Optimizing water footprints and yield sustainability in Boro rice through alternate wetting and intense drying: A climate-resilient strategy for Bangladesh Open Access

Climate change and water scarcity pose significant challenges to rice production in Bangladesh, necessitating water-efficient practices. This study, conducted during the 2024 Boro rice season in Mymensingh, Bangladesh, compared the impacts of alternate wetting and intense drying (AWID), with irrigation at a 20-cm water level drop, against continuous flooding (CF) and alternate wetting and moderate drying (AWMD), with a 15 cm drop. The AWID resulted in 46.12% water savings and a 43.1% increase in crop–water productivity, yielding 5.10 t/ha, while AWMD saved 38.64% water with a yield of 6.13 t/ha. Despite a 22.7% yield reduction compared to CF (6.60 t/ha), AWID's superior water efficiency underscores its potential as a sustainable option in water-scarce regions. Excluding the first 15-day crop establishment phase, the water footprint was lowest for AWMD (1003.83 L/kg) and AWID (1079.68 L/kg) compared to CF (1439.00 L/kg). Climate projections for the 2040 and 2070s indicate increased temperatures, decreased rainfall, and higher evapotranspiration, potentially raising irrigation demands by up to 30% under RCP 8.5 scenarios. These water-saving techniques offer promising strategies for sustaining rice production while conserving water resources. Further research is recommended to optimize these practices across diverse agro-ecological zones, enhancing climate resilience in rice cultivation.

Rice (Oryza sativa L.) is critical to global food security, serving as the staple food for over half the world's population (Fageria 2007; Bin Rahman & Zhang 2023; Akter et al. 2025). With more than three billion consumers worldwide, its significance as a dietary cornerstone cannot be overstated (Munmun et al. 2024). Cultivated in 114 countries, with over 50 producing at least 100,000 tons annually (Wuthi-Arporn 2009), rice occupies more than 146.5 million hectares of agricultural land globally (Lampayan et al. 2015). To meet growing population demands, rice yields must increase by over 1% annually (Normile 2008). However, rice cultivation faces significant challenges due to its high water requirements. As a semi-aquatic plant, rice demands substantial water throughout its growth cycle, regardless of variety or geography, creating difficulties in regions with insufficient rainfall and intense competition for limited water resources (Bouman 2007; Ali et al. 2016; Datta et al. 2017; Islam et al. 2024). Traditional rice farming, particularly in flooded paddy soils, consumes significantly more water than other cereal crops (Chapagain et al. 2011; Akter et al. 2025; Patle & Panggeng 2024). Rice requires between 700–1,500 mm of water per cropping season (Reddy et al. 2016) and demands 2,000–5,000 l to produce 1 kg of grain, depending on environmental conditions (Surendran et al. 2021).

In Bangladesh, rice forms the cornerstone of the nation's dietary sustenance and nutritional stability, accounting for approximately 75% of caloric intake and 65% of protein consumption for its 170 million people (BBS 2018–19; Milovanovic & Smutka 2018). Among the three major rice seasons – Aus, Aman, and Boro – Boro rice has emerged as the most critical for ensuring a stable and sufficient food supply for the population. Contributing over 50% of the country's total rice production (Islam et al. 2022), Boro cultivation ensures year-round rice availability, bridging gaps left by the rainfed Aman and Aus seasons, which remain vulnerable to monsoon variability (Ahmed et al. 2013; Kamruzzaman et al. 2025). The crop's reliance on irrigation during the dry winter season (November–May) allows it to circumvent rainfall uncertainties, making it essential for stabilizing domestic rice supply (Bell et al. 2015). However, this irrigation dependency also renders Boro rice highly susceptible to escalating water scarcity. With groundwater depletion rates exceeding recharge in key agricultural regions (Mukherjee et al. 2018; Islam et al. 2023) and projected climate-driven reductions in dry season rainfall (Shahid 2011), sustaining Boro productivity is pivotal to averting food crises. Any disruption in Boro production could directly threaten the food security of millions, particularly smallholder farmers who constitute 70% of Bangladesh's agricultural workforce (Rahman et al. 2024). Thus, optimizing water use in Boro rice cultivation represents not merely an agronomic concern but a strategic imperative for national stability.

Water scarcity is a pressing global concern, with irrigation agriculture consuming over 70% of the world's fresh water – a demand expected to increase to meet future food security needs. Drought exacerbates this scarcity, leading to the drying of water sources such as lakes, rivers, and seasonal streams, and reducing irrigated rice yields (Kang et al. 2021). Freshwater scarcity is further intensified by population growth, industrial development, and environmental pollution (Bouman 2007; du Plessis 2019). In Asia, where over 75% of the world's rice is produced using conventional irrigation practices, water remains the most critical element for sustainable rice production (Bhuiyan 1992; Prasad et al. 2017). Conventional rice cultivation practices, particularly the continuous flooding (CF) method, are increasingly scrutinized for their high water consumption and environmental impact (Awal 2020; Zhang et al. 2020). CF maintains a continuous water layer in rice fields, benefiting weed control and nutrient availability but resulting in substantial water wastage through surface runoff, percolation, and evaporation (Tuong et al. 2005; Surendran et al. 2021). Moreover, CF contributes to methane emissions, a potent greenhouse gas, exacerbating climate change (Shrestha & Shrestha 2017; Hussain et al. 2020). Bangladesh exemplifies these challenges, with rice covering 75% of cultivated land and providing the primary caloric source (Milovanovic & Smutka 2018). Its tropical monsoon climate creates water management difficulties, with 63% of rice areas depending on irrigation (Ahmed et al. 2013; Bell et al. 2015; Kamruzzaman et al. 2025). Despite averaging 2,300 mm annual rainfall, only 20% occurs during December–May – the critical Boro rice-growing season (Islam et al. 2022) – proving insufficient for crop requirements and negatively impacting growth and productivity.

