Drought has become relatively one of the widespread extreme events that affect socio-economic sphere, ecological balance, environmental conditions, crop-yields, climate feedback mechanism, and water resources management. Monitoring of the drought is one of the challenging tasks, hence required to develop new techniques in prediction of this natural calamity accurately and timely. In this work, Combined Terrestrial Evapotranspiration Index (CTEI) that is forced through precipitation (P) and potential evapotranspiration (PET) is used for estimating drought. Also, this is a novel index developed for Indus-Ganga river basin, which also uses a Gravity Recovery and Climate Experiment (GRACE) terrestrial water storage anomalies (TWSA) data. Thirteen input-variables comprised of GRACE-TWSA, Global Land Data Assimilation System GLDAS-TWSA, Groundwater Storage Anomaly (GWSA), P, Land Surface Temperature ( LST), Wind Speed (WS), Evapotranspiration (ET), Runoff, air temperature ( ), PET, net-shortwave (SWN) and long-wave (LWN) along with net radiation (NR) radiations were implemented for predicting CTEI. Further, thirteen different combinations were analyzed using an improved Sequential Minimal Optimization (SMO) algorithm for support vector machine (SVM) and a greedy linear regression method. Therefore, the objectives of this study are to develop several combinations based on machine learning models used for modeling CTEI, compare the accuracy and stability of these models in CTEI prediction, and select the best outcomes have been provided from these models. The performed error measures and statistical indicators prove that Combo 2 and 3 owing to SVM model are superior to the best combinations of Greedy model. Overall based on the results, the improved SVM is superior to Greedy model in estimating CTEI. SVM (Combo2: R=0.81) in spite of having a higher range of relative error, is superior to Greedy model (Combo3, R=0.77) for estimating CTEI. This method can be one of promising alternatives for estimating CTEI over major river basins across the world.