Nagashree et al. (2025) Evaluating sectoral water use and precipitation variability on blue water scarcity under historical and future climate conditions in the Mahi River Basin

Identification

• Journal: Agricultural Water Management
• Year: 2025
• Date: 2025-11-21
• Authors: G.E. Nagashree, Ashutosh Sharma
• DOI: 10.1016/j.agwat.2025.110006

Research Groups

• Department of Hydrology, Indian Institute of Technology Roorkee, Roorkee, Uttarakhand 247667, India

Short Summary

This study quantifies the blue water scarcity index (WSIbw) in the Mahi River Basin, India, by integrating sectoral water withdrawals and precipitation variability under historical and future climate conditions. It finds that agriculture is the primary driver of scarcity, and future dry years are projected to intensify water stress by over 60% in some upper-basin districts.

Objective

• To quantify the Blue Water Scarcity Index (WSIbw) in the Mahi River Basin (MRB) during the historical period (1981–2015).
• To analyze the sector-specific contributions of agriculture, industry, and domestic withdrawals to overall blue water scarcity.
• To assess the influence of precipitation variability on blue water scarcity under historical, near-future (2031–2065), and far-future (2066–2100) climate scenarios across multiple Shared Socioeconomic Pathways (SSP1-2.6, SSP3-7.0, and SSP5-8.5).

Study Configuration

• Spatial Scale: Mahi River Basin (MRB), India, covering 34,184 square kilometers, analyzed at grid cell (0.5° × 0.5°) and district levels, delineated into upper and lower sub-basins.
• Temporal Scale: Historical (1981–2015), near-future (2031–2065), and far-future (2066–2100) periods.

Methodology and Data

• Models used: H08 model (grid-based large-scale hydrology and water resources model).
• Data sources: Inter-Sectoral Impact Model Intercomparison Project (ISIMIP) Phase 3a (historical) and 3b (future) protocols. Historical simulations used climate datasets: 20CRv3, 20CRv-ERA5, 20CRv-W5E5, and GSWP3-W5E5. Future simulations used five General Circulation Models (GCMs): GFDL-ESM4, IPSL-CM6A-LR, MPI-ESM1–2-HR, MRI-ESM2-0, and UKESM1-0-LL, under Shared Socioeconomic Pathways (SSPs): SSP1-2.6, SSP3-7.0, and SSP5-8.5. Blue water scarcity index (WSIbw) calculated using the Variable Monthly Flow (VMF) approach for environmental flow requirements.

Main Results

• Historically (1981–2015), over 80% of districts in the Mahi River Basin experienced blue water scarcity (WSIbw > 1), with downstream districts like Vadodara and Anand facing the highest stress, reaching a maximum WSIbw of 7.5.
• Agriculture is the dominant driver of blue water scarcity, contributing approximately 70% of total water withdrawals, significantly exceeding domestic and industrial demands.
• Sectoral water withdrawals showed a statistically significant increase (p < 0.05) during 1981–2015, with irrigation withdrawals rising from 2.3 × 10^9 cubic meters per year in 1981 to 3.7 × 10^9 cubic meters per year in 2015.
• Precipitation variability strongly influences WSIbw; dry years (precipitation anomalies less than -1 standard deviation) lead to WSIbw increases of 20–30% above the multi-year average, while wet years (anomalies greater than +1 standard deviation) show significant decreases.
• Future climate projections (2031–2100) indicate increased water scarcity, particularly during dry years. Far-future conditions (2066–2100) show larger deviations than the near-future (2031–2065), with some upper-basin districts (e.g., Dhar, Chittaurgarh, Udaipur) projected to experience dry-year stress increases exceeding 60%. Conversely, some districts like Anand and Vadodara show relative decreases in WSIbw change coefficients, indicating a complex spatial response.

Contributions

• Provides a robust and transferable diagnostic framework that integrates sector-specific water withdrawals with precipitation variability across historical and future climates.
• Decomposes blue water scarcity into its anthropogenic (agriculture, industry, domestic) and climatic (precipitation-driven) drivers, offering a more detailed understanding than aggregate basin-level assessments.
• Offers novel insights into how sectoral water use and climate variability jointly shape blue water scarcity in semi-arid basins.
• Informs adaptive and sustainable water management strategies by highlighting spatial disparities and the amplified severity of dry-year water deficits under future climate change.

Funding

• Prime Minister’s Research Fellowship (PMRF) from the Ministry of Human Resource Development, Government of India (Grant no. PM-31-22-766-414).
• Support from IIT Roorkee.

Citation

@article{Nagashree2025Evaluating,
  author = {Nagashree, G.E. and Sharma, Ashutosh},
  title = {Evaluating sectoral water use and precipitation variability on blue water scarcity under historical and future climate conditions in the Mahi River Basin},
  journal = {Agricultural Water Management},
  year = {2025},
  doi = {10.1016/j.agwat.2025.110006},
  url = {https://doi.org/10.1016/j.agwat.2025.110006}
}