the importance of the chemical elements for the welfare of man and progress of nation. The identification of pathways of natural elements in the pedosphere, hydrosphere and atmosphere gave an impetus for further work and a whole new branch of geochemistry called Applied Environmental Geochemistry came into being. In Britain, the research in this field is undertaken by Applied Geochemistry Research Group of Dept. of Geology at the Imperial College. It started out with the research applications into agriculture and the study was founded by Natural Environmental Research Council. It was followed by a joint programme by geologists, geochemists soil scientists, water engineers and medical practitioners to study the unusual incidence of cancer in part of southwest England.

            Now Applied Environmental Geochemistry has grown enormously covering the factors influencing sources, dispersion and distribution of elements in the environment. The path ways of the elements in the environment. The path ways of the elements into food stuffs and water supplies and possible effects of these on health and diseases of plants, animals and man are under investigation. Geochemical atlases for use by other agencies of Government were prepared using the results of several such studies. Canada, U.S.A., and U.S.S.R., also had contributed substantially for the Applied Environmental Geochemistry, in the early days. In the US the subcommittee of the National Academy of Sciences has taken the load in organising several workshops on the Geochemical Environmental Geochemistry and Health was also established, as part of the workshop programme.

            As far as India is concerned, one must find gratification in the importance the Government has laid is cleaning up of the River Ganga. In a way I see the Applied Environmental Geochemistry at work and in the service of man through the Ganga Action Plan. This programme of cleaning up of Ganga has two benefits; one, we develop the required skills and frame of mind to undertake the work ourself, and two, later the expertise acquired can be very beneficially used in the case of other riverine environments elsewhere in the country. The Geological Survey of India with all the personnel and facilities has not yet seriously taken up any Applied Environmental Geochemical work. The universities rightly on other  hand, taken the lead very early, as early as the late seventies. The Jawaharlal Nehru University, Benares Hindu University, and the IIT, Powai are some of the good examples.

            Surely, it is not surprising to note the delay in catching up with the rest of the world in this field. In fact the concern about the Environment, in the official Indian mind, did not occur till the Stockholm conference on Environment. The Ministry of Environment and Forests, Govt, of India has now institutionalised the national perspective and programme on environmental studies. The fully be utilised by the individual researchers or organisations, if the sharing of data on the environment are made mandatory.

State of the Art in Kerala

            In Kerala the data environment and specifically on the Geochemical Environemet are wanting. My research perhaps is an exception. Through I covered only 4 of the streams of the south Kerala, the data generated out of the investigation is considered very important in many ways. Firstly, discharge weighted load determinations (chemical and well as suspended loads) have been made. In fact each river basin of Kerala has to be subjected to such a sediment flux audit say in the course of nest 5 to 10 year in order to acquire background information of the geochemical environment of the water bodies, and pedosphere. Where ever, gauge data exists, the load flux from the river basis must be estimated. In addition the studies can be extended to a micro-level, where the relationship between the land use, sediment chemistry, sediment quantua etc can be worked out. And ultimately state level and regional geochemical atlases can be prepared for use in the planning and developmental organisations with concern in the area of public health.

Summary

            A survey is also made of evolution of applied environmental geochemistry in the international scene and at home. The need for the study of the sediment discharge through the rivers are examined. The need to document the chemical composition of the solute and suspended load are evaluated. The need for generating atlases showing the distribution of various chemical elements in the pedosphere, and hydrosphere are underscored.

Chapter II

The River Basins

Introduction

            In the following discussion the physiography, geology and land use of the Vamanapuram, Ithykkare, Kallada and Achankovil rivers are treated briefly. A curious reader is directed to more detailed discussions on these by Soman (1922).

            Keralaisendewed with 41 west flowing and 3 east flowing rivers (Table 1). Kerala enjoys a monsoonal climate, and hence the rivers of Kerala seasonal. In other words, the bankful stages are punctuated by periods of base flow twice annually. The South west and the North east monsoons are the caused of such distinct seasonality of river discharge.

            The physiographic divisions of Kerala are the Low-land, Midland and the Highland zones. The Highland is formed by the Western Ghates and lie along the eastern border of the state. This tract is covered by dense growth of vegetation characterised by patches of tropical rain forest and overgreen forest. The Ghat section is characterised by very steep gradients and rocky slopes.

Physiography

            The Kerala region can be divided into four distinct geomorphic zones, which are represented in the river basins examined in this research. The highland zone ranges in altitude from nearly 600 m to 2500 m, the midland from 300 m to 600 m and the lowland from 30 to 300 m. The coastal land is characterised by lagoons and ancient or modern dunes. The kerala Public Works Department in one of their reports have identified three physiographic zones viz., the lowland falling below 25 ft. (7.6 m), the midland lying between 25 ft. and 250 ft. (7.6 to 76 m) and the highland rising above 250 ft. or 76 m. (Anonymous 1974).

            The lowland region covers most of the state and about 62% of the total area of the state i.e., say, 24, 000 Km2 falls within 0 to 300 m. altitude range (Sinha Roy and Mathai, 1979). Another important aspect of the topographic grain of the region is the ridges and alternating valleys (lineaments) that strike roughly in a NW-SE direction. The river courses are in fact initially controlled by the regional strike of foliation of the crystalline rocks. The Achankovil lineament and the Achankovil shear zone are typical examples. The Achankovil river course for a very major part of its initial length lies in this lineament. The Vamanapuram river and the Kallada rivers also have their upstream courses controlled by the distinct strike of foliation of the country rocks which coincides with the major lineaments.

            When the rivers descend further down in the highland, to enter the midland region, the thickness of cover of laterite on the basement rocks are on the rise and the river course in fact is gradually freed form the structural control. On still further descend into the lowland and costal land the energy of the stream to maintain a course of its own is dominantly illustrated.

Geology of the basins

            The area covered by these basins are geologically more or less monotonous. The highland zone – western ghat zone-is formed by the oldest rocks of Pre-cambrian age, belonging to the granulite facies of metamorphism. Charnockite, geneisses, basic dikes, quartz and pegmatitie veins are typical of the Pre-cambrian rocks. Most of these rocks are very rich in th lements like o, Si, Al, Fe, Ca, Na, K, Mg in the order of abundance.

            The rocks have undergone weathering and have transformed themselves into laterite. Laterite in Kerala coastal belt has also formed out of the transformation of sedimentary rocks of Tertiary age, and occurs as cappings. Further weathering of laterite has given rise to lateritic soil. Laterite is very rich in either oxides of iron or aluminium, and in the latter case sometimes qualifies as an ore of Aluminium. In the lowland zone large and extensive outcrops of laterite derived from the Precambrian rocks as well as laterite derived form the sedimentary rocks of Teritary age have been noticed.

            The coastal land zone on the other had is the result of the late tertiary and quaternary processes of sedimentation, and dispersal of sediments. Effects of Neotectonics are also noticed in this tract. The coastal land zone is characterised by the presence of lagoons which link the river channels with the Laccadive sea.

Human Intervention

            These basins have remarkable evidences displaying Human actions like deforestation, crop farming, habitation, settlements, etc. Though it has been suggested that at least 1/3 of the total land area should be ideally under forest cover for the benefit of the population, the situation in Kerala is really appalling in that unlike the rest of the country, the area under forest cover in Kerala is less than 30% (Say like 28%, to be precise).

            The extraction of timber and forest produce were part of the efficient management of the forest resource, and Kerala also followed this philosophy meticulously. However, the need for more farmland in order to grow more food and also to accommodate the ever increasing population unofficial forest encroachment was either encouraged or allowed to take place without any hindrance or objection from the Government. Further, understanding of the role of forest was under an evolutionary process, resulting in the modification of norms of forest management and exploitation from time to time.

            This resulted in the excessive deforestation and erosion of slopes and uplands which were made temporarily barren by the removal of the forest and brush cover. This accelerated erosion against geological erosion has not caught the proper attention of investigators yet. This situation naturally enhanced the suspended load supply to the streams in the region. The rivers under report here and also not exempted form this syndrome. Most of the area of the highland region especially towards the lower elevations are under the grip of accelerated erosion at one time or other. The higher altitudes are mostly covered by unaltered or partially altered rocks without any soil cover.

