Water Quality of the Jerteh River Basin, Terengganu, Malaysia During the Northeast Monsoon

Human activities that cause land use changes are factors affecting the river’s water quality. This study was centred on assessing the quality of the water in the Jerteh River basin that was affected by the land use changes. The water samples were collected at five monitoring stations along the Jerteh River. The fieldwork was conducted between November 2017 and February 2018. The water samples were analysed in the laboratory for six water quality parameters: Biochemical Oxygen Demand (BOD), Chemical Oxygen Demand (COD), Total Suspended Solid (TSS), Ammoniacal Nitrogen (NH3-N), Alkalinity Index (pH) and Dissolved Oxygen (DO). The results showed that the water quality index forthe Jerteh River was classified as moderately polluted (Class II). Three parameters, namely COD, TSS, and NH3-N, were in Classes III and IV during the study period. This study concludes that land use changes due to human activities have impacted the water quality of the Jerteh River basin during the Northeast Monsoon season. Therefore, mitigation and drastic measures should significantly improve the Jerteh River basin’s water quality. All relevant parties should have worked collectively to improve the water quality of the Jerteh River rather than leaving it to the authorities.


Introduction
Studies on water quality, particularly in river basins, have always piqued the interest of hydrologists. The study on the water quality of river basins is critical because its resources provide the lion's share of the water required for human survival. Apart from serving as a source of domestic water, it is essential for industrial operations and agricultural irrigation [1] [2] [3].Thus, authorities should prioritise integrated drainage basin management to ensure that water resources are properly maintained and available for use continuously.
The process of development and land use change is one factor that contributes to the deterioration of water quality in a drainage basin [4] [5] [6] [7] [8].As a result of increased human activity, the river has become a garbage dump, which could degrade the quality and quantity of the river. Recently, the number of river basins supplying water for domestic use has been discovered to be decreasing. Malaysia's current situation indicates that some rivers are still moderately polluted or polluted, with 205 rivers (30%) being moderately polluted and 59 rivers (9%) being polluted [9]. As a result, it is not surprising that water resources have been elevated to a high priority in achieving the Sustainable Development Goals (SDGs), precisely goal number 6 on Clean Water and Sanitation.
The river is supplied with water by a drainage basin, an open system constantly threatened by ineffective management. The Jerteh River basin is no exception; as one of the significant sub-basins of the Besut River, it is constantly threatened by a variety of human activities that have a detrimental effect on the quantity and quality of the Jerteh River's water. The Jerteh Riveris undeniably an essential source of domestic water for the residents of the Besut district. The purpose of this article

Sampling activities and analyses
Between November 2017 and February 2018, water samples were collected four times at five designated stations along the Jerteh River. This observationcould correspond to the current situation, i.e. the wet season.Essentially,rivers' water sampling methods in this fieldwere guided by the American Public Health Association's (APHA) [11]. The following six water quality parameters were used: dissolved oxygen (DO), biochemical oxygen demand (BOD), chemical oxygen demand (COD), ammoniacal nitrogen(NH3-N), total suspended solids (TSS), and pH. Water samples were collected and analysed at the Physical Geography Laboratory, Department of Geography and Environment, Faculty of Human Sciences in the Sultan Idris Education University.
Six water quality parameters were used in the analysis, as the Malaysian Department of Environment (DOE) used only these parameters to determine the state of a river's water quality, referred to as the DOE Water Quality Index Classification (DOE WQIC). The DOE WQCI categorises water quality into five categories and determines the water's current state, as shown in Table 1. Table 1 indicates the range of subindex values (SI) for each water quality index (WQI) parameter. This WQIwas calculated using the formula developed by Malaysia's DOE: To facilitate the calculation of WQI, the SI value from the River Water Quality Index Calculator was converted using a dedicated website.WQI classifications are as follows: Very Good (Class I), Good (Class II), Moderately Polluted (Class III), Polluted (Class IV), and Heavily Polluted (Class V). This water classification could be used to ascertain the purposes of water resources for various human activities, as shown in Table 2.Simultaneously, Malaysia's DOE established the WQI for a body of water, specifically a river, and classified it as Clean(81-100%), Slightly Polluted (60-80%), and Polluted (0-59%). All data on water quality parameters were analysed using descriptive statistics to explain each parameter's value, specifically the minimum, maximum, and average values. Each parameter data is then presented in tables and graphs to explain and show whether it exceeds or does not exceed the established standard.

