The role of Kampar watershed in achieving sufficient rice production and sustaining agriculture

Global challenges such as the climate crisis, population growth, urbanization, and agricultural resource limitations are contributing to the emergence of food scarcity on a global scale. World Food Programme (2022) provides an explanation that there was a notable rise in the global population experiencing hunger, with figures increasing from 650 to 768 million individuals in 2020. Furthermore, this upward trend persisted in 2021, with the number of individuals facing hunger further escalating to 828 million. According to projections, there is an anticipated decline of 20% in agricultural output and an average decrease of 15% in yields in developing nations by the year 2080 (Anggraeni 2020; Goncharova & Merzlyakova 2022). This decline is attributed to the impact of climate change, specifically the occurrence of water scarcity (Ali et al. 2021; Daszkiewicz 2022; Habib-ur-Rahman et al. 2022).

Indonesia encounters a significant difficulty in ensuring the provision of enough food supply to its population. To date, Indonesia has struggled to effectively meet the nutritional requirements of its population (Widada et al. 2017; Vadilaksono et al. 2023). The agricultural sector in Indonesia makes a significant contribution of 13.70% to the country's gross domestic product (GDP), positioning it as the second largest sector after the industry sector, which accounts for 19.88% of the GDP. Rice continues to dominate the modern landscape of agricultural production, serving as a primary means of ensuring food availability (Widada et al. 2017; Bashir & Yuliana 2019). Based on the statistics provided by the Central Statistics Agency of Riau Province (2022) in 2021, the total area of rice fields in Indonesia amounts to 10.4 million hectares, with an annual production of 54.4 million tons (Central Statistics Agency of Riau Province 2021). Rice exhibits the highest level of production in comparison to other food commodities. The cultivation of rice is heavily reliant on the availability of water resources due to the substantial amount of water required for the farming process, which exceeds the water demands of other agricultural commodities (Ikhwali et al. 2022), and both maximum and minimum temperature exhibit favorable effects on the output of rice (Dhamira & Irham 2020). This finding suggests that temperature exerts a significant influence on both the quality and quantity of rice yield.

According to the research conducted by Zuhdi (2021) utilizing a Klassen typology analysis, it has been determined that the agricultural sector has significant potential for development and is poised to make a substantial economic contribution to the region of Riau. Nevertheless, the prevailing circumstance entails that most of the rice consumed in the Riau province is sourced from external regions, notably West Sumatra, while only a minor fraction originates from local production. The annual reduction of rice production in Riau province persists. The districts in Riau have a prevailing trend of negative production patterns, characterized by a consistent reduction (Yulianda & Harini 2020). In the Riau province, there has been an annual decrease in rice production by 2.23% (Indonesian Ministry of Agriculture 2020). The rice production in Riau province had a decline from 389,188 tons in 2014 to 314,448 tons in 2022 (Central Statistics Agency of Riau Province 2023). A multitude of variables has been implicated in the decline of production, encompassing diminished planting area, subpar productivity, environmental influences, and pest infestation, including water availability that is highly dependent on rainfall (Fahri et al. 2014; Ramli & Bahri 2015; Isyandi 2016; Rustam 2019).

It is imperative to acknowledge the significance of water availability for rice plants, given that the agricultural sector accounts for most of the water consumption. The World Economic Forum (2013) stated that sustainable water management is seen as a significant concern in the twenty-first century, with supply shortfall being recognized as one of the most serious hazards confronting the society. According to the OECD (2012), over 1.6 billion individuals currently reside in areas characterized by significant water stress. Projections indicate that by the year 2050, this figure is expected to rise to 3.9 billion people. The distribution of this share exhibits regional disparities, with estimates of agricultural water usage ranging from 40% in countries with industrialized economies that rely on food imports to over 95% in nations where agriculture serves as the dominant economic sector (FAO 2014). Hence, it is crucial to acknowledge the significance of water regulation in the context of rice farming. In the study area, particularly in Kampar regency, according to the findings of Pratiwi & Yuwati (2022), water deficit still occurs during certain months, where the water content is lower than the water requirements for rice crops. In addition, during specific months such as July and August, there is a high level of drought in the Kampar watershed (Darfia & Rahmalina 2019). Insufficient water availability in rice crops can lead to the deterioration and reduction of rice yield, hence impacting food security (Dinar et al. 2019; Surendran et al. 2021; Mallareddy et al. 2023).