            The midland and lowland zones are also not free from the erosion problem. Raising of annual crops like Tapioca etc., calls for turning over of the top soil before planting, which indirectly prepares the tract of land for erosion by rain splash and impact and transport of the soil particles. Apparently most of the activities of people in the area of rising food stuff, for simple sustenance or for earning huge profits are congenial to the erosion and loss of valuable soil.

Fate of the eroded soil

            It is unfair to assume that the soil or sediment lost during the erosion of slopes and uplands directly reach the stream and are immediately transported as suspended load in the ocean.

            In fact it is not true at least in the case of very large rivers (Meade, 1984). Huge quantities of sediment are stored in the channel net work itself. Such sediment is occasionally resuspended and transported again to be deposited soon, at some downstream point. However, the suspended load and dissolved load are able to travel with the same speed as the water in the stream. But the waxing and waning of the velocity may change the competence resulting in deposition and resuspension of load.

            However, the load deposited in the flood plains gets resuspended only when another flood of the equal magnitude recurs. It is now a generally established fact that the suspended load spends time in the various channel reaches, due to modulation of the competence of the stream due to changes in the configuration of channel, channel bed and walls, as well as due to local changes in channel slope. The consequences of  residence of the load in the channel bed and flood plains or rivers have great ramifications especially when the finer particles carry’ piggy back’ on them heavy metals and other toxic chemicals.

Summary

            The Vamanapuram, Ithykara, Kallada and Achankovil river basins have many aspects of physiography, geology and river net evolution in common. The deforestation, crop farming and pressure on land have led to a great deal of erosion of the soil material which denuded the load. This erosion is styled as accelerated erosion by geologists and soil scientists. IN the case of very large rivers the sediment load of rivers are stored for considerable lengths of time in the channel net work.

Description of Rivers

            A brief description of the rivers under report are given below. Data for Neyyar river is included in another report (Thrivikramaji, 1986) and the Karamana has not been investigated as there is no gauging operation in this river, at the time of data collection (See Tables 2 and 3).

Vamanapuram River

            The Vamanapuram Ar. Originates in the Cheminji Mottai at about an elevation of about 1860 m above MSL. and joins the Kalaiparai Ar. – after traversing a distance of 7 km. At Kallar, The Ponmudi Ar and Pannivadi Ar. Joins it. The Chittar is an important downstream tributary. At Manjappara. The Manjappara Ar joins this river and continues a westerly course upto Palode. At about 3 Km downstream of Palode there is a waterfall of about 13 m. drop at Meenmutti. This river receiver two major tributaries, viz., the lower Chit Ar. and the Kilimanoor Ar. Before it empties into the Arabian sea, through the Anjengo lagoon.

Ithykkara Ar.

            Ithykkara Ar rises form the Madathura kunnu at a very low elevation of 240 m. above MSL, and also from the hills falling to the south of Kulathupuzha. Like the other majority of streams of Kerala its initial course is in a northwesterly direction – a dictate of the regional strike. Then it takes westerly course between Irathur malai and Pampira. However, in the lower reaches, the channel trends in a southwesterly direction before it empties into the Paravur Kayal. This river has a basin area of 642 Km2 and a (master stream) length of 56 Km.

Kallada Ar.

            The Kallada basin is one of the major river basins of south Kerala. An irrigation dam has been completed in this basin at Thenmala. As a later thought, plans are under way, for the installation of a low-head hydel station at Thenmala. This river has three major tributaries viz., Kulathupuzha, Chendurini Ar. And Kalthuruthy Ar. Which join together in the vicinity of Parappar. The Kulathupuzha tributary rise from the Kadakkad area of Papanasam range at an elevation of about 1524 m above MSL. The Kulathupuzha takes northewesterly course like the Achekovil Ar. up until Moyal medu, and then follows a northerly course to join the Chendurini Ar at Kalangunnu. Karimalai, Kadakkal and Alwarkurichi peaks are the abodes of Chendurini Ar. which follows a northwesterly course till it joins the Kulathuppuzha. The several lower order streams that lead into Kalthuruthy Ar. rise from the Perianurthi Malai (855 m), Padikkattu Malai (853 m), and Pillayarkovil Malai (808 m). Then Kallada follows an initial southwesterly course followed by a westerly one towards Thenmalai to join the Kulathuppuzha at Parappar. From Parappar it regains the northwesterly course heading towards midland. It finally takes a southwesterly course to ultimately join the Arabian sea via., the Ashtamudi lagoon.

The Achankovil Ar.

            The Achankovil Ar. lies to the north of the Kallada Ar. It originates form the Pasumkita Medu, Ramakal Teri and Rishimala at altitudes ranging between 700 m to 160 m above MSL. This stream follows a northwesterly course which has lately been renamed as the Achankovil Shear zone. In fact the northeasterly course exhibited by many of the streams in Kerala is perhaps the result of orientation of the major zones of weakness, which has been taken advantage by the rivers. The coastal land at the downstream and the Ahcankovil Ar joins with the Pamba Ar. at Veeyapuram. The Central Water Commission maintains a gauging station at Thumbamon. The stream has a length of 126 Km and a basin area of 1484 Km2.

Chapter – III

Previous Work

            Until recently in Kerala the River Geochemistry has remained a least traveled terrain by geologists and geochemists. But it needs to be admitted that several agencies of the state like the Ground water Department, Pollution Control Board and perhaps Kerala Water Authority have been monitoring the water quality aspects including the chemistry of the solutes in water. In addition, Central Water Commission, Central Ground Water Board etc., also should be analysing samples of water to characterize and monitor water quality.

            Though data sets of this nature are not uncommon, the application of such data by geochemists in discussing the rate of denudation, relation between the climate and weathering or the extent of human activity and sediment production has not been attempted. In the national scene only exceptions are the contributions by a Jawaharlal Nehru University group and occasional contributions by a group of workers in the Benares Hindu University. There also exists an active group of workers in the PRL, Ahmedabad and also in BARC.

            As a part of the International Hydrological Decade, a scheme was launched by Government of India, to establish gauging stations in many of the major river basins of the country, to monitor not only water discharge but also to keep track of the suspended load and solute load, using methods of international standard. The data have been published by Government of India from time. Currently, even after the conclusion of the IHD, the monitoring programme is expanded and continued to cover many more river basins of the country. In order to qualify for gauging by CWC, a river basin should have at least 1000 Km2 basin area. On special instances, rivers of much lower basin areas also will be taken up for gauging.

            In the International scene the situation is far better. The developed countries which showed the path of approaches and programmes in monitoring the river discharge are the leaders, and have demonstrated to the world that gauging and monitoring are the basic to an estimate of the water resources of any country. A variety of manned, partially manned and un-manned facilities are operated in various parts of the world.

            The US Geological Survey and its Water Resources division have been engaged in the task of monitoring and gauging for several decades. In addition to river water quality, quality of ground water and lake water have lately become very important. Credit must got to Livingstone (195 ) for compilation of a data set on composition of water and for providing an average river water composition. (Table ). Analysis’ interest in monitoring of the dissolved load and suspended material of rivers is primarily couched on the need to know the type and amount of material under transport in the rivers and delivered to the oceanic basins. Such data can be and have been indirectly used to determine the rate of erosion or denudation of the river basins and hence of continents.

            Several other interesting lines of research have emerged lately, out of the investigation of chemical load of rivers. The question of acid rain is a case in point. In fact the monitoring of the water chemistry and water quality was the intention of analysts who stumbled on the exceptionally high acid nature of the rain water as well as river and lake waters from various part of the World. The hydro-geochemical pathways, pedogeochemical pathways, phyto-geochemical pathways of some of the lethal and man made or man introduced elements and chemical compounds also have been identified as part of such studies.

Definition of sediment load

            Included below are some definitions that are relevant to this work. In a stream there is simultaneous transport of sediment in suspension, saltation, rolling and sliding. Further, there is also constant exchange of material from one mode of transport to the other. All the load that is under transport in a stream can easily be classified as Total load, with out any great deal of confusion. The total load then can be sub-divided into chemical load, suspended load and bed load. Meade (1987) has proposed the following definition to identify various types of load.

(i)   Sediment concentration: It is the mass of sediment suspended in a unit volume of river water usually expressed as grams or milligrams per litre.

(ii)   Sediment discharge is the mass of sediment transported by a river past a given point or a given cross section in a unit time, usually expressed as Kilogram per second, ton per day or ton per year.

