Water Stress Analysis Considering Climate Change Scenarios in Semi-Arid Regions Using WEAP Model
This study utilizes a calibrated WEAP model driven by CMIP6 climate projections to demonstrate that Multan District, Pakistan, faces a structurally pre-existing water stress that will intensify by 2055 under all climate scenarios, with agriculture dominating stress in moderate pathways and domestic demand overtaking it under high-warming conditions, necessitating urgent integrated management interventions before 2035.
Original paper licensed under CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). This is an AI-generated explanation of the paper below. It is not written or endorsed by the authors. For technical accuracy, refer to the original paper. Read full disclaimer
Fresh water is the lifeblood of human civilization, yet in many parts of the world, the amount of water people need is steadily outpacing the amount nature provides. This imbalance, known as water stress, occurs when the demand for clean water consistently exceeds the available supply. In semi-arid regions, where rainfall is scarce and unpredictable, this problem is particularly acute. These areas rely heavily on irrigation to grow food and on groundwater to sustain cities, but rising temperatures and shifting weather patterns are making the situation worse. As the planet warms, the air holds more moisture, causing soil to dry out faster and crops to thirst for more water. At the same time, growing populations and expanding cities demand more water for daily life. The result is a tightening squeeze on resources that threatens food security, economic stability, and the well-being of millions.
In the southern Punjab province of Pakistan, the Multan District stands as a stark example of this struggle. For decades, this region has faced a chronic shortage of water, with farmers and residents already competing for a supply that falls short of their needs. To understand how this crisis might evolve in the coming decades, researchers Muhammad Moaz Munawar, Atiq Ur Rehman Tariq, and Amjad Masood turned to a sophisticated computer modeling tool called the Water Evaluation and Planning system, or WEAP. This tool acts like a digital twin of a real-world water network, allowing scientists to map out rivers, canals, and fields, and then simulate how water flows through them under different conditions. By feeding the model with historical data and future climate predictions, the team could test how the district's water system would hold up against the combined pressures of a changing climate, a growing population, and shifting farming habits.
The researchers focused their study on the period from 2015 to 2055, looking at three distinct future pathways based on global climate scenarios. These pathways range from a future where the world takes strong action to limit warming, to a "business as usual" path where emissions continue to rise unchecked. They also accounted for the specific realities of Multan, where the landscape has been rapidly changing. Between 2010 and 2020, the area dedicated to water-intensive crops like rice and sugarcane exploded, while the population surged and urban areas expanded. The team first calibrated their model using real-world data from 1990 to 2020, ensuring that the computer's predictions matched the actual flow of water in the region's canals. Once the model was tuned to reflect reality, they let it run forward in time to see what the future held.
The simulations revealed a troubling trajectory. Even without any new climate changes, the total demand for water in Multan is projected to skyrocket, rising from roughly 1,449 million cubic meters in 2015 to nearly 4,944 million cubic meters by 2055. This surge is driven by a perfect storm of factors: more people needing water for drinking and sanitation, a massive expansion in the area planted with thirsty crops like sugarcane and rice, and a hotter climate that causes water to evaporate from the soil more quickly. The study found that the region is already facing a structural deficit, meaning that even today, the water available is not enough to meet the needs of the district, leaving a gap of nearly 849 million cubic meters. This gap is currently being filled by pumping groundwater at an unsustainable rate, causing the water table to drop by half a meter to a full meter every year.
As the simulations moved into the future, the gap between supply and demand widened significantly under all climate scenarios. By 2055, the amount of water that goes unmet—meaning the demand that cannot be satisfied by available supplies—is expected to reach between 22 and 38 million cubic meters per year, depending on how much the planet warms. Interestingly, the study showed that the source of the stress changes over time. In the earlier decades and under moderate warming scenarios, the biggest shortfall comes from agriculture, as farmers struggle to water their expanding fields. However, under the most extreme warming scenario, where temperatures rise by more than two degrees Celsius, the dynamic shifts. By the 2040s, the demand for domestic water from the growing population becomes the primary driver of the shortage, overtaking agriculture. This happens because extreme heat drives up the amount of water each person needs for cooling and hygiene, while the rapid urbanization of the district adds millions of new residents to the system.
The research also highlighted a counterintuitive finding regarding the relationship between climate action and water stress. The scenario with moderate warming, which assumes a middle-of-the-road approach to development, actually resulted in the highest agricultural water deficit. This is because this specific path includes a moderate increase in the area of land used for farming, which, when combined with the extra heat, creates a massive demand for irrigation that the water supply cannot meet. In contrast, the most extreme warming scenario, while devastating for domestic water needs, showed a slightly lower agricultural deficit because the assumptions for that path included different land-use patterns. This suggests that the way we manage our land and crops is just as critical to water security as the amount of greenhouse gases we emit.
Ultimately, the study concludes that water stress in Multan is not a future problem waiting to happen; it is a present reality that will only intensify. The simulations indicate that without urgent and integrated interventions, the district will face a severe water crisis before 2035. The window to act is narrow, as the combination of rising temperatures, depleting groundwater, and peak population growth will converge to create a situation where the water supply simply cannot keep up with the demand. The findings point to the need for a multi-sector approach that goes beyond simply building more infrastructure. It requires a fundamental shift in how water is managed, from improving the efficiency of irrigation to better regulating groundwater use and planning for a future where the needs of a growing population must be balanced against a shrinking resource base. The path forward depends on making difficult choices today to ensure that Multan remains a place where people can live and thrive tomorrow.
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