Numerous studies have addressed the adoption of sustainable agricultural practices in relation to the management of water resources. Isyandi (2016) did a study about potential food crop production and food security in the Kampar regency of Riau province. Their findings showed that agricultural land, the number of seeds, fertilizers, insecticides, and labor, both partially and simultaneously, affect the food security in the Kampar district. Pascual & Wang (2016) examined the effects of water management on rice varieties, yield, and water productivity within the context of the system of rice intensification (SRI). One noteworthy aspect of their findings is that not all characteristics of the SRI exert an influence on the development and production of rice plants. Nevertheless, a significant obstacle in the pursuit of sustaining and augmenting rice output lies in the fulfillment of water requirements. Dinar et al. (2019) conducted a review to assess the adequacy of the present freshwater supply in meeting the requirements of agricultural crops, given the persistent implications of water scarcity. Yusuf et al. (2020) conducted a study to ascertain the ecological conditions of rice farming and examine the index and ecological sustainability status of lowland rice farming in the Siak district, Riau. Kusumawardani & Permana (2021) conducted a study to assess the water requirements in the agricultural sector, with a specific focus on rice cultivation. Their findings indicate that the demand for water in this sector, particularly for rice plants, exceeds the allocated water resources on the island of Java. However, the available data on the management of rice farming in Riau are currently insufficient, specifically in the context of water use, which poses challenges in developing appropriate models for sustainable farming management. This research is essential for informed decision-making regarding the optimal utilization of water resources for sustainable rice farming, particularly in the Kampar watershed. This study not only examines the water footprint (WF) but also proposes the identification of regions appropriate for agricultural expansion by considering the WF and water balance.

The method for determining the numerical value of each WF (blue, green, and gray) is described in the following sections.

The crop coefficient, denoted as Kc, is a parameter that integrates plant attributes and the overall impact of soil evaporation. The reference ET, represented as ETo (measured in millimeters per month), was determined using the Penman–Monteith method within the CROPWAT 8.0 software. This calculation incorporated climate data sourced from multiple agencies.

The quantification of green water consumption, referred to as CWU green, necessitates the assessment of crop ET (ETc) and effective rainfall (Peff) at a minimum. The measurements for both of these variables are denoted in cubic meters per hectare (m³/ha) and are calculated using CROPWAT 8.0 software. The data utilized in ETc modeling encompass various factors, including monthly average, maximum and minimum temperatures, relative humidity, wind speed, and duration of sunlight. The term ‘effective rainfall’ (Peff) refers to a small portion of rainfall retained by the soil and potentially utilized by plants to fulfill their water requirements. The strategy employed in the CROPWAT model to calculate Peff is the USDA Soil Conservation Service method. Meanwhile, the variable Y represents the yield of the agricultural crop.

The data processing in this investigation was conducted utilizing Excel and CROPWAT software, as described in previous studies by Altobelli et al. (2015, 2019). Calculation of the WF entails evaluating the carrying capacity of water resources through an analysis of water availability in the Kampar watershed. This analysis employs a water balance model, specifically the Mock method, which incorporates various data points such as rainfall, ET, ground surface water balance, soil storage and groundwater storage, soil moisture capacity, water surplus, and river flow (runoff).