Bangladesh is already experiencing the adverse effects of climate change, including increased frequency of droughts, erratic rainfall patterns, and rising temperatures (Sikder & Xiaoying 2014; Kabir et al. 2024; Rahman et al. 2024). Studies indicate that climate change will exacerbate water scarcity in South Asia, with significant reductions in groundwater recharge and increased monsoon rainfall variability (Shahid 2011; Mukherjee et al. 2018). Mukherjee et al. (2018) projected that groundwater depletion in the Indo-Gangetic Plain, including parts of Bangladesh, could reduce irrigation water availability by up to 25% by 2050. Additionally, rising temperatures are expected to increase crop water requirements, further intensifying pressure on water resources (Acharjee et al. 2017). The Intergovernmental Panel on Climate Change (IPCC) has emphasized the importance of adapting agricultural practices to mitigate climate change impacts (Porter et al. 2014; Suresh et al. 2025). In this context, water-saving techniques like alternate wetting and drying (AWD) are not merely beneficial but imperative for Bangladesh, as they directly address the dual challenges of escalating water scarcity and climate-driven yield instability by reducing irrigation dependency.

To enhance water efficiency in rice irrigation, alternative strategies such as AWD are being widely adopted across Asia, including Japan, China, and India (Carrijo et al. 2017; Qun et al. 2017; Busari et al. 2019; Zhou et al. 2025). Unlike CF, AWD employs intermittent irrigation, reducing water losses through seepage and percolation while improving root oxygenation and nutrient uptake (Carrijo et al. 2017; Norton et al. 2017; Deng et al. 2021). Meta-analyses indicate that AWD can reduce water use by 15–32% compared to CF, although its effects on yield remain debated (Carrijo et al. 2017; Chu et al. 2018; Hossain et al. 2019; Islam et al. 2022; Akter et al. 2025). Among AWD variants, alternate wetting and moderate drying (AWMD) – irrigating at a 15 cm water level drop – was chosen for its demonstrated balance between water savings (20–30%) and minimal yield penalties, making it viable for moderately water-stressed regions (Chu et al. 2015; Zhang et al. 2021). Conversely, alternate wetting and intense drying (AWID) triggered at a 20 cm drop, representing a more aggressive adaptation strategy tailored for areas facing acute aquifer depletion and prolonged dry spells, as projected under RCP 8.5 scenarios (Chu et al. 2018; Mukherjee et al. 2018).

However, under projected climate scenarios for Bangladesh – characterized by intensified dry spells and aquifer depletion – more aggressive strategies like AWID may be necessary. AWID delays irrigation until the water level reaches 20 cm below the ground, promoting deeper root growth and enhancing resilience to prolonged drought (Chu et al. 2018). The selection of AWID, AWMD, and CF as focal treatments directly responds to Bangladesh's gradient of water scarcity: CF represents status-quo inefficiency, AWMD offers a transitional solution for moderate stress, and AWID addresses extreme scarcity scenarios. This tripartite comparison fills a critical gap in understanding trade-offs between water conservation intensity and yield sustainability, particularly under Bangladesh's unique agro-climatic conditions, where groundwater depletion rates exceed 25% in key regions (Mukherjee et al. 2018). Despite its potential, AWID's reliance on frequent irrigation limits its suitability in areas with acute water scarcity. Preliminary studies report significant water savings and yields comparable to CF and AWMD (Chu et al. 2018), but its impacts on water footprints (WFs), yield stability, and climate resilience – particularly in Bangladesh's agro-ecological context – remain underexplored.

Building on this context, the present study addresses three unresolved questions: (1) Can AWID surpass AWMD in water savings without disproportionately reducing yields? (2) How do WFs, as sustainability indicators, differ across irrigation regimes? (3) What are the implications of climate projections for scaling these practices in water-scarce regions? Focusing on escalating water scarcity in Mymensingh, Bangladesh (Islam et al. 2022), this research evaluates AWID against CF and AWMD through field experiments, assessing water efficiency, yield outcomes, and WF metrics. Integrated climate modeling further projects the viability of these practices under future climatic conditions. The findings aim to bridge knowledge gaps in sustainable rice cultivation, offering actionable insights for stakeholders in Bangladesh and analogous regions. Successful implementation of optimized practices like AWID could align with national efforts to rehabilitate irrigation systems and expand paddy cultivation while mitigating climate-driven water demand. Through rigorous analysis of trade-offs between water conservation, yield, and resilience, this study seeks to inform adaptive strategies for sustainable agriculture amid intensifying water scarcity and climate change.