(iii) Sediment yield is the mass of sediment transported by a river in a unit of time divided by the drainage area upriver of the measuring point; it is usually expressed as ton per square kilometer per year. Although it is used as such, sediment yield is not synonymous with erosion or denudation rate.

(iv) sediment load is a qualitative term that is best used in descriptive discussions to denote the material is often synonymously used with sediment discharge. Geochemists tend to use this term as a synonym for sediment concentration. However, Meade (1987) proposes that his last usage should be discouraged.

The following definitions are from Kolby (1963). These are included here because river engineers and geomorphologists frequently use these definitions

(i)   Bed material is the sediment on the bed of the river. This term can be used regardless of whether the sediment is stationary or moving.

(ii)   Bedload is the sediment that is moved along the river bed by rolling, sliding or slipping within a few grain diameters of the bed. Sometimes, the term bedload is used mistakenly to describe stationary material.

(iii) Suspended load is the material being carried in suspension by a river, and being maintained in suspension by the upward component of turbulence of the river.

Further, in engineering usage, the suspended load is divided into two other categories. They are:-

(i)   Suspended bed material load consisting of suspended particles whose sizes are large enough to occur in appreciable quantities at the surface of the stream bed.

(ii)   Washload consists of suspended sediment so fine grained that it is only an appreciable fraction of the sediment on stream bed.

            Bed load is generally the most visible part of the river load. The river bed is normally covered with an appreciable thickness of the bedload which becomes visible only at times of low discharge or no flow condition. The bedload of rivers are normally characteristically of sand size. The bedload of rivers has also become a steady source of construction or foundary sand in many parts of the world. However, these days great deal of concern is expressed by researchers on the excessive removal of bed load sand from the stream channels. (Thrivikramaji, 1986).

            Bedload is normally moulded into many types of bedforms that reflect the flow conditions characteristic of that section of the river. Monitoring and measuring the bedload is difficult as well as expensive. The logistics and reliability of measurements are complex and questionable. For example the very introduction of a sampling device at the measuring site would alter the flow parameters such that the material trapped will no longer be in equilibrium with the flow sans the sampling device. An indirect way of collecting bedload sample is its collection after the cessation of the discharge event. Therefore the practice around the office of the river engineers has been one of indirect estimation and prediction of bed load.

            For this and other reasons the collection of suspended load has undergone lot of refinement and the reliability of the results have also been on the increase. Menard (1987) observed that the accuracy of suspended load measurement of many of todays rivers lies within plus or minus ten percent and further he proposed that the bed load content of many rivers is within the range of error or measurement of suspended load. Further the suspended load, unlike the bedload, has the same velocity as the water that transports it. It is also true for the dissolved load.

Accuracy of measurements

            It is essential to have a degree of accuracy in all stages of the geochemical work, without which the utility of the data becomes questionable. This can be achieved by adoption of standard practices of sample collection, storage and analysis subsequently in the laboratory. In the field situation the distribution of suspended load in the water column is as uncertain as the distribution of velocity. It has been confirmed time and again that the distribution of suspended load is very high near the bottom of the flow.

Erosion rates

            Several methods of estimation of erosion are known today. Schumm (  ) had used pegs with freely moving washers to monitor the depression of land surface around the peg when the washer exposes newer length of pegs or elevation of land when the washer is covered by deposition of sediment. In either case the extent of erosion or sedimentation can be assessed. Unfortunately such point measurements of erosion are not suitable or reliable for extrapolation over a large area like a river basin. It was Archibald Geikie (1886) who measured the rate of erosion of the land area for the first time. He related the suspended sediment measures to crude estimates of vertical denudation of drainage basins. For example he arrived at an average of 50mm/ 1000 yr./ estimate for temperate latitudes.

            Regional denudation rates can be calculated as follows:

            D(m3Km–2 Year–1 = mm/100 year)

            The specific gravity of rock (say 2.5 or 2.65) is used on the assumption that the soil thickness remains constant. According to some authors for estimates of denudation the suspended load, dissolved load and bed load data are essential. For others, the first two are essential. In my estimates the suspended and dissolved loads are used.

Problems with the estimates

            As has already been stated the estimates of denudation rates using the load estimates are not without uncertainties. For example, in some estimates the chemical and suspended loads are used and for still others in addition to these the bed load is also used. Investigators have also reported a common trend in denudation estimates. In the case of very large river basins the rates of denudation are relatively low whereas for small river basins the rates are steeply high (Table  ).

            According to Schumm (1984) such an inverse relationship between the basin area and denudation rate is due to many reasons. In the smaller basins the gradients are bound to be steep for the valleys and channels inducing more rapid erosion. Further the opportunity for sediment storage within the flood plains, valleys, and channels are much less leading to more erosion. Smaller basins generally are more efficient in stream transport than the larger ones. Due to the smaller size of the basins storm events are more intense per unit area and hence the rate of erosion. In addition the morphometry of the basin, the nature of the rocks exposed in the basin, extent of forest and vegetation cover, the tilling and cropping practices in the basin also play significant roles in determining the load output. The climate is another important factor deciding the quantum of loads shed from the river basins (Table ).

Sample Collection

            A modified version of an USGS water resources division sampling and analytical procedures has been adopted for this study. Interested readers are referred to Hem (1970)

Sampling device

            However, a brief description of the sampling equipment is included below. A three liter plastic can with a 4 cm diameter mouth was used for collecting samples. This can is strapped to a ‘Cradle’ and is lowered to the required depth from a canoe or from the side of the deck of a bridge– A 10 kg metallic ‘fish’ is added to the bottom of the ‘cradle’ to maintain the verticality of the sampling bottle during sampling. The mouth of the bottle is covered with a ‘condom’ which can be easily pulled off at the activation of a string remotely from the canoe or the sampling platform. The depth of sampling below the water surface can also be kept track of by the operator. A vent is provided in the bottle for the escape of trapped air in order to allow the entry of water through the mouth.

            This sampling device helps to collect a sample of water confined only to thin layer that is in motion. In the sampled layer only a specific point is being sampled. Therefore the suspended load of the stream is not truly represented by the sample. However, the method does not affect the estimate of dissolved load from the sample. It was also not the intention to collect depth integrated samples of water in order to acquire a better estimate of the suspended load. The distribution of suspended load in the water column and the variability of the suspended load have been treated elsewhere in this report.

Procedure

            The plastic sampling bottle would also serve as the storage can for samples. Every time a sample is collected, a new can is used, because of the case with which the bottle (can) is strapped to the ‘cradle’. Initially the bottle is washed in the laboratory. In the field the bottle is washed and rinsed in the water at the collection site. After collection of the sample from the stream, the sample is immediately checked for the pH, conductivity and temperature. However due to break down of the some of the probes the estimation of some of the parameters were discontinued. The dissolved oxygen content is a case in point. The mouth of sampling bottle is then properly covered with the press down cap and the screw cap, and a proper label is fastened to the handle of the bottle. The sample bottles are stored in a krate for secure transport to the laboratory. All samples are analysed from the third day of collection. Therefore pretreatment of the samples were not carried out in the field.

Estimation of suspended load

            Estimation of suspended load is the first step of the analytical procedure. By definition all material that is larger than 0.45 micron diameter is considered as suspended load. Material smaller than the 0.45 micron is estimated under dissolved load.

            A ‘Sartorius’ vacuum filtering unit was used for the filtration of suspended material. This standard unit has a flask made of glass connectable to a vacuum pump and it stores the filtered water. To the flask is attached the stainless steel funnel storing the water sample. The bottom of the funnel has proper provision for easy placement and removal of ‘Sartorius’ quantitative filter paper to trap the particles which are larger than 0.45 micron size. Approximately a three liter water sample takes 3 to 4 hours of vacuum filtration. The volume of the filtered water is estimated using a measuring cylinder. The suspended load trapped in the filter paper is dried in a hot air own set at 650C and is weighed afterwards using a ‘Sartorius’ electronic balance, along with filter paper. As the weight of the load is estimated by taking the difference between the two, and recorded as the weight in the sample as well as the weight in unit volume of water after appropriate reduction.

