Debnath et al. (2026) Impacts of Climate Change and Demographic Growth on Future Water Supply and Demand Gap in a River Basin

Identification

• Journal: Water Resources Management
• Year: 2026
• Date: 2026-02-23
• Authors: Mridusmita Debnath, Ashok K. Mishra
• DOI: 10.1007/s11269-025-04471-5

Research Groups

• ICAR-National Institute of Secondary Agriculture, Namkum, Ranchi, Jharkhand, India
• Agricultural Engineering Department, Indian Institute of Technology Kharagpur, Kharagpur, West Bengal, India

Short Summary

This study developed a Water Evaluation And Planning (WEAP) model for the Kesinga Sub Catchment of the Mahanadi River basin in India to assess future water supply-demand gaps under climate change and demographic growth, finding significant unmet domestic water demand (up to 20%) in specific demand sites by the 2030s, particularly during lean periods.

Objective

• To compare spatially downscaled CMIP5 General Circulation Model (GCM) outputs (precipitation, maximum and minimum temperature) for a base period (1981–2010) and future climatology (2011–2100).
• To develop a WEAP model using regional climate variables for generating future streamflow scenarios.
• To assess the contribution of population growth and climate change on scenario-based quantitative seasonal variations of future water supply and demand gaps for 2011–2100.

Study Configuration

• Spatial Scale: Kesinga Sub Catchment (KSC) of the middle reaches of the Mahanadi River basin, India, covering an area of 11,794 km². The KSC is divided into four major sub-catchments within the districts of Nabarangpur, Kalahandi, Bolangir, and Nuapada in Orissa.
• Temporal Scale:
  • Historical/Base Period: 1981–2010 for climate data; 1991–2010 for population and water demand baseline.
  • Future Periods: 2011–2040 (2030s), 2041–2070 (2060s), and 2071–2100 (2090s).
  • Data Resolution: Daily for meteorological and streamflow data; monthly for model simulations and GCM outputs.

Methodology and Data

• Models used:
  • Water Evaluation And Planning (WEAP) model for hydrological simulation and water allocation.
  • CSIRO-Mk3-6-0 General Circulation Model (GCM) (CMIP5 outputs) for climate projections.
  • Bruce Seymor (2004) model for population projection.
• Data sources:
  • Meteorological data: Daily rainfall, maximum and minimum temperature from India Meteorological Department (IMD), Bhubaneshwar centre (2000–2009).
  • Streamflow data: Daily streamflow from Central Water Commission (CWC), Bhubaneshwar (2000–2009).
  • Topographic data: SRTM Digital Elevation Model (30 m x 30 m resolution).
  • Land Use/Land Cover (LULC): LANDSATTM ETM+ satellite images (2005, 30 m x 30 m resolution) from Global Land Cover Facility (GLCF).
  • Soil data: Soil type map from National Bureau of Soil Survey and Land Use Planning, Kolkata (1:250,000 resolution).
  • Population data: Census, Government of India (1991, 2001, 2011).
  • Water use rates: WHO recommendation (135 L per capita per day for domestic), Directorate of Economics and Statistics, Ministry of Agriculture (DESMOA), and Ministry of Water Resources reports for agriculture.
  • GCM outputs: CSIRO-Mk3-6-0 GCM outputs for historical (1981–2010) and future (2011–2100) under Representative Concentration Pathways (RCPs) 2.6, 4.5, 6, and 8.5 (1.8653° × 1.875° resolution).

Main Results

• The WEAP model showed satisfactory performance for monthly streamflow simulation, with a Nash-Sutcliffe model efficiency (NSE) of approximately 92% and an Index of Agreement (IOA) of approximately 98%.
• Mean annual temperature is projected to increase by 0.29 °C by the end of the 21st century across all RCP scenarios, with RCP2.6 showing the lowest increase and RCP4.5/RCP8.5 showing the highest in different periods.
• Annual precipitation is projected to increase by a mean of 39% by the end of the 21st century. However, significant decreases are expected during monsoon months (August and October in 2030s; August, September, and October in 2060s and 2090s), while pre-monsoon months (e.g., May) could see increases of up to 1000%.
• Annual streamflow is expected to increase under all RCPs, except for RCP2.6 in the 2030s, with prominent monthly increases from May to August.
• Annual domestic water demand is projected to rise significantly; for instance, Demand Site-1 (DS-1) demand is expected to increase from 22,000,000 m³ in 1991 to 38,000,000 m³ by 2100.
• A water supply-demand gap is projected, with domestic water demand remaining unfulfilled in specific periods. For RCP4.5 in the 2030s, Demand Site-4 (DS-4) faces a 20% unmet annual demand, and Demand Site-3 (DS-3) faces a 1.4% unmet annual demand, particularly during early summer (March and April). This implies reduced water availability for agricultural activities.

Contributions

• Developed and applied a novel framework integrating watershed hydrological simulation and water supply-demand analysis to assess the combined impacts of climate change and population growth in an upstream river basin.
• Provided quantitative, scenario-based projections of future water availability and demand, identifying specific vulnerable periods and demand sites within the Kesinga Sub Catchment.
• Highlighted the critical importance of managing water supply-demand gaps in upstream areas for sustainable water resources management and overall basin growth.
• Offered practical, science-led recommendations for decision-makers to mitigate drought impacts, including increasing groundwater extraction, implementing water pricing, promoting treated water use, and enhancing rainwater harvesting.

Funding

This research did not receive any financial support from funding agencies in any public, commercial, or non-profit organization.

Citation

@article{Debnath2026Impacts,
  author = {Debnath, Mridusmita and Mishra, Ashok K.},
  title = {Impacts of Climate Change and Demographic Growth on Future Water Supply and Demand Gap in a River Basin},
  journal = {Water Resources Management},
  year = {2026},
  doi = {10.1007/s11269-025-04471-5},
  url = {https://doi.org/10.1007/s11269-025-04471-5}
}