The model calibration was done by using the thumb rule. According to the thumb rule the number of simulations depends on the number of parameters used in the calibration (Abbaspour et al. 2015). A minimum of 100 simulations was used for each parameter during the calibration phase of the model. The number of iterations depends on the model evaluation parameters. If the model satisfies the range of statistical indices the calibration process was stopped. The model evaluation parameters such as R², NSE, bR², RSR, KGE and PBIAS for the initial calibration were found to be 0.20, −0.20, 0.08, 1.10, 0.25, 71.7 and 0.48, 0.26, 0.22, 0.86, 0.33 54.9, respectively, for daily and monthly time step (Table 3). The result of initial calibration indicates there is a very high inconsistency between the observed and simulated streamflow. The SUFI algorithm uses five elevation bands and 19 parameters to improve consistency, high flow, low flows, and model efficiency. Using the thumb rule for the iterations, the optimum values of the calibrated model parameters have been adjusted. The range and the optimum fitted values of the model parameters are shown in Table 2. The Precipitation lapse rate (PLAPS) was calibrated within 1,000–2,000 mm, and it was fitted at 1,468.50 and 1,739.47 mm, respectively, for the daily and monthly time steps. The temperature lapse rate (TLAPS) was calibrated within −7 to −6 °C and fitted at −6.25 °C for daily and monthly time steps (Table 2). These two parameters are used to adjust the precipitation and temperature rates according to the elevation; as a result, snowmelt contribution in the streamflow is improved. The Snowfall temperature (SFTMP) was calibrated within −5 to 5 °C and fitted at 4.06, and 2.29 °C, Snowmelt base temperature (SMTMP) was calibrated within −5 to 5 and fitted at 3.48 and 2.71 °C, maximum melt factor (SMFMX) was calibrated within 1–10 and fitted at 2.40 and 1.31, minimum melt factor (SMFMN) was calibrated with and 1–10 and fitted at 6.91 and 1.54, and snowpack temperature lag factor (TIMP) was calibrated within −1 to 1 and fitted at −0.19 and −0.47, respectively, for daily and monthly time step (Table 2). These five parameters have also improved the snowmelt contribution in the streamflow. The minimum snow water content that corresponds to 100% snow cover (SNOCOVMAX) was calibrated within 0–200 mm and fitted at 156 and 60.53 mm, and the fraction of snow volume represented by SNOCOMX corresponds to 50% snow cover (SNO50COV) was calibrated within 0–0.25 and fitted at 0.07 and 0.16, respectively, for daily and monthly time step (Table 2). These two parameters show there is significant snowfall in the basin. The curve number CN₂ value was calibrated within −0.3 to 0.3, and it was fitted at 0.09 and 0.10. The available water capacity of the soil layer (SOL_AWC) was calibrated within 0–0.2 mm water/mm soil. It was fitted at 0.13 and 0.18 mm water/mm soil, and the soil evaporation compensation factor (ESCO) was calibrated within 0.05–0.2. It was fitted at 0.06 and 0.10, respectively, for daily and monthly time steps (Table 2). These three parameters indicate the peak surface runoff and streamflow were improved due to a small increase in the CN₂ and higher water uptake demand from the lower soil layer. The threshold water level in a shallow aquifer for base flow (GWQMN) was calibrated within 0–20 mm. It was fitted at 9.37 and 19 mm, the groundwater ‘revap’ coefficient (GE_REVAP) was set to be zero 0.0, and the percolation of the surface runoff to the deep aquifer (REVAPM) was calibrated within 0–100 mm. It was fitted at 96.87 and 96.58 mm. Re-evaporation through ground water (GW_REVAP) was set to be zero, delay in the ground water (GW_DELAY) was calibrated within 10–50 days and fitted at 11 and 28 days, respectively, for daily and monthly time step and base-flow recession coefficient (ALPHA_BF) was calibrated within 0–0.25. It was fitted at 0.19, respectively, for both daily and monthly time steps (Table 2). The calibrated groundwater parameters indicate that a 19 mm water level is required for base flow in the shallow aquifer while 96 mm is the threshold depth of water in the shallow aquifer percolate to the deep aquifer, and the maximum amount of groundwater will transfer to the overlaying saturated zone from the shallow aquifer whereas (Singh & Saravanan 2020), the very less response of groundwater flow to changes in recharge because of the presence of impermeable rocks present in the Himalayan region. The effective hydraulic conductivity of the channel (CH_K₂) was calibrated within 5–10 mm/h, and it was fitted at 7.34 and 6.43 mm/h, respectively, for daily and monthly time steps (Table 2) and shows there is a very less rate of surface water from the main channel. After calibration, the model evaluation parameters such as R², NSE, bR², RSR, KGE, and PBIAS were found to be 0.60, 0.55, 0.46, 0.68, 0.75, 13.2 and 0.75, 0.74, 0.64, 0.51, 0.86, 10.50, respectively, and also p-factor and r-factor for the calibration period were found to be 0.79, 1.21 and 0.79, 1.30, respectively, for daily and monthly time step (Table 3). Due to these, the peak flow, as well as base flow, has been improved (Figures 6(a) and 7(a)) also the correction of the observed streamflow and simulated streamflow is improved (Figure 8(a,b)). Further, the calibrated parameters were used to validation of the streamflow for the period 2008–2016. The R², NSE, bR², RSR, KGE, and PBIAS were found to be 0.65, 0.59, 0.50, 0.56, 0.79, 7.5 and 0.82, 0.78, 0.64, 0.51, 0.86, 9.25, respectively, for daily and monthly time step and also the p-factor and r-factor for the validation period was found to be 0.73, 1.30 and 0.87, 1.35, respectively, for daily and monthly time step (Table 3). In the validation, some peaks of the streamflow hydrograph were not properly captured by the model, whereas the model captured the lower peaks due to the lower range of CN₂ (Figures 6(b) and 7(b)), and the results show the observed and simulated discharge shows the good correlation for the validation period (Figure 8(c) and 8(d)). The efficiency parameters are also improved for calibration as well as the validation period.