Estimation of the dissolved load

            The procedure used for the estimation of the water chemistry and hence of the dissolved load is given in Thirivikramaji (1986). The methods are standard and haven adopted with or without suitable modification from the USGS methodology. The river water chemistry for the various stations, rivers and seasons are given in Appendix III. The variability of chemical load is a rule in the river water. The discharge is bound to change with the precipitation pattern as well as with the schedule of snow melt. The surplus water added to the basin is bound to dilute the solute content of the water. Generally speaking the dissolved load is high during the lean flow or base flow periods and is relatively low during the bankful or flood discharge periods.

            In the Vamanapuram Ar the dissolved load content ranges between 40.3 mg/lit and 86.3 mg/lit. The TSS (Total Suspended Sediment) content falls between 0.00853 gm/lit and 0.0815 gm/lit. The highest solute and suspended load content are in the month of Oct. 1985. So the total load supply is reckoned in the month of Oct. 1985 for the Vamanapuram river.

            In the case of Ithykkara Ar Nov. 1986 showed lowest TDS content of 61.24 mg/lit. 96.8 mg/lit, the highest TDS occurred in the month of Oct. 1985. Generally speaking the TDS is a function of the degree of dilution of discharge by rain water. The TSS values registered the maximum in Oct. 1985 and minimum in the month of Dec. 1985. The highest total load occurred in the month of July 1986, and the second highest in the month of Oct. 1985.

            For the Kallada river the lowest TDS was recorded (32.51 mg/lit) in Dec. 1985 and the highest TDS content coincided with the month of Feb. 1986. The TLS also behave the same way as the TDS, Oct. 1985 has the highest TSS (0.1126 gm/lit).

            Lowest TDS content again coincides with the month of Oct. 1986 for the Achankovil river and the highest with the Sept. 1985. TSS on the other hand registers a lowest value in the month of Feb. 1986 (0.002618 gm/lit) whereas the highest is recorded for the month of Oct. 1985 (0.08262 gm/lit).

            The water discharge is a key factor in deciding the concentration of TDS and TSS in the river water. The monsoonal climate of Kerala causes seasonal rain falls, However, regional and local rains restricted to one or two adjacent basins would alter the pattern of the variation of the TDS and TSS. In the tables (Appendix II) the TLS is not a simple sum of the TSS and TDS. Instead the contents are numerically so low the final values are arrived at after considerable reduction of the figures.

Mineralogy of suspended load

            The routine microscopic analysis is not feasible in the case of suspended load of lakes and rivers. XRD method is ideal for the qualitative assessment of mineralogy. A one cm2 of the filter paper bearing the suspended load was cut and mounted in sample holder of the X-ray diffractometer. The samples were scanned through 40 to 650 for checking the mineralogy. The sediments under transport in the four rivers studied do not differ greatly. Quarts and Kaolinite are ubiquitous in all the samples examined. Feldspar is not noticed in the samples.

            The mineralogy of the suspended load reflects the nature and mineralogy of the soil, and rocks exposed in the catchment of these rivers. It has been pointed out that these river basins do not differ greatly in terms of the rocks exposed. All the basins do expose crystalline rocks. Residual laterite formed from the insitu weathering of the crystalline as well as from the weathering of sedimentary rocks of Tertiary age. The laterite also has been the source of soils that characterise the basins. The Kaolinite is an important alteration product of the crystalline rocks and laterite is a very common alteration product of the crystalline rocks and it is generated by the break down of quarts of the parent rocks.

Concentration of suspended load

            Concentration of suspended load is subject to variation of flow through the seasons as well as from place to place in the same basin. Inter-basin changes in the suspended load is also recognized in many instances. A brief allusion on the variability of suspended load has already been made in an earlier chapter. The causes for variation has been broadly outlined. In the following the modification of suspended load content of the rivers examined are analysed.

            Normally, the suspended load is derived from the soils and rocks that are exposed in the basin. The mineralogy of the suspended load will bear a signature of the rocks and soils of the basin. The seasonality of discharge and its variation surely is reflected in the suspended load content of the samples.

Relation between the various categories of load

            The river load is a function of climate the state of weathering and type of weathering of the rocks in the provenance, the climate of the provenance, the relief of the river basin and the rock types exposed in the river basin. In addition anthropologenic factors like deforestation, land use, damming of rivers and diversion of river water etc. also affect the load.

            The state of Kerala and these rivers in particular fall in the tropical weathering climate with seasonal rainfall, under the influence of the NE and SW monsoons. The chemical weathering that dominates the terrain definitely controls the quantity and nature of the solute through put in these rivers. The average solute content in the four rivers is of the order of 99.53 mg/lit. Chloride, bicarbonate and calcium ion are the most important ones in the waters. Following these, Magnesium, Sodium and Sulfate ions are second in prominence with contents in the threshold of 10 mg/lit. Potassium, Iron and silicon or very low in the waters analysed.

            The average TDS content of these rivers is much lower than that of the major Indian rivers like Ganges, Brahmaputra Krishna, Vauvery or Mahanadi. (Subramonian et al, 1987). The Indian average for TDS is 159 and the average for the rivers under report is 99.53 mg/lit.

            The HCO3 (Alkalinity) and Ca++ content of the Indian rivers are far too high. It is expected because rivers draining lime stone terrains are also included in reckoning the average. The high content of chloride (23.35 mg/lit) Ca++ (17.46) and HCO3 (16.34) can be explained as due to the proximity to the sea and part of it could as well be from the recycling of sea salts. The river basins do not have any source that will provide these ions in large quantities.

            The HCO3/SiO2 ratios for the rivers are given Table 9. The values range between 4 and 8. This ratio is taken as an index of degree of chemical weathering. These rivers enjoy the seasonality of rainfall and a tropical climate which promote chemical weathering.

            Against the expectations, the ratio between the total load supplied (TLS) by the rivers and the total dissolved load (TDS) is very small and most of the time hovers around one and two. This value is an index of the proportion of the TDS in the total load. The low values suggest the predominance of TDS over the TSS. It has been pointed out that the river basins do enjoy a chemical weathering environment, and then it is normal to expect more TDS under transport than TSS.

            The apparent low incidence of suspended load in the rivers examined needs an explanation. Firstly the collection season did not coincide with the peak TSS transport event. Secondly depth integrated samples were not collected. The intention of the study was mainly to examine th solute content of the rivers. However, a cross check on the TSS could be made. However, in the given circumstances it is argued that the TSS content in the rivers are relatively low, for the following reasons. It is principally due to the dominance of the chemical weathering over physical weathering that characterises Kerala. The colour of the water in browns and brownish yellows during the flood season is primarily due to the ubiquitous presence of ferruginous colouring matter and not exactly due to the high content of suspended load.

            It can also be argued that the suspended load is in short supply to the tributaries and main streams because of the paucity of material. We have not yet looked at the state of the art of the soil profile in Kerala. For example, a study in the Neyyar basin (Thrivikramaji, 1986) revealed the fact that many of the soil profiles are truncated and are capped by lag deposits of gravel. The suggestion is that there exists a paucity of erodible material apportionable with the suspended load.

            Thirdly, to some degree the conservation measures implemented form time to time in the various parts of Kerala would have helped in cutting the rate of soil erosion and hence that of the suspended load. The storage of sediment in the channels and flood plains needs to be examined.

            Any how, I strongly feel that a separate study must be undertaken to examine the relation that exists between the suspended load on the one hand and land use, nature of soil series and its susceptibility to erosion, the physiographic aspects and intensity and amount of rainfall on the other.

            Until then one should assume that as the chemical weathering dominates the Kerala scene, the TSS content may remain secondary to TDS.

Summary

            The Vamanapuram, Itykara, Kallada and Achankovil rivers of south Kerala have been studied for the water chemistry (TDS), the suspended load and water discharge. These rivers have many commonalities. For example, the bed rock geology of these river basins are very much similar.

            All these rivers are in the tropical monsoonal climate with a seasonality of rain fall, which is very much conducive to chemical weathering.

            These river basins are comparatively small compared to many of the north Indian rivers. The Ithykara river with 177 km2 basin area is the smallest under investigation, the Kallada river with a basin area 1210 Km2 is the largest of all. The data on discharge for the water year 1985 and part of the water year 1986 are supplied by the Central water Commission.

            The main weakness of the study is that the findings that are reported and discussed here are based on the data for very short period. Normally what is required is a data base that is at least 8 to 9 year long.

            Another point of weakness is that depth integrated samples of water were not collected for this study. It was not undertaken as the intention was to investigate mainly the TDS and its spatial and temporal variations. Further as usual with such studies the collection of samples could not follow the important discharge events that occurred, during the study period.

