Assessing Agricultural Water Footprint and Its Implications for Sustainable Water Management in Aceh Province, Indonesia: A Case Study of Two Watersheds

Water is an indispensable natural resource that sustains life, agricultural productivity, ecosystem stability, and socio‑economic development [1]. In agrarian economies, particularly in tropical developing regions, freshwater availability directly underpins food security and rural livelihoods. In Indonesia, the agricultural sector is the largest single user of water, accounting for over 76% of withdrawals, with irrigated paddy fields as the dominant consumer [2]. This pattern is evident in Aceh Province, the primary food production hub in the western part of the country, where agriculture contributes more than 30% to the provincial gross domestic product, led by strategic commodities such as rice, coffee, and oil palm. However, increasing demands for domestic and industrial water, coupled with climate variability and deteriorating water quality, are generating mounting pressure on Aceh’s freshwater systems [2, 3].

The province’s river basins are hydrologically diverse but face similar sustainability challenges. In many areas, seasonal water deficits occur during the dry months, constraining agricultural output and threatening rural incomes. For example, in the Krueng Aceh watershed, one of the largest and most developed irrigation zones, annual irrigation demand is estimated at 23.8 million m³, yet dry-season flows are often insufficient to meet requirements, especially between February and September [4, 5]. Parallel issues are observed in other basins, including Jambo Aye, where anthropogenic pressures such as deforestation, agricultural runoff, and competition among sectors further exacerbate water stress.

Beyond scarcity, water quality deterioration from excessive agrochemical use introduces additional risks to ecosystem health. Pesticide and fertilizer residues contribute to increasing grey water footprint (WF), the volume of freshwater needed to dilute pollutants to acceptable standards [6]. This dual challenge of quantitative and qualitative stress underscores the need for integrated, evidence-based water resources management.

The concept of WF was introduced in the early 2000s and offers a comprehensive metric for quantifying direct and indirect water use across the supply chain. WF disaggregates consumption into blue WF (surface and groundwater), green WF (rainwater stored in soil), and grey WF (pollution assimilation flows) [7]. When applied to agriculture, the WF framework enables a multi-dimensional view of water consumption that links production practices with environmental impacts [7, 8]. WF assessment is closely related to the concept of virtual water, the hidden flow of water embedded in traded goods and services. By quantifying this embedded water, policymakers and stakeholders can identify crops and livestock products with disproportionate water demands, and thereby target efficiency interventions [9]. Globally, WF methods have informed irrigation modernization, crop diversification, and trade policies; however, their systematic application in Aceh has been limited.

Case studies in Aceh highlight the value of WF assessment for basin-scale planning. In the Krueng Aceh watershed, a previous study [2] calculated an average per capita WF of 608.27 m³·year^-1 in rural areas and 740.77 m³·year^-1 in urban areas, both below the global average of 1,240 m³·year^-1. Despite the relatively moderate per capita values, seasonal shortages were evident, reinforcing the need for more precise demand management. Meanwhile, in the Jambo Aye watershed, the study [2] found that water use for food consumption reached approximately 144 million m³·year^-1 for crop-based foods, with rice alone accounting for 64% of the total. Animal-derived foods contributed an additional ~17.5 million m³·year^-1, dominated by poultry meat. These findings reveal the dominance of high-water-demand commodities in the local diet and the resulting strain on water resources [1, 10].

Comparative analysis of these studies suggests that, while per capita WFs may not be excessive by global standards, the absolute volumetric pressure on local basins is substantial due to large agricultural areas and cropping patterns heavily reliant on irrigation. Furthermore, recurrent dry-season deficits indicate that storage infrastructure, water distribution efficiency, and crop choice need to be revisited in the light of WF insights. The Aceh Water Resources Master Plan (2020–2045) calls for integrated water resources management (IWRM) that balances ecological, economic, and social objectives. Although the WF framework can directly inform such planning by identifying irrigation hotspots, quantifying pollution loads, and modelling climate change scenarios, its adoption into provincial decision-making remains fragmented [6, 10]. Existing studies are largely isolated by watershed and commodity focus, with no unified, province-wide strategy. There is thus a clear research gap in harmonizing WF data across major agricultural zones and linking it to actionable management options.