Results and Discussions
The study's findings and discussion in this section lead to an assessment of the Jerteh River's water quality based on the six parameters established and the Water Quality Index's status. Furthermore, the discussion on water quality parameters referred to Class III, which uses the river as a source of drinking water that requires the least amount of intensive treatment. The highest, lowest, and average values of each Jerteh River's water quality parameter are shown for each of the five monitoring stations. Table 3 shows the concentrations of six water quality parameters observed in the study area during the wet season.

Dissolved Oxygen (DO)
The DO value is a critical parameter in determining a river's water quality. An increased DO value in water indicates that the water is of good quality and suitable for aquatic life. DOE [9]established a water quality standard of 3-5 mg/l for the DO parameter in Class III. The highest DO reading was 7.78 mg/l (ClassI) at Station A in November 2017, while the lowest DO value was 6.30 mg/l (Class II) at Station B in January 2018.The average DO value in November 2017 across all observation stations was 7.5 mg/l (Class I), the highest DO reading ever recorded. Meanwhile, the lowest average DO value recorded in January 2018 was 6.67 mg/l (Class II).Overall, changes in land use in the study area had a minor effect on DO readings. A total DO amount in water that meets DOE standards allows aquatic flora and fauna to survive in Class III. Thus, with proper treatment, this water source is suitable for drinking and recreational purposes [12].

Chemical Oxygen Demand (COD)
The COD value represents the amount of oxygen required to oxidise organic and inorganic chemicals found in bodies of water [13].A higher COD value indicates that the water's quality has deteriorated. In December 2017, the maximum value recorded at Station C was58 mg/l (Class IV), while the minimum value recorded at Station E was23 mg/l (Class II). Meanwhile, the average COD value by month showed a maximum of49.8 mg/l (Class III)in December 2017 and a minimum of28.2 mg/l (Class III) in January 2018. The average COD reading for the five stations during the study period was 35.3 mg/l, indicating that the water quality was Class III. This finding showed that the Jerteh River's water quality was moderately polluted. This finding also revealed that changes in land use in the Jerteh River basin increased pollutants and effluent emissions, resulting in higher COD readings. Industry, housing, construction, and agriculture were all identified as land use activities in the vicinity of the river basin, contributing to the increase in COD amounts at the five observation stations. The BOD parameter assesses the toxicity of industrial and household wastes by calculating the amount of oxygen required for the oxidation process [13].A higher BOD reading indicates that the water's quality has deteriorated. The minimum BOD value was 0.52 mg/l (Class I) at Station E in January 2018, while the maximum value was 2.32 mg/l (Class II)at Station A in December 2017. Meanwhile, the minimum average BOD value was 0.94 mg/l (Class I) in January 2018,and the maximum value was 1.8 mg/l (Class II) in December 2017. Overall, the Jerteh River's BOD value during the study period was 1.3 mg/l (Class II). The water quality of the Jerteh River was classified as moderately polluted based on the average BOD reading. If the BOD level is high, so is the amount of pollution in the water, and vice versa. However, changes in land use in the vicinity of the Jerteh River did not significantly impact this BOD parameter.

pH
The pH of a body of water, such as a river, lake, or pond determines its acidity and alkalinity. The pH value of a river's water indicates its quality and is related to aquatic life. DOE [9] specifies that the pH for river water in Class III must be between 5.0 and 6.0. The minimum pH value was 5.90 (Class III) at Station Bin November 2017, while the maximum value was 6.40 (Class II) at Station A in December 2017. The average minimum pH value was 6.07 (Class II) in November 2017, and the average maximum pH value was 6.28 (Class II) in January 2018. Overall, the pH value in the Jerteh River was 6.2 (Class II)throughout the study period, indicating that land use change activities in the river had impacted its pH value.