            The most important advantage of the study is that it has pointed out the need for further efforts in the field of Applied Environmental Geochemistry. It is a field of study that brings out the picture of the pattern of distribution of the elements in the hydrosphere and pedosphere which supply the animals and plants with the nutrients.

            This study has pointed out the following aspects of the river basin processes in Kerala. All the rivers studied, do have dominance of TDS over TSS. This is a clear reflection of the predominantly chemical weathering environment that exists in Kerala.

            The HCO3/SiO2 ratios for the rivers also suggest a preponderance of chemical weathering. The TSS is relatively low compared to many of the Himalayan rivers. But these rivers show similarity with the other peninsular rivers.

            The chloride, soda and calcium content of the waters are relatively higher that the peninsular rivers, and these are considered to be the result of the proximity of the rivers in question to the Laccadive sea. These salts are derived from the sea water in the form of sea spary that is carried on land by sea breeze.

            The river basins are undergoing denudation at a fast rate, as indicated by the average sediment yield (Table 8). The 72 to 227 tonnes (metric) per square kilometer per year of sediment yield is fairly high. But it is not at all comparable to the estimated rate for the Himalayan mountains and rivers.

            The erosion estimates made from load data is only an approximation of the rate of erosion. However, it is nonetheless reliable.

            The suspended load is dominated by minerals like kaolinite and Quartz, normal to a terrain under tropical weathering conditions. The suspended load is related to the discharge. With higher discharge caused by rain fall in the catchment, the suspended load content will increase gradually in these rivers.

            It is also stated that due to the non-availability of discharge data the Karamana River water chemistry was not enquired into. In the case of Neyyar river the studies undertaken and the results there of are reported elsewhere. (Thrivikramaji, 1986).

Recommendations

            As the data collection programme advanced and the analytical data started to emerge, more in sight into the question of importance of this study and such studies happened to unravel. Some of the points, related to the benefit of science as well as of humanity, are included in the following.

  1. As the users increase in number phenomenally and newer avenaces of use are identified water resources have become dearer and scarcer. The increase in the rate deforestation tend to reduce the recharge and seepage but increases surface run off and evaporation losses. This leads to gradual reduction in the volume of underground storage of water.
  2. The study of river geochemistry i.e., the nature and quantum of suspended load and dissolved load of various river basins helped to focus my attention on the question of contamination of water resources, both surface and underground an area yet to attract serious attention in our country.
  3. Contamination can result from man made as well as natural causes. Acid waters originating from a metalliferous mine is one example of natural contamination. A chemical industry releasing untreated effluent into a recharge zone or into a stream not is a good example of anthropogenic cause.
  4. Another man made contaminant is the chemicals that may leak out of underground storages, pipe lines etc. Gasoline is also an important contaminant. In a limited survey it was shown that 20-25% of storage tanks in Canada with the petroleum retailers were found to be leaking; and 10% of the tanks in U.S.A. were found to be leaking. These tanks are made of mild-steel and they tend to develop leaks after an underground life of 15 yr. The leaked product naturally would join the aquifer tending to contaminate the same. The U.S. EPA has classified the benzene and toluene (contents of gasoline) as hazardous, and has set a maximum limit of 0.005 mg/1 in water.
  5. Therefore even small contents of gasoline in water can make it unfit for concumption. For example benzene constitutes about 1 to 2 percent of gasoline. Using the US drinking water standard as a criterion, one liter of gasoline has the potential to contaminate 4 million litres of ground water. In fact the situation in India should be very much similar to what exists in Europe, U.S.A. and Canada.
  6. The available data on the chemistry of soils, rocks and surface and underground water should be gathered and analysed to see whether there are any anomalous concentrations of natural elements in any one of these earth spheres. We have known that some of the elements are essential for the humans, plants and animals, whereas many others are detrimental to life. Once the data are analysed, the concentration of the elements can be converted into thematic maps and atlases for ready consultation by the people engaged in the health care planning and industry. Wherever, data are lacking new programmes for data collection can be launched to augment, check and supplement the archival data. This branch of study is called Applied Environmental Geochemistry.

Table 1. Sediment yields from catchments of differing landuses (Douglas, 1989)

Region Forested Sediment yield (M) (m3 Km–2 year–1) Cultivated
Northern range 1.8 16.0
Barron, Queensland 5.7 13.6
Mbeya range, Tansania 6.9 29.5
Cameron Hill, Malayasia 21.1 103.1
Apiodoum, Ivory coast 97.0 1700.0
Tjiloetoeng, Java 900.0 1900.0

Table 2. Denudation rate of Indian rivers (modified after subramonian, 1979)

Basin Denudation rate (104 kg km–2 yr–1)
Cauvery 86.4 tonnes
Krishna 118.3 tonnes
Godavari 137.3 tonnes
Narmada 193.3 tonnes
Tapti 127.2 tonnes
Mahanadi 93.8 tonnes
Ganges 724.8 tonnes
Brahmaputra 978.0 tonnes
India (Total) 407.0 tonnes

Table 3.  Composition of average Indian and World river waters, concentration in ppm (modified after Subramonian, 1979)

Component Average Indian river Average World river
Ca+2 23.08 15.0
Mg+2

Na+3.736.3K+2.322.3HCO390.7758.4SO4–211.3811.2C16.287.8SiO214.7313.1TDS              159.0120.0

Table 4. Variation of load, Vamanapuram Ar. at Ayilam

1 2 3 4 5 6 7 8
TSS 0.00878 0.8155 0.1574 0.00853 0.00414 0.2098 0.03217
TDS 57.7 86.3 40.3 63.61 84.58 61.70 48.01
TLS 0.066448 0.16785 0.05604 0.07214 0.08872 0.08268   0.08018

Table 5. Variation of load, Ithykkara Ar. at Ayur

Load 1 2 3 4 5 6 7
TDS 89.6 96.8 69.7 74.6     435.24 89.29 61.24
TSS 0.01373 0.1694 0.00374 0.00439       0.01534 0.03422 0.01598
TLS 0.10333 0.2662 0.07344 0.07899 0.45048 0.12351 0.7722

Table 6. Variation of load in Kallada Ar. at Pattazhi

Load 1 2 3 4 5 6 7
TDS 93.8 92.3 32.51 350.15 88.57 57.35 61.25
TSS 0.006348 0.1126 0.00863 0.002646   0.023 0.02115       0.01709
TLS 0.100143 0.2049 0.04114 0.3501       0.11157 0.0785     0.07834

Table 7. Variation of load in Achankovil Ar. at Thumbamon

Load 1 2 3 4 5 6 7
TDS 89.3 88.2 82.99 68.50       54.22 53.21 83.74
TSS 0.007285 0.08262 0.00485 0.002618 0.01534 0.02110 0.02464
TLS 0.096585 0.17082 0.08784 0.07111 0.06956 0.04731 0.10838

TDS = Total dissolved load, in mg lit–1

TSS = Total suspended sediment, in gm lit–1

TLS = Total load supplied, in gm lit–1

1 = Sept. 1985; 2 = Oct. 1985; 3 = Dec. 1985; 4 = Feb. 1986;

5 = July 1986; 6 = Oct. 1986; and 7 = Nov, 1986.

Table 8. Sediment yield of South Kerala Rivers

River Basin area, Km2 Sediment yield Ton Km–2
Water yr. 1985 Water yr.1986
Vamanapuram 867 72.4 87.57
Ithykkara 642 115.5 118.04
Kallada 1919 227.2 N.A.
Achankovil 1484 146.75 140.01

N.A. Not available

Table 9. Average composition of the water at the gauges (in mg/lit)

Component Ayilam Ayur Pattazhi Thumbamon Average
Ca+2 6.57 34.17 21.28 7.85 17.40
Mg+2 2.02 27.01 9.94 2.15 10.28
Na+ 8.42 14.18 11.57 7.2 10.34
K+ 1.85 2.28 3.33 1.14 2.15
HCO3 14.88 16.77 17.39 16.35 16.34
SO4-2 6.93 12.73 11.55 15.96 11.79
C1 18.8 22.48 33.55 26.60 25.35
SiO2 3.55 2.61 2.78 1.48 2.44
Fe++ 1.9 4.28 2.13 1.48 2.44
NO3 0.45 0.95 0.66 0.71 0.69
Total TDS 65.37 137.46 114.18 81.26 99.53
 

 4.196.426.258.9

Table 10. Ratios of total load to dissolved load in the rivers for Ayilam, Ayur, Pattazhi and Thumbamon.

