Academic literature on the topic 'Cauvery River basin'

Delta regions of the Cauvery River basin are one of the significant areas of rice production in India. In spite of large-scale utilization of the river basin for irrigation and drinking purposes, the lack of appropriate water management has seemingly deteriorated the water quality due to increasing anthropogenic activities. Vellore is the second most populous district of Tamil Nadu in India where the Palar River flowing towards east for about 295 Km. Vellore is surrounded by many leather tanneries and small scale dying industries and their effluents are discharged into the Palar river causing impact on the quality of the underground water. To assess the extent of deterioration, physicochemical characteristics of surface water were analyzed select regions of Cauvery Delta River basin and Palar region, Tamil Nadu, during March 2016 to May 2016. This study aimed to examine quality of drinking groundwater. The results represented whether the water was suitable or unsuitable for drinking purposes in this area. It was also observed that some areas like Tiruvarur, Needamangalam, Kamalapuram, Arcot, Soraiyur, Ranipet had low quality drinking water. It is suggested to take some necessary measures for supplying desirable water to the people living in these areas.

India is facing major challenges in its water resources management (WRM) sector. Water shortages are attributed to issues such as an explosion in population, rapid urbanization and industrialization, environmental degradation and inefficient water use, all aggravated by changing climate and its impacts on demand, supply and water quality. This paper focuses on the contemporary and future situation in the Cauvery river basin in Southern India, shared by different states, predominantly Karnataka and Tamil Nadu. As water issues largely fall under the authority of the states, inter-state water disputes have a long tradition in the Cauvery river basin. Future changes in precipitation during the two monsoon seasons will only increase these tensions. Both states depend on the arrival of these monsoon rains to water their crops and to replenish the groundwater. The paper identifies the major challenges and general possible solutions for sustainable WRM within the river basin. It synthesises the relevant literature, describes practices that should be addressed in the scope of integrated WRM – including water availability increase and demand management – and stresses the need for further quantitative analyses.

Fifty years after the first report of freshwater medusae (Limnocnida indica) from Cauvery River in Krishanrajasagar Reservoir, there has been only one other published report of its occurrence in the Cauvery Basin at Hemavathi Reservoir, Kodagu District. Recent interest in freshwater photography has revealed three more locations in the Cauvery Basin where medusae are found. Medusae are often observed at these locations but are erroneously identified as invasive species. According to published literature, this is true of Craspedacusta sowerbii, a cosmopolitan species with only three confirmed reports from India. All these reports were from artificial structures such as ponds and aquaria. The native Limnocnida and exotic Craspedacusta can be distinguished from each other visually and with respect to temporal variation in the occurrence of their free swimming medusae. This short note is intended to shed light on the status, distribution, and field identification of L. indica, a species endemic to the Western Ghats of India.

Climate change assessment at a local scale requires downscaling of general circulation models (GCMs) using various approaches. In this study, statistical downscaling using established machine learning techniques is compared with the proposed extreme gradient boosting decision tree (EXGBDT) technique. The Cauvery river basin in southern peninsular India, which is known for its frequent droughts and floods, was considered in this study. The ACCESS 1.0 CMIP5 historical GCM simulation was used for downscaling the local climate with the help of daily observation data from 35 stations located in the study zone. An intercomparison of model performance in predicting daily weather variables such as precipitation and average, maximum, and minimum temperatures over the upper, middle, and lower Cauvery river basin was performed. The findings show that mean-variance is around 15% and bias is negligible for the proposed EXGBDT model, which is better than other models under consideration. The NSE and R2 values range from 0.75-0.85 for both training and testing periods. The intercomparison of monthly mean values of observed and downscaled data for different sub-basins and parameters suggests higher model efficiency. The lower variance observed in the comparison of CLIMDEX indices suggests that the EXGBDT model performance is better in representing the local climatic condition.