The BRRI dhan88 rice variety, with a growth period of about 140 days, was selected for this study. Seedlings, 32 days old, were obtained from the BAU experimental farm in Mymensingh, Bangladesh, on January 21, 2024, and transplanted later that same afternoon. During land preparation, fertilizers were applied at the following rates: urea (N) at 90 kg/ha, triple superphosphate (TSP) at 31 kg/ha, muriate of potash (MP) at 49 kg/ha, zinc sulfate (ZnSO₄) at 5 kg/ha, and gypsum at 37 kg/ha. Nitrogen fertilizer was administered in three equal top-dressings. Irrigation was provided according to the treatment requirements, and weed control was conducted twice during the rice-growing season. The mature crop was harvested following standard procedures when 90% of the seeds had turned golden yellow. To assess yield-contributing factors, a 1 m² section of the field was harvested on April 29, 2024. Measurements such as plant height, the number of effective tillers per hill, and leaf area were taken at four different growth stages. Both rice grains and straw were sun-dried separately until a consistent weight was achieved, with the grain moisture content reaching approximately 14%. Data on grain yield, straw yield, and the weight of 1,000 grains were recorded for each plot.

To address uncertainties in future climate projections, it is essential to use a range of possible climate change scenarios rather than relying on a single projection (Yang et al. 2024). Future climate conditions were projected using three general circulation models (GCMs): BCC-CSM1-1-M (Beijing Climate Center Climate System Model, version 1.1, Moderate Resolution), HadGEM2-ES (Hadley Centre Global Environment Model, version 2 – Earth System), and MIROC5 (Model for Interdisciplinary Research on Climate, version 5). These models were selected based on their effectiveness in evaluating climate change impacts (Nashwan & Shahid 2020; Salman et al. 2020). However, GCMs typically operate at coarse spatial resolutions, ranging from 100 to 300 km, which limits their applicability for localized agricultural studies. To address this, the scenarios were developed under two representative concentration pathways, RCP 4.5 and RCP 8.5, representing moderate and high emission trajectories, respectively. Data on minimum and maximum temperatures, precipitation, wind speed, and solar radiation were prepared for the 2040s (2026–2055) and 2070s (2056–2085) timeframes. Since relative humidity projections were not available from the GCMs, it was assumed to remain constant, based on baseline conditions, for the future scenarios in crop-water modeling purposes.

The evaluation of selected GCMs indicates varying degrees of accuracy in simulating historical climate patterns when compared with weather station data from 2007 to 2023 (Table 2). Given the significant impact of precipitation and temperature on crop water requirements (Bannayan et al. 2011; Acharjee et al. 2017), model performance is evaluated based on these variables. Under RCP 8.5, the BCC-CSM1-1-M model demonstrates excellent predictive accuracy for precipitation, with the highest R² value (0.987), showing a strong correlation between modeled and observed data. Models projecting precipitation under RCP 8.5 consistently outperform their RCP 4.5 counterparts, with R² values from 0.969 to 0.987 and NSE scores between 0.940 and 0.953, underscoring their robust reliability (Tebaldi & Knutti 2007). While the MIROC5 model performs adequately, it shows lower NSE scores, indicating variability in performance. Temperature projections match historical data closely, with R² values above 0.79 for minimum and 0.80 for maximum temperatures across all models and scenarios. PBIAS values are within acceptable limits, especially for temperature (below 8%), suggesting minimal systematic error (Lamichhane et al. 2024). MAE values for temperature predictions are low, ranging from 0.940 to 1.524 °C for minimum temperatures and from 0.991 to 1.254 °C for maximum temperatures, reflecting strong model accuracy. These findings support a multi-model ensemble approach, which effectively addresses uncertainties in climate projections, providing a solid foundation for climate impact assessments (Wang et al. 2014; Yersaw & Chane 2024).

Additionally, the reference crop evapotranspiration (ET₀) was calculated using both baseline climate data (2000–2023) and future projections, employing the Penman–Monteith method via the FAO's CROPWAT model v.8.0 (Soomro et al. 2023). The potential crop water requirement (ΣET_C) and the potential irrigation requirement (ΣET_C − ER) for crop evapotranspiration were also determined using this model. For this analysis, crop-specific data such as crop coefficients for different growth stages, rooting depth, crop height, critical depletion levels, and yield response factors for dry season Boro rice were sourced from the Bangladesh Agricultural Research Institute. This comprehensive assessment aids in understanding the implications of irrigation water management practices in the face of climate change.

A one-way analysis of variance (ANOVA) was conducted using Statistix software v.10.0 to investigate the impact of various irrigation treatments on growth, yield attributes, WUE, WFs, and water productivity of irrigated rice. To differentiate between treatment groups, the least significant difference (LSD) test was applied at a significance level of 0.05.