The rice output and rice field area within the Kampar watershed, encompassing Kampar and Pelalawan regencies, exhibited significant oscillations between 2014 and 2022 (Figure 3). These fluctuations were mostly attributed to variations in rice production levels and the diminishing extent of rice fields in both regencies. Rice production in the Pelalawan regency experienced significant fluctuations between 2014 and 2021. These fluctuations were accompanied by a substantial decrease in the rice field area, which declined by almost 67% from 11,126 to 4,979 hectares. In addition, there was a notable reduction in rice production, which decreased from 36,765 to 19,000 m³/ton. However, it is worth noting that in 2021, there is projection of a slight increase in the rice field area, reaching 5,023 hectares. According to the Department of Food Crops and Horticulture of Riau Province (2022), the variability observed in rice production and rice field area within the Pelalawan regency can be attributed to several factors, including the conversion of rice fields to oil palm plantations, crop failure (known as puso), and forest fires. This phenomenon has been particularly prominent over the period spanning from 2015 to 2021. A similar issue was observed in the Kampar regency, where there was significant volatility in rice production between 2014 and 2021. This was accompanied by a substantial decline in rice fields, amounting to nearly 53%, from 6,928 to 2,905 hectares. In addition, there was a corresponding decrease in rice production, with yields dropping from 26,570 to 19,741 m³/ton. However, it is noteworthy that there is a projected increase in rice field area to 3,123 hectares in 2021. According to the statistics provided by the Department of Food Crops and Horticulture of Riau Province (2022), the variations observed in rice production and rice field area in the Pelalawan regency can be attributed to two primary factors: the conversion of rice fields into oil palm plantations and instances of crop failure (puso), particularly during the period spanning from 2015 to 2021.

According to a study conducted by Yasar & Siwar (2016), similar trends were observed in Malaysia, where the amount of rice fields in Peninsular Malaysia, whether categorized by state or granary area, experienced a decline. Based on official records, there has been a significant decline in the extent of rice fields over the course of the past 15 years. Specifically, the area of rice fields has diminished by 88,321 hectares, which accounts for a reduction of 22.17%. This translates to an average annual decrease of 1.49%. In contrast, based on data from the granary regions, there has been a decrease in the size of the rice field by 10,790 hectares, which accounts for a reduction of 5.10% or an annual decline of 0.34%. There exists a notable association between the reduction in the size of rice fields and the overall national rice yield. Meanwhile, it is anticipated that the population will continue to grow, while productivity experiences a gradual expansion. According to the research conducted by Firmansyah et al. (2021), it was observed that the rate of land conversion in the Sidoarjo regency has exhibited a declining trend throughout the years. The study further predicts that the most significant conversion is anticipated to take place between the periods of 2020–2025 and 2025–2030. In the interim, it is projected that the Gresik regency will experience a gradual escalation in the rate of rice field conversion, with the most substantial conversion anticipated to transpire between the years 2035 and 2040. Meanwhile, the city of Surabaya is predicted to experience a loss of rice fields of 40.2 hectares per year due to the development of residential and industrial land. According to the findings of Barchia et al. (2022), there has been a significant decline in the extent of rice fields over the past decade in the Bengkulu province. Specifically, the study reveals a substantial loss of 6,819 hectares, which accounts for almost 74% of the total area. This decline is evident when comparing the rice field extent in 2008, which stood at 9,187 hectares, to the reduced area of 2,308 hectares observed in 2019. The potential decline in rice growing area at the Air Manjuto irrigation region poses a significant risk to agricultural production in Bengkulu.

To mitigate the loss, it is imperative to implement measures that bolster infrastructure facilities and provide incentives, agrochemical subsidies, and agricultural insurances. In addition, it is crucial to refrain from further conversion of rice fields.