Surface water and groundwater interactions are inherently complex because they occur across a range of spatial and temporal scales. This thesis envisages to improve our understanding of surface water and groundwater in the partially natural and human influenced environment of the Cauvery River Basin (CRB), which will contribute towards a better and efficient managing of water resources in a sustainable way. The primary objective of the thesis is to solve some open ended questions pertaining to the seasonality of stable isotope (δD, δ18O) variation within the Cauvery River Basin (CRB) with the aim to characterize the relative contribution of surface water and groundwater to the streamflow by using a two-component mixing model. Secondary objective is to evaluate the sources of dissolved inorganic carbon isotope (δ13CDIC) ratios of the Cauvery River and its tributaries within the CRB where the lithology is dominated by a silicate basement in the upper and middle reaches and a carbonate basement in the lower reaches. The study also investigates the major-ion chemistry of river water to quantify the silicate weathering rates (SWR) within the Cauvery River Basin (CRB) over spatial and temporal scales. Sampling was done from 2014 to 2016 which resulted in six seasonal datasets of river water along with measurement of groundwater (GW) composition, comprising of three seasonal datasets. The stable isotope (δD, δ18O) measurement recorded a negative seasonal shift in the river water isotopic composition of 8‰ for δD and 0.95‰ for δ18O between Pre-Monsoon (PM) and South-West Monsoon (SWM) seasons which can be ascribed due to different moisture iii sources during the SWM season and enhanced evaporation from the KRS reservoir during the PM season. The results from the two-component mixing model suggest that groundwater contribution to the stream flow during the PM season was ~57 ± 4% whereas surface runoff serves as the primary component with ~53 ± 7% contribution during the SWM season. The seasonal patterns were distinct with the PM season recorded lighter δ13CDIC value of −9.9 ± 2.8‰ and the SWM season with relatively heavier δ13CDIC value of −5.1 ± 2.0‰. This large seasonal variation (≈4.8‰) in the dissolved inorganic carbon isotope composition (δ13CDIC) of the Cauvery River is due to the release of CO2 with charnockite degassing in the headwater region. However, in the lower reaches of the Cauvery River dissolution of carbonate minerals still occurs due to high runoff during the SWM season. Published datasets were used for atmospheric and anthropogenic corrections were applied to the major ion datasets. Atmospheric deposition can either be in the form of wet (rainfall) or dry (dustfall) whereas anthropogenic correction was applied to negate the effect of anthropogenic induced pollution levels which are higher in the semi-arid zone of the Cauvery Basin including the excess contribution of Cl- and Na+ ions from salt affected saline soils. It was observed that sodium (Na+) was the dominant ion (in meq/l) during the PM season whereas bicarbonate (HCO3 -) was the dominant ion during SWM season followed by magnesium (Mg2+) and calcium (Ca2+). Silicate weathering rates (SWR) in the Cauvery River Basin and its flux to the ocean also varied seasonally as well as along the stream length. A iv gauging site at Kudige, located in the Western Ghats recorded high SWR of 11.48 ± 0.15 t/km2/y and 45.43 ± 1.57 t/km2/y during the PM and SWM season respectively whereas, terminal site at Musuri, located near the Cauvery delta recorded SWR of 2.83 ± 0.22 t/km2/y and 5.94 ± 0.09 t/km2/y during the PM and SWM respectively. These high silicate weathering rates especially during the SWM can be explained by the proximity of the gauging site to Western Ghat Mountains which record high rainfall and runoff, large diurnal temperature variability and lush vegetation, are the factors that contribute towards intense silicate weathering in the Western Ghats.
Ministry of Earth Sciences (MoES)

In the recent times, changes are noted in hydrological processes (e.g., surface runoff, lateral flow, infiltration, return flow, evapotranspiration, soil moisture and streamflow) in different river basins of the world due to the impact of climate and land-use/land-cover (LULC) changes. In upper Cauvery river basin considerable changes has been noticed in the cropping pattern over the past few decades. It is also witnessed that the farmers in the region often expand plantation by encroaching into forest and grassland. In this context, there is a need to assess the combined as well as individual impacts of climate and LULC changes over hydrological processes in the area. There is dearth of such attempts in India, and this is the first study of its kind in the Cauvery basin. In this thesis, future projections of meteorological variables (viz., rainfall, temperature, wind speed, humidity, and solar radiation) were obtained for Hemavathi catchment in upper Cauvery basin by downscaling simulations of BCC (Beijing Climate Center) GCM and CORDEX REMO RCM (Regional Climate Model) for AR5 (Fifth Assessment Report) climate change scenarios by using multiple change factor methodology. Accurate information on hydromorphic parameters (e.g., watershed boundary and stream network) is necessary to develop a hydrological model. Conventionally, the hydromorphic parameters are derived from satellite based DEMs which are currently available in different resolutions. Hence need for identifying appropriate DEM(s) for use in the study is realized. In this thesis, accuracy of different DEMs (i.e., SRTM, ASTER, CARTOSAT, TopoDEM) was assessed on the upper Cauvery river basin, considering catchment of Yagachi river as a representative area. Finer resolution DEMs are expected to be better in representing the morphology and