However, the systematic application of the WF framework in Aceh Province faces distinct and interrelated shortcomings that limit its utility for integrated water governance. First, existing assessments are often geographically or thematically isolated, focusing on single watersheds like Krueng Aceh or on individual commodity chains such as rice or coffee. This fragmented approach results in datasets that are inconsistent in scope, methodology, and temporal resolution, making them difficult to harmonize for a comprehensive, province-wide analysis. Consequently, policymakers lack a unified evidence base to compare water pressures across different agro-ecological zones or to prioritize investments at a regional scale, as called for in strategic plans like the Aceh Water Resources Master Plan (2020-2045) [6, 10].

Second, there is a significant implementation gap between WF assessment and actionable water management. While studies may calculate volumetric footprints, they frequently stop short of translating these figures into spatially explicit, practical interventions that can be adopted by local water user associations or district agriculture offices. For instance, knowing the total grey WF for a watershed is less actionable than mapping its specific hotspots to target improved nutrient management practices. This gap prevents the seamless integration of WF science into the operational planning and monitoring frameworks of local water governance institutions.

Furthermore, the dynamic interplay between WF patterns and their underlying drivers remains inadequately explored in a unified analytical framework. The linkages between spatially identified WF hotspots, the critical seasonal variability in water availability, and key socio-economic drivers, such as traditional irrigation practices, cropping calendars, and evolving urban dietary preferences, are often studied in isolation. A lack of integrated analysis that connects hydrologic models, spatial commodity footprints, and consumption data hinders the development of robust, systems-based strategies that can simultaneously address production efficiency, consumption patterns, and climate resilience.

Building upon earlier basin-scale applications, this study seeks to comprehensively apply the WF framework to address these gaps and provide a scalable model for sustainable agricultural water management in Aceh Province. The research is designed to bridge the fragmentation between isolated studies and integrated planning through a comparative analysis of two contrasting yet strategic watersheds: Krueng Aceh and Jambo Aye. To this end, the investigation is guided by three core and sequential objectives:

1. To quantify the blue, green, and grey WFs of key agricultural commodities across the contrasting Krueng Aceh and Jambo Aye watersheds. This involves applying standardized water footprint network (WFN) methodologies to major crops: paddy rice, coconut, coffee, and livestock products: poultry and eggs, using long-term hydro-climatological data to derive representative values for each component (blue, green, grey) in cubic meters per ton.

2. To identify the biophysical and socio-economic factors that determine WF magnitude and variability. This objective moves beyond quantification to diagnose causes, examining how factors such as rainfall distribution, soil type, reference evapotranspiration (ETo), irrigation method, and farmer decision-making influence the computed footprints for different commodities and locations.

3. To produce spatial WF maps and conduct integrated hotspot analyses that enable the prioritization of management interventions. Using Geographic Information Systems (GIS), calculated WF values will be linked to crop distribution maps to visualize the geographic concentration of water use and pollution assimilation demands (grey WF). These spatial outputs will be overlaid with indices of drought vulnerability and water availability to identify critical zones where high WF coincides with high water scarcity risk, thereby pinpointing where interventions would yield the greatest impact.

Through this integrated, multi-scale analysis, which synthesizes volumetric accounting, causal diagnosis, and spatial explicitness, the study aims to develop predictive insights for sustainable water allocation under changing climatic and demographic conditions. The ultimate goal is to formulate evidence-based, spatially targeted recommendations that can directly inform local and provincial planning.

By bridging the current gaps between assessment and action, this research seeks to operationalize the WF concept as a practical decision-support tool within Aceh’s IWRM framework. This contributes directly to balancing agricultural productivity with hydrological sustainability, thereby supporting provincial water security and the achievement of key Sustainable Development Goals (SDGs), particularly Zero Hunger (SDG 2), Clean Water and Sanitation (SDG 6), and Responsible Consumption and Production (SDG 12).