Data Date Ayilam Ayur Pattazhi Thumbamon
Sept. 1985 1.14 1.14 1.06 1.07
Oct. 1985 1.94 2.76 2.23 1.93
Dec. 1985 1.39 n.d 1.25 1.04
Feb. 1986 1.12 n.d 1.0 1.02
July 1986 1.04 1.03 1.26 1.27
Oct. 1986 1.32 1.38 1.36 1.39
Nov.1986 1.66 1.24 1.27 1.28
Average 1.37 1.51 1.34 1.28
Grand Average = 1.37

 

Table 11. Some rates of Regional erosion (Menard 1961)

1 0.55/ton/acre/yr. =   153.85 ton/km2/yr =  51.264 m3/km2/yr
2 0.50/ton/acre/yr.  =   123.5     – do–   =   46.6     –do–
3 0.74   –do– =   182.0     –do–   =   68.67   –do–
4 0.10   –do– =   247.0     –do­–   =     9.32   –do–
5 2.62   –do– =   647.14   –do–   =  244.2    –do–
6 12.00   –do– = 2964.0     –do–   =  118.49   –do–
  1. a) Geologic and present deposition rates in the Missippi basin are nearly equal (1 and 2)
  2. b) Deposition rates in the Appalachian regionain the geologic time (3) and present time (4).
  3. c) Geologic deposition rates in the Himalayan region (5) and present day (6).

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Reference

  1. Anonymous, 1974, Water Resources of Kerala, 110 p.
  2. Chorley, R.J., Schumm, S.A., and Sudgen, D.E. 1984, Geomorphology, London, Methuen, 605 p.
  3. Colby, B.R. 1963, Fluvial sediments – A summary of source, transportation, deposition and measurement of sediment discharge: U.S. Geological Survey Bulletin, 1181-A, 49 p.
  4. Douglas, Ian, 1967, Man, Vegetation and sediment yields of rivers: Nature, 215, 925-928
  5. Geikie, A, 1868, On denudation now in progress: Geol. Mag., 5, 249-54
  6. Gibbs, R.J., 1967, Geochemistry of the Amazon River system: Bull. Geol. Soc. American, V. 78, P. 1203-1212.
  7. Hem, J.D., 1970, Study and interpretation of the chemical characteristics of natural water, 2nd Ed., U.S. Geological Survey Prof. Paper, 1473, 363 pp.
  8. Livingstone, D., 1963, Chemical composition of rivers and lakes of the world: U.S. Geological Survey Prof. Paper 440G, 64 p.
  9. Meade, R.H., 1987, Movement and storage of sediment in river systems: in Lerman, A., and Mayback, M, (ed.) Physical and Chemical Weathering in Geochemical Cycles: Reidel Publishing Co., Dordrecht, Netherlands.
  10. Schrmm, S.A. 1977, Fluvial system, New York, John Wiley and sons, 338 p.
  11. Soman, K., 1980, Geology of Kerala, CESS Prof. Paper, Trivandrum, 61 p.
  12. Subramonian, V., 1979, Chemical and suspended sediment characteristics of Rivers of India: Jour. Hydrology, V. 44, p. 37-55
  13. Thrivikramaji, K.P., 1986., River Metamorphosis due to Human Intervention in the Neyyar Basin, Kerala, Final Technical Report to Department of Environment and Forests, Govt. of India, New Delhi.

Appendix – I

  1. Sampling sites
  2. Collection schedule
  3. Important river basins of Kerala
  4. Principal natural sources of dissolved load in Rivers
  5. Mean basin area and mean denudation rate
  6. Discharge data for the rivers

Appendix – II

  1. Sediment yields from catchments of differing landuses
  2. Denudation rate of Indian river basins
  3. Composition of average Indian and World river water
  4. Variation of load, Vamanapuram Ar. at Ayilam
  5. Variation of load of Ithykara Ar. at Ayur
  6. Variation of load of Kallada Ar at Pattazhi
  7. Variation of load of Achankovil Ar at Thumbamon.
  8. Sediment yield of South Kerala Rivers
  9. Average composition of water at the gauges
  10. Ratios of total load to dissolved load at the gauges
  11. Some rates of regional erosion.

Appendix – III

Physical properties and chemical composition of water samples.

 

Table  Sampling sites

River basin Site Gauge site
Vamanapuram Ar. Kollampuzha

Ayilam

Mylamoodu

PalodeAyilamIthykkara Ar.Ithykkara

Peringallur

AyurAyurKallada Ar.Kdapuzha

Pattazhi

KandamchiraPattazhiAchenkovil Ar.Cherukol

Thumpamon

KonniThumpamon

Table Collection schedule

September, 1985
October, 1985
December, 1985
February, 1986
July, 1986
October, 1986
November, 1986

 Table Important River basins of Kerala (Anonymous, 1974)

No. Basin Name Length Basin

Area, Km2Average Annual yield Mm21Periyar244539811, 6072Bharathapuzha209618874783Pamba176223546414Greater Chaliyar169476577595Chalakudi130170431216Achenkovil130148422877Muvattupuzha121200438148Kallada121191922709Valapattanam1101867409210Chandragiri10515383964

Table  Principal natural sources of dissolved Load in rivers (modified after Janada, 1971)

Denudation components Non-denudation components
A-Terrestrial sources B-Non-Terrestrial sources
Rock Soil dust
Soil Cyclic salts
Alluvius Gases
Connate water
Volcanic material

Table  Mean basin area and mean denudation rate

Basin area, Km2 Mean denudation rate, mm/1000 year
0.3 12,600
3.0 25,50
80.0 220-60
3,900 100-30
37,000-3,280,000 60-30

Table 1

No. Date of Collection Location River Temp 00C pH E.C. (M mohs) Dissolved (ppm) oxygen
1 19-9-85 Kollampuzha Attingal Ar 29.75 7.3 3.85 ´ 1000  3.0
2 19-9-85 Ayilam Attingal Ar  33 7.2 4.6 ´ 10 2.75
3 19-9-85 Mylamoodu Attingal Ar 31 7.25   3.3 ´ 10 2.6
4 19-9-85 Palode Attingal Ar 30.5 7.25   3.3 ´ 10 2.5
5 19-9-85 Kandamchira Kallada Ar 26 7.3   3.3 ´ 10 3.0
6 20-9-85 Peringallur Ithikkara Ar 27 7.1   5.9 ´ 10 4.0
7 20-9-85 Ayurgauge Ithikkara Ar 28 7.2   5.6 ´ 10 4.5
8 20-9-85 Ithikkara Ithikkara Ar 30 7.2   1.6 ´ 100 2.6
9 20-9-85 Kadapuzha Kallada Ar 30 7.2 8 ´ 10 3.0
10 20-9-85 Pattazhi Kallada Ar 28 7.4 5 ´ 10 5.25
11 20-9-85 Konni Achancovil Ar 31 7.2   4.5 ´ 10 6.5
12 21-9-85 Thumbamon Achancovil Ar 30 7.4   4.8 ´ 10 3.2
13 21-9-85 Cherukol Mavelikkara Achancovil Ar 31.5 7.4   5.6 ´ 10 2.0

Table 2

Estimation of Ions (Dissolved Solids in PPm)

No. HCO3 Cl NO3 SO4 N Na++ K+ Ca++ Mg++ Fe++ SiO2 Mu TDS in mg/lit Suspended gm/lit Total load gm/lit  
1 26 1033 485 842.5 28 102 104       0 4.9 2625.4 0.004033 2.629435
2 16 14 3 5.5 4 8 0.4 0.5 6.3 57.7 0.008748 0.066448 Ayilam
3 17 21 16 5.3 3 6    1       5    4 78.3 0.01112 0.08942
4 14 17 3      5 1 5    2 5.5 2.5         55 0.007150 0.062150
5 12 14 14      5 3 10 0.4 1.5 2.9 62.8 0.005719 0.068519
6 20 21 24 7.5 3 7    1       6 5.3 94.8 0.01640 0.11120
7 19 26 16 7.3 3 6    2 7.2 3.1 89.6 0.01373 0.10333 Ayur
8 20 62 43 19.8 3 6    4 0.5    5 163.3 0.004498 0.167798
9 16 43 22 7.6 2 9 0.1      1 4.7 105.4 0.004239 0.167798
10 21 18 28      5 4 9    1      4 3.8 93.8 0.006348 0.100148 Pattazhi
11 20 16 24 5.1 2 5    2 0.5 2.6 77.2 0.002561 0.079761
12 18 16 35      5 2 9    1 1.5 1.8 89.3 0.007285 0.096585 Thumbamon
13 17 14 22      5 1 10    1       2 1.2 73.2 0.005987 0.079187

