Himalayan Rivers Research Articles

Estimation of non-point source of pollution loads in the River Song, a tributary of River Ganga, India.

The Himalayan rivers are particularly vulnerable to regional climate changes and anthropogenic influences, which can significantly alter both water quality and quantity, jeopardizing the fragile river ecosystems. This study investigates the hydrochemical characteristics of the Song River, a tributary of River Ganga focusing on non-point source (NPS) pollution, during the period June 2022 to November 2023. Monitoring of river discharge was carried out water samples were collected weekly during the monsoon (June to September), bi-weekly in the post-monsoon (October & November), and monthly during lean periods (December-May) from three monitoring stations. The study revealed that Biochemical Oxygen Demand (BOD) and Chemical Oxygen Demand (COD) eventually exceeded the criteria limits (3mg/L for BOD and 10mg/L for COD) prescribed by the Central Pollution Control Board (CPCB). The chemical composition of the river water at the monitoring stations revealed Ca2+and Mg2+ as the dominant cations, while HCO3⁻ and SO42⁻ were identified as the major anions. Gibbs plot suggesting the dominance of rock weathering as the major natural controlling mechanism of chemical composition in the basin. Carbonation and sulphide oxidation are two proton-producing reactions controlling the chemical weathering processes. C-ratio plot suggested that dominance of carbonate dissolution in the tributary Suswa, while Song River showed dominance of sulphide oxidation, particularly in its upstream region. Spatial and temporal analysis identified nutrient pollution (NO₃⁻, NH₄⁺, PO₄3⁻), organic loads (BOD, COD), and other parameters (TSS, Cl⁻) as key contributors to water quality deterioration at the monitoring stations. A chemical mass balance (CMB) approach based on mass conservation has been applied for estimating the NPS pollution loads on the Song River. CMB calculations carried out for major cations such as (Na+, K+, Ca2+, Mg2+, and NH4+) and major anions (Cl⁻, SO42⁻, HCO3⁻, NO3⁻, and PO43⁻) across a 21km stretch of the river, encompassing approximately 305 sq. km. and observed that the contribution of uncharacterised load was maximum in dry season and minimum during monsoon season. Seasonal variations in ion concentration and flux were strongly correlated with hydrological processes, highlighting the need for comprehensive monitoring and management of NPS pollution in the Song River to safeguard its water quality and downstream impacts on the Ganga River system.

Chemical Weathering Rates, C‐Q Relationships, Fluxes, Dam Impact and pCO2 Potential in the Ganga Headwaters: Insights From Weekly Time‐Series Data

AbstractPredicted alterations to the hydrological cycle due to higher temperatures at the end of this century will impact riverine processes such as weathering, erosion, and sediment transport. The Himalayan River basins, with their steep slopes, heavy rainfall, and increasing river engineering projects, are excellent sentinels for monitoring climate change and human impacts on rivers. However, few attempts have been made to capture the river mountainous catchment interaction over shorter time scales (weeks to months) to capture pulses of enhanced chemical weathering rates and other riverine processes. Here, we present a weekly time‐series record of dissolved inorganic constituents near the mouth of the Alaknanda and Bhagirathi rivers—the two headwater rivers of the Ganga River—with a weekly resolution during 2018–2019. We report new estimates of discharge‐weighted concentrations and fluxes. We found chemical weathering rates of 98.2 ± 54.0 and 32.2 ± 20.4 t/km2/year and CO2 consumption yields by silicate weathering of 3.7 ± 1.5 × 105 and 1.8 ± 1.2 × 105 mol CO2/km2/year for the Alaknanda and Bhagirathi basins, respectively, which are significantly higher compared to the global chemical weathering rate and CO2 consumption yield of ∼24 t/km2/year and ∼1 × 105 mol CO2/km2/year, respectively. We find that the concentration‐discharge relationship shows both chemostatic and dilution trends, with the Tehri dam strongly influencing the hydrology of the Bhagirathi River. The alkalinity‐DIC framework reveals that the Himalayan weathering acts as a net source of atmospheric pCO2 over a timescale of 105–107 years. Further, we show that a sampling campaign spreaded well throughout the year is imperative in reducing uncertainties in flux estimation.