According to the WF analysis depicted in Figure 4 for the Pelalawan regency, the rice crop exhibited a maximum WF value of 77,882 m³/ton in 2014, while the minimum WF value occurred in 2016 at 33,348 m³/ton. The decline in WF observed in 2016 can be attributed to a significant decrease in the cultivated area of rice fields compared to the previous year. Specifically, the area of planted rice fields decreased from 8,716 hectares in 2015 to 4,764 hectares in 2016. The occurrence of this problem can be attributed to an extended dry season lasting approximately 8 months, coupled with extensive peatland fires. This is particularly significant as most of the rice fields in the Pelalawan regency are situated on vast expanses of peat. In addition, the conversion of rice fields into oil palm plantations has further exacerbated the issue. It is worth noting that this trend is projected to persist until 2022. In contrast to the occurrences in Kampar regency, rice's greatest WF value in 2017 was recorded at 68,579 m³/ton, while the lowest value was observed in 2022 at 21,681 m³/ton. The decline in water availability in 2022 can be attributed to the prolonged dry season, particularly during the early planting phase. This has resulted in insufficient water supply for rice fields, with approximately 68% of rice fields in Kampar regency relying solely on rainfall. Irrigation is only possible through tertiary canals, which are limited in their water reservoir capacity. Furthermore, there is no provision for water pumping from the Kampar River to support irrigation in several areas, including Kampar, North Kampar, and East Kampar districts. Since 2019, there has been a significant decline in the extent of cultivated rice fields compared to the preceding year. Specifically, the area decreased from 8,147 hectares in 2018 to 3,252 hectares in 2019. This downward trend persisted until 2022, with a further reduction to a mere 31,232 hectares. It is worth noting that there was a temporary increase of 4,976 hectares in 2020, but this was followed by another decline from 2021 to 2022 (Department of Food Crops and Horticulture of Riau Province 2022; Central Statistics Agency of Riau Province 2023). In addition to being attributed to diminished production, the determination of cultivation methods, particularly the selection of seeds, irrigation techniques, and fertilization practices, is the primary factor that impacts the quantification of WF. According to data from the Central Statistics Agency of Riau Province (2023), the annual rice production in Indonesia for the year 2021 amounted to 54.5 million tons. A modest decrease in productivity is observed when comparing the production levels of 2019 and 2020. The potential long-term implications of this situation are a cause for concern, particularly considering the projected deficiency of 90 million tons of rice husk by the year 2050 (Ikhwali et al. 2022). The potential decrease in rice production poses a significant threat to the food security situation in Indonesia. This concern is further exacerbated by the potential risks associated with global climate change, particularly in irrigated regions that heavily rely on the use of agrochemicals (Kusumawardani & Permana 2021).

According to Figure 5, the quantity of blue WF is recorded as 99,050 m³/ton, surpassing the quantities of green WF (57,780 m³/ton) and GWF (17,010 m³/ton). The predominant sources of water utilized for rice production in the Kampar district are groundwater and surface water, as opposed to precipitation. The rice growing system in Kampar and Pelalawan areas necessitates a higher volume of blue water (173,840 m³/ton) compared to green and gray water. Therefore, it is imperative to implement a rice farming approach that utilizes a prevailing irrigation system at the designated research site. According to Kusumawardani & Permana (2021), the agricultural sector in Indonesia predominantly depends on water resources derived from groundwater, surface water, or irrigation systems. Indonesia exhibits a notable feature whereby 75% of its overall surface runoff is accessible during a 6-month period known as the rainy season, while the remaining 25% is available during a corresponding 6-month period referred to as the dry season.

The Kampar district exhibits a greater value of WFblue, measuring 57,960 m³/ton, in comparison to the Pelalawan district, where the value stands at 41,090 m³/ton. The phenomenon can be attributed to the considerable volume of rice production and the substantial WF associated with each kilogram of rice cultivated in the Kampar district. Based on the research conducted by Bulsink et al. (2010), it has been shown that the WF of rice plants is larger than that of other crops. This is mostly attributed to the substantial volume of rice production in Indonesia. According to the research conducted by Ewaid et al. (2021), the utilization of water in the cultivation of rice, particularly in terms of the blue WF, is significantly greater in Iraq, amounting to 3,082.2 m³ per ton, in comparison to the green WF, which stands at 8.8 m³ per ton. The necessity for increased water irrigation arises from the hot and arid climatic conditions that prevail during rice cultivation in Iraq. According to the findings of Lathuillière et al. (2018), the research indicated that agriculture emerged as the primary contributor to the overall blue WF within the basin.