Plant height consistently increased across all treatments from 50 to 100 DAT, with CF maintaining the highest values throughout (Figure 6(a)). At 100 DAT, CF resulted in the tallest plants, followed by AWMD and AWID, aligning with Carrijo et al. (2017), who reported that CF promotes greater plant height in rice. The differences in plant height among treatments became more pronounced as the season progressed, indicating water availability's crucial role in stem elongation and overall plant growth (Oliver et al. 2019). While AWID promotes deeper root growth and enhances drought resilience, the associated reduction in shoot elongation and plant height suggests that water stress influences cell expansion and internode elongation (Zhang et al. 2021). In addition, tiller count per hill peaked at 71 DAT during the reproductive stage and slightly declined towards harvest (Figure 6(b)). CF consistently produced the highest tiller count, followed by AWMD and AWID, consistent with Norton et al. (2017), who found that AWD can slightly reduce tiller production compared to CF. This reduction in tiller count under AWMD and AWID can be attributed to temporary water stress, which affects the initiation and survival of tillers (Zhang et al. 2021). A lower tiller count under AWID is primarily attributed to water stress-induced reductions in cytokinin activity, which influences tiller bud initiation (Silwal et al. 2020). Since effective tiller number is a key determinant of yield, reductions in tillering under AWID contribute to observed yield penalties, as fewer tillers result in fewer panicles per unit area (Chu et al. 2018). However, this reduction must be balanced against AWID's substantial water savings, as improving water productivity in water-scarce regions is a priority (Zhou et al. 2025). The decline in tiller numbers after 71 DAT is attributed to natural tiller senescence and resource reallocation to grain filling (Prathap et al. 2019).

In addition, LAI rapidly increased from 50 to 71 DAT, and then gradually declined towards harvest for all treatments (Figure 6(c)). CF maintained the highest LAI throughout the season, which is crucial for photosynthesis and overall crop productivity (Silwal et al. 2020; Zhou et al. 2025). The reduced LAI values observed in AWMD and AWID, particularly during the later stages of growth, indicate that water-saving irrigation methods might cause earlier leaf senescence, which could impact grain filling (Qun et al. 2017; Zhou et al. 2025). A decline in LAI under AWID suggests that intense drying conditions may accelerate senescence due to increased ethylene production and stomatal regulation in response to water stress (Datta et al. 2017). This could impact grain filling efficiency, particularly if stress occurs during the reproductive phase (Kumar et al. 2019). Physiologically, prolonged water deficits in AWID and AWMD likely trigger stomatal closure to reduce transpiration, thereby limiting carbon assimilation and accelerating leaf senescence through ethylene and abscisic acid signaling pathways (Datta et al. 2017; Mote et al. 2022). Early senescence reduces the photosynthetic duration, limiting carbohydrate translocation to grains and potentially compromising yield stability over successive seasons (Kumar et al. 2019; Zhang et al. 2021). While this adaptive response may prioritize resource remobilization from leaves to grains under acute stress (Deng et al. 2021), recurrent water deficits could deplete vegetative reserves, impairing root vitality and soil organic matter turnover, thereby affecting long-term soil–crop health (Bouman 2007; Islam et al. 2024).

Panicle characteristics (Table 3) showed no statistically significant differences among treatments, indicating that water-saving techniques did not severely impact these attributes. Panicle length ranged from 18.84 ± 0.61 cm (AWMD) to 19.89 ± 0.70 cm (CF), with AWID (19.88 ± 0.48 cm) nearly matching CF, suggesting panicle development is relatively resilient to moderate water stress (Chu et al. 2018). The number of filled grains per panicle showed a slight decrease from CF (82.44 ± 10.90) to AWMD (79.30 ± 6.99) and AWID (76.97 ± 6.15), aligning with Hossain et al. (2019), who reported that water-saving techniques might slightly reduce grain filling. The number of unfilled grains per panicle was lowest in AWMD (8.65 ± 1.44), followed by AWID (9.18 ± 1.01) and CF (12.16 ± 2.61), suggesting that moderate drying cycles might improve grain filling efficiency (Zhang et al. 2020; Zhou et al. 2025).

Overall, the trends in growth attributes across irrigation treatments reflect the physiological responses of rice plants to water availability. CF provides optimal conditions for vegetative growth, leading to taller plants with more tillers and larger leaf areas (Munmun et al. 2024). However, water-saving techniques (AWMD and AWID) may induce mild water stress, prompting plants to allocate resources more efficiently towards reproductive growth and grain filling, potentially at the expense of vegetative growth (Datta et al. 2017; Chu et al. 2018). The trade-off between early senescence and yield sustainability warrants attention, as repeated cycles of intense drying may exacerbate oxidative stress, reduce rhizosphere microbial activity, and diminish nutrient uptake efficiency over time (Hussain et al. 2020; Akter et al. 2025). The lack of significant differences in panicle characteristics indicates that rice plants can adapt to moderate water stress without severely compromising growth attributes (Silwal et al. 2020).

Table 4 presents crucial data on yield and yield components – 1,000-grain weight, grain yield, straw yield, and harvest index – under three irrigation regimes: CF, AWMD, and AWID. The 1,000-grain weight showed slight variations across treatments, with CF producing the heaviest grains (20.67 ± 1.15 g), followed by AWID (19.67 ± 0.58 g) and AWMD (19.00 ± 1.00 g). However, these differences were not statistically significant, suggesting that water-saving irrigation techniques did not substantially impact grain filling. This finding aligns with research by Carrijo et al. (2017), who observed in their meta-analysis that AWD practices generally had minimal effects on grain weight. Despite the significant reduction in tiller count under AWID, individual grain weight remained relatively stable, indicating a potential compensatory mechanism where available assimilates are directed towards grain filling rather than additional tiller production (Zhou et al. 2025). However, the lower tiller count ultimately leads to a reduced number of panicles per unit area, explaining the overall yield decline observed under AWID (Table 4).