Population Variability and Apparent Recent Decline of River Birds in the Indian Himalaya

ABSTRACTAbundance estimates are critical to animal conservation in the tropics and sub‐tropics, but assessments for some species and ecosystems in these regions are poorly developed. Estimates are particularly scarce for subtropical mountain rivers where some river organisms reach their greatest global diversity while being at risk from global change. We addressed these issues along rivers in the western Indian Himalaya, focusing on 12 bird species with varying dependence on river production, distribution, abundance, and detectability. We estimated river bird abundance through repeat field counts across 5 years using N‐mixture models to correct for imperfect detection from sparse data over an altitudinal range of 330–3100 m. Estimated abundances were modeled against elevation, flow, and river width as covariates. Detection probabilities overall were greatest in flycatching insectivores connected closely to the river channel and lowest in two piscivorous kingfishers. Patterns of abundance also varied among groups particularly in relation to elevation, with river passerines mostly recorded at mid and higher elevations and piscivorous taxa recorded mostly below 1600 m a.s.l. Five species apparently declined in overall population size by 5%–10% across the 5‐year study, in three cases matching national scale trends recorded by citizen science platforms. Our results reveal the utility of open N‐mixture models in assessing population trends of specialized river organisms in subtropical mountain environments where high‐resolution data are difficult to collect. The data also hint at possible threats to Himalayan rivers that could affect this globally unique community of river birds.

Urban Watershed Management in the Doon Valley: A Geospatial Assessment of Himalayan Watersheds

Abstract Understanding the watershed’s topography and Land Use Land Cover (LULC) is essential for developing a watershed management policy. In this research, Digital Elevation Model (DEM) data, Survey of India (SOI) Toposheet, and multispectral satellite imagery were used to analyse Himalayan rivers (Bindal and Rispana) watersheds hydrology and topography along with LULC. The morphometric analysis approach was employed for hydrological and topographical characterization, and the supervised classification method was applied to LULC classification. This study concludes that both watersheds have low to moderate relief and dendritic drainage patterns with elongated shapes. Also, compared to the Bindal watershed, whose relief ratio value is 26.59 and has a compactness coefficient value (1.92), the Rispana watershed has a higher relief ratio (69.84) and a higher compactness coefficient value (2.42), respectively, making it more susceptible to erosion and landslides. Further, based on the LULC classification, the Built-up class is the second dominant class in both watersheds, after the Forest class, with 40.36 % in the Bindal watershed and 26.83 % in the Rispana watershed. This increases biotic pressure may cause urban flooding, health risks, biodiversity loss, and ecosystem imbalance in both river systems. These findings address critical gaps in understanding urban watershed dynamics and offer valuable insights for sustainable resource management and policy formulation.

GIS and AHP-based methods for river risk zone (RRZ) assessment: a case study of the Himalayan rivers in Doon Valley, Uttarakhand, India.

Pollution from both point and non-point sources, over-extraction of freshwater, and significant climatic changes in recent years are some factors that put substantial pressure on worldwide water resources. As the demand for potable water increases globally for human, agricultural, and industrial uses, the need to evaluate the river risk assessment also increases. GIS-based studies in recent years have gained prominence as they are rapid, cheap, and provide insight into the resources for further development of research on the rivers. Therefore, the present study assessed the river risk zone (RRZ) of the Himalayan rivers in the Doon Valley of Uttarakhand in India. A combination of GIS and analytical hierarchical process (AHP) techniques was used in the present study. A total of 15 thematic layers, total dissolved solids (TDS), conductivity, pH, salinity, temperature, depth, drainage density, land use/land cover (LULC), elevation, slope, flow, width, soil type, geology, and aspect, were prepared and studied from primary survey data and open-source digital elevation model (DEM) and satellite imagery for RRZ evaluation. Weights assigned to each class are based on their characteristics and risk towards the river through the AHP method. The RRZ map thus obtained was categorized into five classes: very high, high, medium, low, and very low. The study reveals that about 56.38% of the river area is covered under high and very high-risk zones. The medium, low, and very low-risk zones are observed in 33.71%, 2.93% and 6.98%, respectively. Identifying and monitoring these risk zones give planners and decision-makers opportunities to intervene where it counts most to prevent further degradation or collapse systematically, thus preserving the health and sustainability of river systems over time.

Benthic diatoms as indicators of water quality in Sharda (Kali), a transboundary Himalayan River.