This pronounced skew towards plant-based WF is consistent with the dietary structure and agricultural production profiles of the Jambo Aye Basin, where rice, coconut, and other crops are staples both for local consumption and for trade with surrounding markets. The dominance of plant-based WF is not unexpected; globally, staple crops, particularly irrigated cereals, often account for the majority of consumptive water use in agrarian economies. In the Jambo Aye context, the findings reflect two reinforcing factors: Dietary dominance of high WF Crops like Rice, which alone represents more than half of the plant-based WF, is consumed in large quantities across all socio-economic strata, and is cultivated predominantly under water-intensive continuous flooding systems. Extensive irrigated lowland agriculture, much of the basin’s prime agricultural land is devoted to irrigated paddy, with water supplied either by gravity-fed surface schemes or pumped groundwater, particularly in Aceh Timur and Aceh Utara regencies.

While the volume share of animal products is numerically smaller, their WF intensity per unit mass is substantially higher than that of most crops. This means that even small shifts in dietary preference towards meat and eggs could trigger significant increases in the basin’s total WF. For example, substituting a portion of rice calories with beef calories, despite beef’s currently low consumption levels, would multiply the embedded water demand several-fold because of the high VWC of livestock products, especially those dependent on grain-based feed [4, 12].

Within the animal-based food category, poultry products, specifically chicken meat and eggs, are the dominant contributors to the total animal WF of the Jambo Aye watershed. This dominance is primarily due to their feed conversion water intensity, meaning that a substantial proportion of their WF is indirect, embedded in the production of feed crops such as irrigated maize and soybeans. The cultivation of these feed ingredients itself consumes significant blue and green water resources, particularly under irrigated systems, and may also generate notable grey WF from nutrient runoff and pesticide residues. Consequently, even though poultry is often considered more water-efficient than ruminant livestock per kilogram of protein produced, the high production volumes and reliance on feed crops with elevated VWC significantly amplify their total WF at the basin scale.

Beef, in contrast, accounts for a much smaller share of the Jambo Aye watershed’s total WF volume. This is largely attributable to low per capita consumption observed in the study area, which keeps aggregate water use modest despite beef’s well-documented per kilogram WF being among the highest of any food commodity worldwide, often exceeding 15,000 L/kg when all water sources are accounted for [20, 21]. In this context, most cattle in the basin are raised in smallholder or semi-extensive systems utilising communal grazing, which can reduce dependence on irrigated feed. Nonetheless, any significant rise in beef demand could disproportionately escalate total WF because of its inherently high water cost per unit of edible output and its long production cycle.

Duck eggs represent the lowest WF among the animal products assessed. This relatively small footprint is partly explained by the small-scale, integrated production systems common in the Jambo Aye basin, where ducks are often herded in post-harvest rice fields or wetlands. Such systems allow ducks to forage on residual grains, aquatic plants, and invertebrates, thereby drastically reducing the need for irrigated feed crops and additional managed water inputs. While ducks inhabit aquatic environments, much of the water in these systems is ambient environmental water rather than consumptive blue water, and thus is not fully counted in WF assessments unless it is actively diverted or managed for production purposes [9, 17].

This ecological synergy between rice farming and duck rearing exemplifies a form of water-smart integrated agriculture capable of supplying nutrient-rich animal protein with minimal additional consumptive water use.

From a resource management perspective, these findings suggest that poultry products, though more efficient per kilogram of protein than beef, require careful attention to feed sourcing, with potential WF reductions achievable through local feed production utilizing low-WF crops or byproducts. Maintaining low beef consumption levels is beneficial for avoiding disproportionate increases in total basin WF; any growth in this sector should be paired with sustainable grazing management and improved feed efficiency. Traditional rice-duck integration systems exemplify a nature-based solution for animal protein production in water-limited contexts, meriting promotion and technical support to preserve their low WF advantage. Overall, the Jambo Aye animal-based WF profile underscores the importance of considering both absolute production volumes and per unit water intensities in developing sustainable food and water strategies for the basin. Shifts in dietary preferences, feed supply chains, or production systems could quickly alter the balance, with implications for both local food security and watershed hydrology.