topography of catchments. But the present study reveals that coarser (90 m) resolution SRTM DEM is better than the finer (30 m) resolution DEMs (CARTOSAT and ASTER) in representing the topography and morphology of the study area. The work presented attempts to predict the future land-use changes through a Cellular Automata (CA)-Markov model developed for modelling LULC dynamics in the area. The model was found to perform fairly well in obtaining projections of two past LULC images based on historical images. Future projections of LULC were obtained at five-year intervals (i.e., 2015, 2020, 2025, 2030) using the developed CA-Markov model. The effect of using past as well as future (projected) LULC on hydrological processes simulated by SWAT was examined for Hemavathi river catchment by considering historical climate data. In addition, combined effect of future LULC and climate changes was assessed on the hydrological processes in Hemavathi river catchment by driving SWAT model using combination of six LULC images (2006, 2010, 2015, 2020, 2025 and 2030 years) and future climate data for the period January 2006 to December 2035. Comparisons are presented with hydrological processes obtained from SWAT model for the cases where (i) only climate change (for the period January 2006 to December 2035) is considered and LULC is chosen corresponding to the year 1991, and (ii) only LULC change is considered by fixing it to a particular year (from among 2006, 2010, 2015, 2020, 2025 and 2030) along with historical climate data for the period 1977-2001. Inferences drawn from the study include: (I) Choice of DEM source and its resolution has an effect on future projections of hydrological processes obtained using a hydrologic model like SWAT when driven using downscaled climate variables. (ii) SRTM and ASTER DEMs provide better representation of elevation as well as morphometric characteristics in the upper Cauvery basin. (iii) The number of HRUs is more sensitive to the resolution of DEM, whereas the number of sub-watersheds is less sensitive to the DEM resolution. (iv) Reduction in agricultural area (by 7.70%) and increase in coffee/plantation area (by 5.91%) was evident during the period 1991-2010. The change was high during 1991-2000 and it has started to decrease during 2000-2006 and was marginal during 2006-2010. Agricultural area is projected to further decrease by 1.45%, whereas coffee/plantation is likely to increase by 1.22% during the period 2010-2030, by the developed Cellular Automata (CA)-Markov LULC model. (v) Duration of south-west monsoon season (June-September) is projected to extend from May to October in the climate change scenario during 2006 to 2085 in analysis with BCC GCM. (vi) Decrease in surface runoff and increase in other hydrological processes (lateral flow, return flow, infiltration, soil water, evapotranspiration and streamflow) was evident in the historical period (1991-2010), and a similar trend is projected for the future period (2010-2030) in climate change scenario. (vii) When changes in both LULC and climate are considered, estimates obtained for hydrological processes (except surface runoff) using SWAT are higher than estimates of the processes obtained by considering only climate change. (viii) Lateral flow, return flow, percolation, soil water and streamflow are projected to increase relative to their historical values when either climate change, or both climate and LULC changes are considered in the analysis. Mechanistic insights are provided on some mitigation strategies and management practices to counter some of the negative impacts of future (expected) changes in climate variability and LULC over the study area.

Groundwater chemistry is a function of recharge and the input chemistry of the rain, which gets transformed as it moves through the soil matrix. Apart from mineral transformations, anthropogenic activities are other external factors, which affect the groundwater chemistry. Stream – aquifer interactions alter the chemistry of groundwater in the regions nearer to the stream. A study is carried out to analyse the hydrogeochemical behavior under the influence of lithologic, precipitation and anthropogenic controls in the upper Cauvery basin. This is followed by the analysis of contributions made by the components of the hydrogeochemical cycle. A geochemical model is developed, which is used to study the spatiotemporal variations in groundwater chemistry of a silicatic rock group in a small experimental watershed. In order to study the effects of precipitation control on the groundwater chemistry the Upper Cauvery river basin (~ 10000 km2) is selected for the analysis, which stretches along three climatic zones – ‘semi-arid’ (500 – 800 mm/year rainfall), ‘sub-humid’ (1000 - 1200 mm/year) and ‘humid’ (1200 – 1500 mm/year) zones. The basin is mainly formed by granitic gneissic group of rocks with some traces of amphibolites and charnockites. Groundwater is observed to occur either in the saprolite or in the deeper hard rock zone based on the geomorphology even at the scale of a small watershed. Parts of this basin are under canal irrigation and are drained by Kabini and Cauvery Rivers. Groundwater – surface water interactions play an important role in these regions. Irrigation with different levels of intensities is practiced through groundwater in the upland areas. Observation wells considered in these three zones are classified into four classes based on the mean annual groundwater fluctuations. Wells in each of these four classes are further classified into ‘shallow’ and ‘deep’ categories based on the depth to groundwater. Analysis of the groundwater chemistry in the basin (widely spread with 120 wells in the three zones) shows a gradient in chemistry along the climatic gradient with sub-humid zone bridging