Bioassessment studies in river systems of India are rather scarce and most of the monitoring programmes still rely on the traditional physical and chemical analysis. We explored the biomonitoring potential of benthic diatoms from the Sharda (Kali) river in the Himalayas, which is due interlinking with the Yamuna River under the National River Linking Programme (NRLP) in India. Seventeen sites along the Sharda were sampled in November 2022 for the analysis of 14 physical and chemical variables and benthic diatoms. Hierarchical agglomerative cluster analysis (HACA) and principal component analysis (PCA) of the physico-chemical data set revealed two major groups of sites; the majorly unpolluted sites at higher elevations of Kumaun Himalayas (KH) and the low or moderately polluted sites of Terai Plains (TP) at lower elevations. Application of Water Quality Index (WQI) assigned a good water quality class (B) to all selected sites. A total of 31 genera including 107 species of diatoms were recorded during the present study. Achnanthes pseudoswazi, Achnanthidium minutissimum, Achnanthidium pusillum, Geissleria decussis, and Reimeria sinuata were the most abundant forms from KH whereas Gomphonema acuminatum, Cymbella excisa, Cocconeis pediculus, Nitzschia linearis, and Navicula angusta were the dominant forms recorded from TP. A decrease in diatom diversity was observed from KH to TP sites due to hydrogeomorphological changes and human interventions. Significant differences (p < 0.05 and p < 0.01) between diatom diversity index scores was observed between KH and TP sites. Diversity indices correlated significantly with important water quality variables. The results of the diatom indices such as Trophic Diatom Index (TDI), Specific Pollution Sensitivity Index (IPS), Generic Diatom Index (IDG), and Louis Leclercq Diatom Index (IDSE) corroborated well with the recorded physicochemical variables and WQI values. IPS diatom index exhibited better resolution than WQI with reference to categorization of sites and subsequent establishment of ecological status. IPS was found to be the most suitable index and could be utilized for a pre-linkage ecological status establishment for the Sharda River. However, weak correlations of diatom indices and water quality variables along with low percentage of taxa included for computation of diatom indices reiterates the importance of establishment ofregion specific autecological preferences of diatoms and subsequent formulation of a customized diatom index for the Sharda River system.

Impact of climate change on hydrological fluxes in the Upper Bhagirathi River Basin, Uttarakhand.

The Himalayan rivers are the major source of freshwater resources and have a tremendous potential for hydroelectric generation. However, assessing the water availability under climate change is challenging due to data scarcity, undulating topography, and complex climatic conditions. SWAT modeling investigates all potential consequences of variations in climate on the hydrological fluxes in the Upper Bhagirathi River Basin. Two global circulation models (GCMs) with three different climatic scenarios were employed. Quantile mapping has been used to correct the bias of GCM data. The developed model accurately simulated streamflow during calibration and validation at daily (NSE = 0.79 - 0.74, r = 0.89-0.87, and RMSE = 61.95m3/s-79.75m3/s) and monthly (NSE = 0.92 - 0.93, r = 0.96-0.97, and RMSE = 34.19m3/s-37.39m3/s) time steps. The analysis of the outcomes from MIROC6 and NorESM2-LM revealed that the rise in streamflow, surface runoff, lateral flow, and baseflow is more pronounced in MIROC6 across all three climatic scenarios. Under all scenarios, both MIROC6 and NorESM2-LM models show significant variations in snowfall and snowmelt patterns, with the area under snowfall reaching up to 51.65% for MIROC6 under SSP1-2.6 and snowmelt area peaking at 64.30% for MIROC6 under SSP2-4.5. This study's findings will offer essential insights for policymakers, practitioners, and water resource managers in developing climate-resilient strategies for sustainable water management in Himalayan catchments.

Spatiotemporal morphodynamics of an ephemeral Himalayan River impacted by sand mining: A process-response framework.

Spatiotemporal morphodynamics of an ephemeral Himalayan River impacted by sand mining: A process-response framework.