The WF value associated with rice growing in the Kampar regency is 32,190 m³/year, which exceeds the corresponding value of 2,490 m³/year observed in the Pelalawan regency. The green WF in agricultural goods refers to the cumulative amount of rainfall that undergoes evaporation from the soil over the growing season, encompassing plant transpiration and other forms of evaporation (Hoekstra & Chapagain 2008). The findings of Chapagain & Hoekstra (2011) indicate that the fluctuation of the green to blue water ratio exhibits significant temporal and spatial variability. In India, Indonesia, Vietnam, Thailand, Myanmar, and the Philippines, the proportion of green water is significantly more than that of blue water. Conversely, in the United States and Pakistan, the blue WF is four times bigger than the green water component. The observed phenomenon may be attributed to a rise in precipitation intensity, as noted by Krishnamurthy et al. (2009) and Li et al. (2018); this is consistent with the findings that Kampar district has a greater level of rainfall compared to Pelalawan district. To alleviate the strain on the limited global blue water resources, it is imperative to enhance water productivity in both irrigated and rain-fed food production. This can be achieved through the augmentation of yields and the mitigation of non-beneficial evaporation (Hogeboom et al. 2020; Mekonnen & Hoekstra 2020).

In contrast, the GWF has the smallest proportion among the various components of the WF, amounting to 17,010 m³/ton. The results of Bulsink et al. (2010) indicate a decreased GWF in rice growing in Indonesia compared to the blue and green WFs. The GWF value of rice plants in the Kampar district is recorded at 14,520 m³/ton, which surpasses the GWF value seen in the Pelalawan district, measuring at 25,590 m³/ton. The elevated GWF in rice cultivation within the Kampar regency can be attributed to the substantial utilization of pollutants and fertilizers. This phenomenon is closely associated with the comparatively wider expanse of rice agricultural land in the Kampar district as opposed to the Pelalawan district. According to Aryani et al. (2021) and Wu et al. (2021), the surface and ground water resources have been negatively impacted by the excessive application of fertilizers and manure, mostly due to the elevated levels of nitrogen (N) deposition. The mitigation of the nitrogen-associated GWF is of utmost importance, as failure to do so could result in significant water pollution connected to food production and a decline in the capacity of freshwater absorption. Furthermore, the implementation of modifications to irrigation and drainage techniques has the potential to effectively regulate and reduce groundwater withdrawal rates. The risk of pollutant leaching is positively correlated with increasing precipitation levels, a phenomenon that can be alleviated by the implementation of strategies aimed at minimizing drainage during the initial phases of plant development.

Rice holds significant agricultural and dietary importance in the Riau province, serving as a fundamental staple crop. One of the key aspects in endeavors to enhance food production is the adequacy of water supply to cater to the IRs of both irrigated and rain-fed rice fields. Hence, ensuring the provision of adequate water for the irrigation of rice crops is crucial, as it is vital to meet the plants' optimal water requirements. The establishment of a precise water requirement is crucial to facilitate the effective and efficient utilization of water resources. The analysis of water demands encompasses various deciding elements, such as rainfall patterns, cropping patterns, and the timing of plowing and planting activities. The water requirements can be determined by considering the duration of irrigation during the planting phase, the growth time of the plants till harvest, and their impact on achieving optimal production. Through WF analysis, it can serve as an indicator of the impact of water use on agricultural production. Wijayanti et al. (2023) found that areas with a high rate of WF will experience inefficiencies in agricultural practices, leading to a decrease in production yields.

The concept of WFs is important for evaluating appropriate water resource management. Gaining an understanding of the importance of WFs can help us make wise and efficient use of freshwater resources. Due to the link between population growth and climate change, there is an expected increase in the demand for water. This will lead to an increasingly severe water scarcity. The consequences of climate change on water resources can pose significant threats to guaranteeing a continuous water supply for various purposes, particularly agricultural use. Land conversion worsens the problem of water scarcity. The research conducted by Shahid et al. (2018, 2021) showed that changes in land use in the Soan watershed resulted in a significant decrease in runoff in all water catchment areas. The study's most significant finding was the conversion of land for agricultural purposes. Hence, the growth of agricultural land inside the watershed results in the availability of water.