between the semi-arid and humid zones. Ca/Na and Mg/Na ratios decrease from humid zone (unimodal rainfall) to semi-arid (bimodal rainfall) zone since both Na and Mg concentrations in groundwater increase along this gradient. These elements are mainly controlled by weathering reactions. Apart from the weathering of Ca, calcrete formations also play an important role in the semi-arid zone. Ion exchange process cycles between Cl and SO4 and between Ca and Na. Dissolution of CaCO3, silicate weathering and evaporation are the major mineralogical reactions. Variations in Na/Cl and Ca/Cl molar ratios indicate that shallow wells have higher molar ratios with higher variance than the deeper wells. Semi-arid zone is more silicaceous (higher Na/Cl value) than the humid zone, which has higher Ca/Cl ratio (~ 14). Effective seasonal patterns are identified using ‘recharge – discharge’ concept based on the rainfall intensity. Wells under normal scenario have low Na/Cl and Ca/Cl ratios in the ‘recharge period’ than in the corresponding ‘discharge period’ (dilution chemistry). Wells in the relatively higher pumping regions, which receive sufficient annual recharge exhibit dilution chemistry though groundwater level fluctuations are higher. However, wells in regions with insufficient recharge show ‘anti - dilution’ chemistry. Thus, the ‘recharge – discharge’ concept is useful in identifying the pumped wells from deeper wells and helps in characterizing the anthropogenic effects on the basin. Rainfall and its chemistry are to be analysed to understand the groundwater chemistry. Hence, data from various monitoring stations in India are analyzed for assessing the influence of several major factors such as, topographic location of the area, its distance from sea and annual rainfall. These stations are categorized as ‘urban’, ‘suburban’ and ‘rural’. pH, HCO3, NO3 and Mg concentrations have not changed much from coast to inland. On the other hand, SO4 and Ca concentrations changes are subjected to local emissions. Cl and Na (marine elements) originate solely from sea and a model is developed to quantify the variation in concentration of these elements under the influence of inland distance and annual rainfall. Non – linear regression model for the various categories shows that both rainfall amount and precipitation chemistry follow a power law reduction with distance from sea. Cl and Na decrease rapidly for the first 100 km distance from sea, then decrease marginally for the next 100 km and then later stabilize. Regression parameters estimated for different cases are found to be consistent (R2 ~ 0.8). Variation in one of the regression parameters accounts for the effect of urbanization. Model developed for precipitation chemistry is validated using stations from the southern peninsular region of the country. Model predictions are found to be in good correlation with observations with a relative error of ~ 5%. This relationship between the three parameters – rainfall amount, coastline distance, and concentration (in terms of Cl and Na) was validated with experiments conducted at Mule Hole SEW and Kalekere. Monthly variations in precipitation chemistry at these stations are predicted from a downscaled (in time) model and then compared with the observed data. Models developed at both annual and monthly scale are found to perform well with the field observations. Hence, this model is used for predicting the precipitation chemistry (in terms of Cl and Na) of different station points in the upper Cauvery basin. Comparative performance of alternate methods of recharge estimation i.e. Chloride mass balance (CMB) and water table fluctuation (WTF) approaches, is analyzed at various stations in the basin. Annual rainfall, Cl concentration in rain (predicted from precipitation model) and the concentration of Cl in the groundwater are the inputs for the CMB approach. Since main source of Na is from atmosphere, Na is taken as an alternative for Cl in the CMB approach and recharge is estimated using sodium mass balance (SMB) approach. Na concentrations contributed from weathering are quantified and eliminated in the analysis. Recharge estimated using SMB approach is found to be higher than CMB estimate in the semi-arid and the sub-humid zones. Water table fluctuation (WTF) method is used to compare the recharge obtained from both CMB and SMB approaches. Estimates using WTF approach are found to be higher than both CMB and SMB in the semi-arid and the sub-humid zones while SMB is found to be higher than CMB estimates. SMB and WTF estimates match well in the humid zone. An exponential relationship between recharge and annual rainfall is observed. Recharge coefficient estimated on an annual scale varied from 0.1 to 0.25 across the basin. Among CMB and SMB approaches, SMB is a better alternative for recharge estimation in semi-arid zones, where WTF approach performed poorly. Water – rock reactions are driven by the inequilibrium reactions of water with the mineral assemblage in the rock. These reactions evolve towards equilibrium with the primary minerals while a series of secondary minerals precipitate. Mass balance approach is adopted to quantify the rate at which the water – rock interactions occur in order to reach the equilibrium. Field experiments in the experimental watershed (Mule Hole SEW, ~ 4.5 km2) are carried to identify the minerals present in the region and their composition. Quartz, oligoclase, sericite, epidote and chlorite are the primary minerals while kaolinite and Fe-oxides are the secondary minerals present in this region. Percentages of oxides of different elements in each of these minerals are determined from the field experiments. Stoichiometric coefficients of different elements in each of these minerals are determined from these percentages. Long – term weathering