Fluvio-hydrological drivers largely control the morphology and stability of channel bars in the transboundary Himalayan River Jaldhaka

Fluvio-hydrological drivers largely control the morphology and stability of channel bars in the transboundary Himalayan River Jaldhaka

A Cluster‐Based Data Assimilation Approach to Generate New Daily Gridded Time Series Precipitation Data in the Himalayan River Basins

AbstractRecent studies show variations in precipitation‐gridded data set accuracy with changing geographical parameters. Ensemble precipitation products, combining diverse data sets, offer global‐scale effectiveness, but applying them to regional studies, particularly in small to medium‐sized sub‐basins, presents challenges in addressing precipitation dependence on specific geographical conditions. Here, we present a newly developed Clusters Based‐Minimum Error approach to assimilate different open‐source gridded precipitation data sets for forming an accurate precipitation product over small to medium‐sized hilly terrain basins, with limited precipitation gauges. This methodology generates the New Gridded Precipitation Data Set (NGPD) from 1991 to 2022 for the Upper Ganga Basin in the western Himalaya, covering approximately 22,292 km2. The study utilizes nine open‐source gridded precipitation data sets and 11 observed precipitation gauges, NGPD is evaluated through station‐wise, grid‐wise, and elevation‐wise analyses using statistical parameters, quantile‐quantile plots, daily coefficient of determination, Rainfall Anomaly Index, and seasonality/precipitation pattern analyses. Results demonstrate the superior performance of NGPD compared to other gridded precipitation sources across various evaluation metrics. Nash‐Sutcliffe Efficiency (NSE), Coefficient of determination (R2), and Root mean squared error (RMSE) range from 0.67 to 0.90, 0.73–0.93, and 4.4–10.69 mm/day, respectively, w.r.t 11 observed precipitation gauges. NGPD outperforms the widely used IMD data set in India, exhibiting a monthly scale improvement of 18.47% and 17.7% in average NSE and R2 values, respectively. Additionally, the methodology is also successfully applied to the Tamor Basin in Nepal, proving its reliability for various Himalayan regions. This approach reliably creates accurate gridded precipitation data sets for hilly sub‐basins, especially in Himalayan regions with limited station data.

Mineral Composition and Daily Mineral Intake from Freshwater Crabs: A Comparative Study of Himalayapotamon emphyseteum and Maydelliathelphusa masoniana in the Jammu division, J and K

The study explored the mineral composition of two freshwater crab species, Himalayapotamon emphyseteum and Maydelliathelphusa masoniana, native to the Himalayan river systems, specifically the Chenab and Ravi rivers. Himalayapotamon emphyseteum and Maydelliathelphusa masoniana were collected from various tributaries of the Chenab and Ravi river, which are the part of Indus River system. Mineral analysis was performed utilizing Atomic Absorption Spectroscopy (AAS) and Inductively Coupled Plasma-Mass Spectrometry (ICP-MS). The assessment revealed that these relatively unexamined shellfish are rich sources of essential minerals such as calcium, magnesium, potassium, phosphorus, aluminium, zinc, sodium, iron, selenium and manganese. These elements play a crucial role in various physiological processes, including muscle contraction, immune response, antioxidation, and blood clotting. If included in the human diet, these crabs could offer a high-quality nutrient profile that meets dietary requirements. This research highlights the potential of locally available freshwater crabs in the Jammu region as a valuable source of minerals, contributing to food security in the landlocked Himalayan areas.

Spatial Sediment Erosion and Yield Using RUSLE Coupled with Distributed SDR Model

Estimating sediment yield in a river is a challenging task in the water resources field. Different methods are available for estimating sediment erosion and yield, but generally they are not spatially distributed in nature. This paper presents the application of the Revised Universal Soil Loss Equation (RUSLE) for estimating soil erosion and integrates it with spatially distributed Sediment Delivery Ratio (SDR) to calculate sediment yield in a Himalayan river. The study area is Kabeli sub-catchment, located upstream of the Koshi River Basin in the eastern part of Nepal. The Kabeli River is where numerous hydropower projects are envisaged, and sediment-related issues are of major concern. With the use of the RUSLE, the mean annual soil erosion is estimated at 35.96 tons/ha/yr. The estimated specific sediment yield (SSY) from the distributed SDR method is 6.74 tons/ha/yr, which is close to the observed SSY of 7.26 tons/ha/yr using the data records of ~8 years. Based on correlation analysis, the topographic factor (LS) is the most sensitive RUSLE parameter with respect to sediment erosion. The sloping areas near the river hillslope are particularly vulnerable to soil erosion. The results indicate that the approach employed in this study may be potentially applied in other catchments with similar physiographic characteristics for the estimation of sediment yield.

