The frequent occurrence of dry spells, heatwaves, and water scarcity takes a toll on green infrastructure, particularly in arid and semi-arid regions. Water-absorbing polymers (WAPs) have the potential to minimise the effects of water stress on plant growth. It can absorb and store large amounts of water and release it when water is unavailable in the soil matrix. This study conducted experimental and numerical research on a novel water-absorbing polymer derived from waste-generated fly ash, aiming to improve the drought resistance of vegetated soils, with a focus on root water uptake () dynamics. The fundamental goal of this research is (1) to establish the efficacy of WAP-amended soil on grass species under water stress conditions and (2) to estimate the from soil under the effect of . The results demonstrate that the improved water retention behaviour by altering water storage in the soil matrix. The water retention characteristics, such as plant-available water content and wilting time, were improved by more than 2 times and 1.2 times, respectively, compared to the control soil. Furthermore, it is observed that WAP-amended soil has higher from the soil matrix. This study suggests that can be utilised for a variety of applications, including green infrastructure and agricultural practices.