rates are determined using these stoichiometric coefficients along with the mass fluxes of each element. Set of minerals present at different depths are found to vary among the thirteen observation wells of Mule Hole SEW. Hence, the mass balance calculations resulted in different weathering rates for a particular mineral based on the spatial location and the particular depth of the occurrence of the mineral. These weathering rates are tested for the sensitivity to carbonates with the inclusion of calcite in the mass balance calculations. With this sensitivity analysis it is observed that the presence of carbonates in the nodular form in the shallow wells has not changed the weathering reactions and their rates, and hence these wells are termed to be in the ‘silicate with secondary carbonate’ system. On the other hand, carbonates are not present in deeper wells, inclusion of which alters the equilibrium of the mass balance calculations. Thus, these wells are said to belong to the ‘silicate’ system. Anorthite present in some of the wells (MH2 and MH6) dissolves accompanied with the dissolution of carbonates. These wells are observed to belong to the third group the ‘amphibolites with primary carbonate’ system. Weathering rates of all the minerals present in these three different systems are also determined annually (short term rates). Mean of these short – term rates are observed to be the same as the long – term (over a period of 4 years) weathering rates with a minor difference of 3 – 10% in values. Thus, the weathering rates determined using mass balance approach is used to determine the quantities of concentrations of different elements contributed from the mineralogical reactions. Temporal variations in the concentrations of different chemical species in this small experimental watershed are simulated using a hydrogeochemical model. The model is developed based on a mixing cell approach, which considers the spatiotemporal variations in the recharge and the weathering inputs. Most of the weathering reactions are observed to take place in the saturated zone, which is termed as the ‘mixing zone’. This zone extends from few meters above the groundwater table to few meters below the water table. Mixing zone is discretized into series of ‘cells’ and concentrations in this zone are simulated. This group of cells is assumed to move along with the groundwater fluctuation. Sensitivity of the model is analysed subject to the variations in the recharge and the weathering fluxes. The developed model is used to simulate the concentrations of the groundwater in the three systems – ‘silicate’, ‘silicate with secondary carbonate’ and ‘amphibolites with primary carbonate’. Field data for chemical species is observed to vary in this mixing zone, boundaries of which are defined from the model simulations. Simulations corresponding to the cell at the mid depth of this mixing zone are observed to correlate well with the field data. Hence, the model developed is able to simulate the temporal variations in the groundwater chemistry. In summary, the study analyses the effects of lithological, climatic and anthropogenic factors on groundwater chemistry. The transformations in the rainwater chemistry as it reaches groundwater are analysed along different stages. A hydrogeochemical model is developed to simulate the groundwater concentrations in three different mineralogical settings over a period of three years.

Groundwater chemistry is a function of recharge and the input chemistry of the rain, which gets transformed as it moves through the soil matrix. Apart from mineral transformations, anthropogenic activities are other external factors, which affect the groundwater chemistry. Stream – aquifer interactions alter the chemistry of groundwater in the regions nearer to the stream. A study is carried out to analyse the hydrogeochemical behavior under the influence of lithologic, precipitation and anthropogenic controls in the upper Cauvery basin. This is followed by the analysis of contributions made by the components of the hydrogeochemical cycle. A geochemical model is developed, which is used to study the spatiotemporal variations in groundwater chemistry of a silicatic rock group in a small experimental watershed. In order to study the effects of precipitation control on the groundwater chemistry the Upper Cauvery river basin (~ 10000 km2) is selected for the analysis, which stretches along three climatic zones – ‘semi-arid’ (500 – 800 mm/year rainfall), ‘sub-humid’ (1000 - 1200 mm/year) and ‘humid’ (1200 – 1500 mm/year) zones. The basin is mainly formed by granitic gneissic group of rocks with some traces of amphibolites and charnockites. Groundwater is observed to occur either in the saprolite or in the deeper hard rock zone based on the geomorphology even at the scale of a small watershed. Parts of this basin are under canal irrigation and are drained by Kabini and Cauvery Rivers. Groundwater – surface water interactions play an important role in these regions. Irrigation with different levels of intensities is practiced through groundwater in the upland areas. Observation wells considered in these three zones are classified into four classes based on the mean annual groundwater fluctuations. Wells in each of these four classes are further classified into ‘shallow’ and ‘deep’ categories based on the depth to groundwater. Analysis of the groundwater chemistry in the basin (widely spread with 120 wells in the three zones) shows a gradient in chemistry along the climatic gradient with sub-humid zone bridging between the semi-arid and humid zones. Ca/Na and Mg/Na ratios decrease from humid zone (unimodal rainfall) to semi-arid (bimodal rainfall) zone since both Na and Mg concentrations in groundwater increase along this gradient. These elements are mainly