3.3 Spatial and policy implications

The comparative analysis between the Krueng Aceh and Jambo Aye watersheds yields a number of important cross-basin insights that reveal both structural similarities and critical differences in how water is used, embedded, and traded through agricultural production. Integrating the WF calculations, broken down into blue, green, and grey components, with spatial and hydrological modelling provides a powerful lens through which to identify shared challenges and basin-specific management needs.

A consistent and compelling finding across both basins is that irrigated rice production is the single most significant driver of blue WF. In each watershed, rice alone accounts for between 40-57% of total food-related WF, with production heavily dependent on traditional continuous flooding irrigation systems. This reliance on season-long inundation not only inflates consumptive blue water use through evaporation and seepage losses but also intensifies dry-season competition between agriculture, domestic supply, and ecological flow requirements. The alignment of this pattern in both basins underscores rice as the critical leverage point for blue water savings.

Another clear pattern involves processing-based products, particularly soy-based foods like tempe and tofu, and coffee. Though produced and consumed in lower volumes than staples like rice, these commodities exhibit disproportionately high total WF values relative to their harvested weight. This is because WF accounting encompasses not only cultivation, often with significant blue and green components from irrigated soybean production, but also the indirect water embedded in their raw inputs. Regarding grey WF: wet processing of soy products and coffee does generate organic-rich wastewater, and if effluent pollutant-load data and the relevant water quality standards are available, this processing stage can legitimately contribute to a grey WF estimate via the standard dilution formula. However, in the absence of measured wastewater concentration data for the processing stage in this study, grey WF for these commodities was calculated from agrochemical runoff during soybean and coffee cultivation only. The discussion of their large total WF should therefore primarily reference the blue and green WF from high-VWC soybean cultivation, and not attribute the grey WF directly to processing operations.

For animal products, while the absolute volumetric contribution to basin WF is far lower than that of plant foods, the per-kilogram WF is markedly higher. Poultry meat and eggs dominate the animal WF profile in both basins due to the substantial indirect water demand embedded in feed production, which relies on irrigated maize and soybeans. Even with low beef consumption in these basins, the per-unit WF of ruminant products remains among the highest for any food, meaning that dietary shifts toward more beef could sharply elevate total water demand.

The diagnostic results align closely with the goals of the Aceh Water Resources Master Plan (2020-2045), which calls for IWRM that is both ecologically and economically balanced. This convergence suggests that WF assessment should be embedded as a core operational tool for water governance in Aceh’s agricultural sector. Specifically, both basins would benefit from transitioning away from continuous flooding to AWD or SRI methods. Field trials indicate potential blue WF reductions of 20-40% without yield penalties. Complementary infrastructure measures, such as lining canals to reduce conveyance losses, could amplify these savings. Crop diversification toward low WF species, promoting and incentivizing the cultivation of lower water demand crops such as cassava, sweet potato, or certain pulses, can reduce pressure on scarce water during peak deficit months and enhance resilience to climate-induced variability.

Demand-side measures, awareness campaigns, and targeted education could shift consumption patterns toward lower WF foods, reducing aggregate demand. This is especially relevant for high-WF animal products or processing-intensive foods, where small reductions in consumption generate disproportionately large water savings. Hydrological modelling has shown that seasonal deficits in water availability coincide with the projected intensification of dry-season droughts under climate change scenarios. This calls for the development of storage infrastructure (dams, on-farm reservoirs) and conjunctive use systems that integrate surface and groundwater to buffer seasonal imbalances.

