Rivers are natural flowing watercourses which show tremendous variation through time and space, and identified as very important ecosystem of the inland waters group (Hebert and Kundell, 2011). The rivers are vital carriers of water and nutrients. They are critical compo-nents of the hydrologic cycle, provide habitat, nourishments and means of transportation to countless organisms (Johansson et al., 1996; Ling et al., 2012). However, ecological imbalance due to widespread pollution, continuous activities and natural phenomena (Carr and Neary, 2006; Vorosmarty et al., 2010) caused the change of the water quality in rivers.

Water quality affects the productivity, biodiversity and complexity of the aquatic ecosystem (Pejman et al., 2009; Martinez and Galera, 2011). Changes in water quality may lead to degradation of ecosystem services (Dodds and Oakes, 2008) and loss of biological diversity. Water quality is determined by comparing the physical, chemical and biological characteristics of a water sample with water quality guidelines or standards (Carr and Neary, 2006; Pepa et al., 2011; Pathak, 2012; Gamedze et al., 2012). Several important parameters which include temperature, biological oxygen demand, dissolved oxygen, chlorides, pH, phosphorus, nitrate/nitrite/nitrogen and presence of fecal coliform can be used to assess the condition of rivers (Martinez and Galera, 2011; Jayalakshmi et al., 2011; Alam et al., 2007; Ayebo et al., 2006).

Threats to water quality can be both natural and human-related activity sources. Human-related activity sources which are considered the leading cause of water quality problems include agricultural and urban runoff, improper waste disposal and faulty septic systems (Shrestha and Kazama, 2006; Brown and Froemke, 2012; Haileselasie and Teferi, 2012).

Climate change is considered as current and biggest survival issue globally (Alvarez, 2010). According to Palmer (2007), major rivers worldwide will experience dramatic changes in flow due to continous damming and development. Through this changes, serious problems such as floods and droughts are expected to happen. Proactive restoration, rehabilitation and management actions are recommended to enhance the resilience of riverine ecosystems and minimize the impacts of climate change.

In the province of Misamis Occidental, studies in Layawan River of Oroquieta City and Langaran River in Plaridel showed that these rivers are relatively healthy (Palao et al., 2013; Roxas et al., 2005). However, no studies were conducted in Labo and Clarin Rivers although considered to be the most threatened rivers due to land conversion, cultivation and development along some parts of the rivers. Assessing the quality of the rivers is very important considering the fact that these rivers are the sources of water that provide the domestic, commercial and agricultural needs of the many residents of Misamis Occidental. Some portions of the rivers are under continuous tremendous pressure of human-related activities that have altered the physicochemical status and threatened the aquatic organisms affecting the local residents in the area and in the lowlands. This study on the water quality of Labo and Clarin rivers aimed to provide the needed information on water quality based on physicochemical and bacteriological analysis.

Study area

Misamis Occidental is a province located within Region X on the island of Mindanao. It covers 14 municipalites and three cities. It is bounded on the northeast by the Mindanao Sea, east by the Iligan Bay, southeast by the Panguil Bay, and the west by the Zamboanga del Norte and Sur. In this province, there are five major river systems including Labo and Clarin rivers. Labo river is strategically located within geographical coordinates of 123°49'8" to 123° 51' 52" east longitude and 8°10'31" to 8° 11' 32" north latitude. It is a natural boundary between Tangub City and Ozamiz City. Clarin river is located at the southern side of Misamis Occidental and strategically located within geographical coordinates 123° 37’ 30” to 123° 13’ 10” east longitude and 8° 7’30” to 8° 13’10” north latitude. It is the natural boundary between the municipality of Clarin and the city of Ozamiz, Misamis Occidental (Figure 1).

Sampling sites

Field sampling was conducted in Clarin and Labo Rivers in October 2010 and May 2011 to represent the wet and dry seasons, respectively. Three sampling sites were established in each river. Sampling site 1 was the portion of the river located along the forest area. Sampling site 2 was the part of the river along the agroforest area , while the third sampling site was the part of the river along the agricultural area. In each sampling site, three sampling stations were chosen. Each sampling station was further subdivided into three sampling points: right, middle and left portions of the river.