Grain yield showed significant differences among treatments, with CF producing the highest yield (6.60 ± 0.28 t/ha), followed by AWMD (6.13 ± 0.34 t/ha) and AWID (5.10 ± 0.35 t/ha). The yield reduction in AWMD (7.1%) and AWID (22.7%) compared to CF is within the range reported by Lampayan et al. (2015) and Carrijo et al. (2017), who documented yield reductions of 5–15% under AWD in various Asian countries. The yield reduction in AWID was primarily driven by reduced tillering and a lower panicle density per unit area, confirming that water stress during tiller initiation significantly impacts yield formation (Norton et al. 2017). The more substantial yield reduction in AWID also suggests that intense drying cycles may impact yield more severely than moderate drying, a finding also reported by Chu et al. (2018). Straw yield followed a similar pattern to grain yield, with CF producing the highest (5.53 ± 0.64 t/ha), followed by AWMD (4.92 ± 0.62 t/ha) and AWID (4.11 ± 0.48 t/ha). These statistically significant differences indicate that water-saving techniques affect both grain and biomass production. The reduced straw yield under AWID is consistent with findings by Hossain et al. (2019) and Islam et al. (2022), which attributed lower vegetative biomass accumulation to intermittent water stress, reducing canopy expansion and dry matter partitioning to straw. Interestingly, the harvest index remained relatively constant across treatments (0.55 ± 0.01–0.56 ± 0.03), with no significant differences. This stability in harvest index under different water regimes, noted by Hossain et al. (2019) and Munmun et al. (2024), indicates that rice plants may have mechanisms to prioritize grain production even under water stress.

Overall, the interrelation between these yield components provides insights into the plant's response to water-saving irrigation. For instance, the maintenance of 1,000-grain weight and harvest index despite reductions in overall yield suggests that the yield decrease is primarily due to fewer grains per unit area rather than smaller or less filled grains. This aligns with findings by Islam et al. (2022), who observed that AWD primarily affected tiller number and panicle density rather than individual grain characteristics.

The total irrigation applied varied significantly among treatments, with CF requiring the highest amount (86.26 ± 1.59 cm), followed by AWMD (52.93 ± 2.22 cm) and AWID (46.36 ± 0.99 cm) (Table 5). This translates to substantial water savings of 38.64 ± 2.35% for AWMD and 46.12 ± 1.05% for AWID compared to CF (Figure 7). These findings suggest that the current AWD strategies surpass previous AWD regimes reported in earlier studies, which achieved water savings of 15–30% (Carrijo et al. 2017). The more pronounced water savings in AWID demonstrate the potential for significant water conservation through intense drying cycles (Chu et al. 2018). Moreover, the WUE varied significantly among the irrigation treatments, with AWMD exhibiting the highest WUE at 0.10 ± 0.002 t/ha/cm, followed by AWID at 0.09 ± 0.005 t/ha/cm, and CF showing the lowest at 0.07 ± 0.004 t/ha/cm (Table 5). This trend aligns with findings from previous studies, such as Carrijo et al. (2017), who reported that AWD practices could improve WUE by up to 20% compared to CF. The higher WUE in AWD treatments can be attributed to reduced water input and improved root development, as suggested by Bouman et al. (2007). These findings indicate that despite potential yield reductions, water-saving techniques substantially improve the efficiency of water use in rice production, consistent with findings by Zhang et al. (2021) and Islam et al. (2022).

The analysis of WFs revealed that the GWF was highest for AWID (167.71 ± 11.40 L/kg), followed by AWMD (139.37 ± 7.41 L/kg) and CF (129.30 ± 5.54 L/kg) (Table 5). It is important to note that while green water use (i.e., effective rainfall) was considered constant across all irrigation regimes in this study, the variation in GWF was primarily due to yield differences. For a more accurate estimation of GWF, considering crop evapotranspiration, runoff, seepage, and percolation losses, it is recommended to employ lysimeter experiments for all irrigation methods, as suggested by Islam et al. (2024). Interestingly, Norton et al. (2017) revealed that intermittent irrigation during the production period might lead to more efficient use of rainfall, potentially due to improved soil water retention and root development. This finding indirectly supports the results of GWF demonstrated herein and directly aligns with the higher WUE observed in AWD treatments in the current study, suggesting that these techniques may offer additional benefits beyond just water conservation. Additionally, the BWF showed a contrasting trend, with CF having the highest value (1,309.71 ± 80.88 L/kg), significantly higher than both AWMD (864.47 ± 12.19 L/kg) and AWID (911.97 ± 48.84 L/kg) (Table 5). This substantial difference in BWF under water-saving techniques aligns with findings by Lampayan et al. (2015) and Surendran et al. (2021). It is important to note that the water used for managing weed growth during the crop establishment phase, where a consistent depth of 5 cm was maintained across all plots for the first 15 DAT, was excluded from the BWF estimates and overall irrigation water use calculations for all treatments. The TWF followed a similar pattern to BWF, with CF showing the highest value (1,439.00 ± 86.43 L/kg), significantly greater than both AWMD (1,003.83 ± 19.18 L/kg) and AWID (1,079.68 ± 59.89 L/kg) (Table 5). These results align with findings from Chu et al. (2018) and Islam et al. (2024), who demonstrated that AWD and specific-days interval-based intermittent irrigation water-saving techniques could significantly reduce overall water consumption in rice cultivation.