According to the study conducted by Darfia & Rahmalina (2019), droughts in the Kampar watershed occur often and usually last from July to September. A pronounced drought typically transpires over the period spanning from July to August. The future agricultural issue in the Kampar watershed is a direct result of climate change. Climate change is projected to result in higher water consumption, hastened fruit and seed maturation, reduced harvest quality, and decreased yield of food crops (Fahad et al. 2017). Addressing this issue necessitates the adoption of multiple solutions, one of which is the integration of water-saving technologies.

Implementing a variety of water-saving technologies can enhance water efficiency and proactively address water scarcity concerns. Agricultural enterprises have implemented a range of water-saving methods, including the use of intelligent irrigation systems that are integrated with sensors and connected to the Internet of Things (Mallareddy et al. 2023). The implementation of improved irrigation techniques is anticipated to have a significant impact on the agriculture sector of the Kampar watershed. According to previous research conducted by Fereres & García-Vila (2013), irrigated agriculture often produces an output level that is at least twice as high as that of rain-fed agriculture. Kumari et al. (2021) identified many options for reducing water usage in rice fields: (1) intensive land puddling and precise leveling greatly decrease seepage and percolation; (2) applying compost or green manures aids in reducing evaporation, percolation, and seepage; (3) maintaining saturated soil under leveled field conditions can cut evaporation losses by 50%; and (4) implementing rainwater harvesting can significantly decrease surface runoff during the wet season. Furthermore, the adaptation of agriculture to climate change can be accomplished by the implementation of sustainable irrigation techniques (Rosa 2022).

Naazie et al. (2023) discovered multiple strategies in soil and water management with the objective of adjusting crop production to climate change. The methods encompassed in this category involve activities such as land preparation, utilization of organic or compost fertilizers, trimming of crop, crop rotation, and implementation of cover cropping. The utilization of cover cropping has demonstrated efficacy in the preservation of soil fertility, conservation of moisture, mitigation of erosion, and sustenance of microbial activity within the soil (El-Naggar et al. 2021). Moreover, by employing intensification techniques, it is possible to achieve water savings of up to 30% as compared to conventional methods (Liesdiana et al. 2019).

Furthermore, the careful choice of plant species is of utmost importance. The study conducted by Saediman et al. (2021) revealed that rice farmers employ a strategy of selecting distinct plant k varieties based on the specific planting season as a means of adapting to climate change. Farmers in Cialam Jaya, located in South Sulawesi, cultivate high-quality rice varieties such as Mekongga, Ciherang, and Inpari. These cultivars possess natural resistance against pests and diseases. During the second planting season, farmers additionally cultivate the Trisakti variety, which is known for its shorter lifespan and reduced water consumption. Shorter maturation varieties are appropriate for the subsequent planting season to preempt potential water scarcity between September and November. Meanwhile, according to a study by Maity et al. (2023), climate variables may not always directly reduce seed productivity. However, they can alter the biochemical composition of seeds, hence reducing their value for planting.

Based on the research findings, the utilization of blue water for rice cultivation in the Kampar watershed is greater in comparison to other WF components. The increased utilization of water resources from both surface water and groundwater in this agricultural setting highlights the necessity for the implementation of more water-saving irrigation systems, such as furrow irrigation, drip irrigation, and sprinkler irrigation. The purpose of implementing these techniques is to forecast a potential reduction in water availability during the dry season, despite the fact that, according to water balance analysis, the water supply from the Kampar watershed is still sufficient to meet the water needs for rice cultivation in the study area. The WF data obtained from this research can provide further information for the efficient use of water resources, promoting both health and sustainability in the future, particularly in the study area. The WF concept is not the exclusive factor utilized in water management decision-making processes, as it covers multiple components within the sustainability framework for each sector. Nevertheless, its incorporation offers promising opportunities for making substantial contributions. In future research endeavors, our objective is to devise suitable water management strategies in the realm of water resource management to efficiently tackle these estimations.

We acknowledge the DRTPM (Directorate General of Higher Education, Ministry of Education and Culture, Republic of Indonesia), Universitas Islam Riau, and all parties involved in this research.

All relevant data are included in the paper or its Supplementary Information.

The authors declare there is no conflict.