Sample collection

Water samples were collected from each sampling site using cleaned polyethylene bottles for physicochemical analysis and 100 mL sterile bottles for microbial analysis. Each bottle was rinsed with the sample before the final sample collection. All sample bottles were tightly closed, properly labeled and placed in insulated cooler box with ice and immediately brought to the laboratory for analysis. If immediate analysis is not possible, water samples were stored at 4°C until processing and analysis.

Physico-chemical analysis

Physicochemical parameters were determined following the Standard Methods for the Examination of Water and Wastewater American Public Health Association (APHA, 2005). Temperature, pH and dissolved oxygen (DO) were determined in situ. Water temperature was measured using the mercury-in-glass thermometer calibrated from 0-100°C. The pH and dissolved oxygen concentration were determined using the digital pH meter and membrane electrode probe, respectively.

Biological oxygen demand (BOD) was obtained using Winkler’s method. Turbidity was determined with the use of turbidity meter. The total dissolved solids was determined through the gravimetric method. Acidity and alkalinity were measured following the titration method. The total hardness was determined using the EDTA complexometric titration method (APHA, 1998). Nitrate and phosphate levels were gauged through alorimetric procedure (APHA,1998). The river discharge was computed following the simple segment method and the average velocity flow through the single float method.

Bacteriological analysis

For bacteriological analysis, another set of water samples was collected using 100 mL sterile sampling bottles. Water samples were brought to the laboratory for heterotrophic plate counts and coliform test.

Results of the analysis of different physical and chemical parameters of water samples collected from the three diffe-rent sampling areas of Labo and Clarin Rivers are shown in Table 1. Results showed that water temperature varied from 21.0  to  27.0°C with  over-all  mean of 23.78±1.86°C for Labo River and 18.0 to 24.0°C (22.33±1.80°C) for Clarin River. These are within the normal limits for freshwater standards set by the Department of Environment and Natural Resources (DENR). It means that this temperature will not cause stress to aquatic ecosystems since at this temperature range the water still maintains its ability to hold essential dissolved gases like oxygen (Butcher and Covington, 1995; Lawson, 2011). The water temperature of Labo and Clarin rivers are comparable to the Layawan and Langaran rivers (Roxas et al., 2005).

The highest average water temperatures were recorded from water samples along the agroforest area of Labo River and in the agricultural area of Clarin River. This is caused by the exposure of water in these areas to direct sunlight because of the lesser number of trees surrounding the water. The shaded water in forested areas of both rivers is much colder than the exposed water in agricultural areas. Touchart et al. (2012) reported that if water is cold, it holds more oxygen which supports more aquatic organisms. On the other hand, as temperature rises, the rate of photosynthesis by algae and larger aquatic plants increases. The faster the plants grow, the faster the plants die and so the decomposition of bacteria that will consume the oxygen. As a result, increasing photosynthesis decreased level of dissolved oxygen in the water (Maxim et al., 2011; Proppe and Harrel, 2007).

Labo River had relatively high turbidity readings (0.18-0.48 NTU) especially from water samples taken along agricultural areas. The severe soil erosion due to quarrying is the major factor that contributes to the high suspended solids in the water. The suspended matter may include the mud, clay and silt (Jayalakshmi et al., 2011). Water samples taken along the forested area were clear with lower turbidity readings of 0.18 to 0.30 NTU (0.25±0.06 NTU). This area has dense vegetation and rocky substrate. However, when based on Water Resource Commission (2003), turbidity readings are more than the maximum permissible levels for turbidity that vary from 0-10 NTU.

Clarin River had excellent turbidity readings which ranged from 0.07 to 0.13 NTU due to shallow depth, dense vegetation and rocky substrate causing the water to be clear. The dense vege-tation of forest and agroforest beside the Clarin River was observed to have minimized the occurrence of soil erosion.