Table 3

No. Date of Collection Location River Temp 00C pH E.C. (M- Mohs) Dissolved oxygen (ppm)
1 28-10-85 Kollampuzha Attingal Ar 26.75 7.1 4.7 ´ 10 6.00
2 28-10-85 Ayilam Attingal Ar  26.8 7.2       3.3 ´ 10 4.50
3 28-10-85 Mylamoodu Attingal Ar 26.8 771       2.9 ´ 10 4.25
4 28-10-85 Palode Attingal Ar 26.9 6.75       3 ´ 10 3.75
5 28-10-85 Kandamchira Kallada Ar 25 7.1       6.8 ´ 10 3.60
6 29-10-85 Peringallur Ithikkara Ar 26 6.6       3.5 ´ 10 5.00
7 29-10-85 Ayurgauge Ithikkara Ar 26.2 6.7       3.8 ´ 10 5.25
8 29-10-85 Ithikkara Ithikkara Ar 27.5 6.9       4.3 ´ 10 5.50
9 29-10-85 Kadapuzha Kallada Ar 28 6.5       4.25 5.20
10 20-10-85 Pattazhi Kallada Ar 27.5 6.6 3.7 ´ 10 5.00
11 29-10-85 Konni Achancovil Ar 27.5 6.3       3.5 ´ 10 5.00
12 30-10-85 Thumbamon Achancovil Ar 26 6.6       3 ´ 10 4.50
13 30-10-85 Mavelikkara Cherukol Achancovil Ar 26.4 6.8       3 ´ 10 4.00

Table 4

Estimation of Ions (Dissolved Solids in PPm)

No. HCO3 Cl NO3 SO4 Na++ K+ Ca++   Mg++ Fe++ Mu++ TDS in mg/lit Suspended gm/lit Solid Total load gm/lit
1 114 39 0.5 30 1.4 8 9    5 6 4 129.5 0.05982 0.18932
2 4 20 0.1 31     7 1 8 5   3 7.2 86.3 0.08150 0.16785
3 8 24 0.9 37     7 2 6    4 3.2 8 100.1        0.02869 0.12579
4 12 18 0.3 30 6 1 11    2 2.9 5.1        88.3 0.02455 0.11285
5 14 14 0 32 9 1 7    3 2.4 5.9 88.3 0.01142 0.09972
6 5 31 1 32     12 2 6    2 2.7 4 97.7        0.09436 0.19206
7 12 10 1.2 31     14 4 10    1 9.1 4.5 96.8        0.1694 0.2662
8 11 66 1 28     16 2 7    2 6 6      145        0.1670 0.312
9 15 28 1.1 45     14 3 8    2 2.7 3.6 122.4        0.1266 0.249
10 13 15 0.5 32     10 2 7    3 8.9 6.9 92.3        0.1126 0.2049
11 19 45 1 41     12 2 7    3 1.9 3 129.9        0.1468 0.2767
12 11 26 0.3 23 9 1 7    6 2.7 2.2 88.2 0.08262 0.17082
13 14 34 0 22 9 1 9    1 2.1 5 97.1 0.07463 0.17173


 

 

 

 

Table 5

No. Date of Collection Location River Temp (00C) pH E.C.
1 30-12-85 Kollampuzha Attingal Ar  28 7.15
2 30-12-85 Ayilam Attingal Ar  28 7.1 4.2 ´ 10
3 30-12-85 Mylamoodu Attingal Ar 26.8 7.15 3.9 ´ 10
4 30-12-85 Palode Attingal Ar 26.8 7.05 3.1 ´ 10
5 30-12-85 Kandamchira Kallada Ar 25.8 7.2 3.6 ´ 10
6 31-12-85 Peringallur Ithikkara Ar 24.4 7.05 5.6 ´ 10
7 31-12-85 Ayurguage Ithikkara Ar 24.8 7.1 5.6 ´ 10
8 31-12-85 Ithikkara Ithikkara Ar 26.5 6.9 1.41 ´ 1000
9 31-12-85 Kadapuzha Kallada Ar 27.5 7.4 2.9 ´ 100
10 31-12-85 Pattazhi Kallada Ar 26.6 7.9 4.8 ´ 10
11 31-12-85 Konni Achancovil Ar 28.2 7.3 4.95 ´ 10
12 1-12-86 Thumbamon Achancovil Ar 26 6.85 4.65 ´ 10
13 1-12-86 Cherukol Mavelikkara Achancovil Ar 28 6.9 5.35 ´ 10

Table 6

Estimation of Ions (Dissolved Solids in PPm)

No. HCO3 Cl NO3 SO4 Na++ K+ Ca++ Mg++ Fe++ SiO2 Mu++ TDS in mg/lit Suspended gm/lit Total load gm/lit
1 3.21 634 0.1 20 14 97  150 4.3 1 1.1 924.71 0.01512 0.93983
2 1.30 14.9 0.2 1.5 10 2 5.0   1.2 1.2 3.0      40.3 0.01574 0.05604
3 1.19 14.0 0.7 3.15 10 2 2.6 3.2 2 3.2 42.04 0.00798 0.05002
4 1.05 15.1 0.4 2.0 9 2 3.0 1.8 0.6 2.0       36.95 0.01238 0.04933
5 1.07 16.0 0.5 3.45 88 2 1.8 3.6 2.2 2.1 40.72 0.01064 0.05136
6 1.60 26.0 0.5 1.6 13 2 4.0 1.8 4.0 3.0 57.5 0.00485 0.06235
7 1.50 35.2 0.9 1.6 14 3 5.0 2.1 2.6 3.8 69.7 0.00374 0.07344
8 1.34 39.0 0.2 NIL 12 26 18.0 2.7 0.6 1.2     101.04 0.00860 0.10964
9 1.38  101 0.5 NIL 57 8 9.8 3.2    NIL 0.5   181.38 0.00622 0.1876
10 1.46 7.8 0.4 1.15 8 4 6.0 2.4 0.6 0.7 32.51 0.00863 0.04114
11 1.40 22.3 0.6 1.05 8 2 5.6 2.4 1.0 3.0 47.35 0.00528 0.05263
12 1.44 53.5 0.8 2.65 9 1 8.0 8.8 1.2 2.6 82.99 0.00485 0.08784
13 1.14   37 0.9 1.3 10 1 7.4 2.7     NIL 0.7 62.14 0.01399 0.07613

 

Table 7

No. Date of Collection Location River Temp (00C) pH E.C.
1 28-2-86 Kollampuzha Attingal Ar  29 7.0 7.5 ´ 10
2 28-2-86 Ayilam Attingal Ar  29.8 7.2 7.4 ´ 10
3 28-2-86 Mylamoodu Attingal Ar 29.6 7.3 4.8 ´ 10
4 28-2-86 Palode Attingal Ar 28.8 7.4 4.0 ´ 10
5 28-2-86 Kandamchira Kallada Ar 2 6.9 4.5 ´ 10
6 1-3-86 Peringallur Ithikkara Ar 26.8 6.8 6.4 ´ 10
7 1-3-86 Ayurguage Ithikkara Ar 26.6 7.3 6.9 ´ 10
8 1-3-86 Ithikkara Ithikkara Ar 28.6 6.8   4 ´ 100
9 1-3-86 Kadapuzha Kallada Ar 32.2 7.55 10 ´ 1000
10 1-3-86 Pattazhi Kallada Ar 30.6 7.15 6.6 ´ 10
11 1-3-86 Konni Achancovil Ar 30.6 7.45 6.7 ´ 10
12 1-3-86 Thumbamon Achancovil Ar 32 7.6 5.7 ´ 10
13 1-3-86 Cherukol Mavelikkara Achancovil Ar 31.4 8.05 4.1 ´ 10