controlled by weathering reactions. Apart from the weathering of Ca, calcrete formations also play an important role in the semi-arid zone. Ion exchange process cycles between Cl and SO4 and between Ca and Na. Dissolution of CaCO3, silicate weathering and evaporation are the major mineralogical reactions. Variations in Na/Cl and Ca/Cl molar ratios indicate that shallow wells have higher molar ratios with higher variance than the deeper wells. Semi-arid zone is more silicaceous (higher Na/Cl value) than the humid zone, which has higher Ca/Cl ratio (~ 14). Effective seasonal patterns are identified using ‘recharge – discharge’ concept based on the rainfall intensity. Wells under normal scenario have low Na/Cl and Ca/Cl ratios in the ‘recharge period’ than in the corresponding ‘discharge period’ (dilution chemistry). Wells in the relatively higher pumping regions, which receive sufficient annual recharge exhibit dilution chemistry though groundwater level fluctuations are higher. However, wells in regions with insufficient recharge show ‘anti - dilution’ chemistry. Thus, the ‘recharge – discharge’ concept is useful in identifying the pumped wells from deeper wells and helps in characterizing the anthropogenic effects on the basin. Rainfall and its chemistry are to be analysed to understand the groundwater chemistry. Hence, data from various monitoring stations in India are analyzed for assessing the influence of several major factors such as, topographic location of the area, its distance from sea and annual rainfall. These stations are categorized as ‘urban’, ‘suburban’ and ‘rural’. pH, HCO3, NO3 and Mg concentrations have not changed much from coast to inland. On the other hand, SO4 and Ca concentrations changes are subjected to local emissions. Cl and Na (marine elements) originate solely from sea and a model is developed to quantify the variation in concentration of these elements under the influence of inland distance and annual rainfall. Non – linear regression model for the various categories shows that both rainfall amount and precipitation chemistry follow a power law reduction with distance from sea. Cl and Na decrease rapidly for the first 100 km distance from sea, then decrease marginally for the next 100 km and then later stabilize. Regression parameters estimated for different cases are found to be consistent (R2 ~ 0.8). Variation in one of the regression parameters accounts for the effect of urbanization. Model developed for precipitation chemistry is validated using stations from the southern peninsular region of the country. Model predictions are found to be in good correlation with observations with a relative error of ~ 5%. This relationship between the three parameters – rainfall amount, coastline distance, and concentration (in terms of Cl and Na) was validated with experiments conducted at Mule Hole SEW and Kalekere. Monthly variations in precipitation chemistry at these stations are predicted from a downscaled (in time) model and then compared with the observed data. Models developed at both annual and monthly scale are found to perform well with the field observations. Hence, this model is used for predicting the precipitation chemistry (in terms of Cl and Na) of different station points in the upper Cauvery basin. Comparative performance of alternate methods of recharge estimation i.e. Chloride mass balance (CMB) and water table fluctuation (WTF) approaches, is analyzed at various stations in the basin. Annual rainfall, Cl concentration in rain (predicted from precipitation model) and the concentration of Cl in the groundwater are the inputs for the CMB approach. Since main source of Na is from atmosphere, Na is taken as an alternative for Cl in the CMB approach and recharge is estimated using sodium mass balance (SMB) approach. Na concentrations contributed from weathering are quantified and eliminated in the analysis. Recharge estimated using SMB approach is found to be higher than CMB estimate in the semi-arid and the sub-humid zones. Water table fluctuation (WTF) method is used to compare the recharge obtained from both CMB and SMB approaches. Estimates using WTF approach are found to be higher than both CMB and SMB in the semi-arid and the sub-humid zones while SMB is found to be higher than CMB estimates. SMB and WTF estimates match well in the humid zone. An exponential relationship between recharge and annual rainfall is observed. Recharge coefficient estimated on an annual scale varied from 0.1 to 0.25 across the basin. Among CMB and SMB approaches, SMB is a better alternative for recharge estimation in semi-arid zones, where WTF approach performed poorly. Water – rock reactions are driven by the inequilibrium reactions of water with the mineral assemblage in the rock. These reactions evolve towards equilibrium with the primary minerals while a series of secondary minerals precipitate. Mass balance approach is adopted to quantify the rate at which the water – rock interactions occur in order to reach the equilibrium. Field experiments in the experimental watershed (Mule Hole SEW, ~ 4.5 km2) are carried to identify the minerals present in the region and their composition. Quartz, oligoclase, sericite, epidote and chlorite are the primary minerals while kaolinite and Fe-oxides are the secondary minerals present in this region. Percentages of oxides of different elements in each of these minerals are determined from the field experiments. Stoichiometric coefficients of different elements in each of these minerals are determined from these percentages. Long – term weathering rates are determined using these stoichiometric coefficients along with the mass fluxes of each element. Set of minerals present at different depths are found to vary among the thirteen observation wells of Mule Hole SEW. Hence, the mass balance