Identifying potential concerns on surface water resources usage through citizen scientific field investigation in the Province of Antique, Philippines

The Philippines is a country with abundant surface and groundwater resources under tropical and monsoonal climates. However, the freshwater availability per capita remains low due to institutional and management issues (Lapong & Fujihara, 2008). Flooding causes rainwater to flow out as surface water during the rainy season; on the other hand, a water shortage crisis occurs during the dry season (Yazawa & Honda, 2021). Water pollution is also a concern in many of the major river basins due to agricultural pesticides (Ligaray et al., 2017), landfill leachate (Chounlamany et al., 2019), urbanization (Kumar et al., 2018), and so on. Therefore, integrated water resources management has been urgently prioritized, particularly in such urbanized areas as Metro Manila (Yazawa & Honda, 2021) and popular tourist destinations including Palawan (Cacal et al., 2023), by securing the water storage, treatment, and supply facilities.

Nevertheless, provinces in the Philippines remain highly dependent on groundwater for day-to-day water resources (Inson et al., 2021). In rural areas, which still lack water treatment and supply systems, people continue to draw water from a community well. As areas become more developed and urbanized, water demand and consumption increase (UNEP, 2003). Then, the degradation of water, particularly by nitrates, pesticides, and health-related microorganisms, is caused by increased human activities (Bouman et al., 2002; John & Rose, 2005). The Province of Antique, which is the target area of this research, is no exception. The population in Antique has been increasing in recent years, according to a census conducted by the Philippine Statistics Authority (2021). Thus, the increase in groundwater demand, which triggers groundwater contamination, is a matter of growing concern to local government, according to a face-to-face interview conducted by the authors in October 2023. Exploring new water resources from surface water in the province, such as rivers and lakes, is therefore the next challenge.

However, the situation of surface water systems in the Province of Antique has not yet been comprehensively investigated because of the lack of observation facilities. Individual river investigation, particularly for large rivers such as the Sibalom River, located near the Southern capital (i.e. San Jose de Buenavista), has been conducted by the local cooperative. Given that the population is increasing in the middle part of the province, including Bugasong, which is far from the capital, a comprehensive investigation of major river conditions in the province is needed in order to explore the possibility of surface water usage in the near future.

This research conducted the first comprehensive water quality assessment of nine major river systems in Antique. The field investigation and water samplings were conducted with the participation of local citizens and government officers. Physical and chemical water quality parameters were measured and analyzed using only on-site equipment and a smartphone. Recently, the use of smartphones in assisting with field observations has been gaining attention because of their portability and technological advancements in the quality of cameras and sensors (Leeuw & Boss, 2018; Luetzenburg et al., 2021; Tavani et al., 2022). The novelty of this research lies in its analysis of 12 water quality parameters using only an iPhone in combination with an on-site water quality meter additionally measuring four parameters. The citizen scientific water resources investigation allowed for the identification of qualitative local issues that are sometimes overlooked by examining only quantitative water quality values. The success of water quality analysis without the need for expensive facilities demonstrated the high applicability of the methodology in developing areas. Furthermore, the potential issues and insights provided by this research can provide valuable assistance with the comprehensive planning of water resources management in the province.

A series of field investigations was conducted from October 17 to 24, 2023. Nine rivers – Malandog, Sibalom, Patnongon, Cangaranan, Paliwan, Cairawan, Tibiao, Bugang, and Inyawan – were subject to the field investigation. Table 1 presents the key information on the rivers, i.e. the length of mainstream (km), basin area (km²), basin population, based on the LandScan Global 2022 (Sims et al., 2023), and the sampling date and location at each river. The sampling dates depended on the availability of local government officers since the water sampling activities were under their observation.

The Inyawan and Bugang Rivers are situated in the north of the province. The sampling points along these rivers were mainly surrounded by forests, agricultural areas, and livestock farming zones. The Tibiao River is a popular water activity spot in Antique. In this research, the water samples were collected near the upstream mountain resorts since the condition of water resources is a primary concern for the local government in maintaining tourism. Embankment and sand mining activities were observed at the sampling points along the Cairawan, Paliwan, Cangaranan, and Patnongon Rivers. The Malandog and Sibalom Rivers, located near the capital in the south, also exhibit a range of activities including agriculture, livestock farming, and fishing, which are recognized as the primary industries of the local people and were observed around the sampling points.