Ammoniacal Nitrogen (NH3-N)
The NH3-N parameter is used as a primary indicator of contamination caused by human, animal, and urban domestic waste, as well as industrial and agricultural fertiliser waste. A higher NH3-N value indicates contamination in the presence of extremely high levels of organic matter. DOE [9]set a range of 0.3-0.9 mg/l forthe NH3-N value in ClassIII. A reading of more than 0.9 mg/l indicates that the river has been polluted. The maximum value was 0.56 mg/l (Class III) at Station A in February 2018, while the minimum value was 0.04 mg/l (Class I) at Station E. The average NH3-N value with the lowest value of0.12 mg/l (Class II) was recorded in January 2018, while the highest value was 0.35 mg/l (Class III) in February 2018. Overall, the NH3-N value was 0.25 mg/l (Class II) in the Jerteh River basin. This finding revealed an increase in the NH3-N value in the river basin in February 2018. The changes in land use in the study area, such as residential development, resulted in sewage waste being discharged directly into the river. Moreover, active agricultural activities, specifically paddy cultivation, were carried out in February 2018. Paddy ploughing activity has been held responsible for the rise in NH3-N readings. Furthermore, observations in the study area revealed that many farmers use pesticides and chemical fertilisers on their rice crops. This activity occurred near the Jerteh River basin's upstream area. Thus, this flowing water carried these materials into the Jerteh River, indirectly increasing its NH3-N level.

Total Suspended Solids (TSS)
TSS in water bodies is typically caused by sewage sludge, soil erosion, sand dredging, and natural waste [13]. The higher the TSS value, the poorer the water quality. The maximum TSS value was 170.3 mg/l (Class IV) at Station Ain December 2017, while the minimum value was 131mg/l (Class III)at Station E (November 2017). The highest average TSS was 161.02 mg/l (Class IV) in December 2017, while the lowest was 144.72 mg/l (Class III) in November 2017. Overall, the TSS reading in the Jerteh River was 150 mg/l (Class IV), indicating that it was polluted. The finding showed that TSS readings at the five stations increased from November 2017 to January 2018, then slightly decreased in February 2018. It occurred due to increased land use, particularly in the river's upstream and middle reaches. Land use changes in the area have included building construction, housing, and Another factor, such as riverbank erosion, influenced the amount of TSS in the Jerteh River. Based on observations made in the study area, the river's current was discovered to be high or fast. It resulted in erosion and transport of particles, silt, and pollutants along the river's course.

Status and Water Quality Index of the Jerteh River
The Jerteh River's water quality status was determined using six major water quality parameters previously discussed. Therefore, Formula 1 was used to evaluate the river's water quality status. Also, the WQI at each station was determined based on DOE [9]as the range index for the following statuses: Clean(81-100), Slightly Polluted (60-80), and Polluted (0-59). Water quality analysis conducted throughout the study revealed that the Jerteh River was moderately polluted and classified as a Class II (Table 3). During the study period, the highest WQI recorded was 85, which was classified as Class II with a Clean status at Stations D and E in January 2018. While the lowest WQI readings were recorded in December 2017 at Stations A, B, and C, classified as Class II and Slightly Polluted. Overall, December 2017 had the lowest average WQI value of 77.8 (Class II) with a Slightly Polluted status, and January 2018 had the highest average WQI value of 82.6 (Class II) with a Slightly Polluted status. With an WQI value of 80.1 (Class II), it can be concluded that the Jerteh River's water quality was Slightly Polluted during the study period. However, the Class II designation indicates that the water in the Jerteh River can still be used as a source of drinking water and requires conventional treatment. It is also suitable for sensitive species fishing and recreational activities involving body contact.
There is no doubt that land use development in the Besut district in general, specifically in the Jerteh River basin, has impacted the Jerteh River's water quality. The deterioration of its water quality has been linked to urbanisation activities, particularly in terms of TSS, COD, andNH3-N parameters.

Conclusions
Changes in land use and development in a drainage basin endanger both the quantity and quality of water, particularly river water. This situation will indirectly impact human well-being in the drainage basin that relies on water for various purposes. In this regard, land use development in the Besut district is proliferating, posing a threat to the Jerteh River's water quality. The Jerteh River's water quality was moderately polluted, with an WQI value of 80, corresponding to a Class II classification. Despite increasing land use changes in this drainage basin, this status and WQIvalue indicate that the Jerteh River is still in good condition and is not heavily polluted. The wet season factor associated with Northeast Monsoon winds also influenced changes in the Jerteh River's water quality, particularly for the TSS, COD, andNH3-N parameters. Simultaneously, this study should be expanded in the future to assess the state of water quality during the Southwest Monsoon'sdry season, which runs from May to September, in order to compare the Jerteh River's water quality status during the wet and dry seasons.