calculations resulted in different weathering rates for a particular mineral based on the spatial location and the particular depth of the occurrence of the mineral. These weathering rates are tested for the sensitivity to carbonates with the inclusion of calcite in the mass balance calculations. With this sensitivity analysis it is observed that the presence of carbonates in the nodular form in the shallow wells has not changed the weathering reactions and their rates, and hence these wells are termed to be in the ‘silicate with secondary carbonate’ system. On the other hand, carbonates are not present in deeper wells, inclusion of which alters the equilibrium of the mass balance calculations. Thus, these wells are said to belong to the ‘silicate’ system. Anorthite present in some of the wells (MH2 and MH6) dissolves accompanied with the dissolution of carbonates. These wells are observed to belong to the third group the ‘amphibolites with primary carbonate’ system. Weathering rates of all the minerals present in these three different systems are also determined annually (short term rates). Mean of these short – term rates are observed to be the same as the long – term (over a period of 4 years) weathering rates with a minor difference of 3 – 10% in values. Thus, the weathering rates determined using mass balance approach is used to determine the quantities of concentrations of different elements contributed from the mineralogical reactions. Temporal variations in the concentrations of different chemical species in this small experimental watershed are simulated using a hydrogeochemical model. The model is developed based on a mixing cell approach, which considers the spatiotemporal variations in the recharge and the weathering inputs. Most of the weathering reactions are observed to take place in the saturated zone, which is termed as the ‘mixing zone’. This zone extends from few meters above the groundwater table to few meters below the water table. Mixing zone is discretized into series of ‘cells’ and concentrations in this zone are simulated. This group of cells is assumed to move along with the groundwater fluctuation. Sensitivity of the model is analysed subject to the variations in the recharge and the weathering fluxes. The developed model is used to simulate the concentrations of the groundwater in the three systems – ‘silicate’, ‘silicate with secondary carbonate’ and ‘amphibolites with primary carbonate’. Field data for chemical species is observed to vary in this mixing zone, boundaries of which are defined from the model simulations. Simulations corresponding to the cell at the mid depth of this mixing zone are observed to correlate well with the field data. Hence, the model developed is able to simulate the temporal variations in the groundwater chemistry. In summary, the study analyses the effects of lithological, climatic and anthropogenic factors on groundwater chemistry. The transformations in the rainwater chemistry as it reaches groundwater are analysed along different stages. A hydrogeochemical model is developed to simulate the groundwater concentrations in three different mineralogical settings over a period of three years.

The economic growth and the increase in population has led to an increased demand for water for various purposes such as domestic consumption, irrigation, industrial use, power generation, navigation, recreation, and ecological requirements. With the increase in population, the per-capita water availability is continuously decreasing. Due to increase in demand and accompanying scarcity of water the conflict among the potential users of the resource is on raise. Hence, the allocation of the available water resource is a big challenge as the intersect oral and inter-regional water allocation is often competing and conflicting in nature. In the above context a good model to manage the available water resources would require reliable inputs on the available water resources. In the first part of this thesis we compare different techniques that are typically used for modeling the river water flow. Time series analysis (ARIMA) is compared with machine learning techniques such as support-vector regression (SVR) and neural network models. The performance of these techniques is compared by applying them to a long-term time-series data of the inflows of three tributaries of the river Cauvery into the Krishnaraja Sagar reservoir (KRS). Flow data over a period of 30 years from three different observation points established in upper Cauvery river sub-basin is analyzed. Specifically, a multi-layer feed forward network trained with a back-propagation algorithm and support vector regression with epsilon-insensitive loss function is compared with the ARIMA models. It is found that the performance of support vector regression model is superior to those of the other techniques considered. The second part of our thesis is to develop a model for optimal water allocation to the different sectors with the aim of maximizing the total utility of available water resource in a river basin. A hydro-economic modeling framework is developed that incorporates the economic assessment of the value of water. This inter-sectoral allocation problem is studied in the context of enforcing certain minimum water rights to every person for domestic use and a certain minimum irrigation need set out by the contingency plans of the state agriculture department in Cauvery river basin. A non-linear optimization model is built to obtain an optimal inter-sectoral water allocation policy. The study evaluates the economic impact of different parameters of competing demands such as water availability, population, basic water right (quantity), ground water contribution, and crop benefit. The optimal policies that implements the water allocation priorities