The field investigation involved the assessment of fundamental water quality parameters, with on-site and laboratory testing. Table 2 summarizes the water quality parameters measured in this research and the detection range of each application/equipment. Turbidity and suspended particulate matter (SPM) concentration were measured via the HydroColor application using the iPhone 12 Pro Max (Leeuw & Boss, 2018). The HydroColor app calculates the remote sensing reflectance based on three images, capturing a gray reflector card (18% exposure), water surface, and sky using the smartphone's camera. The remote sensing reflectance is used to estimate the concentration of absorbing and scattering substances (i.e. SPM) in the water, using turbidity as a proxy. On-site measurements included water temperature, pH, electrical conductivity (EC), and total dissolved solids (TDS) concentration, using the pH/EC meter (EA776AE-3A, Hanna Instruments, USA).

In addition to the water quality parameters measured at the sampling point, water samples were collected using polypropylene bottles and promptly transported to a local laboratory. The measurement of ammonium-nitrogen (NH₄-N), nitrite-nitrogen (NO₂-N), nitrate-nitrogen (NO₃-N), orthophosphate as phosphorus (PO₄-P), chemical oxygen demand (COD), and biochemical oxygen demand (BOD) was facilitated by the SMART PACKTEST application (Kyoritsu Chemical-Check Lab., Japan), using the iPhone 12 Pro Max. The PACKTEST contains a reagent to measure specified analytes in a polyethylene tube. The water samples are colored in a tube after a certain reaction time designated for each water quality parameter. Conventionally, the colored sample in a tube is visually compared with the Standard Color sheet by an analyst to obtain the approximate value/concentration of a water quality parameter. By using the SMART PACKTEST application, this visual estimation can be digitized by taking photographs of colored samples to remove individual variations stemming from different analysts.

Crucially, all of the field investigations conducted as part of this research were the result of a collaborative effort with local citizens and government officers. Two to six officers from the provincial government, depending on the sampling dates and locations, participated in this series of water samplings. Thus, the sampling activities were under their approval and observation. At each river, municipal government officers and/or local volunteer civil engineers also participated as the representatives of local citizens so that they would be able to transfer the knowledge to the other citizens in the future.

The primary concerns of locals regarding water resources were discussed during the water sampling, measurement, and observation at each sampling point of the rivers. A conversational approach was used to directly gather information from local citizens, including the history of each river, ongoing projects, and management activities. Subsequently, citizens learned the meaning of basic water quality parameters, their impact on the river environment, and how to take field notes. This understanding was crucial for citizens to identify potential pollution sources and express expectations regarding water resources management from their unique perspectives. The citizen scientific approach not only enriched the water quality data but also provided insights into local concerns regarding water resources. Discussions during the field investigation allowed for the identification of qualitative local issues that are sometimes overlooked when taking only quantitative measurements of water quality.

Table 3 displays the results of the water quality assessment for the target rivers in Antique, Philippines. Turbidity and SPM were not estimated in the Bugang River because the sampling point was covered by a forest, and the sky image was not available. The estimation range of the HydroColor for both turbidity (NTU) and SPM (mg/L) is 0–80 (Ouma et al., 2018). In the Cairawan, Sibalom, and Malandog Rivers, turbidity and SPM were higher than the estimation range. Thus, the results show 80 ± 29 NTU for turbidity and 80 ± 30 mg/L for SPM. Among the remaining five rivers, the Cangaranan River displayed the lowest turbidity at 11 ± 4 NTU, while the Patnongon River recorded the highest turbidity at 33 ± 12 NTU. These values categorize the rivers as being fairly turbid or rather turbid, according to the turbidity levels presented by Azis et al. (2015).

The pH values of all rivers meet the standard range (i.e. 6.5–8.5) designated by the Water Quality Guidelines and General Effluent Standards of 2016, Philippines (Department of Environment & Natural Resources, 2016). On the other hand, the temperature values in some rivers are slightly outside of the guideline range (Class C, 25–31°C for use in fishery, recreation, agriculture, etc.). There are no standard values for EC and TDS in the Water Quality Guidelines. However, the Philippine National Standards for Drinking Water of 2017 (Department of Health, 2017) notes that the maximum allowable level of TDS is 600 mg/L. Since EC and TDS are correlated parameters, in this case, the TDS concentration values in all rivers, excluding the Malandog River, are within the acceptable range. The sampling point at the Malandog River is at the estuary with high salinity. Thus, the values of EC and TDS exceed the detection limit of the pH/EC meter.