Table 8

Estimation of Ions (Dissolved Solids in PPm)

No. HCO3 Cl NO3 SO4 Na++ K+ Ca++ Mg++ Fe++ SiO2 Mu++ TDS in mg/lit Suspended gm/lit Total load gm/lit
1 26.77 550 0.2 60 180 17 480 140 Nil 0.9 1454.87 0.00822 1.46309
2 18.11 15.1 0.4 1.8 17 2 6.0   1.2 Nil 2.0   63.61 0.00853 0.07214
3 17.64 13.1 0.6 2.0 12 3 3.8 2.2 Nil 1.8 55.61       0.00476 0.05985
4 23.64 12.1 0.8 3.6 10 2 2.4 2.6 Nil 1.6 58.54 0.00364 0.06218
5 9.2 14.0 0.4 4.2 9 1 5.6 3.0 Nil 1.6 48.00 0.00186 0.04986
6 20.9 21.2 0.5 3.2 18 2 3.0 2.4 Nil 1.8 72.10 0.00349 0.075148
7 22.5 18.2 0.9    Nil 20 3 6.0 1.5 1.0 1.5 74.60 0.00439 0.07899
8 18.4 150    Nil Nil 78 7 300 120 0.5 0.8 674.70 0.004569 0.67927
9 65.3 9000 0.5 4.6 720 109 600 180 2.0 0.3  12681.7 0.002732 10.6844
10 22.3 140 0.6 1.25 20 4 100 60 1.0 1.0 350.15 0.002646 0.35015
11 25.3 196 0.9 2.45 13 1 9.6 1.6    Nil 1.6 75.05 0.006030 0.081080
12 25.1 14.4 0.9 1.6 14 1 7.6 2.4 0.5 1.0 68.50 0.002618 071118
13 14.3 17.2 0.9 1.2 9 1 4.8 2.2 1.0 0.8 52.40 0.00373 0.056130

 

 

 

 

 

 

 

 

 

 


Table 9

No. Date of Collection Location River Temp (00C) pH E.C.
1 July 1986 8.20 6.1 ´ 10
2 8.49 5.2 ´ 10
3 8.16 6.0 ´ 10
4 7.60 4.5 ´ 10
5 7.45 8.0 ´ 10
6 7.31 4.8 ´ 10
7 7.99 3.1 ´ 10
8 7.64   1.5 ´ 100
9 5.76 2.0 ´ 1000
10 8.48 5.2 ´ 10
11 8.24 8.0 ´ 10
12 8.20 3.2 ´ 10
13 8.02 4.5 ´ 10
7.67 6.6 ´ 10

Table 10

Estimation of Ions (Dissolved Solids in PPm)

No. HCO3 Cl NO3 SO4 Na++ K+ Ca++ Mg++ Fe++ SiO2 Mu++ TDS in mg/lit Suspended gm/lit Total load gm/lit
1 15.31 623 0.4 20 36 4 460 230 0.5    1   1372.21 0.00157 1.37378
2 31.08 35.2 0.8    Nil 5.5 2 4.0 3.6 2.4 84.58 0.00414 0.098720
3 20.40 13.1 0.6 3.0 4.0 1 3.6 2.4 1.8 49.90 0.00726 0.05715
4 19.13 8.75 0.8 1.9 5.0 0.5 5.8 2.4 1 1.6 46.08 0.00460 0.050680
5 17.85 17.6 0.6 3.5 3.0 2 5.6 1.2 2.0 53.35 0.00119 0.054540
6 24.23 11.9 0.5 2.0 8.0 5 5.0 3.2 0.5 1.6 61.93 0.00245 0.064380
7 23.94 17.6 0.9    Nil 9.0 2 200 180     – 1.8 435.24 0.01534 0.45058
8 18.11 210    Nil 30 0.8 250 240     – 1.0 749.91 0.00800 0.75791
9 77.02 7000 0.6    Nil 70 10 110 120     1 0.4    7389.02 0.00270 7.39252
10 27.04 16.63 0.8 1.5 24 5 9.6 3.0     –     1 88.57 0.02300 0.11157
11 26.48 10.5 1 0.5 6.0 2 8.8 2.6     – 0.7 56.58 0.02882 0.08540
12 18.57 16.45 0.9 1.6 5.0 1 8.4 0.6     – 1.4 54.22 0.01534           0.06956
13 7.90 13.1 0.8 105 4.0 Nil 7.2 1.5    0.5 1.5 37.55   0.00900           0.04655
   1 2.5

Table 11

Estimation of Ions (Dissolved Solids in PPm)

No. HCO3 Cl NO3 SO4 Na++ K+ Ca++ Mg++ Fe++ SiO2 Mu++ TDS in mg/lit Suspended gm/lit Total load gm/lit
1 19.40 625 0.8 16 20 2 284 56 0.5 1.0 1032.7 0.01556 1.04826
2 17.90 20.2 0.6 2.8 8 1 9.2 1.2    Nil 1.6        61.70 0.02098 0.08268
3 22.50 14.9 0.7 1.7 6 3 7.6 1.3    Nil 1.8       59.50 0.007101 0.066601
4 16.06 16.63 0.5 2.25 7 Nil 8.2 2.3    Nil 0.8        53.74 0.02038 0.07412
5 16.84 9.27 1.0 1.55 5 1 7.8 1.1    Nil 0.9       44.46 0.009174 0.05364
6 23.74 33.4 0.6    Nil 10 2 4.6 2.8    Nil Nil       77.72 0.02098 0.09818
7 23.94 40.25 0.8 0.5 14 1 6.0 1.0   1 0.8       89.29 0.03422 0.12351
8 17.64 36.9 0.9 11 28 3 560 44    Nil 1.0      701.54 0.01154 0.71893
9 23.21 490 0.8    Nil 18 Nil 161 21    Nil 0.8      717.81 0.01739 0.73520
10 20.15 19.6 1.1 2.9 7 1     9.0 2.4    0.5 Nil     57.35 0.02115 0.07850
11 20.66 14.0 0.5 1.8 8 Nil 7.2 2.0    Nil 1.5     55.26 0.01891          0.07419
12 20.41 10.9 1.0    Nil 7 2 8.0 1.1    Nil 1.8    43.21 0.02110 0.07431
13 16.32 15.1 0.8 1.3 9 Nil 10.0 0.8    0.5 2.0    55.82   0.01228 0.06810

Table 12

Estimation of Ions (Dissolved Solids in PPm)

No. HCO3 Cl NO3 SO4 Na++ K+ Ca++ Mg++ Fe++ SiO2 Mu++ TDS in mg/lit Suspended gm/lit Total load gm/lit
1 25.51 61.25 0.8 2.55 25 2 420  160 4 2.0 703.11 0.01977 0.72288
2 15.81 12.30 0.6 1.50 6 1 5.8    1.6 1 2.4      48.01 0.03217 0.08018
3 17.34 16.28 0.4 2.55 8 3 11.2    3.8 1.5 2.5 66.57 0.01939 0.08596
4 11.48 13.13 1.5 0.55 12 4 6.2    2.2 0.8 1.5     53.36 0.015044 0.068404
5 10.21 9.88 1.7 0.90 10 1 7.2    1.1 0.6 1.0 44.59 0.01088 0.05547
6 21.42 12.60 0.7 1.45 9 8.0    1.1 2.2 2.8 59.27 Kg–Kg 1526 0.07453
7 14.54 10.15 1.0 1.85 21 1 6.2    1.5 1.5 2.5 61.24 0.01598 0.07722
8 14.03 31.52 1.7 3.35 12 2   11.0    1.2 1.0 2.4     80.20 0.02477 0.10497
9 16.32 21.00 1.5 2.30 10 1     9.6    0.9 4.0 1.5     68.12 0.01047 0.07859
10 16.84 17.85 0.6 2.50 7     1.2    0.8 3.8 1.2 61.25 0.01709 0.07834
11 18.62 16.85 0.7 0.85 9 3     8.0   0.24 1.0 2.8 61.02 0.01489 0.07591
12 19.63 49.01 0.4 3     7.0 1.2 1.5 2.0 83.74 0.02464 0.10838
13 12.24 21.35 0.3 1.25 5     7.6 2.1 0.6 2.2 52.64 0.02411 0.07675
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