Tectonics and climate controlled sedimentary provenance in the teesta basin since mid-holocene

Tectonics and climate controlled sedimentary provenance in the teesta basin since mid-holocene

Morphometric analysis and hydrological implications of the Himalayan River Basin, Goriganga, India, using Remote Sensing and GIS techniques

Morphometric analysis and hydrological implications of the Himalayan River Basin, Goriganga, India, using Remote Sensing and GIS techniques

Coupling the Glacio-hydrological Degree-day Model (GDM) with PCRaster for spatial dynamic modeling of Himalayan river basins

Abstract. We have seen a surge in glacio-hydrological modeling efforts in the past few decades. This form of modeling is also being carried out in the Himalayan river basins, but a comprehensive high-resolution simulation software that can be effective with a limited number of hydrometeorological data is recommended. In this regard, an open-source, scalable, flexible, and distributed modeling system called PyGDM has been developed by fully coupling the Glacio-hydrological Degree-day Model with PCRaster Python software. To evaluate the potential of using this model in the Himalayan river basins, we calibrated and then validated the model for Trishuli River basin using geographical data and the existing hydrometeorological data. The tests showed a promising result with respect to the effective application of the model in the entire Himalayan region. The PyGDM source code was optimized and adapted to the process models of glacier melting and hydrological processes in Himalayan basins. It increased the speed of the simulation, made the model highly scalable to accommodate new submodels, and enhanced the flexibility of the model to ingest various types of input data and parameters. Hence, the PyGDM model strives to simulate the glacio-hydrological processes of the entire Himalayan region.

Late Miocene Uplift and Exhumation of the Lesser Himalaya Recorded by Clumped Isotope Compositions of Detrital Carbonate

AbstractThe Himalaya orogen evolved since the Eocene as the Tethyan‐, Greater‐, Lesser‐ and Sub‐Himalaya thrust sheets were uplifted and exhumed in sequence. Reconstructing the provenance of sediment in Himalayan River systems can inform on stages in the tectonic history of the orogen. Here, we analyze the oxygen, carbon and “clumped” isotope compositions of carbonate minerals from Himalayan bedrock, Ganga River sediments and Bengal Fan turbidite deposits. We demonstrate that river sediments consist of a mixture of Himalayan‐derived and authigenic calcite precipitated in the river system. The relative abundance and clumped isotope apparent temperatures of detrital calcite in turbidite deposits decreased between the Late Miocene and Pliocene, while chemical weathering intensity did not increase during this interval. Considered together, these results reflect the establishment of the Lesser Himalaya as an important carbonate sediment source for Himalayan rivers, driven by the uplift and exhumation of this thrust sheet.

Hydrochemical characterization and pCO2 dynamics in the surface waters of Himalayan River: A case study of river Alaknanda.

Chemical weathering processes are becoming increasingly important in studies on carbon cycling because they are responsible for increased solute fluxes in the proglacial zone, can effectively sequester atmospheric CO2 and raise carbon budgets for lateral transport via rivers. Here, we examined the hydrochemical and hydrogeochemical processes, solute sources and factors controlling riverine pCO2 of the Alaknanda River and its tributaries for three sampling seasons, viz. pre-monsoon (May 2021), post-monsoon (October 2021) and winter (January 2022). The surface water is enriched with Ca2+ and Mg2+ as the dominant cations, while HCO3- and SO42- were the major anions. Gibbs's plot confirmed rock weathering as the leading mechanism in controlling the hydrochemistry of the basin. The chemical composition of river water was mainly regulated by the weathering of carbonate end members: dolomite, limestone and feldspar along with small inputs from silicate weathering. The mean pCO2 values in the mainstream (1702.7 µatm), Pindar (2267.9 µatm) and Mandakini (1136.1 µatm) revealed the streams were oversaturated with CO2 having a higher rate of exporting excess CO2 gas to the atmosphere. The study showed the persistence of high pCO2 closed system characteristics associated with increased suspended sediment concentration resulting from carbonate weathering, dominance of HCO3- over SO42- and thereby results in high values of C ratio. Principal component analysis of the water chemistry suggests that weathering contributes about 41%, while humans contribute about 13% of the ionic load to the river. This study is one of its kind to understand the system characteristics of Alaknanda River water.