The measurement results of NH₄-N, NO₂-N, NO₃-N, and PO₄-P in Table 3 show that most of these parameters are below the detection range in the target rivers. The detected value of NH₄-N in the Patnongon River is 0.21, which is still lower than the Water Quality Guidelines for Ammonia, i.e. 0.5 mg/L. In the Malandog River, where the sampling point is at the estuary, the values of NH₄-N, NO₂-N, and NO₃-N are within the detection range. The standard for NO₃-N is 7 mg/L, and no standard is available for NO₂-N. Thus, at least NH₄-N and NO₃-N meet the standards.

In six rivers, excepting the Bugang, Cairawan, and Cangaranan Rivers, both COD and BOD are detected. Particularly, the Water Quality Guidelines contains detailed standards for BOD, such as 7 mg/L for Class C, 5 mg/L for Class B, and 3 mg/L for Class A water bodies. According to these standards, the Sibalom and Malandog Rivers, which have the first and second highest populations, respectively (as indicated in Table 2), may contain higher levels of organic pollutants than the other rivers.

In summary, the water quality assessment of nine major rivers reveals that some of the rivers in Antique are already affected by siltation with high turbidity. Anthropogenic activities, such as embankment, sand mining, and dredging, could lead to the further siltation of these rivers. On the other hand, these activities have high importance for disaster management and represent major industries in the province. Thus, a well-integrated management strategy, involving cooperation between stakeholders and locals and including monitoring and education, is necessary for sustainable river management, rather than halting the activities. In basins with high populations, such as the Sibalom and Malandog River Basins, a high BOD level was confirmed by the water quality analysis using an iPhone. Although this research took samples only at one point of each river, there is a possibility that the rivers have already been polluted. However, a shift from groundwater to surface water usage, with the construction of a facility treating physical and chemical parameters, is recommended for these areas since high consumption of groundwater has already affected the lives of people as some wells have dried up or been polluted in the province. Biological parameters were not the focus of this research because of the facility's limitations. Therefore, it is recommended that future research investigate biological parameters, such as E. coli, in order to strengthen discussions of the possibility of surface and groundwater usage.

To engage more local people in effective citizen scientific investigation, all investigation processes should be designed to enable them to work independently in the future, without researchers. Therefore, local citizens should also be involved in water quality analysis and management. As the observed changes in the participants, for example, one engineer prepared and brought his field notes by himself for the second sampling date based on what he learned on the first day. This showed how the citizen scientific approach worked for capacity development and raising awareness. As individuals with knowledge of the local environment, they would be able to take necessary actions for water resources management. In this context, the methodology used in this research could serve as the foundation for citizen-led water resources management.

This research successfully conducted a comprehensive water quality assessment of nine major river systems in the Province of Antique, Philippines, employing a citizen scientific field investigation and water quality analysis using only an iPhone and an on-site water quality meter. Potential issues regarding water resources management in the province were discussed with local governors and citizens while conducting the water sampling and on-site measurement. The results of water quality assessments revealed that some of the rivers, particularly the Cairawan, Sibalom, and Malandog Rivers, have experienced siltation with high turbidity, caused by anthropogenic activities such as embankment, sand mining, and dredging. In highly populated basins, such as the Sibalom and Malandog Rivers, a high BOD level (>7 mg/L) was confirmed by the water quality analysis using an iPhone.

Considering the increase in water demand, there is a need for a shift from groundwater to surface water usage through the construction of a facility to treat physical and chemical parameters. The citizen scientific water resources investigation approach employed in this research enabled the identification of local issues that could not otherwise be found in measuring water quality values. Thus, further research, including the investigation of biological parameters, is necessary to facilitate an in-depth discussion for planning integrated water resources management strategies for the province.

This research was supported by the year 2023 special fund of the Institute of Industrial Science, The University of Tokyo. We would like to thank the Provincial Council and the Sangguniang Panlalawigan office of Antique for their support to conduct the field research.

All authors contributed to the conception and design of this research. Taishi Yazawa was in charge of conceptualization, methodology, formal analysis, writing original draft, project administration, and funding acquisition. Kenn Joshua Geroy Rubite and Princess Eden Macabata-Rubite contributed to data collection, investigation, and writing – review & editing.

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

The authors declare there is no conflict.