Both basins act as net exporters of virtual water through the trade of high WF commodities like rice, coconut, and coffee. While economically beneficial in the short term, this effectively represents a net loss of local water resources. Policy frameworks should assess whether current trade patterns are compatible with long-term water security goals, particularly in light of population growth and climate variability. Moreover, incorporating spatially explicit WF hotspot mapping into annual water allocation planning can ensure that interventions are targeted where water savings yield the highest returns, both in volumetric and socio-economic terms. This is particularly critical for avoiding maladaptation, such as displacing rice production from one water-scarce sub-basin to another without net water savings.

By systematically embedding WF analysis into Aceh’s IWRM framework linked to rural development, trade policy, and climate adaptation planning, the province has the opportunity to align food security with water security, ensuring that agricultural growth does not come at the expense of long-term hydrological stability.

This dominance stems from rice's blue water intensity under continuous flooding regimes, coupled with its centrality in local diets. The persistence of traditional flooding, despite its high water demand, is driven by a combination of factors: entrenched agricultural practices and knowledge systems that prioritize perceived yield security and pest control; limited access to capital and technical knowledge for adopting water-saving technologies like AWD; and irrigation infrastructure designed for basin-wide flooding rather than controlled distribution. This creates a significant lock-in effect, where shifting away from flooding is perceived as both technically and economically risky by farmers [11, 21].

Beyond rice, other high water demand plant commodities in Jambo Aye include coconut (11.32 million m³·year^-1) and soy-based processed foods (tempe: 11.25 million m³·year^-1; tofu: 7.86 million m³·year^-1), whose elevated total WF is primarily driven by the high VWC of their soybean inputs, which represents a substantial blue and green WF from cultivation. The processing stage also generates organic-rich wastewater that, in principle, would contribute to grey WF through effluent dilution requirements; however, because wastewater pollutant-load data for the processing stage were not collected in this study, the grey WF component for tempe and tofu has been estimated from soybean cultivation agrochemical runoff only, following standard WFN methodology. The elevated WF of these commodities should therefore be understood primarily in terms of cultivation-related blue and green water use, not processing water consumption per se. Horticultural crops such as coffee, chillies, leafy greens, and melons also contribute sizeable volumes, particularly in districts with commercial market linkages. Animal products add a smaller proportion of the total WF by volume but exhibit much higher per-unit water intensities. Chicken meat and eggs dominate this category, reflecting the embedded water in feed grain production.

Spatial hotspot analysis pinpoints geographic clustering of high WF demand: in Krueng Aceh, peri-urban irrigated rice zones around Aceh Besar and Banda Aceh score highest in KDE; in Jambo Aye, Aceh Timur's eastern floodplain concentrates plant WFs (rice, coconut), while Bener Meriah's highlands are prominent for animal WFs (poultry, eggs).

A critical finding from the spatial analysis is the strong correlation between grey WF hotspots and specific agro-ecological conditions. These hotspots, identified in intensive paddy and vegetable zones, are not merely a function of crop choice but are intrinsically linked to local fertilization practices and soil types. In lowland clay-rich paddy soils, which are dominant in the floodplains of Aceh Timur and Krueng Aceh, high rates of nitrogen fertilizer application, common in the pursuit of high-yield rice varieties, coupled with poor nutrient management and continuous flooding, lead to significant leaching and runoff.

The fine texture of these soils can limit initial infiltration but, under saturated conditions, promotes the lateral movement of nutrient water into drainage canals. Conversely, in upland vegetable zones (parts of Bener Meriah), grey WF hotspots are associated with coarse-textured, sandy loam soils. These soils have high permeability, facilitating the rapid leaching of soluble nitrates and pesticides from the frequent and intensive fertilizer and pesticide applications typical of commercial vegetable production. Thus, the spatial pattern of grey WF is a direct diagnostic map of areas where current nutrient management practices are mismatched with hydrological and soil conditions, highlighting a priority for implementing targeted BMPs such as controlled-release fertilizers, split application timing, and improved irrigation scheduling to reduce pollutant loads.