While AWID resulted in a more significant yield penalty compared to AWMD, its higher water productivity (0.92 ± 0.05 kg/m³) compared to CF (0.65 ± 0.04 kg/m³) suggests that it remains a viable option under extreme water scarcity conditions (Figure 7). The trade-off between tiller count reduction, yield decline, and water conservation must be carefully considered when selecting irrigation strategies for different agro-ecological zones. The ability of rice plants to adapt to moderate water stress while still maintaining efficient grain filling suggests that AWID could be a climate-smart strategy for ensuring food security in regions with declining water availability (Deng et al. 2021).

Overall, the interrelation between these water use parameters offers valuable insights. The higher WUE and water productivity in AWMD and AWID, despite potential yield reductions, are directly linked to significant reductions in total water use. This suggests that there may be a trade-off between maximizing water savings and maintaining optimal yield levels, as observed by Datta et al. (2017). The balance between water conservation and yield optimization remains a crucial consideration in adopting AWD practices. Additionally, the trade-off between GWF and BWF under different irrigation regimes is also notable. Water-saving techniques increase GWF while substantially reducing BWF, leading to a net reduction in TWF. This shift in water use patterns could have important implications for water resource management in rice-growing regions, potentially easing pressure on irrigation sources. Furthermore, the increased reliance on green water under AWD techniques aligns with du Plessis (2019), who highlighted the importance of optimizing rainfall use in sustainable agriculture.

The dry season in Bangladesh (November–April), which coincides with Boro rice cultivation, is expected to witness a decline in rainfall. Both RCP 4.5 and RCP 8.5 scenarios predict decreased rainfall during the key months of Boro rice growth, from transplanting to harvesting (January–April), in the 2040s and 2070s compared to the baseline period (2000–2023), with few exceptions (Figure 8(a)). For example, under RCP 8.5 in the 2040s, rainfall in March and April is projected to decrease by approximately 33–43% relative to the baseline, while in the 2070s, this reduction is estimated to be around 20–35%. These projections align with the findings of Sikder & Xiaoying (2014), who projected more frequent and severe droughts in Bangladesh as a consequence of climate change. Temperatures are projected to rise significantly (Figures 8(b) and 8(c)). By the 2070s under RCP 8.5, monthly average maximum temperatures could increase by up to 16–19 °C in January-April, reaching nearly 38 °C in April on average. The monthly average minimum temperatures show a similar warming trend, with increases of 10–18 °C across all months by the 2070s. This warming trend is consistent with projections by Rahman et al. (2024) for Bangladesh and will likely lead to higher evapotranspiration rates and increased crop water demand. Moreover, the ET₀ is projected to increase substantially, especially during the Boro season (Figure 8(d)). By the 2070s under RCP 8.5, ET₀ in April could increase by approximately 0.66 mm/day (around 14% increase) compared to the baseline. This increase in ET₀, coupled with reduced rainfall, will exacerbate water scarcity during the critical rice-growing period.

The implications of these climatic changes on rice cultivation are evident in the projections of crop water requirements (ΣET_C) and irrigation requirements (ΣET_C – ER) for the Boro season (Figure 9). The potential crop water requirements are projected to increase by around 7 and 15% for the 2040 and 2070s, respectively, under RCP 8.5 (Figure 9(a)). This increase is primarily driven by higher temperatures and evapotranspiration rates, as observed in previous studies (Soomro et al. 2023). More critically, the potential irrigation requirements are projected to increase dramatically, by about 21 and 30% for the 2040 and 2070s, respectively, under RCP 8.5 (Figure 9(b)). This substantial increase in irrigation needs is due to the combined effect of increased crop water requirements and reduced effective rainfall during the growing season, aligning with findings by Shrestha & Shrestha (2017) for rice in Nepal under climate change scenarios.

These projections underscore the critical importance of water-saving techniques like AWMD and AWID for sustainable rice production. Field experiments demonstrated significant water savings with AWMD (38.64 ± 2.35%) and AWID (46.12 ± 1.05%) compared to CF, which becomes even more valuable considering projected increases in potential irrigation requirements of up to 30% by the 2070s (Table 5). Furthermore, the improved WUE observed with AWMD (0.10 ± 0.002 t/ha/cm) and AWID (0.09 ± 0.005 t/ha/cm) compared to CF (0.07 ± 0.004 t/ha/cm) suggests these techniques can maintain or improve rice productivity under future water-scarce conditions, aligning with findings by Carrijo et al. (2017) that AWD practices could improve WUE by up to 20% compared to CF. For Bangladeshi farmers, the trade-off between yield reduction (7.1% for AWMD and 22.7% for AWID compared to CF, Table 4) and water savings requires contextual evaluation, as the benefits of water conservation may outweigh moderate yield losses, particularly in water-stressed regions where preserving groundwater reserves through AWID ensures long-term agricultural viability amid aquifer depletion (Lampayan et al. 2015; Rahman et al. 2024). Policymakers must address socioeconomic barriers to adoption – such as reduced short-term profitability – through subsidies or crop insurance, as highlighted by Lampayan et al. (2015). Scaling AWID and AWMD across Bangladesh's diverse agro-ecological zones requires tailored adjustments to drying thresholds and irrigation schedules; in saline-affected coastal zones, AWID could mitigate saltwater intrusion by reducing irrigation frequency, while in heavy clay soils of floodplains, shorter drying cycles (AWMD) may prevent excessive cracking (Ahmed et al. 2025; Kamruzzaman et al. 2025). Enhancing adaptability would require soil-specific calibration coupled with farmer training on groundwater monitoring tools, while multi-stakeholder collaborations integrating local knowledge with technical guidance are critical for context-specific implementation, as proposed by Islam et al. (2022). Balancing these trade-offs is crucial for climate adaptation, as optimizing WUE sustains both water resources and farm livelihoods under escalating scarcity (Datta et al. 2017; Zhou et al. 2025), with Datta et al. (2017) noting that finding the optimal balance between water savings and yield maintenance will be essential for adapting rice cultivation to climate change.