as set out by the National Water Policy (2012) are compared. Further, results show that the basic water right can be secured for essential needs with optimal management of available surface and ground water resources. In the third part of thesis, we study the conflict of water sharing that arises between sectors/regions. We consider the river water-sharing problem between two agents along a river. Each agent has a stated claim to the river water. The Absolute Territorial Sovereignty (ATS) and Absolute Territorial Integrity (ATI) principles are promoted by different agents along the river as a means to maximize their individual benefit. However, these principles are invariably considered to be unjust by one or more of the other agents. Hence, it is preferred to have a negotiated water treaty that is perceived to be equitable and just by all. A one way downstream stream bilateral bargaining model can be used to guide the negotiated water treaty between the agents. In this bargaining framework we introduce the issue of negative externalities imposed by the upstream agent on the downstream agent/s in the form of pollution and/or flooding. This imposes a cost on the downstream agent to mitigate losses due to the negative externalities. A bargaining model that incorporates the impact of negative externalities is developed to guide the negotiated treaties. We identify individually rational bargaining strategies for a two agents transferable utility one way downstream river water sharing problem. The results characterize the agreement and disagreement points for bilateral trading

The economic growth and the increase in population has led to an increased demand for water for various purposes such as domestic consumption, irrigation, industrial use, power generation, navigation, recreation, and ecological requirements. With the increase in population, the per-capita water availability is continuously decreasing. Due to increase in demand and accompanying scarcity of water the conflict among the potential users of the resource is on raise. Hence, the allocation of the available water resource is a big challenge as the intersect oral and inter-regional water allocation is often competing and conflicting in nature. In the above context a good model to manage the available water resources would require reliable inputs on the available water resources. In the first part of this thesis we compare different techniques that are typically used for modeling the river water flow. Time series analysis (ARIMA) is compared with machine learning techniques such as support-vector regression (SVR) and neural network models. The performance of these techniques is compared by applying them to a long-term time-series data of the inflows of three tributaries of the river Cauvery into the Krishnaraja Sagar reservoir (KRS). Flow data over a period of 30 years from three different observation points established in upper Cauvery river sub-basin is analyzed. Specifically, a multi-layer feed forward network trained with a back-propagation algorithm and support vector regression with epsilon-insensitive loss function is compared with the ARIMA models. It is found that the performance of support vector regression model is superior to those of the other techniques considered. The second part of our thesis is to develop a model for optimal water allocation to the different sectors with the aim of maximizing the total utility of available water resource in a river basin. A hydro-economic modeling framework is developed that incorporates the economic assessment of the value of water. This inter-sectoral allocation problem is studied in the context of enforcing certain minimum water rights to every person for domestic use and a certain minimum irrigation need set out by the contingency plans of the state agriculture department in Cauvery river basin. A non-linear optimization model is built to obtain an optimal inter-sectoral water allocation policy. The study evaluates the economic impact of different parameters of competing demands such as water availability, population, basic water right (quantity), ground water contribution, and crop benefit. The optimal policies that implements the water allocation priorities as set out by the National Water Policy (2012) are compared. Further, results show that the basic water right can be secured for essential needs with optimal management of available surface and ground water resources. In the third part of thesis, we study the conflict of water sharing that arises between sectors/regions. We consider the river water-sharing problem between two agents along a river. Each agent has a stated claim to the river water. The Absolute Territorial Sovereignty (ATS) and Absolute Territorial Integrity (ATI) principles are promoted by different agents along the river as a means to maximize their individual benefit. However, these principles are invariably considered to be unjust by one or more of the other agents. Hence, it is preferred to have a negotiated water treaty that is perceived to be equitable and just by all. A one way downstream stream bilateral bargaining model can be used to guide the negotiated water treaty between the agents. In this bargaining framework we introduce the issue of negative externalities imposed by the upstream agent on the downstream agent/s in the form of pollution and/or flooding. This imposes a cost on the downstream agent to mitigate losses due to the negative externalities. A bargaining model that incorporates the impact of negative externalities is developed to guide the negotiated treaties. We identify individually rational bargaining strategies for a two agents transferable utility one way downstream river water sharing problem. The results characterize the agreement and disagreement points for bilateral trading