Coupled role of climate and tectonics in the deposition of the late Quaternary sedimentary sequence in the southern margin of the central Ganga Plain, India

ABSTRACT The Ganga Plain’s sedimentation is primarily controlled by Himalayan tectonics, variations in monsoon intensity, and glacier size. However, the significance of intrabasinal tectonics, which is an interplay of the Himalaya tectonics and basement tectonic configuration of the Ganga Plain, in comprehending the late Quaternary Ganga Plain sedimentation remains unclear. In this study, the sediment provenance and extent of weathering experienced by the sediments are studied using the mineralogical and geochemical (major, trace, and rare earth elements) composition of a sedimentary cliff sequence exposed at the Ramnagar locality near the cratonic peripheral bulge in the southern Ganga Plain. In the Ramnagar cliff sediment section, two sediment packages, designated SP-A and SP-B, are identified based on mineralogy, texture, and geochemistry. These packages of sediments show mild chemical weathering and distinct geochemical compositions. The lower part (SP-A) of the Ramnagar cliff section is characterized by higher contributions from mafic sources (pyroxene, feldspar, and mica as dominant minerals), while the upper part (SP-B) is predominately derived from felsic sources (mica and feldspar as dominant minerals), which are supplied via the peninsular and the Himalayan rivers, respectively. The southern part of the central Ganga Plain shows evidence of a shift in the sediment provenance from mafic to felsic source rock at 40 ka. This study demonstrates how weathering and sedimentation are controlled by both regional tectonics and climate in the southern margin of the central Ganga Plain.

Optimized ensemble-based flood hazard mapping in low altitude subtropical riverine terrane

Among various natural hazards, those induced by hydrological and meteorological factors have emerged as the most frequent and damaging. India is at the second from the top, after Bangladesh, of flood hazard-affected countries of the world, causing immense damage to life and property every year. The Middle Ganga Plain in the country is one of the most severely affected regions due to the convergence of Himalayan rivers in the Ganga (Ganges) plain. This study focuses on optimizing novel ensemble models to enhance the mapping of flood hazard susceptibility in specific topoclimatic setting, characterized by a low-altitude-range, sub-tropical monsoonal climate, and a riverine floodplain environment of the tectonically active Middle Ganga Plain. This region forms part of the Ganga Foreland Basin prone to frequent floods. We employ a comprehensive flood inventory and twelve selected flood conditioning factors and is the first study that has developed these ensemble models in low relief riverine floodplain environmental setting with high resolution geomorphology as one of the conditioning factors. Four artificial intelligence ensemble models were employed in this work: Logistic Regression-Evidential Belief Function (LR-EBF), Logistic Regression-Frequency Ratio (LR-FR), Multi-Layer Perceptron-Evidential Belief Function (MLP-EBF), and Multi-Layer Perceptron-Frequency Ratio (MLP-FR). Results showed that LR-based ensembles outperformed MLP-based ensembles in the studied topoclimatic setting, with LR-EBF model achieving 87.2% and 84.7% success and prediction rates respectively. Our results reveal consistent performance differences between LR-based ensembles with FR and EBF models across different environmental settings. MLP-based ensembles, particularly with Frequency Ratio, displayed more significant performance variations. The findings underscore the importance of considering specific topoclimatic and altitudinal range environments when applying flood hazard susceptibility models. Our study also provides valuable insights for planning and policymaking in flood management practices in similar topoclimatic settings worldwide.

Climate change impact on hydropower generation and adaptation through reservoir operation in a Himalayan river, Tamor

ABSTRACT Integrated assessment of climate change impact and water resource development scenario is crucial for planning and management. In the Himalayan river basin, it is of utmost importance considering the vulnerability to climate change and the pace of water resource development. This study focused on Tamor river basin (TRB), investigating the impacts of climate change on the energy generation from hydropower projects and analyzes the adaptation through reservoir operation. Analyzing the three run-of-river (RoR) hydropower projects and a storage project, this study projects future energy generation. Results showed that RoR is highly susceptible to the impacts, demonstrated by significant reduction during pre-monsoon up to -53% and increment at annual scale up to 28%. In Tamor storage project, the particle-swarm optimization approach generated operational strategies according to altered streamflow conditions. This resulted in adaptation to the projected decrease in March-June flow through flexible operation rules, yielding positive impact on energy generation (up to +7.3% on an annual scale). The new set of rules will adapt to the flow deficit and increase the dry season flow downstream, almost by double than the historical baseline. This research highlights the significance of reservoir project and its optimized operation in effectively managing water under changing climate.