Moreover, the observed improvements in root development and soil water retention under AWD practices (Norton et al. 2017) could prove particularly beneficial in coping with the projected increases in temperature and evapotranspiration rates. The deeper root systems developed under AWMD and AWID may allow rice plants to access water from deeper soil layers, enhancing their resilience to drought conditions. The shift in water use patterns observed in the study, with increased reliance on green water (rainfall) under AWD techniques (Table 5), aligns well with the projected changes in rainfall patterns. As dry season rainfall becomes scarcer and variable, techniques that optimize the use of available rainfall, such as AWMD and AWID, will become increasingly valuable for sustainable rice production. In conclusion, the projected climate changes for North-central Bangladesh highlight the urgent need for adapting rice cultivation practices, particularly for the water-intensive Boro season. Water-saving techniques like AWMD and AWID offer promising solutions for maintaining rice production while conserving water resources. Their implementation, coupled with continued research on optimizing these techniques for future climate conditions, will be crucial for ensuring food security and sustainable agricultural development in Bangladesh and similar rice-growing regions facing climate change challenges.

This study provides valuable insights into the potential of AWMD and AWID for water conservation in rice cultivation. However, several limitations must be acknowledged, along with key directions for future research. First, the experiment was conducted over a single growing season in a specific agro-ecological zone (Old Brahmaputra Floodplain), limiting the generalizability of the findings. As Carrijo et al. (2017) emphasized, the effectiveness of AWD techniques varies significantly with soil type, climate, and management practices. To enhance the robustness of these findings, future studies should implement long-term, multi-site trials across diverse agro-ecological zones, capturing variations in soil texture, organic matter content, and groundwater table depth (Chu et al. 2018). Such broader investigations would facilitate the refinement of AWD strategies for different environmental contexts.

Another key limitation arises from site-specific climatic and edaphic conditions, which may not fully represent all rice-growing regions in Bangladesh. Seasonal climatic fluctuations, including variations in dry season rainfall and temperature extremes, could influence the reproducibility of results. While meteorological data from a nearby weather station were used to monitor climate conditions, microclimatic variations within the field might have introduced inconsistencies in evapotranspiration rates, soil moisture retention, and crop response. These factors underscore the need for future studies to assess interannual climatic variability and its impact on AWD irrigation efficiency. Moreover, the controlled experimental setting differs from real-world farm conditions, where irrigation practices vary due to differences in water source availability, field slope, and soil infiltration capacity. Scaling up AWD techniques requires evaluating their adaptability under practical farming scenarios. To address these challenges, future research should incorporate multi-location trials spanning multiple growing seasons to validate the general applicability of AWD-based irrigation strategies.

Furthermore, while this study focused on WUE and yield components, additional research should explore critical parameters like soil health, nutrient dynamics, and greenhouse gas emissions under various irrigation regimes (Kumar et al. 2019). Such investigations are essential to capture the full spectrum of environmental benefits and trade-offs, as emphasized by Surendran et al. (2021), who stressed the need to examine the broader ecological impacts of water-saving technologies in rice cultivation. Moreover, exploring AWMD and AWID's effects on rice grain quality would provide practical insights for farmers and consumers alike. As Mote et al. (2022) demonstrated, AWD practices can influence grain quality attributes, such as protein content and amylose concentration, which are critical for market acceptance and nutritional value.

To enhance our understanding of WFs and better comprehend water dynamics within the soil-plant-atmosphere continuum, future research should incorporate lysimeter experiments. These provide precise measurements of evapotranspiration, deep percolation, and crop water use, offering a clearer picture of water balance components under varying irrigation regimes. As suggested by Islam et al. (2024), lysimeters can help partition water use into productive (transpiration) and non-productive (evaporation, percolation) components, leading to a more nuanced understanding of WUE. This, in turn, can aid in refining irrigation scheduling and optimizing AWD systems. Additionally, while this study examined three irrigation treatments, there is significant potential for exploring a broader range of water management strategies. Zhang et al. (2021) demonstrated the benefits of integrating AWD with optimized fertilizer management to improve both water and nitrogen use efficiency. Future research could extend this by investigating the synergies between AWD and other conservation practices such as conservation tillage, mulching, or intercropping systems, potentially leading to the development of more holistic and sustainable rice production systems.

