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Accueil du site → Doctorat → Inde → 2015 → Rainfall Variability in the Tunga and Bhadra River Basins based on Remote Sensing Approach

Central University of Karnataka (2015)

Rainfall Variability in the Tunga and Bhadra River Basins based on Remote Sensing Approach

Nischitha.V

Titre : Rainfall Variability in the Tunga and Bhadra River Basins based on Remote Sensing Approach

Auteur : Nischitha.V

Université de soutenance : Central University of Karnataka

Grade : Doctor of Philosophy (PhD) 2015

Résumé
Rainfall is one of the vital element of hydrological cycle and hence its variability in spatial and temporal scales can significantly affect all components of the regional water balance. The rainfall variability under the effect of orography and the lack of rain gauge stations creating a spatio-temporal gaps in the rainfall meassurements in Tunga and Bhadra river basins. Rainfed agriculture is the main occupation of the livelihood and the high intensity monsoon rainfall causes great damage to the agricultural crops every year in this region. Therefore, the study of rainfall variability is very essential in this region. This thesis presents a short overview of the formation of rainfall and its variability at different scales together with the various instruments for meassuring the rainfall. The thesis also attempts to add to to the knowledge on the general information on the study area required for present research work such as its geography, climate, land use, soil types,drainage charecteristics along with some other informations of the basins. First, the spatial and temporal variability of rainfall is investigated using the rain gauge and the TRMM observations. Further statistical methods are applied to validate the TRMM estmates versus gauge data. The hovmoller diagrams are plotted to undersstand the seasonal and diurnal variations in rainfall variability. The results suggest that orography of the western ghat mountains mainly affect the rainfall variability and diurnal cycle in this region. The results of validation suggests TRMM captures the precipitation pattern observed by the rain gauges with slight underestimations. Active breaks cycles are observed in the intraseassonal variations. The analysis of diurnal time scale suggests the study area experience high rainfall activity in the afternoon hours. Second, the impact of seasonal rainfall variability on vegetation greenness of the study area is studied using NDVI and rainfall data. The results are accomplished through the analysis of grahs, maps and correlation methods. The results suggests rainfall variability exerts a seasonal control on vegetation greeneness. The high rainfall of the monsoon showed inverse relationship with the vegetation greeness of the monsoon season and a positive relationship with rest of the seasons. High vegetation greeness is observed in the post monsoon season indicated the need of other climatic factors along with the rain water for vegetation growth in the study region. Also the study showed, the stability of the high monsoon rainfall in sustaining the long term vegetation greeneness of the river basins. Third, the rainfall runoff of the river basins is estimated using HEC-HMS model and accuracy of the model simulations is evaluated. The NRCS curve number method is used to generate the runoff of the river basins along with some statistical techniques for evaluation of model performance. It is noticed that land use change is the major factor affecting the runoff generation of the study area. The results suggest that the model has reasonably good predicting capability with slight underprediction of observed flows.

Présentation et version intégrale (Shodhganga)

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