Madhusudana Rao Chintalacheruvu

Recent developments in hydrometric practices enable the measurements of continuous maximum surface velocity of flow passing at a river section and the corresponding water level using a combined surface velocity and water level sensors installed across river bridges. These measurements enable continuous discharge estimation at these river section by employing the well-studied entropy methods. However, the cost of equipping these combined radars at many gauging stations of a river may be prohibitive. But the use of standalone water level radars at many stations may not be cost-wise prohibitive. Taking into consideration of this aspect, the current study proposes a novel method of routing the upstream estimated velocity hydrograph to a desired downstream station of a river reach, which is equipped with a water level sensor, and using the routed velocity hydrograph and the water levels measured at that station, one can estimate the corresponding discharge hydrograph. The proposed study establishes the equation governing the velocity hydrograph propagation in a channel reach which is of the same form as that of the weak-diffusive wave equations governing the discharge and flow depth hydrographs propagation. The derived velocity routing equation is of the same form as the Muskingum routing equation. The parameters of the routing method are estimated using the channel and velocity characteristics of the propagating velocity hydrograph. The proposed velocity routing method is tested by routing the hypothetical velocity hydrographs arrived at by routing a given hypothetical discharge hydrograph defined by Pearson Type-III mathematical function at the inlet of 25 uniform trapezoidal channel reaches each characterised by a unique combination of bed slope and Manning’s roughness characteristics. The benchmark solutions were arrived using the HEC-RAS model. The routed velocity hydrographs enable the close reproduction of the corresponding estimated benchmark velocity hydrographs and, thus, proving the appropriateness of the proposed velocity hydrograph routing method.

The well-known Muskingum-Cunge method and the variable parameter Muskingum-Cunge-Todini method (Todini 2007) have been developed by matching the diffusion coefficient of the numerical analogue of the kinematic wave equation with that of the physical diffusive wave equation governing the one dimensional flood wave propagation in channels. It is shown in this study that an alternative variable parameter Muskingum method can be directly derived from the diffusive wave equation without resorting to the matched diffusivity approach as followed in the above mentioned two methods. A comparative evaluation of the routing performances of this method with those of very two similar methods, known as the variable parameter Muskingum-Cunge-Todini (MCT) method as proposed by Todini (2007), and another Variable Parameter McCarthy-Muskingum (VPMM) method proposed by Perumal and Price (2013) is made in the study. For the purpose of comparative evaluation, all these three methods use the same set of benchmark solutions obtained by routing a given inflow hydrograph in twenty five trapezoidal channels each having the same bed width and the side slope, but each of them characterized by unique combinations of bed slopes and Manning’s roughness coefficients. Standard evaluation measures as available in the literature were used in assessing the capabilities of each of the three methods in reproducing the benchmark solutions obtained by routing the given hypothetical inflow hydrograph by the HEC-RAS model for a reach length of 100 km in each of these channels. All the three methods show equal performances in reproducing the benchmark solutions with NSE≳0.99, when the inflow hydrograph is characterized by the water surface gradient +(1/S0)∂y/∂x≤0.5. But for the routing cases characterized by +(1/S0)∂y/∂x>0.5, the MCT method fails to route the inflow hydrograph, while the other two methods yield results with diminished performance levels (NSE

The comparative performances of two variable parameter Muskingum flood routing models are evaluated in this study from the perspective of overall reproduction of the routed flood hydrographs characterized by different magnitudes of attenuation of the routed benchmark hydrographs. These two models are the Variable Parameter Muskingum-Cunge-Todini (MCT) model advocated by Todini in 2007, and the Variable Parameter McCarthy-Muskingum (VPMM) model advocated by Perumal and Price in 2013. To investigate this objective, routing studies were undertaken by routing a given hypothetical inflow hydrograph in 25 hypothetical trapezoidal channel reaches of the same geometrical size, but each characterized by different unique combinations of channel bed slopes and Manning’s roughness coefficients. The study results demonstrate that the VPMM model is capable of better reproduction of different levels of attenuation of the routed benchmark hydrographs in small bed slope channels in comparison with that of the MCT model. However, for steep and very steep bed slope channels, where the attenuation is small or insignificant, both the VPMM and MCT models perform equally well due to the reason that the latter model is a specific case of the former model. The study concludes that the application of the VPMM model is more suitable for field routing studies than the MCT model, when the magnitude of the water surface gradient of the inflow hydrograph is characterized by an absolute magnitude of (1/S0) ∂y/∂x where, S0 and ∂y/∂x are, respectively, the bed slope of the channel and the relative water surface gradient of the inflow hydrograph. The added advantage of employing the VPMM model is that it has the capability of estimating the stage hydrograph at the end of the routing reach or sub-reaches corresponding to the routed discharge hydrograph in a manner consistent with the numerical solution approach of the full Saint- Venant equations.

The generation of hydropower is profoundly influenced by shifts in streamflow patterns induced by climate change. This research examines changes in streamflow and the potential surge in hydropower generation over a span of 35 years (2015–2050) at the Bhakra Dam site within the Upper Sutlej River basin. Employing a deep learning methodology, particularly the long short-term memory (LSTM) model, in conjunction with Coupled Model Intercomparison Project (CMIP) 6 multi-global climate model (GCM), facilitates a thorough analysis of these dynamics. Six out of 14 bias-corrected statistically downscaled datasets (0.25° × 0.25° grid resolution) from CMIP6 multi-GCM were selected based on entropy and combined compromise solution techniques. This innovative approach is utilized to assess streamflows and project potential increases in hydropower at the Bhakra Dam site under shared socioeconomic pathways (SSP) scenarios, specifically SSP245 and SSP585. The results indicate a maximum increase of approximately 15% and 17% in mean monthly streamflow under SSP245 and SSP585, respectively. Moreover, dependability flows calculated at Q50, Q75, and Q90 show respective rises of 13%, 16%, and 17% under SSP245 and 21%, 17%, and 18% under SSP585. The projected hydropower potential exhibits an increase of up to 15.9% and 17.3% under SSP245 and SSP585, respectively.