The economic feasibility of scaling up AWMD and AWID techniques was not addressed in this study, which leaves an important research gap. Lampayan et al. (2015) pointed out the significance of socioeconomic considerations in the adoption of water-saving technologies. Future studies should include cost–benefit analyses and investigate the practical challenges farmers face when adopting such irrigation practices. This could be facilitated through participatory research and surveys, providing deeper insights into farmers' perspectives on AWD practices. Moreover, the exploration of incentive programs or policy interventions could yield valuable strategies for promoting AWD adoption, thus supporting policymakers and agricultural extension services in advancing water-saving technologies.

Although climate change projections were considered in this study, future research could benefit from more detailed modeling of crop-climate interactions under different irrigation regimes. Integrating crop growth models with downscaled climate projections, as suggested by Soomro et al. (2023), could offer more precise estimates of future water requirements and crop yields under various management scenarios. Using advanced crop simulation models such as ORYZA or DSSAT (Alejo 2021), combined with ensemble climate projections, could provide a clearer understanding of the long-term sustainability of AWD practices in the face of climate change. Such models could also identify tipping points where existing water management strategies may no longer suffice, thus informing the development of more resilient irrigation practices.

In conclusion, while this study provides a solid foundation for understanding AWMD and AWID's potential in sustainable rice cultivation, addressing these limitations and pursuing the proposed research directions is critical for developing comprehensive, climate-resilient strategies for rice production. As Porter et al. (2014) emphasized in the IPCC report, adapting agricultural practices to climate change requires a multi-faceted approach, integrating agronomic, environmental, and socioeconomic considerations. Addressing these gaps will facilitate the development of more sustainable and efficient water management systems, ultimately contributing to food security and water resource sustainability in a changing global climate.

This study demonstrates the substantial potential of AWID and AWMD irrigation strategies in optimizing water use while maintaining viable rice yields under escalating water scarcity in Bangladesh. Compared to CF, the most notable findings reveal that AWID reduced irrigation water use by 46.12% and increased crop-water productivity by 43.1%, despite a 22.7% yield reduction. AWMD, on the other hand, achieved a balanced approach, saving 38.64% water with only a 7.1% yield decline, making it particularly suitable for regions experiencing moderate water stress. The TWF for both AWID and AWMD was 25–30% lower than CF, primarily due to reduced dependence on blue water. These results highlight the critical role of water-saving practices in mitigating groundwater depletion, particularly under climate projections indicating a 30% rise in irrigation demand by the 2070s due to rising temperatures and erratic rainfall. The implications of these findings extend beyond agronomic efficiency: AWID and AWMD offer scalable climate-resilient strategies for Bangladesh's diverse agro-climatic zones. In regions with acute aquifer depletion, AWID's superior water efficiency could preserve groundwater reserves despite yield trade-offs, while AWMD provides a transitional solution for areas with moderate water stress. Policymakers must prioritize context-specific adaptations, such as adjusting drying thresholds in saline-prone coastal zones or heavy clay soils, to maximize adoption. However, the trade-off between water conservation and yield necessitates socioeconomic interventions, including subsidies or crop insurance, to incentivize farmers facing short-term profitability challenges.

This study acknowledges limitations inherent to its single-season, single-location experimental design, which may not fully capture long-term soil health dynamics or interannual climatic variability. The controlled experimental conditions also differ from real-world farming scenarios, where factors like field slope and water source accessibility influence irrigation efficacy. Future research should address these gaps through multi-site, multi-season trials across Bangladesh's agro-ecological zones, integrating assessments of soil nutrient dynamics, greenhouse gas emissions, and grain quality under varied drying regimes. Additionally, economic feasibility studies and participatory farmer surveys are critical to understanding adoption barriers. In conclusion, this work provides a robust foundation for climate-resilient rice cultivation, emphasizing that strategic water management is indispensable for reconciling food security with groundwater sustainability. By balancing immediate agronomic trade-offs with long-term resource conservation, AWID and AWMD can serve as cornerstones of adaptive strategies in Bangladesh and other water-scarce rice-growing regions globally.

Conceptualization contributed by M.T.I.; methodology contributed by M.T.I., M.A.R.A., N.J.; Formal analysis and investigation contributed by M.T.I., M.A.R.A., N.J., M.H.J., S.S.S.; Writing – original draft preparation contributed by M.T.I., M.A.R.A., M.H.J., S.S.S.; Writing – review and editing contributed by N.J., M.M.R., K.F., A.K.M.A.; Funding acquisition contributed by M.T.I.; Supervision contributed by A.K.M.A.

The authors gratefully acknowledge the financial support provided by the Bangladesh Agricultural University Research System (BAURES), Bangladesh, under Grant No. 2023/1936/BAU. The authors extend their gratitude to the anonymous reviewers for their valuable comments and thoughtful suggestions on the manuscript.

All the authors approve the participation in the manuscript.

All the authors approve the publication of manuscript.

This manuscript has not been submitted to another journal for simultaneous consideration. The submitted work is original and has not been published elsewhere in any form or language, either partially or in full.

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The authors declare there is no conflict.