The total dissolved solid measurements ranged from 27.0 to 71.0 mg/L. Among the sampling areas, the water samples taken along the agricultural area of Labo and Clarin rivers had the highest total dissolved solids with 67.67±3.06 and 59±3.61. mg/L, respectively. Fertilizers from cornfields and organic matter from untreated sewage contribute higher levels of nitrate and phosphate ions that led to elevated total dissolved solid readings (Dodds and Oakes, 2008). However, these levels of dissolved solids are less than the maximum permissible total dissolved solid concentration (500 mg/L) set by the DENR.

The pH ranged from 6.40 to 8.27. The pH values are within the tolerable range of 6.50-8.50 in most stations except sampling stations 2 and 3 in Clarin River. The slightly acidic water of Clarin river along the agroforest and agricultural areas is attri-buted to the decaying plants and logs found at the riverbank. As these logs decompose, organic acids are formed resulting in the decrease of water pH. Aquatic organisms are affected by changeable pH. To maintain a reasonably constant pH in the water, it is good to have a higher alkalinity (Addy et al., 2004).

All sampling stations in Labo and Clarin rivers had higher alkalinity ranging from 61.10-84.55 and 32.60-62.30 mg/L, respectively, in concentration of calcium carbonate. These are classified as not sensitive under the US Environmental Protection Agency cateogory. The higher concentration of calcium carbonate implies that the risk of acidification in the water is lower (Craig, 2009).

All sampling stations in Labo river had total hardness of 58.0-75.0 mg/L and is classified by the Water Quality Association (WQA) as moderately hard. In Clarin river, the sampling stations along the forest and agroforest areas had total hardness readings of 38.0-54.0 mg/L and is classified as slightly hard while the stations along the agricultural area were 63.0-66.0 mg/L (64.33±1.53 mg/L) and classified as moderately hard. The moderate degree of water hardness along the agricultural areas of both rivers pointed to the increased amounts of dissolved calcium and magnesium. The relatively high amounts of calcium in the Labo river especially along the agro forest and agricultural areas was observed to be caused by the presence of limestone. As water moves through soils and rocks, calcium and magnesium ions are dissolved and holds them in solution. Hard water is not a health risk (Skipton and Dvorak, 2009). Calcium is essential to aquatic plants as cell wall component and to aquatic organisms as part of the bones and shells.

The dissolved oxygen readings were 2.40-10.60 mg/L in Labor River and 3.90 - 11.20 mg/L in Clarin River. These are mostly within the DENR standards (≥5 mg/L) except for water along agricultural areas in both rivers. This low level of dissolved oxygen from water along agricultural areas was observed because of the presence of logs and dead plants in the water. Sewage from human settlements nearby and agricultural runoff are additional sources of organic matter (Samantray et al., 2009). Organic materials act as food source for waterborne bacteria. If high levels of organic matter are present in water, there is an increase in number of bacteria (Ling et al., 2012). The bacteria utilize the oxygen in the water as energy to break down long chained organic molecules into simpler, more stable end products during the process of decomposition. This results to the depletion of the dissolved oxygen in the water. Moreover, the amount of oxygen that can be held by the water is dependent on the temperature. In agricultural areas, trees that give shade to the water are limited. As a result, water is exposed directly to the sun-light thus increasing the temperature. Warm water holds less oxygen than cold water (Touchart et al., 2012).

The lowest values of biological oxygen demand (BOD) were recorded in forest sampling stations while the highest values were seen in agricultural areas of both rivers. The higher BOD readings in agricultural areas of Labo River (2.10 - 3.0 mg/L) and Clarin River (1.70 - 2.60 mg/L) can be attributed to the increased organic matter from decayed logs and plants and discharges from agricultural runoff and sewage from the nearby human settlements. With the increase quantity of degradable wastes, there will be an increase in abundance of microorganisms (Martinez and Galera, 2011; Jayalakshmi, 2011). However, both rivers have BOD readings below the standard set by DENR-Environmental Management Bureau.

Nitrate levels were found to be 0.13 to 0.90 mg/L NO₃^-N which are within the DENR standard of 1.0 mg/L NO₃^-N; however, water samples taken from portions of the two rivers along agricultural areas had relatively high nitrate levels. The use of fertilizers and manures on agricultural lands and domestic sewage increases the amount of nitrates drained into the rivers (Quan and Yan, 2002; Ayebo et al., 2006; Chimwanza et al., 2006). Also, at the time of sampling, domesticated animals such as hogs, cows and horses were found at the vicinity of the river. During rains, water moves as runoff across the surface of the soil and carries the untreated sewage which is a significant source of nitrates (Asriningtyas and Rahayuningsih, 2012). The agricultural area of Clarin River had average phosphate concentration beyond the DENR standard of 0.10 mg/L PO₄^-P. An increased level of phosphate is due to the presence of people washing clothes and taking a bath during the sampling. Detergent wrappers were found in the vicinity. Detergent contributes to the increase of phosphate in domestic wastes (Cojocariu et al., 2011; Ling et al., 2012). In addition, varying amounts of phosphates are washed from fertilizers used in cornfields and contribute to the high phosphate level (Olajire and Imeokparia, 2001; Quan and Yan, 2002).

The higher river discharges were monitored at the sampling stations along the forest area of both rivers. Labo River had 16.59 - 21.11 m3/s (18.31 ± 2.44 m³/s) while Clarin River had 6.54 - 9.58 m³/s (7.76±1.46 m³/s). Along the forest area is the rolling slope of hillsides that creates waterways allowing rainwater to reach river faster, thus increasing the discharge. On the other hand, the very steep slope along the agricultural area of Labo River especially in station 1 caused the rainwater to run straight over the surface before infiltration.

The average water velocity was also higher in the forest areas of both rivers with an overall mean of 4.17±0.15 m/s for Labo River and 3.30 ± 0.06 m/s for Clarin River. The forest area is the nearest part where the river starts. On this part, more elevation changes, lesser volume and narrower waterways cause water to move down faster thus higher water velocity.  Results of microbial analysis from the water samples collected in three different sampling areas of Labo and Clarin Rivers are shown in Table 2.

Based on the results, water from Clarin River along the forested area is classified as Class A- public water supply with low coliform counts ranging from 2 to 23. This water is not safe for drinking even if the water seems to be very clear unless a complete treatment will be done such as coagulation, sedimentation, filtration and disinfection (DENR-DAO 34, 2005). The water for drinking should be free of coliforms and contain not more than 10 organisms per milliliter of water. The presence of E. coli in water samples is attributed to the direct discharge of faecal wastes of wild pigs, monkeys, birds and humans (Usharani et al., 2010; Kumar and Puri, 2012).

On the other hand, the water from Labo River along the forested area is classified only as Class B-recreational water class 1 which indicates that the water is good only for recreational purposes such as bathing, swimming, skin diving and other activities for tourism purposes. The presence of few households scattered in hilly and mountainous areas contribute to the microbial count in this portion of the river (Dragun et al., 2011; Britz et al., 2013).

There were very high counts (≥1600) of total fecal coliforms that were present (Escherichia coli and Enterobacter aerogenes) in Labo and Clarin Rivers along the agroforest and agricultural areas. The water in these areas are classified as Class C/D water which means that the water cannot be used for drinking and is only fit for agriculture, irrigation and industrial purposes. A person swimming in such waters has a greater chance of getting sick from swallowing disease causing organisms, or from pathogens entering the body through cuts in the skin, the nose, mouth, or the ears. Diseases and illness can be contracted in waters with high fecal coliform counts. There were more households confined near the riverbanks. It was observed during the sampling that lavatories are absent in the households. Aside from corn and other short-term crop farming, many people practice open hog-raising (not contained in a concrete pens) as their common alternative livelihood. During the sampling, cows and carabaos were found along the riverbanks. The fecal contamination is primarily due to eroded wastes from humans, pigs, carabaos and cows (Sh AlOtaibi, 2009; Adetunde et al., 2011). 

Most of the physicochemical properties of Labo and Clarin rivers were within the tolerable range and are not harmful to the aquatic resources. However, water from both rivers are not safe for drinking due to the presence of coliforms.

The author(s) have not declared any conflict of interests.

We acknowledge the Commission on Higher Education and Misamis University for the funding support.